| 弯折断层系统上超剪切破裂传播的产生条件 |
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| 引用本文： | 郑玲珑,钱峰,张海明.弯折断层系统上超剪切破裂传播的产生条件[J].地球物理学报,2021,64(1):182-194. |
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| 作者姓名： | 郑玲珑 钱峰 张海明 |
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| 作者单位： | 北京大学地球与空间科学学院地球物理系,北京100871;北京大学地球与空间科学学院地球物理系,北京100871;北京大学地球与空间科学学院地球物理系,北京100871 |
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| 基金项目： | 国家自然科学基金项目（41674050和41874070）资助. |
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| 摘 要： | 断层的破裂速度是描述地震震源过程的重要物理量.如果震源破裂的传播速度超过剪切波速,将会对地震波场产生影响,造成更大的破坏性.超剪切破裂的产生受多种因素影响,断层的几何形状是因素之一.本文针对弯折断层的情况,采用三维空间非结构化网格的边界积分方法计算参数空间中的破裂相图,从中分析超剪切破裂的产生条件.以15°、25°和40°为例,得到了不同断层弯折角度的破裂相图.在本文的初始应力设置下,通过对不同的无量纲化临界滑动弱化位移Dc和初始剪应力Te参数组合的结果进行交叉对比发现,对于弯折面处于压缩区的断层模型,不可持续传播的自发停止破裂的发生条件与弯折角无关.而对于可持续传播破裂,其在平面断层的传播速度也不受弯折角影响;在弯折部分,随弯折角度增大,破裂传播速度越小,正应力越大,破裂强度越大,破裂越难以越过弯折交界线继续传播(如40°).对比三个不同弯折角的相图,弯折角越小,越容易发生超剪切破裂,即发生超剪切的参数空间越大.同时,随着初始剪应力的增大,超剪切不仅可以发生在弯折面上,甚至在平面部分就可以发生.总体而言,Dc较小、Te较大时,破裂传播速度更大,更容易形成超剪切破裂.另外,因克服弯折交界处的正应力而产生的错位延迟效应也与弯折角度正相关.
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| 关 键 词： | 边界积分方程 超剪切破裂 弯折断层 相图 破裂速度 |
| 收稿时间： | 2020-05-27 |
The transition conditions of supershear rupture propagation on fault-bend systems |
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| ZHENG LingLong,QIAN Feng,ZHANG HaiMing.The transition conditions of supershear rupture propagation on fault-bend systems[J].Chinese Journal of Geophysics,2021,64(1):182-194. |
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| Authors: | ZHENG LingLong QIAN Feng ZHANG HaiMing |
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| Institution: | School of Earth and Space Sciences, Peking University, Beijing 100871, China |
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| Abstract: | The rupture speed on the fault during an earthquake is an important physical quantity to describe the earthquake source process. The seismic wave field would be affected, which possibly creates much more severe damage, if the propagation speed of the rupture exceeds the shear wave velocity. The occurrence of supershear rupture is controlled by many factors, one of which is the fault geometry. In this paper, we focus on the fault geometry with a bending angle. By adopting the boundary integral equation method based on the three-dimensional unstructured grids, we are able to calculate the rupture phase diagram in the parameter space, and analyze the transition conditions of supershear rupture. Taking 15°, 25° and 40° as examples, phase diagrams under different bending angles are obtained. Under the initial stress setting of this study, by cross-comparing the results on different combinations dimensionless critical slip weakening distance Dc and initial shear stress Te, we find that for fault models with bending planes in the compression zone, the generation of the unsustainable self-arresting ruptures is independent of the bending angle. Similarly, for the sustainable ruptures, the propagation speed on the planar part of the fault is also not affected by the bending angle. At the bending line, however, the rupture speed will reduce with the increase of the bending angle. And the greater the normal stress, the greater the fracture strength is, and the harder it is to propagate beyond the bending line (e.g., 40°). Comparing the three phase diagrams, it is easier to generate the supershear rupture when the bending angle is small, in other words, the corresponding parameter space is larger for a smaller bending angle. Moreover, with the increase of initial shear stress, supershear rupture can occur not only on the bending plane, but also on the planar part. In general, when Dc is small and Te is large, the rupture propagation speed is large, which is more prone to generate supershear rupture. In addition, the delay effect caused by overcoming the normal stress is also positively related to the bending angle. |
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| Keywords: | Boundary integral equation Supershear rupture Bend fault Phase diagram Rupture speed |
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