<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="1050" name="seismology" parent="470" scope="Branch of earth sciences concerned with the study of earthquakes and man-induced seismic waves."/><uf><usefor name="earthquake seismology"><usewith><term thcode="2" code="299" name="earthquake occurrences" parent="304" scope="Time, location, severity, and mechanism of earthquake events, including the frequency and history of events in a given area."/></usewith></usefor><usefor name="engineering seismology"><usewith><term thcode="2" code="339" name="engineering sciences" parent="1019" scope="Sciences involved in the application of scientific and mathematical principles to construction, machinery, mechanical design, mining and manufacturing processes and other practical activities."/></usewith></usefor><usefor name="exploration seismology"><usewith><term thcode="2" code="774" name="natural resource exploration" parent="1174" scope="Techniques for locating deposits or stocks of useful minerals, water, and other resources using reconnaissance or instrumental methods."/></usewith></usefor></uf><bt><term thcode="2" code="470" name="geophysics" parent="291" scope="Branch of geology studying the physical characteristics and phenomena of the earth and its atmosphere."/><term thcode="2" code="291" name="earth sciences" parent="1019" scope="Broad term for all science related to the study of the earth."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="862" name="paleoseismology" parent="1050" scope="Branch of seismology concerned with ancient earthquakes.  Clues which indicate seismic activities in the geologic past are used  to date and determine the effects of those earthquakes."/></nt><rt><term thcode="2" code="299" name="earthquake occurrences" parent="304" scope="Time, location, severity, and mechanism of earthquake events, including the frequency and history of events in a given area."/><term thcode="2" code="304" name="earthquakes" parent="451" scope="Ground shaking caused by the sudden release of accumulated strain by an abrupt shift of rock along a fracture in the earth or by volcanic or magmatic activity, or other sudden stress changes in the earth."/><term thcode="2" code="1042" name="seismic methods" parent="375" scope="Procedures used to record and study earthquakes or earth vibrations including those that are artificially induced."/><term thcode="2" code="1043" name="seismic networking" parent="1042" scope="Deploying, operating, and maintaining groups and arrays of instruments for detecting and describing local movements of the earth."/><term thcode="2" code="1045" name="seismic reflection methods" parent="1042" scope="Geophysical technique to study the subsurface of the earth using sound waves induced by explosives, vibrating devices, or percussive equipment.  The reflections of the sound waves from the boundaries of different rocks are measured."/><term thcode="2" code="1047" name="seismic refraction methods" parent="1042" scope="Geophysical technique to study the subsurface of the earth by generating compressional waves by means of hammering or explosive methods. The variations in velocity of the waves traveling through rocks or geological layers are measured."/><term thcode="2" code="1145" name="tectonic processes" parent="451" scope="The structural forces affecting the deformation, uplift, and movement of the earth's crust."/><term thcode="2" code="1169" name="tiltmeter measurement" parent="375" scope="Determination of tiny changes in the slope angle or tilt of the ground in order to monitor deformation caused by moving magma. Instruments detect variations in a liquid level or in the position of a pendulum."/><term thcode="2" code="1195" name="tsunamis" parent="822" scope="Sea waves generated by submarine earthquakes, volcanic eruptions, or landslides, which are generally imperceptible in deep water but may be very destructive when striking the shoreline."/><term thcode="2" code="1289" name="volcanology" parent="464" scope="The branch of geology that deals with volcanism and the processes involved in magma flow and eruption through a vent in the earth's surface."/></rt></descriptor>