Faulting process and strong ground motion predicted from crustal deformation

1)长町-里夫断裂带周边地壳变形利用地理调查所GPS地球观测网观测资料，研究了长町-里夫断裂带周边地壳水平变形。以三个GPS观测点组成的三角形作为有限元法的三角形单元，利用有限元法中的应变计算技术，估算了地壳变形的应变速率。应变速率的大小在空间上存在差异，但应变速率的主要方向几乎垂直于断层走向。这一结果表明，长町-里夫断裂为逆冲断裂。(2)长町-里夫断层破裂模拟利用多场岩石破裂实验所得参数的经验方程，在考虑地壳温度和初始应力变化的基础上，从理论上提出了一种评估断层表面破裂剪应力、破裂应力降和临界滑动位移等断层参数的方法。利用该方法建立了长町断裂的有限元模型。我们通过将地壳变形应用于有限元模型的侧向边界作为规定位移来进行断层的破裂模拟。模拟得到的地面加速度时程存在数值误差。这些误差似乎是由于采用的节理单元作为故障模型无法模拟停止滑动后的粘滞阶段的数值问题造成的。3)断层滑动停止后的粘滞阶段为了克服上述数值问题，在块滑块模型的基础上发展了一种数值计算技术。该技术允许模拟粘贴模式。为了验证所提出的数值方法，将数值结果与块滑块模型的谐波稳态精确解和块滑块试件振动实验结果进行了比较。该方法模拟了精确解和实验结果。少

1) Crustal deformation around the Nagamachi-Rifu faultsThe horizontal crustal deformation around the Nagamachi-Rifu faults was investigated from the records observed by GPS earth observation network of the Geographical Survey Institute. The strain rates of the crustal deformation were estimated by taking a triangular composed of three GPS observation points as a triangular element of finite element method and using the technique of strain calculation in finite element method. The magnitude of the strain rate varied spatially, but the major principal directions of the rates were almost perpendicular to the strike of the faults. This result indicates that the Nagamachi-Rifu faults are thrust faulting.2) Simulation of fault rupture of the Nagamachi-Rifu faultsA method for evaluating the fault parameters such as breakdown shear stress, breakdown stress drop, and critical slip displacement on fault surface was developed theoretically by using empirical equation of the parameters obtained fr … More om breakdown experiments of rocks and taking the variations of temperature and initial stress in crust into account. Using the method, the finite element model of the Nagamachi-rifu faults was build. We performed the rupture simulations of the faults by applying the crustal deformation to the lateral boundaries of the finite element model as prescribed displacement. The numerical errors were observed in the time history of acceleration on the ground obtained from the simulation. The errors seemed to be caused by the numerical problem that the joint elements adopted as fault model is incapable of simulating stick phase after cease of sliding.3) Stick phase after cease of fault slidingTo overcome the above numerical problem, a numerical technique was developed on the base of block-slider model. The technique permit to simulate the stickmode. In order to validate the proposed numerical technique, the numerical results were compared with the exact solutions of block-slidermodel for harmonic steady state motion and the results obtained by the vibration experiments of block-slider specimen. The proposed method simulated the exact solutions and the experimental results. Less