J. Ramón Arrowsmith

Thumbnail image of Slip in the 1857 and Earlier Large Earthquakes Along the Carrizo Plain, San Andreas Fault cover sheet

The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a ~350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the ~60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes.

Thumbnail image of Three-Dimensional Excavation and Recent Rupture History along the Cholame Segment of the San Andreas Fault article first page

A paleoseismic study conducted along the Cholame segment of the San Andreas fault provides evidence for three earthquakes and the amount of lateral offset for the most recent event (1857 Fort Tejon earthquake).

Thumbnail image of Recent Rupture History of the San Andreas Fault Southeast of Cholame in the Northern Carrizo Plain, California journal article

We conducted a paleoseismic study on the San Andreas fault (SAF) southeast of Cholame, California, to investigate the record of earthquakes along an 80-km paleoseismic data gap between Parkfield and the Carrizo Plain.

Thumbnail image of Displacement across the Cholame Segment of the San Andreas Fault between 1855 and 1893 from Cadastral Surveys journal article first page

Changes since 1855 in reported section-line lengths and positions of survey monuments that span the San Andreas fault (SAF) were used to measure displacement interpreted to be from the 1857 Fort Tejon earthquake in south-central California. In 1855–1856 James E. Freeman established township and range lines across the SAF between Rancho Cholame and the northern Carrizo Plain. At least 26 1-mile sections lines spanned the SAF in the area between present-day California Highways 46 and 58. Each section line was marked by monuments at the midpoint and endpoints.

Thumbnail image of Climate-Modulated Channel Incision and Rupture History of the San Andreas Fault in the Carrizo Plain article cover sheet

The spatial and temporal distribution of fault slip is a critical parameter in earthquake source models. Previous geomorphic and geologic studies of channel offset along the Carrizo section of the south central San Andreas Fault assumed that channels form more frequently than earthquakes occur and suggested that repeated large-slip earthquakes similar to the 1857 Fort Tejon earthquake illustrate typical fault behavior. We found that offset channels in the Carrizo Plain incised less frequently than they were offset by earthquakes.

Thumbnail image of Analysis of Seismic Activity near Theodore Roosevelt Dam, Arizona, during the Occupation of the EarthScope/USArray Transportable Array journal article first page

Rate and distribution of seismic activity are important indicators of the overall state of tectonic stress within a region. In regions characterized by low levels of seismicity, active fault surfaces are rarely visible at the surface, and the analysis of small-magnitude earthquakes at depth may be the most effective way to identify seismic hazard and risk from ambient tectonic activity.

Thumbnail image of Century-Long Average Time Intervals Between Earthquake Ruptures of the San Andreas Fault in the Carrizo Plain, California journal article cover page

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.

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