HR: 0830h
AN: S21F-0390    [PDF]
TI: New, High Resolution, Three-Dimensional Velocity Models for the New Madrid Seismic Zone
AU: * Vlahovic, G
EM: vlahovic@email.unc.edu
AF: Department of Geography and Earth Sciences, North Carolina Central University, Durham, NC 27707 United States
AU: Powell, C
EM: powell@ceri.memphis.edu
AF: Center for Earthquake Research and Information, University of Memphis 3876 Central Ave Ste 1, Memphis, TN 38152 United States
AU: Withers, M
EM: withers@ceri.memphis.edu
AF: Center for Earthquake Research and Information, University of Memphis 3876 Central Ave Ste 1, Memphis, TN 38152 United States
AB: We are developing high resolution three-dimensional P and S wave velocity models for the New Madrid seismic zone (NMSZ) using arrival times recorded by the 90 station New Madrid seismic network operated by the Center for Earthquake Research and Information. The new velocity models will be much more detailed than prior velocity images produced by inverting arrival times recorded by the 40 station PANDA array and will be the first models produced for the southwest portion of the NMSZ. The new models will use arrival times associated with 1,100 earthquakes recorded from 1995 until mid 2003. This data set comprises roughly 25,000 P and S wave arrivals. Previous three-dimensional velocity models determined using PANDA data imaged high velocity regions interpreted to be mafic intrusions along the axis and edges of the Reelfoot rift. Hypocenters in the depth range 4 to 10 km in the NW trending central arm of seismicity occur along the borders of the mafic intrusions. A region of low shear wave velocity was imaged at the SE end of the central arm of seismicity and was attributed to the presence of highly fractured, fluid saturated crust. This region is characterized by a high earthquake swarm rate and shallower than normal seismicity. The new velocity models will provide increased resolution along the NW trending central arm of seismicity and will help illuminate the relationship between earthquake activity and velocity perturbations. In particular, the apparent association of earthquakes and mafic intrusions will be thoroughly investigated. The station configuration will allow detailed velocity models to be constructed for the SW trending arm of seismicity; these models may provide insight into why seismicity terminates near Marked Tree, Arkansas.
DE: 7205 Continental crust (1242)
DE: 7230 Seismicity and seismotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting