Laboratory Studies of Earthquake Dynamics

California Institute Of Technology, Pasadena CA

Investigators

Abstract

EAR-0207873 Ares J. Rosakis Highly instrumented, real-time, dynamic idealized experiments are being used to model earthquakes in the laboratory towards a comprehensive understanding of the basic physical phenomena governing earthquake rupture. Laboratory experiments are performed by creating idealized two-dimensional models made of Homalite-100 or polycarbonate. These materials are birefringent, enabling the use of the optical technique of dynamic photoelasticity. Photoelastic fringe patterns are captured and recorded throughout experimental events by high-speed photography (2 million frames per second), enabling the inference of real-time full-field stress field evolution. A custom high-speed infrared camera (1 million frames per second) is also being used to image thermal fields due to rupture. Dynamic specimen loading is accomplished by gas gun fired projectile impact or by an exploding wire system. Specific areas of study are: (1) nature of rupture propagation (crack-like vs. pulse-like); (2) experimental verification of the achievable range of rupture speed (limited to ~0.8 times the material's shear wave speed vs. supershear); (3) determination to what extent differences in properties (e.g., wave speeds) across inhomogeneous crustal faults promote directionality of rupture; (4) conditions of rupture across step-overs or jogs in en echelon faults (e.g., successive triggering, jumping, or slowing down of ruptures); (5) investigation of whether ruptures incident on fault bends or branches get transmitted, slow down, arrest, or bifurcate creating new fault surfaces; (6) nature of frictional heat dissipation, asperity heating, local melting, and lubrication along active faults.