Seismic attenuation structure of the Seattle Basin, Washington State from explosive-source refraction data

Li, Q.; Wilcock, W. S. D.; Pratt, T. L.; Snelson, C. M.; Brocher, T. M.

Abstract:

We used waveform data from the 1999 SHIPS (Seismic Hazard Investigation of Puget Sound) seismic refraction experiment to constrain the attenuation structure of the Seattle basin, Washington State. We inverted the spectral amplitudes of compressional- and shear-wave arrivals for source spectra, site responses, and one- and two-dimensional Q-1 models at frequencies between 1 and 40 Hz for P waves and 1 and 10 Hz for S waves. We also obtained Q-1 models from t* values calculated from the spectral slopes of P waves between 10 and 40 Hz. One-dimensional inversions show that Qp at the surface is 22 at 1 Hz, 130 at 5 Hz, and 390 at 20 Hz. The corresponding values at 18 km depth are 100, 440, and 1900. Qs at the surface is 16 and 160 at 1 Hz and 8 Hz, respectively, increasing to 80 and 500 at 18 km depth. The t* inversion yields a Qp model that is consistent with the amplitude inversions at 20 and 30 Hz. The basin geometry is clearly resolved in the t* inversion, but the amplitude inversions only imaged the basin structure after removing anomalously high-amplitude shots near Seattle. When these shots are removed, we infer that Q-1 values may be ???30% higher in the center of the basin than the one-dimensional models predict. We infer that seismic attenuation in the Seattle basin will significantly reduce ground motions at frequencies at and above 1 Hz, partially countering amplification effects within the basin.

Genre:

Article

ProdID:

70030276

Citation Author:

Li, Q.; Wilcock, W. S. D.; Pratt, T. L.; Snelson, C. M.; Brocher, T. M.

Citation Contributing Office:

Citation Datum:

Citation Day:

Citation Edition:

Citation Editor:

Citation End Page:

571

Citation Issue:

Citation Keywords:

Citation Language:

English

Citation Larger Work Title:

Bulletin of the Seismological Society of America

Citation LatN:

Citation LatS:

Citation LonE:

Citation LonW:

Citation Month:

Citation No Pagination:

Citation Number Of Pages:

Citation Online Only Flag:

Citation Phsyical Description:

Citation Projection:

Citation Public Comments:

Citation Publisher:

Citation Series:

Citation Series Code:

Citation Series Number:

Citation Search Results Text:

Seismic attenuation structure of the Seattle Basin, Washington State from explosive-source refraction data; 2006; Article; Journal; Bulletin of the Seismological Society of America; Li, Q.; Wilcock, W. S. D.; Pratt, T. L.; Snelson, C. M.; Brocher, T. M.