| 2017年九寨沟MS7.0地震对周围地区的静态应力影响 |
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| 引用本文： | 靳志同,万永革,刘兆才,黄骥超,李瑶,杨帆.2017年九寨沟MS7.0地震对周围地区的静态应力影响[J].地球物理学报,2019,62(4):1282-1299. |
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| 作者姓名： | 靳志同 万永革 刘兆才 黄骥超 李瑶 杨帆 |
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| 作者单位： | 1. 中国地震局地球物理研究所, 北京 100081;2. 防灾科技学院, 河北三河 065201 |
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| 基金项目： | 河北省廊坊市科技计划项目（2016011011）、国家自然科学基金（41674055）、河北省地震局地震科技星火计划项目（DZ20170109001）联合资助. |
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| 摘 要： | 基于九寨沟MS7.0地震的破裂模型及均匀弹性半空间模型，本文计算了该地震在周围主要活动断层上产生的库仑应力变化、在周围地区产生的应力场和位移场和同震库仑应力变化对余震的触发.结果表明：（1）九寨沟地震造成虎牙断裂中段库仑破裂应力有较大增加，已经超过0.01 MPa的阈值，虎牙断裂北段、塔藏断裂中段和岷江断裂北段北部的库仑破裂应力有较大降低，因此尤其要注意虎牙断裂中段的危险性.（2）水平面应力场在该地震震中东西两侧增加（拉张），张应力起主要作用.在震中南北两侧降低（压缩），压应力起主要作用.从水平主压和主张应力方向来看，均呈现出条形磁铁的磁场形态.从剖面上的应力场来看，在上盘的面膨胀区域内，大部分点的主张应力方向与地表是垂直的，在其他区域内，主张应力和主压应力均以震中为中心，向外呈辐射状.（3）从地表水平位移场来看，震中东西两侧物质朝震中位置汇聚，南北两侧物质向外流出，在震中处的最大水平位移量达43 mm.从地表垂直位移场来看，震中南北两侧出现明显的隆升，隆升最大值达56.8 mm.震中东西两侧出现明显的沉降，沉降最大值达74.5 mm.从剖面的位移场来看，九寨沟地震为左旋走滑地震，且有一定的正断成分.由分析可以推测该断层破裂在大致22~26 km的深度上就截止了.并推测下盘物质运动的动力来自震源北东东方向（四川块体）深度在6~30 km的下盘下层物质，上盘物质运动的动力来自震源北西西方向（巴颜喀拉块体）深度在0~6 km的上盘上层物质.（4）通过计算不同深度上主震对余震的触发作用可知，主震后的最大余震受到了主震的触发作用，多数其他余震也受到主震的触发作用.主震的发生促使了库仑应力增加地区余震的发生，抑制了一部分库仑应力减少地区余震的发生.
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| 关 键 词： | 九寨沟地震 震源破裂模型 库仑应力 应力场 位移场 |
| 收稿时间： | 2018-01-23 |
The static stress triggering influences of the 2017 MS7.0 Jiuzhaigou earthquake on neighboring areas |
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| JIN ZhiTong,WAN YongGe,LIU ZhaoCai,HUANG JiChao,LI Yao,YANG Fan.The static stress triggering influences of the 2017 MS7.0 Jiuzhaigou earthquake on neighboring areas[J].Chinese Journal of Geophysics,2019,62(4):1282-1299. |
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| Authors: | JIN ZhiTong WAN YongGe LIU ZhaoCai HUANG JiChao LI Yao YANG Fan |
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| Institution: | 1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;2. Institute of Disaster Prevention, Sanhe Hebei 065201, China |
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| Abstract: | Based on the rupture model of the 2017 Jiuzhaigou MS7.0 earthquake and a homogeneous elastic model in the half space, we calculated the Coulomb stress changes on the active faults near the earthquake region, the stress field, the displacement field and the static stress triggering effect on the aftershocks.Results shows that (1) the Coulomb stress increases in the middle of the Huya fault, which exceeds the threshold value 0.01 MPa, and decreases in the north of the Huya fault, the middle of the Tazang fault and the north of the Minjiang fault. So the seismic risk of the middle Huya fault should receive more attention. (2) The horizontal stress increases in the west and east of the earthquake, and decreases in the north and south of the earthquake. The principal extensional stress and the principal compressive stress are respectively like the form of a magnetic field produced by a bar magnet. (3) From the horizontal displacement on the ground, the material in the eastern and western part of the Jiuzhaigou earthquake moves towards the epicenter, and the material on both sides of the north and south of the earthquake flows outward from the epicenter. The maximum horizontal displacement at the epicenter reaches 43 mm. From the vertical displacement field, there are obvious uplift in the north and south sides of the epicenter with a maximum of 56.8 mm. There is also obvious subsidence in the east and west sides of the epicenter with a maximum of 74.5 mm. From the displacement profile, the Jiuzhaigou earthquake is a left-lateral strike-slip event with a certain normal faulting component. At depths of 22~26 km, the fault is stopped. We hypothesize that the material of footwall of the fault provided the driving force for the movement, which is in the NEE direction of the earthquake (Sichuan block), and at the depth between 6~30 km. The hanging wall of the fault provided the kinetic energy for movement, which is in the NWW direction of the earthquake (Bayankala block), and at the depth between 0~6 km. (4) Calculation of the triggering effect of the main earthquake on the aftershocks shows that the largest aftershock was triggered by the main shock, and most other aftershocks were also triggered by the main shock. In the region of increasing Coulomb stress, there are more aftershocks. In the area of the Coulomb stress reduction, the aftershocks are relatively fewer. |
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| Keywords: | 2017 Jiuzhaigou earthquake Earthquake rupture model Coulomb stress Stress field Displacement field |
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