SGER: Field Survey of Easter Island

这一行动是为了支持在智利附近的复活节岛和胡安费尔南德斯群岛对 1946 年阿留申海啸进行的实地调查。1946 年 4 月 1 日阿拉斯加乌尼马克岛的海啸仍然是一个地球物理之谜：它是由一场相对中等的地震引发的，但却产生了夏威夷历史上有记录以来最高的波浪，造成了 159 人死亡，造成的损失比附近的 1957 年地震（一场更大的地震）要大得多。事件），甚至是由有史以来最大的地震引发的 1960 年智利海啸。 地震信息很少，理解 1946 年这一事件的唯一现实可能性似乎是根据太平洋周围的淹没数据进行水动力反演。水动力反演准确性的标准尚未制定，但数据的地理分布似乎至少与数据点的数量同样重要，甚至更重要。 直到最近，人们还认为海啸对夏威夷南部影响不大。 然而，在 1999 年 9 月对法图希瓦岛海啸进行实地调查时，国际海啸研究小组发现了一些大型岩石，据报道这些岩石在 1946 年阿留申海啸发生时被移至内陆。 一些岩石是在内陆300m处发现的。 2000 年夏天，美国/法国联合探险队记录了这些发现。 该小组采访了目击者，他们的叙述帮助绘制了 1946 年 4 月 1 日事件中马克萨斯群岛的大致淹没地图。这次对复活节岛和智利附近胡安·费尔南德斯群岛的阿留申海啸的实地调查非常及时，因为这些岛屿的位置允许测量自由场淹没数据 - 假设可以找到目击者。 在马克萨斯岛调查期间，ITST 采访了 6 个岛屿上的约 40 名目击者（以及社会群岛中的 2 个岛屿上的另外 10 名目击者），其中许多人已经上了年纪。 除了预期目击者的高龄之外，进行这项调查还有另一个令人信服的原因：初步分析表明阿留申海啸涉及山体滑坡。 如果是这种情况，那么迫切需要精确的水动力反演来识别滑坡源。 目前正在重新评估夏威夷的洪水地图，并首次绘制美国大陆太平洋各州的洪水地图。 需要仔细重新评估阿留申群岛的海啸，特别是考虑到引发山体滑坡的可能性，以便利用现有的最佳技术和现场知识来制定新的疏散地图。

This action is to support a field survey, in Easter Island and the Juan Fernandez Islands off Chile, of the 1946 Aleutian tsunami.The April 1,1946 Unimak Island, Alaskan tsunami remains a geophysical mystery: It was generated by a relatively moderate earthquake, yet it produced the highest waves recorded in historical times in Hawaii, where it killed 159 people and caused considerably more damage than the nearby 1957 earthquake (a much larger seismic event), or even the great 1960 Chilean tsunami that was triggered by the largest earthquake ever measured. Seismic information is scant, and the only realistic possibility of understanding this 1946 event appears to be hydrodynamic inversion from inundation data around the Pacific.Criteria for the accuracy of hydrodynamic inversions are not well established, but it appears that the geographic distribution of data is at least as important, if not more so, than the number of data points. Until recently, it was believed that the tsunami had little impact south of Hawaii. However during a field survey of an tsunami in the island of Fatu Hiva in September 1999, the International Tsunami Research Team discovered large rocks that were reportedly moved inland in 1946, at about the time of the Aleutian tsunami. Some of the rocks were found 300m inland. In the summer of 2000, a joint US/France expedition was able to document these findings. The team interviewed eyewitnesses and their accounts helped develop approximate inundation maps for the Marquesas from the April 1,1946 event.This field survey of the Aleutian tsunami in Easter Island and the Juan Fernandez Islands off Chile is very timely, since the location of these islands allows the measurement of free field inundation data - assuming that eyewitnesses can be found. During the Marquesas survey, the ITST interviewed about 40 eyewitnesses on 6 islands (and an additional 10 on 2 of the Society Islands), many quite elderly. Apart from the advanced age of the expected eyewitnesses, there is another compelling reason for performing this survey: preliminary analysis suggests that a landslide was involved in the Aleutian tsunami. If this is the case, then accurate hydrodynamic inversion is urgently needed to identify the landslide source. Inundation maps for Hawaii are currently being re-evaluated, and inundation maps for the Pacific states of the US mainland are being developed for the first time. Tsunamis from the Aleutians need to be carefully reassessed, particularly in view of the landslide trigger potential, so that the new evacuation maps are developed with the best available technology and field knowledge.