3D Visualization Analysis of Longtan Reservoir-Induced Earthquakes and Active Faults

This article collected geological formation, fault occurrence, precise positioning of medium and small earthquakes, focal mechanism solution, and other data of Longtan Reservoir area, built a 3D geologic model on ARCGIS platform, conducted a 3D visualization analysis on the relationships between reservoir earthquakes and active faults and between focal mechanism of medium and small earthquakes and fault occurrence and discussed 3D spatial relationship between focal depth of reservoir-induced earthquakes and geological formation. Results showed that (1) Using focal longitude and latitude, magnitude, focal depth and other parameters from precise positioning results of small earthquakes of 5 earthquake clusters, a 3D spatial model was built between reservoir earthquakes and faults and 3D buffer zones were set up within 6 km radius and 20 km depth of each fault, to analyze the relationship between faults and earthquake distribution, indicating that Gaoxu-Bamao Fault (F2), Fengting-Xialao Fault (F3), Maer-Lalang Fault (F4), Changli-Banan Fault (F8) and Longfeng-Bala Fault (F9) were controlled seismic faults of various earthquake clusters. (2) Using focal longitude and latitude, magnitude, focal depth, strike, dip, slip, T-axis dip, P-axis dip and other parameters of 120 focal mechanism solutions derived from waveform data of earthquakes with magnitudes greater than M L 2.0 in the reservoir area, a 3D focal mechanism and fault model was built, to calculate focal mechanism type and parameters of 5 earthquakes clusters, suggesting that focal mechanisms in the reservoir area were mainly thrust. Strike and dips of 5 earthquake clusters were basically identical with fault occurrence of main faults through this cluster; (3) Using geological formation, fault occurrence and precise positioning results of medium and small earthquakes, a 3D strata and earthquake model was set up, the relationship between focal depth and geological formation was analyzed visually, suggesting that brittle strata within 5–13 km under the reservoir area were prone to brittle rupture and thereby induce seismicity.