Determining hillslope-scale material strength from seismically-triggered landslide events

对项目的非技术描述，它解释了项目的意义和重要性。滑坡在世界上许多山区是一个持续的威胁，在容易发生大地震的地区，危险增加了。尽管存在这种联系，但关于地震事件能在多大程度上引发滑坡的知识还很初级。该项目将检查1994年加州北岭地震的数据，以评估岩性、构造、岩石强度和裂缝密度如何影响山坡对滑坡的敏感性。数据将输入一个模型，该模型是为2008年中国汶川地震开发的试点测试。加利福尼亚地震的更详细和实地检验的结果将允许改进模型，并使其更广泛地适用于其他地区的危害评估。特别是，这些数据将被纳入美国地质调查局的一个项目，该项目正在开发一个自动化系统，为应急响应、政府和援助机构以及媒体提供对世界各地地震影响和损失的估计。这个项目取得的进展将有助于它们的实施。项目的技术说明自然山坡强度是景观演变和危害评估的主要控制因素，通常与在实验室用手大小的样品测量岩石强度有很大不同。实验室测试是在完整的岩石上进行的，但决定山坡岩石强度的是裂缝密度、孔径和尺寸。山坡的强度可以通过使用高地形的大地震事件来量化，地震会引起强烈的地面运动（峰值地面加速度）和可量化的景观反应（山体滑坡）。本项目利用模拟的峰值地面加速度，评估斜坡稳定性作为滑坡厚度和剪切强度特性（黏聚力和内摩擦角）对特定地震事件的函数。这项研究的重点是1994年北岭6.7级地震造成的滑坡，在那里，构造变形导致山坡强度降低，这可以与岩性和气候因素隔离开来。该项目将结合建模和实地考察来验证这一假设，其结果将提高对构造过程作为岩石弱化调控因素的认识。这些发现与地表过程、景观演化、构造和自然灾害评估有关。

A non-technical description of the project, which explains the project's significance and importanceLandslides are a continual threat in many mountainous regions of the world and the danger is increased in areas prone to large earthquakes. In spite of this association, knowledge concerning the extent to which seismic events can trigger landslides is rudimentary. This project will examine data from the 1994 Northridge, California earthquake in order to evaluate how lithology, tectonics, rock strength, and fracture density influence the susceptibility of hillslopes to landslides. Data will be entered into a model that was developed as a pilot test for the 2008 Wenchuan earthquake in China. The more detailed and field-checked results from the California earthquake will permit refinement of the model and engender a wider applicability for hazard assessments in other areas. In particular, the data will be incorporated into a program of the U.S. Geological Survey, which is developing an automated system that produces estimates of impact and losses for earthquakes around the world for emergency response, government and aid agencies, and the media. Advances resulting from this project will aid in their implementation.A technical description of the projectNatural hillslope strength, which is a major controlling factor for landscape evolution and hazard assessment, is usually quite different than measurements of rock strength on hand-sized samples done in the laboratory. Laboratory tests are performed on intact rock, yet it is fracture density, aperture, and size that determine hillslope-scale rock strength. The strength of hillslopes can be quantified by using large seismic events in high relief settings, where an earthquake causes strong ground motion (peak ground acceleration) and a quantifiable landscape response (landsliding). This project assesses slope stability as a function of landslide thickness and shear-strength properties (cohesion and internal angle of friction) for a particular seismic event using modeled peak ground acceleration. The research focuses on landslides caused by the 1994 magnitude 6.7 Northridge earthquake, where it is hypothesized that tectonic deformation causes a strength reduction of hillslopes that can be isolated from lithologic and climatic factors. The project will integrate modeling and fieldwork to test this hypothesis and the results will improve knowledge of tectonic processes as a governor of rock weakening. The findings are relevant to earth surface processes, landscape evolution, tectonics, and natural-hazard assessment.