A fault model with variable slip duration for the 1989 Loma Prieta, California, earthquake determined from strong-ground-motion data

A finite-fault model with variable slip duration is inferred from strong-ground-motion data for the Loma Prieta earthquake. Unlike previous models, slip duration is found to be consistent with fault width scaling. 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 modifications of the slip function shape greatly enhance the data fit without significantly changing the inferred static offset or rupture characteristics. 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 hypocenter. The rake varies with position along the fault from dominantly strike slip in the southeast to dominantly reverse slip in the northwest.