朱守彪^1,2,
1. 中国地震局地壳应力研究所(地壳动力学重点实验室), 北京 100085
2. 中国科学院计算地球动力学重点实验室, 北京 100049

基金项目: 国家自然科学基金项目(41574041, 41874060), 中央级公益性科研院所基本科研业务专项(ZDJ2017-08)以及北京市自然基金(8152034)共同资助


详细信息

作者简介: 朱守彪, 男, 研究员, 理学博士, 博士生导师.现主要从事地球动力学、地震活动性及地震预报方法研究.E-mail:zhusb@pku.edu.cn, zhushoubiao@gmail.com

中图分类号: P315

收稿日期:2019-04-12
修回日期:2019-06-04
上线日期:2020-02-05

Inter-and pre-seismic deformations in the 2011 M_W9.0 Tohoku-Oki earthquake: Implications for earthquake prediction

ZHU ShouBiao^1,2,
1. Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
2. Key laboratory of Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China


MSC: P315

--> Received Date: 12 April 2019
Revised Date: 04 June 2019
Available Online: 05 February 2020


摘要
摘要:强震震前（preseismic）动力学过程的研究对于地震预测具有十分重要的意义，但由于观测资料的限制，目前对强震前孕震区力学状态及其演化过程的认识还非常有限.2011年日本东北9.0特大地震（Tohoku-Oki）发生在GPS观测台站最为密集的地区，为研究特大地震震间（interseismic）与震前的变形状态提供了难得的机会.文中将利用日本东北大地震之前连续的GPS观测资料，分别计算震间与震前的速度场与变形场.通过对比分析发现，日本东北地区（Tohoku）震前的应变状态与震间的有很大的不同，震间的变形主要受到太平洋板块向日本海沟北西西向的俯冲挤压作用所控制，其主压应变以近东西向压缩为主，日本东北地区的运动方向与太平洋板块的运动方向大体一致.但是，临近地震前（震前）日本东北地区的运动方向发生了很大变化，震前30天的连续GPS观测结果显示，速度场的优势方向经常变换，间歇性地出现与太平洋板块运动方向相反的情况.这意味着震前孕震区的力学状态发生了很大的改变.这种变化可能与震前破裂成核或慢滑移及慢地震等过程有关，这些过程将加速或促进大地震的发生，从而为大地震的发生准备了力学条件.值得特别强调的是，这些现象都是可以通过直接观测能够发现的大地震之前的异常现象.由此可见，加密GPS站点进行连续观测，寻找震前变形异常区以及探索异常的物理机制对于地震预测预报有重要的科学意义.
关键词: 2011年日本东北M_W9.0大地震/
GPS连续观测/
震前变形/
地应变率场/
地震预测

Abstract:It is important to study dynamic processes of the preseismic phase in order to make a successful earthquake prediction. However, the stress regime and the dynamic evolution in the seismogenic zone remain unclear due to the insufficiency of observation data. The 2011 M_W9.0 Tohoku-Oki, Japan, earthquake occurred in the highest density of GPS observation stations in the world, which provided a rare opportunity to study the inter-and pre-seismic deformation. In this paper, we will calculate velocity field and strain rates, respectively, in Tohoku district, Japan, by means of continuous GPS measurement data. By comparison, it is found that the strain state in Tohoku district before the M_W9.0 mainshock is much different from that in interseismic period of time in which the deformation is mainly controlled by the westward subduction of the Pacific Plate in the Japanese trench, and the principal strain rate is dominant with nearly east-west compression, with the direction of movement in Tohoku being broadly in line with that of the Pacific Plate. In contrast, the movement of the Tohoku district is changed much prior to the M_W9.0 main event. The predominant direction of velocity field used to vary within 30 days before the mainshock (preseismic), with sporadic eastward movement which is opposite to the movement of the Pacific plate, suggesting that the stress regime in preseismic phase had changed greatly. This change may be associated with processes such as rupture nucleation, slow slip event and/or slow earthquakes, which may accelerate or trigger the main earthquake and prepare mechanical conditions for the occurrence of large earthquakes. Particularly, we should note that these kinds of phenomena can be detected by direct observation before mainshock, which could be used as seismic precursor in earthquake prediction. Therefore, it is of great scientific significance for the prediction of strong earthquakes to search for the abnormal deformation zone and to study dynamic mechanisms based upon densely deployed continuous GPS sites.
Key words:2011 Tohoku-Oki earthquake/
GPS measurements/
Preseismic deformation/
Strain rate field/
Earthquake prediction



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