Collaborative Research: Geodetic Constraints on Moment Deficit and Physics-based Earthquake Cycle Models in the Source Region of the M 9 Tohoku, Japan Earthquake

合作研究：日本东北9级地震震源区矩差的大地测量约束和基于物理的地震周期模型

• 批准号: 1141832
• 负责人: Kaj Johnson
• 金额: $ 9.34万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1141832&HistoricalAwards=false
• 关键词: Collaborative; Research; Geodetic; Constraints; Moment

The Mw 9 March 11, 2011 Tohoku earthquake, resulting in 25,000 fatalities, was the largestearthquake to strike Japan in modern times. The failure of long-term forecasts to anticipate anevent of this magnitude is leading to a reevaluation of our scienti c understanding of subductionzone fault dynamics. At the same time, the enormous Japanese investment in seismic andgeodetic monitoring provides an unprecedented opportunity to study processes leading to giantearthquakes. The investigators will focus here on two aspects of the quake that raise central issues for our abilityto forecast future hazards globally: 1) the constraints that geodetic strain accumulation placeon the seismic moment budget, and 2) how the distribution of mechanical properties on theplate interface control seismic versus aseismic slip.Forecasts of seismic hazard rely primarily on the historical record, paleoseismology, andgeodetic strain accumulation. While a strict time-predictable model has proven inconsistentwith geodetic data in some areas, the rate of strain accumulation must strongly inuence the recurrence rate and/or size of large earthquakes. Previous analyses of the extensive JapaneseGPS data set regularize the underdetermined inverse problem; the inferred plate coupling isthus conditional on the choice of regularizing functional. In addition, most assumed no coupling at the trench, an area that effectively lies in the model null-space. The researchers propose rather to estimate rigorous bounds on the moment deficit rate, independent of any regularizing functional. They also propose to systematically explore the effects of time-dependent viscoelastic effects on estimates of slip deficit.The Tohoku earthquake also raises profound questions about the frictional properties ofthe subducting plate interface. Mw 7 events along the Japan-Kurile trench have repeatedin nearly the same locations. Substantial afterslip following these events suggested that thefault surrounding these seismic `asperities' have different frictional properties, e.g., velocityweakening `asperities' surrounded by velocity strengthening regions. The fact that the March11 earthquake seems to have ruptured through both areas raises important questions. Is theasperity paradigm fundamentally flawed? Or did the M 9 activate other weakening mechanisms(thermal pressurization?) that allowed it to rupture through velocity strengthening regions?To distinguish between competing hypotheses the researchers will use a combination of GPS data basedhypothesis testing and physics based fault modeling. They will test whether or not post-seismicGPS data can be fit with afterslip only in regions that have not experienced seismic slip inthe last several decades. They will test alternative physical models that could accountfor the observed behavior, by extending our numerical codes that couple rate-state friction,thermal pressurization, and dilatant strengthening to three dimensions. This will allow them totest for example whether dilatancy could stabilize slip in otherwise velocity weakening regions,or thermal pressurization could allow ruptures to extend into velocity strengthening areas.

MW 2011年3月11日，Tohoku地震，造成25,000人死亡，是现代袭击日本的巨大态度。长期预测无法预期这种范围的范围的失败，导致我们对细节性断层动力学的科学理解的重新评估。同时，日本对地震和地理监测的巨额投资为研究过程提供了前所未有的机会，从而导致了巨型脉冲。调查人员将在这里关注地震的两个方面，这些方面为我们的全球预测未来危害的能力提出了中心问题：1）限制测量应力积累的限制，地震矩预算，以及2）2）机械性能在板界面界面控制地震和亚eSeasic症上的分布如何依赖于历史悠久的记录，并依赖于历史悠久的记录。尽管严格的时间预测模型已证明在某些地区与大地测量数据不一致，但应变累积的速率必须强烈影响大地震的复发率和/或大小。对广泛的日语数据集的先前分析将不确定的逆问题规范化；推断的板耦合静脉均以正规化功能的选择为条件。此外，大多数人都假定在沟渠上没有耦合，该区域有效地位于模型空间空间中。研究人员建议估算瞬间赤字率的严格界限，而与任何正规化功能无关。他们还建议系统地探索时间依赖性的粘弹性影响对滑动不足的估计的影响。托霍科地震还提出了有关俯冲板界面的摩擦特性的深刻问题。 MW 7赛事沿日本 - 库里尔沟的事件几乎重复了相同的位置。这些事件发生后的大量倒流表明，围绕这些地震的“覆盖率”具有不同的摩擦特性，例如，速度向速度向速度增强区域包围。 3月11日地震似乎在这两个地区破裂的事实引发了重要问题。硫代式范式根本存在缺陷吗？还是M 9激活了其他弱化机制（热加压？），从而使其可以通过速度加强区域破裂？以区分竞争性假设，研究人员将使用基于GPS数据的基于GPS数据的组合和基于物理的故障模型。他们将仅在过去几十年中没有经历过地震滑移的区域中，仅在没有经历过地震滑移的地区才能将其后数据符合。他们将通过扩展我们的数值代码来测试可以解释观察到的行为的替代物理模型，这些代码将对摩擦构成摩擦，热加压和膨胀的增强量为三个维度。这将使他们允许他们倾斜，例如，膨胀性是否可以稳定速度弱化区域中的滑动，或者热加压可以使破裂延伸至速度加强区域。