{"thcode":2,"term":{"code":470,"name":"geophysics","parent":291,"scope":"Branch of geology studying the physical characteristics and phenomena of the earth and its atmosphere."},"uf":[{"name":"geophysical maps","usewith":{"code":700,"name":"maps and atlases","parent":808,"scope":"Representation, usually on a flat surface, of a part or whole of the Earth or other parts of the universe.  Collections of maps linked digitally or bound together in a book are called atlases."}}],"bt":[{"code":291,"name":"earth sciences","parent":1019,"scope":"Broad term for all science related to the study of the earth."},{"code":1019,"name":"sciences","parent":1,"scope":"Major educational fields, fields of study, and professional groupings within USGS."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[{"code":440,"name":"geodesy","parent":470,"scope":"Branch of science dealing with measuring the earth or large areas of the earth for making maps, determining the size and shape of the earth, and correlating gravitational, geological, and magnetic surveys of the earth."},{"code":707,"name":"marine geophysics","parent":470,"scope":"Branch of earth sciences concerned with the physical processes of the oceans and continental margins.  We include here studies of large bodies of brackish and fresh water, such as lakes and rivers."},{"code":1050,"name":"seismology","parent":470,"scope":"Branch of earth sciences concerned with the study of earthquakes and man-induced seismic waves."},{"code":1147,"name":"tectonophysics","parent":470,"scope":"Branch of geophysics concerned with the structural forces affecting the deformation, uplift, and movement of the earth's crust."}],"rt":[{"code":225,"name":"Curie temperature analysis","parent":860,"scope":"Analysis of rock specimens using the Curie temperature point above which ferromagnetic materials lose permanent magnetism."},{"code":125,"name":"borehole logging","parent":375,"scope":"Method of recording the physical characteristics of the subsurface as a function of depth by observations during drilling of a well or borehole, studying the resulting core, or by lowering instruments into a drilled hole."},{"code":126,"name":"borehole temperature logging","parent":125,"scope":"Method of recording the measured temperature of the subsurface as a function of depth by lowering instruments into the hole."},{"code":211,"name":"core (earth)","parent":292,"scope":"The superdense center of the earth composed of two layers: a liquid outer layer and a solid inner core of metallic iron-nickel alloy."},{"code":501,"name":"gravitational field (earth)","parent":287,"scope":"Region or space around earth's mass which exerts a force that mutually attracts other masses in proportion to the product of the two masses and the distance between them."},{"code":2291,"name":"gravity gradient","parent":501,"scope":"Lateral variation of the three-dimensional vector components of gravity, typically measured using airborne sensors."},{"code":534,"name":"heat flow (earth)","parent":451,"scope":"Energy transferred by a difference in temperature through the surface of the earth."},{"code":590,"name":"inner core (earth)","parent":211,"scope":"The solid interior part of the earth's core, presumed to be composed principally of iron with an alloy of about 10 percent oxygen, sulfur, or nickel, or perhaps some combination of these three elements.  The inner core is about 1221 kilometers thick."},{"code":2298,"name":"inverse modeling","parent":713,"scope":"An iterative approach to estimate the form and characteristics of a physical system explained by observations or measurements. Frequently used to determine a subsurface geological structure from measurements of physical properties obtained at or near the earth's surface."},{"code":608,"name":"isostasy","parent":451,"scope":"Condition of equilibrium or buoyancy of the earth's crust above the mantle."},{"code":620,"name":"laboratory-induced magnetization analysis","parent":860,"scope":"Laboratory method to study rocks using magnetometers to measure remanent magnetic fields induced in the samples."},{"code":677,"name":"magnetic field (earth)","parent":287,"scope":"The magnetic region surrounding earth.  It is generated by the dipolar characteristic of earth's core whereby earth itself acts as a great spherical magnet with poles near, but not exactly at, the North and South poles."},{"code":678,"name":"magnetic hysteresis analysis","parent":860,"scope":"Nondestructive evaluation of ferromagnetic materials.  The evaluation is based on measurement of the variation of intensity of magnetization within an applied magnetic field due to changes in the magnetic domain structure of the materials under study."},{"code":680,"name":"magnetic susceptibility analysis","parent":860,"scope":"Nondestructive evaluation and location of magnetic materials in rock based on measuring the intensity of attraction of the materials to an induced magnetic field. Applications include geological and soil surveys, paleomagnetic studies, sedimentology, archaeological prospecting and core logging."},{"code":690,"name":"mantle (earth)","parent":292,"scope":"Zone of earth's interior between the crust and the core.  It is 2,900 kilometers (1,740 miles) thick and consists of a dense upper layer (upper mantle) and a partially molten lower layer (lower mantle), separated by a transition zone."},{"code":727,"name":"metamorphism (geological)","parent":451,"scope":"Process by which rocks are altered in composition and texture by extreme heat, high pressure, or the action of chemicals."},{"code":771,"name":"natural remanent magnetization analysis","parent":860,"scope":"Method which measures the intensity and direction of residual magnetism in rocks to determine their age and history."},{"code":849,"name":"outer core (earth)","parent":211,"scope":"Outer zone of the earth's core between the mantle and the inner core."},{"code":860,"name":"paleomagnetic analysis","parent":619,"scope":"Determination of the intensity and direction of residual magnetism in rocks to study changes in the earth's magnetic field during past geologic time."}]}