Triggered Seismicity in Utah from the 3 November 2002 Denali Fault Earthquake

摘要: Immediately after the arrival of surface waves from M w 7.9 Denali fault earthquake on 3 November 2002, University Utah regional seismic network recorded an abrupt increase in local microseismicity throughout most Utah’s main belt. We examined this context background seismicity using a catalog 2651 earthquakes 1 January 2000 to 30 June 2003. Statistical analyses above spatially varying magnitudes completeness ranging 1.2 1.7 allow us reject with >95% confidence null hypothesis that observed increases were due random occurrence. The elevated was intense during first 24 hr (>10 times average prior rate) but continued level for 25 days (at 95% level) areas. conclude increased triggered by earthquake, which occurred more than 3000 km study region. High peak dynamic stresses 0.12 0.35 MPa passage Love are consistent interpretation triggering. estimated measuring vector velocities at 43 recording sites, 37 relatively new strong-motion stations Advanced National Seismic System. The events ranged magnitude ( c and/or L) less 0 3.2 and widely distributed across state, primarily seismically active regions. In contrast many previously published observations remotely seismicity, majority did not occur near Quaternary volcanic vents or areas magma-related geothermal activity. several clustered (more five each separated <5 km). Double-difference relative relocations three these clusters indicate most, all, source zones 2000–2002. Focal mechanisms two largest have northeast- northwest-trending tension axes, unusual region where they occurred. temporal decay activity similar aftershock sequences can be described modified Omori’s law p -value 0.6 0.7. frequency-magnitude distribution is also aftershocks and, area as whole, Gutenberg-Richter relation b 0.81 ± 0.16. These similarities between suggest possibility initiation development both could result same causative mechanisms. Online Material : Catalog used study.