The lithosphere, i.e., the crust and the upper parts of the mantle beneath, can be effectively studied using seismic waves that propagate through the subsurface and reflect and refract from the interfaces (or internal boundaries) within the subsurface. These seismic soundings use for example explosions and vibrators trucks as sources. The seismic waves traveling through the subsurface are recorded on the surface using geophones (on land) or hydrophones (on water).
The structure of the lithosphere can also be studied using seismic tomography which uses seismic signals from mining and road construction explosions or even earthquakes to "x-ray" the earth's crust and mantle. Field work is usually done in international collaboration since it requires large resources (staff, hardware, diverse know-how).