Collaborative Research: Subduction Zone Segmentation over Multiple Seismic Cycles, South-Central Chile

合作研究：智利中南部多个地震周期的俯冲带分割

• 批准号: 1357756
• 负责人: Benjamin Horton
• 金额: $ 12.35万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1357756&HistoricalAwards=false
• 关键词: Collaborative; Research; Subduction; Zone; Segmentation

The possible segmentation of subduction zone faults currently presents one of the most significant questions to the physics and geology of earthquake occurrence and the assessment of future earthquake hazards. How will future large earthquakes be arrayed along a fault? How and why will individual earthquake ruptures stop? Subduction zone faults form the tectonic plate boundaries that parallel the coastlines of many countries around the world. Advances in instrumentation and modeling in recent decades have produced important insights into fault behavior, yet these measurements span only fractions of the time interval between major earthquakes. The goal of this research project is to use an interdisciplinary array of evidence preserved in coastal landforms and sediments to investigate whether segmentation of subduction zone faults is maintained over multiple earthquake cycles spanning hundreds to thousands of years. The field are, the Arauco Peninsula coast of south-central Chile, crosses the boundary between the rupture zones of two of the largest subduction zone earthquakes in the worldwide historic record, on May 22, 1960 (Mw 9.5) and February 27, 2010 (Mw 8.8). Prior to 2010, the study area for this project in south-central Chile was one of the most accepted hard fault segment boundaries along the Peru-Chile trench; it was believed to bound several historical ruptures, including the Great Chilean earthquake of 1960. The Chilean earthquake in February 2010 called this hypothesis into question, when the rupture extended south of this boundary and only partially overlapped with the previous earthquake in AD 1835. The combination of geological evidence of past earthquakes over the last 4000 years, frequent large subduction zone earthquakes, and an unusually long and comprehensive historic record of earthquakes in south-central Chile makes this region a natural laboratory to address fundamental questions about fault segmentation. This research project will test multiple hypotheses regarding earthquake behavior and coastal response: (1) fault ruptures over multiple earthquake cycles could terminate at fixed (hard), variable (soft), or random boundaries, or could include multiple segments; (2) large subduction zone earthquakes will produce a tsunami deposit simultaneous with an abrupt change in land level; and (3) the Holocene coastal evolution in this region reflects a modest net change in relative sea level in which the vertical uplift or subsidence during large earthquakes is largely reversed during the periods between earthquakes. To address these hypotheses the research team will reconstruct vertical land-level changes and tsunami history associated with multiple earthquake cycles using geomorphic, sedimentological and microfossil analysis. They will characterize the optimal environmental settings for the preservation of land-level changes and tsunami deposits in sedimentary sequences and analyze the impacts of these land-level changes on the coastal landscape.Ruptures on subduction zone faults have created some of the largest earthquakes and tsunamis in the world, such as the catastrophic earthquake in Japan in 2011 that killed thousands of people and destroyed coastal cities. The practical importance of this investigation for assessing future earthquake hazards in other similar geological settings was underscored by the unforeseen extent of fault ruptures and resulting earthquake magnitudes in the recent devastating earthquakes in Sumatra in 2004, Chile in 2010 and Japan in 2011. The project will build on strong existing collaboration with Chilean scientists. The results will inform the construction of earthquake and tsunami risk maps through established contacts in Chile, and we will arrange public presentations on earthquake and tsunami hazards. The general concepts will advance knowledge of earthquake behavior over time periods that exceed the relatively short period of the instrumental record.This project is supported by the Tectonics Program and Geomorphology and Land Use Dynamics Program in the Division of Earth Sciences and the Office of International Science and Engineering.

目前，俯冲带的可能分割是地震发生物理和地质的最重要问题之一以及对未来地震危害的评估。未来的大地震将如何沿断层驱逐？各个地震破裂是如何以及为什么停止的？俯冲带断层形成了与世界许多国家海岸线相似的构造板边界。近几十年来，仪器和建模的进步产生了对断层行为的重要见解，但是这些测量仅涵盖了主要地震之间时间间隔的分数。该研究项目的目的是使用在沿海地面和沉积物中保存的一系列跨学科的证据来研究俯冲带断层的分割是否在跨越数百至数年的多个地震周期中保持。该领域是智利中南部智利的Arauco半岛沿岸，跨越了全球历史记录中两个最大的俯冲带地震的破裂区域，1960年5月22日（MW 9.5）（MW 9.5）和2010年2月27日（MW 8.8）（MW 8.8）。在2010年之前，该项目在智利中南部的研究区域是秘鲁 - 智利沟渠沿线最受接受的硬断层细分市场的边界之一。人们认为它会束缚几次历史破裂，包括1960年的智利大地震。2010年2月的智利地震将这种假设称为疑问，当时的破裂延伸到了这个边界以南，并且仅与第1835年的先前地震重叠，并且仅在1835年的地震中部分地地震证据。智利中南部的地震使该地区成为解决故障分割基本问题的自然实验室。该研究项目将检验有关地震行为和沿海反应的多种假设：（1）多个地震周期的断层破裂可能在固定（硬），可变（软）或随机边界上终止，或者可能包括多个段； （2）大型俯冲带地震将同时产生海啸矿床，土地水平突然变化； （3）该地区的全新世沿海进化反映了相对海平面的净变化，在大地震期间，大地震期间的垂直隆起或沉降在地震之间大部分逆转。为了解决这些假设，研究小组将使用地震，沉积和微化石分析重建与多个地震周期相关的垂直土地层面变化和海啸历史。它们将描述以沉积序列保护土地水平变化和海啸沉积物的最佳环境环境，并分析这些土地水平变化对沿海景观的影响。俯冲区断层的破坏造成了一些最大的地震和沿海地区的沿海地区，例如沿海地区造成了沿海地区的袭击，造成了沿海地区的袭击。这项调查对于评估其他类似地质环境中未来地震危害的实际重要性，这是由于无法预见的断层破裂程度以及在2004年苏门答腊最近在2004年县县造成的地震而导致的地震幅度的强调，2010年和日本在2011年在日本进行。结果将通过智利建立的联系方式为地震和海啸风险地图的建设提供信息，我们将在地震和海啸危害上安排公开演讲。一般概念将使对地震行为的知识超过工具记录相对较短的时间段。该项目得到了地球科学部和国际科学和工程办公室的构造计划和地貌学计划和地貌和土地利用动态计划的支持。