Geophysicists aim to understand the dynamics of the Earth through research on the physical processes, properties, and structure of the planet on which we live. The Geophysics group at UC Davis is involved in a diverse spectrum of research activities including geodynamics, marine geophysics, seismology, paleomagnetism, geodesy, natural hazards, and tectonics. In their research, faculty and students in geophysics use theoretical modeling, computer simulations, data analyses, laboratory experimentation, and land and marine field observations. The following is an introduction to our faculty and what we do.

Magali Billen (Ph.D. California Institute of Technology, 2001) - Most of the interior structure of the Earth's mantle, including its geophysical and chemical properties can not be measured directly. Instead, these properties are inferred from a combination of indirect measurements, laboratory experiments and numerical models. My primary research interest focuses on using numerical models to test hypotheses about the spatial and temporal variations in the physical properties of rocks within the earth. This is done by comparing predictions from numerical models to observations made at the earth's surface from geophysics (e.g. topography, tomography, strain-rates), and geochemistry (e.g. temperature and pressure of melting, water content, age of deformation) and geology. In using geodynamic models in this way, examples of how the Earth has deformed in the past provide an important guide to interpreting model results. This leads me to my second research focus, plate tectonics, or more specifically, making geophysical observations which help to constrain both when and how tectonic plates have moved and deformed.

Louise Kellogg (Ph.D. Cornell University, 1988) - The solid Earth is in a continual state of deformation both in the deep interior as well as at its surface. I am interested in both "why" and "how" this deformation occurs. One major component of my research is to use computers calculations to study convection in the deep mantle. This work includes studies of the evolution of mantle plumes, models of thermo-chemical convection near Earth's core-mantle boundary, as well as investigations of mantle stirring and mixing over geologic time. Mantle convection is also important in that it drives plate tectonics, deforms the crust, and generates earthquakes. Deformation of the Earth's surface is the second major area of my research. My graduate students and I have been using the Global Positioning System (GPS) satellite network in conjunction with numerical models to understand the way the Earth's lithosphere deforms and how faults break.

Jim McClain (Ph.D. Washington University, 1979) - I exploit a variety of geophysical techniques, in conjunction with geological observations, to understand the structure and evolution of the Earth's crust. I examine problems using seismic refraction and earthquake data, as well as magnetic and gravity measurements. Much of my work has focussed on the mid-ocean ridges, with particular emphasis on how magma is stored and how this affects hydrothermal systems along the axis of mid-ocean ridges. We at UC Davis were the first to show that ridge magma chambers must be narrow, and that hydrothermal systems are accompanied by extensive microseismicity. Most recently we are using these geophysical tools to study transform faults as well as underwater volcanoes that erupt near mid-ocean ridges. With my students, I have recently moved onto the continents, with projects in the Monterey Bay, the central California coast, and, in the near future, northeastern California.

John Rundle (Ph.D., University of California, Los Angeles, 1976): Interdisciplinary Professor of Physics, Civil Engineering and Geology. Director, Center for Computational Science and Engineering - Research interests include: Numerical simulations of high dimensional drive threshold systems; Pattern analysis of complex systems; Dynamics of driven nonlinear Earth systems; Adaptation in complex systems.

Don Turcotte - (Ph.D. Caltech 1958) - Application of dynamical systems to geological problems, including crustal deformation, seismicity, topography, forest fires. Geodynamics, including mantle convection and the forces that drive the plates and result in seismicity, volcanism, and mountain building at the earth's surface. Planetary geology and geophysics, especially the interpretation of data returned from various planetary missions.

Ken Verosub (Ph.D. Stanford, 1973) - In recent years, the focus of my research has expanded from studies of magnetostratigraphy, tectonic rotations and geomagnetic field behavior to environmental magnetism, a new field of geophysics that uses the magnetic properties of soils and sediments as tracers of environmental and paleoclimate processes. At the present time, the paleomagnetism group is working on samples collected in China, Russia, Israel, Hungary, Argentina, New Zealand, Australia, Tahiti, South Africa, Canada and Antarctica as well as on samples taken from cores from all of the world's oceans and several of its major seas and lakes. In many cases, these projects involve travel to distance lands and close collaboration with scientists in other countries. Students who join the paleomagnetism group will work with state-of-the-art equipment in one of the best-equipped paleomagnetic labs in the country. For most projects only a basic physics and geology background is needed.

Gary Acton (Ph.D. Northwestern, 1990): Associate Research Geologist - My main interests are in the fields of geomagnetism, plate tectonics, geodynamics, and paleoclimatology, and their interactions and linkages. My current research focuses on understanding the interaction between climate, orbital modulation, and the geomagnetic field; estimating plate and hotspot motions to place constraints on global geodynamics; determining the rock magnetic properties of the upper oceanic crust to investigate the evolution of the crust and its role in generating marine magnetic anomalies; determining the evolution of incipient oceanic rifts; and studying short-term changes in the direction and intensity of the geomagnetic field.

Gerald Bawden (Ph.D., UC Davis, 1998): Research Associate - Research involves a multidisciplinary approach to study how and where the surface of the earth deforms before, during, and after earthquakes. I utilize the modern space based geodesy techniques of Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR), to "see" where the earth may be deforming and by how much.

Donna Eberhart-Phillips (Ph. D. Stanford University, 1989): Research Associate - Modelling of three-dimensional seismic velocity structure and material properties; and seismotectonic analysis of active deformation. Motivated to integrate 3-D velocity and attenuation models with other geophysics and to use 3-D velocity models to understand the effects of heterogeneous material properties, to extend beyond simply interpreting crustal structure. Current research efforts have focused on New Zealand and Alaska, with emphasis on understanding subduction processes and the transition from subduction to collision. Recent work with imaging 3D attenuation structure is valuable for interpreting tectonic processes that involve fluids, and also has application to engineering response spectra.

Jeffery Roberts (Ph.D., Arizona State, 1992): Research Associate - Mineral and rock physics. Transport in minerals, impedance spectroscopy and electrical properties of materials. Current research on olivine-basalt and olivine-iron sulfide partial-melts includes microtomographic imaging and visualization, permeability determination and melt migration. Also performing research in support of engineered geothermal systems, specifically fracture creation, permeability evolution and preservation.

Rob Twiss (Ph.D. Princeton, 1971): Professor Emeritus - My interests are in understanding deformation mechanisms in rocks, the structures that result from them, and how one can use the structures to infer the characteristics of the deformation. Most recently I have been studying brittle deformation in the Earth's crust associated with faulting and earthquakes. My research group and I have developed a technique to infer geometry of crustal strain using both seismic focal mechanisms and fault-slip field data. This method is being applied to studying the deformation and tectonics associated with earthquake aftershock sequences (e.g. Loma Prieta, Landers, Northridge) and regional tectonics (e.g. northern California Coast Range, eastern California Shear Zone, Pacific Northwest).

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