Geodynamic Modeling of Long-term Fault Interactions During the Evolution of the Pacific-North American Plate Boundary Zone

太平洋-北美板块边界带演化过程中长期断层相互作用的地球动力学模拟

• 批准号: 0948620
• 负责人: Mian Liu
• 金额: $ 13.5万
• 依托单位: University of Missouri-Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948620&HistoricalAwards=false
• 关键词: Geodynamic; Modeling; Long; term; Fault

The San Andreas Fault is the tectonic boundary between the Pacific and the North American plates, yet only a portion of the relative plate motion is absorbed by slip on the San Andreas Fault proper. The rest, up to 25 per cent, is accommodated by a complex system of faults over a broad plate boundary zone, by the Eastern California shear zone. Such diffuse deformation in the plate boundary zone is responsible for the widely scattered earthquakes in California and Nevada, but it is not clear how the Eastern California shear zone and other faults in the San Andreas Fault system formed, and what controls the strain partitioning among these faults. This research project will attempt to address the following questions: 1) what caused the inception and development of the Eastern California shear zone? 2) how has the development of the Eastern California shear zone, the Garlock Fault, and the San Jacinto Fault in the past few million years affected the crustal dynamics in the San Andreas Fault plate boundary zone? The study employs numerical modeling of long-term mechanical coupling and fault interactions in which the research team will develop a finite element model for three-dimensional, regional-scale lithospheric deformation. The viscoelastoplastic formulation in this model allows simulation of strain localization in the crust outside the faults, hence the inception of new faults.Plate boundaries are major fault zones, across which the relative plate motion produces concentrated crustal deformation, volcanoes, and earthquakes. However, the Pacific- North American plate boundary is a major exception. Here the plate boundary, the San Andreas fault absorbs only part of the relative plate motion and the rest is accommodated by slip on many faults in a complex system that extents into central Nevada. The proposed research seeks to understand why these fault initiated and what controls strain partitioning among these faults. The results of this study will help us to better understand the geodynamic implications of the observed crustal motion, hence provide insights into earthquakes in California and Nevada.

圣安德烈亚斯断层是太平洋板块和北美板块之间的构造边界，但只有一部分相对板块运动被圣安德烈亚斯断层本身的滑动吸收。其余的，高达25%，是由一个广泛的板块边界带，东加州剪切带的复杂断层系统容纳的。板块边界带的这种扩散变形是造成加州和内华达州广泛分布的地震的原因，但目前尚不清楚东加州剪切带和圣安德烈亚斯断层系统中的其他断层是如何形成的，以及是什么控制了这些断层之间的应变分配。本研究将试图解决以下问题：1）是什么导致了东加州剪切带的形成和发展？2)在过去的几百万年里，东加州剪切带、加洛克断层和圣哈辛托断层的发展如何影响了圣安德烈亚斯断层板块边界带的地壳动力学？该研究采用了长期力学耦合和断层相互作用的数值模拟，其中研究小组将开发三维区域尺度岩石圈变形的有限元模型。该模型中的粘弹塑性公式允许模拟断层外地壳中的应变局部化，从而产生新的断层。板块边界是主要的断层带，板块的相对运动产生集中的地壳变形，火山和地震。然而，太平洋-北美板块边界是一个主要的例外。这里是板块边界，圣安德烈亚斯断层只吸收了部分相对板块运动，其余部分则由延伸到内华达州中部的复杂系统中的许多断层上的滑动来调节。拟议的研究旨在了解为什么这些故障启动和什么控制这些故障之间的应变分配。这一研究结果将有助于我们更好地理解所观测到的地壳运动的地球动力学意义，从而为加州和内华达州的地震提供见解。