Bimaterial

=[|link]Dynamic Ruptures in Structures with Bi-material Interfaces=

Faulting is a process that disrupts material continuity and creates zones of relatively compliant damaged rock bounded by material discontinuity interfaces. In addition, active faulting over geological times brings into contact materials that were originally separated and are thus likely to have different elastic properties. There are fundamental differences between properties of dynamic ruptures on faults that do or do not separate different elastic solids.

On a planar fault between solids with identical elastic properties, there is no coupling between slip and changes of normal traction. On the other hand, mode II (in-plane) rupture along a material interface generates local changes of normal stress that are proportional to the spatial derivative of slip. This produces dynamic dilation at the tip that propagates in the direction of slip on the more compliant side of the fault and dynamic compression at the tip propagating in the opposite direction.

The magnitudes of these effects increase with the rupture velocity and the degree of velocity contrast across the fault, up to about 30-40% contrast (beyond which the generalized Rayleigh wave speed does not exist). In addition, the dynamic changes of normal stress increase with propagation distance along the material interface due to a dynamic instability that produces a continual transfer of energy to shorter wavelengths during rupture propagation.


 * The following papers provide theoretical results on dynamic rupture in structures with bimaterial interfaces:


 * Ben-Zion, Y., Dynamic Rupture in Recent Models of Earthquake Faults, //J. Mech. Phys. Solids//, **49**, 2209-2244, 2001. [|link]
 * Ben-Zion Y. and Y. Huang, Dynamic Rupture on an Interface Between a Compliant Fault Zone Layer and a Stiffer Surrounding Solid, //J. Geophys. Res//., **107**, Art. No. 2042, DOI 10.1029/2001JB000254, 2002. [|link]
 * Ben-Zion, Y. and Z. Shi, Dynamic rupture on a material interface with spontaneous generation of plastic strain in the bulk, //Earth Planet. Sci. Lett.//, 236, 486-496, DOI: 10.1016/j.epsl.2005.03.025, 2005. [|link]
 * Shi, Z. and Y. Ben-Zion, Dynamic rupture on a bimaterial interface governed by slip-weakening friction, //Geophys. J. Int.//, 165, doi: 10.1111/j.1365-246X.2006.02853.x, 2006.[|link]
 * Brietzke, G. B. and Y. Ben-Zion, Examining tendencies of in-plane rupture to migrate to material interfaces, //Geophys. J. Int.//, in press, 2006.[|link]
 * Ben-Zion, Y., Comment on “The wrinkle-like slip pulse is not important in earthquake dynamics” by Andrews and Harris, //Geophys. Res////. Lett.//, 33, L06310, doi:10.1029/2005GL025372, 2006. [|link]
 * Ben-Zion, Y., A comment on “Material contrast does not predict earthquake rupture propagation direction” by R. A. Harris and S. M. Day, //Geophys. Res. Lett.//, 33, L13310, doi:10.1029/2005GL025652, 2006.[|link]


 * The following papers provide theoretical results on dynamic rupture in structures with bimaterial interfaces, but these papers come to a different conclusion from the above publications, for 2D (mode II) and 3D (mixed mode); that is the following papers, all show how the bimaterial case leads to bilateral rupture propagation:**
 * Harris, R.A., and S.M. Day, Effects of a low-velocity zone on a dynamic rupture, //Bull. Seism. Soc. Am.//, **87**, 1267-1280, 1997.
 * Andrews, D.J., and R.A. Harris, The wrinkle-like slip pulse is not important in earthquake dynamics, //Geophys. Res. Lett.//, 32, L23303, doi:10.1029/ 2005GL023996, 2005.
 * Harris, R.A., and S.M. Day, Material contrast does not predict earthquake rupture propagation direction, //Geophys. Res. Lett.//, 32, L23301, doi:10.1029/2005GL023941, 2005.

bimaterial problem:
 * The following paper provides laboratory results reinforcing the bilateral rupture propagation hypothesis for the


 * Xia, K., A.J. Rosakis, H. Kanamori, and J.R. Rice, Inhomogeneous faults hosting earthquakes in the laboratory: directionality and supershear, //Science//, **308**, 681-684, 2005.

contrast for specific earthquakes that have occurred in California:
 * The following paper tests the ideas of unilateral vs. bilateral rupture propagation caused by a bimaterial


 * Harris, R.A., and S.M. Day, Material contrast does not predict earthquake rupture propagation direction, //Geophys. Res. Lett.//, 32, L23301, doi:10.1029/2005GL023941, 2005.
 * Xia, K., A.J. Rosakis, H. Kanamori, and J.R. Rice, Inhomogeneous faults hosting earthquakes in the laboratory: directionality and supershear, //Science//, **308**, 681-684, 2005.


 * The papers below provide related geological observations:


 * Dor O., T. K. Rockwell and Y. Ben-Zion, Geologic observations of damage asymmetry in the structure of the San Jacinto, San Andreas and Punchbowl faults in southern California: A possible indicator for preferred rupture propagation direction, //Pure Appl. Geophys.//, //Pure Appl. Geophys////.//, 163, 301-349, DOI 10.1007/s00024-005-0023-9, 2006. [|link]
 * Dor O., Y. Ben-Zion, J. Brune and T. K. Rockwell, Pulverized Rocks in the Mojave section of the San Andreas Fault Zone, //Earth Planet. Sci. Lett.//, 245, 642-654, 2006. [|link]