Earthquake jolts Hemet and Inland Empire

Residents shaken awake at 4:49 a.m.

■ Chronicle News Staff

A 4.5 magnitude earthquake centered 6.8 miles north of Cabazon awakened Hemet residents early Tuesday morning. At least 27 aftershocks followed, the largest of which was 3.2, the USGS said. There were no reports of injuries or damage.
The 4:49 a.m. earthquake was located six miles southeast of Mt. San Gorgonio and 19.3 miles northwest of Palm Springs at a depth of 8 miles. The magnitude was initially measured at 4.6 before being revised downward.
Some 10,000 people felt the temblor, besides residents of Hemet, people from San Bernardino, Banning, Lake Elsinore and Colton experienced the shaking. Even people as far away as Woodland Hills and Laguna Niguel felt it, according to news reports.
Seismologist Dr. Lucy Jones said the quake occurred under the San Bernardino Mountains near a complex part of the San Andreas fault. It was just east of the 1986 North Palm Spring quake that measured 5.9 magnitude.
“Historically, the area around Mt. San Gorgonio is the only part of southern San Andreas fault that produces smaller quakes,” Jones said on Twitter. “But the main San Andreas is not clearly defined here. At the surface, it disappears, covered by the Banning thrust fault.”
At a morning press conference held at the Caltech Seismological Laboratory in Pasadena, experts said the probability of a larger earthquake increases for the following week after a temblor such as Tuesday’s, but then gradually decreases.
The seismologists also said, however, that earthquakes in this magnitude range are seen in the San Andreas fault area every couple of years, known as the San Gorgonio Knot.
“The last one we had was a 4.4 back in January of 2016, so this isn’t unusual for this area,” said seismologist Dr. Jennifer Andrews.
Meantime, the earthquake experts gave a thumbs up to the ShakeAlert earthquake warning system. They said the warning arrived in the L.A. County area about 30 seconds before the strong-shaking hit.
In Riverside, the alarms went off about 8 seconds ahead of time and only 5 seconds ahead of time in Palm Springs.
As for any possible relation to the earthquakes and volcano activity in Hawaii, Caltech officials said there was no direct correlation.

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