Geophysics involves the application of physical theories and measurements to discover the properties of the earth. The discipline dates to antiquity, mainly as a scientific approach to earthquake prediction (a problem still unsolved), but major progress began in the late 1500s with initial work in such areas as magnetism and gravity. Tremendous improvements in instrumentation in the early years of the 20th century generated rapid progress in geophysics and ultimately led, in the 1960s, to the theory of plate tectonics. Plate tectonics, the study of the interior structure of the earth, and such related areas as global and regional processes are known collectively as solid earth geophysics. The subdiscipline known as exploration geophysics involves the use of geophysical theory and instrumentation to locate petroleum and other mineral sources. Unlike solid earth geophysics, exploration geophysics generally concentrates on finding lateral heterogeneities in a relatively small part of the earth's crust. Geophysics is considered by some to be a branch of geology, by others to be of equal rank. It is distinguished from the other earth sciences largely by its use of instruments to make direct or indirect measurements of the parts of the Earth being studied, in contrast to the more direct observations which are typical of geology. The following definitions are from Robert E. Sheriff's Encyclopedic Dictionary of Applied Geophysics. 1. The study of the earth by quantitative physical method, especially by seismic reflection and refraction, gravity, magnetic, electrical, electromagnetic, and radioactivity methods. 2. The application of physical principles to studies of the earth. Includes the branches of (a) seismology (earthquakes and elastic waves); (b) geothermometry (heating of the earth, heat flow, volcanology, and hot springs); (c) hydrology (ground and surface water, sometimes including glaciology); (d) physical oceanography; (e) meteorology; (f) gravity and geodesy (the earth's gravitational field and the size and form of the earth); (g) atmospheric electricity and terrestrial magnetism (including ionosphere, Van Allen belts, telluric currents, etc.); (h) tectonophysics (geological processes in the earth); and (i) exploration and engineering geophysics. Geochronology (the dating of earth history) and geocosmogony (the origin of the earth) are sometimes added to the foregoing list. 3. Often refers to solid-earth geophysics only, thus excluding (c), (d), (e), and portions of other subjects from the above list. 4. Exploration geophysics is the use of seismic, gravity, magnetic, electrical, electromagnetic, etc., methods in the search for oil, gas, minerals, water, etc., with the objective of economic exploitation.
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Airborne Geophysical Survey Workshop
A collection of papers covering the practical aspects of performing airborne magnetic, radiometric, and electromagnetic surveys.
EPA Dynamic Field Activities - Geophysical Methods
Common geophysical methods used by the Environmental Protection Agency at hazardous waste sites include: ground penetrating radar, seismic refraction, electromagnetics, and magnetometry. Presents case studies and field-based analytical methods.
The Exploration of the Earth's Magnetosphere
A detailed non-mathematical introduction to the research on the Earth's magnetic environment in space and its history. Contains master directory of many related text files.
Genetic Algorithms in Joint Inversion
Research discussing some of the advantages and disadvantages of using genetic algorithms for joint inversion of different geophysical datasets, particularly magnetotellurics and seismic receiver functions.
Online forum for geophysics issues related to environment, engineering, archaeology, hydrology, forensic and other near surface geophysical applications.
Research institute in New Zealand specializing in earth systems, seismic data acquisition and processing, laboratory analysis, environmental and natural hazards risk analysis.
The Great Magnet, the Earth
Historical review of geomagnetism, from the discovery of the compass to plate tectonics and space observations. Also has instructions for teachers, glossary, and FAQ.
Introduction to Magnetotellurics
A geophysical technique that uses naturally-occurring (or man-made) electromagnetic fields to probe the electrical conductivity structure of the Earth.
Magnetotellurics (MT) is a geophysical method to study the distribution of electrical conductivity in the earth. Article includes examples of recordings and resistivity ranges of standard rock types.
Magnetotellurics MT: Technique, Interpretation, and Application
A detailed article explaining the practical application of magnetotellurics. Includes case studies to present processing and interpretation techniques.
Michael Studinger's Homepage
Geophysical and glaciological research on the Antarctic continent with aerogeophysical methods.
An international electronic forum for the free exchange of knowledge, programs and data between scientists engaged in the study of the Earth using electromagnetic methods, principally magnetotellurics.
Multicomponent Seismic: A Pragmatist's Primer
Article discussing the different types of multicomponent seismic data, including geophone orientation, recording methods and successful applications.
Natural Resources Canada: Geomagnetism
Contains data on the ever-changing magnetic field. Includes a declination calculator and a database from Canadian magnetic observatories.
ORAD Laboratory for Satellite Altimetry
Specializes in the analysis of satellite altimeter data related to problems in physical oceanography and marine geophysics.
Origin of the Terrestrial Magnetic Field
Article by Andrija Radovic on how the Earth's geomagnetic field arises.
Seminar in Geophysics: Thermal and Chemical Evolution of the Earth
Course materials are available for download from MIT, this program studies the historical development and the current status of ideas and models from the different research fields, and investigates the different views on mantle flow.
A novel approach to the comprehensive elimination of multiples, which combines both waveform inversion (SDec) and statistical estimation (MSvE).
The Upper Mantle of the Earth
Information about the highly viscous layer between the Earth's crust and the lower mantle, including its internal structure, its material composition and associated natural phenomena.
USGS Geomagnetism Homepage
Provides background information on the earth's magnetism, geomagnetic field maps and data, and modelling information.
USGS Office of Ground Water, Branch of Geophysics
Technical support, guidance, and applied research that fosters the appropriate use of surface and borehole geophysical methods for USGS interdisciplinary earth science investigations and the development of geophysical characterization and monitoring methods.
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