鄂尔多斯块体周缘中小地震震源机制及应力场特征

发布时间：2018-02-21 22:26

本文关键词： 震源机制解 P波初动振幅比鄂尔多斯块体　出处：《大地测量与地球动力学》2017年07期 　论文类型：期刊论文

【摘要】：利用基于P波初动和振幅比反演震源机制解的HASH方法,得到鄂尔多斯块体周缘2008-01~2014-06共1 700个ML2.5以上地震的震源机制解,从中选取结果较为可靠的1 581个地震的震源机制解,将研究区域划分为1°×1°的网格,采用阻尼区域应力反演方法(MSATSI软件)获得了研究区域内中小地震震源机制解特征和应力场图像。鄂尔多斯块体周缘震源机制解类型以正断和走滑为主,应力场反演结果表明,鄂尔多斯周缘应力状态以拉张为主,局部区域存在剪切、挤压。块体北缘和西缘的最大水平主应力优势方位为NE向,一致性较好;块体东缘和南缘的最大水平压应力方向与区域内主要活动构造方向基本平行,东缘最大水平主应力方向从南段的近EW向、NEE向逐渐过渡到NE向,南缘是NWW-SEE和近EW向。通过分析研究区域应力状态和最大水平主应力方向认为,银川-吉兰泰南端近NS向活动断裂的剪切应力状态的出现,是由于近NS向活动断裂在NE向挤压应力作用下发生了右旋剪切运动;块体西南缘NEE向的挤压和剪切的应力状态与青藏块体对鄂尔多斯块体的直接作用,以及六盘山断裂带第四纪以来强烈的挤压性质及左旋走滑运动有关;大同盆地出现局部剪切应力状态可能与盆地下方的火山有关。
[Abstract]:Using the HASH method based on P wave initial motion and amplitude ratio inversion, the focal mechanism solutions of 1 700 or more ML2.5 earthquakes around the Ordos block are obtained. The focal mechanism solutions of 1 581 earthquakes with reliable results are selected. The study area is divided into 1 掳脳 1 掳grids, By using the damped regional stress inversion method (MSATSI software), the focal mechanism solutions and stress field images of the small and medium-sized earthquakes in the studied area are obtained. The main types of focal mechanism solutions around the Ordos block are normal faults and strike-slip, and the stress field inversion results show that, The stress state around Ordos is mainly tensional, and there is shear and compression in the local area. The dominant orientation of the maximum horizontal principal stress in the northern and western margin of the block is NE, and the consistency is good. The direction of the maximum horizontal compressive stress in the eastern and southern margin of the block is basically parallel to the direction of the main active structures in the region, and the direction of the maximum horizontal principal stress in the eastern margin is gradually transitioning from the near EW direction to the NEE direction of the southern segment to the NE direction. The southern margin is in the direction of NWW-SEE and near EW. Based on the analysis of the regional stress state and the maximum horizontal principal stress direction, it is considered that the shear stress state of the NS-direction active fracture near the south end of Yinchuan-Gilantai appears. This is due to the dextral shear movement of the NS-trending active faults under the action of NE compression stress, the stress state of the NEE direction of the southwestern margin of the block and the direct action of the Qinghai-Tibet block on the Ordos block. The strong compressibility and left-lateral strike-slip movement in Liupanshan fault zone since the Quaternary period and the occurrence of local shear stress in Datong basin may be related to the volcanoes in the lower part of the basin.
【作者单位】：中国地震局地球物理研究所;河北省地震局;
【基金】：国家自然科学基金(91214201) 中国地震局地震行业科研专项(201208009) 潜在强震区地震地质灾害调查与风险区划(12120114035501)~~
【分类号】：P315.33

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