Fault Orientation Determination for the 4 March 2008 Taoyuan Earthquake from Dense Near-Source Seismic Observations

Abstract

On 4 March 2008, a moderate earthquake (M L = 5.2) occurred in southern Taiwan and named as the Taoyuan earthquake, preceded by foreshocks and followed by numerous aftershocks. This earthquake sequence occurred during the TAIGER (TAiwan Integrated GEodynamics Research) controlled-source seismic experiment. Consequently, several seismic networks were deployed in the Taiwan area at this time and many stations recorded this earthquake sequence in the near-source region. We archived and processed near-source observations to determine the fault orientation. To locate the events more accurately, station corrections, waveform cross-correlation to pick seismic phases, and a double-difference earthquake location algorithm were used to compute earthquake hypocenters. Over a 50-hour recording period, beginning half an hour before the start of the main shock, 2340 events were identified within the earthquake sequence. The identified aftershocks reveal a clear fault plane with a strike of N37°E and a dip of 45°SE. This plane corresponds to one of the focal mechanism nodal planes determined by the Broadband Array in Taiwan for Seismology (BATS) (strike = 37°, dip = 48°, and rake = 96°). Based on the main shock focal mechanism, the aftershock distribution, and the regional geological reports, we suggest that faulting on the northern extension of the major regional active fault, the Chishan Fault, caused the Taoyuan earthquake sequence.

Evaluating the Association Between Tectonic Tremors and Earthquakes in Taiwan From 7 Years Catalogs

“…The coseismic slip models for 2008 Taoyuan, 2010 Jiashian, 2012 Wutai, and 2016 Meinong mainshocks were derived from Shih et al (), Lee et al (), Chiang et al (), and Huang et al (), respectively. The fault parameters corresponding to each of the mainshocks are listed in Table .…”

“…The uniform and oversimplified slip inferred using empirical relationships in the 2008 event may lead to a biased result and interpretation, while three other source models also have uncertainties that propagate through the Coulomb stress calculations (e.g., Parsons, ). In this study we did not test the stress computation using different source models, given the selected models themselves were compared with other results in the original papers (Chiang et al, ; Huang et al, ; Lee et al, ; Shih et al, ). Instead, we attempted to approach uncertainty produced by receiver fault orientations, as shown in Figures and .…”

“…The aftershocks reveal a linear structure of NE–SW strike and 45°SE dip, consistent with the focal mechanism of strike = 37°, dip = 48°, and rake = 96. The faulting on the northern extension of the Chishan Fault may be responsible for this Taoyuan earthquake sequence (Shih et al, ). In 2010, the M w 6.4 Jiashian earthquake occurred to the south of the 2008 event and just 5 km east of the Chaochou fault (blue star in Figure ).…”

A study of large earthquake sequences in the Sumatra subduction zone and its possible implications

“…The double-difference algorithm has been implemented in the computer program HypoDD (Waldhauser 2001). The program HypoDD has been extensively tested with data from permanent networks and aftershock arrays around the world to verify its ability to improve the image of seismicity (Rietbrock and Waldhauser 2004;Waldhauser et al 2012;Shih et al 2014). The earthquake data of P-wave arrival times collected from stations of the BMKG seismic network have been analyzed in this study based on the HypoDD algorithm.…”

Studies on Aftershocks in Taiwan: A Review

“…From the aftershock spatial distribution, the major fault plane is ~10 km long along the strike and 10 km wide in the dip direction. Shih et al (2014) observed that relocated aftershocks formed clusters, and an area with low aftershock activity was beneath the mainshock. The aftershock distribution suggests a southeast-dipping fault plane, which is consistent with one of the nodal planes of the focal-plane solution for the mainshock.…”