Journal: |
Geophysical Journal International 2018 No.2
clicks:298 |
Title:
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Author:
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Qifang Liu |
Adress: |
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Abstract:
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We perform full elastic wavefield simulations of Weihe basin during the
great Wenchuan earthquake using a 3-D spectral element method. The 3-D basin
model, including Quaternary and Tertiary layers, is constructed based on the
drilling well data and seismic profile data. The source model of Wenchuan
earthquake was inversed using the far-field P waves by non-negative
linear least-squares inversion method. We validated the source, crustal and
basin models by comparing synthetic and observed records of three-component
displacements at 28 stations distributed within and at the edge of the basin.
Results indicated that direct surface waves incident to the basin were trapped
and rebounded obviously at the two deepest bowls where the Quaternary
thicknesses are >1000 m, with shaking duration of large-amplitude
ground motion about 50–100 s longer than that outside the basin. The southern
steep basin boundary induced noteworthy large-amplitude surface wave,
propagating and reflecting in the basin, which increased the wave amplitude and
prolonged the shaking duration. The basin produced remarkable amplification in
frequency range 0.125–0.175 Hz by a factor of about 6–10, attributed to
the reverberation of the deepest part of sediment within the basin. The
amplification of basin is coherent to the Quaternary thickness, with deep
Quaternary sediment corresponded to the large-amplitude and long-duration
ground motion. |
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