Document Type
Conference Paper
Publication Date
2024
Publication Title
18th World Conference on Earthquake Engineering (WCEE2024)
Volume
2024
Pages
1-12
Conference Name
18th World Conference on Earthquake Engineering (WCEE2024), June 30-July 5, 2024, Milan, Italy
Abstract
Microtremor horizontal-to-vertical spectral ratios (mHVSR) are frequency-dependent ratios of Fourier amplitude spectra of the horizontal to vertical components of a 3-component recording of ambient ground motions from microtremors. Results from mHVSR tests can identify the frequencies associated with site resonances at sites with large impedance contrasts, and hence have potential to provide useful parameters for predicting seismic site response. Site measurements are made by recording ground vibrations either from a temporarily deployed seismometer, typically recording for a relatively short period of time (~1-2 hrs.), or from a permanently-installed broadband seismometer. In this paper, we discuss ongoing work investigating the reliability of low frequency (< ∼0.1 Hz) mHVSR ordinates. Such low frequency ordinates are potentially useful for sites that are known to have deep basins (e.g., LA Basin, Imperial Valley, Great Salt Lake basin), where fundamental frequencies may fall in this range and direct measurements of depth to bedrock are difficult to make. We have found that low-frequency mHVSR ordinates (< ∼0.1-0.2 Hz) are for practical purposes not reliable in most cases, even when measured by high-quality temporary or permanent broadband sensors. In this paper, we discuss sensor drift and its limited impact on the reliability of mHVSR ordinates. We document the low frequency problem for multiple sites, although we do not have a solution as of this writing for how to improve the reliability of low-frequency results.
Rights
© 2024 International Association for Earthquake Engineering and the authors.
Posted with the kind written permission of IAEE and the author.
ORCID
0000-0002-2844-4557 (Wang)
Original Publication Citation
Ornelas, F. J., Nweke, C. C., de la Torre, C. A., Wang, P., Mai, T. D., Cox, B. R., Brandenberg, S. J., & Stewart, J. P. (2024, June 30-July 5). Reliability of low frequency mHVSR ordinates [paper presentation]. 18th World Conference on Earthquake Engineering (WCEE2024), Milan, Italy.
Repository Citation
Ornelas, F. J.; Nweke, C. C.; de la Torre, C. A.; Wang, P.; Mai, T. D.; Cox, B. R.; Brandenberg, S. J.; and Stewart, J. P., "Reliability of Low Frequency mHVSR Ordinates" (2024). Civil & Environmental Engineering Faculty Publications. 124.
https://digitalcommons.odu.edu/cee_fac_pubs/124