(CNN)Here's a look at earthquakes worldwide.
The US Geological Survey describes an earthquake as "the ground shaking caused by a sudden slip on a fault. Stresses in the earth's outer layer push the sides of the fault together. Stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the earth's crust and cause the shaking that we feel during an earthquake."
Earthquakes are measured using seismographs, which monitor the seismic waves that travel through the Earth after an earthquake strikes.
Scientists used the Richter Scale for many years to measure earthquakes but now largely follow the "moment magnitude scale," which USGS says is a more accurate measure of size.
Major Earthquakes since 2000
June 4, 2000 - A magnitude 7.9 earthquake strikes southern Sumatra, Indonesia, killing an estimated 103 people.
January 13, 2001 - A magnitude 7.7 earthquakes hits near San Miguel, El Salvador, killing an estimated 852 people.
January 26, 2001 - An estimated 20,000 people are killed by a magnitude 7.7 earthquake centered in Gujarat, India.
February 13, 2001 - Another earthquake strikes El Salvador, magnitude 6.6. Three hundred and fifteen people are estimated to have been killed.