Evaluation of Modified Frequency Dependent Equivalent Linear Method for Deconvolution Site Response Analysis

ABSTRACT

Frequency-dependent equivalent linear (FD-EQL) site response analysis methods, developed as potential substitutes for the EQL procedure to better simulate the nonlinear soil response, have been reported to overpredict the high-frequency wave propagation. Modified procedures proposed to overcome this limitation have demonstrated to improve the fits with the nonlinear analysis results. The method has not yet been applied to perform a deconvolution analysis, where a conventional EQL analysis often fails to converge or provide reliable estimate. The conventional EQL procedure and one of the modified FD-EQL method, which uses an empirical factor f to interpolate the strain spectrum between the EQL and FD-EQL outputs, are used to perform a series of deconvolution analyses using an idealized 1000 m profile and twelve Kik-net downhole arrays. The residuals of recorded and deconvoluted motions are shown to increase with strain for the EQL method even when using the recommended frequency cut-off. For the FD-EQL method, the range of f recommended for convolution analyses is shown to provide unrealistic responses in performing deconvolution analyses. A new range that produces unbiased residuals for all strain amplitudes is proposed. Comparisons highlight that the modified FD-EQL yields reliable predictions of the within motion for all profiles and motion intensities, automatically suppressing the amplification of high-frequency noise typically accompanied in a deconvolution analysis.

KEYWORDS:

• Frequency dependent equivalent linear method
• deconvolution site response analysis
• convolution site response analysis
• downhole array
• equivalent linear method
• cutoff frequency

Acknowledgments

This work was supported by the Ministry of Science and Technology in Taiwan, under Award No. MOST 108-2628-E-005 -001 -MY3. The authors gratefully acknowledge such support.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

The work was supported by the Institute for Information Industry, Ministry of Science and Technology, Taiwan [MOST 108-2628-E-005 -001 -MY3].