铅垂断层向错引起的地表重力变化

利用直立长方体组合模型以及坐标旋转理论,对铅垂断层向错引起的重力变化进行数值模拟,分别计算深度为1、5、10 km的铅垂断层在单一方向上、两个方向上向错引起的地面重力变化。结果表明,当断层在单一方向产生向错时,以左端点为基点的W1、W2向错引起的地面重力变化场均呈现以断层为轴线的对称分布|以中点为基点的W3向错引起的地面重力变化场构成四象限反对称分布。当断层在两个方向上同时产生向错时,以左端点为基点的W1W2向错引起的地面重力变化场呈现以断层为轴线的对称分布,整体显示W2向错起主导作用|以中点为基点的W2W3向错引起的地面重力变化场呈现非对称分布,整体也显示出W2向错起主导作用,断层附近的扭错现象为W3向错的作用。随着断层深度的增加,断层向错引起的地面重力变化值递减,但影响范围逐渐扩大。     

断层向错引起的地表重力变化研究

利用三维角点法以及空间物体旋转的几何变换理论,建立断层向错与地表重力变化的关系,并进行数值模拟计算。选取断层下盘左端点为旋转基点,分析断层埋深和倾角对其向错引起的重力变化的影响。结果表明,断层向错引起的重力变化与断层埋深有明显的相关性,在W1、W2、W3向错模式下,重力变化均表现为随断层深度增加而逐渐衰减;重力变化对断层倾角有着不同的响应。断层运动产生的重力变化空间分布特征与断层的向错模式以及旋转基点的选择有关。     

矩形断层向-位错引起的空间重力变化

针对位错理论难以解释断层面之间的旋转转动的问题,该文基于子断层叠加法,利用经典点源位错理论,得出了矩形断层向-位错引起的空间重力变化。利用C++语言编制了弹性半空间中的矩形断层向-位错正演程序,模拟计算并分析了倾角为90°的矩形断层滑动和转动引起的空间重力变化的分布特征。数值模拟结果显示:断层运动引起的空间重力变化与断层的滑动和转动量大小及断层产状有关,断层滑动和转动越大,引起的地表变形范围和量值就越大;断层转动引起的重力变化大小与断层埋深成反关系,即断层埋深越大,相应的重力变化量值就越小;宏观上,矩形断层位错运动引起的重力变化呈近似对称的特征,而断层向错打破了重力变化图像的对称性。     

Point Sources of Elastic Deformation: Elementary Sources, Static Displacements

Summary. We construct a catalogue of all possible elementary point sources for static deformation in an elastic solid. the familiar double-couples, CLVD's, centres of compression and dilatation, etc., are all members of the complete catalogue. the sources are classified according to the rank of the seismic moment tensor, and according to the weight (or order) of the irreducible tensor representation of the 3-D rotation group. These sources can be classified as belonging to one of three general classes. the static excitation functions are calculated for an infinite, homogeneous, isotropic medium for all these sources. We show that, except for sources belonging to these three general classes, all other sources — which are numerous for the tensors of high rank — are null static sources. That is, sources that do not produce any static displacement outside of the source region. Due to the presence of null sources, an inversion of the static deformation data is non-unique. the expansion of the equivalent-force tensors and the stress glut tensors (or seismic moment tensors) into a set of the symmetric trace-free source tensors is proposed. the sources corresponding to seismic moment tensors of the second, third and fourth ranks are considered in more detail. We identify the third-rank sources with rotational dislocations or disclinations.