Laboratory Studies of Earthquake Dynamics

Ares J. Rosakis高度仪器化的、实时的、动态理想化的实验正在实验室中用于模拟地震，以全面了解控制地震破裂的基本物理现象。 通过创建由Homalite-100或聚碳酸酯制成的理想化二维模型来进行实验室实验。 这些材料是双折射的，使得能够使用动态光弹性的光学技术。 通过高速摄影（每秒200万帧）捕获并记录整个实验事件中的光弹性条纹图案，从而能够推断实时全场应力场演化。 一个定制的高速红外摄像机（每秒100万帧）也被用来成像热场由于破裂。 动态试样加载是通过气体枪发射的弹丸冲击或爆炸丝系统来完成的。 具体的研究领域是：（1）破裂传播的性质（裂纹状对脉冲状）;（2）破裂速度的可实现范围的实验验证（限于材料的剪切波速度对超剪切的~0.8倍）;（3）确定性能差异的程度（例如，波速）跨越不均匀的地壳断层促进破裂的方向性;（4）跨越雁列断层中的台阶或颠簸的破裂条件（例如，断裂的连续触发、跳跃或减缓）;（5）调查断层弯曲或分支上的断裂事件是否传播、减缓、停止或分叉，从而产生新的断层面;（6）沿着活动断层的摩擦热耗散、粗糙体加热、局部熔融和润滑的性质。

EAR-0207873Ares J. RosakisHighly 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.