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earthquakes

Striped pyrites link earthquakes to gold deposition

Many of the world’s richest gold deposits are found in fault zones, where the precious metal is concentrated in quartz veins that cut through the surrounding rock. For several decades, scientists have suspected that earthquakes help form these deposits by releasing pressure and giving metals in mineral-rich hydrothermal fluids in the fault zone a chance to precipitate. But clear evidence for this so-called “fault-valve” process has been hard to come by. Now, researchers studying the geochemical makeup of tiny pyrite crystals from one well-known gold mine appear to have found some long-sought confirmation.

18 Jul 2014

People's earthquake reports influenced more by locomotion than location

In this era of high-tech seismic networks and GPS, scientists still rely on low-tech earthquake intensity scales, generated from public surveys like the U.S. Geological Survey’s (USGS) Did You Feel It? questionnaire, to characterize ground shaking in places with low instrument coverage. But how accurate are people’s perceptions of shaking? 

15 Jul 2014

San Andreas Fault shook Bay Area three times in a century

During the April 18, 1906, magnitude-7.9 earthquake near San Francisco, Calif., 470 kilometers of the San Andreas Fault ruptured between San Juan Bautista, south of San Francisco, and Point Arena, north of the city.

27 Jun 2014

Longmenshan fault zone in the spotlight after two major quakes in five years

In May 2008, a magnitude-7.9 earthquake struck near Wenchuan, China, killing more than 80,000 people in the country’s biggest quake since 1950. Then, in April 2013, the magnitude-6.6 Lushan earthquake hit just 90 kilometers to the south — also within China’s Longmenshan Fault Zone, which separates the Tibetan Plateau to the west from the Sichuan Basin to the east — and caused another 200 deaths. Now, scientists have found that a roughly 60-kilometer segment of the fault zone between the epicenters of the two big temblors could be the next to rupture, although no one knows when or how big it might be.

05 Jun 2014

Humans causing California's mountains to grow

Humankind has proven time and again that it can reshape mountains, or even tear them down. Now, it appears, we can make them rise as well. Geologists studying growth rates of the Sierra Nevada and of central California’s Coast Ranges have identified an anthropogenic contribution to the mountains’ uplift that they suggest is tied to the decades-long depletion of groundwater in the state’s Central Valley. What’s more, the researchers report in a new study published in Nature, the long-term water loss may be affecting how stress builds up on faults like the San Andreas.

14 May 2014

Faking quakes at full scale: Giant shake tables simulate earthquakes to make buildings safer

At a few select facilites around the world, engineers are able to shake full-size buildings to learn how to make them safer during earthquakes. Take a look at the massive shake tables that make it possible.

23 Apr 2014

Massive earthquake strikes Chile

A massive magnitude-8.2 earthquake struck off the coast of Chile about 95 kilometers north of Iquique on Tuesday night at 6:46 p.m. local time, according to the U.S. Geological Survey (USGS). Because the quake occurred underwater along a thrust fault in the subduction zone, a tsunami warning was issued for several cities along the Chilean coast and around the Pacific Basin. A 2.1-meter wave was reported in some Chilean cities. Preliminary reports indicate several deaths and some damage; power is out in many areas and landslides have also been recorded, according to news reports. So far, widespread destruction — which could easily accompany such a large quake — has thankfully not been reported.  The quake followed weeks of increased seismic activity, including dozens of earthquakes up to magnitude-6.7 that have struck since March 16. It is now clear these were foreshocks. 

01 Apr 2014

Seattle’s landslide risk greater than thought

Landslides have been part of Seattle’s history “from a time to which the memory of man runneth not back,” wrote famed city engineer Reginald Thomson in 1897. A new study shows that landslides will also play a central role long into the future. They will be “extensive and potentially devastating, causing direct losses and impeding recovery,” reported a team in Bulletin of the Seismological Society of America.

17 Mar 2014

Benchmarks: March 27, 1964: The Good Friday Alaska Earthquake and Tsunamis

During the Cold War, many Americans lived in fear of the day their town would be shaken by an atomic bomb blast. On Good Friday 1964, some Alaskans thought that day had come. Beginning at 5:36 p.m., intense ground shaking continued for almost five minutes as the most powerful earthquake ever recorded in North America struck 22.5 kilometers beneath Prince William Sound, where the Pacific Plate is subducting beneath the North American Plate. The shaking — felt over an area of more than 1.3 million square kilometers — was so severe and long-lived that some survivors later said they first thought the Soviet Union had dropped a nuclear bomb on Anchorage, 120 kilometers northwest of the epicenter.

27 Feb 2014

Hazards abroad: Sent home

On May 19, 2012, seismologist Roger Bilham of the University of Colorado at Boulder landed at the airport in Delhi, India, on his way to Bhutan. He debarked from the plane and was met by Indian customs officials, who declared he was on the “blacklist” and not allowed entry to India, despite having a valid visa. Two hours later, he was on a plane heading back to the U.S.

15 Dec 2013

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