Taxonomy term

seismicity

Benchmarks: November 18, 1929: Turbidity currents snap trans-Atlantic cables

On the evening of Monday, Nov. 18, 1929, a magnitude-7.2 earthquake ruptured off the coast of Newfoundland, Canada. Those living on the Burin Peninsula, a foot of land that reaches into the Atlantic Ocean, reportedly felt five minutes of shaking — a confusing sensation, since no one in the area had experienced an earthquake before. “Suddenly this roar — this loud banging — [occurred] and the kettle and the plates started to dance,” Gus Etchegary, a resident of the Burin Peninsula who had experienced the quake, described in a documentary video produced by The Newfoundland and Labrador Heritage Website.

18 Nov 2017

Eavesdropping on Old Faithful

The Old Faithful geyser in Yellowstone National Park has erupted predictably within a 10-minute window every hour for more than 150 years, but the inner workings that power its regular 30-meter-high eruptive plumes are largely still a mystery. Recent monitoring of the gusher is revealing new secrets about its plumbing system, which may help the National Park Service plan for future infrastructure expansions around the popular attraction.

28 Jul 2017

Initial earthquake behavior does not predict outcome

Can seismologists tell from the first few seconds of recorded seismic data how big an earthquake is going to be, or does it take longer and require data that come in after a quake rupture has progressed along the fault? The answer to this question underpins the usefulness of earthquake early warning systems and has perplexed scientists for decades. In a new study, researchers looking at near-source seismic recordings from shallow crustal earthquakes have found that, within the first few seconds of rupture, large and small earthquakes appear indistinguishable from one another, hinting that initial rupture behavior may be universal among variously sized events.

26 Jan 2017

Lack of afterslip in Nepal hints at mounting tensions

On April 25, 2015, a magnitude-7.8 earthquake struck Nepal, northwest of Kathmandu, damaging much of the capital city, flattening surrounding villages and killing more than 8,000 people. The quake’s hypocenter was relatively shallow, only 15 kilometers below ground on a fault that’s part of the Main Himalayan Thrust. Yet the displacement didn’t rupture all the way to the surface, indicating that only part of the fault slipped. Now, in a new study looking at how the fault continued to move following the 2015 event, researchers have found that the shallower section of the fault is likely still locked — and potentially loaded for another earthquake.

02 Oct 2016

Nearly half of Americans in lower 48 at risk for potentially damaging quake shaking

An estimated 143 million Americans in the conterminous 48 states, or about 46 percent of the population, live in areas susceptible to potentially damaging ground shaking from natural earthquakes, according to a new study by U.S. Geological Survey (USGS) scientists published in the journal Earthquake Spectra. (The study did not assess hazards associated with human-induced quakes.)
 
16 Dec 2015

Balanced boulders in earthquake country highlight interconnected faults

Precariously balanced boulders look like bizarre accidents in any landscape, but when they’re found in regions famous for frequent earthquakes, such gravity-defying formations are even more improbable. Scientists have long wondered about an odd collection of dozens of balanced boulders in the San Bernardino Mountains that seemingly should have been toppled centuries ago by the earthquakes that regularly shake Southern California. Even stranger, these car- to house-sized granite boulders are located within 10 kilometers of the active San Andreas and San Jacinto faults. Now, new detective work on 36 of the boulders is giving scientists clues about the connections between these faults. 
 
14 Dec 2015

Ice sheet has had lasting effect on European earthquakes

“Modern Germany is not known for its earthquakes,” says Christian Brandes, a geoscientist at the University of Hannover in Germany. The country, after all, is in the middle of a tectonic plate, he says, away from any plate boundaries or other features that would cause tectonic strain to build up in underground faults. 
 
10 Nov 2015

Campi Flegrei makes its own concrete caprock

In the 1980s, Tiziana Vanorio was a teenager living in the Italian port city of Pozzuoli west of Naples when the  Campi Flegrei volcanic complex that underlies the town and its harbor began to stir. Between 1982 and 1984, the caldera swelled more than 2 meters — the most rapid volcanic uplift ever measured anywhere. The rising seafloor shallowed Pozzuoli’s harbor so that ships could no longer enter. The uplift was followed by a magnitude-4 earthquake and thousands of microquakes that prompted the evacuation of 40,000 residents. Thereafter, the seismicity waned and the residents returned home, but geologists were left with a puzzle: How did the caldera withstand such extreme strain and deformation for so long without rupturing? 
 
16 Oct 2015

Source of Red Sea's mysterious cannon earthquakes revealed

For decades, people living along Egypt’s Red Sea coast have reported hearing loud blasts accompanying the small earthquakes that regularly jolt the Abu Dabbab region. And there is evidence the sounds have been occurring for much longer: Abu Dabbab means “the Father of Knock” in Arabic, hinting at a tectonic mystery at least as ancient as the name of the long-inhabited coastal region. Now, scientists are offering a novel explanation for the uniquely noisy seismic events, and their discovery is revealing new information about the underlying structure of the Red Sea region. 
 
08 Oct 2015

Injection experiment offers new view of fluid-filled faults

Scientists have known since the late 1960s that injecting fluids underground can cause earthquakes if those fluids find their way into slip-prone fault zones. Evidence of fluid-induced quakes has continued mounting in recent years with observations of abnormally high levels of seismicity in the central U.S., coincident with increased injections of wastewater into the ground — mostly related to oil- and gas-mining operations. But understanding the inner workings of fluid-filled faults is challenging because researchers have been limited by how close they can get to study them. Now, a new study is offering a glimpse into the future of induced-seismicity studies by monitoring fault motions on the spot and in real time.
 
19 Sep 2015

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