Research
John W. Schlue, Associate Professor of Geophysics

My interest in how the crust and upper mantle of the earth are modified in an extensional tectonic regime makes the Rio Grande rift a perfect setting for my research. One focus of this work is our use of seismic observations to describe how magma migrates through the upper mantle to the mid-crustal magma body discovered by Prof. Allan Sanford. Does the magma flow through discrete, narrow conduits, or does it diffuse to the mid-crust through a wide-spread zone of partial melt? Our recent attempts toward answering this question have included the efforts of colleagues from New Mexico State University, the University of Wisconsin, and the Los Alamos National Laboratory in cooperative projects of recording and analyzing P and S waves from distant earthquakes. Our initial results are not conclusive but are beginning to show discrete structure on the underside of the magma body that may be related to its plumbing system. A planned tomographic study of the shear-wave structure beneath the magma body should provide further insights.

Another question is concerned with the evolution of the Rio Grande rift through time. Here, we have used teleseismic shear-wave phases (SKS, SKKS) at several stations within the rift to infer the magnitude and direction of upper-mantle anisotropy. Results of this study can be interpreted as showing a north-south flow of material in the uppermantle as the rift opens to the north, rather than an east-west flow that might be expected from a simple model of east-west extension.

In addition to my seismic interests, I also use resistivity and frequency-domain electromagnetic techniques for obtaining estimates of apparent soil conductivities at shallow depths. Such measurements are useful in geophysical surveys, soil-moisture calculations, and pollution studies.