Pre-Northridge Earthquake. The Northridge earthquake struck on a previously unknown fault at 4:31 a.m. on Jan. 17, 1994.
Last year, Southern California experienced more than 11,700 earthquakes of measurable magnitude.To map the Puente Hills fault, the researchers at Harvard and Scripps analyzed seismic data gathered during the drilling of hundreds of commercial oil wells in the L.A. Basin, to which the researchers have recently gained access.In all, about 40,000 wells were drilled in the basin over the last 50 years to tap the oil and gas trapped in the region’s complex folds and faults, but only a fraction of the information gathered by petroleum company geologists has ever been made public.“This tends to be secretive data,” Shaw said. Building damage in the 1994 Northridge Earthquake was widespread, including collapses of both old and new structures. It runs in three segments from beneath downtown Los Angeles to the Coyote Hills in Orange County.John Nolan, an assistant director who died last week after a battle with COVID-19, worked on a commercial shoot in Texas. Like the Northridge earthquake, the smaller Whittier Narrows event of 1987 (M = 5.9) occurred on a blind thrust fault. With the conventions over, President Trump continues to trail Joe Biden.
It is very similar to the fault that caused the magnitude 6.7 Northridge earthquake, which killed 57 people, left 20,000 people homeless and did $40 billion in damage.
The reports include plots of the uncorrected accelerations (phase 1 data), instrumented and baseline‑corrected acceleration, velocity and displacement (phase 2 data), as well as response and Fourier amplitude spectra (phase 3 data). October 17, 1989: $10 billion.
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1980s 'Birds Eye view' of the West San Fernando Valley, viewing north (Woodland Hills, Canoga Park and Chatsworth in the distance.) “This fault system has not been considered in previous hazard assessments.”Christened the Puente Hills fault, the newly discovered fault zone runs in three broad segments for almost 25 miles under downtown Los Angeles, through Santa Fe Springs and into the Coyote Hills of northern Orange County. Like the 1987 Whittier Narrows Earthquake (M w 5.9), the Northridge earthquake was caused by the sudden rupture of a previously unknown, entirely subsurface, ‘blind’ thrust fault. âÀû"^¤%;³�œl¼x¹¢¢İ1„íŞIú°†�‡iâç K6~ºîûpÕÜ[‡„û‡ ÷Ÿ!ûû“~”°ZÂ>±Ç?VâÉ9Àû›ˆÕô˜¯×¬²IèÓ{i4
“It was so expensive to collect. Buildings crumbled in the 1994 Northridge earthquake, rated the most expensive in U.S. history. The impact of the improvements to building code became evident in the 1987 Whittier Quake, 1991 Sierra Madre Quake, 1992 Landers Quake, and 1994 Northridge Quake. Principal faults exposed at the surface (purple lines) and urbanized areas of southern California (gray shaded area) are shown for comparison. ‘We’re going to be more stubborn this time,’ he says.Devo cofounder Mark Mothersbaugh spent weeks in Cedars-Sinai hospital, hooked up to a ventilator, his mind wracked by violent hallucinations.L.A. Until now, many researchers had blamed the Oct. 1, 1987, temblor east of downtown on the Elysian Park system, which runs for 11 miles through the city.“Prior to now, there was a feeling there was a fault down there, but we could not, in effect, see it,” Henyey said. “This particular report is confirming the notion that those types of ground motions are feasible for directly under the city.”Researchers are still struggling to master the bookkeeping of plate tectonics, to learn how earthquakes, fault slippage and seismic energy all balance out in the L.A. Basin.Many of the best-known faults may never rupture again, while some potentially damaging faults continue to elude detection because they leave no traces at the surface.USC geologist James F. Dolan called the newest finding “an impressive achievement.”“It is incredibly important that we know where these active structures are because they are the ones that produce the future earthquakes,” Dolan said.Scientists have found a major active thrust fault under metropolitan Los Angeles that caused the magnitude 5.9 Whittier Narrows earthquake in 1987.Invisible at the surface, the newly mapped Puente Hills Fault structure is 25 miles long and 12.5 miles wide. County sheriff’s deputies fatally shot a man Monday afternoon in the Westmont neighborhood of South Los Angeles, the department said.
Previously secret oil company data reveal a major active fault system under metropolitan Los Angeles that most likely caused the magnitude 5.9 Whittier Narrows earthquake in 1987, researchers said Thursday.This buried fracture may be capable of larger and even more damaging earthquakes than the 1994 Northridge quake, according to the research, published today in Science.The discovery is the latest in a series of recent findings about regional seismic hazards that have some experts questioning whether earthquake engineering safety standards and building codes in Southern California should be strengthened.The newly found fault “is clearly a source of major earthquakes and likely could produce much damage to the L.A. area,” said Harvard University geophysicist John H. Shaw, who conducted the study with Peter M. Shearer at the Scripps Institution of Oceanography in La Jolla.
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The new research gives the first concrete form to their fears by producing direct images of an active blind-thrust fault concealed beneath the asphalt and steel of urban Los Angeles, according to leading authorities on the geology of the basin.Even so, the discovery does not seriously increase the overall earthquake risk facing the Los Angeles region, they said, because tectonic energy--and the attendant risk of major earthquakes--is building up in the basin at a relatively constant rate.“Finding a new fault doesn’t mean that the overall hazard has changed, but that we know more about where an earthquake might occur and how large it is likely to be,” said U.S. Geological Survey seismologist David Ward.