SGER: Field Survey of Easter Island

这项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年阿留申海啸进行实地调查。1946年4月1日发生在阿拉斯加乌尼马克岛的海啸仍然是一个地球物理学上的谜：它是由一次相对温和的地震引起的，但它在夏威夷产生了有历史记录以来最高的海浪，造成159人死亡，造成的破坏远远超过了附近1957年的地震（一次更大的地震事件），甚至超过了1960年智利的大海啸，后者是由有史以来最大的地震引发的。地震信息很少，理解1946年这次事件的唯一现实可能性似乎是太平洋周围淹没数据的水动力反演。水动力反演精度的标准还没有很好地确立，但看来数据的地理分布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的影响很小。然而，在1999年9月对法图希瓦岛的海啸进行实地调查时，国际海啸研究小组发现了据报道在1946年阿留申海啸发生时被移动到内陆的大型岩石。有些岩石是在内陆300米处发现的。2000年夏天，一支美法联合考察队记录下了这些发现。该小组采访了目击者，他们的描述帮助绘制了1946年4月1日事件发生后马克萨斯群岛的大致淹没地图。这次对复活节岛和智利胡安费尔南德斯群岛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。在马克萨斯岛的调查中，ITST采访了6个岛屿上的大约40名目击者（另外10人在2个社会岛屿上），其中许多人都很老。除了预期的目击者年事已高之外，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。如果是这样的话，那么迫切需要精确的水动力反演来识别滑坡的源头。夏威夷的洪水地图目前正在重新评估，美国大陆太平洋各州的洪水地图正在首次开发。需要仔细重新评估来自阿留申群岛的海啸，特别是考虑到可能引发山体滑坡，以便利用现有的最佳技术和实地知识编制新的疏散地图。

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.