Document Type

Conference Paper

Publication Date

2024

Publication Title

18th World Conference on Earthquake Engineering (WCEE2024)

Pages

1-4

Conference Name

18th World Conference on Earthquake Engineering (WCEE2024), June 30-July 5, 2024, Milan, Italy

Abstract

Site response describes the alterations of seismic energy due to its interaction with subsurface geological interfaces and structures, which is usually estimated by one dimensional (1D) ground response analysis (GRA). However, 1D GRA requires subsurface information (e.g., shear wave velocity profile), which makes it not widely applicable, particularly for the sites where subsurface information is unavailable. Alternatively, the microtremor horizontal-to-vertical spectral ratio (mHVSR) from three-component recordings of ambient noise on the ground surface is easily measured and is believed to have the potential for site response prediction (the peaks in mHVSR are strongly associated with the site resonant frequencies). However,the mHVSR ordinates at frequencies lower than 0.3 Hz are accompanied by high variability stemming from the issues in data collection, processing, and interpretation. This primarily manifests as an inconsistent description of resonant ordinates (magnitude of amplitude and existence of peaks). In this study, we investigated the reliability of low-frequency peaks in mHVSR by comparing them with the results from 1D linear GRA. We collected mHVSR (followed by the recommended SESAME guideline) for two and a half days at a site on the University of Southern California campus in the Los Angeles basin. We also extracted the shear wave velocity profile (about 12 km deep with the bottom most Vs = 3,600 m/s) from an established community velocity model for the site and ran 1D linear GRA. The result shows the fundamental site frequency is below 0.1 Hz (about 0.09 Hz). In mHVSR curves, the variability of ordinates increases as the frequency decreases (a significant increase below 0.2 Hz). Nevertheless, a peak below 0.1 Hz (about 0.05 Hz) presents in mHVSR, although the peak is not perfectly aligned with the peak location in the 1D GRA result. This study indicates that even with large variability, mHVSR has the potential to extract fundamental site frequency for deep basins by low-frequency peaks.

Rights

© 2024 The authors and IAEE.

Posted with the kind written permission of IAEE and the Author.

ORCID

0000-0002-2844-4557 (Wang)

Original Publication Citation

Mai, T., Nweke, C. C., Wang, P., & Ornelas, F. J. (2024, June 30-July 5). Investigating the viability of low frequency mHVSR estimates using shear wave velocity profile [Paper presentation]. 18th World Conference on Earthquake Engineering (WCEE2024), Milan, Italy.

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