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R.A. Harris

Publications and source records attributed to R.A. Harris.

22 records · Page 2Linked to original sources
USGS1995

Influence of static stress changes on earthquake locations in southern California

Earthquakes induce changes in static stress on neighbouring faults that may delay, hasten or even trigger subsequent earthquakes 1–10 . The length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment, but is presently unknown. Here we use an elastic half-space model 11 to estimate the static stress changes generated by damaging (magnitude M ≥5) earthquakes in southern California over the past 26 years, and to investigate the influence of these changes on subsequent earthquake activity. We find that, in the 1.5-year period following a M ≥5 earthquake, any subsequent nearby M ≥5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake. After this period, damaging earthquakes are equally likely to rupture loaded and relaxed faults. Our results suggest that there is a short period of time following a damaging earthquake in southern California in which simple Coulomb failure stress models could be used to identify regions of increased seismic hazard.

California↗
USGS1992

Changes in static stress on southern California faults after the 1992 Landers earthquake

The magnitude 7.5 Landers earthquake of 28 June 1992 was the largest earthquake to strike California in 40 years. The slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults; these changes in stress should in turn affect the likelihood of future earthquakes. Stress changes that load faults towards failure have been cited as the cause of small 1–5 , moderate 6 and large 7 earthquakes; conversely, those that relax neighbouring faults have been related to a decrease in seismicity 5 . Here we use an elastic half-space model 8 to estimate the stress changes produced by the Landers earthquake on selected southern California faults, including the San Andreas. We find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4.5, and that the largest changes (1–10 bar), occurring on part of the San Bernardino segment of the San Andreas fault, may have decreased the time to the next magnitude 8 earthquake by about 14 years.

California↗