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: 2044916
• 负责人: Christopher Paola
• 金额: $ 13.5万
• 依托单位: University of Minnesota-Twin Cities
• 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=2044916&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年的苏门答腊和2011年的Tohoku-Oki Mega-Earthquakes和海啸是灾难性的地质事件，具有重大的社会后果。两者在俯冲的构造板边界的区域造成了巨大的破裂，而构造板板边界预计不会有那么大的地震。大的断层位移到达了海洋沟的海底，导致了巨大的海啸。像这样的板块边界是海底地震，尤其是海啸中的最重要的来源，也是类似大地震的唯一来源。这两个最近的两项在刺激海洋研究以及对巨型锻炼和相关海啸的进一步了解方面特别重要。关于较早事件的数据对于解决此类事件发生的何处以及对它们的期望至关重要，但是仪器数据中几乎没有此类事件。唯一的评论是从沉积物沉积物中的记录中重建了较旧的巨型地震。海底地震中的深水研究目前正在使用Tohoku-Oki地震的沉积物特征来识别以前大地震的特征。这项研究正在促进我们对与异常大地震相关的沉积事件的独特特征的理解，并有助于在沉积记录中区分它们。典型的事件沉积物包括层压，混沌和均匀的沉积物（“同质岩”）。这项研究将结合现场观测，包括沉积物和宽度表面沉积物动员的文献，以及一种新型的实验室“沉积物振荡器”，以更好地了解这些罕见但毁灭性事件的独特属性。该项目支持学生和早期职业科学家的培训。俯冲边缘上最大的大型巨像地震消除了100 km宽的破裂的沉积物，从而在层学中留下了特征性的事件散布。它们通常包括一个准确的透明层，该层在岩性，物理和地球化学上（“同质”），以及具有广泛的沉积结构和组成（“浊度”）的准确层压层。最近发现了2011年日本地震的泥泞同质岩，以衍生出表面（少数厘米）沉积物的宽度重新化，而富含砂的浊度却源自斜坡故障和潜水源。这种差异适用于其他地震和环境，表明了不同的重新策略过程。该假设将通过实验室实验来检验，该实验将探讨这些过程是否响应地震谱的不同部分。要解决的另一个问题是，高于M≥9.0兆果皮破裂的海底的极大且持续的长周期振荡是否可能进入表面沉积物，从而解释了同质岩。 2011年Tohoku地震的特殊数据集将用于进行实验。通过合作，将添加来自卡斯卡迪亚利润率的样本，小安列斯群岛和巴利阿里的深渊平原。从地球物理和核心数据与物理实验中对全球观察的比较将为理解地震消除沉积物的方式提供重要的一步，并进步了海底古sopperogicy质学领域，以识别大型事件押金。该奖项颁发了NSF的法定任务，反映了通过评估基金会的支持者，并通过基金会的范围来评估了支持的珍贵。