S. Horton, A FAULT MODEL WITH VARIABLE SLIP DURATION FOR THE 1989 LOMA-PRIETA, CALIFORNIA, EARTHQUAKE DETERMINED FROM STRONG-GROUND-MOTION DATA, Bulletin of the Seismological Society of America, 86(1), 1996, pp. 122-132
A finite-fault model with variable slip duration is inferred from stro
ng-ground-motion data for the Loma Prieta earthquake. Unlike previous
models, slip duration is found to be consistent with fault width scali
ng. Slip duration varies between 1 and 6 sec at points along the fault
surface with values between 3 and 6 sec, where slip amplitudes obtain
or exceed the average slip of 98 cm. Modest high-frequency modificati
ons of the slip function shape greatly enhance the data fit without si
gnificantly changing the inferred static offset or rupture characteris
tics. This model exhibits bilateral rupture with the propagation rate
of the main energy release of 3 km/sec or less. The moment is 2.3 X 10
(26) dyne-cm, and the largest slip amplitudes occur northwest of the h
ypocenter. The rake varies with position along the fault from dominant
ly strike slip in the southeast to dominantly reverse slip in the nort
hwest.