Depth dependence of constitutive law parameters for shear failure of rock at local strong areas on faults in the seismogenic crust

Abstract

[1] In the framework of slip-dependent constitutive formulation, which leads to a unifying law that governs not only frictional slip failure at precut interface areas on faults but also shear fracture of intact rock at local strong areas on the faults, a thorough investigation has been made about how the constitutive law (of dimensionless form) for rock failure at local strong areas on faults is affected by seismogenic crustal conditions of effective normal stress, pore pressure, and temperature, on the basis of laboratory data on the shear fracture of granite rock obtained by Kato et al. (2003a) under crustal conditions simulated in the laboratory. It has been revealed how dimensionless constitutive law parameters distinctively vary with depth, depending on the crustal conditions simulated; consequently, the constitutive behavior including the slip-weakening phase also distinctively varies with depth. This behavior in the regime of suprahydrostatic pore pressure clearly differs from that in the regime of hydrostatic pore pressure. The results of this study are suited for implementation in a numerical code, and the constitutive properties of rock failure at local strong areas (called ''asperites'') on faults will be easily assimilated into numerical models of earthquake ruptures for realistic computer simulation.Citation: Ohnaka, M., and A. Kato (2007), Depth dependence of constitutive law parameters for shear failure of rock at local strong areas on faults in the seismogenic crust,

Van Gölü Bölgesi̇nde 2011 Yili Depremleri̇ni̇n Artçi Şok Seri̇si̇ Kirilma Karmaşiğina Yapisal Bağlanti(doğu Anadolu, Türki̇ye)

“…This means that the rupture area of the Van event is a fault-bounded fragmentation barrier (see Toker, 2017 for details). Such a local strong area (e.g., large asperity and/or barrier) is highly resistant to rupture growth on a fault and this area plays a more important role in determining the size of an earthquake than the remainder (e.g., aseismic slip and/or relaxation barrier as proposed by Toker, 2017) of the fault plane, which has little resistance to rupture growth (Ohnaka and Kato 2007;An et al 2010). Moreover, hypocenters and their distributional patterns (e.g., the migration, diffusion, scattering and clusters) are also the consequence of stress redistribution related to the mainshock, occurring as failure along smaller fault asperities (Toker, 2017).…”

Reply to “Comment on ‘Earthquake cycles and physical modeling of the process leading up to a large earthquake’”

“…As discussed in earlier papers (Ohnaka, 2003(Ohnaka, , 2004Ohnaka and Kato, 2006), real faults embedded in the seismogenic crust are inherently inhomogeneous, and fault inhomogeneity has profound implications for the rational constitutive formulation for earthquake ruptures. The earthquake rupture process at shallow crustal depths is not a simple one of frictional slip failure on a precut weak fault but, rather, a more complex process, including the fracture of initially intact rock at local strong areas (called "asperities") on an inhomogeneous fault (see Ohnaka and Kato, 2006).…”

“…The constitutive law for real earthquake ruptures must, therefore, be formulated as a unifying law that governs not only frictional slip failure at precut-interface (or frictional contact) areas on faults but also shear fracture of intact rock at local, strong areas on the faults. This is a very important requirement to be met when we rationally formulate the constitutive law for real earthquake ruptures (see Ohnaka, 2004;Ohnaka and Kato, 2006).…”

“…It is therefore obvious from physical viewpoints how the constitutive law for real earthquake ruptures should be formulated, and what it ought to be (see Ohnaka, 2004;Ohnaka and Kato, 2006).…”

“…The earthquake rupture process at shallow crustal depths is not a simple one of frictional slip failure on a precut weak fault but, rather, a more complex process, including the fracture of initially intact rock at local strong areas (called "asperities") on an inhomogeneous fault (see Ohnaka and Kato, 2006). The constitutive law for real earthquake ruptures must, therefore, be formulated as a unifying law that governs not only frictional slip failure at precut-interface (or frictional contact) areas on faults but also shear fracture of intact rock at local, strong areas on the faults.…”