A REVIEW OF THE THINKING AND PROCESS ABOUT PREDICTION OF LUSHAN M7.0 EARTHQUAKE ON APR. 20, 2013

doi:10.3969/j.issn.0253-4967.2014.04.012

Abstract

Abstract:

Before the Lushan M7.0 earthquake of April 20, 2013, fault displacement time histories inferred from near-field observation in Xianshuihe, Anninghe and Zemuhe Fault zones in Sichuan Province showed long-, mid-, and short-term anomalies which deviated from the normal background. The long-term anomalies were mainly represented by extensional faulting, the mid-term anomalies were marked mainly by turning of anomaly trends, and the short-term anomalies appeared mainly as compressional movement of the central-northern segment of Xianshuihe Fault. And based on these anomalies, a relatively accurate short-term prediction to this earthquake was proposed by the Survey Engineering Institute of Earthquake Administration of Sichuan Province. In this article, we summarize the thoughts and process of the prediction to Lushan earthquake, and present the bases and process for the long-, mid-, and short-term prediction. This experience can be useful for short-term prediction of strong earthquake in the future. Our preliminary results show that: 1)The sudden acceleration of variation in anomaly of short-baseline and short-leveling has short-term predictive significance to the origin time of strong earthquake. 2)Combined with analysis on the characteristics of time series of the occurrence time of cross-fault deformation anomalies, and the high gradient zones and their temporal evolutions revealed by mobile gravity surveys, we chose the intersection of the anomalous zones as the hazardous area and found it has a better predictive effect for determining the location of strong earthquake. 3)Statistical analysis shows that the duration of cross-fault deformation anomalies has certain significance for predicting the magnitude of strong earthquake. According to the characteristics of fault activity, the southeastward movement rate of the Bayar Har block may be greater than that of the eastern boundary of the Sichuan-Yunnan block before the Lushan earthquake, which aggravated the compressional and extensional movement of the northern segment of Longmenshan Fault, the middle-northern segment of Xianshuihe Fault and the Zemuhe Fault, and made the southern segment of Longmenshan Fault and the northern segment of Anninghe Fault locked. The faults differed remarkably in their activity patterns, which were mutually restrained and adjusted, as well as convertible. Thus, brittle rocks in the transition zone between plateau and basin ruptured and earthquake occurred. Currently, short-term earthquake prediction is still based on empirical results, and its scientificity is insufficient and pending further discussion.

Key words: near-field fault displacement, mobile gravity, Lushan earthquake, prediction review

摘要：

2013年 "4.20"芦山7.0级地震前, 四川跨断层形变资料在紧邻发震断裂的鲜水河、安宁河、则木河断裂带上出现了偏离正常背景的长、中、短期异常, 长期异常以断层张性活动为主, 中短期以趋势转折为主, 短期则以鲜水河中北段压性活动为主, 且据此做出了较准确的短期预测.文中将对该次地震的预测思路及过程进行回顾, 展示长、中、短期预测依据及过程, 为未来强震的短期预测总结经验.分析结果认为:1)跨断层短水准、短基线的突变加速异常对强震发生的时间有着较好的短期预测意义;2)综合利用跨断层前兆异常出现的时序特征、流动重力高梯度带及差异性变化进行分析, 提取其异常交会部位, 对强震的发生地点有着较好的预测效果;3)跨断层形变异常持续时间的统计对于强震发生的震级有一定的指示意义;从断层活动特性来看, "4.20"芦山地震前, 巴颜喀拉块体向SE的运动速率可能大于川滇块体东边界, 导致龙门山北段、鲜水河中北段、则木河断裂带断层挤压推拉活动加剧, 龙门山南段、安宁河北段 "闭锁", 各个断层活动方式产生明显差异, 但又相互牵制、相互调整, 并在运动形式上相互转换, 从而使高原与盆地过渡地带的脆性岩层产生破裂, 发生强震.

关键词: 跨断层形变, 流动重力, 芦山地震, 预测回顾

CLC Number:

P315.75

SU Qin, YANG Yong-lin, ZHENG Bing, WANG Shuang-hong, LI Fei-fei, LIU Guan-zhong. A REVIEW OF THE THINKING AND PROCESS ABOUT PREDICTION OF LUSHAN M7.0 EARTHQUAKE ON APR. 20, 2013[J]. SEISMOLOGY AND GEOLOGY, 2014, 36(4): 1077-1093.

苏琴, 杨永林, 郑兵, 王双洪, 李菲菲, 刘冠中. 4 ·20芦山7.0级地震预测思路及过程回顾[J]. 地震地质, 2014, 36(4): 1077-1093.

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