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Sedimentological post-tsunami survey of the deposits formed by the September 16, 2015 Illapel tsunami in central Chile

对 2015 年 9 月 16 日智利中部伊拉佩尔海啸形成的沉积物进行海啸后沉积调查

基本信息

批准号：
310697700
负责人：
Professor Dr. Hans Heinrich Bahlburg
金额：
--
依托单位：
Institut für Geologie und Paläontologie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/310697700?language=en
关键词：
Sedimentological post tsunami survey deposits

项目摘要

On September 16, 2015 a Mw 8.3 earthquake off the coast of Illapel, central Chile, triggered a tsunami reaching wave heights exceeding 4.5 m at the town of Coquimbo. Eye witness reports indicate that the tsunami deposited sediments at several coastal sites including the coast near the village of Tongoy south of Coquimbo. Post-tsunami surveys conducted in the wake of a larger tsunami depositing sediment onshore are an indispensable tool in the study of tsunami deposits. They are instrumental not only in encompassing the large and still not completely explored variety of sediments deposited by tsunamis but also for gauging the difference between modern deposits and those contained in the paleotsunami record. Recent studies indicate that sediment thicknesses and extent, sedimentary structures, grain-size distributions and petrographical composition maybe significantly altered already in the first few years after deposition. These differences are largely due to post-depositional modification including early diagenesis. Presently there are only two studies exploring these changes by following the deposits fate in the years following a tsunami event. In the proposed study we will map the spatial distribution of the deposits laid down by the September 16, 2015, Illapel tsunami. Distance from the coast to the line of maximum inflow as well as the relationship between this distance and the landward end of sediment deposition are of particular interest. If present we will record markers of the inundation height. We will record the sedimentological features of the deposits by digging pits and trenches. We will sample the deposits in grids covering the lateral extent of the sediments to map the spatial arrangement of grain-size distributions. If more than one tsunami layer is present we will sample each layer, or, if possible, each lamina. We will also sample for later OSL studies to explore the reasons for inhomogenous bleaching of datable grains in tsunami deposits observed in several studies. Where possible we will interview eye witnesses to obtain information on inundation heights and other observations.

2015年9月16日，智利中部伊拉佩尔近海发生8.3级地震，引发海啸，科昆博镇的海浪高度超过4.5米。目击者报告表明，海啸在几个沿海地点沉积了沉积物，包括科金博以南的通戈伊村附近的海岸。在一场更大的海啸之后进行的海啸后调查，在岸上沉积沉积物是研究海啸沉积不可缺少的工具。它们不仅有助于涵盖海啸沉积的大量仍未完全勘探的各种沉积物，而且还有助于测量现代沉积物与古海啸记录中所包含的沉积物之间的差异。最近的研究表明，在沉积后的头几年，沉积物的厚度和范围、沉积结构、粒度分布和岩石成分可能已经发生了重大变化。这些差异在很大程度上是由于沉积后的改造作用，包括早期成岩作用。目前，只有两项研究通过跟踪海啸事件后几年的沉积物命运来探索这些变化。在拟议的研究中，我们将绘制2015年9月16日伊拉佩尔海啸沉积的沉积物的空间分布图。从海岸到最大流入线的距离以及这一距离与泥沙淤积向陆地的末端之间的关系特别令人感兴趣。如果有的话，我们将记录淹没高度的标记。我们将通过挖坑和挖沟来记录矿床的沉积学特征。我们将在覆盖沉积物横向范围的网格中对沉积物进行采样，以绘制粒度分布的空间排列图。如果存在不止一个海啸层，我们将对每一层进行抽样，或者，如果可能，对每一层进行抽样。我们还将为以后的OSL研究提供样本，以探索在几项研究中观察到的海啸沉积物中可测得的颗粒不均匀漂白的原因。在可能的情况下，我们将与目击者面谈，以获得有关淹没高度和其他观察到的信息。