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Study on the background and triggering seismicity in Yutian, Xinjiang, China region

Shengfeng Zhang, Yongxian Zhang, Jiancang Zhuang, & Zhongliang Wu

Published August 14, 2020, SCEC Contribution #10526, 2020 SCEC Annual Meeting Poster #103

Several earthquakes of magnitude 6.0 or above have occurred in Yutian, Xinjiang, China, and a MS6.4 earthquake occurred in this area again on June 26, 2020 in Beijing time. After the earthquake, the Institute of Earthquake Forecasting, China Earthquake Administration conducted an earthquake emergency consultation meeting in time and carry out a “virtual scientific” research for it. A serious of questions expecting to be solved are that whether this earthquake is an aftershock of other strong events, what is the relationship with previous two MS7.3 earthquake sequences in this area, or is it just a background events? For these questions, we use the spatial-temporal ETAS model to analyze the earthquake sequence since 1970 in this region (81.33 º-83.33ºE,34.73º-36.73ºN), and obtains several model parameters which can characterize the seismic sequence. The model also gives the regional background seismicity level, the clustering rate and the total activity level including these two parts. Statistical de-clustering method based on ETAS model is used to separate the background and clustering events, so the probability of each event as a background event or triggered event is also obtained. The results show that the occurrence rate of cluster events in this area accounts for the main part of the total seismicity. If a certain level of strong earthquake occurs in this area, a large number of aftershocks tend to be triggered in a short time. In addition, the probability of this earthquake being a background event is 74.5%, and the probability of being triggered by two MS7.3 earthquakes on March 21, 2008 and February 12, 2014 are 0.04% and 0.9%, respectively. Even though this earthquake has a high probability to be an independent background events, other events has still some contribution to it mainly from 2014. Through systematically analyzing the triggering ability of events in this region, we found that among the seismic events in the study area that has contribution to triggering other events, the MS7.3 earthquake on February 12, 2014 had the highest average level to "intervene" others, which only reached 0.15. From the above analysis, we can suggest that the working routine of determine whether an earthquake is a background or triggered event based on a probability value computed using the statistical de-clustering method may be an effective bridge connecting pure scientific research and seismic consultation system in China.

Key Words
Spatial-temporal ETAS model, background events, triggered events, Yutian MS6.4 earthquake, aftershock probability

Zhang, S., Zhang, Y., Zhuang, J., & Wu, Z. (2020, 08). Study on the background and triggering seismicity in Yutian, Xinjiang, China region. Poster Presentation at 2020 SCEC Annual Meeting.

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Earthquake Forecasting and Predictability (EFP)