Teleseismic earthquakes occur at distances greater than 1,000 km from the measurement (seismograph) site.
P and S waves are refracted and speed up in faster layers at depth. Even from long distances, teleseismic (more than 500 km away) earthquakes are recorded by sensitive seismograph stations. An earthquake from Chile is recorded by a seismograph station at Mount St. Helens, WA
Seismograms of common events are compiled to show the different seismic signals recorded by ground-shaking events. Seismograms can record everything from nearby earthquakes to earthquakes on the other side of the world, plus anything that shakes the ground near the seismograph station like people walking, elk running, rocks falling and helicopters landing.
