南北地震带南段震源空间分布特征及其构造意义  

Hypocentres Spatial Distribution and Its Tectonic Significance in Southern Section of the North-South Seismic Belt,China

作　　者：罗文行[1,2] 胡祥云[3] 李德威[1,2] 蔡建超[3] 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]中国地质大学青藏高原研究中心,武汉430074 [3]中国地质大学地球物理与空间信息学院,武汉430074

出　　处：《吉林大学学报（地球科学版）》2012年第6期1944-1958,共15页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40974040);国家深部专项(SinoProbe-01-03-02);中国地质调查局项目(1212010914036)

摘　　要：大陆浅源地震震源空间分布可以看作是一种地球物理特征,大量震源的空间位置数据可用来刻划大陆地壳结构。通过研究南北地震带南段震源的空间分布特征,发现研究区震源深度分布在横向上的疏密变化与地质构造特征相对应。剖面震源分布等密度图显示,中、下地壳不同深度广泛分布着多震层。多震层的分布与地壳低速、低阻层具有相关性,多震层一般位于低速、低阻层的上方。中地壳层次的低速、低阻层很可能是壳内滑脱层,是韧性下地壳与脆性上地壳发生拆离解耦的构造层次;下地壳低速、低阻层是部分熔融、含流体的韧性流变层;壳内多震层的构造属性应是上地壳硬的脆性层,容易发生突然破裂,产生地震。低速、低阻层是大陆板块内部上地壳脆性层构造过程的主控因素,包括对大陆内部浅源地震的控制;因此,在低速、低阻层之上往往形成多震层,越是活动性强的低速、低阻层,其上多震层震源密度越高。南北地震带南段不同层圈和块体之间的差异运动控制了其地壳层次的构造活动,包括大量地震的发生,其中,下地壳流层与上地壳脆性层的差异运动在中地壳层次发生剪切拆离是最重要的因素。Numerous hypocenters＇ spatial data were used to characterize the crustal structure in the southern section of the North-South seismic belt.The results show a variation,corresponding to the tectonic features of the distribution of hypocenters＇ density along latitudes in study area.According to the Hypocenters＇ density distribution on the profiles,seismogenic layers distribute widely in middle and lower crust.Spatial distribution of hypocenters can also be considered as a geophysical feature of continental crust.It is found that the seismogenic layers are usually at the top of low velocity and resistivity layers,which are assumed to be detachment shear zones between ductile lower crust and brittle upper crust.The low velocity and resistivity layer are possibly related with partial melting,rheological fluid containing etc.Seismogenic layer is corresponding to the hard brittle upper crust,which is prone to result in sudden ruptures and earthquakes.As a result,the more active of the low-velocity resistivity layer,the higher the density of hypocenters of the seismogenic layer.Tectonic activities,including tremender earthquakes,are controlled by differential movements between different layers and blocks in the crust of southern section of the North-South seismic belt,and the most important factor is the differential movement between flowable lower crust and brittle upper crust which occurred in the detachment shear zone in middle crust.

关 键 词：地壳结构 震源分布 多震层 南北地震带 构造 

分 类 号：P631[天文地球—地质矿产勘探]