断层几何与前兆偏离

Fault Geometry and Departure of Precursors from Epicenter

不同构造部位在变形中所起的作用不同，变形形式与异常类型也不相同。这种差异造成了地震前出现明显异常的地区与未来震中区偏离的现象我们称之为前兆偏离。作者利用最近一些数值模拟与物理模拟结果，揭示在一个区域变形过程中不同构造部位按其作用可把它们分为５种类型：制动单元（或闭锁单元）、错动单元、让位单元、敏感单元和阀单元。文中以５°的拐折断层为例说明不同构造条件下各种单元的空间分布，特别是敏感单元与发震的错动单元的相互关系。这些起着不同作用的构造单元有时可以相互重迭，有时可以相互偏离。当起不同作用的构造单元相互偏离时，就会出现前兆偏离现象。研究表明，不同断层几何下这些单元的空间布局不同，敏感区的位置和表现方式也不同。前兆往往出现在高应力的单元，而地震失稳则发生在易错动的单元。了解这种布局可能有助于我们布置观测台网。

Different tectonic elements may play different roles and their deformation style s and types of anomalies are also different in process of deformation.Such diffe rences may be the cause of the phenomena of the departure of the region with o bvious anomalies from coming epicenter,which are called “departure of precursors from epicenter”.From some new experimental and numerical modeling results,five types of deformation elements are identified according to their roles in the process of deformation in a region.They are the brake (or locked),slip,yield,sensitive,a nd valve elements.Spatial distribution of different elements,especially sensitive and sl ip elements,are discussed by taking bend fault,extension,compression,and complex en echelon faults as examples.These elements with different roles may be overl apped each other in some cases or separated in other cases.It is obvious that fo r different fault geometry,the spatial layout of these elements is different and thus the position and style of possible sensitive element are also different.Un derstanding the relationship may help us with arranging observation network and defining the position of possible events when anomalies appeared.