震源区的断层构造与震源应力积累过程关系的实验研究

EXPERIMENTAL STUDY ON THE RELATION BETWEEN THE STRUCTURAL FORM OF FAULTS IN EARTHQUAKE SOURCE AND ITS STRESS ACCUMULATION PROCESS

摘要:

本实验研究了地壳内对压组合构造和对张组合构造中垂断层蠕滑,破裂错动时对主震断层(底断层)应力积累过程的影响,并结合实际地震活动中的一些现象进行了讨论。所得结论如下:
1.当垂断层蠕滑时,对压组合构造中垂直于底断层的压应力增大,它可以延迟主震发生但增大发震的能量;对张组合构造中垂直于底断层的压应力减小,剪应力略有增大,因而可以促使主震发生。
2.如果垂断层某一部分为原来锁住的愈合断层或为完整介质,当其突然破裂错动时,可以使对张组合构造中的底断层的剪应力突然增大,同时压应力减小,因此前震序列中这类垂断层上的较大前震可看作底断层上主震即将来临的信号。
3.由垂断层破裂前后单轴压力不变和位移不变的实验结果说明了地壳中主震断层应力集中的过程。
4.底断层的主震破裂可以使处于引张状态的垂断层上余震发育甚至发生强余震。
本文还应用实验结果对前震活动的条带现象进行了解释,这将有助于判定对压组合构造中主震的断层面。

Abstract:

There are two combinatory structural forms of faults in the crust. The main faults of them(called the bottom faults)are respectively borne press stress and tention stress when the faults perpendicular to the main faults (called the vertical faults)creep or fracture. The former is called the Model P structure for short, the later the Model T structure. This paper has studied experimentally the effects when the vertical faults creep or fracture on the process of stress accumulation at the main faults and discussed the results with some phenomena in the seismic activity.
1. When the vertical fault in the Model P structure creeps, the press stress perpendiuclar to the bottom fault increases, it can delay the occurrence of the main earthquake and increase the energy of this earthquake; In the Model T structure the press stress decreases and the shear stress on the bottom fault increases a little, it can urge the occurrence of the main earthquake.
2. If a part of the vertical fault is a locked and healed fault or intact medium and when it fractures, it can suddenly increase the shear stress and decrease the press stress on the bottom fault in the Model P structure. So the larger foreshocks on this type of vertical fault can be considered a sign that the main earthquake on the bottom fault is coming.
3.The experimental results under the condition that the unixal pressure or the displacement is constant indicate the stress accumulation process on the main earthquake fault.
4. The fracture of main earthquake on the bottom fault can develop the aftershocks on the vertical fault and even causes great aftershocks.
5. The phenomenon that the foreshocks of some earthquakes scatter on a belt has interpreted. It is helpful for deciding he fault plan of the main earthquake in the Model P structure.