M. West - Volcanic/tectonic interests

Volcano / tectonics interests

The plate tectonics revolution of the 1960s provided a framework for understanding many of the processes at work in Earth's crust. While it shed light on the distribution of global volcanism, it did little to explain the mechanics of individual volcanoes. To be fair, this is a devilish problem. But if we are to ever understand the nature of volcanic eruptions, I believe we must first understand the deeper structure and underlying physics. The projects below show a range of a applications from shallow studies of magma bodies to regional investigations of the upper mantle. The goal of most of these is to understand how the structures and processes we observe on the surface of the Earth may be controlled or influenced by structure not otherwise visible from the surface.

My emphasis is on the roots and plumbing of volcanoes. However, the various imaging techniques have applications in numerous other settings as well. In volcanic environments this structural information can be combined with other geophysical data, geochemistry and eruptive history to explain the origin and transport of magma from its source to the surface.

Projects

The Colima Volcano Deep Seismic Experiment Even though arc volcanoes are a natural result of subduction, we understand little about how arc volcanoes are fed and maintained from below. The Colima Volcano Deep Seismic Experiment (CODEX) will target the deep crustal processes which create discrete volcanoes and ultimately control eruptive behavior. The CODEX array is a cooperative venture between the Geophysical Institute at the University of Alaska Fairbanks and the Universidad de Colima Observatorio Vulcanológico. Over the next several years we will install and maintain a seismic array in the vicinity of Colima Volcano to address these issues. Teleseismic data, together with seismicity in the local crust and subducting slab, will be used to map the deep crustal environment beneath Colima.
The RISTRA project in the southwest U.S. This project seeks to understand the causes of the striking tectonic events that have occured in the southwestern U.S. An extensive field program and a suite of seismic imaging techniques are being combined with surface geology to yeild high resolution images of Earth's crust and upper mantle. Illuminating the deep features beneath this region is vital to understanding the dramatic volcanism, faulting and uplift observed on the surface.The RISTRA project is a collaboration between New Mexico State University, The University of Texas at Austin, New Mexico Tech, Los Alamos National Laboratory and Dine College.
Crustal structure of north and south Tibet The Tibetan plateau is the result of the on-going collision between the Indian tectonic plate into Eurasia. It is the best place on Earth to witness the process of continent-continent collision. Several seismic arrays have been operated in recent years to image this collision process. My participation has been directed toward imaging lithosphere-scale structure in northern and southern Tibet to understand how shortening is accomodated in the crust and in the mantle lithosphere.
The deep structure of Axial Volcano Axial volcano sits on the Juan de Fuca ridge a few hundred kms off the coast of Oregon/Washington. It has erupted several times in the past couple decades, most recently in 1998. It is of geologic interest because it sits at the intersection of the ridge system and the Cobb hot spot. In this project we are mapping the 3-D seismic velocity structure of the volcano to locate magma chambers and determine crustal thickness across the region. This information, together with recent geochemical analyses will help us understand how this volcano is sourced and why it erupts in the manner it does.
Structure of north rift zone, Iceland The northern rift zone of Iceland is the current center of spreading between the European and North American continent. Numerous volcanos, current and extinct, lie in this zone including Krafla volcano which has erupted several times in the past few decades. It is the type locality for en echelon volcanic rifting. This study examined a 200 km transect of the crust using explosive and earthquake sources recorded along a seismic array. It supported ideas about how new crust is created by channeling magma down the rift zone from large central volcanos. Observations were further confirmed by a re-examination of a previous gravity survey.
Traveltime calibration for Asia IMS stations The International Monitoring System (IMS) proposed by the Comprehensive Nuclear Test Ban Treaty includes a global seismic network of unprecidented scale. Though the U.S. has failed to ratify the treaty, we are keenly interested in developing the monitoring power of the IMS array. This project is small piece of the Lamont Consortium's effort to calibrate 30 IMS-proposed seismic stations in Asia. Specifically, this project created a three dimensional velocity model of central Asia to explore the strengths and pitfalls of traveltime calculation in this geographically diverse region.
Effect of crustal reflection on S-wave correlation Many modern seismic methods rely on cross correlating digital waveforms. These cross correlation methods can detect subtle changes in a signal that may not be clear by eye. In a common application, earthquake records from different in-coming directions are often compared for subtle traveltime differences that result from variations in crustal structure under that station. In addition to the direct arrival, a subsequent bounce from the surface and the bottom of the crust is often recorded a few seconds later. The degree to which this second phase interferes with the main arrival is the topic of this paper.
Proposed Andes Volcano Undershooting Experiment This ambitious project, which has yet to be funded, would be centered on an interesting section of the middle Andes. Very little work has been done to understand the complex transport of magma above subduction zones. Unlike mid-ocean ridges, melt may have to traverse 70 km or more to erupt in such a setting. There are several outstanding questions about how magma is emplaced in the crust, on top of the crust, or at the deep base of the crust. This project would help illuminate this process using a number of seismic imaging techniques.