how are earthquakes measured

Earthquakes are primarily measured by two main concepts: magnitude and intensity. Magnitude measures the total energy released by an earthquake and is estimated using data from seismograms, which record ground motion vibrations. The most widely used scale today is the moment magnitude scale, which calculates magnitude based on physical factors like the area of the fault that slipped, the distance the fault moved, and the rock's rigidity. Seismometers detect and record these vibrations as seismograms to provide data for magnitude calculation. Intensity measures the strength of shaking at specific locations and is described using the Modified Mercalli Intensity scale with values from I (barely felt) to X (widespread destruction). Intensity depends on the distance from the earthquake epicenter and local geological conditions. The Richter scale, developed in 1935, was the first numerical scale to measure earthquake magnitude based on wave amplitudes but is largely replaced today by the moment magnitude scale, which is more accurate for large earthquakes. Thus, earthquakes are measured by recording ground vibrations with seismometers and interpreting these signals to quantify both the total energy released (magnitude) and the shaking experienced locally (intensity).