Earthquake catalog in northeastern Tibetan plateau from the large aperture ChinArray-II through deep learning approach

SUMMARY We present an earthquake catalogue in northeastern Tibetan plateau between September 2013 to April 2016 during the ChinArray-II deployment. Using continuous records from 676 transportable ChinArray-II stations and 172 permanent stations, the P/S phases are obtained using one deep learning phase picker. After associating these phases, the events are identified and located to establish the ChinArray-II Regional Earthquake Database (CARED-II). Benefiting from both improved station coverage and sensitive phase picker, CARED-II catalogue has 156 057 events (around 3 million picks), about tenfold more than the manual routine catalogue (15 967 events) using the permanent stations. The improved event catalogue delineates the fault structures clearly. The deep structure of south-dipping north Qilian thrust faults is revealed, consisting with previous geology studies. The hidden faults and fault connectivity are revealed by improved seismicity, especially in the Alxa Block with sparse permanent stations and severe environments restricting geological field work. Moreover, small anthropogenic events are identified and related to highway tunnel construction across Qinling Mountain, forming a straight event cluster. The results demonstrate the high event detection ability of our procedure and reliability of the automatic catalogue. Our array-based CARED-II catalogue provides improved seismicity images in northeastern Tibet and could be used for further seismology and geotectonic studies.