A thermal pressurization model for the spontaneous dynamic rupture propagation on a three‐dimensional fault: 1. Methodological approach

Abstract

[1] We investigate the role of frictional heating and thermal pressurization on earthquake ruptures by modeling the spontaneous propagation of a three-dimensional (3-D) crack on a planar fault governed by assigned constitutive laws and allowing the evolution of effective normal stress. We use both slip-weakening and rate-and state-dependent constitutive laws; in this latter case we employ the Linker and Dieterich evolution law for the state variable, and we couple the temporal variations of friction coefficient with those of effective normal stress. In the companion paper we investigate the effects of thermal pressurization on the dynamic traction evolution. We solve the 1-D heat conduction equation coupled with Darcy's law for fluid flow in porous media. We obtain a relation that couples pore fluid pressure to the temperature evolution on the fault plane. We analytically solve the thermal pressurization problem by considering an appropriate heat source for a fault of finite thickness. Our modeling results show that thermal pressurization reduces the temperature increase caused by frictional heating. However, the effect of the slipping zone thickness on temperature changes is stronger than that of thermal pressurization, at least for a constant porosity model. Pore pressure and effective normal stress evolution affect the dynamic propagation of the earthquake rupture producing a shorter breakdown time and larger breakdown stress drop and rupture velocity. The evolution of the state variable in the framework of rate-and state-dependent friction laws is very different when thermal pressurization is active. In this case the evolution of the friction coefficient differs substantially from that inferred from a slip-weakening law. This implies that the traction evolution and the dynamic parameters are strongly affected by thermal pressurization.Citation: Bizzarri, A., and M. , A thermal pressurization model for the spontaneous dynamic rupture propagation on a three-dimensional fault: 1. Methodological approach,

Off‐fault plasticity and earthquake rupture dynamics: 2. Effects of fluid saturation

“…Therefore we neglect in this study the effects of pore pressure increases or decreases on the slip-weakening response of the fault. Such slip weakening, as conventionally assumed, may in fact be a proxy for much more significant but highly localized pore pressure changes along the fault due to thermal pressurization [Sibson, 1973;Lachenbruch, 1980;Mase and Smith, 1987;Andrews, 2002;Noda and Shimamoto, 2005;Rice, 2006;Rempel and Rice, 2006;Suzuki and Yamashita, 2006;Bizzarri and Cocco, 2006].…”

Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate

“…Shimamoto (2003, 2005) and Spray (2005) observed slip weakening during high slip rate sliding when melting occurred. Thermal pressurization was proposed by Sibson (1973) and modeled by Lachenbruch (1980), Mase and Smith (1987), Andrews (2002), Wibberley and Shimamoto (2005), Bizzarri and Cocco (2006) and Rice (2006) and many others. It is difficult to confirm in the laboratory whether thermal pressurization occurs or not because no footprints of thermal pressurization remain after high-speed slip; all the above studies are based on theoretical considerations.…”

Toward the Formulation of a Realistic Fault Governing Law in Dynamic Models of Earthquake Ruptures

“…The interest is motivated by the fact that fluids play an important role in fault mechanics; they can affect the earthquake nucleation and the earthquake occurrence (e.g., Sibson, 1986;Antonioli et al, 2006), they can trigger aftershocks (Nur & Booker, 1972 among many others) and they can control the breakdown process through the so-called thermal pressurization phenomenon (Bizzarri & Cocco, 2006a, 2006b and references therein). Here we will focus on the coseismic time scale, but we want to remark that pore pressure can also change during the interseismic period, due to compaction and sealing of fault zones.…”

“…Here we will focus on the coseismic time scale, but we want to remark that pore pressure can also change during the interseismic period, due to compaction and sealing of fault zones. The temperature variations caused by frictional heating, ( (Bizzarri & Cocco, 2006a; χ is the thermal diffusivity, c is the heat capacity of the bulk composite and erf(.) is the error function), heats both the rock matrix and the pore fluids; thermal expansion of fluids is paramount, since thermal expansion coefficient of water is greater than that of rocks.…”