Geophysical instruments are used for geological study, including rock and soil mechanics, and surveying the earth. Geological study can be subdivided into categories such as geophysics, geochemistry, mineralogy, hydrology, geomorphology. One area of geological study is seismology, the study of earthquakes (a sudden, sometimes violent movement of the earth’s surface from released energy in the earth’s crust) and related phenomena. Geophysical instruments for seismology are helping scientists learn more about the structure and properties of the earth’s crust and the causes and predictors of earthquakes. The use of geophysical instruments for earth quake detection is especially important.