基于视电阻率观测对2023年12月18日甘肃积石山MS6.2地震的预测

Apparent Resistivity Observation-based Prediction of the Jishishan MS6.2 Earthquake of December 18, 2023,Gansu Province, China

摘要:

2023年12月18日甘肃临夏积石山M_S6.2地震前,震中300km范围内运行有9个视电阻率观测站,其中5个观测站数据质量较好,其余4个观测站因测区内环境因素影响而难以为日常跟踪提供稳定的动态背景。定西站自2021年7月开始出现下降异常,2022年1月8日门源M_S6.9地震发生之后,该异常一直未恢复。2023年6月以来,武胜驿和武威站出现下降异常变化。此外,自2023年6月开始,距离震中335km的武都站也出现上升异常变化。依据这4个观测站的异常,分析认为祁连山地震带东段至甘东南地区存在发生6级左右地震的危险性,且地震类型最可能为逆冲型。2023年10月通渭站出现“快速下降—转折回升”形态的短期异常变化,随后在10月27日的周震情例会上对该预测区域给出了短期预测意见,12月18日M_S6.2地震发生在预测区内,且震源机制解类型也为预测的逆冲型。

Abstract:

Nine DC apparent resistivity stations within a 300km radius of the Jishishan M_S 6.2 earthquake,which occurred on December 18,2023,were in normal operation. Among these,five stations provided high-quality data,while the remaining four were rendered ineffective due to environmental disturbances in the monitoring areas. Notably,anomalous variations at the Dingxi station were first observed in June 2021 and have persisted without recovery following the Menyuan M_S6.9 earthquake in January 2022. Since June 2023,both the Wushengyi and Wuwei stations have exhibited declining anomalous trends,while the Wudu station,located 335km from the epicenter,has shown an upward trend during the same period. Based on the anomalies recorded at these four stations,a potential risk of a magnitude 6 earthquake was identified within the region spanning the eastern section of the Qilian Mountain seismic belt to southeastern Gansu Province. The anticipated focal mechanism was predominantly of the thrust type. Furthermore,following the emergence of short-term anomalous variations at the Tongwei station in October 2023,a short-term seismic forecast was presented during the weekly earthquake situation meeting on October 27. Subsequently,the Jishishan M_S6.2 earthquake on December 18 occurred within the predicted region,and its focal mechanism solution confirmed a thrust-type event.