Sen Xie's research while affiliated with Krirk University and other places

This study aims to assess the structural damages caused by the potential Changhua earthquake (M L 7.0). The hybrid broadband waveform is employed to simulate the strong motions in Changhua County at first, and the modal analysis method is then used to estimate two significant parameters, the roof story drift ratio (RDR) and maximum inter-story drift ratio (MIDR), to correlate the damages of the buildings with 4-story frames. To validate the corrects of the relationship between the parameters and injuries of the structures, we use the 1999 Chi-Chi earthquake (M L 7.3), which is the largest earthquake that occurred in central Taiwan, and the 2016 Meinong earthquake (M L 6.6) as two real examples in the theoretical tests. According to the results of the tests, 90 percent of the damaged buildings with 1~4 floors are located in places with RDR values greater than 0.035 and MIDR values greater than 0.04, respectively. The results represent the thresholds of RDR and MIDR, which are 0.035 and 0.04, consistent with the tables in Hazus (2001). Based on the theoretical tests, the assessment of the buildings damaged by a potential Changhua earthquake (M L 7.0), which occurred on Feb. 12, 1848, due to the Changhua fault's movement, is evaluated. The hybrid simulation method and modal analysis are employed to calculate the distributions of RDR and MIDR caused by the potential Changhua earthquake in Changhua County. Results of the research indicate that most of the buildings with 1~4 floors in Changhua County may be destroyed seriously, especially for the buildings in the populated areas such as Changhua and Yuanlin cities and Xianxi, Lukang townships which can cause considerable damage over large areas. Establishing rescue and relief joint coordination mechanisms is the most crucial work to reduce the destructiveness of the potential earthquake disaster.

This research aims to evaluate the probability distribution of landslides triggered by a potential earthquake. Based on the evaluations, successive disaster prevention and mitigation can be well-prepared in advance. Deriving the critical acceleration value depends on the geometry and strength of the material on the slope. Thus, the Newmark's displacement of slope can be determined using the critical acceleration and strong motion recording of an earthquake. A threshold value of Newmark's displacement is assumed as 5cm, which means a landslide may occur if Newmark's displacement is greater than it. To identify the feasibility, we synthesize two waveforms of the 1999 Chi-Chi earthquake (M w 7.6) and one for the 2013 Nantou earthquake (M w 6.2) to compute the Newmark's displacements at Jiou-Jiou Peaks and Shinyi town in Nantou County, Taiwan by using the stochastic semi-empirical technique. The Newmark's displacements are 9.75 averaged and 6cm respectively, which are coincident with the earthquake-triggered landslides occurring actually. By counting accumulations of Coulomb's stress changes of Nantou earthquakes in 2013 in central Taiwan, we predict the epicenter of a potential earthquake. The regression relation between critical acceleration with Arias intensity of the seismic waveform is employed to calculate Newmark's displacements in the Nontou County. Accompanied by Newmark's displacement, the empirical probabilities of earthquake-induced landslides are derived. Accordingly, there are four populated densely areas with higher Newmark's displacements and probabilities, indicating that high landslide risk is existing potentially in these areas and the corresponding disaster prevention management and mitigation must be carefully regulated.

The kinematic source rupture process of the 2016 Meinong earthquake (Mw = 6.4) in Taiwan was derived from apparent source time functions retrieved from teleseismic S-waves by using a refined homomorphic deconvolution method. The total duration of the rupture process was approximately 15 s, and one slip-concentrated area can be represented as the source model based on images representing static slip distribution. The rupture process began in a down-dip direction from the fault toward Tainan City, strongly suggesting that the rupture had a unilateral northwestern direction. The asperity with an area of approximately 15 × 15 km2 and the maximum slip of approximately 2 m were centered 12.8 km northwest of the hypocenter. Coseismic vertical deformation was calculated based on the source model. Compared with the results derived from InSAR (Interferometric Synthetic Aperture Radar) data, our results demonstrated that the location with maximum uplift was accurately well detected, but our maximum value was just approximately 0.4 times of the InSAR-derived value. It reveals that there are the other mechanisms to affect the vertical deformation, rather than only depending on the source model. At different depths, areas west, east, and north of the hypocenter maintained high values of Coulomb stress changes. This explains the mechanism behind aftershocks being triggered and provides a reference for predicting aftershock locations after a large earthquake. The estimated seismic spectral intensities, including spectral acceleration and velocity intensity (SIa and SIv), were derived. Source directivity effects caused damage to buildings, and we concluded that all damaged buildings were located within a SIa value of 400 gal. Destroyed buildings taller than seven floors were located in an area with a SIv value of 30 cm/s. These observations agree with those on damages caused by the 2010 Jiasian earthquake (ML 6.4) in Tainan, Taiwan.

The earthquake (M L 5.2) which occurred at Chushan town, Nantou on Nov.11, 2017 resulted many aftershocks around the hypocenter of the mainshock. The coulomb stress changes (∆CFSs) by the mainshock demonstrated by most of the aftershocks located within the portions with ∆CFSs greater than 0.1 bar, revealing the aftershocks may be induced by the mainshock. After investigating the ∆CFSs at different depths, the results showed most of ∆CFSs with positive values under depth 15km were transferred to the southeast and southwest regions. About ten days later, there were many earthquakes (M L 5.2~3) with depth below 15km clustered exactly in the southeast region. The southwest region near the Meishan fault, caused large earthquake with M L 7.0 before 110 years ago. This means the Meishan fault may be triggered by the successive earthquakes near the fault. Based on the seismic spectrum intensities, the seismic hazards by the potential Meishan earthquake are estimated. The maximum seismic intensities will occur at Chushan township and the segment of freeway 3 connecting Nantou city and Chushan township may be damaged seriously. The landslides may happen again at the junctions of Nantou and Yunlin counties, where great landslides happened when Chi-Chi earthquake (M L 7.3) occurred in 1999.

The kinematics rupture process of the Chia-Yi earthquake occurred on October 22, 1999 (Mw 5.9) in Taiwan is investigated. The hybrid blind deconvolution technique is applied to the teleseismic waves to invert source parameters, including slip amplitudes, rise times and rupture velocities on the fault. From the directivity effect of the fault, the actual fault plane is determined as east dipping. According to the derived ASFT, the total duration of the rupture process is 6.5 sec. A good correlation notices that the larger slip amplitude corresponds to the longer rise time of the subfault. By using the inverted source parameters and combining the stochastic method for finite fault, the strong ground motions of 12 stations at epicentral distances ranging from 3.28 to 29 km are simulated. The results show that the agreements between simulated and recorded spectra are quite satisfying. It means that the inverted source parameters are reliable and the stations where located at near source distance are dominated by source effects. The inhomogeneous distribution of slip and the variable corner frequency could play important roles in the simulation process. Although the source effects are dominant, there are some significant discrepancies existing at stations, implying the site effects are influential.