Collaborative Research: Modeling fault ruptures along bends and stepovers

合作研究：模拟沿弯曲和步距的断层破裂

基本信息

批准号：
2013695
负责人：
Benchun Duan
金额：
$ 25万
依托单位：
Texas A&M University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2013695&HistoricalAwards=false
关键词：
Collaborative Research Modeling fault ruptures

项目摘要

Earthquakes occur when faults rupture, and large earthquakes are produced when ruptures propagate long distances along fault zones. Large earthquakes often rupture across tens to hundreds of miles of faults, including stepovers (gaps) between fault segments and bends in faults. These fault irregularities can also stop rupture propagation. So, they play an important role in understanding earthquake hazard assessment. Whether or not an earthquake rupture is able to pass through a given stepover or a bend is very important. Previous studies have suggested that stepovers more than about 5 km wide would stop rupture propagation, but some recent large earthquakes have jumped wider gaps. The 2016 magnitude 7.8 New Zealand earthquake, for example, involved rupture jumping over a gap more than 15 km wide between faults. This project will use tectonic fault models to simulate the initial stress field, especially around stepovers and bends, and then use the results to improve fault rupture models. Results of this project will improve our understanding of large earthquakes and their hazards, particularly within continents where fault systems are complex. This research will train two graduate students in the emerging field of multiphysics in faulting and earthquakes. Undergraduate students will be involved through senior thesis research, and research results, including animations of fault ruptures, will be incorporated into the undergraduate curriculum at Texas A&M and the University of Missouri, and be freely available to other educators. Computer codes developed in this project will be freely shared with other researchers.This project will use numerical models to simulate fault rupture and propagation along stepovers and bends, the fault irregularities that often stop fault rupture, hence limiting the size of earthquakes. Knowing whether or not a given stepover or bend can stop fault rupture propagation is critical for hazard assessment, because large earthquakes, especially those on intracontinental strike-slip faults, usually rupture multiple fault segments by jumping over stepovers and propagating along fault bends. Previous numerical modeling and some field observations have suggested that stepovers more than ~5 km wide would stop fault rupturing; however, ruptures in the 2016 Mw 7.8 Kaikoura earthquake in New Zealand jumped more than 15 km between faults. Fault geometry and initial stress are among the most important factors dictating rupture behavior, but initial stress is often poorly constrained and simplified as homogeneous or ad hoc heterogeneous in previous dynamic rupture models. On the other hand, it is well known that stress tends to concentrate around stepovers, bends, and other fault irregularities. This project will use fault tectonics models to simulate changes of regional static stress around stepovers and bends, and quasi-static stress changes due to previous slip events. The resulting stress fields will then be used in dynamic rupture models to simulate spontaneous propagation of fault ruptures during earthquakes. The research will use generic fault models to explore key parameters controlling rupture along stepovers and bends, and then a model based on the 2016 Kaikoura earthquake will be developed to gain insights into complex ruptures involving multiple faults. Results of this project will improve our understanding of large earthquakes and their hazards, particularly within continents where fault systems are complex and large events often involve rupture of multiple faults or segments. This research takes an important step toward a fully integrated model of fault mechanics that simulates stress evolution and rupture behaviors over multiple timescales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

当断裂破裂时发生地震，当破裂沿断层区域繁殖时，会产生大地震。大地震经常在数十至数百英里的断层上破裂，包括断层段和弯曲之间的阶梯越过（间隙）。这些断层不规则性也会阻止破裂的传播。因此，他们在理解地震危险评估中起着重要作用。地震破裂是否能够穿过给定的步骤或弯曲非常重要。先前的研究表明，宽度超过5公里的阶梯将停止破裂的繁殖，但是最近的一些大地震越来越大。例如，2016年的7.8新西兰地震涉及破裂的破裂，两次断层之间的距离超过15公里。该项目将使用构造断层模型来模拟初始应力场，尤其是在踏板和弯曲周围，然后使用结果来改善故障破裂模型。该项目的结果将提高我们对大型地震及其危害的理解，尤其是在断层系统复杂的大陆内。这项研究将培训两名研究生在过失和地震领域的新兴领域。本科生将通过高级论文研究参与，研究结果（包括故障破裂的动画）将被纳入德克萨斯州A＆M和密苏里大学的本科课程中，并可以向其他教育者免费获得。该项目中开发的计算机代码将与其他研究人员自由共享。本项目将使用数值模型来模拟断层破裂和沿Stepover和弯曲的传播，这通常会阻止断层破裂的故障不规则，因此限制了地震的大小。知道给定的阶梯或弯曲是否可以停止断层破裂的传播对于危害评估至关重要，因为大地震，尤其是在肠内滑移断层上的大地震，通常会通过跳过踏板并沿断层弯曲传播而破裂多个断层段。以前的数值建模和一些现场观测表明，宽度超过5 km的踏板会阻止断层破裂。然而，在2016年MW 7.8 kaikoura地震中，新西兰的地震跃升了15公里以上的断层。断层几何形状和初始应力是决定破裂行为的最重要因素之一，但是在先前的动态破裂模型中，初始应力通常受到巨大的约束和简化为均质或临时异质的。另一方面，众所周知，压力倾向于集中在踩踏，弯曲和其他错误不规则周围。该项目将使用故障构造模型来模拟Stepover和弯曲周围区域静电应力的变化，以及由于以前的滑移事件而导致的准静态应力变化。然后，所得的应力场将用于动态破裂模型中，以模拟地震期间断层破裂的自发传播。该研究将使用通用故障模型来探索控制沿Stepover和弯曲的破裂的关键参数，然后将开发基于2016年Kaikoura地震的模型，以洞悉涉及多个故障的复杂破裂。该项目的结果将提高我们对大型地震及其危害的理解，尤其是在断层系统复杂且大型事件通常涉及多个断层或细分市场的大陆上。这项研究朝着完全集成的故障力学模型迈出了重要的一步，该模型在多个时间范围内模拟了压力的演变和破裂行为。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛影响的审查标准通过评估来通过评估来支持的。