Deciphering the cause of massive disaster during sept. 2022 Chihshang Taiwan earthquake of magnitude 6.8 using strong motion seismology
Journal
Environmental Earth Sciences
Journal Volume
83
Journal Issue
17
ISSN
1866-6280
1866-6299
Date Issued
2024-08-29
Author(s)
Abstract
Between September 17 and 18, 2022, a series of earthquakes struck the southern Longitudinal Valley of Taiwan, causing severe damage to infrastructure, particularly bridges, railroads, buildings, and highways in Taitung and Hualien. The primary event in this sequence was the Chihshang earthquake, measuring magnitude of ML 6.9, preceded by a significant foreshock of ML 6.4 the day before. Notably, the highest intensity reported in the epicentral region during this earthquake sequence reached 6 +, marking the highest intensity ever recorded since the Central Weather Bureau (CWB) revised its seismic intensity scale. In this study, we examined the strong ground motion data recorded by the low-cost P-alert network to investigate the cause of structural damage to buildings, railway stations, schools, and other structures in the affected area. Our analysis encompassed data from a total of 17 monitoring stations. The observed peak ground acceleration (PGA) ranges from 0.06 g and 0.78 g, the peak spectral acceleration or response spectrum (PSA) spanned from 0.20 g at 0.50 s to 3.87 g at 0.41 s, and site amplification varied from 4 at 0.6 Hz to 12.6 at 5.2 Hz. The reported damage of single storey house at Taitung City is correlated with the higher amplification 4.5 at 0.14 s; Bridge and factory at Chihshang Township is correlated with the higher amplification 5 at 0.17 s; Railway station at Zhuoxi Township with the higher amplification 7.5 at 0.3 s; of three storey building at Yuli Township with amplification 8 at 0.26 s and, also higher PSA 2.83 g at 0.29 s, and several schools at Kaoshiung City with amplification 7.2 at 0.37 s and with high PSA 3.87 g at 0.41 s. Additionally, we studied the static Coulomb stress changes resulting from the coseismic slip of the main shock, which contributed to an increase in aftershock occurrences. The occurrence of a high-intensity earthquake (ML 6.9) on September 18, 2022, within a region of positive Coulomb stress changes, provides support for the hypothesis of aftershock triggering. Through analysis, we found that stronger foreshock (ML 6.4) occurred in the rupture area of mainshock foreshock, positioned adjacent to the main fault.
Subjects
Amplification
Coulomb Stress
PGA
PSA
Strong ground motion
SDGs
Publisher
Springer Science and Business Media LLC
Type
journal article