HR: 1340h
AN: S53B-1103    [Abstracts]
TI: Time-dependent Probabilistic Seismic Hazard Maps for Alaska
AU: * Boyd, O S
EM: olboyd@usgs.gov
AF: US Geological Survey, Geological Hazards Team MS 966, Box 25046 , Denver, CO 80225 United States
AB: We are currently revising the probabilistic seismic hazard maps of Alaska and the Aleutians. In addition to preparing time-independent hazard maps, we are preparing experimental maps including time-dependent earthquake probability estimates. The time-dependent maps consider various methods to implement time-dependent probability estimates based on Brownian Passage Time probability density functions. The methods require knowledge of the time of the last earthquake and the recurrence interval and its variability, as well as the assumption that the last earthquake reset the slip deficit. We apply time-dependent probabilities to those faults which have measured recurrence intervals and where the time of the last earthquake is known. We also investigate both elastic and viscoelastic stress transfer from regional large earthquakes on target faults as a means for influencing the time-dependent probabilities. The resulting stress changes vary along target faults and have necessitated modifications to our hazard calculation procedures that account for position-dependent probabilities. These modifications have also allowed us to account for position-dependent slip rates and provide for a straight forward way to cascade earthquakes. We find that time-dependent probabilities without stress transfer can lead to 100% reductions in probability on some faults while increasing others by more than a factor of two. This can dramatically change the resulting seismic hazard maps relative to time-independent seismic hazard maps. Elastic stress transfer can have a large but relatively short-lived effect on the probabilities while transient phenomena such as post-seismic afterslip and viscoelastic deformation can have larger and more long-lasting effects on earthquake probabilities.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7221 Paleoseismology (8036)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 9350 North America
SC: Seismology [S]
MN: Fall Meeting 2005