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Journal: |
Geophysical Research Letter 2017 No.44
clicks:313 |
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Title:
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Author:
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Victor C. Tsai, Daniel C. Bowden, Hiroo Kanamori |
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Adress: |
Seismological Laboratory, California Institute of Technology, Pasadena, California, USA |
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Abstract:
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Despite being 770 km away from the epicenter, observed ground motions due to the Tohoku earthquake in the Osaka Basin were unexpectedly large, with an amplification of more than a factor of 20 compared to immediately outside the basin, and including 2.7 m peak-to-peak roof displacements at one high-rise building. The local ground motions exceeded expectations based on standard computations of site response by a factor of 3, predicted frequencies of peak acceleration were off by at least 50%, and such discrepancies have not yet been explained quantitatively. Here we show that utilizing semianalytic theory for surface-wave amplification, we are able to accurately predict both the amplitudes and frequencies of large ground amplification in the Osaka Basin using only knowledge of the local one-dimensional structure. Comparison between this simple prediction and observed amplification was not expected to be so favorable and suggests that simple one-dimensional surface-wave site amplification factors can be useful in the absence of full three-dimensional wave propagation simulations. Such surface-wave amplification factors can be included in addition to the standard measures of site-specific site amplification and should help explain strong ground motion variability in future large earthquakes that shake Osaka Basin and elsewhere in the world. |
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Comment: |
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