Effects of prestress state and rupture velocity on dynamic fault branching

[1] We consider a mode II rupture which propagates along a planar main fault and encounters an intersection with a branching fault. Using an elastodynamic boundary integral equation formulation, allowing the failure path to be dynamically self-chosen, we study the following questions: Does the rupture initiate along the branch? Does it continue? Is the extensional or compressional side most favored for branching? Does rupture continue on the main fault too? Failure is described by a slip-weakening law for which the strength at any amount of slip is proportional to normal stress. Our results show that dynamic stresses around the rupture tip, which increase with rupture velocity at locations off the main fault plane relative to those on it, could initiate rupture on a branching fault. As suggested by prior work, whether branched rupture can be continued to a larger scale depends on principal stress directions in the prestress state and on rupture velocity. The most favored side for branching rupture switches from the extensional to the compressional side as we consider progressively shallower angles of the direction of maximum compressive prestress with the main fault. Simultaneous rupturing on both faults can be activated when the branching angle is wide but is usually difficult for a narrow branching angle due to strong stress interactions between faults. However, it can be also be activated by enhanced dynamic stressing when the rupture velocity is very near the Rayleigh velocity. Natural examples seem consistent with the simulations that we present.

[1]  GEOFFREY KING,et al.  Role of Fault Bends in the Initiation and Termination of Earthquake Rupture , 1985, Science.

[2]  John R. Rice,et al.  The mechanics of earthquake rupture , 1980 .

[3]  E. Hauksson,et al.  Crustal stress field in southern California and its implications for fault mechanics , 2001 .

[4]  H. Aochi,et al.  Spontaneous Rupture Propagation on a Non-planar Fault in 3-D Elastic Medium , 2000 .

[5]  E. Gdoutos,et al.  Fracture Mechanics , 2020, Encyclopedic Dictionary of Archaeology.

[6]  E. Hauksson,et al.  Role of fluids in faulting inferred from stress field signatures , 1999, Science.

[7]  Shuichi Kodaira,et al.  Splay Fault Branching Along the Nankai Subduction Zone , 2002, Science.

[8]  T. Yamashita,et al.  Apparent critical slip displacement caused by the existence of a fault zone , 1996 .

[9]  G. Ekström,et al.  Seismicity and geometry of a 110 km-long blind thrust fault: 1 , 1992 .

[10]  T. D. Rubin,et al.  Relationship of the kickapoo fault to the Johnson Valley and Homestead Valley faults, San Bernardino County, California , 1994, Bulletin of the Seismological Society of America.

[11]  T. Yamashita,et al.  Earthquake rupture complexity due to dynamic nucleation and interaction of subsidiary faults , 1994 .

[12]  R. Sibson.  Stopping of earthquake ruptures at dilational fault jogs , 1985, Nature.

[13]  Nobuki Kame,et al.  Simulation of the spontaneous growth of a dynamic crack without constraints on the crack tip path , 1999 .

[14]  Hideo Aochi,et al.  Effect of normal stress during rupture propagation along nonplanar faults , 2002 .

[15]  J. Rice,et al.  Pore pressure and poroelasticity effects in Coulomb stress analysis of earthquake interactions , 2002 .

[16]  A. Nakanishi,et al.  Crustal structure across the coseismic rupture zone of the 1944 Tonankai earthquake, the central Nankai Trough seismogenic zone , 2002 .

[17]  Geoffrey C. P. King,et al.  Speculations on the geometry of the initiation and termination processes of earthquake rupture and its relation to morphology and geological structure , 1986 .

[18]  Yoshiaki Ida,et al.  Cohesive force across the tip of a longitudinal‐shear crack and Griffith's specific surface energy , 1972 .

[19]  James R. Rice,et al.  Dynamic shear rupture interactions with fault bends and off-axis secondary faulting , 2002 .

[20]  Hideo Aochi,et al.  Three‐dimensional nonplanar simulation of the 1992 Landers earthquake , 2002 .

[21]  J. Rice,et al.  The growth of slip surfaces in the progressive failure of over-consolidated clay , 1973, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[22]  Hideo Aochi,et al.  Selectivity of spontaneous rupture propagation on a branched fault , 2000 .

[23]  K. Broberg.  Cracks and Fracture , 1999 .

[24]  Ralph J. Archuleta,et al.  A faulting model for the 1979 Imperial Valley earthquake , 1984 .

[25]  T. Yamashita,et al.  A new light on arresting mechanism of dynamic earthquake faulting , 1999 .

[26]  Charles A. Langston,et al.  The February 9, 1971 San Fernando earthquake: A study of source finiteness in teleseismic body waves , 1978, Bulletin of the Seismological Society of America.

[27]  T. Heaton,et al.  Generalized ray models of the San Fernando Earthquake , 1979 .

[28]  Raul Madariaga,et al.  Dynamic faulting under rate-dependent friction , 1994 .

[29]  D. J. Andrews,et al.  Rupture velocity of plane strain shear cracks , 1976 .

[30]  G. King,et al.  STATIC STRESS CHANGES AND THE TRIGGERING OF EARTHQUAKES , 1994 .

[31]  K. W. Neale,et al.  Dynamic fracture mechanics , 1991 .