Unusual geologic evidence of coeval seismic shaking and tsunamis shows variability in earthquake size and recurrence in the area of the giant 1960 Chile earthquake
Unusual geologic evidence of coeval seismic shaking and tsunamis shows variability in earthquake size and recurrence in the area of the giant 1960 Chile earthquake
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DOI：
10.1016/j.margeo.2016.12.007
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发表时间：
2017-03-01
期刊：
影响因子：
2.9
通讯作者：
Ely, L. L.
中科院分区：
文献类型：
--
作者：
Cisternas, M.;Garrett, E.;Ely, L. L.
一个不寻常的海岸沉积记录结合了自公元1000年以来在仪器记录的最大地震地区的地震震动和海啸淹没的证据：1960年智利南部的巨大地震（Mw 9.5）。记录显示，沿着纳斯卡-南美板块边界的这一部分，大规模逆冲地震和随之而来的海啸的规模和复发率存在显著差异。在1960年破裂的沿着，奇洛埃岛上有一个500米长的沿海露头，提供了被碎屑流杂岩局部掩埋和被海啸沙层广泛掩埋的土壤层的连续暴露。这些杂岩夷平了植物，使其产生地质上精确的年龄，与其他地方的年代确定的证据相关联。在1960年地震之前，发生了三次地震，其影响可能与1960年地震相似，分别发生在公元898- 1128年、1300 -1398年和1575年，还有五次相对较小的地震。地震和海啸在公元1300年至1575年之间异常频繁。它们的平均复发间隔为85年，仅略超过1960年以来已经过去的时间。这一推论令人严重关切，因为在1960年事件发生后不久，该地区预计不会发生地震，而目前的板块锁定表明，边界的某些部分已经能够产生大地震。这个世界上地震最活跃的俯冲带之一的长期地震和海啸历史提供了一个可变破裂模式的例子，其中地震规模和复发间隔从一个地震到下一个地震都不同。(C)2016爱思唯尔B. V.保留所有权利。
An uncommon coastal sedimentary record combines evidence for seismic shaking and coincident tsunami inundation since AD 1000 in the region of the largest earthquake recorded instrumentally: the giant 1960 southern Chile earthquake (Mw 9.5). The record reveals significant variability in the size and recurrence of megathrust earthquakes and ensuing tsunamis along this part of the Nazca-South American plate boundary. A 500-m long coastal outcrop on Isla Chiloe, midway along the 1960 rupture, provides continuous exposure of soil horizons buried locally by debris-flow diamicts and extensively by tsunami sand sheets. The diamicts flattened plants that yield geologically precise ages to correlate with well-dated evidence elsewhere. The 1960 event was preceded by three earthquakes that probably resembled it in their effects, in AD 898-1128,1300-1398 and 1575, and by five relatively smaller intervening earthquakes. Earthquakes and tsunamis recurred exceptionally often between AD 1300 and 1575. Their average recurrence interval of 85 years only slightly exceeds the time already elapsed since 1960. This inference is of serious concern because no earthquake has been anticipated in the region so soon after the 1960 event, and current plate locking suggests that some segments of the boundary are already capable of producing large earthquakes. This long-term earthquake and tsunami history of one of the world's most seismically active subduction zones provides an example of variable rupture mode, in which earthquake size and recurrence interval vary from one earthquake to the next. (C) 2016 Elsevier B.V. All rights reserved.