When you hear about an earthquake, you usually hear about its magnitude, or strength, on the Richter scale.
But there’s another way to measure an earthquake. Intensity tells us how much damage was done: buildings crushed, human lives lost, and so on. Intensity and magnitude can be very different. That’s because an earthquake of small magnitude can do a lot of damage in a region that isn’t prepared—and vice versa.
Intensity is measured by the Modified Mercalli Intensity Scale. Invented in 1902 by Italian seismologist Giuseppe Mercalli, it uses numbers to help explain events. The scale ranges from I (not felt) to XII (total destruction).
Magnitude is measured with a seismograph. That’s a device that records tremors in the Earth. It has a hanging weight that does not move when the Earth around it moves. The rest of the machine does move, and that movement is written down by a pen and paper attached to the device.
