Geologists determine the location of an earthquake's epicenter primarily by using seismograph data to triangulate the distance from multiple seismic stations. When an earthquake occurs, it generates seismic waves that are recorded by seismometers at various locations. By measuring the time it takes for these waves to reach each station, geologists can calculate the distance from each station to the epicenter. By collecting data from at least three different seismic stations, they can use triangulation to pinpoint the precise location of the epicenter on the Earth's surface.
The other options listed are not methods used for this purpose:
- The Mercalli scale measures the intensity of shaking and its effects, not the epicenter.
- Analyzing rock composition does not help locate an epicenter.
- Observing surface rupture gives information about the fault but is not a primary method for locating the epicenter.