Hydrologically-Induced Crustal Stress Change and Its Association with Seismicity Rate in Taiwan
Abstract
Studying the influence of hydrological cycles on crustal stress changes and seismicity is crucial to disentangling the complex interplay between water-related processes and earthquakes. This study utilizes GNSS data to estimate annual vertical displacements and horizontal strain in response to seasonal water storage changes in Taiwan. The largest GNSS-inferred annual water-thickness change of 0.91 m occurs in SW Taiwan, where the region exhibits contraction and extension along a WNW-ESE trend in wet and dry months, respectively. The orientations of seasonally-varying strain axes are generally subparallel to the tectonic maximum principal stress axes. To assess the statistical correlation between hydrologically-induced stress changes and the timing of earthquake, we calculate the rate of excess earthquakes with respect to background seismicity for discrete stress intervals. We find a 20% increase in seismicity rate during the dry months when the tectonic maximum horizontal principal stresses and vertical stress are both reduced. The enhanced seismic activity in dry months manifests the dominant role of hydrologically-induced vertical stress changes, which are generally 5-10 times larger than the horizontal stress cycles. In SW Taiwan, the annual and interannual variability of seismicity rate exhibits an inverse correlation with hydrological loading and a positive correlation with GNSS annual vertical motion. This suggests a direct influence of elastic loading on seismicity rate. Probing the complex physical interactions between hydrological processes and seismic activity will advance our understanding of the earthquake faulting process and can help improve the assessment of earthquake hazard, which is especially important in regions with active tectonics and significant hydrological variability like Taiwan.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2023
- Bibcode:
- 2023AGUFM.G14A..07H