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

合作研究：2018 年安克雷奇 7 级地震的快速大地测量场响应

• 批准号: 2137370
• 负责人: Julie Elliott
• 金额: $ 1.11万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-05-15 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2137370&HistoricalAwards=false
• 关键词: Collaborative; Research; RAPID; Geodetic; Field

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.

2018年11月30日，阿拉斯加安克雷奇北部发生7级地震，造成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，板块可能向下弯曲，早期迹象表明，该事件与板块弯曲引起的应力有关。 在大地震后的几周或几个月里，滑动和变形会继续沿着构造板块的边界沿着发生。 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，并在其他当地基准位置记录活动GPS测量结果。 这项研究的数据可用于更好地了解德纳里断层沿着的行为，并改善对当地地震危险的限制。 该项目的重点是约束震后变形由于7级安克雷奇地震，正常的断层事件在雅库塔特平板，包括同震和震后变形如何可能触发变化的滑动沿着俯冲界面。为实现这一目标，将在地震近场安装五个新的连续全球定位系统站点，并将在整个区域的基准上进行重复活动调查。这些测量将提供一个数据集，将能够更完整地描述地震后变形，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。 板块内正断层地震对上板块变形、俯冲界面沿着耦合以及界面上的瞬变事件的影响尚不清楚。 在连续的GPS站点记录的同震位移显示出复杂的变形模式和事件的位置使它可能在软流圈粘弹性松弛将发生。 地震后最初几周记录的余震大致描绘了一个水平表面，表明这些事件可能发生在板块界面或附近。主震发生在一个过去经历过多年缓慢滑动事件的地区，对其他俯冲带的研究表明，这些地区更容易在地震后触发缓慢滑动事件。沿着雅库塔特平板的东部边界，2002年德纳里地震的震后研究表明，该事件可能导致了俯冲界面沿着该部分的耦合的长期变化。余震区内GPS站点的稀疏性使得潜在界面上的瞬态变化可能未被检测到，并且震后变形和沿沿着界面的耦合变化可能无法完全表征。从拟议的新的连续GPS网络收集的数据，加上现有的连续GPS和重复调查的数据，在运动基准将允许这些信号的评估在一个更时空密集的规模比目前可能的。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。