The San Andreas fault paleoseismic record at Elizabeth Lake: Why are there fewer surface-rupturing earthquakes on the Mojave section?

Bulletin of the Seismological Society of America
By: , and 

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Abstract

The structural complexity of active faults and the stress release history along the fault system may exert control on the locus and extent of individual earthquake ruptures. Fault bends, in particular, are often invoked as a possible mechanism for terminating earthquake ruptures. However, there are few records available to examine how these factors may influence the along‐fault recurrence of earthquakes. We present a new paleoearthquake chronology for the southern San Andreas fault at Elizabeth Lake and integrate this record with existing paleoearthquake records to examine how the timing and frequency of earthquakes vary through a major restraining bend. This restraining bend features a mature, throughgoing right‐lateral strike‐slip fault, two major fault intersections, proposed subsurface fault dip changes, and a >200  km long section of fault 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 earthquakes, since 1100  C.E., similar to the number of earthquakes recorded at Pallett Creek. In contrast, the Frazier Mountain and Wrightwood sites each record 8–9 earthquakes during this same time period. Differences in earthquake frequency demonstrate that fewer earthquakes rupture the central portion of the restraining bend than occur near the fault bends and intersections. Furthermore, the similarity of earthquake records from the Bidart Fan paleoseismic site northwest of the restraining bend and the Frazier Mountain paleoseismic site suggests that the broad, 30° curve of the Big Bend section of the San Andreas fault exerts less influence on fault rupture behavior than the 3D geometry of the Mojave sections of the fault.

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Publication type Article
Publication Subtype Journal Article
Title The San Andreas fault paleoseismic record at Elizabeth Lake: Why are there fewer surface-rupturing earthquakes on the Mojave section?
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120200218
Volume 111
Issue 3
Year Published 2021
Language English
Publisher Seismological Society of America
Contributing office(s) Earthquake Science Center
Description 24 p.
First page 1590
Last page 1613
Country United States
State California
Other Geospatial Elizabeth Lake, San Andreas fault
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