高速脉冲加载条件下地震摩擦实验及其地震物理机制的研究

The constitutive frictional relations of a fault-zone during unstable (earthquake) and stable slip strongly affect the style of rupture propagation and seismic radiation. The commonly used constitutive relations were determined by either simple, conceptual models or by adaptation of experimental data derived from steady-state runs. Yet, the earthquake rupture includes time transient of friction-velocity-distance which is neither simple nor steady-state. Recently our slip-pulse experiments revealed similarities to earthquake rupture for the first time in terms of energy rates, transient constitutive properties of fault, weakening-strengthening, wear, heat production, and self-healing. We propose here to systematically simulate earthquake at high velocity, e.g., slip-pulse earthquake, to study frictional phenomena under different loading conditions, and to explore the physical mechanism of earthquake. We expect that implementing this new-design earthquake experiment (slip-pulse loading) could enhance our understanding of earthquake mechanisms and help construct more realistic constitutive relation of friction.

断层破裂（地震）与稳态时的摩擦本构关系强烈影响着断层破裂发育形态以及地震波的传播。目前地震数值模拟最常用的本构模型来自于极其简化的线性弱化模型，或恒速慢度摩擦实验。但是，天然地震即非线性弱化，亦非恒态。我们最近的地震摩擦实验首次指出，脉冲高速加载实验显示出与天然地震破裂更相似的特征：能量释放、断层演化本构特征、弱化-强化、磨损、热能释放及自愈。 我们提出，系统地将地震实验推进到高速，重点研究脉冲型地震的各种摩擦现象，并探索导致脉冲型地震断层弱化的物理机制。我们期望，采用最新的地震实验（脉冲加载），可以提高对地震物理机制的认识和理解，并建立更接近真实地震的摩擦本构关系。

大型地震通常从很小的局部点开始发育，而后沿断裂扩展。我们难以从震源深度获得复杂断裂的认识，只能通过实验室进行模拟分析相应的摩擦规律。在这项研究中，我们通过实验展示了地震相关的动力学参数，包括滑移距离、滑移速度和滑移加速度。此外，我们还建立了基于实验的高速摩擦模型，并对脉冲型、Yoffe方程、高斯速度、以及瞬时愈合等地震加载模式进行了数值模拟。研究结果为地震成因提供部分实验理论基础。从脉冲地震实验结合数值模拟的角度分析验证了Rice在1998年提出的“脉冲地震可能存在”的猜想；并且统计了脉冲加载模式下的地震摩擦规律，建立了HARD摩擦模型，对地震破裂进行了数值模拟，提出地震破裂过程中存在“速度强化”的物理机制。