Location

San Diego, California

Session Start Date

5-24-2010

Session End Date

5-29-2010

Abstract

Surface wave analysis consists of generation, measurement and processing of the dispersive Rayleigh waves recorded from two or more vertical transducers. However, in case of soft clay soil, the reliable dispersion curve is difficult to be produced particularly at the frequency below 20 Hz. Some noises from nature and other human-made sources may disturb the generated surface wave data. In this paper, coupled analysis of continuous wavelet transform (CWT) spectrogram analysis based on Gaussian Derivative function was used to analyze the seismic waves in different frequency and time. First analysis is time-frequency wavelet spectrogram which was employed to localize the interested seismic response spectrum of generated surface waves. Second analysis is a time-frequency wavelet filtering approach which was used to remove noisy distortions in the spectrogram. Based on the generated spectrogram, the thresholds for wavelet filtering could be easily obtained. Consequently, the denoised signals of the seismic surface waves were able to be reconstructed by inverse wavelet transform considering the thresholds of the interested spectrum. Results showed that the CWT spectrogram analysis is able to determine and identify reliable surface wave spectrum and phase velocity dispersion curve of soft clay residual soil. This technique can be applied to problems related to non-stationary seismic wave.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fifth Conference

Publisher

Missouri University of Science and Technology

Publication Date

5-24-2010

Document Version

Final Version

Rights

© 2010 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 24th, 12:00 AM May 29th, 12:00 AM

Coupled CWT Spectrogram Analysis and Filtration: New Approach for Surface Wave Analysis (A Case Study on Soft Clay Site)

San Diego, California

Surface wave analysis consists of generation, measurement and processing of the dispersive Rayleigh waves recorded from two or more vertical transducers. However, in case of soft clay soil, the reliable dispersion curve is difficult to be produced particularly at the frequency below 20 Hz. Some noises from nature and other human-made sources may disturb the generated surface wave data. In this paper, coupled analysis of continuous wavelet transform (CWT) spectrogram analysis based on Gaussian Derivative function was used to analyze the seismic waves in different frequency and time. First analysis is time-frequency wavelet spectrogram which was employed to localize the interested seismic response spectrum of generated surface waves. Second analysis is a time-frequency wavelet filtering approach which was used to remove noisy distortions in the spectrogram. Based on the generated spectrogram, the thresholds for wavelet filtering could be easily obtained. Consequently, the denoised signals of the seismic surface waves were able to be reconstructed by inverse wavelet transform considering the thresholds of the interested spectrum. Results showed that the CWT spectrogram analysis is able to determine and identify reliable surface wave spectrum and phase velocity dispersion curve of soft clay residual soil. This technique can be applied to problems related to non-stationary seismic wave.