and Orange counties - could kill 3,000 to 18,000 people, according to the USGS and Southern California Earthquake Center. A magnitude 7.5 quake on the Puente Hills fault - which runs underneath highly populated areas of L.A. In Northern California, a simulation of a magnitude 7 earthquake on the Hayward fault east of San Francisco showed that there could be at least 800 deaths from the quake, plus hundreds more from fires afterward.Įither scenario would result in the deadliest earthquakes to hit California in more than 100 years. Geological Survey simulation of a magnitude 7.8 earthquake in Southern California led researchers to determine that it was plausible such a quake could cause nearly 1,800 deaths and 50,000 injuries, and destroy major utilities carrying fuel, power and water. In California, a magnitude 7.8 quake would produce damage far more widespread than was caused by the tremblors of the past century. "And then when you have a significant aftershock come through, then they actually collapsed. "So the building gets weakened by the first earthquake," she said. The initial signs of building weakness can be observed when big diagonal cracks, looking like the letter X, are visible in the building. "We often call them a doublet," Scharer said. Scharer traveled to the site of a magnitude 7.1 earthquake in 2011 in eastern Turkey, which produced intense shaking under the city of Van a subsequent, less-powerful quake caused additional damage. Whether from one quake or two, "the longer the duration, the better the chance a building is going to collapse," Cocke said. The magnitude 7.5 aftershock occurred around 1:24 p.m. Some of the collapses in Turkey occurred many hours after the predawn mainshock. Experts say new buildings in Turkey - when properly built to local codes - are comparable to California's standards. But they also show that many others survived the shaking. Videos and photos from Turkey and Syria show building of various eras - some old, some modern - collapsing. One showed a building wobbling, followed by concrete falling out of a ground-floor column the columns then flexed, and the upper floors crashed down, sinking into a cloud of dust.Ī concrete school in Mexico City that collapsed in that quake killed 19 students and seven adults. Similar videos emerged after a magnitude 7.1 earthquake in 2017 struck Mexico. More concrete buildings suffered significant damage in the 1994 Northridge quake.ĭavid Cocke, president of the Earthquake Engineering Research Institute and a structural engineer with Gardena-based Structural Focus, said some of the collapsed buildings he has seen in news footage from Turkey appear to have been constructed from non-ductile concrete, in which inadequate steel reinforcing bars allow concrete to explode from columns when shaken. Minimum construction requirements were strengthened in the years after the Sylmar quake, but those rules affected only new construction. When the concrete Veterans Administration Hospital in San Fernando pancaked in the 1971 earthquake, 49 people were killed. They have long warned about the risk of brittle, concrete buildings collapsing, as occurred during the 1971 Sylmar and 1994 Northridge quakes. The collapses could also be due to corruption in safety inspections or incompetence in design practices - issues that have come up in Mexico, Taiwan and New Zealand.īut structural engineers have said that a big quake in California would also be devastating, if not on the same scale. Some of the structures may have been built before the advent of modern building codes. The scale of the building collapses in Turkey and Syria, some captured on video, could be attributed to a number of factors. Compared to the long-term average, we've been quiet for a while." And there's no way to say when it's going to be happening. "The timing of them, as far as we can tell, is random. We have the faults, we've seen it in the past, it will happen again," said seismologist Lucy Jones, a research associate at Caltech. Two of those have occurred on the San Andreas: the 1906 earthquake that destroyed much of San Francisco and the 1857 quake that ruptured a length of the fault from Monterey County through Los Angeles County and into the Cajon Pass. Geological Survey research geophysicist Kate Scharer. We’ve had a great run without them, but it’s important to be prepared for these possibilities in the future," said U.S. "We’ve had 7.8 earthquakes in our historic past. The San Andreas fault is capable of similar activity.
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