鄂尔多斯西南缘P波三维Q值层析成像  

Three-dimensional Q Tomography of P-wave Data in the Southwestern Ordos Margin

作　　者：师海阔[1] 张元生[2] 马禾青[1] 马小军[1,3] SHI Haikuo;ZHANG Yuansheng;MA Heqing;MA Xiaojun(Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,Ningxia,China;Lanzhou Institute of Seismology,China Earthquake Agency,Lanzhou 730000,Gansu,China;Institute of Geophysics,China Earthquake Agency,Beijing 100081,China)

机构地区：[1]宁夏回族自治区地震局,宁夏银川750001 [2]中国地震局兰州地震研究所,甘肃兰州730000 [3]中国地震局地球物理研究所,北京100081

出　　处：《地震工程学报》2018年第4期815-825,共11页China Earthquake Engineering Journal

基　　金：中国地震局"三结合"课题(CEA-JC/3JH-163003)

摘　　要：利用国家测震台网数据备份中心提供的2009年1月至2015年11月的地震波形数据,选取震级范围为ML1.8~6.7,震中距小于800km的1 820个地震事件的16 156条Pg波到时数据,对鄂尔多斯西南缘P波三维Q值分布特征进行了研究。结果表明:鄂尔多斯西南缘一系列呈"L"型分布的断裂带上,Q值呈现出比较低的水平;而其两侧地区,Q值相对较高,且分布存在较大差异。研究区内呈现低Q值状态的海原地区和天水—礼县地区存在明显的低阻—低速层,而高Q值的渭源—定西—通渭—西吉地区则在地壳内缺失低阻层。另外,存在明显高热流的渭河盆地和天水—礼县地区,Q值都明显偏低,而其周围地区则Q值较高。沿临潼—长安—富城—蒲城断裂走向,有一条比较显著的垂直形变梯度带和重力变化等值线,水平形变沿此断裂方向呈现条带状变化特征,而该区低Q值的状态反映了Q值分布与地壳大面积的垂直、水平形变及重力变化等存在一定联系。In this study,seismic wave data of January 2009 to November 2015 are collected from China National Seismographic Network,and 16 156 Pg wave travel times from 1 820 seismic events(M L=1.8~6.7 and epicentral distances less than 800 km)are selected to study the 3D Q-value distribution characteristics of P-wave in the southwestern Ordos margin.The results show that Q-values are relatively lower along the fault zones with“L”shape distribution in the southwestern Ordos margin,while on both sides of this zone,the Q-values are higher and vary greatly in their distribution.In the research area,the resistivity and velocity layers are significantly low in the Haiyuan and Tianshui-Lixian regions which have low Q-values,but the Weiyuan-Dingxi-Tongwei-Xiji region,which has higher Q-values,lacks a low resistivity layer.In addition,the Weihe Basin and Tianshui-Lixian region with a high heat flow have low Q-values,but surrounding areas have higher Q-values.There is a significant vertical deformation gradient belt and gravity change isoline along the Lintong-Chang’an-Fucheng-Pucheng fault.Moreover,the distribution of horizontal deformation along the fault is characterized by distinct stripped variations.The low Q-values in this area indicate that Q-value distribution is related to the vertical and horizontal deformations and gravity changes in the crust.

关 键 词：鄂尔多斯西南缘 P波 三维Q值 层析成像 

分 类 号：TU47[建筑科学—结构工程] P315[建筑科学—土工工程]