Geophysics

Members of the Geophysics Group at UWM use techniques like gravity, magnetism, and seismology to study Earth’s deep structure; to interpret tectonic and volcanic processes; and to understand how Earth’s magnetic field changes in time and space. Geophysical techniques provide a window into the Earth, allowing us to examine everything from Earth’s innermost core to natural resources in the shallowest crust.

Julie Bowles

Julie Bowles

Dr. Julie Bowles, Assistant Professor

Specializes in Geophysics, Paleomagnatism

Research: Most of my research centers around the field of paleomagnetism—the study of Earth’s magnetic field as recorded in rocks and sediments. My work can be subdivide into three main areas: 1) understanding how Earth’s magnetic field has changed over time; 2) using these “rock records” of changing magnetic fields and magnetic properties to interpret volcanic processes; and 3) understanding how and how well magnetic minerals record the field.

  1. Earth’s magnetic field varies in both space and time. Characterizing and understanding those variations can help us to understand the processes in Earth’s core that generate the magnetic field. They can also help to provide constraints on planetary differentiation, inner core nucleation, and atmospheric evolution. Current work in this area involves using volcanic glass from the Juan de Fuca Ridge to better constrain field variations over the past few tens of thousands of years, and evaluating ignimbrites and other pyroclastic flows as potential field recorders over longer timescales.
  2. By comparing records of the Earth’s field recorded in igneous rocks with known variations in in the field, we can place some age constraints on lava flows or estimate whether or not two flows were likely erupted at the same time. Additionally, by studying the orientation of magnetic minerals in some igneous rocks like ignimbrites, we can learn something about flow direction and source location. Ongoing work in this area includes examining eruption timing and recurrence intervals on the Juan de Fuca Ridge and the Galapagos Spreading Center; and examining flow direction and post-emplacement rotations in pyroclastic flows.
  3. We use paleomagnetic data to provide constraints on tectonic reconstructions, geodynamo formation and behavior, planetary evolution, magmatic flow, and sub-solidus deformation. To reliably draw these kinds of conclusions, it is necessary to fully understand the mechanisms by which magnetic minerals form and acquire magnetization and the temperature at which this happens. How reliable are our paleomagnetic recorders? Recent work in this area has involved creating synthetic Mars rocks to better understand the strong magnetic anomalies on Mars; and creating synthetic basaltic glass to understand the timing of magnetite formation in submarine eruptions and its implications for the type of magnetization they acquire.
  4. Dr. Keith Sverdrup, Professor

    Specializes in Seismotectonics, Geoscience education in undergraduate oceanography

    Keith Sverdrup

    Keith Sverdrup

    Research: My research involves the relocation of historic earthquakes that have occurred in relatively remote regions where the azimuthal distribution of recording stations is poor, leading to in accurate relative and absolute locations. The most recent work has involved earthquakes along the Blanco Transform Fault separating the Pacific and Juan de Fuca plates off the northwest coast of the United States. Earthquakes in this region have historically been mislocated to the northeast due to the poor azimuth distribution of stations. Events along the transform are typically in the magnitude 5.5 or less range, small enough that only stations in the narrow azimuthal range from about 0 to 135 degrees record them well. This one-sided distribution of stations results in computed locations that are routinely tens of kilometers to the northeast of the actual locations.

    I have also worked on events in the Himalayas with Professor Cronin of Baylor University. My relocation methodology involves first grouping nearby events into clusters and then jointly relocating all of the events in a single cluster to mitigate the effects of errors that are common to all of them.

     

    Any interested MS or PhD students should feel free to contact any of the faculty members above.