Interseismic Slip Deficit at the Edge of a Locked Patch: Shumagin Islands, Alaska

阿拉斯加是研究是什么控制了构造板块会聚沿着地震活动变化的首要地点。这是因为地震带的宽度是已知的不同部分沿着阿拉斯加俯冲带。阿拉斯加半岛段包括从一个广泛的，锁定的地区在板块界面上的一个占主导地位的蠕变部分的过渡。事实上，一系列的岛屿横跨这一段提供了一个理想的设置测量变形，这些数据将被用来确定最近的滑动（或缺乏）的分布沿着板块边界断层。这是第一次详细了解孕震区如何从锁定段变化到蠕动段。这些发现将为评估地震和海啸危险提供信息，无论是与阿拉斯加半岛有关的还是与跨太平洋海啸造成的美国西海岸沿着有关的。调查人员将在舒马金群岛的阿拉斯加州沙角当地社区的学区进行公开讲座，并与一名教师合作。将编制关于阿拉斯加地震和海啸、俯冲及其对当地环境的影响等专题的教材，将在1990年代以来未进行过调查的地点进行全球定位系统测量，提供新的高度精确的板块速度。大多数地点已经测量过一次，新的测量将在第一次测量后20年进行，导致速度不确定性应为0.5毫米/年。这些数据将用于估计板块界面断层锁定和蠕动部分的分布，并将孕震区的空间变化与地震活动性和下行板块性质的空间变化进行比较。结果将解决如何突然的沿走向过渡，从广泛的锁定区域的Semidi段到更窄和/或蠕变为主的锁定区域的Shumagin段。Shumagin段部分锁定区域内的结构将通过建模来解决。这项研究还将调查所观察到的滑动变化与上覆或下行板块的特征、板块界面本身的反射特征、地震活动模式或其他地质观测之间的潜在相关性。

Alaska is a premier location for studying what controls variations in seismic activity along a margin where tectonic plates converge. This is because the width of the seismic zone is known to differ between segments along the Alaskan subduction zone. The Alaska Peninsula segment includes the transition from a wide, locked region on the plate interface to a dominantly creeping section. The fact that a chain of islandsruns across this segment provides an ideal setting for measuring deformation, and these data will be used to determine the distribution of recent slip (or lack thereof) along the plate boundary fault. This is the first time that a detailed view of how the seismogenic zone varies from a locked to a creeping section will be obtained. The findings will inform assessment of earthquake and tsunami hazards, both in relation to the Alaska Peninsula and along the US west coast due to trans-Pacific tsunamis. Investigators will conduct public lectures and work with a teacher in the school district of the local community of Sand Point, Alaska, in the Shumagin Islands. Lesson materials will be developed on the topics of earthquakes and tsunamis in Alaska, subduction and its impact on their local environment.GPS measurements will be made at sites that have not been surveyed since the 1990s, providing new highly precise plate velocities. Most of the sites have been measured once, and the new measurements will come 20 years after the first, resulting in velocity uncertainties that should be 0.5 mm/yr. These data will be used to estimate the distribution of locked and creeping parts of the plate interface fault, and spatial changes in the seismogenic zone will be compared with spatial changes in seismicity and properties of thedowngoing plate. Results will address how abrupt the along-strike transition is, from the wide locked region of the Semidi segment to the much narrower and/or creep-dominated locked region of the Shumagin segment. The structure within the partially locked region of the Shumagin segment will be addressed through modeling. The study will also investigate potential correlation between observed slip variations and features on the overriding or downgoing plates, the reflection character of the plate interface itself, seismicity patterns, or other geologic observations.