It is easily seem that there has been no large catastropic flood in this area for at least 13,250 years !!

Geologists see indications that the total accumulated displacement from
earthquakes and creep along the San Andres fault is at least 350 miles along the fault since it came into existence. Wallace Creek is an ephemeral stream in central California, the present channel of which displays an offset of 128 m along the San Andreas fault which is easily seen from the air and also further down the fault is also easily seen an ancestral stream bed.
Geological investigations have elucidated the relatively simple evolution of this channel and related landforms and deposits. This history requires that the average rate of slip along the San Andreas fault has been 33.9 ± 2.9 mm/yr for the past 3,700 yr and 35.8 + 5.4/-4.1 mm/yr for the past 13,250 yr. Thus it is easily seem that there has been no large catastropic flood in this area for at least 13,250 years !!

The San Andreas Fault Shows the Age of the Earth !!

The infamous San Andreas fault has left its impression on the earth in California in a
number of ways! Geologists see indications that the total accumulated displacement from
earthquakes and creep is at least 350 miles along the fault since it came into existence.
Studies of a segment of the fault between Tejon Pass and the Salton Sea revealed geologically similar terranes on opposite sides of the fault now separated by 150 miles, and some crustal blocks
may have moved through more than 20 degrees of latitude.


Its feature are readily seen from the air as shown below.
One of its many features is the offsetting of streams that cross it. This offsetting feature
can be used to demonstrate and calculate the rate of comparative movement along the fault and
the age at which these changes occurred !!


a) Holocene activity of the San Andreas fault at Wallace Creek, California
b) An Independent confirmation of the slip rates of Sieh and Jahns
c) Appendix A: Wikipedia article on the San Andreas
d) Appendix B: Calibrating Radiocarbon Dating
e) Appendix C: The Bible Affirms Radiocarbon Dating

Holocene activity of the San Andreas fault
at Wallace Creek, California

KERRY E. SIEH Division of Geological and Planetary Sciences, 170-25 California Institute of Technology, Pasadena, California 91125
RICHARD H. JAHNS* School of Earth Sciences, Stanford University, Stanford, California 94305


Wallace Creek is an ephemeral stream in central California, the present channel of which displays an offset of 128 m along the San Andreas fault . Geological investigations have elucidated the relatively simple evolution of this channel and related landforms and deposits. This history requires that the average rate of slip along the San Andreas fault has been 33.9 ± 2.9 mm/yr for the past 3,700 yr and 35.8 + 5.4/-4.1 mm/yr for the past 13,250 yr. Small gullies near Wallace Creek record evidence for the amount of dextral slip during the past three great earthquakes. Slip during these great earthquakes ranged from ~9.5 to 12.3 m. Using these values and the average rate of slip during the late Holocene , we estimate that the period of dormancy preceding each of the past 3 great earthquakes was between 240 and 450 yr. This is in marked contrast to the shorter intervals (-150 yr) documented at sites 100 to 300 km to the southeast. These lengthy intervals suggest that a major portion of the San Andreas fault represented by the Wallace Creek site will not generate a great earthquake for at least another 100 yr. The slip rate determined at Wallace Creek enables us to argue, however, that rupture of a 90-km-long segment northwest of Wallace Creek, which sustained as much as 3.5 m of slip in 1857, is likely to generate a major earthquake by the turn of the century.
In addition, we note that the long-term rates of slip at Wallace Creek are indistinguishable from maximum fault -slip rates estimated from geodetic data along the creeping segment of the fault farther north. These historical rates of slip along the creeping reach thus do represent the long-term—that is, millennial—average, and no appreciable elastic strain is accumulating there.
Finally, we note that the Wallace Creek slip rate is appreciably lower than the average rate of slip (56 mm/yr) between the Pacific and North American plates determined for the interval of the past 3 m.y. The discrepancy is due principally to slippage along faults other than the San Andreas , but a slightly lower rate of plate motion during the Holocene epoch cannot be ruled out.

[IMAGE]1a Figure 1. a. Wallace Creek (WC) is along the San Andreas fault (SAF) between Los Angeles (LA) and San Francisco (SF), in the Carrizo Plain of Central California. b. This oblique aerial photograph shows the modern channel which has been offset -130m, and an abandoned channel that has been offset -380 m. An older abandoned channel, indicated by white arrow at left, has been offset -475 m. Photograph by R.E. Wallace, 17 Sep. 1974. View is northeastward.

California has experienced many episodes of tectonic activity during the past 200 m.y. During the past 15 m.y. horizontal deformations due to the relative motion of the Pacific and North American plates have been dominant. On land, the major actor in this most recent plate-tectonic drama has been the San Andreas fault , across which -300 km of right-lateral dislocation has accumulated since the middle Miocene (Hill and Dibblee, 1953; Crowell, 1962, 1981; Nilsen and Link, 1975). The San Andreas fault traverses most of coastal California, running close to the populous Los Angeles and San Francisco Bay regions (Fig. la). Its historical record of occasional great earthquakes (Lawson and others, 1908; Agnew and Sieh, 1978) amply demonstrates that it poses a major natural hazard to inhabitants of these regions. The future behavior of the San Andreas fault thus has long been a topic of great interest to Californians. Interpretations of historical, geodetic, and geologic data have yielded estimates of one century to several centuries for the time between great earthquakes along the fault in the San Francisco Bay region (Reid, 1910; Thatcher, 1975). Geologic data indicate that similar recurrence intervals apply in southern California (Sieh, 1978b, and in press). The behavior of the San Andreas fault during the past few thousands of years is one of the best clues to its future behavior. Useful forecasts concerning the likelihood or imminence of a great earthquake along the fault will be much more difficult without greater understanding of its behavior during the past several millennia. In this paper, we present and discuss the geologic history of Wallace Creek, a locality about halfway between San Francisco and Los Angeles that contains much information about the Holocene behavior of the San Andreas fault (Fig. la). For the purpose of determining rates of slip in Holocene time, the channel of Wallace Creek offers excellent possibilities. The channel crosses and is offset along a well-defined, linear trace of the San Andreas fault in the Carrizo Plain of central California (Fig. lb). It is relatively isolated from other large drainages, and, therefore, its history is not complicated by involvement with remnants of other drainages that have been brought into juxtaposition. The simple geometry of Wallace Creek suggests a simple history of development. Arnold and Johnson (1909) inferred 120 m of offset on the San Andreas fault , because the modern channel of the creek runs along the fault for about that distance. Wallace (1968) also inferred a simple history of offset involving incision of a channel into an alluvial plain, offset of -250 m, then channel filling and new incision across the fault . The latest dextral offset of 128 m then accumulated. These interpretations are verified and quantified by us in this paper.

color map legend


Figure 2 is a geologic map of the Wallace Creek area that is based upon surficial mapping and study of sediments encountered in numerous excavations. The map shows four main geologic units: older fan alluvium (uncolored), younger fan alluvium (green), high-channel alluvium (dark orange), and low-channel alluvium (light orange). A mantle of slope wash and local alluvium, which is extensively burrowed by rodents, overlies most of the deposits. This unit has been mapped (brown) only where it is thicker than ~ 1 m and does not cover units and relationships that need to be shown on the map. Geological Society of America Bulletin, v. 95, p. 883-896, 11 figs., 3 tables, August 1984.

Older Fan Alluvium

Underlying all other units exposed at the site, there is a late Pleistocene alluvial fan deposit derived from the Temblor Range to the north east. This deposit here termed the "older fan alluvium," consists of thin sheets, lenses, and stringers of indurate silty clay, pebbly sandy clay, and sandy gravel. Most of the trenches (Fig. 2 and 3) esposed this unit. Southwest of the fault, the older fan alluvium is covered by various deposits, but northeast of the fault, the deformed fan surface is incised.
Charcoal disseminated within the older fan alluvium 4 m below the surface of the fan in trench 5 (Fig. 3), yielded an age of 19,340 ± 1,000 yr B.P. (Table 1). The lack of major unconformities and paleosols in the older fan alluvium below or above this dated horizon implies that all of the exposed 13 m of the unit formed during the late Pleistocene epoch. Evidence discussed below supports a conclusion that the fan surface on the northeast side of the fault had become inactive by about 13,000 yr B.P.

Younger Fan Alluvium

Southwest of the fault (Fig. 2), there is a lobate deposit that we have termed the "younger fan alluvium." This deposit overlies and is less indurated than the older fan alluvium. It is a well-sorted gravelly sand with a distinctive imbrication of pebbles that indicates southwestward current flow. The unit is thickest near trenches 2, 9, and 10 and thins to the northwest, southeast, and southwest. The boundary of this composite alluvial fan is inferred from the topography and the trench exposures. A radiocarbon date from charcoal in the upper centimetre of the older fan alluvium (trench 2) indicates that the younger fan alluvium began to accumulate 13,250 ± 1,650 yr B.P. (Table 1).
Figure 4. Trenches 9 and 10 reveal the various deposits of the abandoned channel B1 and B2 are scarp-derived breccias. C1, C2 and C3 are fluvial sands and gravels. Solid triangles indicate locations of charcoal that yielded date for channel deposits.

High-Channel Alluvium

Nestled within the channel of Wallace Creek above the modern stream bed, there are numerous remnants of an ancient terrace (Fig. 2). This surface is referred to as the "high terrace," and it is underlain by sand and gravel beds characterized by scour-and-fill structures, which we refer to as the "high-channel alluvium" (trench 5 in Fig. 3). The massive and poorly sorted nature of some of these "high-channel" beds indicates that they are debris-flow deposits. Other beds that are well sorted and laminated must have been transported as bedload in the waters of Wallace Creek. Radiocarbon analyses (3) of charcoal from within the high-channel deposits in trench 5 demonstrate that these beds were accumulating through a period from 5845 ± 225 yr B.P. to 3680 ± 155 yr B.P. (samples WC-3, WC-6, and WC-7 in Table 1). Southwest of the San Andreas fault , the highchannel deposits occur in the abandoned channel of Wallace Creek (Figs. 1 and 2). Trenches 2, 7, and 8 (Fig. 3) and 9 and 10 (Fig. 4) show these sands and gravels residing in a 3- to 4-m deep channel cut into colluvium. Like their correlatives northeast of the fault , these beds exhibit major episodes of scour and fill. A radiocarbon analysis of organic matter from trench 10 yielded an age of 3,780 ± 155 yr B.P. This sample was collected from a colluvial wedge in the middle of the deposits in the abandoned channel, and its age indicates that the abandoned-channel deposits are contemporaneous with the highchannel deposits across the fault and upstream. Figure 5 includes a profile of the high terrace. The height of the high terrace above the modern channel is greatest at the fault ; the terrace merges with a low terrace ~1 km upstream from the fault . Judging from the elevation difference of the high terrace across the fault , vertical slip during the past 3,800 yr is 3 m, which is a mere 2.3% of the horizontal slip during that time period. It is worth noting that within 1 km to the northwest and to the southeast, this vertical slip diminishes to zero and reverses sense. 5

Modern-Channel Alluvium

Younger sand and gravel beds very similar to the high-channel alluvium have been deposited in the modern channel of Wallace Creek (Fig. 2, and trench 5 in Fig. 3). Like the high-channel alluvium, this "modern-channel alluvium" also exhibits scour-and-fill structures and interfingers with debris derived from the channel walls. In trench 5, the base of the modern-channel alluvium is —2.5 m beneath the creek bed, and along the entire channel, there is a low terrace that occurs 1.5 m above the modern creek bed (Fig. 5). This terrace represents the highest level reached by the modern-channel deposits; it formed and was incised within the past 1,000 yr, as indicated by the radiocarbon date of 1035 ± 235 yr B.P. on charcoal 2.5 m below the terrace surface in trench 11 (Fig. 6). An early photograph of the channel shows that the low terrace was incised by the creek prior to A.D. 1908 (Sieh, 1977, p. 61).

GEOLOGIC HISTORY The evolution of Wallace Creek has been rather simple. It is divisible into four periods, each of which ends in a sudden change of channel configuration. Accumulation of Older Fan Alluvium and Initial Entrenchment of a Channel Prior to initial incision of Wallace Creek, during the late Pleistocene epoch, the older fan alluvium gradually accumulated as broad, thin bed on an alluvial fan or apron that extended southwestward from the Temblor Range across the San Andreas fault (Fig. 7a). The lack of small channels within the older fan alluvium indicates either that any scarps that formed along the fault during this interval were buried before they accumulated even 1 m of height, or that they faced mountainward and served to pond the older fan alluvium on the upstream side of the fault . About 13,000 yr B.P., the first major entrenchment of the older fan alluvium occurred (Fig. 7b). Several small gullies were eroded into the fault scarp, and their debris, the younger fan alluvium shown in Figure 2, was deposited at the foot of the scarp. At about the same time, the initial entrenchment of Wallace Creek occurred. The downstream segment of this initial channel now lies outside the mapped area, -475 m northwest of Wallace Creek (beneath the white arrow at left margin of Fig. lb).

Initial Offset of Wallace Creek and Re-entrenchment

After -100 m of right-lateral slip had been registered by the features formed -13,000 yr B.P., the initial downstream segment of Wallace Creek was abandoned, and a new segment was cut, so that a straight-channel configuration was restored across the fault (Fig. 7c). This new segment is the one labeled "abandoned channel" in Figure 1.
More Offset and Re-entrenchment of the Channel

For several millennia the newly re-entrenched Wallace Creek served as a narrow conduit for materials being transported fluvially out of the nearby Temblor Range. The depth of initial incision of this channel is poorly constrained, but it cannot have been more than 12 m, which is the depth of the base of the high-channel deposits below the surface of the old alluvium in trench 5. As slip accumulated along the San Andreas fault early during the Holocene epoch, Wallace Creek developed a bend along the fault that reflected the offset accumulated since entrenchment (Fig. 7d). Water and debris flowing within the channel were diverted to the right at the fault , flowed along the fault for a distance equal to the accumulated offset, and then were diverted left and away from the fault . These two bends in the channel will be referred to here in after as the right bend and the left bend. Trench 5 indicates that by -6000 yr B.P., 3.0 to 3.3 m of sediment had been deposited within the channel at the right bend. Trench 5 also shows that, locally, at least 1.5 and perhaps 3.3 m of these high-channel deposits subsequently was eroded away. About 3800 yr B.P., after the channel had been offset -240 m, critical changes began to occur within the channel. For reasons that we do not understand, debris began to accumulate in the channel to greater thicknesses than ever before (Fig. 7e). Trench 5 reveals that at the right bend, the accumulation was at least 5.5 m deep. Trenches 2, 9, and 10 show that this accumulation all but filled the channel at the right bend. This filling set the stage for abandonment of the channel downstream from the right bend and re-entrenchment of Wallace Creek straight across the fault (Fig. 7e). The new channel was cut no more than 8.5 m below the level of the old channel, as the maximum depth of the new channel is only 8.5 m below the top of the high terrace in trench 5.

Offset and Future Re-entrenchment of the New Channel

The new channel has been offset —130 m subsequent to its creation about 3800 yr B.P. (Fig. 7f). The modern-channel deposits lave accumulated in the new channel during this period of time. They are now —2.5 m thick at :he right bend and more than 2.5 m thick at the left bend. Although the active channel floor is now —3 m below the crest of the channel bank at the


Figure S. Stream profiles of the modern and the abandoned channels of Wallace Creek. High terrace, indicated by dotted lines, and top of high-channel alluvium, indicated by solid and dashed lines, are offset ~3 m vertically. Figure 6. Trench 11 exposes the upper 2.5 m of low-channel deposits in the modern channel. Solid lines are contacts of individual fluvial beds. Dotted lines represent locally visible layering within these beds. right bend, older modern-channel deposits form a low terrace surface that is only 1 m below the crest of the bank there. Mr. Ray Cavanaugh, who farms at Wallace Creek, reported to us that water actually spilled over the edge at the right bend in the winter of 1971-1972 or 1972-1973. It is not hard to envision a third entrenchment of Wallace Creek (Fig. 7g), given another metre or two of channel filling and a moderately high discharge. Such a re-entrenchment would establish the creek once again straight across the fault .

Figure 7. The Holocene -late Pleistocene evolution of Wallace Creek. An aggrading "older alluvial fan" during the period including 19,300 yr ago progressively buried small scarps formed along the San Andreas fault (SAF) during major strike-slip events (a). Right-lateral offsets accumulated during this period, but no geomorphologically recognizable offsets began to form until 13,250 yr ago, when the "older alluvial fan" became inactivated by initial entrenchment of Wallace Creek (b). At this time, erosion of small gullies to the right (southeast) of Wallace Creek also resulted in deposition of the "younger fan alluvium" downstream from the fault . These features then began to record right-lateral offset, and scarps began to grow along the fault . About 10,000 yr ago, a new channel was cut across the fault at Wallace Creek, and the initial channel, downstream from the fault , was abandoned (c). The new channel remained the active channel of Wallace Creek during the early and middle Holocene , during which -250 m of slip accumulated (d). This channel filled with "high- channel alluvium" 3,700 yr ago, and Wallace Creek cut a new channel straight across the fault (e). Between 3,700 yr ago and the present, this youngest channel has registered 128 m of right-lateral offset (f). Aggradation of this channel, accompanied by continued offset, will probably lead to its abandonment and the creation of a new channel, cut straight across the fault (g).


Slip Rate during the Late Holocene

Knowing the date of the most recent entrenchment of Wallace Creek and the offset that has accumulated since that entrenchment, one can calculate rather precisely the rate of slip for the San Andreas fault . That rate is 33.9 ± 2.9 mm/yr, and its derivation is explained in detail below. The offset of the modern channel of Wallace Creek is 128 ± 1 m. This figure is obtained by extrapolating the southwestern edge of the abandoned channel (labeled 1 in Fig. 8) to its intersection with the fault and then measuring the distance from that intersection to the intersection of the modern channel edge (labeled 2 in Fig. 8) with the fault . The same value is obtained if one measures the distance between the offset segments of the modern channel (labeled 3 and 4 in Fig. 8). In making the latter measurement of offset, it is important to realize that the outside edge of the left bend has been eroded by flood waters that have swept against it as they have passed around the left bend. The right bend has not been eroded in this manner, because it is refreshened each time the fault slips. The fact that feature 1 and feature 3 (Fig. 8) intersect the fault at almost the same point strongly suggests that the abandonment of the high channel and entrenchment of the modern channel were contemporaneous. This coincidence also indicates that the new channel was cut straight across the fault without any initial nontectonic deflection of the stream along a fault scarp. The absence of any initial, nontectonic deflection is also confirmed by the fact that the modern channel is entrenched thrcugh a broad topographic high immediately downstream from the fault (consider contours in Fig. 2). If the channel had been deflected E.long a fault scarp, one would expect it to have cut through a low point on the downstream side of the fault rather than a high point. The measured separation of 128 m thus is ascribable entirely to tectonic offset. The youngest date from the deposits of the abandoned high channel (3680 ± 155 y r B.P.) provides a maximum age for the modern channel, because all of the high-channel sediments were deposited before the modern channel was cut. All offset of the modern channel thus oc- curred between this date and A.D. 1857. The average slip rate, therefore, can be no slower than 35.7 + 1.9 mm/yr [128 ± 1 m/3.680 ± 155-93 yr]. (93 yr is the time between A.D. 1950, which has been designated zero B.?., and A.D. 1857.) Additional considerations are necessary to provide an upper limit to the slip rate. For this constraint, trenches 9 and 10 (Fig. 4) are useful. The high-channel deposits here consist of three distinct units, labeled CI, C2, and C3, that represent three distinct scourings and fillings. The uppermost sediment of channel C2 in treich 10 contained the radiocarbon sample the age of which is 3780 ± 155 yr B.P. At the time of deposition, CI, C2, and C3 in trenches 9 and 10 must have been at or northwest of the right bend of Wallace Creek. Trench 9 is now .45 m northwest of the right bend, and so no more than 145 m of dextral slip has accumulated since channel C2 was filled 3780 ± 155 yr B.P. The trend of C2 between trenches 10 and 9 suggests that the edge of C2 actually intersects
the fault at least 10 m closer to the modern right bend. In support of this, we note that the channel is -5 m wide and rests entirely southwest of the fault in both trench 9 and trench 10. Sufficient channel width to accommodate a similar deposit southwest of the fault in the modern channel does not exist until at least 15 m downstream from the modern right bend. There, the crest of the channel bank is ~5 m southwest of the fault trace, and, were the channel to fill this year, a 5-m wide deposit analagous to the channel fill in trenches 9 and 10 would be deposited. From trench 9 to this geometrically analagous point in the modern channel (labeled 2 in Fig. 8) is -130 m. It seems, therefore, that no more than 130 m of dextral slip accumulated between 3780 ± 155 yr B.P. and A.D. 1857. This yields an upper limit of 35.3 ± 1.5 mm/yr [130 m/(3,780 ± 155 - 93 yr)] for the slip rate. This maximum limiting rate is indistinguishable from the minimum limiting rate of 35.7 + 1.9 mm/yr determined previously and independently. The rate must therefore be 35.3 ± 1.5 mm/yr, which includes the highest maximum value (35.3 + 1.5 mm/yr) and the lowest minimum value (35.7 - 1.9 mm/yr). The calculations thus far have assumed continuous fault displacement between 3680 yr B.P. and A.D. 1857. It is very likely, however, that much, and possibly all, of the slip accumulates sporadically, during large earthquakes, such as that which occurred in 1857. If, as we argue below, this segment of the fault is characterized by coseismic displacements of ~10 m, followed by several centuries of quiet repose, the fault could have been at any point in its earthquake cycle 3680 yr B.P. If, in that year, the region bisected by the fault was in the middle or toward the end of a period of elastic strain accumulation, the rate calculated using this data will be slightly too high, because the 128-m offset accumulated between then and 1857 is in small part due to loading that occurred slightly earlier. Put in a different way, the 3,680-yr date may be any fraction of a recurrence interval younger than the beginning of a strain accumulation cycle. The beginning of the loading cycle corresponding to the earliest increment of the 128-m offset thus may be any time between 3680 yr B.P. and 3680 plus one recurrence interval. As is seen below, the average recurrence interval here is -310 yr, or 8% of the time between A.D. 1857 and 3680 yr B.P. The actual slip rate thus could be as much as 8% lower than that just calculated, or 32.5 ± 1.5 mm/yr. The late Holocene slip rate thus could be any value between 32.5 ± 1.5 and 35.3 ± 1.5 mm/yr. This range is conveniently expressed as 33.9 + 2.9 mm/yr.

Slip Rate since 13,250 yr B.P.

An additional determination of slip rate along the San Andreas fault at Wallace Creek comes from the 475-m offset of a 13,250-yr-old alluvial fan from its source gullies. This provides an average slip rate of 35.8 + 5.4/-4.1 mm/yr, which is not appreciably different from the late Holocene rate of 33.9 ± 2.9 mm/yr. The 13,250-yr-old alluvial fan constitutes the "younger fan alluvium" mapped in Figure 2. The fan radiated from a point that is now located very near the modern left bend of Wallace Creek. Its existence is reflected in the bulging of the 2,240-, 2,250-, and 2,260-ft contours toward the southwest (Fig. 2). Even though it is now buried by 1.5 to 2 m of unmapped slope wash and bioturbated materials, the bulging of the contours and measurements of thickness in trenches 2, 3,4, and 6 enable construction of the isopach map of the younger fan alluvium shown in Figure 9. 9 Trench 2 (Fig. 3) exposes the sediments of the fan near its apex. There, the sediments constitute a 1.3-m-thick bed of well-sorted, imbricated sandy gravel. The gravel is composed of tabular pebbles of diatomaceous Tertiary marine mudstone. Imbrication of these tabular pebbles clearly indicates a flow direction toward the southwest. The source of the alluvial fan thus must be on the opposite side of the San Andreas fault . Although the fan is composed of three discrete beds in trench 2 (see detailed log of trenches, available from author), the lack of bioturbation or weathering of the two horizons between these beds suggests that the fan was deposited very rapidly, perhaps in a matter of a few decades or less. The deposit overlies a massive, poorly sorted sandy loam that represents either a colluvial unit or an alluvial deposit that was extensively bioturbated prior to burial. The unit probably lay at the ground surface for a long time prior to burial by the alluvial fan. The presence of charcoal pebbles and granules in this unit, no more than a centimetre or two beneath the base of the fan, suggests that a range fire occurred just prior to deposition of the fan. The charcoal certainly would have been oxidized if it had not been buried deeply very soon after its formation. Erosion of the fan materials from their source within the burned area may have been a direct result of the fire, which removed protective vegetative cover from the ground surface. The charcoal age of 13,250 ± 1,650 yr B.P. thus represents the age of the basal unit of the overlying alluvial fan. If the source of the younger fan sediments were Wallace Creek, the fan would be offset a mere 128 m. This would imply that the fault was inactive between about 13,000 yr and about 3700 yr B.P., because we have just shown that 128 m of slip has occurred since about 3700 yr B.P. Such a long period of dormancy along the San Andreas fault seems very unlikely to us, and so we seek a source for the younger fan that is farther to the southeast. The volume of the fan is -25,000 m3. Candidates for the source gully (or gullies) must have total eroded volumes at least as great as this and preferably somewhat larger, because some of the material transported out of the source region must have been carried beyond the alluvial fan as suspended load and bedload. Given this constraint, only two plausible sources for the fan exist within 1 km of Wallace Creek. The first is a solitary channel -730 m southeast of the fan apex (E in Fig. 1). This channel originates in the Temblor Range but drains a much smaller area than Wallace Creek. If this is the source, an average slip rate of -63 mm/yr for the period 13,250 to 3700 yr B.P. is calculated:

This would indicate fluctuations in slip rate of at least several centimetres per year during the past 13,000 yr, because the average rate for the past 3,800 yr has been -34 mm/yr. More likely sources for the alluvial fan are four closely spaced gullies several hundred metres southeast of the fan apex (A, B, C, and D in Fig. 1 ). In Figure 9, these have been restored to their probable location at the time of formation of the fan. None of these four small gullies, which extend only a few hundred metres back from the fault scarp, could have been the sole provider of enough material to construct the entire fan. The volumes of A, B, and C are only -13,000 m3 each, and D is much smaller. In any combination, however, they could have delivered enough material. The proper matching of this multiple source with the younger fan deposit can be determined rather precisely. If the general reconstruction shown in Figure 9 is correct, the southeastern Figure 9. Isopach map of 13,250-yr-old alluvial fan and source gullies B and C. In this figure, the gullies have been restored 475 m to their late Pleistocene position upstream from the fan. The same gullies are indicated by letters B and C in Figure lb. For reference, dotted line represents location of modern channel of Wallace Creek. Isopach map is based on trench exposures (thick, open bars) and geometry of contours. Insert in upper right illustrates use of topographic contours in constructing isopach map. Lower edge of stippled region is topographic contour. Upper edge is contour prior to deposition of fan. Southwestward bulging of contours indicates presence and thickness of alluvial fan. flank of the main fan complex had to be southeast of channel C. The offset thus is no less than 472 m. At the same time, the crests of the two distinct lobes of the fan shown in Figure 9 should have had their apexes at the mouths of two of the middle gullies. Only gullies B and C are spaced appropriately to meet this constraint. The mouth of gully B cannot be offset more than 478 m, if B is the source of the northwestern lobe of the fan. It is of interest that the younger fan deposits are offset from gullies A, B, C, and D, only slightly less so than the oldest, beheaded channel of Wallace Creek itself (marked with a white arrow at the left margin of Fig. 1). The creation of gullies A, B, C, and D must, therefore, be nearly contemporaneous with the fnst entrenchment of Wallace Creek. These considerations constrain the offset of the younger fan deposits to 475 ± 3 m. In that the younger fan formed 13,250 ± 1650 yr B.P., the average slip rate must be 35.8 + 5.4/-4.1 mm/yr. Within the level of resolution, this cannot be distinguished from the average late Holo- cene rate of 33.9 ± 2.9 mm/yr.


The average Holocene and late Holocene rates of slip at Wallace Creek are important new measurements of strain across the San Awireas
table 2
fault in central California, because they are the first to span more than a fraction of a great earthquake cycle of strain accumulation and relief. These millennial averages can be used in conjunction with other data to infer earthquake recurrence intervals. For example, the length of the cycle of strain accumulation that preceded and led to the great 1857 earthquake can be calculated. In 1857, the San Andreas fault sustained 9.5 m of right-lateral slip at Wallace Creek. This is indicated by five small offset gullies nearby (A, B, C, D, and E in Fig. 1; Table 2), as well as by small offset gullies at distances of as much as several kilometres to the northwest and southeast. These gullies were incised across the fault prior to the 1857 event, but after the previous large event (see Sieh, 1978c, for a more detailed discussion). If one assumes that the 9.5 m of fault slip associated with the 1857 earthquake relieved elastic strains that had accumulated in the adjacent crustal blocks at an average rate of 34 mm/yr, one calculates that the 1857 earthquake was preceded by a 280-yr period of strain accumulation. This calculation does not assume that annual strain accumulation was uniform during the 280-yr period, but only that the average annual rate was equal to the millennial average of 34 mm/yr. Periods of faster or slower accumulation thus could be accommodated within the over-all loading cycle. Table 2 (top of col. 5) displays the actual range of values for the period of strain accumulation if the uncertainties in the 1857 offset value and average slip rate are taken into account. In lieu of a direct dating of the large event that preceded the 1857 event at Wallace Creek, this range (240-320 yr) is probably the best estimate that can be made for the recurrence interval between the 1857 earthquake and its predecessor. Estimates of the duration of two earlier periods of strain accumulation can also be made, using the average late Holocene slip rate and the '1857(240 to 320 yr). t|857 (560 to 740 yr). §1857-(840toll40yr). amount of fault slip associated with each of the last two prehistoric earthquakes. Table 2 lists the data that suggest these 2 events were associated with -12.3 and 11.5 m of fault slip at Wallace Creek. At 34 mm/yr, these values would have accumulated in 360 and 340 yr, respectively. The actual range in value for both of these recurrence intervals, calculated using the ranges in value for the slip rate and the offsets, is displayed in column 5 of Table 2. From the table, one can see that the latest 3 recurrence intervals are estimated to be within the range of 240 to 450 yr. Of course, it is possible that the 4,000-yr and 13,000-yr average slip rates do not represent the average rate of strain accumulation during the periods of fault dormancy prior to 1857 and the 2 previous great earthquakes. For example, the rate of accumulation actually could have been much higher during the past millennium and much slower during the previous 4,000-yr interval. If so, the recurrence intervals between the latest few earthquakes would be much shorter than those calculated above. Perhaps a future study of a currently undiscovered 1,000-yr-old feature near Wallace Creek will resolve this issue by providing a 1,000-yr average rate. Alternatively, the past several earthquakes may be dated directly, as has been done at Pallett Creek (Sieh, 1978b, in press). In the meantime, the validity of using the 3,700-yr average slip rate in calculating recurrence intervals of recent and future great earthquakes must be assessed in other ways. First, the slip rate averaged over the past 3,700 yr (33.9 ± 2.9 mm/yr) does not differ appreciably from the 13,000-yr average (35.8 + 5.4/-4.1 mm/yr), although the 13,000-yr average conceivably could be as much as 10 mm/yr (-30%) faster than the late Holocene average, given the imprecision of the 2 determinations. Second, geodetic data on modern rates of strain accumulation across the fault are available from the "Carrizo" net, which spans the fault and 80 km of adjacent territory at the latitude of Wallace Creek (Savage, 1983, and 1982, written commun.). These data are available, however, only for the period 1977.6 to 1981.5. The deformation observed during this period aver- ages 0.29 ± 0.06 /ustrain/yr (extension) N89° ± 4°W and -0.09 ± 0.06 justrain/yr (contraction) north-south. Numerous models of lithospheric deformation can produce this observed surficial deformation. One class of model involves the assumption that the observed deformations are the result of aseismic right-lateral slip on the San Andreas fault beneath its locked, brittle upper 10 or 20 km. In this case, the observed deformations of the Carrizo net are resolved as right-lateral shear strains parallel to the San Andreas fault . The average shear strain over the entire 80-km-wide network is 0.38 ± 0.04 /żrad/yr. This translates into a deep slip rate on the fault of 30.4 ± 3.2 mm/yr, if one assumes that the network spans the entire zone of deformation due to slip on the fault . If it does not span the entire zone, the rate of deep slip on the fault must be higher. Like the 13,000-yr average rate, the geodetically determined modern rate does not differ significantly from the 3,700-yr average. The similarity of the 13,000-yr, 3,700-yr, and 4-yr averages suggests that strain accumulation across the fault may be fairly uniform. Of course, numerous histories could be invented that include these three data points and yet involve large fluctuations in the strain accumula- tion rate between earthquake cycles or recurrence intervals. To date, however, no known data support large fluctuations. A reasonable as- sumption, thus, is that the late Holocene average slip rate represents the average rate of strain accumulation between large earthquakes. The recurrence intervals displayed in Table 2 may, therefore, be realistic estimates of the dormant intervals that preceded the past three great earthquakes. In the next section, we attempt to assess when the current earthquake cycle will end at Wallace Creek; that is, when the next great earthquake, accompanied by rupture at Wallace Creek, will occur. We also attempt to use the 3,700-yr average slip rate to assess the likelihood of large earthquakes elsewhere along the San Andreas fault .


Along the South-Central (1857) Segment If the crust adjacent to the San Andreas fault has been accumulating strain at 34 mm/yr since 1857, as much as 4.3 m of potential slip has now been stored and conceivably could be released along all or part of the 1857 rupture. Geomorphologie data, however, suggest that this is likely only along two portions of the 1857 rupture. Wallace Creek is not within either of these portions. Figure 10 displays offsets measured along the south-central segment of the San Andreas fault . The 1857 segment is divisible into at least three parts, based on slippage during the 1857 earthquake and one to four previous large earth- quakes. The southeastern part is ~90 km long and seems to have been characterized by 3- to 4.5-m slip events. The central 160 km, including Wallace Creek, has experienced 7 to 12.3 m of slip during the most recent 3 great earthquakes. The lower values along this central portion occur along the reach between km 90 and km 200, where several other active faults to the north and northeast exist, and so the lower values may reflect distributed deformation, away from the San Andreas fault . A 30-km segment northwest of Wallace Creek experienced 3 to 4 m of slip in 1857 and probably 1 or 2 during previous large earthquakes, as well. These data suggest that each part of the fault has experienced a characteristic amount of slip- Figure 10. Right-lateral offsets measured along the south-central (1857) segment of the San Andreas fault suggest that slip at each locality is characterized by a particular value. Solid circles are data from Sieh (1978c), with poor-quality data deleted. Open circles are data from Davis (1983). Triangles are new data and remeasurements at sites reported by Sieh (1978c). Open squares are new data. Vertical bars indicate magnitude of imprecision in measurement. page during the past three to four large earthquakes. Although, of course, so few data do not provide a statistically sound basis for predicting all previous and future events, we are confident that this pattern offers seme insight into the long-term behavior of the fault . At least two explanations are worth considering. First, we consider the possibility that the northwestern 40 km and southeastern 90 km are loaded more slowly, and, therefore, when the earthquake occurs, they experience lesser amounts of slip than does the central 160-km- long part. This is unlikely, because the average Holocene slip rate along these two parts nust be nearly equal to the rate determined at Wallace Creek. Just beyond the south-central segment, at Cajon Creek (Fig. 10), the San Andreas las average Holocene and late Holocene slip rates of 25 ± 3 mm/yr (Weldon e.nd Sieh, 1981). The nearby San Jacinto and related subparallel faults probably carry ~10 mm/yr at this latitude (based on data of Sharp, 1981, and Metzger, 1982). These fault systems end and nearly merge with the San Andreas fault just northwest of Cajon Creek. Farther northwest, the San Andreas fault is the only major active structure, and so northwest of Cajon Creek, it must have a slip rate of —35 mm/yr. In addition, the average recurrence interval for large earthquakes at Pallett Creek (location in Fig. 10) is in the range of 145 to 200 yr, which is appreciably shorter than the 240- to 450-yr range at Wallace Creek. For this reason, some of the slip events shown in Figure 10 in the Palmdale-Pallett Creek region must have their northwestern rupture tip southeast of Wallace Creek, and 1857-like events cannot be the only type of slip event along this part of the south-central segment. 10 The northwestern 30 km of the south-central segment (Fig. 10) must also share the long-term average slip rate of Wallace Creek. No diversion of a large fraction of the Wallace Creek rate along other structures is plausible. The only known major active(?) fault nearby is the San Juan Hill fault , which runs 3 to 14 km west of and subparallel to the San Andreas from about Cholame to Wallace Creek (Jennings and others, 1975). Its rate of slip is probably no more than a few millimetres per year. A second explanation fcr the different behavior of the three parts of the south-central segment is based on the hypothesis that each part is imbued with a different strength. If, for reasons of geometry or rock properties, the cent'al 160 km of the segment were 2 or 3 times stronger than the 2 other parts, 2 or 3 times a;, much elastic loading of the adjacent crustal blocks would be necessary before failure occurred. Each failure thus would result in two to three times as much slippage as on the two adjacent parts. Such an explanation is compatible with our judgments that (1) slip rate does not vary greatly along the south-central segment, and (2) large earthquakes are more frequent at Pallett Creek than at Wallace Creek. Table 3 lists our best estimates of the dates of large earthquakes at Wallace Creek and proposed correlations with large earthquakes that have been directly dated at Pallett Creek (Sieh, in press) and at Mill Potrero (Davis, 1983). The capital letters in Figure 10 reflect our best judgment regarding correlation of the latest events at Wallace Creek, Pallett Creek, and Mill Potrero. Event X at Pallett Creek (A.D. 1720 ± 50) has no correlative at Wallace Creek, although Davis (1983) discovered evidence for and dated a relatively small slip event at Mill Potrero that may well be event X. Event V at Pallett Creek occurred about A.D. 1550, which is about the time we estimate that the last prehistoric event at Wallace Creek occurred, and also about the time of a large slip event that Davis (1983) discovered at Mill Potrero. Similarly, events R and F at Pallett Creek occurred at about the time we estimate that the third and fourth events occurred at Wallace Creek. On the basis of the foregoing discussion, we judge that the central 160 km of the southcentral segment of the San Andreas fault is un- likely to generate a great earthquake for at least another 100 yr. Recurrence intervals appear to be in the range of 250 to 450 yr, and yet the time elapsed since the great earthquake of 1857 is only 127 yr. Slip during the latest 3 great earthquakes has been 7 to 12.3 m, and yet we suspect that only a little more than 4 m of potential slip has been stored in the past 127 yr. The southeastern 90 km and the northwestern 30 km of the south-central segment are good candidates for producing a large earthquake within the next several decades. Geomorpho- logie measurements seem to indicate that 3 to 4.5 m of slip is characteristic during large events, and >4 m of potential slip may well have been stored in the adjacent crustal blocks since 1857. Based on studies at Pallett Creek, the probability of a great event along the southeastern 90 km of the south-central segment within the next 50 yr is between 26% and 98% (Sieh, in press).

Along the Creeping Segment

The long-term average slip rates determined at Wallace Creek are indistinguishable from the geodetically determined rates of slip at deep levels along the fault from Wallace Creek to Monterey Bay (Savage, 1983; Lisowski and Prescott, 1981). The long-term rates at Wallace Creek are also identical to the historical rate of slip at shallow levels along the central 50 km of the creep- ing segment (see data compiled by Lisowski and Prescott, 1981, Fig. 6). These similarities could be coincidental, but they suggest that the central 50 km of the creeping segment is creeping annually at its millennial-average rate of slip. If this were true, it would mean that large elastic strains are not accumulating across the central 50 km of the creeping segment, and that this segment will not participate in the generation of the next large earthquakes along the San Andreas fault . From a geological point of view, it is reasonable to suspect that the long-term slip rate along the San Andreas fault at Wallace Creek should not be different from its long-term rate along the creeping segment, except along its northernmost 50 km, adjacent to which runs the actively creeping Paicines fault (Harsh and Pavoni, 1978). No other large, active structures in the latitudes of the creeping segment can be called upon to absorb a large portion of the slip rate observed farther south at Wallace Creek. Likewise, there are no obvious geological structures near the San Andreas that would lead one to suspect that the long-term slip rate along the creeping segment is appreciably higher than the long-term rate farther south.

Along the 90-km Segment
Centered on Cholame

between the central 50 km of the creeping zone and Wallace Creek, there is a stretch of the San Andreas fault that historically has been a zone of transition between the fully creeping and fully locked portions of the fault. On the basis of available data, this segment is a prime candidate for generating a large earthquake in the near future. In the period of historical record, it has not experienced as much slip as have segments to the northwest or southeast, and it is therefore a "slip gap." One interpretation of the historical data is illustrated in Figure 11, in which cumulative right-lateral slip for the past two centuries is plotted as a function of location along the fault. We assume that creep rates northwest of Cholame have been constant for the past few hundred years, so that the alignment array data for the period 1968-1979 are representative of the pre- and post-1857 creep rates. We also assume that Cholame has been the edge of the creep zone throughout this period. In the century preceding 1857, 3 to 3.5 m of slip would have accumulated by creep northwest of Slack Canyon. Less slip would have accumulated by creep, and perhaps during occasional moderate earthquakes, between Slack Canyon and Cholame. In 1857, —3.5 m of slip occurred along the 30-km stretch of the fault southeast of Cholame, and 9.5 m of slip occurred in the vicinity of Wallace Creek. The sparse historical accounts are compatible with our inference in Figure 11 that slippage during the earthquake decreased northwestward from Cholame and died out near Slack Canyon (Sieh, 1978c, p. 1423-1424). Following 1857, creep resumed northwest of Cholame. Northwest of Slack Canyon, —4.5 m of slip now has accumulated at the full, longterm rate of loading of the fault (that is, 34 mm/yr). The 60-km-long section between Slack Canyon and Cholame, however, has crept at rates that are significantly lower than the loading rate, and strain is being stored in the rocks adjacent to the fault there. Similarly, elastic strains are accumulating in the rocks adjacent to the locked portion of the fault, and the northernmost 30 km of this portion, which seems to fail in 3- to 4-m slip events, may well be loaded nearly to the point of failure. We suggest that this northernmost part of the locked segment and the southernmost part of the creeping segment might fail in unison and produce a major earthquake. This hypothetical event would be associated with —90 km of surface rupture and a maximum of-4.3 m of right- lateral slip. In discussing this hypothetical event, it is important to note that the great 1857 earthquake seems to have originated in this region. Sieh (1978a) documented that at least 2 moderate foreshocks occurred in this vicinity about 1.5 and 2.5 hr prior to the main shock. Within the past century, 5 moderate (M5.5 to 6) earthquakes have been produced by slippage along the San Andreas fault northwest of Cholame. Sieh (1978a) inferred that the 1857 foreshocks emanated from a source similar to that which produced these historical shocks. If this is true, then the next moderate "Parkfield-Cholame" earthquake might well be a foreshock of the hypothetical major event described above.


Minster and Jordan (1978) determined from a circumglobal data set that the relative motion of the Pacific and North American plates has averaged ~56 mm/yr during the past 3 m.y. The geological record at Wallace Creek shows that, at least during the past 13,000 yr, only -34 mm/yr of this has been accommodated by slip along the San Andreas fault. If one assumes that the 3-m.y. average represents the Holocene average rate across the plate boundary as well, then clearly the San Andreas fault is accommodating only -60% of the relative plate motion. The remainder of the deformation must be accomplished elsewhere within a broader plate boundary. The San Gregorio-Hosgri fault system, which traverses the coast of central Cali- fornia, may have a late Pleistocene-Holocene slip rate of 6 to 13 mm/yr (Weber and Lajoie, 1977), and the Basin Ranges, to the east of the San Andreas fault, may be opening N35°W on oblique normal faults at a late Pleistocene-Holocene rate of-7 mm/yr (Thompson and Burke, 1973). Most of the 56 mm/yr plate rate thus may be attributed to the San Andreas, San Gregorio-Hosgri, and Basin Range faults. Longterm slip rates on these three major fault systems are not known precisely enough to preclude or confirm the possibility that the rate of relative plate motion during the Holocene is equal to the 3-m.y. average. No clear basis exists, however, for suggesting that the Holocene rate is less than or more than the longer-term rate.


Wallace Creek is named after Robert Wallace, who elucidated the basic history of the channel more than 15 years ago and provided us with a special topographic base map. N. Timothy Hall drew our attention to the study site. He and Laurie Sieh participated in initial studies. Art Fairfall and John Erickson at the University of Washington provided all of the radiocarbon analyses. Robert Wallace, David Schwartz, David Pollard, Christopher Sanders, and Ray Weldon provided helpful criticisms of earlier manuscripts. This work was supported by the National Earthquake Hazards Reduction Program, U.S. Geological Survey Contract nos. 14-08-0001-15225, 16774, 18385, and 19756.


Agnew, D.. and Sieh, K., 1978, A documentary sludy of the fell effects of the great California earthquake of 1857: Seismological Society of America Bulletin, v. 68, p. 1717 1729.
Arnold, R., and Johnson, H. R„ 1909, The earthquake rift in eastirn San Luis Obispo County, California: Science, v. 29, no. 744, p, 558.
Crowell, J„ 1962, Displacement along the San Andreas Fault California: Geological Society of America Spec ial Papers, v, 71, 61 p. 1981, An outline of the tectonic h:slory of southeastern California, in Ernst, W. C. ed.. The geotectonic development of Califcrnia: Engle- wood Cliffs, New Jersey. Prentice-Hall, p. 584 600.
Davis, T.. 1983, Late Cenozoic structure ind tectonic history of the western "Big Bend" of the San Andreas Fau t and adjacent San Em gdio Moun- tains [Ph.D. dissert.]: Santa Barbara, California, University of Califor- nia, Department of Geological Sciences.
Harsh, P., and Pavoni, N., 1978, Slip on the Paicines fault: S:ismological Society of America Bulletin, v. 68, ;3. 1191-1194.
Hill, M., and Dibblee, T., Jr., 1953, San Andreas, Garlock and Biji Pine faults. California—A study of their charac:er, history and tectonic significance of their displacements: Geological Society of America Bulletin, v, 64. p. 443-458.
Jennings, C, and others, 1975, Fault map of California: CaliforniE Division of Mines and Geology California Geological Data Map Serie:. Map no, 1. Klein, J.. Lerman. J. C, Damon, P. E .. and Ralph, E. K... 1982. Calibration of radiocarbon dates: Tables based on the consensus data of th z Workshop Calibrating the Radiocarbon Time Scale: Radiocarton. v. 24, p. 103-150,
Lawson, A., and others, 1908, The Gilifornia earthquake of April 18, 1906—Report of the State Eanhquike Investigation Comnission: Wa- shington, D.C, Carnegie Institution of Washington. 2 columes and atlas, 461 p.
Lisowski, M„ and Prescotl, W. H.. 1981. Short range distance measurements along the San Andreas fault system in central California: Seismological Society of America Bulletin, v. 71, no. 5, p. 1607 1624.
Metzger, L., 1982, Tectonic implications of the Quaternary history of Lower Lytle Creek, southeastern San Gat riel Mountains [B.A. thesis): Clare- mont, California, Pomona College.
Minster, J. B.. and Jordan. T. H., 1978, Present-day plate motion;: Journal of Geophysical Research, v. 83. no. B . 1, p. 5331 5334. Nilsen, T., and Link, M. H., 1975, Stratigraphy, sedimentology ant offset along the San Andreas fault of Eocene to lower Miocene strata of the northern Santa Lucia Range and the San Emigdio Mountains. Coast Ranges, centra] California, i>r Weaver, D. W,, and others, eds., Palcogene Sym- posium and selected technical papers: Conference on Future Energy Horizons of the Pacific Coast, Annual Meeting AAPG-SEPM-SEG, Long Beach, California, p. 367-400.
Reid, H. F., 1910, Permanent displacements of the ground, in Tl e California earthquake of April 18, 1906—Retron of the State Earthq take Investi- gation Committee: Washington, D.C Carnegie Institution of Washing- ton, v. 2, p. 16 28.
Savage, J. C, 1983, Strain accumulation in western United States: Annual Reviews of Earth and Planetary Science, v. 11, p. 11 43. Sharp, R. V., 1981, Variable rates of late Quaternary strike slip on the San Jacinto fault zone, southern California: Journal of Geo jhysical Re- search, v. 86. p. 1754-1762.
Sieh, K., 1977. Late Holocene displacement history along the touth-central reach of the San Andreas Fault [Ph.D. dissert.]: Stanforc, California, Stanford University, 219 p.
1978a. Central California foreshocks of the great 1857 earthquake: Seismological Society of America Eiulletin. v. 68, p. 1731 1749. 1978b, Pre-historie large earthquakes produced by slip on the San Andreas fault at Pallet! Creek, California: Journal of Geophysical Re- search, v. 83, p. 3907 3939.
1978c, Slip along the San Andreas fault associated with th: great 1857 earthquake: Seismological Socie.y of America Bulletin, v. 68, p. 1421 1428, in press. Lateral offsets and revised elates of large prehistoric earthquakes at Pallen Creek, southern California: Journal of Geophysical Research. Stuiver, M., 1982, A high-precision calibration of the AD radiocarbon time scale: Radiocarbon, v. 24. no. I, p. 1 26.
Stuiver, M„ and Polach, H. A.. 1977, Discussion: Reporting of 4C data: Radiocarbon, v. 19. no. 3. p. 355-J.63.
Thatcher. W., 1975, Strain accumulation on the northern San Andreas fault zone since 1906: Journal of Geophysical Research, v. 80, no. 35, p. 4873 4880.
Thompson, G. A., and Burke, D. B„ 1973, Rate and direction of spreading in Dixie Valley, Basin and Range province, Nevada: Geologic al Society of America Bulletin, v. 84, p. 627 632. Wallace, R. E.. 1968, Notes on stream channels offset by the San Andreas fault, southern Coast Ranges, California, in Dickinson, W., anc Grantz, A„ eds.. Conference on Geologic Problems of San Andreas Fault System. Proceedings: Stanford University Publications in the Geological Sciences, v. 11. p. 6-21.
Weber, G. E., and Lajoie, K. R.. 1977. Late Pleistocene and Holoc:ne tectonics of the San Gregorio fault zone between Moss Beach anil Point Ano Nuevo, San Mateo County, California: Geological Society of America Abstracts with Programs, v. 9. no. 4. p. 524. Weldon. R. J., and Sieh, K. E., 1981. Offset rale and possible timing of recent earthquakes on the San Andreas fi.ult in Cajon Pass. California [abs.]: EOS (American Geophysical Union Transactions), v. 62. no. 45, p. 1048.

Manuscript Received by the Society November 10, 1982

Revised Manuscript Received September 2, 1983

Manuscript Accepted September 22, 1983

Contribution No 3819, Division of Geological and Planetar

Sciences. California Institute of Technology

Printed in U.S.A.

An Independent confirmation of the slip rates of Sieh and Jahns

Title: Stream Channel Offset and Preliminary Slip Rate on the San Andreas Fault, at the Van Matre Ranch Site, in the Carrizo Plain, California

Authors: Noriega-Carlos, G. R.; Grant, L. B.; Arrowsmith, R.; Young, J. J.

Affiliation: AA(University of California, Irvine, Environmental Health, Science and Policy, Irvine, CA 92697-7070 United States ;, AB(University of California, Irvine, Environmental Health, Science and Policy, Irvine, CA 92697-7070 United States ;, AC(Arizona State University, Department of Geological Sciences, Tempe, AZ 85287-1404 United States ;, AD(Arizona State University, Department of Geological Sciences, Tempe, AZ 85287-1404 United States ; Publication: American Geophysical Union, Fall Meeting 2004, abstract #G11A-0772

Publication Date: 12/2004

Origin: AGU

AGU Keywords: 7221 Paleoseismology, 7223 Seismic hazard assessment and prediction, 7200 SEISMOLOGY

Bibliographic Code: 2004AGUFM.G11A0772N


To understand the spatial and temporal variation in fault slip it is important to improve the spatial coverage of slip and slip rate measurements along major active faults. A set of well-preserved channels are offset across the San Andreas fault at the Van Matre Ranch (VMR) site (35.154N, 119.700W) in the Elkhorn Hills area of the Carrizo Plain. The fault zone and offset channels at VMR were exposed by excavation in 1993 and 2004. This study included one fault-perpendicular and 5 fault-parallel trenches that exposed the buried thalwegs of several offset channels. Seventeen samples were collected from channel margin deposits for 14C dating and survey data was taken for accurate offset measurement of the buried thalwegs and geomorphic channels. The geomorphic history of the site is well manifested in the excavations with clear evidence for initial incision of the channels into Plio-Pleistocene fan units that were typically heavily bioturbated. The channels then back filled and the stratified channel sediments grade laterally into clayey silts. The buried thalweg of the currently active channel is offset 24.8 m, while the geomorphic offset is 27.6 m (qualitatively defined conservative uncertainties on offsets are ± 1m). The thalweg of the first beheaded channel is offset 48.8 m with a geomorphic offset of 51.8 m. The geomorphic offset of the second beheaded channel ranges from 71.9 to 79.0 m. There are no ages associated with these channels. The median dates of samples from the clayey silts in the currently active channel margin range between A.D. 1221 and 1108, implying a 34.7 mm/yr slip rate. The significance of the samples ages is dependent upon interpretation of the sediments in which they were collected. They were collected from clayey silts which are either colluvium, washed down from adjacent hill slopes, or autochthonous alteration of the channel deposits by pedogenic processes (largely burrowing). If the samples were derived from colluvial processes, the ages of the samples would provide a maximum slip rate. However, if the samples were derived from older channel sediments, then they would indicate a slip rate minimum. This preliminary slip rate is consistent with the measured slip rate at Wallace Creek, approximately 18 km to the northwest where Sieh and Jahns documented a late Holocene slip rate of approx. 33.9 ± 2.9 mm/yr, and with the regionally assumed 35-mm/yr rate derived from decadal time-scale geodetic measurements.

See the following appendices for more information
Appendix A: Wikipedia article on the San Andreas
Appendix B: Calibrating Radiocarbon Dating
Appendix C: The Bible Affirms Radiocarbon Dating

Appendix A
Wikipedia article on the San Andreas

San Andreas Fault

From Wikipedia, the free encyclopedia

Exaggerated altitude image of the San Andreas Fault on the Carrizo Plain in central California, 35°07'N, 119°39'W. The picture is a composite of radar data and a Landsat photo.
Aerial photo of the San Andreas Fault in the Carrizo Plain

The San Andreas Fault is a geologic transform fault that runs a length of roughly 800 miles (1,300 km) through California in the United States. The fault's motion is right-lateral strike-slip (horizontal motion). It forms the tectonic boundary between the Pacific Plate and the North American Plate.

The fault was first identified in Northern California by UC Berkeley geology professor Andrew Lawson in 1895 and named by him after a small lake which lies in a linear valley formed by the fault just south of San Francisco, the Laguna de San Andreas. Following the 1906 San Francisco Earthquake, it was Lawson who also discovered that the San Andreas Fault stretched well southward into Southern California.



[edit] Southern, central, northern segments

The San Andreas Fault can be divided into three segments.

Map of the San Andreas Fault, showing relative motion.

The southern segment (known as the Mojave segment) begins near the Salton Sea at the northern terminus of the East Pacific Rise and runs northward before it begins a slow bend to the west where it meets the San Bernardino Mountains. It runs along the southern base of the San Bernardino Mountains, crosses through the Cajon Pass and continues to run northwest along the northern base of the San Gabriel Mountains. These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range. Near Palmdale, a portion of the fault is easily examined as a roadcut for the Antelope Valley Freeway runs directly through it.

After crossing through Frazier Park, the fault begins to bend northwards. This area is referred to as the “Big Bend” and is thought to be where the fault locks up in Southern California as the plates try to move past each other. This section of the fault has an earthquake-recurrence interval of roughly 140-160 years. Northwest of Frazier Park, the fault runs through the Carrizo Plain, a long, treeless plain within which much of the fault is plainly visible. The Elkhorn Scarp defines the fault trace along much of its length within the plain.

The central segment of the San Andreas fault runs in a northwestern direction from Parkfield to Hollister. While the southern section of the fault and the parts through Parkfield experience earthquakes, the rest of the central section of the fault exhibits a phenomenon called aseismic creep. This term describes the fault being able to move without causing earthquakes.

Map showing the San Andreas (reds and orange) and major "sister" faults in the San Francisco Bay Area

The northern segment of the fault runs from Hollister, through the Santa Cruz Mountains, epicenter of the 1989 Loma Prieta earthquake, then on up the San Francisco Peninsula, where it was first identified by Professor Lawson in 1895, then offshore at Pacifica at Mussel Rock. This is the approximate location of the epicenter of the 1906 San Francisco earthquake. The fault returns onshore at Bolinas Lagoon just north of Stinson Beach in Marin County. It returns underwater through the linear trough of Tomales Bay which separates the Point Reyes Peninsula from the mainland, returning onshore at Fort Ross. (In this region around the San Francisco Bay Area several significant "sister faults" run more-or-less parallel, and each of these can create significantly destructive earthquakes.) From Fort Ross the northern segment continues overland, forming in part a linear valley through which the Gualala River flows. It goes back offshore at Point Arena. After that, it runs underwater along the coast until it nears Cape Mendocino, where it begins to bend to the west, terminating at the Mendocino Triple Junction.

[edit] Plate movement

Historical movement of the San Andreas Fault

All land west of the fault on the Pacific Plate is moving slowly to the northwest while all land east of the fault is moving southwest (relatively southeast as measured at the fault) under the influence of plate tectonics. The rate of slippage averages approximately 33-37 mm/year across California. [1]

The westward component of the motion of the North American Plate creates compressional forces which are expressed as uplift in the Coast Ranges. Likewise, the northwest motion of the Pacific Plate creates significant compressional forces where the North American Plate stands in its way, creating the Transverse Ranges in Southern California, and to a lesser, but still significant, extent the Santa Cruz Mountains, site of the Loma Prieta Earthquake of 1989.

Studies of the relative motions of the Pacific and North American plates have shown that only about 75 percent of the motion can be accounted for in the movements of the San Andreas and its various branch faults. The rest of the motion has been found in an area east of the Sierra Nevada mountains called the Walker Lane or Eastern California Shear Zone. The reason for this is not as yet clear, although several hypotheses have been offered and research is ongoing. One hypothesis which gained some currency following the Landers Earthquake in 1992 is that the plate boundary may be shifting eastward, away from the San Andreas to the Walker Lane.

Assuming the plate boundary does not change as hypothesized, projected motion indicates that the landmass west of the San Andreas Fault, including Los Angeles, will eventually slide past San Francisco, then continue northwestward toward the Aleutian Trench, over a period of perhaps twenty million years. On the other hand, if the plate boundary shifts eastward, then the entire state of California would move in the same direction.

[edit] Scientific research

[edit] Research at Parkfield

In central California is the small town of Parkfield, California, which lies along the San Andreas Fault. Seismologists discovered that this section of the fault consistently produces magnitude 6.0 earthquakes about every 22 years. Following earthquakes in 1857, 1881, 1901, 1922, 1934, and 1966, scientists predicted an earthquake to hit Parkfield in 1993. This quake eventually struck in 2004 (see Parkfield earthquake). Because of this frequent activity and prediction, Parkfield has become one of the most popular spots in the world to try to capture and record large earthquakes.

In 2004, work began just north of Parkfield on the San Andreas Fault Observatory at Depth (SAFOD). The goal of SAFOD is to drill a hole nearly 3 kilometers into the Earth's crust and into the San Andreas Fault. An array of sensors will be installed to capture and record earthquakes that happen near this area.[2]

[edit] The University of California study on "the next big one"

A study completed by Yuri Fialko[3] has demonstrated that the San Andreas fault has been stressed to a level sufficient for the next "big one," as it is commonly called, that is, an earthquake of magnitude 7.0 or greater. The study also concluded that the risk of a large earthquake may be increasing faster than researchers had previously believed. Fialko also emphasized in his study that, while the San Andreas Fault had experienced massive earthquakes in 1857 at its central section and in 1906 at its northern segment (the great San Francisco earthquake), the southern section of the fault has not seen a similar rupture in at least 300 years.

If such an earthquake were to occur, Fialko's study stated, it would result in substantial damage to Palm Springs and a number of other cities in San Bernardino, Riverside and Imperial counties in California, and Mexicali municipality in Baja California. Such an event would be felt throughout much of Southern California, including densely populated areas of metropolitan Los Angeles, Orange County, San Diego and Tijuana, Baja California.

"The information available suggests that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell," Fialko said. "It could be tomorrow or it could be 10 years or more from now," he concluded in September of 2005.

[edit] The Cascadia Connection

Recent studies of past earthquake traces on both the northern San Andreas Fault and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The 1906 San Francisco Earthquake seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake, and the rupture moved mostly from south to north. [4]

[edit] Notable earthquakes

The San Andreas Fault has had some notable earthquakes in historic times:

  • 1857 Fort Tejon earthquake — 350 kilometers were ruptured in central and southern California. Though it is known as the Fort Tejon earthquake, the epicenter is thought to have been located far to the north, just south of Parkfield. Only two deaths were reported. The magnitude was about 8.0
  • 1906 San Francisco Earthquake — 430 kilometers were ruptured in Northern California. The epicenter was near San Francisco. About 3000 people died in the earthquake and subsequent fires. This time the magnitude was estimated to be 7.8.
  • 1989 Loma Prieta earthquake — 40 kilometers were ruptured (although the rupture did not reach the surface) near Santa Cruz, California, causing 63 deaths and moderate damage in certain vulnerable locations in the San Francisco Bay Area. Magnitude this time was about 7.1. The earthquake also postponed game 3 of the 1989 World Series at Candlestick Park.
  • 2004 Parkfield earthquake — on 28 September 2004 at 10:15 AM, a magnitude 6.0 earthquake struck California on the San Andreas Fault. This earthquake was originally expected in 1993 based on the latest earthquake prediction theories of the time, but eleven years passed before the predicted event occurred. Despite the extra time between events, the magnitude of the earthquake was no larger then anything.

Appendix B

Radiocarbon Calibration by Richard G. Fairbanks, Columbia University

The radiocarbon content of the atmosphere and surface ocean depends upon the solar flux, Earth’s geomagnetic field intensity, and the carbon cycle

The records of the 14C content of the atmosphere and oceans contain a remarkable array of information about Earth history. Produced by cosmic rays in the upper atmosphere, 14CO2 rapidly mixes throughout the troposphere and exchanges with the reactive carbon reservoirs of the oceans and biosphere, where it decays. For the past 11,000 years, fluctuations in the atmospheric 14C have been largely produced by changes in the solar magnetic field. Many researchers believe that carbon cycle changes, tied to deep ocean circulation changes are a significant cause of atmospheric 14C fluctuations between 11,000 and 15,000 years before present. On longer time scales, changes in the Earth’s magnetic field intensity impact the 14C content of the atmosphere, producing positive 14C anomalies during intervals of weaker geomagnetic field.

small logo

Of practical importance to a wide range of scientific disciplines is the radiocarbon calibration, which is used for converting radiocarbon ages to calendar years; essential for measuring time and rates of change for numerous scientific fields. To access our radiocarbon calibration program, click on the 'Radiocarbon Calibration Program' button above, or here.

Arguably, few research topics engage so many different fields of science and have such a profound impact on our understanding of Earth and Solar science as the history of 14C in the Earth's atmosphere and the surface and deep oceans. Over the past decade we have witnessed a remarkable development and proliferation of accelerator mass spectrometers; these instruments have reduced the counting time by a factor of 100 and reduced the sample size by a factor of 1000 compared to the classic B-counting systems. It is estimated that nearly 90% of all measurements made at the more than 50 active accelerator mass spectrometry laboratories are radiocarbon dates. This dramatic increase in the number of radiocarbon dates is driving the demand for a radiocarbon calibration program that spans the entire radiocarbon timescale from the present to 55,000 years BP. Extension of the 14C record beyond the 0 to 11,900 year long tree ring record is well underway, being measured in many different archives, and undoubtedly an enormous amount of scientific knowledge will stem from these studies. In our laboratory, we have overlapped and extended the tree-ring radiocarbon calibration from 3,000 to 55,000 yrs. BP using coral samples from our offshore coral reef core collections from Barbados (13.10°N; 59.32°W) in the western tropical Atlantic and Kiritimati Atoll (1.99°N, 157.78°W) in the central equatorial Pacific, and from the uplifted reefs of Araki Island (15.63°S; 166.93°E) in the western Pacific. In addition, we have reanalyzed the radiocarbon and 230Th/234U/238U age dates from our earlier radiocarbon calibration work using new pretreatment and analytical techniques and state-of-the-art instrumentation at higher precision; we report these new results in this WEB site and in Fairbanks et al., (2005).

In our radiocarbon calibration paper (Fairbanks et al., 2005), we present paired 230Th/234U/238U (Lamont) and 14C age determinations (Lawrence Livermore National Lab and Leibniz-Labor for Radiometric Dating and Isotope Research Christian-Albrechts University Kiel) that span the entire range of the radiocarbon dating technique and present a radiocarbon calibration curve based on a Bayesian statistical model with rigorous error estimations. Due to the importance of an accurate and precise radiocarbon calibration curve, we have measured many samples in duplicate and validated the quality of the samples by dating the older samples with redundant 231Pa/235U dates. Our online radiocarbon calibration curve presented in this WEB site is a stand alone alternative to existing radiocarbon calibration curves that infer calendar ages based on interpolations and correlations of local climate proxies in deep-sea cores to the chronology of ice core proxies or assumptions about sedimentation rates. Our calibration has the advantage that each data point in the calibration has a measured calendar age (230Th/234U/238U) and radiocarbon age with know errors that are independent from each other. In a series of published papers and manuscripts soon to be published, we present our analytical techniques in detail (Mortlock et al., 2005; Chiu et al., 2005a) and the geochemical (Cao et al., 2005) and geophysical (Chiu et al., 2005b, 2005c) explanations for the departure of radiocarbon dates from the true calendar ages and compare our results to other radiocarbon calibration data.

calibration curve

Comparisons of Fairbanks Radiocarbon Calibration data and curve and IntCal04 data and curve

The tree ring atmospheric radiocarbon calibration data set spanning 0 to 12,410 years BP is superior to all other atmospheric radiocarbon calibration data due to the number and quality of the radiocarbon measurements and the accuracy and precision of the tree dendrochronology (Stuiver et al., 1998; Reimer et al., 2004). The Fairbanks curve (Fairbanks et al., 2005; 2007) and IntCal04 curve (Reimer et al., 2004) use the same tree ring data set from 0 to 12,410 cal yr B.P. and the two different radiocarbon calibration programs yield nearly identical results over this interval (See CalPal web site for a comparison). There are presently two choices for calibration curves beyond 12,410 years BP: IntCal04 (Hughen et al., 2004) to 26,000 years or our calibration curve (Fairbanks et al., 2005) from 0 to 55,000 years BP. In our judgment the choice is clear but let us review the differences. The IntCal04 includes predominantly laminated sediments from the Cariaco Basin from 11,900 to 14,000 years BP along with coral data from numerous investigators of varying sample quality based on the reported presence of calcite in samples analyzed by some of the contributors. In contrast, our calibration program (Fairbanks et al., 2005; 2007) uses the 1382-ring floating tree ring data set from Kromer et al., (2004) for the time interval between 12,600 and 14,000 yrs BP anchored by our coral data set. Over this time interval, the Caricao data set used by IntCal04 differs by more than 200 years from the tree ring and our coral calibration data. The photo images of the Cariaco sediment layering (Hughen et al., 2004) shows very weak to indistinct layers in the 13,250 to 14,000 year interval where the offset of Cariaco data with the tree ring and coral data sets is most apparent. In a recent study (*Bondevik et al., 2006), Reimer, the lead author of the IntCal04 paper) and her colleagues retract the Cariaco calibration data in IntCal04 data set and IntCal04 calibration curve and inserted the floating tree ring data set in its place. In their 2006 paper they state that:

 The part of the new calibration curves that relies on tree-ring evidence (IntCal04) dates back to 12,410 calendar (cal) yr B.P. Beyond that and back to 14,700 cal yr B.P., IntCal04 is mainly constructed from 14C dates of foraminiferas from Venezuela.s Cariaco basin that are corrected for a constant reservoir age of 405 years. However, it has been proposed that the latter increased up to 650 years during the Bolling/Allerod. We therefore replaced that part of IntCal04 with a new, floating tree-ring curve composed of 1382 rings between 10,650 and 12,000 14C yr B.P. . Thus our tree-ring record from IntCal04, combined with the new, floating tree-ring curve, represents a true terrestrial curve that extends across most of the studied interval.  

All previous attempts to use layered sediments for radiocarbon calibration purposes have not stood the test of time and the Cariaco basin calibration data used in IntCal04 are apparently no exception (Bondevik et al., 2006).

From 14,000 to 26,000 years BP, 80% of the data in the IntCal04 were provided by our laboratory and we have subsequently doubled the amount of data in the 14,000 to 26,000 year BP time interval (Cao et al., 2006; Fairbanks et al., 2005; 2006).

IntCal04 ends at 26,000 cal yr B.P. representing only 50% of the radiocarbon age dating range. Our calibration extends to the limits of radiocarbon age dating to 50,000 cal yrs B.P. using the same coral sample and data quality control measures and dating techniques as applied to our younger samples and those we provided to IntCal04.

Another difference between the selections of IntCal04 versus our calibration program is philosophical. Seven years elapsed between publication of IntCal98 and IntCal04 although the majority of new data between 14,000 and 26,000 are from our laboratory. It is unclear when the next internationally ratified calibration curve will be approved but it is presumably many years away. Meanwhile, Reimer and colleagues (Bondevik et al., 2006) have already retracted a segment of the Cariaco layered sediment data set used in IntCal04 but the .official. IntCal04 file has not been revised. On the other hand, we are increasing the number of new calibration data pairs by 50% per year over the next 3 years. We appreciate the value of a stable internationally-ratified radiocarbon calibration curve, however researchers want the best available calibration curve in order to make the most accurate and precise conversion of radiocarbon years to calendar years. Considering the dramatic increase in ocean, climate, and archeological research spanning the deglacial, glacial and Marine Isotope Stage 3, there is a high and growing demand for radiocarbon calibration. We recommend that researchers and editors always list their raw radiocarbon ages and laboratory sample identification code and simply identify the calibration version used for their calibrated ages. This permits anyone to revise calibrated ages as our calibration curve is periodically updated over the next three years. In order to ensure that there is not a proliferation of calibration curves using outdated versions of our calibration data, we only offer an on line version. We will update our calibration curve every year and publish the data within 12 months of the update. To better serve the archeological community, we will also release the calibration data and access to our curve to CalPal at the same time we update our curve. The curve will be updated every year on Jan 1 and versions are identified as Fairbanks followed by the month and year such as Fairbanks0107 for the upcoming version. There are already enough calibration data such that our curve is stable and the primary improvements with future versions will be in the reduction in computed calendar year uncertainties. We continue to measure the 231Pa/235U ages of the samples that have been exposed to vados fresh water in order to provide quality assurance. Our goal is to have redundant 231Pa/235U dates on all calibrations ages between 30,000 and 55,000 years BP within one year of publishing new 230Th/234U/238U dates.

*Bondevik, S., J. Mangerud, H.H. Birks, S. Gulliksen and P. Reimer, 2006. Changes in North Atlantic radiocarbon reservoir ages during the Allerod and Younger Dryas. Science, 312, 1514-1517.


Appendix C

C14 dating affirms Scripture/Scripture affirms C14 dating!

San Francisco Chronicle

A judgment about Solomon
Evidence supports Hebrew kingdoms in biblical times

David Perlman, Chronicle Science Editor

Deep in the ruins of a Hebrew town sacked nearly 3,000 years ago by an Egyptian Pharaoh, scientists say they have discovered new evidence for the real-life existence of the Bible's legendary kingdoms of David and Solomon.

The evidence refutes recent claims by other researchers who insist that the biblical monarchs were merely mythic characters, created by scholars and scribes of antiquity who made up the tales long after the events to buttress their own morality lessons.

The debate, however, is not likely to subside, for archaeology is a field notable for its lengthy quarrels among partisans, however scientific they may be.

The latest evidence comes from Israeli and Dutch archaeologists and physicists after seven years of digging at a historic site called Tel Rehov. The site is in the Jordan valley of Israel, where successive settlements rose and fell over the centuries.

Using highly sophisticated techniques for establishing dates through the decay rate of radioactive carbon, the scientists have pinned down the time of a disputed moment in history, recorded in the Bible, when a Pharaoh now known as Shoshenq I invaded Jerusalem.

As the book of Chronicles relates in the Old Testament, Shoshenq (the Bible called him Shishak) came "with twelve hundred chariots and threescore thousand horsemen" and plundered Israel's capital, as well as such towns and fortresses as Rehov, Megiddo and Hazor.

The Pharaoh later listed those conquests on a monument in the temple of Amun at Karnak, where the Egyptian city of Luxor now stands.

11=Gaza, Genesis 10:19, Joshua 10:41

12=Makkedah, Joshua 10:10


14=Aijalon, Joshua 21:24


16=Beth- horon, Joshua 10:10

17=Gibeon, Joshua 9:3

18=Mahanaim, Genesis 32:2, Joshua13:26



21=Adoraim, 2 Chronicles 11:9

22=Hapharaim, Joshua 19:9

23=Rehob, Numbers 13:21, Joshua 19:28


25= Shunem, Joshua 19:18

26=Taanach, Joshua 12:21

27=Megiddo, Joshua 12:21

28=Adar, Joshua 15:3


Temple of Amon

closeup of lists

(List and second photo from

The new timetable places Shoshenq's rampage and looting at Rehov in the 10th century rather than the 9th, a highly significant difference. It sets the date at about 925 B.C., some five years after Solomon was said to have died, and some 80 years earlier than other archaeologists maintain.

Those scholars, known in the world of archaeology as "minimalists," insist that both David and Solomon were little more than tribal chieftains, and certainly not the mighty monarchs of the Bible.

A report on the new evidence appears today in the journal Science by Hendrik Bruins, a desert researcher at Ben-Gurion University of the Negev in Israel, Johannes van der Plicht of the Center for Isotope Research at the University of Groningen in the Netherlands, and Amihai Mazar of the Hebrew University of Jerusalem, the principal archaeologist at Tel Rehov.

In a telephone interview, Mazar said that one specific "layer of destruction" at the site yielded a harvest of charred grain seeds and olive pits that enabled his colleagues to date them with an unusually high level of precision. The dates of both earlier and later layers showed clearly how the successive layers of occupation could be determined from the 12th through the 9th centuries B.C., he said.

"They provide a precise archaeological anchor for the united monarchies of the time of David and Solomon," Mazar said. "The pottery we found there also tells us that the conquest dates from the same period as Meggido, when its mighty gates and walls and temples were also destroyed by Shoshenq's armies."

More than 40 years ago the late Yigael Yadin, who won fame as an army officer during Israel's war for independence, turned to archaeology and after excavating the imposing ruins at Megiddo maintained that they were in fact destroyed during the so-called Solomonic period.

Recently, however, a group of archaeologists led by Israel Finkelstein of Tel Aviv University working at Megiddo has insisted that the so-called Solomon's gate there dates from a much later time -- perhaps 100 or even 200 years after Solomon.

Finkelstein read a copy of the Mazar report that was sent him by e-mail. After replying that Mazar "is a fine scholar," he insisted that "there are many problems with his archaeological data" and that the samples of material used for the radiocarbon dating are at best questionable.

In the past, Finkelstein has accused Mazar of harboring a "sentimental, somewhat romantic approach to the archaeology of the Iron Age," according to an earlier account in Science.

On Thursday, however, one of the leaders in the archaeology of Israel, Professor Lawrence E. Stager, who is director of Harvard University's Semitic Museum, dismissed the claims of Finkelstein and the other archaeologists who share his views.

"Mazar and his colleagues have now put another nail in the coffin of Finkelstein's theories," Stager said. "There's no question that Rehov and the other cities that Shoshenq conquered were indeed there at the time of Solomon.

"We don't need to rely any more only on the Bible or on Shoshenq's inscriptions at Karnak to establish that Solomon and his kingdom really existed, because we now have the superb evidence of the radiocarbon dates."

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Radio-dating backs up biblical text

11 September 2003
The 500 meter-long tunnel still carries water to the
city of David

An ancient waterway, described in the Bible, has been located and radiocarbon-dated to around 700 BC1.

The half-kilometre Siloam Tunnel still carries water from the Gihon Spring into Jerusalem's ancient city of David. According to verses in Kings 2 and Chronicles 2 2, it was built during the reign of the King Hezekiah - between 727 BC and 698 BC - to protect the city's water supply against an imminent Assyrian siege. Critics argue that a stone inscription close to the exit dates the tunnel at around 2 BC.

To solve the conundrum, geologist Amos Frumkin, of the Hebrew University of Jerusalem, and colleagues looked at the decay of radioactive elements - such as carbon in plants and thorium in stalactites - in tunnel samples.

The plaster lining the tunnel was laid down around 700 BC, says Frumkin's team. A plant trapped inside the waterproof layer clocked in at 700-800 BC, whereas a stalactite formed around 400 BC. "The plant must have been growing before the tunnel was excavated; the stalactite grew after it was excavated," explains Frumkin.

The study "makes the tunnel's age certain", says archaeologist Henrik Bruins of Ben-Gurion University of the Negev, Israel. The Siloam Tunnel is now the best-dated Iron Age biblical structure so far identified.

The remains of buildings and structures described in the Bible are notoriously difficult to find. Specimens are rare, poorly preserved, hard to identify and often troublesome to access. Says James Jones, Bishop of Liverpool, UK: "This scientific verification of historical details in the Bible challenges those who do no wish to take it seriously."

Tunnel vision

The samples also help to explain how the tunnel was built. The passage is sealed with layers of plaster, the deepest and oldest of which is directly above the bedrock, with no sediment between. This shows that the plaster was applied immediately after the tunnel was built, Frumkin says.

"It's also quite unique to find well-preserved plant remains in plaster," says Bruins. Workers may have made up huge quantities outside the tunnel, where the plants could have become mixed in, and then taken it inside.

Large enough to walk inside, the Siloam Tunnel zigzags through an ancient hill. Its carved inscription describes how two teams of men, starting on opposite sides of the mountain, managed to meet in the middle. They may have followed a natural fissure in the limestone rock, Bruin suggests.

It's quite unique to find well-preserved plant remains in plaster
Henrik Bruins
Ben-Gurion University

Unusually, the inscription does not name King Hezekiah - other monarchs commonly boasted of their architectural achievements in stone. The carving is six metres inside the tunnel, so it must have been made by lamplight.

"It wasn't meant to be seen by the public," says Biblical historian Andrew Millard of Liverpool University, UK. "I think it was the workmen recording what an extraordinary feat they had accomplished."

  1. Frumkin, A., Shimron, A. & Rosenbaum, J. Radiometric dating of the Siloam Tunnel, Jerusalem. Nature, 425, 169 - 171, (2003). |Article|
  2. 2 Kings 20:20; 2 Chronicles 32:3,4.

© Nature News Service / Macmillan Magazines Ltd 2003

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