Shallow P- and S-wave velocities and site resonances in the St. Louis region, Missouri-Illinois

Williams, R. A.; Odum, J. K.; Stephenson, W. J.; Herrmann, R. B.

Abstract:

As part of the seismic hazard-mapping efforts in the St. Louis metropolitan area we determined the compressional and shear-wave velocities (Vp and Vs) to about a 40-m depth at 17 locations in this area. The Vs measurements were made using high-resolution seismic refraction and reflection methods. We find a clear difference in the Vs profiles between sites located on the river floodplains and those located in the upland urban areas of St. Louis. Vs30 (average Vs to 30-m depth) values in floodplain areas range from 200 to 290 m/s (NEHRP category D) and contrast with sites on the upland areas of St. Louis, which have Vs30 values ranging from 410 to 785 m/s (NEHRP categories C and B). The lower Vs30 values and earthquake recordings in the floodplains suggest a greater potential for stronger and more prolonged ground shaking in an earthquake. Spectral analysis of a M3.6 earthquake recorded on the St. Louis-area ANSS seismograph network indicates stronger shaking and potentially damaging S-wave resonant frequencies at NEHRP category D sites compared to ground motions at a rock site located on the Saint Louis University campus. ?? 2007, Earthquake Engineering Research Institute.

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Article

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70030965

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Williams, R. A.; Odum, J. K.; Stephenson, W. J.; Herrmann, R. B.

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726

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English

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Earthquake Spectra

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Shallow P- and S-wave velocities and site resonances in the St. Louis region, Missouri-Illinois; 2007; Article; Journal; Earthquake Spectra; Williams, R. A.; Odum, J. K.; Stephenson, W. J.; Herrmann, R. B.