Effects of shear heating, slip‐induced dilatancy and fluid flow on diversity of 1‐D dynamic earthquake slip

Abstract

We theoretically study effects of thermal pressurization, slip-induced dilatancy and fluid flow on slip evolution assuming 1-D fault model. We generalize the analysis made in our former papers by introducing an upper limit for the inelastic porosity evolution. The expression for nondimensional parameter T a , which is related to the upper limit, is derived in the present paper. We find that the parameter T a together with two nondimensional parameters S u and S u ′ derived in our former papers completely determine the qualitative nature of system behavior once the initial condition is given. For example, changes in S u and T a generate two qualitatively different slip behaviors, both of which can be models for ordinary earthquake. The slip is accelerated with time after experiencing an initial deceleration in one of them, while the slip ceases after monotonic deceleration in the other. The initial slip deceleration observed in the former case may be interpreted as a dynamic event preceding the main shock in seismological observations. We mathematically derive the expression for the ranges of the nondimensional parameters in which the above two slip behaviors appear. Slow earthquakes are also modeled in the same framework, and nonzero values of the nondimensional parameter S u ′ together with relatively large values of S u and T a are found to contribute to the generation of such slow earthquakes. The mathematical framework constructed here can be applied to understanding of some other natural phenomena such as a kind of reaction-diffusion system.

Emergence and seismological implications of phase transition and universality in a system with interaction between thermal pressurization and dilatancy

“…It should be emphasized that when the fluid pressure increases (decreases), the frictional stress decreases (increases) due to a reduction (increment) in the effective normal stress acting on the fault plane, inducing the slip velocity increase (decrease). The competition between thermal pressurization and dilatancy induces complex feedback in the slip behavior, which can explain many aspects of the dynamic earthquake slip process (e.g., Suzuki and Yamashita (2014) [6], referred to as SY14 below). However, this system is not yet researched from the viewpoint of nonlinear mathematics, particularly with regard to the behaviors of attractors.…”

“…Such fluid pressure elevation induces a decrease in the normal stress acting on the fault plane, leading to frictional stress decrease and slip acceleration. Many studies, in- * t-suzuki@phys.aoyama.ac.jp cluding a sequence of studies by the author, have considered another interaction between thermal pressurization and dilatancy (referred to as ITPD below) [6,7,[9][10][11][12][13]. The dilatancy is slip-induced inelastic pore creation, leading to fluid pressure decrease and slip deceleration.…”

Ordinary and Slow Earthquakes Reproduced in a Simple Continuum System With Stochastic Temporal Stress Fluctuations

“…Dynamic rupture processes may substantially change the physical conditions of a fault system, including the fault geometries, through various processes such as pore fluid flow. Even a simple nonlinear system of pore‐fluid and heat is known to yield various behaviors as a result of just a slight variation in the initial condition (Suzuki & Yamashita, ). Multiple nonlinear physical processes act on a given fault, including those related to viscosity, off‐fault damage, pore fluids, and thermal activation, and the interactions between these processes make the rupture evolution inherently unpredictable over longer timescales, thereby introducing deterministic chaos to the fault system.…”

Characteristic Sensitivity of Turbulent Flow within a Porous Medium under Initial Conditions

“…Particularly, an increase (or decrease) in the fluid pressure induces decrease (or increase) in the effective normal stress that acts on the fault zone, thereby decreasing (or increasing) friction stress and increasing (or decreasing) slip velocity. Many processes, such as thermal pressurization and dilatancy, are the presumed mechanisms causing fluid pressure variation [11][12][13][14][15][16][17][18]. Additionally, the increase (decrease) in the fluid pressure in the fault zone induces the fluid outflow to (inflow from) the outside of the fault zone because of the emergence of the gradient of the fluid pressure profile along the direction normal to the fault zone.…”