Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake

TLDR

The 1992 Landers 7.3 earthquake triggered a sudden, widespread increase in seismicity across much of the western United States, especially in geothermal and volcanic regions, suggesting that nonlinear interactions between dynamic strains and crustal fluids may explain the triggering. Triggered earthquakes up to 1,250 km away were confined to persistent seismicity zones and strike‑slip or normal faults, but static stress changes from elastic models are too small to explain the triggering.

Abstract

The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkably sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances up to 1250 kilometers (17 source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity and strike-slip to normal faulting. Many of the triggered areas also are sites of geothermal and recent volcanic activity. Static stress changes calculated for elastic models of the earthquake appear to be too small to have caused the triggering. The most promising explanations involve nonlinear interactions between large dynamic strains accompanying seismic waves from the mainshock and crustal fluids (perhaps including crustal magma).