A preliminary magnitude-4.3 earthquake and smaller quakes in the San Bernardino area produced shaking Thursday morning that was felt over widespread parts of Southern California.
The quake, reported at about 9:30 a.m., was one of four of magnitude-2.5 or greater just west of San Bernardino, a region that includes the communities of Fontana, Muscoy and Rialto.
A magnitude-3.0 quake was reported at 8:34 a.m. in the San Bernardino County community about 50 miles east of Los Angeles. Shaking was reported in Riverside, San Bernardino and other inland areas.
The second stronger quake was reported at about 9:30 a.m. Shaking was reported in Los Angeles, Santa Monica, Torrance, Long Beach, Pasadena and other areas.
The initial magnitude changed several times as more data became available.
A magnitude-3.1 aftershock was reported about four minutes later.
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Several smaller earthquakes have been reported Thursday morning before and after the largest shock. Aftershocks, the sequence of quakes after a larger mainshock, become less frequeNt over time, but can continue for days, weeks, months and even years after a powerful mainshock.
The area has seen about 130 quakes of magnitude 3.0 and greater since 1990, many coming in clusters. There have been eight quakes of magnitude-4.0 since that time.
“This is a very active region,” said seismologist Dr. Lucy Jones, adding that Thursday’s activity was standard fare for Southern California and its vast network of earthquake faults.
There were no reports of significant damage.
Whether you feel shaking from an earthquake largely depends on three major factors — magnitude, distance and local soil conditions.
Magnitude refers to the strength of the quake. The closer your location to the epicenter, the more likely you’ll feel the effects of seismic waves that become less intense as they move out from the fault. Generally, the looser the soil under your location, the greater the amplification.
Did you feel it? Let us know below.
MagnitudeDateLocationNotes7.9Jan. 9, 1857Fort TejonTwo killed; 220-mile surface scar7.8April 18, 1906San FranciscoPossibly 3,000 killed; 225,000 displaced7.4Mar. 26, 1872Owens Valley27 killed; three aftershocks of magnitude 6 or greater7.4Nov. 8, 1980EurekaInjured 6; $2 million in damage7.3July 21, 1952Kern County12 killed; three magnitude 6-pluys aftershocks in five days7.3June 28, 1992LandersOne killed; 400 injured; $9.1 million in damage7.2Jan. 22, 1923MendocinoHomes damaged in several towns7.2April 25, 1992Cape Mendocino356 injuries; $48.3 million in damage7.1Nov. 4, 1927LompocNo major injuries; light damage in two counties7.1Oct. 16, 1999LudlowMinimal damage due to remote location7.1July 5, 2019Ridgecrest/TronaPreceded by 6.4-magnitude quake; no fatalities7.0May 18, 1940El Centro9 killed; $6 million in damage6.9Oct. 17, 1989Bay Area63 killed; 3,753 hurt; up to $10 billion in damage6.7Jan. 17, 1994Northridge57 killed; 9,000 hurt, up to $40 billion in damage6.6Feb. 9, 1971San Fernando65 killed; 2,000 injured; $505 million in damage6.4March 10, 1933Long Beach115 killed; led to new building codes for schools
Credit: California Department of Conservation
