HR: 0830h
AN: S41D-04    [Abstracts]
TI: Characteristics of Seismicity Triggered Remotely by the Mw7.9 Denali Fault Earthquake
AU: * MUKHERJEE, T
EM: tandrimals@yahoo.com
AF: TANDRIMA MUKHERJEE, Center for Earthquake Reseach and Information (CERI),University of Memphis,TN, MEMPHIS, TN 38152 United States
AU: BODIN, P
EM: pbodin@memphis.edu
AF: TANDRIMA MUKHERJEE, Center for Earthquake Reseach and Information (CERI),University of Memphis,TN, MEMPHIS, TN 38152 United States
AU: GOMBERG, J
EM: gomberg@ceri.memphis.edu
AF: JOAN GOMBERG, United States Geological Survey (USGS), Memphis, TN, MEMPHIS, TN 38152 United States
AB: Within seconds to minutes following the arrival of large surface waves from the Mw 7.9 Denali Fault earthquake an unusual number of small earthquakes took place near many seismic stations throughout the western US and Canada to distances exceeding 4000 km. These remotely triggered earthquake sequences persisted with Omori-like time-decaying occurrence rates for hours or days. At first glance, remotely triggered seismicity seems to behave like aftershocks, but instead of being initiated by a local mainshock the sequences are triggered by dynamic deformations of the distant large earthquake. They are difficult to study because many appear to be small, and take place when large scattered signals from the mainshock are still arriving. We study these triggered earthquakes by high-pass filtering broadband seismic recordings from a number of seismic stations in the western Cordillera, and we "calibrate" our single-station observations with data from seismicity catalogs from regional and local networks, where possible. We are seeking to determine whether the remotely triggered earthquakes are restricted to a particular type of tectonic environment and whether their temporal decay reflects "secondary" aftershocks of a rather large triggered earthquake. Or, alternatively do they represent a more "excited" state of faults more generally in the environments where they are observed to take place? Preliminary results suggest that both magmatically active and inactive (though faulted) environments were triggered, and that the triggered sequences are not simply secondary aftershocks.
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2005 Joint Assembly