Century-long average time intervals between earthquake ruptures of the San Andreas Fault in the Carrizo Plain, California

Paleoseismological data constrain the age, location, and associated magnitude of past surface-rupturing earthquakes; these are critical parameters for developing and testing fault behavior models and characterizing seismic hazard. We present new earthquake evidence and radiocarbon analyses that refi...

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Bibliographic Details
Published in:Geology (Boulder) 2010-09, Vol.38 (9), p.787-790
Main Authors: Akciz, Sinan O, Ludwig, Lisa Grant, Arrowsmith, J. Ramon, Zielke, Olaf
Format: Article
Language:English
Subjects:
absolute age
active faults
alluvial fans
Bidart Fan
C-14
California
carbon
Carbon dating
Carrizo Plain
Cenozoic
Chronology
dates
Earthquakes
Faults
Geology
Hazards
Holocene
Intervals
isotopes
magnitude
modern
paleoseismicity
periodicity
Plate tectonics
Quaternary
Quaternary geology
radioactive isotopes
rupture
San Andreas Fault
San Luis Obispo County California
secular variations
Seismic engineering
Seismic phenomena
Seismology
Slip
Structural geology
United States
upper Holocene
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Summary:Paleoseismological data constrain the age, location, and associated magnitude of past surface-rupturing earthquakes; these are critical parameters for developing and testing fault behavior models and characterizing seismic hazard. We present new earthquake evidence and radiocarbon analyses that refine the chronology of the six most recent earthquakes that ruptured the south-central San Andreas fault in the Carrizo Plain (California, United States) at the Bidart Fan site. Modeled 95 percentile ranges of the earthquakes prior to the A.D. 1857 earthquake are A.D. 1631-1823, 1580-1640, 1510-1612, 1450-1475, and 1360-1452. The average time interval between the last six earthquakes that ruptured the San Andreas fault in the Carrizo Plain is 88±41 yr. This is less than the time since the most recent A.D. 1857 earthquake, less than all reported average intervals of prehistoric earthquakes along the entire San Andreas fault, and significantly shorter than the 235 yr average used in recent seismic hazard evaluations. The new chronological data combined with recent slip studies imply that the magnitudes of the earthquakes that ruptured the southern San Andreas fault in the Carrizo Plain since ca. A.D. 1360 were variable, and suggest that the widely held view of rare but great surface rupturing earthquakes along this portion of the southern San Andreas fault should be reevaluated.
ISSN:0091-7613
1943-2682
DOI:10.1130/G30995.1