How do earthquakes get measured?

A seismograph records how the ground shakes when seismic waves pass through it. The first arriving waves, called P-waves, move faster than S-waves and can help locate the earthquake’s epicentre. Magnitude scales such as the moment magnitude scale estimate the total energy released, replacing the older Richter scale for most modern reporting. Earthquake magnitude is based on the physics of the rupture, not simply how strongly a building shakes at one place. The 1960 Valdivia earthquake in Chile remains the largest instrumentally recorded earthquake, at magnitude 9.5.