Cross-fault triggering in the November 1987 Superstition Hills Earthquake Sequence, southern California
Abstract
Two large strike-slip ruptures 11.4 hours apart occurred on intersecting, nearly orthogonal, vertical faults during the November 1987 Superstition Hills earthquake sequence in southern California. This sequence is the latest in a northwestward progression of earthquakes (1979, 1981, and 1987) rupturing a set of parallel left-lateral cross-faults that trend northeast between the Brawley seismic zone and Superstition Hills fault, a northwest trending main strand of the San Jacinto fault zone. The first large event (MS=6.2) in the 1987 sequence ruptured the Elmore Ranch fault, a cross-fault that strikes northeasterly between the Brawley seismic zone and the Superstition Hills main fault. The second event (MS=6.6) initiated its rupture at the intersection of the cross-fault and main fault and propagated towards the southeast along the main fault. The following hypotheses are advanced; (1) slip on the cross-fault locally decreased normal stress on the main fault, and triggered the main fault rupture after a delay; and (2) the delay was caused by fluid diffusion. It is inferred that the observed northwestward progression of ruptures on cross-faults may continue. The next cross-fault expected to rupture intersects both the San Andreas fault and the San Jacinto fault zone. We hypothesize that rupture of this cross-fault may trigger rupture on either of these main faults by a mechanism similar to that which occurred in the Superstition Hills earthquake sequence.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- February 1989
- DOI:
- 10.1029/GL016i002p00199
- Bibcode:
- 1989GeoRL..16..199H
- Keywords:
-
- Earthquakes;
- Geological Faults;
- Seismology;
- Southern California;
- Earth Crust;
- Shear Stress;
- Seismology: Earthquake prediction;
- Tectonophysics: Continental tectonics;
- Tectonophysics: Structural geology (crustal structure and mechanics);
- Information Related to Geographic Region: North America;
- Seismology: Seismicity