2022年门源M6.9地震前孕震区跨断层形变异常特征及其机理

doi:10.12196/j.issn.1000-3274.2023.01.001

摘要/Abstract

摘要： 跨断层形变测量在寻找地震前兆信息和强震预测预报工作中做出了重要贡献。 2022年青海门源M6.9地震前, 祁连山—海原断裂带上的跨断层短水准资料有着显著的前兆异常。本文基于截至2021年12月的跨断层短水准资料, 利用时序分析法、形变异常强度分析法和垂直形变累积率分析法等, 提取震前异常的时空演化特征, 探讨震前中短期断层活动情况及其变形机理。结果表明, 在NE-SW向挤压和NW-SE向水平剪切共同作用的动力学背景下, 震源区垂直形变趋势累积处于高值, 具有一定的应变能累积背景; 在震前5年时间, 靠近震中的断层运动发生偏离线性的“迟滞”现象, 且在震前2年内异常空间分布具有向震中迁移集中的特征, 表征靠近震源区地壳应力快速积累, 应力局部化增强; 震前半年内, 距离震中60～120 km范围多个场地表现为一致性的、与挤压受力背景相反的张性异常变化, 这种异常现象指示近震区应力积累到一定程度后发生微动态调整、断层局部出现预滑动等变化。

关键词: 2022年门源M6.9地震, 跨断层形变, 异常特征, 断层活动, 形变机理

Abstract: Cross-fault deformation measurements have made an important contribution to the search for earthquake precursor information and strong earthquake prediction and forecasting efforts. Before the 2022 Qinghai Menyuan M6.9 earthquake, the cross-fault data in the Qilianshan-Haiyuan fault zone occured significant precursory anomalies. Based on the cross-fault data before earthquake, this paper uses time-series analysis, deformation anomaly intensity analysis, vertical deformation accumulation rate analysis and other methods to extract the temporal and spatial evolution characteristics of pre-earthquake anomalies, and analyse the short-term and medium-term fault activity and deformation mechanism before the earthquake. The results show that under the dynamic background of the combined action of NE-trending extrusion and NW-trending horizontal shear, the accumulation of deformation trend in the near-seismic region and its vicinity is at a high value, with a certain degree of strain accumulation background. Five years before the earthquake, the movement of the faults in the near-seismic area deviates from linearity and slows down. During the two years before the earthquake, the abnormal spatial distribution has the characteristics of migration and concentration to the epicentral area, which indicates that the crustal stress is accumuleting rapidly and locally enhanced in the near-epicentre area. Within half a year before the earthquake, multiple sites in the region of 60~120 km from the epicenter exhibited consistent tensional anomalies that were opposite to the compressional background, implying that micro-dynamic adjustment occurred after the stress in the near-seismic area accumulated to a certain extent, and pre-slip behaviors occurred.

Key words: Menyuan M6.9 earthquake, Cross-fault deformation, Abnormal features, Fault activity, Deformation mechanism

中图分类号:

P315.7

李媛, 陈长云, 李腊月, 周伟. 2022年门源M6.9地震前孕震区跨断层形变异常特征及其机理[J]. 地震, 2023, 43(1): 1-14.

LI Yuan, CHEN Chang-yun, LI La-yue, ZHOU Wei. The Abnormal Characteristics and Mechanism of Cross-fault Deformation in the Seismogenic Zone before the 2022 Menyuan M6.9 Earthquake[J]. EARTHQUAKE, 2023, 43(1): 1-14.

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