Abstract
The Pearl River Estuary area, located in the middle part of the southern China coastal seismic belt, has long been considered a potential source of strong earthquakes above magnitude 7.0. To scientifically assess the potential strong earthquake risk in this area, a three-dimensional artificial seismic sounding experiment, consisting of a receiving array and seabed seismograph, was performed to reveal the deep crustal structure in this region. We used artificial ship-borne air-gun excitation shots as sources, and fixed and mobile stations as receivers to record seismic data from May to August 2015. This paper presents results along a line from the western side of the Pearl River Estuary to the western side of the Baijing-Gaoming-Jinwan profile. A two-dimensional velocity structure was constructed using seismic travel-time tomography. The inversion results show that the Moho depth is 27 km in the coastal area and 30 km in the northwest of the Pearl River Estuary area, indicating that the crust thins from land to sea. Two structural discontinuities and multiple low-velocity anomalies appear in the crustal section. Inside both discontinuity zones, a low-velocity layer, with a minimum velocity of 6.05 km s−1, exists at a depth of about 15 km, and another, with a minimum velocity of 6.37 km s−1, exists at a depth of about 21.5 km between the middle and lower crust. These low velocities suggest that the discontinuities may consist of partly molten material. Earthquakes with magnitudes higher than 5.0 occurred in the low-velocity layer along the profile. The deep Kaiping-Enping fault, rooted in the crust, may be one of the most important channels for deep material upwelling and is related to tectonic movement since the Cretaceous in the Pearl River Delta tectonic rift basin.
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Acknowledgements
The authors thank Professor Min Xu from South China Sea Institute of Oceanology for improving the quality of the manuscript. Funding for the fieldwork has primarily come from China Earthquake Administration and the People’s Government of Guangdong Province. Teams from the Guangdong Earthquake Administration, CEA, South China Sea Institute of Oceanology, CAS, and Geophysical Exploration Center, CEA participated the field work. In addition, the China Seismic Array provided over 60 instruments for observation, and the Geophysical Exploration Center, CEA, provided over 300 instruments for observation. Support for fieldwork was also provided by the People’s Government of Guangzhou, the People’s Government of Shenzhen, the People’s Government of Dongguan, the People’s Government of Jiangmen, the People’s Government of Foshan, the People’s Government of Zhaoqing, the People’s Government of Huizhou. The data processing and interpretation is support by the National Natural Science Foundation of China (No. 41676057. The public domain GMT package (Wessel and Smith, 1995) was used to produce some of the figures.
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Zhang, X., Ye, X., Lv, J. et al. Crustal structure revealed by a deep seismic sounding profile of Baijing-Gaoming-Jinwan in the Pearl River Delta. J. Ocean Univ. China 17, 186–194 (2018). https://doi.org/10.1007/s11802-018-3489-7
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DOI: https://doi.org/10.1007/s11802-018-3489-7