A 4.0-magnitude earthquake struck at 9:46 a.m. Sunday 3 miles west-southwest of the Palomar Observatory and was felt in Hill communities.
Seismologist Dr. Lucy Jones tweeted, “The depth is ~14km. That is the bottom of the brittle part of the [Elsinore] fault. The shallower part of the fault is ‘locked’ — no small quakes but building up stress for a big quake.
“The locked San Jacinto and Elsinore faults often have small quakes below the locked section. Somewhere in the Elsinore [fault] has a ~M4 below the locked section about once a year. So, this isn’t an everyday occurrence, but it isn’t unusual.”
A possible tsunami was listed on the U.S. Geological Survey’s app for the tremor, however, the National Weather Service’s National Tsunami Warning Center in Palmer, Arkansas, stated, “There is no tsunami danger from this earthquake.”