5:15 PM - 6:45 PM
[SCG40-P26] Resolving source parameters of induced seismicity using near-field observations
Keywords:the Three Gorges Reservoir, dense seismic array, micro earthquakes, Sp-converted wave
After the impoundment of the Three Gorges Reservior, there are some induced seismicity in Zigui, Hubei province, China. With permanent seismic observations with station spanning of ~ 15 km, there are roughly located at the vicinity of the northwest end of the Xiannvshan fault. Due to sparse distribution of the seismic stations, the source parameters such as focal depth and focal mechanism are remain unresolved.
Here we deployed a dense nodal seismic array with station interval of 2-5 km, to monitor the seismicity of the seismicity that occurred in Zigui.
With those dense observations, we are able to accurately determine the epicenters of the earthquakes. By selecting stations within 4 km to relocate the sources on two dimensions and recalculating the focal depth by considering the S-P arrival-time difference recorded on proximate stations, we are able to determine a more accurate focal depth.
For some stations that are located in sedimentary regions, we noted a distinct seismic phase with particle motion akin to the P wave, occurring between the direct P and S waves. This phase, known as the Sp-converted wave, is generated by the interface between sedimentary layers and the basement. Notably, the Sp-P arrival-time difference exhibits a nearly linear increase with the focal depth when the epicentral distance is short. Leveraging these Sp converted phases not only improves the depth accuracy of shallow earthquakes but also enables us to constrain VP/VS, resulting in a more comprehensive understanding of the seismic activity in the region.
Through our meticulous methodology and analysis, we are delving deeper into the unique characteristics of micro-earthquakes in the Three Gorges Reservoir, ultimately paving the way for a more nuanced insight into the seismic potential and fault reactivation in this area.
Here we deployed a dense nodal seismic array with station interval of 2-5 km, to monitor the seismicity of the seismicity that occurred in Zigui.
With those dense observations, we are able to accurately determine the epicenters of the earthquakes. By selecting stations within 4 km to relocate the sources on two dimensions and recalculating the focal depth by considering the S-P arrival-time difference recorded on proximate stations, we are able to determine a more accurate focal depth.
For some stations that are located in sedimentary regions, we noted a distinct seismic phase with particle motion akin to the P wave, occurring between the direct P and S waves. This phase, known as the Sp-converted wave, is generated by the interface between sedimentary layers and the basement. Notably, the Sp-P arrival-time difference exhibits a nearly linear increase with the focal depth when the epicentral distance is short. Leveraging these Sp converted phases not only improves the depth accuracy of shallow earthquakes but also enables us to constrain VP/VS, resulting in a more comprehensive understanding of the seismic activity in the region.
Through our meticulous methodology and analysis, we are delving deeper into the unique characteristics of micro-earthquakes in the Three Gorges Reservoir, ultimately paving the way for a more nuanced insight into the seismic potential and fault reactivation in this area.