Joint Inversion of Surface Waves and Teleseismic Body Waves to Study the Formation of the High Lava Plains in Eastern Oregon

这项提案中的研究将提高我们对俄勒冈州东部高熔岩平原的理解。高熔岩平原是一系列富含硅的火山喷发，大约15年前开始于俄勒冈州的东南角，从那时起一直向北和向东发展。虽然沿着喀斯喀特山脉的火山活动很容易用俄勒冈州和华盛顿州下面的胡安·德·富卡板块的俯冲来解释，但内陆地区后来向弧方向发展的火山活动却很难解释。可能的解释包括：地幔深处有一种被称为地幔柱的热物质上涌，上部板块刚性部分的厚度差异可以控制其下方的流动模式，以及/或胡安·德·富卡板块进一步向东俯冲导致的动态地幔流动模式。本提案中的研究将开发一种新的方法，用于分析位于高熔岩平原的地震台站收集的世界各地地震的地震数据，以更好地成像地球最上面的150 - 200公里。这种成像将有助于确定哪些因素可能导致这次火山活动，以及各种因素如何相互关联。新的方法是面波和远震体波的联合反演。它将面波层析成像和远震体波层析成像的互补优势结合到三维横波速度结构的单一反演中，从而减少了单独使用任何一种方法时存在的局限性。一旦开发，这种方法将很容易适用于现有和未来的数据集。初步的分辨率测试表明，这种方法不仅可以极大地提高我们对高熔岩平原火山作用的理解，还可以大大提高我们对许多其他环境中上地幔构造过程的理解，这些环境中有密集的区域数据集可用。

The research in this proposal will improve our understanding of the High Lava Plains in eastern Oregon. The High Lava Plains are a series of silica-rich volcanic eruptions which began some 15 Ma at the south eastern corner of Oregon, and have been progressing to the north and east since then. While volcanism along the Cascades is easily explained by the subduction of the Juan de Fuca plate beneath Oregon and Washington, volcanism further inland which later progresses towards the arc is very difficult to explain. Possible explanations may include the presence of a deep mantle upwelling of hot material called a plume, differences in the thickness of the rigid portion of the upper plate which could control flow patterns beneath it, and/or dynamic mantle flow patterns caused by the subducting Juan de Fuca plate further to the east. The research in this proposal will develop a new method for analyzing seismic data from earthquakes around the world collected at seismic stations located within the High Lava Plains to better image the uppermost 150 - 200 km of the earth. This imaging will help constrain which of these factors may be causing this volcanism, and how the various factors may relate to each other. The new methodology is a joint inversion of surface waves and teleseismic body waves. It combines the complementary strengths of surface wave tomography and teleseismic body wave tomography into a single inversion for 3-D shear wave velocity structure, thereby reducing the limitations that exist when using either type of approach alone. Once developed, this methodology will be readily applicable to existing and future datasets. Preliminary resolution tests indicate that this methodology promises to greatly improve our understanding, not only of the High Lava Plains volcanism, but of tectonic processes in the upper mantle in many other settings where dense regional datasets are available.