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Sediment signatures of the 2010 Chile Mw 8.8 earthquake

2010 年智利 8.8 级地震的沉积物特征

基本信息

批准号：
NE/I00503X/1
负责人：
Ian Shennan
金额：
$ 6.59万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FI00503X%2F1
关键词：
Sediment signatures 2010 Chile Mw

项目摘要

Great earthquakes (Magnitude 8 and above) and related tsunami, generated where the Earth's tectonic plates collide, produce major hazards for both the earthquake area and heavily populated coastlines across much of the adjacent ocean. On 27th February 2010, a Mw 8.8 earthquake struck central Chile. This is the 5th or 6th largest earthquake ever recorded and resulted in over 500 deaths, with 500,000 homes significantly damaged and initial estimates of the financial cost ranging from $15bn to $30bn. We seek urgency funding to make a rapid field assessment of the sedimentary record of land uplift and subsidence at the coast. We shall collect sediments deposited by the tsunami and those deposited later by daily tides. Laboratory analyses of these sediments will provide, for the first time, the modern equivalent of geological records used to investigate the long-term record of these large earthquakes, not just in Chile but coasts in similar tectonic settings, e.g. Alaska, Washington, Oregon, British Columbia, Japan, Indonesia and Tonga. Evaluating future earthquake and tsunami risk around the Pacific and Indian Oceans requires knowing how frequently great earthquakes occur, at what intervals and how the patterns of land movement vary in different events. We can only obtain the long term patterns from the geological investigations of sediments accumulating of the last 5000 years. Land and sea-level motions, as well as coastal sedimentation (and restoration / reconstruction efforts) mean that field observations from the immediate post earthquake event are critical to our palaeoseismic reconstructions. This has been recently shown in the contemporary sampling that followed the Indian Ocean tsunami but this took place in a markedly different coastal and climate regime to that in Chile. Analysis of the sediments from Chile will help us to validate methods used and applicable to all these other areas. The results will help validate methods to (1) estimate the amount of uplift and subsidence in previous earthquakes over the past few thousand years in these areas; (2) determine the area affected by uplift or subsidence in each great earthquake, and (3) determine whether similar sized areas rupture each time, or can we have even greater earthquakes when two adjacent parts of the tectonic plate boundaries rupture at the same time. There are three key reasons for urgency. First, as restoration takes place in Chile we expect to see the loss of pristine sediments as farmland is recovered and grazing resumes on intertidal salt marshes. Second, sediment traces of medium sized tsunami are often ephemeral, where the run-up extends into the supratidal zone. Heavy rainfall, which is common in this area of Chile, will likely destroy sedimentary evidence of the tsunami within a few months. Third, sites at the southern end of the rupture will potentially preserve the overlap, mixing or separation of evidence of the 1960 Chile earthquake (Magnitude 9.5, the largest ever recorded by instrumentation) as these sites lie in the area potentially recording two earthquakes 50 yr apart. This will provide unique sedimentary evidence for testing methods and models for separating multi-segment from single-segment great earthquakes preserved in the sedimentary record for the last few thousand years. This is a critical debate in assessing earthquake hazard, tsunami generation and the long-term development of the boundaries where tectonic plates collide.

地球构造板块碰撞时产生的大地震（8 级及以上）和相关海啸对地震区和邻近海洋大部分人口稠密的海岸线造成重大危害。 2010年2月27日，智利中部发生里氏8.8级地震。这是有记录以来第 5 或第 6 大地震，导致 500 多人死亡，50 万栋房屋严重受损，初步估计财务损失在 150 亿美元到 300 亿美元之间。我们寻求紧急资金，对海岸陆地隆起和沉降的沉积记录进行快速现场评估。我们将收集海啸沉积的沉积物以及随后每日潮汐沉积的沉积物。对这些沉积物的实验室分析将首次提供相当于现代地质记录的信息，用于调查这些大地震的长期记录，不仅在智利，而且在类似构造环境的海岸，例如智利。阿拉斯加州、华盛顿州、俄勒冈州、不列颠哥伦比亚省、日本、印度尼西亚和汤加。评估太平洋和印度洋周围未来的地震和海啸风险需要了解大地震发生的频率、间隔时间以及不同事件中陆地运动模式的变化。我们只能通过对过去5000年沉积物积累的地质调查来获得长期模式。陆地和海平面运动以及沿海沉积（以及恢复/重建工作）意味着地震发生后的现场观测对于我们的古地震重建至关重要。印度洋海啸之后的当代采样最近显示了这一点，但这次采样发生在与智利明显不同的沿海和气候状况中。对智利沉积物的分析将帮助我们验证所使用的方法并适用于所有其他地区。研究结果将有助于验证以下方法：（1）估计这些地区过去几千年来地震中的隆起和下沉量；（2）确定每次大地震中受隆起或沉降影响的区域，以及（3）确定每次是否有类似大小的区域破裂，或者当板块边界的两个相邻部分同时破裂时是否会发生更大的地震。紧迫性有三个主要原因。首先，随着智利的恢复，我们预计随着农田的恢复和潮间带盐沼恢复放牧，原始沉积物将会消失。其次，中型海啸的沉积物痕迹通常是短暂的，海啸上升时会延伸到潮上带。智利这一地区常见的强降雨可能会在几个月内摧毁海啸的沉积证据。第三，位于断裂南端的地点可能会保留 1960 年智利地震（震级 9.5 级，仪器记录的最大地震）证据的重叠、混合或分离，因为这些地点可能记录了相隔 50 年的两次地震。这将为测试方法和模型提供独特的沉积证据，以区分过去几千年沉积记录中保存的多段和单段大地震。这是评估地震危险、海啸发生以及板块碰撞边界长期发展的关键争论。