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![Marginal posterior layer-age PDFs calculated for the Wrightwood site using only stratigraphic ordering constraints. Dotted, dashed, and solid lines represent marginal PDFs derived from prior estimates based only on radiocarbon age control, order-only constraints using the ID method of Biasi et al. (2002), and our MCMC simulation method, respectively. All marginal PDFs have been normalized to their maximum value to facilitate comparisons between each of the PDFs. Large bold labels W3–W14 show the location of earthquake events within the stratigraphy; stars denote that the earthquake event occurred during the deposition of the stratigraphic interval.]()
![Marginal posterior earthquake age PDFs calculated for the Wrightwood site using minimum time-separation constraints inferred from relative peat thicknesses and peat-growth rates. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering and minimum time-separation constraints were applied; solid lines show our estimates using simulation.]()
![Marginal posterior earthquake age PDFs calculated for the Wrightwood site using the peat-growth method described in the text. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering and minimum time-separation constraints were applied; solid lines show our simulated estimates using the method described in the text.]()
![Marginal posterior earthquake age PDFs calculated for the Wrightwood site using only stratigraphic ordering constraints. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering constraints were applied; solid lines show our estimates using simulation.]()
![Marginal posterior layer-age PDFs calculated for the Wrightwood site using the peat-growth method described in the text. See the caption to Figure 4 for a description of all labels except solid and dashed lines. The dashed lines represent marginal PDFs determined using the ID method when both stratigraphic ordering and minimum time-separation constraints were applied. Solid lines show our simulated estimate of posterior marginal PDFs using the peat-growth method presented in the text.]()
![Relationship between total peat thickness and time at the Wrightwood site. Small back dots denote the mean age of each peat-bearing layer, while the horizontal bars denote 95% bounds on these ages. Layer ages plotted in this figure are derived by imposing stratigraphic order constraints on the prior estimates of the layer ages determined from radiocarbon analysis. Note that constant peat-growth rates plot as a straight line in this graph, and the inverse of the slope (1/slope) is equal to the growth rate (in units of yr/cm). Thus, while peat-growth rates are approximately constant throughout large intervals of the section, there are excursions within some intervals. Large circles centered about mean ages denote units used to determine peat-growth rates (θrate) based on the algorithm presented in this work. In addition, the names of these layers are shown in bold next to the corresponding mean layer age.]()
![Marginal posterior layer-age PDFs calculated for the Wrightwood site using minimum time-separation constraints inferred from relative peat thicknesses and peat-growth rates. See the caption to Figure 4 for a description of all labels except solid and dashed lines. The dashed lines represent marginal PDFs determined using the ID method when both stratigraphic ordering and minimum time-separation constraints were applied. Solid lines show our simulated estimate of posterior marginal PDFs when minimum time-separation constraints are used.]()
![Detailed map of the Wrightwood site; green lines show roads (including HW#2, north of the site, and the water company access road, to the south). Yellow lines are 1-m contour intervals (bold 5 m); red lines indicate the main fault zone to the north and the secondary fault zone to the south. Arrows indicate sense of slip, with barbs indicating oblique extension and teeth oblique compression. Red shading indicates intense distributed deformation. Blue line represents Swarthout Creek.]()
![Composite stratigraphic section of the Wrightwood site. To date only the upper ∼12 m, which span the past ∼1600 yr, have been intensively investigated. Black units are peat layers (numbered in increments of 5), and patterned units represent clastic deposits; patterns reflect facies. 14C calendar ages include 95% uncertainties.]()
![Map of the gully part of the Wrightwood site where Swarthout Creek crosses the San Andreas fault. Gray lines are 25-cm contours (bold 1 m); blue lines are streams, including Swarthout Creek (heavy); a major abandoned channel that erodes the fault zone to the east (blue polygon); and small streams filled with material offset by the 1857 rupture; yellow rectangles indicate excavations, and the yellow polygon covers the map extent of the cleaned and progressively cut back gully wall. The solid brown line separates colluvium from fluvial and peat facies to the southeast; the dotted brown line separates fluvial and peat facies from peat and debris flow facies, prior to the W3 rupture. Green defines a fold active during the W4 rupture, red locates 1857 traces, and purple indicates earlier ruptures since event W4.]()
![Simple structural models of the Wrightwood site. (A) Surface expression of the major faults, with main fault trace and secondary fault zone indicated on figure. The secondary fault zone is dominantly right lateral but has extension on its west side and compression on its east side (fault symbols on map). (B) Preferred model, with cross sections to illustrate how the transtensive and transpressive portions of the Secondary fault are related and how it might relate to the Main Trace at depth. (C, D) Two alternative models that were rejected.]()
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![Diagram illustrating probable correlation of Event 2 at Frazier Mountain with similarly dated events at the Bidart Fan, Pallett Creek, and Wrightwood sites. Gray vertical bars represent 2σ age ranges for earthquakes at Bidart fan reported by Grant and Sieh (1994) and for Pallett Creek and Wrightwood reported by Biasi et al. (2002). Historic earthquake correlations for the 1857 and 1812 earthquakes are shown as horizontal lines. Event 2 at Frazier Mountain appears to correlate with event B at the Bidart fan site to the northwest and events V and W4 at the Pallett Creek and Wrightwood sites, respectively, to the southeast.]()
![Peat accumulation plots for Pallett Creek and Wrightwood sites. Peat thicknesses were measured perpendicular to bedding at their thickest point. Measurements were compiled from mapped exposures and reported sample thicknesses. Thicknesses were plotted at the mean dates of their ordering constrained date distributions (dotted lines, Figs. 2, 3). Average peat accumulation rates were estimated where multiple dates define segments by drawing straight lines through the circles. Higher rates (smaller minimum time separation constraints) were used at “growth spurts” where the average rate would otherwise force nearby layer dates into unlikely posterior distributions. For Wrightwood a single rate of 15 yr/cm was applied because the available data do not justify a more detailed model. Pallett Creek peat accumulation resolvably varied with time. Both sites experienced slow accumulation from A.D. 350–600. Event W14 occurred during this slow period and is poorly resolved as a result.]()
![Probability distribution functions for fully constrained ages of paleoearthquakes at the Wrightwood site (updated from a preliminary version in Weldon et al., 2004; the earthquake age distributions and qualification of earthquakes in the old section [previously labeled the “deep section”] have changed). Each curve (in alternating gray and black for clarity) represents the likelihood that the earthquake occurred in a given 10-year bin; historic earthquakes in 1857 and 1812 are lines that extend to a probability of 1.0. The dashed curve in the young section (PCT) is earthquake T from the Pallett Creek paleoseismic site (Biasi et al., 2002), whereas the dashed curves in the old section (W380, W390, and W520) are from the Wrightwood site but are qualified as “possible.” The middle section (a.d. 500 to 1500 b.c.) includes approximately one dozen earthquakes that have not been dated. The horizontal lines indicate the number of paleoearthquakes and age range of stratigraphy observed in the indicated trenches (K. M. Scharer, unpublished data).]()
![Product overlaps of event PDFs with themselves range from 0.02 to 0.38. Events 6 to 24 are the relatively precise event dates from Pallett Creek and Wrightwood sites (Biasi et al., 2002).]()
![(A) 1930 1:18,000 Spence photos with (B) 1928 1:24,000 U.S. Geological Survey topography and geology. Yellow lines are 25-ft contours (bold 100 ft); red lines are fault traces; green lines are roads; blue lines are streams; and bold is Swarthout Creek. Box indicates location of Figure 2, which includes the Wrightwood site where Government Canyon joins Swarthout Creek. Active fault traces have transtensive geometry and are flanked by late Holocene highs (orange).]()
![Probability density functions representing the timing of earthquakes for the past 2000 yr from paleoseismic sites on the San Andreas and San Jacinto faults near their juncture. The Wrightwood site (Fumal et al., 2002) is shown in the middle, the Mystic Lake site (this study) and the Hog Lake site (Rockwell et al., 2015) on the San Jacinto fault are shown to the right, and the Pitman Canyon (Seitz et al., 1997), Plunge Creek (McGill et al., 2002), and Burro Flats (Yule and Sieh, 2001) sites on the San Andreas fault south of the San Andreas–San Jacinto juncture are on the left. Event histories from the San Andreas sites are updated event ages from Field et al. (2013). RI—recurrence interval. Individual event PDFs for each paleoseismic site are labeled with a letter representing the site name, and a number representing the chronological order of the events at each site.]()
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Journal Article
Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
Publisher: Seismological Society of America
Published: 01 October 2002
Bulletin of the Seismological Society of America (2002) 92 (7): 2704–2725.
...R. J. Weldon, II; T. E. Fumal; T. J. Powers; S. K. Pezzopane; K. M. Scharer; J. C. Hamilton Abstract Thirty-eight trenches and natural exposures across the San Andreas fault zone, four km northwest of Wrightwood, California, reveal the structure and stratigraphy of this paleoseismic site. A 25-m...
FIGURES
| View All (16)
Journal Article
Evidence for Large Earthquakes on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site: a.d. 500 to Present
Publisher: Seismological Society of America
Published: 01 October 2002
Bulletin of the Seismological Society of America (2002) 92 (7): 2726–2760.
...T. E. Fumal; R. J. Weldon, II; G. P. Biasi; T. E. Dawson; G. G. Seitz; W. T. Frost; D. P. Schwartz Abstract We present structural and stratigraphic evidence from a paleoseismic site near Wrightwood, California, for 14 large earthquakes that occurred on the southern San Andreas fault during the past...
FIGURES
| View All (21)
Image
Marginal posterior layer-age PDFs calculated for the Wrightwood site usin...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 4. Marginal posterior layer-age PDFs calculated for the Wrightwood site using only stratigraphic ordering constraints. Dotted, dashed, and solid lines represent marginal PDFs derived from prior estimates based only on radiocarbon age control, order-only constraints using the ID
Image
Marginal posterior earthquake age PDFs calculated for the Wrightwood site...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 7. Marginal posterior earthquake age PDFs calculated for the Wrightwood site using minimum time-separation constraints inferred from relative peat thicknesses and peat-growth rates. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering
Image
Marginal posterior earthquake age PDFs calculated for the Wrightwood site...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 11. Marginal posterior earthquake age PDFs calculated for the Wrightwood site using the peat-growth method described in the text. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering and minimum time-separation constraints were applied
Image
Marginal posterior earthquake age PDFs calculated for the Wrightwood site...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 5. Marginal posterior earthquake age PDFs calculated for the Wrightwood site using only stratigraphic ordering constraints. Dashed lines show earthquake age PDFs estimated using the ID method when stratigraphic ordering constraints were applied; solid lines show our estimates using
Image
Marginal posterior layer-age PDFs calculated for the Wrightwood site usin...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 10. Marginal posterior layer-age PDFs calculated for the Wrightwood site using the peat-growth method described in the text. See the caption to Figure 4 for a description of all labels except solid and dashed lines. The dashed lines represent marginal PDFs determined using the ID
Image
Relationship between total peat thickness and time at the Wrightwood site. ...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 3. Relationship between total peat thickness and time at the Wrightwood site. Small back dots denote the mean age of each peat-bearing layer, while the horizontal bars denote 95% bounds on these ages. Layer ages plotted in this figure are derived by imposing stratigraphic order constraints
Image
Marginal posterior layer-age PDFs calculated for the Wrightwood site usin...
in Deducing Paleoearthquake Timing and Recurrence from Paleoseismic Data, Part I: Evaluation of New Bayesian Markov-Chain Monte Carlo Simulation Methods Applied to Excavations with Continuous Peat Growth
> Bulletin of the Seismological Society of America
Published: 01 February 2008
Figure 6. Marginal posterior layer-age PDFs calculated for the Wrightwood site using minimum time-separation constraints inferred from relative peat thicknesses and peat-growth rates. See the caption to Figure 4 for a description of all labels except solid and dashed lines. The dashed lines
Image
Detailed map of the Wrightwood site; green lines show roads (including HW#2...
in Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 2. Detailed map of the Wrightwood site; green lines show roads (including HW#2, north of the site, and the water company access road, to the south). Yellow lines are 1-m contour intervals (bold 5 m); red lines indicate the main fault zone to the north and the secondary fault zone
Image
Composite stratigraphic section of the Wrightwood site. To date only the up...
in Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 3. Composite stratigraphic section of the Wrightwood site. To date only the upper ∼12 m, which span the past ∼1600 yr, have been intensively investigated. Black units are peat layers (numbered in increments of 5), and patterned units represent clastic deposits; patterns reflect facies. 14
Image
Map of the gully part of the Wrightwood site where Swarthout Creek crosses ...
in Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 6. Map of the gully part of the Wrightwood site where Swarthout Creek crosses the San Andreas fault. Gray lines are 25-cm contours (bold 1 m); blue lines are streams, including Swarthout Creek (heavy); a major abandoned channel that erodes the fault zone to the east (blue polygon
Image
Simple structural models of the Wrightwood site. (A) Surface expression of ...
in Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 14. Simple structural models of the Wrightwood site. (A) Surface expression of the major faults, with main fault trace and secondary fault zone indicated on figure. The secondary fault zone is dominantly right lateral but has extension on its west side and compression on its east side
Journal Article
The San Andreas Fault Paleoseismic Record at Elizabeth Lake: Why are There Fewer Surface‐Rupturing Earthquakes on the Mojave Section?
Publisher: Seismological Society of America
Published: 27 April 2021
Bulletin of the Seismological Society of America (2021) 111 (3): 1590–1613.
... misaligned with the regional plate motion. The Frazier Mountain, Elizabeth Lake, Pallett Creek, Wrightwood, and Pitman Canyon paleoseismic sites are located on this relatively linear surface trace of the San Andreas fault between fault bends. Our paleoseismic investigations at Elizabeth Lake document 4–5...
FIGURES
| View All (11)
Includes: Supplemental Content
Image
Diagram illustrating probable correlation of Event 2 at Frazier Mountain wi...
in Evidence for Two Surface Ruptures in the Past 500 Years on the San Andreas Fault at Frazier Mountain, California
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 12. Diagram illustrating probable correlation of Event 2 at Frazier Mountain with similarly dated events at the Bidart Fan, Pallett Creek, and Wrightwood sites. Gray vertical bars represent 2σ age ranges for earthquakes at Bidart fan reported by Grant and Sieh ( 1994 ) and for Pallett
Image
Peat accumulation plots for Pallett Creek and Wrightwood sites. Peat thickn...
in Paleoseismic Event Dating and the Conditional Probability of Large Earthquakes on the Southern San Andreas Fault, California
> Bulletin of the Seismological Society of America
Published: 01 October 2002
Figure 4. Peat accumulation plots for Pallett Creek and Wrightwood sites. Peat thicknesses were measured perpendicular to bedding at their thickest point. Measurements were compiled from mapped exposures and reported sample thicknesses. Thicknesses were plotted at the mean dates of their ordering
Image
![Probability distribution functions for fully constrained ages of paleoearthquakes at the Wrightwood site (updated from a preliminary version in Weldon et al., 2004; the earthquake age distributions and qualification of earthquakes in the old section [previously labeled the “deep section”] have changed). Each curve (in alternating gray and black for clarity) represents the likelihood that the earthquake occurred in a given 10-year bin; historic earthquakes in 1857 and 1812 are lines that extend to a probability of 1.0. The dashed curve in the young section (PCT) is earthquake T from the Pallett Creek paleoseismic site (Biasi et al., 2002), whereas the dashed curves in the old section (W380, W390, and W520) are from the Wrightwood site but are qualified as “possible.” The middle section (a.d. 500 to 1500 b.c.) includes approximately one dozen earthquakes that have not been dated. The horizontal lines indicate the number of paleoearthquakes and age range of stratigraphy observed in the indicated trenches (K. M. Scharer, unpublished data).](https://gsw.silverchair-cdn.com/gsw/Content_public/Journal/bssa/97/4/10.1785_0120060137/5/s_a06137-uid002.jpeg?Expires=2147483647&Signature=x9Mj8tC3d2CAZ3e4-wD3etqI~x87OkeTz9GwoOb0dsomYyW7simLztDh-kTTMBIaCF9fXZ0YofaILOeszq5pwVD77mhIIxKcQIo-i9qwqquAAzAgtnX4Db7W3MiPgUeIYz6lSAfoFIyQbirpUHojegA6GrBZJ2w0953nhCMLr72bFd3OKcXTNnsh1gG4NeYewbS-jCCm0T0qSnLrVi9DDjy5vct2ChnmtsrAvZF5vGCpfu9J8WciKB5t0iNM~R6IvFc1hp74Oz8oixqpfRIRJMYCngrCNJ439VGiIyOF3gMmUh3cZRnLJo3jWHtuQ6mlc4GKTKCVO96j0q~O1Q9h8g__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Probability distribution functions for fully constrained ages of paleoearth...
in Paleoearthquakes on the Southern San Andreas Fault, Wrightwood, California, 3000 to 1500 b.c.: A New Method for Evaluating Paleoseismic Evidence and Earthquake Horizons
> Bulletin of the Seismological Society of America
Published: 01 August 2007
Figure 2. Probability distribution functions for fully constrained ages of paleoearthquakes at the Wrightwood site (updated from a preliminary version in Weldon et al. , 2004 ; the earthquake age distributions and qualification of earthquakes in the old section [previously labeled the “deep
Image
Product overlaps of event PDFs with themselves range from 0.02 to 0.38. E...
in San Andreas Fault Rupture Scenarios from Multiple Paleoseismic Records: Stringing Pearls
> Bulletin of the Seismological Society of America
Published: 01 April 2009
Figure 6. Product overlaps of event PDFs with themselves range from 0.02 to 0.38. Events 6 to 24 are the relatively precise event dates from Pallett Creek and Wrightwood sites ( Biasi et al. , 2002 ).
Image
(A) 1930 1:18,000 Spence photos with (B) 1928 1:24,000 U.S. Geological Surv...
in Structure and Earthquake Offsets on the San Andreas Fault at the Wrightwood, California, Paleoseismic Site
> Bulletin of the Seismological Society of America
Published: 01 October 2002
2 , which includes the Wrightwood site where Government Canyon joins Swarthout Creek. Active fault traces have transtensive geometry and are flanked by late Holocene highs (orange).
Image
Probability density functions representing the timing of earthquakes for th...
in A 3700 yr paleoseismic record from the northern San Jacinto fault and implications for joint rupture of the San Jacinto and San Andreas faults
> Geosphere
Published: 12 October 2018
Figure 13. Probability density functions representing the timing of earthquakes for the past 2000 yr from paleoseismic sites on the San Andreas and San Jacinto faults near their juncture. The Wrightwood site ( Fumal et al., 2002 ) is shown in the middle, the Mystic Lake site (this study
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