Architecture of the Subduction to Strike-Slip Transition in New Zealand

近年来，地震学家已经认识到，许多发生的大地震涉及多个断层的滑动。这一现象意味着，基于单个断层失效假设的地震危险性估计可能会低估一个地区可能发生的最大地震的规模，进而低估地震危险性的水平。2016年11月14日发生在新西兰南岛北部的凯库拉7.8级地震是已知最复杂的地震之一，在20多个断层上观测到地表破裂。地震之后发生了成千上万次余震，它还引发了一些所谓的“慢滑事件”——断层滑动发生在几天到几个月的时间里，而不是像大多数地震那样在几秒钟到几分钟内发生。凯库拉地震是近十年来新西兰南岛北部发生的一系列破坏性地震中最新的一次。该项目将研究与该地区复杂地质演化有关的几个关键问题。该项目将利用过去二十年来开展的广泛研究的数据和结果。它还将利用临时阵列的地震数据，这些阵列用于记录余震，并在NSF的RAPID资助下部分运行。该项目的任务是成像三维地震速度和衰减结构，高精度地重新定位该地区发生的地震，并利用余震位置确定断层滑动几何形状。这项工作将有助于我们了解在大地震中如何发生多断层破坏，从而有助于改进地震危险性估计。这项工作将与新西兰GNS科学公司和惠灵顿维多利亚大学的科学家密切合作进行。此外，作为更广泛影响的一部分，该项目将指导一名女性博士后学者。2016年11月14日发生在新西兰南岛北部凯库拉的里氏7.8级地震是已知最复杂的地震事件之一。地表破裂已经在至少21个断层上被绘制出来。地震后的慢滑事件在大范围内被触发，包括南岛巨型逆冲断层下的大量滑动。凯库拉地震是近十年来南岛坎特伯雷和马尔伯勒地区发生的一系列破坏性地震中最新的一次，从2010年和2011年的达菲尔德和克赖斯特彻奇地震开始，接着是2013年的塞登和格拉斯米尔湖地震，最后是2016年的凯库拉地震。我们注意到，达菲尔德7.1级地震也是一次复杂的多断层破裂。本项目将考察与该地区从俯冲向走滑过渡的复杂构造有关的几个假设。拟议的研究将利用过去二十年来在该地区开展的广泛研究的数据和结果，并利用由美国国家科学基金会通过RAPID奖部分支持的临时余震阵列的数据。主要的分析工具是地震速度和衰减层析成像，结合了最近和计划的方法发展，高精度地震定位和震源机制分析。这项工作将与新西兰GNS科学和惠灵顿维多利亚大学的科学家密切合作，并将聘请一名女性博士后学者进行数据分析和解释。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In recent years, seismologists have come to recognize that many large earthquakes that occur involve slip on multiple faults. This phenomenon means that estimates of earthquake hazard based on the assumption that faults fail individually can underestimate the size of the largest possible earthquake in a region, and in turn the level of seismic hazard. The November 14, 2016 magnitude 7.8 Kaikoura earthquake in the northern South Island, New Zealand, stands out as one of the most complex earthquakes known, with rupture of the ground surface observed on more than 20 faults. The earthquake was followed by tens of thousands of aftershocks, and it also triggered a number of what are called "slow slip events" - fault slip occurring over days to months instead of seconds to minutes like most earthquakes. The Kaikoura earthquake is the latest in a series of damaging earthquakes in the northern part of the South Island in New Zealand that have struck in this decade. This project will examine several key questions related to the complicated geologic evolution of this region. This project will take advantage of data and results from a broad range of studies that have been carried out over the past two decades. It will also utilize seismic data from temporary arrays that were deployed to record aftershock and were operated, in part, with support of RAPID funding from NSF. The tasks of this project are to image the three-dimensional seismic velocity and attenuation structure, to relocate earthquakes that occurred in the region with high-precision, and to determine the fault slip geometry using the aftershock locations. This work will contribute to our understanding of how multiple-fault failure occurs in large earthquakes, thereby contributing to improving seismic hazard estimation. The work will be carried out in close collaboration with New Zealand scientists from GNS Science and Victoria University of Wellington. In addition, as part of the broader impacts, this project will mentor a female postdoctoral scholar.The November 14, 2016 Mw 7.8 Kaikoura earthquake in the northern South Island, New Zealand, stands out as one of the most complex seismic events known. Surface rupture has been mapped on at least 21 faults. Post-seismic slow slip events were triggered over a broad area, including substantial slip on the South Island megathrust underlying the activated crustal faults. The Kaikoura earthquake is the latest in a series of damaging earthquakes in the Canterbury and Marlborough regions of the South Island that have struck in this decade, starting with the Darfield and Christchurch earthquakes of 2010 and 2011, continuing with the Seddon and Lake Grassmere earthquakes of 2013, and culminating in the 2016 Kaikoura earthquake. We note that the Mw 7.1 Darfield earthquake was also a complex, multi-fault rupture.This project will examine several hypotheses related to the complex tectonics of this region of transition from subduction to strike-slip. The proposed study will take advantage of data and results from a broad range of studies that have been carried out in this region over the past two decades, and utilize data from temporary aftershock arrays supported in part by NSF through RAPID awards. The main analysis tools are seismic velocity and attenuation tomography that incorporate recent and planned methodological developments, high-precision earthquake relocation, and focal mechanism analysis. The work will be carried out in close collaboration with New Zealand scientists from GNS Science and Victoria University of Wellington and will engage a female postdoctoral scholar in the data analysis and interpretation.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.