Notable Earthquake of the Week

Elsinore M 6.0 Earthquake  

At 8:47 a.m., May 15, 1910, an earthquake registering about M 6.0 struck the east flank of the Santa Anna Mountains in Southern California.

The quake was centered roughly 52 miles southeast of Los Angeles in Temescal Valley, just northwest of Lake Elsinore, and registered Modified Mercalli Intensity readings of VII (a relative shaking intensity scale from 1-12 shown in Roman numerals).

Chimneys were shaken down over a wide region, including at Corona, Riverside, and Temescal. In the epicentral area, windows were shattered and cracks formed in walls, but no structural failures occurred. Glassware in Barstow, and San Diego was said to have jiggled.

It was preceded by a few moderate foreshocks and followed by a robust aftershock sequence which included a few moderate events. No surface fault ruptures were ever discover from this earthquake.

The quake triggered along the Whittier-Elsinore-Laguna Salada Fault Zone, a prominent northwest-trending strike-slip fault zone that extends from the Gulf of California to San Gabriel River (~300 km or 156 mi.), making it one of the longest fault zones in Southern California.

The Elsinore fault is subdivided into five segments: Whittier, Glen Ivy, Temecula, Julian, and Coyote Mountain. Slip rates along these segments average about 5 mm/yr., ranking it the forth most active fault behind the San Andreas, San Jacinto, and Imperial Valley faults. Reoccurrence of major earthquakes is between 240 and 760 years (ave. 400 yrs.) and has not produced a surface rupturing temblor in the past 200 years.

The Whittier fault forms the northernmost segment and has an average slip rate along the fault is about 2.5 mm/yr. The interval between major earthquakes along this segment is unknown. It was the site of the 1987 Whittier Narrows M 5.9 earthquake.

The Laguna Salada fault in northern Baja California, Mexico, has a slip rate of roughly 4 mm/yr and was the site of the powerful M 7.2 earthquake in 1896 which caused significant surface ruptures. The reoccurrence of major events on the Laguna Salada fault are unknown.

Seismo-Watch Earthquake Reports

Track weekly earthquake activity with the Seismo-Watch Earthquake Reports. Click here or on any of the reports below.

You can also track activity in Central California with the Brief CCA Earthquake Report, the Western Basin and Range, including the very active Mammoth Lakes region, with the Brief WGB Earthquake Report, and in Southern California with the Coachella Valley Earthquake Report.

Seismo-Watch Alert Bulletins are a great way to be informed right away when significant earthquakes occurs.