We tested whether aftershocks could account for the postseismic motions prior to modeling the GPS data. We used first motion locations and mechanisms for 65 aftershocks determined by Hauksson et al. (1995) for the time period January 18, 1994, through June 15, 1994, ranging in magnitude from 4.0 to 5.2.
After estimating the fault area and slip for each aftershock, we calculated the surface displacements by using point dislocations in an elastic half-space (Okada, 1985). The predicted surface displacements from the aftershocks show generally the same sense of motion as the GPS observations. The magnitudes of the motions are less than 10% those of the measured motions, suggesting that at least 90% of the postseismic motion has occurred aseismically.
Back || GPS Observations || Data || Behavior || Aftershocks || Inversions || SAR Observations || SAR Images of Northridge || Comparisons || Next