震源动力学模型关键技术的研究

One of the most important goals of strong-motion seismology is to improve the scientific understanding of the physical processes of earthquakes, then to estimate the strong-ground motions expected from future earthquakes and to develop a reliable approach to mitigate the seismic hazards. In fact, an earthquake is a dynamically propagating shear crack that radiates seismic waves and the stress variation on the fault plane is an indication of the dynamic behavior of earthquake rupture. So, to understand the physical processes actually occurring in the source region, one must study stress-dependent material properties as the way in which material failure nucleates and spreads, rapidly relieving stresses that had slowly risen (due to long-term tectonic processes) to exceed the strength of material in the source region. This is a dynamic problem. For a dynamic source model, the stress on the fault plane is the fundamental parameter. It addresses the physics of the earthquake rupture process. Earthquake source dynamics provide key elements for the prediction of strong ground motion and for understand the physics of earthquake initiation, propagation, and healing. Thus, dynamic simulations on earthquake rupture process are the best way to investigate the physics of earthquakes...This proposal will address the key problems in the earthquake dynamic source model. We will investigate the fault behavior during the earthquake rupture process, and determinate the constitutive friction laws. For dynamic simulation of the seismic source rupture process, the friction laws play an important role because the friction laws determine the fault behavior,and control the rupture processes. We will study on the dynamic source parameters and try to put forward a scaling law about these parameters. Also, we are going to develop a sytematic nonlinear inversion method for studying the dynamic rupture propagation by using computational methods for nonlinear optimization with a frictional law. Our results will be expected to help us to improve our knowledge about the physics of earthuakes, to develop and implement physics-based simulation methodologies that can predoct earthquake strong-motion waveforms for earthquake engineering.

强震动地震学最重要的研究目的之一就是正确地理解地震发生过程中的物理本质，进而科学地预测未来大地震所产生的强地面运动，以有效地减轻地震灾害。地震的发生是大地构造应力场长期积累作用的结果，震源动力学模型是以断层附近应力场为其基本参数，是从物理本质上来探究地震的孕育、发生和停止的过程，因而，震源动力学模型的研究对认知地震断层破裂的物理过程有着重要的意义。.本项目研究拟针对震源动力学模型的一些关键性问题进行系统地研究，将从地震实例出发，研究在地震发生时，断层破裂过程中所遵循的摩擦准则，探究震源动力学参数的定标律（scaling law），同时，尝试将非线性优化算法应用于反演震源动力学模型的研究，提出反演震源动力破裂过程的方法。预期研究成果将为基于震源动力学模型评估未来大地震所产生的强地面运动奠定基础。

地震的发生是大地构造应力场长期积累作用的结果，震源动力学模型是以断层附近应力场为其基本参数，是从物理本质上来探究地震的孕育、发生和停止的过程，因而，震源动力学模型的研究对认知地震断层破裂的物理过程有着重要的意义。本项目研究针对震源动力学模型的一些关键性问题了进行地研究，课题研究结果显示，破坏性大地震破裂过程中基本上遵循着滑动弱化摩擦准则，震源动力学参数的分布同断层面上的位错分布有着相似的关系，大的应力降对应着滑动量大的区域，而临界滑动弱化位移Dc同断层面上最终位移量有着正比例的关系；研究了震源动力学模型参数对破裂传播的影响，获得了破裂相图；研究了震源动力学模型参数对近场强地面地震动场的影响特征。同时，也针对影响地震所产生的强地面地震动的“三要素”（震源过程、传播途径、场地效应）开展了研究，提出了“传递台站”场地反应的分析方法，并利用经验格林函数和分形技术开展了强地面地震动数值模拟的研究，实际震例分析显示取得了较好的效果。