【摘要】 2021年3月30日和6月16日，青藏块体先后发生双湖M_S 5.8和茫崖M_S 5.8地震，其中双湖M_S 5.8地震发生在羌塘块体中部，茫崖M_S 5.8地震发生在柴达木块体北缘。系统总结2次地震前出现的地震活动和地球物理观测异常，结果表明：(1) 2次M_S 5.8地震发生在青藏块体内部地球物理监测能力较弱区域，震前地球物理观测异常少，仅在茫崖地震前存在2项形变背景异常；(2) 2次M_S 5.8地震前地震活动异常较为突出，包括5级地震成组、固体潮调制比、地震发生率指数和Wq值异常，均为1年尺度内的中期异常；(3) 2次地震序列均为主—余型，余震较少，具有不同的衰减特征。综合分析认为，2021年3月和6月，西藏和青海地区2次M_S 5.8地震前存在的地震活动异常在一定程度上弥补了区域地球物理监测能力的不足，或许可为地震监测能力较弱地区的震情跟踪提供关键性参考依据。更多还原

【Abstract】 On March 30 and June 16, 2021, the Shuanghu M_S 5.8 earthquake and the Mangya M_S 5.8earthquake occurred in the Qinghai-Tibet block. The Shuanghu M_S 5.8 earthquake occurred in the middle of the Qiangtang block and the Mangya M_S 5.8 earthquake occurred in the northern margin of the Qaidam block. This paper systematically summarizes the seismicity and geophysical observation anomalies before the two earthquakes. The results show that:(1) Both of the two earthquakes occurred in an area with weak geophysical monitoring capability inside the QinghaiTibet block. There were few geophysical observation anomalies before the two earthquakes,and only two background deformation anomalies existed before the Mangya earthquake.(2) The seismicity anomalies before the two M_S 5.8 earthquakes are more prominent, including the grouped M_S≥ 5.0 earthquake, the solid tide modulation ratio, the seismicity rate index and the Wq-value anomalies, all of which are medium-term anomalies within a year scale.(3) Both of the two earthquake sequences are of mainshock-aftershock type with few aftershocks and different attenuation characteristics. Comprehensive analysis indicates that in March and June 2021, the seismicity anomalies before the two M_S 5.8 earthquakes in Tibet and Qinghai made up for the lack of regional geophysical monitoring capability to a certain extent. This may provide a key reference for earthquake tracking in areas with weak seismic monitoring capability.更多还原