A trio of Southern California earthquakes have occurred in the Newport Beach and Costa Mesa area in the past two days, and a pair rumbled Thursday afternoon.
The first earthquake on Thursday, at 4:52 p.m., occurred along the border between Newport Beach and Costa Mesa. The magnitude 3.6 tremor struck near Irvine Avenue and where Westcliff Drive in Newport Beach passes into East 17th Street in Costa Mesa.
This was followed by a magnitude 3.4 aftershock at 5:04 p.m., with the epicenter about three-fifths of a mile southeast, below the residential street Somerset Lane, a few blocks from Upper Newport Bay.
According to the U.S. Geological Survey, weak shaking, or level 3 on the modified Mercalli intensity scale, was felt in Santa Ana, Westminster, Huntington Beach, Garden Grove and Irvine, as well as Newport Beach and Costa Mesa. That jolt would produce vibrations similar to those of a passing truck, and could slightly sway more parked cars.
A preview of Thursday's earthquakes occurred on Wednesday at 1:46 pm. Originally estimated at a magnitude of 2.6 with its epicenter beneath Newport Beach's Mariners Park, it was updated to a magnitude of 2.8 and its epicenter moved a quarter mile northwest. , in a residential neighborhood of Costa Mesa.
The trio of earthquakes occurred near mapped traces of the Newport-Inglewood/Rose Canyon fault zone. The Newport-Inglewood fault has long been considered one of the highest seismic hazard zones in Southern California because it passes beneath some of the most densely populated areas in the region, from the west side of Los Angeles to the coast of the Orange County.
The last major earthquake on that fault occurred in 1933: the magnitude 6.4 Long Beach earthquake. The 1933 earthquake left almost 120 dead and caused property damage worth $40 million.
During the last week several earthquakes have been felt throughout the region.
A pair of earthquakes shook the El Sereno neighborhood of East Los Angeles earlier this week. The first was a magnitude 3.4 and occurred at 9:56 a.m. Sunday, a couple of blocks south of Huntington Drive and Eastern Avenue.
The second was magnitude 2.8, down from an earlier estimate of magnitude 3, and occurred at 3:05 p.m. Tuesday. Its last estimated epicenter was about 700 feet northwest of Sunday's earthquake.
On Friday, at 10:26 a.m., a magnitude 3.6 earthquake (below the original estimate of 3.8) occurred with its epicenter just north of the Ojai Valley, causing a weak tremor that was felt from Santa Barbara to Los Angeles.
Small earthquakes are not uncommon in Southern California. Most do not cause larger catastrophic earthquakes. And although some larger earthquakes are preceded by smaller earthquakes, this is not always the case.
Experts say it's impossible to know whether small earthquakes are harbingers of a larger quake before the more powerful event occurs.
