Micro-Earthquake Seismicity and Tectonic Significance of the 2012 Ms 4.9 Baoying Earthquake, Jiangsu, China

Abstract

On July 20, 2012, the Ms 4.9 Baoying Earthquake occurred near the junction of Baoying County and Gaoyou City in Jiangsu Province, eastern China. Due to no obvious surface rupture and limited observation of earthquake sequence, the seismogenic structure of the Ms 4.9 Baoying Earthquake is still unclear. In this study, 80 earthquakes provided by China Earthquake Network Center (CENC) are first relocated; and then the relocated 75 events with high signal-to-noise ratios as templates are utilized to scan through continuous waveform data (July 11 to August 31, 2012) using graphics processing unit-based match and locate (GPU-M&L) technique. Then the DeepDenoiser, a deep-learning-based noise reduction technique, is used to further confirm some newly detected events; and the double-difference relocation (HypoDD) algorithm is used to relocate the earthquakes. We detect and relocate more than twice as many events as the CENC routine catalog, which includes 15 fore-shocks and 230 aftershocks. The results show that the foreshocks are mainly distributed in the NW direction along the extended SE section of the blind Xiagonghe fault (XF), which is orthogonal to the strike of the seismogenic fault of the Ms 4.9 Baoying Earthquake (Yangchacang-Sangshutou fault, named YSF). Most of the aftershocks are generally distributed along the NNE-trending YSF and illuminate a steeply dipping plane. This study reveals detailed spatiotemporal evolution of the earthquake sequence and suggests that the buried XF extends southeastward and cuts through the NNE-trending seismogenic YSF.

Keywords

2012 Ms 4.9 Baoying Earthquake / micro-earthquake seismicity / tectonics / GPU-M&L / HypoDD / DeepDenoiser

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