HR: 0830h
AN: S21E-0348    [PDF]
TI: The Relation of the Grenville/Appalachian Boundary to the April 20, 2002 Au Sable Forks, New York and the April 29, 2003 Fort Payne, Alabama Earthquakes
AU: * Detweiler, S T
EM: shane@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: On April 20, 2002, an M=5.1 earthquake occurred near Au Sable Forks, New York at 10:50AM UTC (6:50AM locally). The significance of this event is twofold: first, such moderate earthquakes are relatively rare in this part of the North American continent, and second, the structure of the crust is well-known here because a major seismic investigation [Musacchio et al., 1997] took place before the Au Sable Forks event. That seismic survey derived detailed information about the deep subsurface, including the Champlain thrust fault, which was possibly the causative fault for this earthquake. The Champlain fault marks the local boundary between the Grenville and the Appalachian Provinces. On April 29, 2003 another event (M=4.6) occurred along the province boundary, this time in Fort Payne, Alabama. This second event is believed to have occurred on a nearly-vertical strike-slip fault. These two earthquakes are examples of the kind of temblors that the Grenville/Appalachian boundary is capable of producing, and we explore these events as they relate to seismic zones and background seismicity.
DE: 7205 Continental crust (1242)
DE: 7230 Seismicity and seismotectonics
DE: 8110 Continental tectonics--general (0905)
SC: Seismology [S]
MN: 2003 Fall Meeting