Geophysical analyses encompass a broad range of studies and techniques that seek to image the region beneath the surface of the Earth by means of the interpretation of physical parameters, waves, or fields measured at the Earth's surface. Physical quantities commonly measured include gravitational acceleration, geomagnetic field, rock magnetism, electrical conductivity, electromagnetic fields from both natural or manmade sources, seismic waves from explosions or earthquakes, heat flow, and many others. Because most individual geophysical techniques provide fuzzy or ambiguous images of the subsurface, effective interpretations are commonly based on a number of techniques used in tandem. The Mineral Resource Program (MRP) maintains capabilities in remote sensing, imaging spectroscopy, gravity, magnetic, electrical, electromagnetic, gamma-ray, magnetotelluric, and ground-penetrating radar techniques. These methods are applied in mineral resource, mineral environmental, and general geologic investigations. The Geophysical Unit in Menlo Park (GUMP) has members who specialize in gravity, magnetic, electrical, electromagnetic, and paleomagnetic techniques applied to the solution of geologic problems. Gravity and magnetic techniques are effective in urban or other developed areas, places where many important problems are encountered but where many geologic and geophysical methods are rendered ineffective due to cultural "noise". Geophysical databases Aeromagnetic--Efforts are being made to archive on CD-ROM all the digitized aeromagnetic data from early analog surveys that have been used in various whole state compilations. Target date for release to the public is January 2000. A reference database containing all the specifications for most public domain airborne geophysical surveys has been established. It is currently being annotated to show which surveys have been digitized. Whole state aeromagnetic maps have been compiled for many of the western states. It is expected they will be released on the World Wide Web before the end of 1998. Selected Bibliography Bibliographies and location maps of selected publications containing airborne geophysical data are available as Open-File Reports 91-370-A through F. Most states have been updated and draft copies of individual states can be obtained for internal use only. General Contact: Victor F. Labson USGS, MS 964 Denver Federal Center Denver, CO 80225 (303) 236-1312 vlabson@usgs.gov GEO-CRG-MRS Regional and Geologic Expertise Alaska -- Morin, Saltus, Kulik, Campbell Antarctica -- Finn Arizona -- Gettings, Finn, Phillips Northern California --J achens Southern California -- Langenheim Colorado -- Bankey, Campbell Eastern States -- Daniels, Snyder Florida -- Fitterman Hawaii -- Hildenbrand Idaho -- Bankey, McCafferty Mid-continent -- Hildenbrand, Daniels, Phillips Montana -- McCafferty, Bankey Nevada -- Ponce, Grauch, Saltus New Mexico -- Grauch Pacific Northwest -- Blakely, Finn, Blank Utah - Bankey, Campbell Wyoming -- Kucks, Finn Process Expertise Basin analysis -- Ponce, Saltus, Phillips, Grauch Earthquake related processes -- Hildenbrand Ground water studies -- Langenheim, Grauch, Fitterman, Lucius, Powers, Horton, Campbell, Bisdorf Mineral resources -- Jachens, Daniels, Saltus, Bankey, Wynn, Grauch, Gettings, McCafferty, Smith, Duval, Kulik, Blank, Kleinkopf, Phillips, Knepper, Livo, Rowan, Crowley Mineral environmental studies -- McCafferty, Campbell, Knepper, Livo, Swayze, Clark, King, Kolaly, Rowan, Crowley Plate tectonics -- Blakely Volcano-related processes -- Blakely, Finn

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