The Role of Sediments in Rupture Dynamics of Tsunami Earthquakes and Tsunami Generation

海洋板块携带的沉积物持续流入俯冲带是会聚板块边界的显著特征之一，可能导致最明显的低速断层带#9135;这一因素在很大程度上被地震建模界所忽视。俯冲带中沉积物的优势被认为是造成俯冲带地震的巨大复杂性的原因，这在地壳地震中是看不到的。拟议的研究集中在一类特殊的俯冲带地震：海啸地震。大量的观测表明，海啸地震发生在靠近海沟的浅层，并与异常长的破裂持续时间，低破裂速度，和/或小应力降。这些破裂特征被认为是俯冲带沉积物造成的。在弧前盆地的沉积物也被发现会影响板块界面上大的滑动粗糙体的位置，并与大海啸generation.The沉积物如何有助于这些过程的基本物理相关，但是，还没有很好地理解。为什么海啸地震的破裂速度很慢？为什么这些地震的破裂持续时间长，应力降小，与常规地震明显不同？这些特征是否与异常海啸的产生有关？沉积物的作用有多大？自由面在破裂动力学中是否起重要作用？沉积物和自由表面能共同引起大的海底隆起和海啸发生吗？我们提出的动态破裂模型为解决这些问题提供了主要的理论手段，了解控制海啸地震和海啸发生的物理机制，对于减少海啸对人类社会的危害具有明显的价值。拟议的研究将使用动态破裂模型来研究沉积物在海啸地震破裂动力学中的作用，并更好地了解异常海啸产生的物理机制。本研究拟进行为期两年的研究，包括以下活动：（i）研究海啸地震期间由沉积物和自由面引起的断层上的动应力演化及其与破裂速度和滑动的关系。(ii)探讨断层外沉积物屈服对断裂特征和海底变形的影响。(iii)模拟弧前盆地对地震波传播、海底形变和断层滑动分布的影响。

Continuous flux of sediments carried by the oceanic plate into subduction zone is one of the distinct features of the convergent plate boundary, giving rise to probably the most pronounced low-velocity fault zones ⎯ a factor that has largely been overlooked by the earthquake modeling community. The dominance of sediments in the subduction zone has been considered to contribute to great complexities in subduction zone earthquakes that are not seen in crustal earthquakes.The proposed research focuses on a special class of subduction zone earthquakes: tsunami earthquakes. Numerous observations indicate that tsunami earthquakes occur at shallow depths close to the trench and are associated with the unusually long rupture duration, low rupture velocity, and/or small stress drop. These rupture characteristics have been attributed to sediments in subduction zone. Sediments in the forearc basin have also been found to affect the location of large slip asperities on the plate interface and correlate with large tsunami generation.The underlying physics as to how sediments contribute to these processes is, however, not well understood. Why is the rupture velocity slow for tsunami earthquakes? Why do these earthquakes have long rupture duration and small stress drops, which are distinctly different from regular earthquakes? Are these features related to the anomalous tsunami generation? How significant is the role of sediments? Does the free surface play an important role in the rupture dynamics? Can sediments and free surface together give rise to large seafloor uplift and tsunamigenesis? The dynamic rupture models that we propose provide the principal theoretical means currently available for helping answer these questions.Understanding the physical mechanism for controlling tsunami earthquakes and tsunami generation has its obvious value for reducing tsunami hazards to the human society. The proposed research will use dynamic rupture models to investigate the role of sediments in rupture dynamics of tsunami earthquakes and to better understand the physical mechanism for anomalous tsunami generation. The 2-year research proposed here will include the following activities: (i) Investigate the dynamic stress evolution on faults during tsunami earthquakes induced by both sediments and free surface, and its relations with rupture velocity and slip. (ii) Explore the effect of off-fault yielding of sediments on the rupture characteristics and seafloor deformation. (iii) Simulate the effect of forearc basin on seismic wave propagation, seafloor deformation and fault slip distribution.