Abstract

This study used ambient vibration data collected during a reconnaissance mission to assess whether harmonics between structures and the underlying soil played a significant role in the pattern of buildings that collapsed in the magnitude 7.5 Noto Japan earthquake on January 1, 2024, and the magnitude 6.2 to 7.0 Kumamoto Japan earthquake series that occurred between April 14 and 16, 2016. Portable seismometers were used to measure the natural soil and structural frequencies of vibration under ambient loading at sites in Wajima, a city located on the Noto Peninsula, and in four locations in and around Kumamoto City. Soil frequency was determined based on the geophysical horizontal-to-vertical spectral ratio (HVSR). Where building access was permitted, structure frequency was determined based on the single-sided amplitude (power) spectrum. Where building access was not permitted, structure frequency was estimated based on local construction and the shear stiffness of the lateral system. The hypothesis is that sites where the half-power bandwidth of the soil spectrum overlapped with the frequency band of the structure aligns with buildings that collapsed. Results showed that soil-structure harmonics under ambient vibration was well matched with the collapse pattern of mid-rise reinforced concrete buildings, but there was less correlation with the collapse pattern of low-rise (residential) wood-frame buildings. The findings in this study suggest that portable seismometers and response spectra based on ambient vibration can be valuable tools and techniques for rapidly identifying sites where soil-structural harmonics could lead to significant structural damage during a major earthquake.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Civil and Construction Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-04-22

Document Type

Thesis

Keywords

resonance, seismic performance, HVSR, power spectra, risk analysis, Japan, Kumamoto, Noto, engineering, structural engineering, civil engineering

Language

english

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