CAREER: Decoding the Enigmas of U.S. Seismic Hazard Via Multi-Scale, Multi-Physics Approaches to Paleoliquefaction Analysis

这个教师早期职业发展计划（Career）项目将为减少美国地震灾害的不确定性提供知识，从而促进科学进步和国家的繁荣与福利。在全国范围内，有许多地区的地震灾害特别不确定，因为地震的返回周期比历史记录更长。换句话说，我们知道地震已经发生并将继续发生，但由于以前的地震早于人类记录和/或地震仪器的出现，对未来地震的预期特征是高度不确定的。在这些地区，由过去地震引起的土壤液化，称为“古液化”，可能是确定地震危险信息的唯一证据，包括地震的震级、位置和复发率。因此，美国的建筑规范深受古液化证据的影响，反过来，公共安全也是如此。该奖项支持基础研究，以改善古液化的分析，目前受到限制，可能导致高度错误的结果。这些发现不仅将推进古液化分析，而且将有利于了解液化的一般危害，从而进一步减少地震对建筑和自然环境的影响。此外，教育研究部分将调查地震风险感知与社会心理偏见之间的联系，从而在自然灾害工程方面建立更有效的教育平台。这个CAREER项目旨在消除古液化准确反分析的普遍障碍，这将通过在三个不同的尺度上弥合基础知识差距来实现。研究内容包括：(1)控制流化岩脉和砂沸点形成和形态的微观尺度物理数值研究；(2)一个耦合的、力学一致的液化触发和表现模式的中尺度公式；(3)采用宏观尺度方法对古液化震源进行概率定位并评估其破裂震级。然后，从基础研究中开发的分析框架将应用于神秘的地震灾害对社会产生重大影响的地区的古液化证据。其中包括美国西北部的卡斯卡迪亚俯冲带；美国中部的新马德里地震带；美国东部的南卡罗来纳海岸平原；在物理和数值多尺度建模、现场测试和前所未有的案例历史数据的帮助下，本研究将推进古液化分析和对液化危害的总体理解，从而减少未来地震的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development Program (CAREER) project will contribute knowledge that reduces the uncertainty of seismic hazards in the United States, thereby promoting scientific progress and the nation's prosperity and welfare. Nationally, there are many regions in which seismic hazards are especially uncertain because the return periods of earthquakes are longer than the historic record. In other words, it is known that earthquakes have and will continue to occur, but because prior earthquakes predate human records and/or the advent of seismic instruments, the expected characteristics of future earthquakes are highly uncertain. In these locales, soil liquefaction caused by past earthquakes, termed "paleoliquefaction," may provide the only evidence from which information about the seismic-hazard can be determined, including earthquake magnitudes, locations, and recurrence-rates. As a result, U.S. building codes are heavily influenced by paleoliquefaction evidence, and in turn, so too is public safety. This award supports fundamental research to improve the analysis of paleoliquefaction, which at present suffers from limitations that can lead to highly erroneous results. The findings will not only advance paleoliquefaction analytics, but will also benefit the understanding of liquefaction hazards in general, thus further reducing earthquake impacts on the built and natural environments. In addition, an educational research component will investigate links between seismic risk perception and socio-psychological bias, leading to more effective educational platforms in natural hazards engineering. This CAREER project aims to remove ubiquitous barriers to the accurate inverse-analysis of paleoliquefaction, which will be achieved by bridging fundamental knowledge-gaps at three distinct scales. The research includes: (1) micro-scale physical-numerical investigation of the mechanics controlling the formation and morphology of fluidized dikes and sand boils; (2) meso-scale formulation of a coupled, mechanically-consistent liquefaction triggering and manifestation model; and (3) a macro-scale approach to probabilistically geolocate seismic sources from paleoliquefaction and assess their rupture magnitudes. An analytical framework developed from the fundamental research will then be applied to paleoliquefaction evidence in regions where enigmatic seismic-hazards significantly impact society. These include the Cascadia Subduction Zone of the Northwest U.S.; the New Madrid Seismic Zone of the Central U.S.; the South Carolina Coastal Plain of the Eastern U.S.; and Coastal New England in the Northeast U.S. Aided by physical and numerical multi-scale modeling, field testing, and unprecedented case-history data, this research will advance both paleoliquefaction analytics and the understanding of liquefaction hazards in general, thus reducing future earthquake impacts.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.