HR: 0800h
AN: S51A-0230    [Abstracts]
TI: New Ground Motion Prediction Equations Spanning Weak and Strong Ground Motion Levels
AU: Heaton, T H
EM: heaton@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, United States
AU: * Cua, G B
EM: georgia.cua@sed.ethz.ch
AF: Swiss Seismological Service ETH Zurich, Schaffmattstrasse 30, Zurich, CH-8093, Switzerland
AB: We present new set of prediction equations for horizontal peak ground acceleration (PGA) and peak ground velocity (PGV) valid up to 200 km away from earthquakes over the magnitude range 2 &<& M &<& 8. We adopt a functional form used by Cua and Heaton (2007) that allows for a linear dependence of the log of ground motion amplitudes on magnitude for events with M&<&5, and a magnitude-dependent saturation term for M&>&5. We fit this functional form to observed PGA and PGV from 1) a predominantly weak motion southern California dataset, and 2) the Next Generation Attenuation (NGA) strong motion dataset in a single inversion. At the weak motion levels, the new equations are consistent with the small-amplitude equations (Quitoriano, 2003) used by the ShakeMap system for M&<&5. The resulting equations predict median PGA and PGV values consistent with the Boore and Atkinson (2006) and Campbell and Borzorgnia (2006) NGA equations, which are valid for 5&<&M&<&8, at the larger magnitudes. There are discrepancies between the median ground motions predicted by the NGA relationships and our equations at M=5 level, which is the lower bound of the applicable magnitude range for the NGA equations. These discrepancies may be indicative of a systematic bias towards higher ground motion levels at the lower magnitude bound of the NGA equations. Our findings suggest that in order to develop prediction equations that adequately characterize the median ground motion behavior at a particular magnitude (for instance, the lower magnitude bound of M=5 for the NGA equations), a sufficient quantity of data from events with magnitudes lower than the targeted lower magnitude bound must be used to constrain the regressions.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting