3.5-magnitude earthquake rattles Southern California awake. ‘My heart dropped’

A 3.5-magnitude earthquake rattled parts of Southern California awake Friday, May 13, geologists said.

The earthquake shook Palomar Observatory at about 6:30 a.m., according to the U.S. Geological Survey. The 4.6-mile deep earthquake could be felt about 64 miles away in San Diego.

The earthquake was smaller than some California residents may be used to, but more than 700 people reported feeling the earthquake to USGS. Several people said on social media they were rattled awake by it.

“Earthquake San Diego? my heart dropped,” a person on Twitter said.

“Woke up to my bed shakin,” one person said.

Other people thought it was ironic the earthquake struck on Friday the 13th.

“Earthquake in San Diego again???? On Friday the 13th of course,” another person said.

Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.

Quakes between 2.5 and 5.4 magnitude are often felt but rarely cause much damage, according to Michigan Tech. Quakes below 2.5 magnitude are seldom felt by most people.