Abstract
Fault dislocation occurs under certain stress conditions. Based on the mechanical relationship between the direction of crustal stress and the occurrence of fault plane, three criterions of fault strike dislocation trend, dip dislocation trend and fault dislocation or not are put forward, According to these three criteria, the fault slip and the type of slip can be inferred. The parameters that have great influence on the characteristics of fault slip are: fault dip angle, angle between horizontal principal stress and fault strike, depth, lateral pressure coefficient, internal friction angle and cohesion of fault plane. Fault slip is more likely to occur in the environment of high deviation stress, low friction angle and dip angle of about 40°. Fault rupture is a point-to-surface and deep-to-shallow process. When the criterion f2 of the local position of the fault is greater than 0, it will lead to the slip of the nearby fault. When the slip range of the fault extends to the surface, it will cause large earthquakes with large-scale surface rupture. The theoretical calculation is basically consistent with the numerical simulation results. According to the theory in this paper, the slip instability state of Longmen Mountain Fault Zone under different stress conditions is calculated, the results show that when the lateral pressure coefficient is greater than 2.5, dislocation occurs in the deep part of the fault.
Highlights
How did the earthquake happen? What are the physical mechanisms of fault dislocation and fracture conduction and energy release? This is one of the pressing problems in seismology (Shearer, 2009; Lu et al, 2014)
The coupling source theory is a hypothesis of source mechanics, which provides a theoretical basis for determining the initial fault dislocation position (Nakano, 1923)
The theory of plate tectonics can explain that earthquakes are caused by the dislocation of plate margin faults (Le Pichon et al, 1973)
Summary
How did the earthquake happen? What are the physical mechanisms of fault dislocation and fracture conduction and energy release? This is one of the pressing problems in seismology (Shearer, 2009; Lu et al, 2014). Whether a fault slips depends on the friction angle and cohesion of the fault plane, and the normal stress value of ABC on the fault plane is |σ O O |. Fault dip angle, principal stress, fault strike angle, and depth are fixed parameters in a certain period of plate movement, while cohesion of fault plane has relatively little influence on fault plane slip. When the friction angle of the fault plane is less than 23◦, f 1 > 0, n < 0, and f 2 > 0, indicating that thrust and sinistral slip occur on the fault. When the friction angle of the fault plane is greater than 23◦, f 1 < 0, indicating that no slip occurs on the fault. Dip angle, angle between horizontal principal stress and fault strike, depth, lateral pressure coefficient, internal friction angle, and cohesion of fault plane. Faults with dislocation generally have the following characteristics: firstly, in high deviational stress environment, if the lateral pressure coefficient is less than 0.1 or more than 2.8, but there is no fault dislocation in the area where the lateral pressure coefficient approaches 1; secondly, the fault is more prone to slip at the dip angle of 40◦; thirdly, the fault surface with low friction angle is more prone to slip
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