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

该提案旨在通过确定破裂开始前和滑动期间断层的摩擦强度来了解东北地震期间如何发生浅层滑动。使用IODP exp 341（JFast）期间从故障收集的样本，PI？将进行：1）有机热成熟度测量，以确定破裂面和量化同震滑动引起的摩擦温度异常。2）微观结构观察，以确定和表征承载地震的断层，包括确定表明摩擦弱化的纹理。3）摩擦测量，以限制断层的稳态摩擦应力。这些结果对于理解浅俯冲带海啸的成因至关重要，并将为海啸预测和减灾提供关键信息。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。东北地震是一个惊喜，以前的工作表明，这样的地震是不太可能在该地区，特别是一个在其中发生了大量的滑动？软弱？浅层增生棱镜沉积物。了解这次地震需要了解断裂带岩石的摩擦特性。有三种可能的情况：第一，断层可能在快速滑动过程中经历了剧烈的摩擦弱化，导致同震应力非常低。另一方面，地震前的应力较低，断层的同震变化较小，断层深部的应力导致了滑动。最后，滑动可能通过断层的速度增强区传播，而断层的平均强度几乎没有减弱。更广泛的影响：有关一次大的（和意外的）海啸地震是如何在浅层沉积物中发生的信息。更好地了解海啸地震具有重大的社会意义。

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.