D.C. Agnew
H.O. Johnson
G. Anderson
2003
<p><span>The </span>Salton<span> </span>Trough<span> in southeastern California, United States, has one of the highest seismicity and </span>deformation<span> rates in southern California, including 20 earthquakes M 6 or larger since 1892. From 1972 through 1987, the U.S. Geological </span>Survey<span> (USGS) measured a 41-station </span>trilateration<span> network in this region. We remeasured 37 of the USGS baselines using </span>survey<span>-</span>mode<span> Global Positioning System methods from 1995 through 1999. We estimate the </span>Salton<span> </span>Trough<span> </span>deformation<span> field over a nearly 30-year period through </span>combined<span> analysis of baseline length time series from these two datasets. Our primary result is that strain accumulation has been steady over our observation span, at a resolution of about 0.05 μstrain/yr at 95% confidence, with no evidence for significant long-term strain transients despite the occurrence of seven large </span>regional<span> earthquakes during our observation period. Similar to earlier studies, we find that the </span>regional<span> strain field is consistent with 0.5 ± 0.03 μstrain/yr total engineering shear strain along an axis oriented 311.6° ± 23° east of north, approximately parallel to the strike of the major </span>regional<span> faults, the San Andreas and San Jacinto (all uncertainties in the text and tables are standard deviations unless otherwise noted). We also find that (1) the shear strain rate near the San Jacinto fault is at least as high as it is near the San Andreas fault, (2) the areal dilatation near the southeastern </span>Salton<span> Sea is significant, and (3) one station near the southeastern </span>Salton<span> Sea moved anomalously during the period 1987.95-1995.11.</span></p>
application/pdf
10.1785/0120030014
en
Seismological Society of America
Salton Trough regional deformation estimated from combined trilateration and survey-mode GPS data
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