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earthquakes

Lead-up to Icelandic earthquakes seen in groundwater chemistry

Scientists tracking groundwater in Iceland have reported that significant shifts in the water’s chemistry occurred months prior to earthquakes in 2012 and 2013. It’s far too early to apply the findings to earthquake hazard assessment, researchers say, but the results suggest that precursory groundwater changes may also herald earthquakes elsewhere and point toward a potential means of future seismic monitoring.

31 Dec 2014

Benchmarks: December 26, 2004: Indian Ocean tsunami strikes

On Dec. 26, 2004, a magnitude-9.2 earthquake ruptured the seafloor off Indonesia, sending the most destructive tsunami in recorded history across the Indian Ocean. A wall of water and debris slammed the shores of South Asia; some witnesses described it as sounding like a freight train. Tourists and locals alike scrambled to safety inland and atop tall hotels, recording videos of the surging water that inundated their communities. Many were unable to reach higher ground.

26 Dec 2014

Snow triggers quakes on Mount Rainier

A new study indicates that more than 150,000 low-frequency earthquakes that occurred on Mount Rainier over the past decade were caused by snowfall that triggered stick-slip sliding of glaciers.

25 Dec 2014

Hazard lingers after South Napa earthquake

The magnitude-6 earthquake that shook buildings and rattled wineries in California’s Napa Valley on Aug. 24, 2014, continues to affect homes in at least one neighborhood in the city of Napa more than three months later. The quake’s epicenter was about 6 kilometers south of the city, but post-quake movement, or afterslip, along the principal fault line to the north of the epicenter is ongoing, according to a fast-track report prepared by the U.S. Geological Survey (USGS) for the Federal Emergency Management Agency. Scientists involved in producing the 51-page report — released to the public on Tuesday — discussed it at a press conference at the annual meeting of the American Geophysical Union in San Francisco.

17 Dec 2014

Inland earthquake triggers distant tsunami

On Sept. 24, 2013, a magnitude-7.7 earthquake struck southern Pakistan, killing more than 800 people. The quake made global headlines in part due to the birth of a small island it triggered just off the coast — a mound of mud dubbed Quake Island that has since washed away. A new study has found evidence of another curious event linked to the quake: a small tsunami that appears to have been remotely triggered by a submarine landslide far from the earthquake’s inland epicenter.

26 Nov 2014

Seismic friction causes fault iridescence

Although iridescent spots on rocks in Utah’s Wasatch Fault Zone were first recognized two decades ago, scientists haven’t understood their origin, until now. New research shows that the iridescence appears on fault surfaces subjected to flash heating from friction and that the spots can provide clues to ancient seismic events. 

11 Nov 2014

Russian earthquake ruptures superfast and deep

A “superfast” magnitude-6.7 earthquake was detected off the coast of Kamchatka, Russia, in May. The earthquake, called a “supershear” quake, is one of a handful of superfast earthquakes noted by researchers over the years, but this is the first identified at such great depth.

24 Oct 2014

We're all living in the global aftershock zone

Can a large earthquake trigger another quake hundreds or even thousands of kilometers away? The answer, scientists say, appears to be yes, but when it happens is far from predictable. How does such dynamic triggering affect global earthquake hazards? Perhaps the whole world should be considered an aftershock zone.

19 Oct 2014

Remote triggering of ice quakes

On Feb. 27, 2010, a magnitude-8.8 earthquake struck the subduction zone off the coast of Chile. The resulting Rayleigh surface waves rippled around the world, triggering small earthquakes in many different tectonic settings, including Antarctica. As the surface waves moved across the white continent, a third of Antarctic seismic stations reported shaking coming from so-called “ice quakes.”

19 Oct 2014

Triggered tremor along the San Andreas Fault

The San Andreas Fault (SAF) in California is one of the most active in the U.S., but the 1,300-kilometer-long strike-slip fault seems to only be susceptible to small-scale dynamic triggering. After the magnitude-9 Tohoku quake in Japan in 2011, the SAF experienced an elevated incidence of tremor up and down its length. The tiny tremors were recorded at depths between 16 and 30 kilometers, below the fault’s seismogenic zone.

19 Oct 2014

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