Microseismic Detection And Magmatism In The Wudalianchi Volcanic Area

The Wudalianchi volcano is one of the typical intraplate volcanoes in Northeast China.It is located at the intersection area of the Great Xing'an Range,the Less Xing'an Range,and the Songliao Basin.The volcano field consists of 14 volcanic cones dominated by NE-trending faults,which includes North Gelaqiushan,South Gelaqiusahn,Wohushan,Yaoquanshan,Bijiashan,Laoheishan,Huoshaoshan,Weishan,East Jiaodebushan,West Jiaodebushan,Xiaogushan,West Longmenshan,East Longmenshan and Molabushan volcano.According to historical records,the Laoheishan and Huoshaoshan volcanoes erupted within the time form 1719 to 1721.In recent years,magnetotelluric imaging showed that there was a cooled magma chamber under the Laoheishan volcano,whereas ambient noise tomography showed that there is a magma chamber under the Weishan volcano.Therefore,the magmatism under the Wudalianchi volcano is still unclear.Investigating the microseismicity in the Wudalianchi volcanic area is of great scientific significance to understand the magmatism and deep dynamic processes in the Wudalianchi volcanic area.In this work the area with a center of the Wudalianchi volcano and a radius of 75 km is taken as the study area,which includes 24 WAVESArray portable seismic stations and 3 provincial permanent stations of China Earthquake Administration.Continuous waveform data are collected at these stations from June 2015 to May 2019 and pick-based detection method is adopted to search for earthquakes.Firstly,the PhaseNet algorithm is used to pick 3221773 P-wave and 2590012 S-wave arrival time data from the three-component continuous seismograms.Then,based on the IASP91 1-D velocity model,the REAL algorithm is used for phase association and earthquake location,and 765 seismic events are obtained,and their magnitudes are evaluated by simulating the seismic waveforms of the horizontal component to the Wood-Anderson seismograph.Using the Hypo2000 location method,the earthquakes are relocated,and 532 events are obtained.Finally,using the HypoDD algorithm,380 events are obtained.The results show that the spatial distribution pattern of earthquakes under the Wudalianchi volcanic area illustrates a cone-like structure,which indicates the existence of magmatism.During the observation period,there were more than two peaks of seismic activity in the Wudalianchi volcanic area,which provides strong seismological evidence for intermittent supply of mantle magma.The seismicity under the Sunyongshan and Liuhaogaodi areas presents a columnar structure,while the seismicity under the Erlongshan area presents a double-layer structure,indicating that the magmatism is more influenced by geological structure.