DOE Physicists at Work
Profiles of representative DOE-sponsored physicists
doing research at universities and national laboratories
Compiled by the Office of Scientific and Technical Information
How do you figure out what is underground without digging a hole?
Maybe you want to find oil, or a gas line; manage underground contamination; or locate a tunnel. A geophysicist can make measurements at the earth's surface and use that information to estimate what's underground - the structure, composition, and distribution of soil, rocks, fluids, and voids.
"Geophysics is fun," says Patricia Berge, a geophysicist by training and now Division Leader for Earth Science within the Energy and Environment Directorate at Lawrence Livermore National Laboratory (LLNL). "It's also often cheaper, faster, safer, and more practical than digging holes." For instance, you may want to avoid excavations or drilling because you have a large area to cover, or it would be expensive to dig holes, or you might spread contaminants or disturb artifacts, or it would simply take too long.
"Now, the catch is what to measure and where," says Dr. Berge. "That is the challenge, the puzzle - where the fun really begins."
The basic idea is to identify some measurable physical property that can be observed at the earth's surface and a value that will change with changes in the subsurface. This is a combination of physics and earth science, requiring an understanding of the earth and earth materials as well as an understanding of physical properties. Examples of the physical properties geophysicists use for underground imaging are the speed of sound in rocks (seismic measurements), small local changes in the earth's gravity field, and electromagnetic properties of rocks and soils. Careful placement of measurement equipment and ready availability of fast computers makes it possible to estimate the three-dimensional picture of the subsurface from the geophysical measurements.
"Sometimes making the measurements can be tricky," says Dr. Berge. "When I worked at the U.S. Geological Survey, I flew in helicopters to put seismometers on rocky outcrops next to Alaskan glaciers." Over the course of her career, she's donned a wet suit to check a seismometer on the bottom of a lake; measured the speed of sound in the seafloor on a research ship that happened to be caught in a typhoon ("That part wasn't so much fun," says Dr. Berge); and taken measurements in 120-degree heat in Nevada.
With all the excitement geophysics offers, still Dr. Berge chose a management path in physics. "Although my own research was fascinating, I wanted to influence future directions of research at a larger scale and contribute toward solving bigger problems of concern to the taxpayers," says Dr. Berge.
Challenges include energy supply, environmental cleanup, hazard mitigation, and national security. "I would like to see the U.S. invest more research dollars in geothermal energy, cheaper and more effective monitoring of environmental cleanup, innovative hazard mitigation such as satellite-based tsunami warning systems, better methods for detecting and characterizing buried bunkers, and better methods for screening cargo containers," says Dr. Berge. "The world cannot afford to delay developing technical solutions to these difficult problems and it may take all the scientific expertise we have in the whole global population to make any progress at all," says Dr. Berge. "I became a manager in order to contribute to LLNL's vision for the future of earth science research, what areas we should be directing our efforts toward, where we should be going to solve problems that will be increasingly important over the next ten to twenty years."
Though most of these challenges are not within her subspecialty in geophysics, significant progress will require geophysics research and interdisciplinary work by large teams of scientists - and that's where management comes into play.
"As part of the management at LLNL, I can influence the future direction of research in earth science to be relevant to the nation's and the world's problems," says Dr. Berge.
Dr. Berge received a BS in Geophysics and an AB in History from Stanford University in 1982 and worked for the Seismology Branch of the U.S. Geological Survey until 1986. In 1991 she received a PhD in Geology and Geophysics from the University of Hawaii and then joined Lawrence Livermore National Laboratory as a postdoctoral researcher in the Earth Science Department. She was hired in a staff position at LLNL in 1994 and worked as a research geophysicist until 2002, when she assumed her current position.
Her research at LLNL focused on how things like sand grains, clay, fluid-filled pores, and cracks might influence the speed of sound and other physical properties. "I hope this basic research will help geophysicists to make better and better images of the subsurface, improving current techniques and inventing new ones for use in geothermal fields, environmental cleanup sites, and anywhere that we need to do underground imaging in the future," says Dr. Berge.
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