2022年1月8日青海门源6.9级地震短临异常跟踪分析

A Short-term Prediction Practice on the Menyuan M6.9 Earthquake on January 8, 2022

摘要:

2022年1月8日青海门源县发生6.9级地震，此次地震前青海地区出现了大量地球物理观测异常。2021年10月下旬青海地区出现地磁垂直强度极化高值异常，10月27日异常台站最多，并在门源-祁连至兴海地区形成一个面积约为6.6×10⁴km²的高值异常区；此外，2021年7—11月青海地区8项地下流体观测数据出现准同步异常变化。结合青海及周边地区历史震例的分析结果，认为2021年11月23日至2022年1月23日，青海西北部地磁垂直强度极化高值区内可能发生5.6～6.4级地震。门源6.9级地震发生在地磁垂直强度极化异常出现后的73天，震中位于预测区的边缘，地震的发生时间和地点与预测意见一致，但震级超出预测意见上限值0.5级。此次地震前基于地球物理观测地震预测指标体系开展的短临异常跟踪分析过程，对中国大陆西部地震预报工作具有一定的参考意义。

Abstract:

An M6.9 earthquake occurred in Menyuan county, Qinghai Province on January 8, 2022. Some geophysical precursory anomalies have been recorded in Qinghai region before this event. For example, obvious anomalies of geomagnetic vertical intensity polarization happened in Qinghai area at the end of October 2021. The number of anomalous stations reached the climax on October 27, and the anomaly area of 6.6×10⁴km² covered Menyuan-Qilian to Xinghai area in northwest Qinghai. In addition, from July to November in 2021, eight subsurface fluid observations in Qinghai region showed quasi-synchronous abnormal changes. With the reference of previous earthquake cases in Qinghai and its surrounding areas, we made a conclusion that an M5.6 to M6.4 earthquake might occur in geomagnetic anomalous area in northwest Qinghai from November 23, 2021 to January 23, 2022. Thus, a short impending earthquake prediction card had been provided. The Menyuan M6.9 earthquake occurred 73 days after the occurrence of the anomaly, and its epicenter is located at the boundary of the prediction area of geomagnetic vertical intensity polarization anomaly. In light of this practice, the predicted time and the epicentral location of the earthquake are basically good enough but the magnitude is 0.5 magnitude higher than expected. However, this short-term anomaly tracking and prediction practice will be of importance in Qinghai area and even in the western China.