3 Days After Earthquake In Chile, South America

Measuring and locating earthquakes
Earthquakes can be recorded by seismometers up to great distances, because seismic waves travel through the whole Earth's interior. The absolute magnitude of a quake is conventionally reported by numbers on the Moment magnitude scale (formerly Richter scale, magnitude 7 causing serious damage over large areas), whereas the felt magnitude is reported using the modified Mercalli intensity scale (intensity II–XII).
Every tremor produces different types of seismic waves, which travel through rock with different velocities: