HR: 1340h
AN: S23B-0247    [Abstracts]
TI: Earthquake Source Scaling and Wave Propagation in Eastern North America: The Au Sable Forks, NY, Earthquake
AU: * Viegas, G
EM: gmvf@bu.edu
AF: Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, MA 02215 United States
AU: Abercrombie, R
EM: rea@bu.edu
AF: Department of Earth Sciences, Boston University, 685 Commonwealth Avenue, Boston, MA 02215 United States
AU: Baise, L
EM: laurie.baise@tufts.edu
AF: Tufts University, Civil and Environmental Engineering, Medford, MA 02155 United States
AU: Kim, W
EM: wykim@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964 United States
AB: The 2002, M5 Au Sable Forks, NY earthquake and aftershocks are the best recorded sequence in the North Eastern USA. We use the local and regional recordings to investigate the characteristics of intraplate seismicity, focusing on source scaling relationships and regional wave propagation. A portable local network of 11 stations, recorded 74 aftershocks of M<3.2. We relocate the mainshock and early aftershocks using a master event technique. We then use the double-difference relocation method using differential travel times measured from waveform cross-correlation to relocate the aftershocks recorded by the local network. Both the master-event and double-difference location methods produce consistent results suggesting complex conjugate faulting during the sequence. We identify a number of highly clustered groups of earthquakes suitable for EGF analysis. We use the EGF method to calculate the stress drop and radiated energy of the larger aftershocks to determine how they compare to moderate magnitude earthquakes, and also whether they differ significantly from interplate earthquakes. We consider the 9 largest aftershocks (M3.7 to M2), which were recorded on the regional network, as potential EGFs for the mainshock, but they have focal mechanisms and locations that are sufficiently different that we cannot resolve the mainshock source time function well. They are good enough to enable us to place constraints on the shape and duration of the source pulse to use in modeling the regional waveforms. We investigate the crustal structure in New York (Grenville) and New England (Appalachian) through forward modeling of the Au Sable Forks regional broadband records. We compute synthetic records of wave propagation in a layered medium, using published crustal models of the two regions as a starting point. We identify differences between the recorded data and synthetics for the Grenville and the Appalachian regions and improve the crustal models to better fit the recorded waveforms.
DE: 7205 Continental crust (1219)
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: Fall Meeting 2005