Collaborative Research: RAPID Geodetic Field Response to the 2018 Magnitude 7 Anchorage Earthquake

2018年11月30日，阿拉斯加安克雷奇以北发生7级地震，私人和公共设施损失超过7500万美元。地震发生在俯冲板块的上部，那里的板块可能向下弯曲，早期迹象表明，这一事件与板块弯曲产生的应力有关。在大地震后的几周和几个月里，沿着构造板块边界可能会继续发生滑动和变形。为了更好地了解这种变形的性质，这项研究将在地震震中附近放置五个连续的GPS(全球定位系统)站，并在当地其他基准地点记录动态GPS测量结果。这项研究的数据可以用来更好地了解德纳利断层的行为，并改善对当地地震灾害的约束。该项目专注于限制7级锚定地震引起的震后变形，这是雅库塔特平板内的一种正常断层事件，包括同震和震后变形如何触发俯冲界面上的滑移变化。为了实现这一目标，将在地震近场安装五个新的连续全球定位系统站点，并将在整个区域以基准进行重复的运动测量。这些测量将提供一个数据集，能够更全面地描述地震后变形、俯冲界面上锁定和蠕动行为的变化，以及潜在的触发慢滑事件。实验室内正断层地震对上板块变形、沿俯冲界面的耦合以及界面上的瞬变事件的影响还不是很清楚。GPS连续观测点记录的同震位移显示出复杂的形变模式，事件的位置使软流层发生粘弹性松弛成为可能。在地震后的头几周记录的余震大致描绘了一个水平表面，表明地震可能发生在板块交界处或附近。主震发生在一个过去经历了多年慢滑事件的地区，而对其他俯冲带的研究表明，这些地区更容易在地震后触发慢滑事件。2002年德纳利地震的震后研究表明，沿着雅库塔特平板的东部界限，那次地震可能导致了沿该段俯冲界面的耦合的长期变化。由于余震区内GPS测点的稀疏性，下伏界面上的瞬时变化可能无法检测到，震后变形和界面上耦合的变化可能无法得到充分表征。从拟议的连续GPS新网络收集的数据，加上现有连续GPS和以竞选基准进行的重复调查的数据，将允许在比目前可能的时间和空间密度更高的范围内对这些信号进行评估。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

On November 30, 2018 a magnitude 7 earthquake struck just north of Anchorage, Alaska and caused over $75 million in damage to private and public facilities. The earthquake took place in the upper part of a subducting slab where the slab may be bending downwards, and early indications suggest that the event was related to stresses caused by plate bending. In the weeks and months following a large earthquake, slip and deformation can continue to take place along a tectonic plate boundary. To better understand that nature of this deformation, this study would place five continuous GPS (global positioning system) stations near the earthquake epicenter, as well as record campaign GPS measurements at other local benchmark locations. Data from this study could be used to better understand the behavior along the Denali fault and improve constraints on local seismic hazards. This project focuses on constraining postseismic deformation due to the magnitude 7 Anchorage earthquake, a normal faulting event within the Yakutat flat slab, including how coseismic and postseismic deformation may trigger changes in slip along the subduction interface. To achieve this, five new continuous GPS sites will be installed in the near-field of the earthquake and repeat campaign surveys will be conducted at benchmarks throughout the region. These measurements will provide a dataset that will be able to more completely characterize postseismic deformation, variations in locking and creeping behavior on the subduction interface, and potential triggered slow slip events. The effect of intraslab normal-faulting earthquakes on upper plate deformation, coupling along the subduction interface, and transient events on the interface is not well understood. Coseismic displacements recorded at continuous GPS sites show a complex deformation pattern and the location of the event make it likely that viscoelastic relaxation in the asthenosphere will occur. Aftershocks recorded in the first weeks after the earthquake roughly delineate a horizontal surface, suggesting that the events may be occurring at or near the plate interface. The main shock occurred within a region that has experienced multi-year slow slip events in the past and studies in other subduction zones suggest that such regions are more prone to triggered slow-slip events after an earthquake. Along the eastern limit of the Yakutat flat slab, a postseismic study of the 2002 Denali earthquake suggested that that event may have caused long-term changes of the coupling along that section of the subduction interface. The sparseness of GPS sites within the aftershock zone makes it likely that transient changes on the underlying interface may go undetected and that postseismic deformation and changes in the coupling along the interface may not be able to be fully characterized. Data collected from the proposed new network of continuous GPS added to the data from existing continuous GPS and repeat surveys at campaign benchmarks will allow an evaluation of these signals at a more temporally and spatially dense scale than is currently possible.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.