Michael West

Lamont-Doherty Earth Observatory
of Columbia University

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 volcanos. 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.

My work tries to illuminate the roots and plumbing of volcanos. The principle set of techniques I use image the subsurface with seismic waves. The approach is similar to how a CAT scan images the brain. The structural information, combined with other geophysical data, geochemistry and eruptive history helps explain the origin and transport of magma from its source to the surface.

The deep structure of Axial volcano (in progress)
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.