Development And Application Of Earthquake Real-time Monitoring System In Reservoir Area Based On Artificial Intelligence

Real-time monitoring and analysis of seismic activity in reservoir areas are crucial for studying and mitigating the risks of reservoir-induced earthquakes.The main purpose of this thesis is to develop a real-time seismic monitoring system for reservoir earthquakes,which can be divided into the following aspects:1)testing the generalizability of LOC-FLOW in the reservoir area,testing the effect of different parameters on the output catalog,and selecting the appropriate parameters for subsequent development;2)developing a real-time seismic monitoring system and evaluating its performance in a dense reservoir network.Formally access real-time data for seismic monitoring in the Baihetan reservoir area;3)Use the system to process offline(LOC-FLOW)continuous waveform data to output seismic catalogs before and after water storage in the Baihetan reservoir area and comprehensively analyze the characteristics of seismic activities.In the testing phase,14 days of continuous waveform data recorded at stations within multi-basin reservoirs in southwest Guizhou were processed using LOC-FLOW.The number and quality of the output seismic phases of Phase Net with different threshold settings were compared,and the final threshold was chosen to be 0.5 under the balance of the detection accuracy rate and the detection completeness rate.426events were produced after association and localization,and the recall rate was 83.9%compared to 118 events obtained by manual processing.The reasons for the missing events include the setting of the maximum gap angle(GAP),the low signal-to-noise ratio of the waveform and the inconsistent criteria in manual localization;among the matched events,the basic parameters of the seismic source produced by LOC-FLOW deviated less from the manual processing.Finally,the reliability of the output catalog is further illustrated by manually checking all event waveforms.On this basis,LOC-FLOW was further used to retrospectively process the continuous waveform data from2020 to the first half of 2021 in the multi-basin reservoir area of southwest Guizhou,and the final obtained events were about five times more than the manual processing,the completeness magnitude decreased from 1.3 to 0.8.The calculated b-value of seismic activity in the Qianxi area was 1.25,which is more in line with the b-values of previous studies in multiple reservoir areas.The output catalog was used to analyze the seismic characteristics of reservoirs in the region.The results of the study showed that the seismic activity near the reservoir area is related to the reservoir capacity,storage time,geological and tectonic background near the reservoir area,hydrogeological features,and active fractures.The results of the testing phase show that LOC-FLOW can be used for the detection and localization of reservoir earthquakes after reasonable setting of parameters,and can be used to develop a real-time monitoring system for reservoir earthquakes.In the developing phase,LOC-FLOW is used as the core to develop the real-time seismic monitoring system.The architecture of the system mainly includes three sub-modules,which are data module,positioning module and output module.Among them,the data module is responsible for accessing,processing and storing real-time data,and transmitting real-time waveforms to the localization module;the localization module is responsible for processing real-time waveforms and transferring seismic information to the output module after seismic detection,seismic phase pickup,seismic phase association,seismic localization and integrity determination;the output module is responsible for interaction with users.To test the timeliness of the system output catalog,it was run for one month in the lower Jinsha River reservoir area to process real-time waveforms recorded by 129 broadband seismometers in the area.Finally,the system produced 5,370 seismic events with an average of 116.81 s after the earthquake,and about 96.74%of the events were produced within 150 s after the earthquake.In order to evaluate the reliability and completeness of the system output catalog,this paper discusses three aspects of comparing the manual catalog,parameter setting,and manual checking.The system recalled 97.6%of the 1692 earthquakes produced by the manual catalog during the time period,and the deviation of the basic parameters of the source of the two catalog-matched events was small;comparing the previous parameter settings,the system had stricter parameter settings during the real-time operation phase;manually checking all the event waveforms with M_L≤0 produced by the system during the trial operation phase,about 97.6%of the events were true and reliable.The results of the trial run phase show that the system can produce a real-time seismic catalog of the reservoir area,and the reliability of the output catalog is consistent,timely and complete compared to the manual one.For seismic monitoring and seismic follow-up in the Baihetan reservoir area,real-time data from 129 stations in the lower Jinsha River gradient reservoir area have been officially accessed since January 1,2023.As of May10,2023,the system automatically produced 8,153 seismic events,including one earthquake of magnitude 4 or higher and eight earthquakes of magnitude 3 or higher.To provide users with a more timely understanding of the seismic activity in the region,this paper also designed a visualization interface applicable to seismic monitoring in the Baihetan reservoir area according to the requirements,which allows users to quickly understand the real-time output of earthquake locations,historical earthquake distribution,water level-earthquake frequency relationship and regional b-value changes on the web or cell phone.In the application phase,this paper processed continuous waveform data from2021.1 to 2022.7 in the Baihetan reservoir area using the system offline(LOC-FLOW).The relocation yielded 54,559 seismic events with median horizontal positioning errors of 27.1 m and 39.5 m,and median vertical positioning errors of 78.0 m.The positioning results indicate that the seismicity in the reservoir area has increased significantly after water storage.The produced high-precision seismic catalogs portray a number of tiny faults in the region that are consistent with the orientation of large fracture zones,indicating that the seismic activity after water storage is still controlled by the regional tectonics.After water storage,different regions show significant differences in seismicity.Some areas connected to the Jinsha River and its tributaries show obvious strip-like features,presumably related to fluid diffusion and rising groundwater levels;the seismic activity features near the Qiaojia Basin,which is low-lying and has a wide area inundated by reservoir water,are particularly complex,presumably related to various factors such as gravity loading and karst collapse.