青海玛多MS7.4地震前LURR与OLR短临异常关联性研究

加卸载响应比(LURR)是根据岩石应力-应变关系的动态演化规律提出的地震预测方法。以Benioff应变为响应量,分析青海玛多M_S7.4地震前震中及其周边400 km内的LURR异常的演化特征发现,在震前一个月LURR值达到最高值,半个月之后出现高值回落的现象,说明此时孕震区岩石介质已进入屈服阶段的末端。在此基础上,利用NOAA卫星地面长波辐射(OLR)数据,分析高值回落后(5月14—25日)地面长波辐射值的短临异常演化规律。结果显示:震前在空间上仅仅在震中北部出现OLR显著且连续的短临异常变化并呈现向震中扩展的趋势,在时间上整个演化过程经历了初始增温-异常扩展-达到峰值-异常减弱-地震发生-异常消失等6个阶段。LURR和OLR震前短临异常特征说明,回落前的LURR高值反映了岩石介质屈服阶段的结束,OLR在一定程度上可以表征处于临界状态的活动断层的构造应力累积状态,综合研究两种物理参量震前异常演化特征,有助于更准确评估地震活动趋势。

Correlation between short-term and imminent anomalies of LURR and OLR before the Maduo MS7.4 earthquake in Qinghai Province, 2021

Load/unload response ratio (LURR) is an earthquake prediction method based on the dynamic evolution law of rock stress-strain relationship. Using Benioff strain as the response, this paper analyzed the evolution characteristics of LURR anomalies within 400 km of the epicenter of 2021 Maduo M_S7.4 earthquake in Qinghai Province and its surrounding area, and found that the LURR reached the highest value one month before the earthquake and fell back half a month later, indicating that the rock medium in the seismogenic zone has entered the end of yield stage. On this basis, the evolution law of short-term and impending anomalies of outgoing long-wave radiation (OLR) value from May 14 to 25 was analyzed by using the OLR data from NOAA satellite. The results showed that: before the earthquake, significant and continuous short-term and impending abnormal changes of OLR occurred only in the northern part of the epicenter and showed a trend of expanding toward the epicenter. In terms of time, the entire evolution process experienced six stages: initial temperature increase-abnormal expansion-peak value-anomaly weakening-earthquake occurrence-anomaly disappearance. The short-term and imminent anomaly characteristics of LURR and OLR before the earthquake indicated that the LURR high value before the fall reflects the end of yielding stage of rock medium. To a certain extent, OLR can characterize the cumulative state of tectonic stress of active faults in a critical state. The comprehensive study of evolution characteristics of the two physical parameters before the earthquake can be helpful to more accurate evaluation of seismic activity trend.