RAPID ESTIMATION OF RUPTURE DIRECTIVITY - APPLICATION TO THE 1992 LANDERS (MS=7.4) AND CAPE MENDOCINO (MS=7.2), CALIFORNIA EARTHQUAKES

Using empirical Green functions with regional and teleseismic surface waves, it is possible to resolve fault finiteness effects, in many cases uniquely defining the fault plane for relatively large earthquakes. The technique requires very little data processing and can be applied in near-real time with the current distribution of seismic stations. The Landers strike-slip earthquake was dominated by two sub-events with predominantly north-northwestward rupture. The second sub-event was 1.5 times larger and rotated in strike by 12-degrees counter-clockwise relative to the first. The Cape Mendocino thrust event had a relatively smooth rupture that propagated to the southwest on a shallow dipping fault.