海原断裂带中强地震前b值时空异常特征研究

Spatial and Temporal Anomaly Characteristics of b-Value before Moderate Earthquake in Haiyuan Fault Zone

摘要: 海原断裂带是青藏块体东北缘一条重要的断裂带，历史上强震丰富，现今小震活跃，目前仍存在发生中强以上地震的危险性，也是诸多地震学者重点关注的区域之一。本文基于小震b值在地震预测研究中的重要作用，系统研究了1970年以来海原–六盘山断裂带及附近区域小震b值时空变化特征，重点回溯了宁夏南部5次M_S 4.9以上地震前的b值异常变化特征，并分析发现宁夏南部小震b值在2023年12月31日平川4.9级地震后处于低值波动变化，表明目前海原–六盘山断裂带处于应力积累状态，该结果为宁夏地区震情短临跟踪提供参考依据。

Abstract: Haiyuan fault zone is an important fault zone in the northeast margin of Qinghai-Tibet Block. It is rich in strong earthquakes in history, but active in small earthquakes today. At present, there is still a risk of moderate and strong earthquakes. Based on the important role of b-values of small earthquakes in earthquake prediction, this paper systematically studies the temporal and spatial variation characteristics of b-value of small earthquakes since 1970 in the Haiyuan-Liupanshan fault zone, and focuses on the b-value anomaly changes before five earthquakes with magnitude ≥ M_S 4.9 in southern Ningxia, and finds that the b-value of small earthquakes in southern Ningxia is at a low value fluctuation after Pingchuan M_S 4.9 earthquake on December 31, 2023. The results show that the Haiyuan-Liupanshan fault zone is in the state of stress accumulation, which provides a reference for the earthquake short-term tracking in Ningxia region.