HR: 0830h
AN: S51E-0087    [PDF]
TI: Evidence for Nonlinear Strong Ground Motion at Rock Sites from Moderate Earthquakes?
AU: * Rubinstein, J L
EM: justin@pangea.stanford.edu
AF: Stanford University Department of Geophysics, 397 Panama Mall, Stanford, CA 94305 United States
AU: Beroza, G C
EM: beroza@pangea.stanford.edu
AF: Stanford University Department of Geophysics, 397 Panama Mall, Stanford, CA 94305 United States
AB: Through the analysis of repeating earthquakes we have identified seismic velocity reductions coincident with both the M6.9 Loma Prieta Earthquake and its largest aftershock, the M5.4 Chittenden Earthquake at distances greater than 20km from the rupture. We attribute these velocity reductions to lasting physical damage to surficial materials in the vicinity of the NCSN stations we analyzed that are caused by the strong motion of these two earthquakes. Our conjecture is that the relatively modest strong ground motion of the Chittenden Earthquake was only able to structurally damage rocks because the rocks had not completely healed from the damage imparted by the Loma Prieta Earthquake 6 months earlier. Using the same cross-correlation technique used to identify the velocity reductions associated with Loma Prieta and Chittenden earthquakes, we will search for velocity variations associated with other M5 earthquakes in Northern California. This will allow us to test the hypothesis that M5 earthquakes will not damage rocks that are in a healed state.
UR: http://pangea.stanford.edu/~jrubinst/nlin.html
DE: 3220 Nonlinear dynamics
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2003 Fall Meeting