1. Improved site-dependent statistical relationships of VS and resonant frequency versus bedrock depth in Japan
- Author
-
Mostafa Thabet
- Subjects
Combinatorics ,geography ,Geophysics ,geography.geographical_feature_category ,Site dependent ,Spectral ratio ,Geochemistry and Petrology ,Bedrock ,Nonlinear regression ,Seismology ,Mathematics - Abstract
Combining both processing techniques of horizontal-to-vertical spectral ratio (HVSR) and surface-to-borehole spectral ratio (SBR), using the KiK-net and K-NET database in Japan, could be used in the present study to establish relationships of VS and resonant frequency ( $$f$$ ) versus depth to bedrock half-space ( $$h$$ ) based on the site-dependent variability. Remarkable correlations of the average $${V}_{s}$$ of layers overlying the bedrock half-space ( $$\overline{{V }_{S}}$$ ) versus $$h$$ are inversely resembling those of the $$f$$ versus $$h$$ . The maximum $$\overline{{V }_{S}}$$ values are 1262 m/s, 933 m/s, 842 m/s, and 568 m/s through site class of B, C, D, and E, respectively. These values of $$\overline{{V }_{S}}$$ are decreasing gradually resembling the $${V}_{s30}$$ through site class of B, C, D, and E according to (NEHRP, Report FEMA 368, NEHRP, Washington, 2000). The $$f$$ versus $$h$$ regressions at KiK-net sites yield gradual decrease in the correlation coefficients (i.e., a and b) through site class of B, C, D, and E, particularly the resulted a and b from SBR technique. K-NET sites yield significant lower correlation coefficients, which could be attributed to the K-NET shallow depths ( $$h$$ ) and their corresponding limited ranges of ( $$f$$ ). Although such relationships are site-specific and highly dependent on each region’s geologic conditions, fair comparisons based on site information and site-dependent variability between previous relationships of $$f$$ versus $$h$$ in the literature and the present study relationships are showing remarkable similarities. This indicates significant importance of introducing the seismic site classification as a crucial controlling factor in establishing the previous and the present $${V}_{s}$$ and $$f$$ versus $$h$$ nonlinear regression relationships.
- Published
- 2021
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