[S-SS05] Advancements in Regional Seismic Networks: Operations, Applications, and Development

[SSS05-04] Three Gorges Seismological Network: Monitoring Seismicity at the Three Gorges Reservoir Forebay

*Fang Chen¹, Dun Wang¹, Dongdong Yao², Wulin Liao³, Heiya Na¹ (1.State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, China, 2.State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei Province, China, 3.Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan, China)

Keywords:Three Gorges Reservoir Forebay, Regional Seismological Network, Seismicity Monitoring

This study is based on a dense seismic network deployed in the Three Gorges Reservoir Forebay, in order to investigate the relationship between seismic activity in the region, reservoir water levels, and local tectonics. The network has been monitoring seismic activity since September 2020, with inter-station distances of less than 5 km. The first phase of the network's operation spanned from 2 September 2020 to 16 November 2020, consisting of 78 short-period seismometers with an approximate inter-station distance of 5 km. We established earthquake catalogs for the approximately two months of data using both manual and machine learning methods. During this period, the machine learning method identified 1,165 seismic events, which exceeded the 623 events detected in the manual catalog using the same dataset. The catalog's magnitude of completeness is ∼ M_L −0.3. The precise earthquake catalogs, obtained through absolute and relative location methods, reveal the spatial distribution characteristics of seismic activity in the region. By comparing these two catalogs, we validated the monitoring capability of our network and the robustness of the machine learning techniques in detecting seismic events.
Subsequently, using the machine learning-based process, we constructed earthquake catalogs for a two-year period. During this period, the seismic network expanded to at least 150 short-period seismometers with station spacing less than 5 km, detecting over 15,000 events. The refined seismic catalog reveals detailed spatial distribution features in the Three Gorges Reservoir Forebay, such as multiple seismic clusters around major faults, including the Xiannvshan fault and Jiuwanxi Fault. Notably, an earthquake swarm near the Guojiaba region, close to the end of the Xiannvshan fault, shows two clear streaks at depths of 5 km and 10 km. The dense seismic network provides insights into the fault morphology of the Three Gorges Reservoir Forebay, offering valuable evidence for regional tectonic studies and earthquake disaster risk assessment. This study has significant implications for further research and analysis of the region's active tectonics and induced earthquake seismicity.