{"thcode":2,"term":{"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."},"uf":[],"bt":[{"code":1042,"name":"seismic methods","parent":375,"scope":"Procedures used to record and study earthquakes or earth vibrations including those that are artificially induced."},{"code":375,"name":"field inventory and monitoring","parent":376,"scope":"Repeated observation or sampling at a site, on a scheduled or event basis, for study and analysis.  In general, this category excludes sampling programs in which materials are obtained in the field and brought back to a laboratory for study and analysis."},{"code":376,"name":"field methods","parent":734,"scope":"Research procedures and instrumental means to measure, collect data and samples, and observe in the natural areas where the materials, phenomena, structures, or species being studied occur."},{"code":734,"name":"methods","parent":1,"scope":"Techniques, methods, procedures, or strategies for research, management, collection, or analysis of scientific information in 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":[],"rt":[{"code":1050,"name":"seismology","parent":470,"scope":"Branch of earth sciences concerned with the study of earthquakes and man-induced seismic waves."},{"code":2054,"name":"sub-bottom profiling","parent":1045,"scope":"Methods of imaging the structure of sediments below the sea floor  or lakebed using ship-borne or towed sensors with a variety of sound sources."}]}