Spontaneous Complex Earthquake Rupture Propagation

Abstract

The historical development of spontaneous rupture propagation, starting from the landmark paper of Griffith in 1920, through to the late 1980s is traced, with particular emphasis on the work carried out at MIT in the 1970s by K. Aki and his co-workers. Numerical applications of Kostrov's method for planar shear cracks were developed by Hamano, Das and Aki. Simultaneously at MIT, Madariaga considered the radiated field of a dynamic shear crack. The further development of these ideas, for example, three-dimensional spontaneous planar faulting models, continued through the 1980s. Major insight into the maximum possible rupture speeds for earthquakes developed, with the acceptance of the theoretical possibility of supersonic rupture speeds for faults with cohesion and friction, the theoretical developments spurring the search for such observations for earthquake ruptures. Possible mechanisms by which faults stop were elucidated. It was shown that a propagating rupture can jump over barriers for cracks with a cohesive zone at its tip. Complex faulting models, namely the barrier and asperity models, and their associated radiated field developed. In the late 1980s, it was shown that ''dynamic'' or transient asperities can develop during the complex rupturing process. Even seemingly relatively simple physical situations, can lead to such complex rupturing processes that the usual idea of ''rupture velocity'' needs to be abandoned in those cases. Some of the work initiated by Aki and his co-workers, such as the details of the transition from sub-Rayleigh to super-shear speeds in inplane shear mode, and the behavior of the cohesive zone size as the crack extends, still remains the subject of research today.

Evidence for self‐similar, triangular slip distributions on earthquakes: Implications for earthquake and fault mechanics

“…Profiles have been normalized by both L and D max with some of them being flipped so that maximum slip is at right [from Manighetti et al, 2001Manighetti et al, ]. 2002Das, 2003], we have here compiled them for many more earthquakes than has been done before. That compilation reveals that most earthquakes initiated at or close to an intersection between two strongly oblique faults (in strike and in some cases also in dip), one eventually broke during the earthquake.…”

“…Zones of large slip (relative to the rest of the slip on the fault) on earthquake fault surfaces are usually defined as “asperities” [e.g., Madariaga , 1979; Lay and Kanamori , 1981; Das and Kostrov , 1983; Mendoza , 1993; Ruff and Miller , 1994; Somerville et al , 1999; Papageorgiou , 2003; Das , 2003]. In section 5, we will discuss how these asperities relate to geological structures.…”

“…ES06 describes the main features that were observed about where the 56 listed earthquakes initiated (column 5), had their maximum slip abruptly dropping to zero (column 6), and had their slip gently tapering to zero (column 7). Note that while aspects of these observations have been touched on by a number of authors [e.g., Segall and Pollard , 1980; King , 1986; Sibson , 1985, 1986; Scholz , 1990; Harris et al , 1991; Harris and Day , 1993; Kame and Yamashita , 1999; Oglesby and Day , 2001; Harris et al , 2002; Das , 2003], we have here compiled them for many more earthquakes than has been done before. That compilation reveals that most earthquakes initiated at or close to an intersection between two strongly oblique faults (in strike and in some cases also in dip), one eventually broke during the earthquake.…”

Cracklike Processes within Frictional Motion: Is Slow Frictional Sliding Really a Slow Process?

“…The application of spatially nonuniform loading (i.e., shear applied to the system at the trailing edge of the slider) leads to this precursor evolution, which dynamically generates a highly nonuniform contactarea profile. 32 Because the amount of contact area determines the fracture toughness, local nonuniformity of A will directly affect both the nucleation 3,39,40 and arrest 41,42 mechanisms that promote interface weakening and eventual failure (leading to sliding). These are intrinsically important fundamental questions with ramifications to both materials science and earthquake dynamics.…”

The Challenge of Defining Upper Bounds on Earthquake Ground Motions

“…If the spatial variability of rupture velocity across the fault plane is considered, the definition of the maximum per missible values of this quantity becomes even more of an issue. Das (2003) discussed the development of proposals regarding maximum permissible rupture speeds, addressing in particular the issue of whether rupture velocity can exceed shear-wave velocity. The answer to this problem is to a large extent dependent on the assumptions of the model that is used.…”