This is how it was determined that the outer core consists of liquid. Unsaturated sediments have lower values than saturated sediments. Unconsolidated sediments have lower values than consolidated sediments. Velocities are very similar in saturated, unconsolidated sediments. Weathered rocks have lower values than similar rocks that are unweathered.
Fractured rocks have lower values than similar rocks that are unfractured.
The earthquake focus or hypocenter is the point where the earthquake originated. This location is specified bylatitude, longitude, and depth beneath the surface. The location of earthquakes are determined from at least three seismic stations. Given a single seismic station, the seismogram records will yield a measurement of the S-P time. This will allow the distance between the station and the event to be located.