天然地震形成的一种机制:地壳结构不稳定性  

Crustal structural instability: An earthquake mechanism

作　　者：王腾飞[1] 黄少英[2] 王兆国[3,4] 程日辉[1] 王典[5] 肖中尧[2] 能源[2] 杨宝俊[5] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国石油塔里木油田勘探开发研究院,库尔勒841000 [3]西北大学大陆动力学教育部重点实验室,西安710069 [4]西北大学地质学系,西安710069 [5]吉林大学地球探测科学与技术学院,长春130026

出　　处：《科学通报》2015年第28期2765-2773,共9页Chinese Science Bulletin

基　　金：中国石油天然气集团公司"十二五"科技攻关项目(041011080018)资助

摘　　要：对于天然地震的成因研究多关注于板块相互作用以及流体、断裂等因素.震区地壳结构本身的不稳定性是发生地震的重要因素.伽师地区位于塔里木盆地西端,为塔里木地块、天山造山带、西昆仑造山带、帕米尔构造结的交接部位,具有典型的地壳结构不稳定性,地震频发.地震宽角反射/折射、近垂直反射等地震资料显示伽师地区地壳结构具有特殊的不稳定性.地震宽角反射/折射资料提供了盆地约75 km以上的二维速度结构剖面,地壳速度结构较为复杂,可以识别出高速块体和低速块体相间与堆叠的形态.近垂直地震反射剖面展示了20 s双程到时深度以上更为精细的结构特征,盆地盖层为成层性较好的反射,反射事件C,D构成了地壳之下的稳定带,而反射事件A,B,E则为地壳不稳定结构.建立了伽师地区地壳结构不稳定性的模型,地壳高速块、低速块(即刚性强、弱)相间并堆叠构成的不稳定带置于反射事件C,D构成的稳定带之上,挤压作用与近垂直的隐伏断裂加剧了这种不稳定性.地壳结构不稳定是导致天然地震的重要因素,同样表现存在于日本列岛以及鄂尔多斯盆地等地.Regional crustal structure instabilities are potentially a significant cause of earthquakes, although current research focuses on other causes such as interactions between tectonic plates and the existence of fluids or faults. The Jiashi area, located at the junction of the Tarim block, the Tianshan orogenic belt, the West Kunlun orogenic belt, and the Pamir syntax, is subject to frequent earthquakes. Wide-angle reflections and refractions and near-vertical seismic reflection profiling data show that the crustal structure of the Jiashi area bears a special instability. The velocity distribution at subsurface depths above ~75 km suggests that the crust is structurally complex and hosts a number of high- and low-velocity blocks. Near-vertical seismic reflection profiles show detailed structural characteristics at a depth of 20 s two-way travel time. Sedimentary cover has well-layered reflections, and there is a stable zone highlighted by Reflectors C and D below the unstable zone of Reflectors A, B and E. A model of the crustal structure instability of the Jiashi area has been established, in which an unstable belt is formed by stacking a combination of high- and low-rigidity blocks that are correspondingly represented by high-and low-velocity blocks. They are hosted in the crust, within the stability belt of Reflectors C and D. The structural instability is aided by regional compression and deep crustal faults that intensify regional seismicity. Crustal structural instabilities also exist in the Japanese archipelago and Erdos Basin.

关 键 词：天然地震形成 地壳结构不稳定性 伽师强震带 地震宽角反射/折射 近垂直地震反射 

分 类 号：P315.1[天文地球—地震学]