地震孕育机制与破裂机制的研究

在理论上得出地震孕育发生的普遍物理机制是:地震前孕震区在垂直向会逐步形成、发展弹性的“拉疏隆起—压缩凹陷”的不稳结构,在水平向也多会形成对称相间分布的两个弹性压缩区及两个弹性拉疏区。应变的“压缩区与拉疏区同时产生、对应存在、共为一体”的这种双向应变结构是地壳构造运动中形成孕震体与非孕震体的根本区别,也是能用以首先找到孕震地区的主要依据;地震的破裂机制是:孕震体形成的双向应变结构,构成了应力集中后的失稳与剪切破裂的必要条件,当初始破裂后,就会引起压缩区与拉疏区发生逆转性的弹性膨胀与收缩的相互配合而不断提供位错空间,从而能使应力与破裂快速地传递与扩张。这一地震孕育与破裂机制的认识,几乎能解释绝大多数的地震前兆现象及震时震后的冒砂、冒水与断层的破裂、错动现象。

STUDY ON MECHANISM OF EARTHQUAKE PREPARATION AND FRACTURE

 A general physical mechanism of earthquake preparation and occurrence discussed theoretically in the paper is that an elastic“pull-loosened uplift—compressional depression”unstable structure is formed and developed gradually in vertical direction in a seismogenic zone before earthquake and two elastic compressional zones and two elastic pull-loosened zones symmetrically and alternatively distributed can be also formed in horizontal direction. This bi-directional strain structure in which the strain“compressional and pull-loosened zones are formed synchronously and exist oppositely and together form an entirety”is an essentially difference for formation of seismogenic body and non-seismogenic body produced by the crustal tectonic movement and also the main basis for finding the seismogenic zone. The
mechanism for seismic fracturing is that the bi-directional strain structure formed in a seismogenic zone is the necessary condition for instability and shear fracturing after stress concentration. An initial fracture after its formation can cause the compressional zones and pull-loosened zones to reverse expand and contract and in a coordinated pattern to uninterruptedly provide a dislocation space, and hence to make the stress and fracture to rapidly transmit and extend. This knowledge of the mechanisms for earthquake preparation and fracturing can be used to explain most of the seismic precursory phenomena and sand blow, water ejection, and fault rupture and dislocation.