HR: 09:00h
AN: NS21A-05    [Abstracts]
TI: A Microtremor Study in the New Madrid Seismic Zone
AU: * Hardesty, K
EM: geokelli@yahoo.com
AF: Auburn University Department of Geology, 210 Petrie Hall, Auburn, AL 36849-5305, United States
AU: Wolf, L
EM: wolflor@auburn.edu
AF: Auburn University Department of Geology, 210 Petrie Hall, Auburn, AL 36849-5305, United States
AU: Bodin, P
EM: bodin@u.washington.edu
AF: Earth and Space Sciences University of Washington, Johnson Hall 070 Box 351310 4000 15th Avenue NE, Seattle, WA 98195-1310, United States
AB: We present results of a microtremor study in the New Madrid seismic zone (NMSZ). The study utilizes Nakamura's method to investigate horizontal to vertical (H/V) spectral ratios across the central Mississippi embayment, in areas that experienced strong ground shaking and widespread soil liquefaction during the 1811 and 1812 earthquake sequence. Results from 20 sites show that embayment thicknesses ranging from 100 to 200 m and 500 to 900 m have fundamental periods ranging from 1.5 to 1.9 s and 3.0 to 4.1 s, respectively. The average shear-wave velocities for these two stratigraphic intervals are calculated at 325 m/s and 830 m/s, respectively. Most pronounced in the frequency spectra are peaks associated with a strong impedance contrast at the interface between embayment sediments and underlying basement rocks, which deepen towards the central embayment and to the south. The impedance contrast coupled with the basin configuration could contribute significantly to wave amplification at these fundamental periods. These results are consistent with similar studies conducted in other areas of the seismic zone.
DE: 7212 Earthquake ground motions and engineering seismology
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting