Monitoring of Crustal Activities in the Yun-Chia-Nan area of Taiwan

Monitoring of Crustal Activities in the Yun-Chia-Nan area of Taiwan

The physical properties of the crust exhibit variation due to the effect of tectonic stress. In particular, before and after strong earthquakes, the relevant physical parameters(velocity, attenuation) produce a change that has been discussed in numerous studies. After a strong earthquake, the rupture can cause rock fragmentation and lead to pore fluid migration or filling and this phenomenon can be observed by analyzing the seismic wave propagation. Therefore, this study uses small earthquakes to calculate seismic crustal attenuation parameters. The variation in physical parameters can confirm the correlation between the observed data and the occurrence of earthquakes, and assess changes in the regional stress state. When a seismic wave propagates, the geometric spreading and anelastic absorption affect the amplitude, and related factors that include the rock porosity, lithology, temperature and pressure conditions, rock particle size, viscosity, and saturation. Hence, this study proposes monitoring of the crust, which exhibits temporal variations in lithology and fluid conditions under tectonic stress before an earthquake. Through the use of high-quality seismic waveform data and dispersive attenuation analysis, we can resolve temporal changes in media and assess the regional seismogenic processes.