Southwest (SW) Taiwan lies on the deformation front of a plate collision zone. Most earthquakes in this region occur due to deformation of the upper crust, therefore, potential seismic hazards in this area must be considered. On 6 February 2016, a moderate, but disastrous earthquake (M L = 6.6; depth = 14.6 km) occurred in Meinong, a district in the Kaohsiung area of Taiwan. This earthquake produced three cluster-like aftershocks. Among them, two of the aftershocks clusters were not spatially correlated with the main earthquake. Additionally, the trends of these two seismic clusters were not associated with previously known faults or geological structures. Therefore, our major intention is not only to investigate the rupture process of the 2016 Meinong earthquake, but more importantly, to look into the corresponding seismogenic process. In this research, high quality strong-motion data was used to invert the slip distribution on the fault plane using the isochron method. In addition, we relocated aftershocks to further obtain focal mechanisms using a 3D velocity model. Coulomb failure stress maps are calculated for different depth ranges based on the obtained source slip distribution to verify whether the main-shock triggers nearby unknown faults or not. In conclusion, we suggest that there might exist a NW-SE trending, north-dipping fault, which is located north of the source area and may have been triggered by the initial shock. We also conclude that the 2016 Meinong earthquake did trigger the pre-existing normal faults beneath Tainan City.

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The vigorous collision between the Eurasian plate and Philippine Sea plate in Taiwan causes a series of imbricate fold and thrust belts to develop at the deformation front. The Chukou Fault (CKF), characterized by a thrust type fault, located in Chiayi County, southwest (SW) Taiwan, is a prominent boundary between the fold-thrust belts and the Western Coastal Plain. Most of the seismicity in SW Taiwan is associated with this fault and its neighboring fault systems. The seismotectonic structures in the CKF zone, especially in the east, are complex due to the interactions among fault systems with distinct slip motions. To gain better insights into the seismogenic characteristics in the CKF zone, we used 1661 microearthquakes recorded by a temporary dense broadband seismic network and the Central Weather Bureau Seismic Network (CWBSN) between 2003 and 2004 to investigate the physical properties of the crust in the CKF zone. A waveform cross-correlation technique was applied to 143086 pairs of waveform data to determine the relative differential travel time between the P-and S-waves. By combining both the absolute and relative differential travel time data, we were able to obtain a new 3-D crustal P-wave velocity structure and V p /V s ratios. This study suggests that by using both absolute and relative differential travel time data in tomographic inversion can obtain precise 3-D velocity images and also gain better correlation between seismic events and fault structures, which is crucial for understanding the seismogenic process in our study area.

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The purpose of this paper is an analysis of features of the seismic regime before one of the strongest earthquake Taiwan in the twentieth century (Chi-Chi, 21.09.1999, Mw = 7.6). According to data for 1990-1999 variations of three parameters of the seismic regime were studied retrospectively: total annual number of earthquakes N Ʃ in the range of magnitudes of M L = 2.5-5.5, total annual quantity of released seismic energy ƩE, J and angular coefficient b of graphs of recurrence of earthquakes. There were chosen two obvious sub-periods in course the seismic regime -quiescence in 1990-1996 and activation in 1997-1999. Earthquake of Chi-Chi occurred on a maximum of seismic activity. The prevalence of weak earthquakes during of preparation the Chi-Chi earthquake caused an overestimation of coefficient b graphs of earthquake recurrence (-1.16 on average).