HR: 17:15h
AN: S12E-05    [PDF]
TI: Issues in Evaluating Seismic Hazards in the Basin and Range Province: An Example From Yucca Mountain
AU: * Wong, I G
EM: ivan_wong@urscorp.com
AF: URS Corporation, 500 12th Street, Suite 200, Oakland, CA 94607 United States
AU: Stepp, J C
EM: cstepp@moment.net
AF: URS Corporation, 871 Chimney Valley Road, Blanco, TX 78606 United States
AU: Whitney, J
EM: jwhitney@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center, MS 980, Denver, CO 80225 United States
AU: Quittmeyer, R
EM: richard_quittmeyer@ymp.gov
AF: ISSI, 1180 Town Center Drive, MS 423, Las Vegas, NV 89144 United States
AU: Abrahamson, N
EM: naa3@pge.net
AF: Consultant, 152 Darcena Avenue, Piedmont, CA 94611 United States
AU: Robert, R
EM: byoungs@geomatrix.com
AF: Geomatrix Consultants, Inc., 2101 Webster Street, 12th Floor, Oakland, CA 94612 United States
AU: Coppersmith, K
EM: kevin@coppersmithconsulting.com
AF: Geomatrix Consultants, Inc., 2121 North California Blvd., Suite 290, Walnut Creek, CA 94596 United States
AU: Toro, G
EM: toro@riskeng.com
AF: Risk Engineering, Inc., 3 Farmers Row, Acton, MA 01720 United States
AB: Evaluating seismic hazards in the Basin and Range Province poses significant challenges due, in large part, to an inadequate empirical database. Despite a dramatic increase in paleoseismic investigations of Basin and Range faults in the past decade, long inter-event times, limitations associated with age-dating, and geologic, financial, and physical constraints in excavating the necessary deep paleoseismic trenches have hindered our ability to decipher the seismic cycles along the vast majority of Basin and Range faults. The almost nonexistent strong motion database also poses challenges in characterizing strong earthquake ground motions. Due to an intensive program of seismic hazard-related investigations and seismic monitoring, particularly in the past 10 years, Yucca Mountain, the site of the first U.S. underground nuclear waste repository has become the most analyzed site in the Basin and Range Province. These studies culminated in an expert judgment probabilistic seismic hazard analysis (PSHA) for ground motion and fault displacement. Despite the relative abundance of seismological and paleoseismic data, the ranges of expert interpretations and uncertainties in characterizing the earthquake potential of Quaternary faults and ground motion estimation were still very significant. Significant seismic source issues included: (1) the role of planar block faulting versus detachment faults; (2) the seismogenic potential of listric and detachment faults; (3) rupture models for closely-spaced faults both along strike and downdip; (4) identification and characterization of multiple fault segment ruptures; (5) depth of seismogenic faults and rupture in large events; (6) recurrence models for faults; (7) the role of Walker Lane-style shear deformation; and (8) approaches to addressing the hazard from "background" earthquakes. Issues in characterizing ground motion estimation included: (1) whether ground motions in extensional regimes are smaller than in compressional regimes (e.g., California) possibly due to lower earthquake stress drops; (2) hanging wall versus footwall effects; (3) ground motions from multiple parallel faults and detachment faults; and (4) the value of the near-surface attenuation parameter kappa. How these issues were addressed by the PSHA experts and their relative significance to the seismic hazard at Yucca Mountain are presented.
DE: 7212 Earthquake ground motions and engineering
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting