PHYSICAL MECHANISM OF MAJOR EARTHQUAKES BY EARTHQUAKE CASES ANALYSIS

Abstract

Understanding the physical mechanism of major earthquakes is very important for earthquake prediction and its disaster reduction. The mainstream hypotheses on earthquake mechanism are reviewed in this paper. It is pointed out that the elastic rebound and stick-slip hypotheses, both of which are usually used to explain the mechanism of shallow earthquakes, have some serious drawbacks, and that such hypotheses explaining the mechanism of intermediate and deep earthquakes as the dehydration embrittlement, phase transition instability, shear melting and anticrack-associated faulting, are inconsistent with some observation data. Thus, it is necessary to establish a new hypothesis or theory of earthquake mechanism. The brittle failure theory of multiple locked patches in a seismogenic fault system developed by us since 2010 is introduced in the present study. It is stated by the theory that the progressive failures of locked patch result in the occurrence of earthquakes due to the fault movement. Hereafter, the significant earthquakes occurred at its volume expansion and peak strength points are referred to as characteristic ones. The earthquake cases indicate that the seismogenic processes of shallow, intermediate and deep characteristic earthquakes can be well explained by the theory. We emphasize that both the elastic rebound and stick-slip hypotheses contain the same implicit assumption that there exist locked patches in the seismogenic faults, and that the source body of deep earthquakes is with appropriate environment conditions leading to brittle failures. Moreover, some controversial issues, such as seismic stress drop much less than that of rock failure in the laboratory test, heat flow paradox and Self-Organized Criticality (SOC), are discussed and can be reasonably explained by the theory. The present study shows that the physical mechanism of major earthquakes is attributed to the brittle failures of locked patches.