Laboratory Studies of Earthquake Dynamics

EAR-0207873 Ares J.Rosakis高度仪表化的、实时的、动态的理想化实验正被用于在实验室中模拟地震，以全面了解地震破裂的基本物理现象。实验室实验是通过创建由Homalite-100或聚碳酸酯制成的理想化的二维模型来进行的。这些材料是双折射的，可以使用动态光弹性的光学技术。在整个实验过程中，通过高速摄影(每秒200万帧)捕捉和记录光弹条纹图案，从而能够实时推断全场应力场的演变。一台定制的高速红外摄像机(每秒100万帧)也被用来拍摄由于破裂而产生的热场。动态试件加载是通过气枪发射的弹丸撞击或爆炸钢丝系统来完成的。具体的研究领域是：(1)破裂传播的性质(裂隙状与脉冲状)；(2)破裂速度可达到的范围的实验验证(限于材料剪切波速度与超剪切的~0.8倍)；(3)确定跨不均匀地壳断层的性质差异(例如，波速)在多大程度上促进破裂的方向性；(4)跨越梯形断层的跨步或转折的破裂条件(例如，连续触发、跳跃或减缓破裂)；(5)研究断层弯曲或分支上的破裂是否传播、减速、停滞或分叉形成新的断裂面；(6)沿着活动断层的摩擦散热、粗糙加热、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.