Collaborative Research: Catching the quake: Investigating samples from the JFAST expedition for evidence of the 2011 Tohoku Earthquake

合作研究：捕捉地震：调查 JFAST 探险队的样本以寻找 2011 年东北地震的证据

• 批准号: 1260602
• 负责人: James Kirkpatrick
• 金额: $ 15.37万
• 依托单位: Colorado State University
• 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: 2013-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1260602&HistoricalAwards=false
• 关键词: Collaborative; Research; Catching; quake; Investigating

This proposal seeks to understand how shallow slip occurred during the Tohoku earthquake by determining the frictional strength of the fault before the rupture initiated and during slip. Using samples collected from the fault during IODP exp 341 (JFast), the PI?s will undertake:1) Organic thermal maturity measurements to identify the rupture plane and quantify the frictional temperature anomaly induced by coseismic slip.2) Microstructure observations to identify and characterize the fault that hosted the earthquake, including the identification of textures that indicate frictional weakening.3) Friction measurements to constrain the steady-state frictional stress of the faults.These results are crucial for understanding tsunami genesis in shallow subduction zones and will provide critical information for tsunami prediction and hazard mitigation. Importantly, only direct observation and measurement of the fault physical properties can determine these parameters. The Tohoku quake was a surprise, previous work had indicated that such a quake was unlikely in region, especially one in which large amounts of slip occurred in ?weak? shallow accretionary prism sediment. Understanding this quake requires understanding frictional characteristics of rocks in fault zone. There are three plausible scenarios:First, the fault could have undergone dramatic frictional weakening during rapid slip resulting in very low stress coseismically. Alternatively, stress prior to the earthquake was low and changes on the fault were small coseismically, with slip driven by stress transferred from the deeper part of the fault Finally, slip could have propagated through a velocity-strengthening region of the fault with little fault weakening on average.Broader impacts: Information relating to how a major (and unexpected) tsunami-generating quake was hosted in shallow sediments. A better understanding of tsunamigenic earthquakes has great societal importance.

这一建议试图通过确定断裂开始前和滑动期间断层的摩擦强度来了解在东北地震期间浅滑动是如何发生的。使用IODP exp 341 （JFast）期间从故障中收集的样本，PI？1)有机热成熟度测量，识别破裂面，量化同震滑动引起的摩擦温度异常。2)通过微观结构观测识别和表征地震断层，包括识别表明摩擦减弱的结构。3)摩擦测量以约束断层的稳态摩擦应力。这些结果对于了解浅层俯冲带的海啸成因至关重要，并将为海啸预测和减灾提供重要信息。重要的是，只有直接观察和测量断层的物理性质才能确定这些参数。东北地震是一个意外，之前的研究表明，这样的地震不太可能发生在该地区，尤其是在一个发生大量滑动的脆弱地区。浅层增生棱镜沉积物。了解这次地震需要了解断层带岩石的摩擦特性。有三种可能的情况：第一，断层可能在快速滑动期间经历了剧烈的摩擦弱化，导致同震应力非常低。或者，地震前的应力较低，断层的同震变化较小，滑移是由断层深层传递的应力驱动的。最后，滑移可能通过断层的速度增强区传播，断层的平均弱化程度很小。更广泛的影响：有关引发海啸的大地震（意外的）是如何在浅层沉积物中发生的信息。更好地了解海啸性地震具有重要的社会意义。