What happens when an earthquake occurs?
The earthquakes displayed on these maps and associated web pages have been detected and located by the University of Utah Seismograph Stations. Seismic signals are telemetered in real-time by radio and land lines from over 80 remote seismic stations in the region. Real-time computer systems continuously monitor the Earth for the occurrence of earthquakes. When an earthquake occurs, seismic waves are created, which propagate away from the focus or hypocenter. The fastest waves, the P-wave, travels outward at a speed of about 3 to 5 miles/second. As the P-wave passes each seismic station, its arrival time is detected and noted by the real-time computers. The computers use the list of arrival times to determine the location of the earthquake. The location is typically available within a minute or less after the occurrence of the earthquake. Once the location of the earthquake is known, a signal is sent to the computer that updates these web pages. Initially the magnitude may not be known,
