How are earthquakes triggered and how are their magnitudes measured? What to know

Earthquakes can range from too small to be noticed to horrific natural disasters, and while they’re somewhat common in California they can strike almost anywhere.

Here are the basics you need to know about earthquakes.

What triggers an earthquake?

An earthquake is triggered when there is a sudden release of energy that then causes seismic waves and causes the ground to shake.

Dr. Julian Lozos, a seismologist and professor at Cal State Northridge, says earthquakes are a lot like people when they hold stress. They can have their coping mechanisms but at some point that stress will catch up and there will be a breaking point.

With earthquakes “the stress comes from plates trying to move and the faults are holding themselves together with friction,” which he says is like a coping mechanism for the fault.

“At a certain point a fault can’t take it anymore, it’s not strong enough to withstand all the stress coming from plate and movement and the friction gives way and at that point the fault unzips like a zipper,” Lozos said, which creates an earthquake.

How are earthquake magnitudes measured?

In the United States, the Modified Mercalli (MM) Intensity Scale is used to determine the magnitude of earthquakes. It replaces the old Richter Scale.

The scale classifies the intensity and the observed structural damages of an earthquake.

For example, a 3.0-magnitude tremor may be felt by people, especially those on upper stories, but it is often mistaken for something else, such as a passing truck, the scale shows. An 8.0-magnitude quake can cause considerable damage in poorly built or badly designed buildings and can cause chimneys to collapse.

This story was originally published December 21, 2022 at 11:28 AM.