Notable Earthquake of the Week
Landers, California, M7.3 Earthquake
At 4:57 a.m. on June 28, 1992, a very strong earthquake occurred in the High Desert of Southern California. The M7.3 earthquake was centered on the eastern side of the San Bernardino Mountains near the town of Landers in Homestead Valley. The quake was the largest to strike California since the Kern County M7.7 earthquake in 1952. (Click on the images to enlarge and see more photos here)
The quake was preceded a few months earlier by the Joshua Tree M6.3 earthquake on April 22 and followed by the Big Bear M6.4 earthquake at 8:05 a.m. later that day. A robust aftershock sequence followed and consisted of thousands of tremors, including 143 quakes registered M4.0 or stronger - 19 of which measured M5.0 or stronger. The most recent moderate aftershock was the Joshua Tree M5.0 earthquake on May 14, 1999.
Vigorous shaking was felt 100 miles away in Los Angeles and the quake was felt as far away as Central California and Las Vegas, Nevada. One person was killed, 25 were seriously injured and another 372 were treated for some sort of earthquake related injuries. The total property damage value was on the order of $56 million and included collapsed buildings, ruptured utility lines, and widespread nonstructural damage.
Three items of notable interest came out regarding this quake: 1) the quake ruptured disconnected surface traces of several known and a few unknown faults for a distance of 53 miles; 2) the displacement was two to three times larger than generally anticipated for these faults, with maximum horizontal offsets of 15-20 feet across a zone 30-60 feet wide; and as a consequent, 3) the magnitude was much larger than envisioned by seismologist and geologists for these individual faults.
Interestingly, elevated microseismicity was recorded throughout the western U.S. within minutes of the jolt and lasted for several months. Most notable was the Little Skull Mountain M5.6 earthquake near the Nevada Test Site and the proposed Yucca Mountain nuclear waste repository the day following the Landers quake and a M5.5 jolt on the Garlock fault on July 11. Elevated activity was also recorded volcanoes at Mammoth Lakes, Mt. Shasta and Yellowstone.
The largest historic earthquake in Southern California was the Fort Tejon ~M8 earthquake in 1852.
Images from the Southern California Earthquake Center (SCEC).
Visit the Landers Earthquake Page at the Southern California Earthquake Center
Seismo-Watch Earthquake Reports
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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.
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