Earthquake location

There are several methods used to locate earthquakes, triangulation is one that uses distance information from 3 or more stations to uniquely locate an earthquake.For an earthquake at the surface there are three unknowns: latitude, longitude, origin time.Triangulation is a method that uses distance information determined from 3 seismic stations to uniquely locate the earthquake.
An earthquake location specifies the place and time of occurrence of energy release from a seismic event.The location may refer to the earthquake's epicentre, hypocentre, or centroid, or to another observed or calculated property of the earthquake that can be spatially and temporally localized.An earthquake epicenter can be located from records made of earthquake waves on devices called seismographs.
A location is called absolute if it is determined or specified within a fixed, geographic coordinate system and a fixed time base, a location is called relative if it is determined or specified with respect to another spatio-temporal object which may have unknown or uncertain absolute location.We can locate earthquakes using a simple fact: an earthquake creates different seismic waves (P waves, S waves, etc.) The different waves each travel at different speeds and therefore arrive at a seismic station at different times.
For rapid hazard assessment and emergency response, an earthquake location provides information such as the locality of potential damage or the source region of a possible tsunami, and a location is required to calculate most measures of the size of an earthquake, such as magnitude or moment.
Since earthquakes occur deep in the Earth, their source locations must be inferred indirectly from distant observations, and earthquake location is thus a remote-sensing problem.