Surface Rupture Earthquakes and the Mechanics of Earthquake Faulting

提出的工作将从历史地震动地震中发展新的观测和数据，以提高对地震破裂过程的理解。先前的观测已经定义了断层几何形状在破裂传播中的作用，在地表破裂滑动分布的描述中处理和排除了自相似性，清楚地表明断层破裂并不总是单向或双向的，地震并不总是在最终记录最大滑动的断层部分开始。大走滑地震的平均同震滑动与破裂长度之间的关系似乎要求发震层以下深度逐渐增大的同震滑动作为破裂长度的函数。由于时间和资金的限制，以前的工作仅限于一组大约36次大型大陆地震，这些地震具有以下特征：(1)地表破裂轨迹图，(2)附近未破裂的活动断层图，以及(3)沿着破裂走向的许多点的同震偏移量测量，以确定地表滑动分布。最终的汇编已经成为地震物理学界大量引用和广泛使用的资源。这项工作将把以前的分析扩展到一个清单上，这个清单上有两倍多的地震，这些地震产生了地表喷发，但记录可能无法同时满足所有三个标准。这一建议的前提是，在采用类似的方法并将分析扩展到这些额外的地表破裂地震时，还需要获得许多观察和见解。更广泛的意义：在我们努力理解地震过程的物理过程中，将观测范围置于量化地震危险的核心，这是由绘制的活动断层造成的；这是拟议研究最广泛和最实际的影响。其他研究人员已经开发了地震破裂行为的数值模型，但是要知道它们对地球行为的预测程度取决于实际地面破裂的观测数据。研究问题包括破裂可以从一个断层跳到另一个断层多远，断层轨迹的角度偏差如何影响破裂，地壳破裂延伸到多深，以及地表破裂如何与预期的地面运动相关联。作为一个实际的例子，经验观察将改进工具来定义加州地震的预期终点和破裂长度。资金还将用于培养研究生水平的地球科学学生。

The proposed work will develop new observations and data from historical groundrupturing earthquakes to improve understanding of the earthquake rupture process. Priorobservations have worked to define the role of fault geometry in rupture propagation, addressedand discounted self-similarity in the description of surface rupture slip distributions, shownclearly that fault rupture is not consistently uni- or bi-lateral, that earthquakes do not consistentlyinitiate on the section of fault ultimately recording maximum slip, and thatthe relationshipbetween average coseismic slip and rupture length for large strike-slip earthquakes appears torequire coseismic slip at progressively greater depths below the seismogenic layer as a functionof rupture length. Previous work was been limited by time and funding to a set of about threedozen large continental earthquakes which shared the characteristics that there existed (1) mapsof the surface rupture trace, (2) maps of the nearby active faults that did not rupture, and (3)measurements of coseismic offset at many points along the strike of the rupture to define thesurface slip distribution. The resulting compilation has already become a heavily cited andwidely used resource for the larger earthquake physics community. This work will extendprevious analyses to a list of more than twice as many earthquakes that have produced surfaceruptures but for which documentation may not simultaneously satisfy all three criteria. Thepremise of this proposal is that many observations and insights are yet to be gained in followinga similar approach and extending the analysis to these additional surface rupturing earthquakes.Broader Significance:Placing observational bounds on our efforts to understand the physics of the earthquakeprocess is at the heart of quantifying earthquake hazard imposed by mapped active faults; this isthe broadest and most practical impact of the proposed research. Other researchers havedeveloped numerical models of earthquake rupture behavior, but knowing how well they predictreal earth behavior depends on observational data from real ground ruptures. Research questionsinclude how far a rupture can jump from one fault to another, how angle deviations in a faulttrace affect rupture, how deep into the crust rupture extends, and how surface rupture correlateswith expected ground motions. As a practical example, the empirical observations will improvetools to define the expected endpoints and thus rupture lengths of earthquakes in California.Funding will also contribute to the training of a graduate-level geoscience student.