Collaborative Research: Sedimentary signature of shallow and tsunamigenic megathrust ruptures: Observations and physical models from recent catastrophic events

合作研究：浅海和引发海啸的巨型逆冲断裂的沉积特征：最近灾难性事件的观测和物理模型

• 批准号: 2044915
• 负责人: Cecilia McHugh
• 金额: $ 60.15万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2044915&HistoricalAwards=false
• 关键词: Collaborative; Research; Sedimentary; signature; shallow

The 2004 Sumatra and the 2011 Tohoku-Oki mega-earthquakes and tsunamis were catastrophic geologic events with major societal consequences. Both produced huge ruptures in areas of subducting tectonic plate boundaries that were not expected to have such large earthquakes. The large fault displacement reached the sea-floor of oceanic trenches, causing the huge tsunamis. Plate boundaries like these are the most consequential source of submarine earthquakes, especially tsunamigenic ones, and the only source of similarly large earthquakes. These two most recent ones were particularly significant in stimulating marine research and in providing further understanding of mega-earthquakes and associated tsunamis. Data on earlier large events are critical to addressing where and how often such events occur and what to expect from them, but few such events are available with instrumental data. The only recourse is reconstruction of older mega-earthquakes from their record in sediment deposits. Pioneering deep-water research in submarine earthquake geology is now using the sedimentary signature of the Tohoku-Oki earthquake to recognize signatures of previous large earthquakes. This research is advancing our understanding about the unique characteristics of sedimentation events associated with exceptionally large earthquakes and helping to distinguish them in the sedimentary record. Typical event deposits include laminated, chaotic, and homogeneous sediments (“homogenites”). This study will combine field observations, including deposits and documentation of widespread surface sediment mobilization, with a novel laboratory “sediment shaker”, to better understand the unique attributes of these rare but devastating events. The project supports the training of students and an early career scientist.The largest megathrust earthquakes at subduction margins remobilize sediment over ruptures 100s of km wide, leaving characteristic event-deposits in the stratigraphy. They generally include an acoustically transparent layer that is lithlogically, physically and geochemically homogeneous (“homogenite”), plus acoustically laminated layers with a wide range of sedimentary structures and composition (“turbidites”). The muddy homogenites from the 2011 Japan earthquake have been recently discovered to derive from widespread remobilization of surficial (few cm) sediment, while sand-rich turbidites are thought to derive from slope failures and diverse sources. This difference holds for other earthquakes and settings, suggesting distinct remobilization processes. This hypothesis will be tested by laboratory experiments that will explore whether these processes respond to different parts of the earthquake spectrum. Another question to be addressed is whether the exceptionally large and sustained long-period oscillations of the sea floor above M≥9.0 megathrust ruptures can entrain surficial sediment and thus account for the homogenites. Exceptional data sets from the 2011 Tohoku earthquake will be available to conduct the experiments. Through collaborations, samples from the Cascadia Margin, Lesser Antilles and Balearic Abyssal plain will be added. The comparisons of global observations from geophysical and core data with the physical experiments, will provide a major step forward in understanding the ways in which earthquakes remobilize sediments and advances the field of submarine paleoseismology to recognize megaquake event deposits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

2004 年的苏门答腊岛和 2011 年的东北冲地震和海啸都是灾难性的地质事件，造成了重大的社会后果。海底的海沟，引起像这样的巨大海啸，是海底地震最重要的来源。尤其是引发海啸的地震，也是类似大地震的唯一来源，这两次地震对于刺激海洋研究以及进一步了解特大地震和相关海啸的数据对于解决发生地点和方式至关重要。此类事件经常发生，以及对它们的预期，但很少有此类事件可用仪器数据，目前唯一的办法是根据沉积物沉积物的记录重建较早的大地震。利用东北冲地震的沉积特征来识别以前大地震的特征，这项研究正在加深我们对与特大地震相关的沉积事件的独特特征的理解，并帮助在沉积记录中区分它们。这项研究将现场观察（包括广泛的表面沉积物动员的沉积物和记录）与新型实验室“沉积物摇床”相结合，以更好地研究层状、混乱和均质的沉积物。了解这些罕见但具有破坏性的事件的独特属性。该项目支持对学生和早期职业科学家的培训。俯冲边缘最大的巨型逆冲地震使数百公里宽的断裂处的沉积物重新流动，在地层中留下了特征性的事件沉积物。通常包括岩性、物理和地球化学均质的声学透明层（“均质岩”），以及具有各种沉积结构和成分的声学叠层最近发现，2011 年日本地震的泥质均质岩源自地表（几厘米）沉积物的广泛再活动，而富含沙子的浊积岩则被认为源自斜坡破坏和多种来源。对于其他地震和环境，该假设将通过实验室实验进行检验，这些实验将探讨这些过程是否对地震谱的不同部分做出反应，另一个需要解决的问题是是否异常大且持续。 M≥9.0 巨型逆冲断裂以上的海底长期振荡会夹带地表沉积物，从而解释 2011 年东北地震的特殊数据集，通过合作，来自卡斯卡迪亚边缘的样本将可用于进行实验。将添加小安的列斯群岛和巴利阿里深渊平原的全球观测结果与物理实验的比较，这将提供重要的信息。在理解地震重新激活沉积物的方式方面向前迈出了一步，并反映了海底古地震学领域识别特大地震事件沉积物的进展。该奖项是 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

IODP Expedition 386 “Japan Trench Paleoseismology”: Mission Specific Platform Giant Piston Coring to track past megathrust earthquakes and their consequences in a deep-sea subduction trench.

IODP Expedition 386“日本海沟古地震学”：任务特定平台巨型活塞取芯，用于跟踪过去的巨型逆冲地震及其在深海俯冲海沟中的后果。

• 发表时间: 2022-06
• 期刊: European Geophysical Union General Assembly 2022
• 作者: Strasser, M.;Ikehara, K.;Eveerst, J.;Meada, L.;The Science Party of IODP Expedition 386
• 通讯作者: The Science Party of IODP Expedition 386

Tracking past earthquakes along the Japan Trench: Fresh initial results from the IODP Japan Trench Paleoseismology Project

追踪日本海沟过去的地震：IODP 日本海沟古地震学项目的最新初步结果

• DOI: 10.5194/egusphere-egu22-1588
• 发表时间: 2022-06
• 期刊: European Geophysical Union General Assembly
• 作者: Strasser, M;Ikehara, K;Everst, J.;Meada, L.;The Science Party of IODP Expedition 386
• 通讯作者: The Science Party of IODP Expedition 386