HR: 10:50h
AN: S31G-03 INVITED     [PDF]
TI: The Importance of "Time-Varying" Input for Probabilistic Seismic Hazard Assessment
AU: * Stirling, M W
EM: m.stirling@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30368, Lower Hutt, 0000 New Zealand
AU: Rudolph, T
EM: thessa@tormann.de
AF: Victoria University of Wellington, PO Box 600, Wellington, 0000 New Zealand
AU: Savage, M K
EM: martha.savage@vuw.ac.nz
AF: Victoria University of Wellington, PO Box 600, Wellington, 0000 New Zealand
AU: Gerstenberger, M
EM: matt@seismo.ifg.ethz.ch
AF: Institute of Geological & Nuclear Sciences, PO Box 30368, Lower Hutt, 0000 New Zealand
AB: The standard methods of modern probabilistic seismic hazard assessment (PSHA) typically assume a Poissonian (time-independent) model of earthquake occurrence. Input to Poissonian-based hazard estimates are simply the magnitudes and recurrence intervals of earthquakes on earthquake sources, allowing the PSHA to be computationally simple, and probably adequate for quantifying the long-term distribution of hazard in a region (e.g. peak and spectral accelerations expected with a 10% probability of exceedance in 50 years, equivalent to a 475 year return time). However, a serious deficiency in these standard methods of PSHA is that they ignore "time-varying" phenomena, such as the time elapsed since the last earthquake on an earthquake source, the association of foreshocks and aftershocks with a given mainshock, and interactions between the different earthquake sources in a region. Quantification of the influence of these factors on the Poissonian hazard estimates is especially important for estimating shorter-term hazard (i.e. time periods of tens of years or less), and significant efforts in recent years have focused on developing "time-varying" PSHAs that take these factors into account. We will show examples of PSHAs from New Zealand, USA and elsewhere to illustrate how "time-varying" hazard estimates differ from standard Poissonian estimates. For example, we observe a 30% increase in the peak ground acceleration expected along the Alpine Fault of New Zealand in a "time-varying" model over the standard Poissonian model, at the 10% probability of exceedance in 50 years level.
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting