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Geoscientists Use Numerical Model to Understand Forces Behind Earthquakes

Researchers used their model to help explain the stresses that act on Earth's tectonic plates. Those stresses result in earthquakes not only at the boundaries between tectonic plates, where most earthquakes occur, but also in the plate interiors, where the forces are less understood. (Credit: © Anton Balazh / Fotolia)

Stony Brook University researchers have devised a numerical model to help explain the linkage between earthquakes and the powerful forces that cause them, according to a research paper scheduled to be published in the journal Science on Feb. 17. Their findings hold implications for long-term forecasting of earthquakes.

William E. Holt, Ph.D., a professor in the Geosciences Department at Stony Brook University, and Attreyee Ghosh, Ph.D., a post doctoral associate, used their model to help explain the stresses that act on Earth’s tectonic plates. Those stresses result in earthquakes not only at the boundaries between tectonic plates, where most earthquakes occur, but also in the plate interiors, where the forces are less understood, according to their paper, “Plate Motions and Stresses from Global Dynamic Models.”

“If you take into account the effects of topography and all density variations within the plates — the Earth’s crust varies in thickness depending on where you are — if you take all that into account, together with the mantle convection system, you can do a good job explaining what is going on at the surface,” said Dr. Holt.

Their research focused on the system of plates that float on Earth’s fluid-like mantle, which acts as a convection system on geologic time scales, carrying them and the continents that rest upon them. These plates bump and grind past one another, diverge from one another, or collide or sink (subduct) along the plate boundary zones of the world. Collisions between the continents have produced spectacular mountain ranges and powerful earthquakes. But the constant stress to which the plates are subjected also results in earthquakes within the interior of those plates.

“Predicting plate motions correctly, along with stresses within the plates, has been a challenge for global dynamic models,” the researchers wrote. “Accurate predictions of these is vitally important for understanding the forces responsible for the movement of plates, mountain building, rifting of continents, and strain accumulation released in earthquakes.”

Data for their global computer model came from Global Positioning System (GPS) measurements, which track the movements of Earth’s crust within the deforming plate boundary zones; measurements on the orientation of Earth’s stress field gleaned from earthquake faults; and a network of global seismometers that provided a picture of Earth’s interior density variations. They compared output from their model with these measurements from Earth’s surface.

“These observations — GPS, faults — allow one to test the completeness of the model,” Dr. Holt said.

Drs. Ghosh and Holt found that plate tectonics is an integrated system, driven by density variations found between the surface of Earth all the way to Earth’s core-mantle boundary. A surprising find was the variation in influence between relatively shallow features (topography and crustal thickness variations) and deeper large-scale mantle flow patterns that assist and, in some places, resist plate motions. Ghosh and Holt also found that it is the large-scale mantle flow patterns, set up by the long history of sinking plates, that are important for influencing the stresses within, and motions of, the plates.

Topography also has a major influence on the plate tectonic system, the researchers found. That result suggests a powerful feedback between the forces that make the topography and the ‘push-back’ on the system exerted by the topography, they explained.

While their model cannot accurately predict when and where earthquakes will occur in the short-term, “it can help at better understanding or forecasting earthquakes over longer time spans,” Dr. Holt said. “Nobody can yet predict, but ultimately given a better understanding of the forces within the system, one can develop better forecast models.”

…(Science Daily)

February 27, 2012 Posted by | Science, Seismic | , , , , , | Leave a comment

Riyadh Sandstorm turns Day into Night

Motorists flash hazard lights to alert other drivers as traffic slows down in the capital during a sandstorm on Saturday afternoon. (AN photo)

Riyadh: A heavy sandstorm hit the Saudi capital yesterday, making the city totally dark after 4 p.m. as it swept through neighboring areas.

“Darkness enveloped the main arteries of the capital city such as Qassim, King Fahd, Khurais and Makkah roads because of the storm which started at about 12 noon,” said Benny M. Quiambao, a Filipino building contractor. Drivers slowed down and switched on their hazard lights as visibility dropped to zero, he said.

Earlier, the Presidency of Meteorology and Environment (PME) had warned that a sandstorm was approaching Riyadh with a one-meter horizontal visibility.

Director General of Health Affairs in Riyadh Dr. Adnan bin Sulaiman Al-Abdulkarim, announced at 3 p.m. yesterday that hospitals under the Ministry of Health were ready to admit dust-hit patients.

Other regions like Qassim and Hail had also been affected. “The sandstorm started at 8:30 in the morning in Qassim, followed by rains at about 12:15 in the afternoon. It stopped at about 3:30 p.m.,” said Arnold G. Pineda, a community leader in Buraidah. He added that by 5:30 p.m. the rains had stopped but the skies remained cloudy.

Edmund Nieto, who works for the STC in Hail, said there was no storm in the area. “However, there were intermittent rains and the skies were cloudy the whole day,” he said.

Murad Al-Sagaf, manufacturing director at a Saudi firm in Buraidah, added that in the northern region, it was cloudy with intermittent rains.

…(Arab News)

February 27, 2012 Posted by | Weather | , , , , | Leave a comment

Strongest Earthquake in 15 Years Hits SE France

The earth shook in Crévoux, 16 km northeast of Barceloneta, tonight at 11:37 p.m. accurate, according to the website of Atomic Energy Commission (CEA).

The earthquake measuring 4.9 on the Richter scale was felt in the Var, Alpes-Maritimes and even Marseille where many people have felt the tremor for 3 to 4 seconds.

Not since 1997 to find an equivalent amplitude in this mountainous region of the Hautes-Alpes.

…(La Provence)

February 27, 2012 Posted by | Seismic | , , , , , | Leave a comment

5.9 Magnitude Earthquake Rattles Taiwan

A shallow 5.9-magnitude earthquake sent people fleeing onto the streets in Taiwan’s second-largest city of Kaohsiung and led to temporary halting of rail services. No casualties were reported yesterday.

The quake struck 57 kilometers east of the southern city at 10.34am at a depth of just four kilometers, the US Geological Survey said. The Hong Kong Observatory measured the quake at a magnitude of six, while Taiwan’s Seismology Centre put it at 6.1. The National Fire Agency said there were no casualties or major material damage.

“A few Kaohsiung residents sought safety in the streets for a short while, but it wasn’t many,” a police officer said.

A spokesman for the center said it is relatively rare for a quake of such magnitude to hit the Kaohsiung area. “While the quake was strong, it didn’t last long,” Chen Jung-yu said.

“Even in some towns near the epicenter, buildings swayed for no more than seven seconds. That explained why it did not inflict damages.”

A high-speed railway linking Kaohsiung with Taipei in the north resumed about 90 minutes after the quake prompted services to be suspended. The greater metropolitan area of Kaohsiung has a population of nearly three million.

Taiwan is regularly hit by quakes as it lies near the junction of two tectonic plates.

In September 1999, a 7.6-magnitude tremor killed 2,400 people in the deadliest natural disaster in the island’s recent history.

…(The Standard)

February 27, 2012 Posted by | Seismic | , , , , , | Leave a comment

6.7 Magnitude EQ – SW Siberia, Russia

At approximately 06:17:19 UTC on Sunday, February 26th, a 6.7 magnitude earthquake based on land struck at a depth of 11.7 km (7.3 miles) in the region of SW Siberia, Russia, 101 km (62 miles) E of Kyzyl, Russia. Coords: 51.731°N, 95.921°E …(USGS)

The 6.8 magnitude earthquake that struck the Tyva republic in Russia’s East Siberia on Sunday will trigger a new series of earthquakes in the region, a Russian scientist said.

“Judging from the data received from our stations, this is not the continuation of the Tyva earthquake that occurred in late 2011 with its epicenter at the Academician Obruchev Ridge but signals a new series of earthquakes,” said Viktor Seleznyov, director of the Geophysical Institute at the Siberian branch of the Russian Academy of Sciences.

The earthquake, the second powerful tremor in East Siberia in the past two months, had its epicenter located 107 km (66 miles) east of the city of Kyzyl near the border with Mongolia, at a depth of 15 km. The earthquake struck at 10:20 a.m. Moscow time (06:20 GMT) with a magnitude of 6 to 7 points in the epicenter.

The earthquake caused no casualties or damage, according to preliminary data reported by the Russian Emergencies Ministry.

The previous earthquake with a 6.7 magnitude occurred in December 2011 in the Kaa-Khemsky district of Tyva, some 100 km east of the city of Kyzyl, at a depth of 10 km. The tremor caused no destruction or casualties.

The next earthquake was expected to strike closer to Lake Baikal. Normally, a fault that becomes active in one area causes a series of decreasing tremors by their magnitude, he said.

“In this case, it is most likely that some neighboring fault became active near the previous one. This means that Tyva will now be rattled by two series of earthquakes simultaneously,” he said.

…(Ria)

February 27, 2012 Posted by | Seismic | , , , , , | Leave a comment

Mystery Virus Kills Thousands of Lambs

The worst affected counties are Norfolk, Suffolk, East Sussex and Kent, but the virus has spread all along the south coast to Cornwall Photo: GETTY

Thousands of lambs have been killed by a new virus that is threatening the survival of many British farms.

The Schmallenberg virus causes lambs to be born dead or with serious deformities such as fused limbs and twisted necks, which mean they cannot survive.

Scientists are urgently trying to find out how the disease, which also affects cattle, spreads and how to fight it, as the number of farms affected increases by the day.

So far, 74 farms across southern and eastern England have been hit by the virus, which arrived in this country in January.

A thousand farms in Europe have reported cases since the first signs of the virus were seen in the German town of Schmallenberg last summer.

The National Farmers Union has called it a potential “catastrophe” and warned farmers to be vigilant. “This is a ticking time bomb,” said Alastair Mackintosh, of the NFU. “We don’t yet know the extent of the disease. We only find out the damage when sheep and cows give birth, and by then it’s too late.”

It is unclear exactly how the disease arrived in Britain, but the leading theory is that midges carried the virus across the Channel or North Sea in the autumn. However, scientists cannot yet rule out transmission of the disease from animal to animal.

Infected ewes do not show any symptoms of the virus until they give birth, with horrific results. Farmers have described delivering the deformed and stillborn animals as heartbreaking.

The lambing season has only just begun, which means that the full impact of the disease will not be felt until the weather warms up and millions more animals are born.

On the Continent, some farms have lost half of their lambs. So far the worst hit in Britain have lost 20 per cent, according to the Department for Environment, Food and Rural Affairs (Defra).

…(Telegraph)

February 27, 2012 Posted by | Animals, Health Warning | , , , | Leave a comment

Unexpected Display of Aurora Stuns Observers

QUIET SUN: With no sunspots actively flaring, the sun’s output has flatlined again.

NOAA forecasters put the chance of an M-class flare during the next 24 hours at no more than 1%. Solar activity should remain low.

AURORA WHIRLPOOL: On Feb. 14-15, Arctic skies erupted with an unexpected display of auroras that veteran observers said was among the best in months. At the height of the event, a US Defense Meteorological Program satellite photographed a whirlpool of Northern Lights over the Bering Sea:

“A number of images from the DMSP F18 satellite captured the dramatic auroral event of the last couple nights,” says analyst Paul McCrone, who processed the data at the US Navy’s Fleet Numerical Meteorology and Oceanography Center in Monterey, CA.

The reason for the outburst is still not completely clear. It started on Feb. 14th when a magnetic disturbance rippled around the north pole. No CME was obvious in local solar wind data at the time; the disturbance just happened. Once begun, the display was amplified by the actions of the interplanetary magnetic field (IMF). The IMF near Earth tipped south, opening a crack in our planet’s magnetic defenses. Solar wind poured in and fueled the auroras.

more images: from Göran Strand of Östersund, Sweden; from Heidi Pinkerton of Birch Lake, Babbitt, Minnesota; from Roger Schneider of Tromso, Norway; from Hanneke Luijting of Tromsø, Norway; from Peter Rosén of Abisko NP, Sweden; from Jesper Grønne of Silkeborg Denmark

…(Space Weather)

February 17, 2012 Posted by | Solar, Space | , , , , , , | 1 Comment

Volcanologists Monitor Swarm of New Tremors at El Hierro

The submarine eruption south of El Hierro Island could be in a process of change: While visible activity on the sea surface above the vent, as well as harmonic tremor signal (thought to be more or less proportional to erupting magma flux) have nearly ceased, the number of earthquakes under the island has increased sharply since yesterday.

On 15 February, more than 20 quakes were measured. Most of the earthquakes were very small, well below magnitude 2, and were clustered beneath the NW and SW sectors of the island at depths of around 10 km. There is no conclusive interpretation of this measurement.

A possible (and usually assumed) scenario is that rising new magma from the mantle reservoir is creating new intrusions and rupturing rock to create pathways in the crust under El Hierro, not using the same paths as until now. That would explain why less magma is currently being erupted at the current vent(s). In that scenario, the eruption will continue, perhaps even from a different vent, and an increase in magma output is going to be expected any time soon. However, this is speculation.

The earthquakes could as well be related to some other (known or unknown) process, e.g. gravity-induced adjustments that respond to pressure changes and occur within previously ruptured areas of the crust beneath the island.

The next days or weeks will show what happens next.

…(Volcano Discovery)

February 17, 2012 Posted by | Science, Volcanic | , , , , , , | 1 Comment

6.0 Magnitude EQ – Off the Coast of Oregon

A strong 6.0 magnitude earthquake struck on Tuesday roughly 160 miles off the coast of Oregon, the U.S. Geological Survey said. This earthquake comes one day after a 5.6 magnitude quake rattled Northern California near the Pacific Coast.

A 4.2 magnitude earthquake struck off the coast of Vancouver Island toward the northern edge of the Juan de Fuca plate earlier in the day on February 14 at 2:54 p.m. local time.

With all quakes, being prepared and having a plan is the only true defense as a quake can happen at any time.

At approximately 03:31:20 UTC on Wednesday, February 15th, the 6.0 magnitude earthquake based on water struck at a depth of 10.0 km (6.2 miles) off the coast of Oregon, 256 km (159 miles) W of Coos Bay, Oregon. Coords: 43.536°N, 127.381°W

…(USGS)

The 1700 Cascadia earthquake was a magnitude 8.7 to 9.2 megathrust earthquake that occurred in the Cascadia subduction zone on January 26, 1700. The earthquake involved the Juan de Fuca Plate underlying the Pacific Ocean, from mid-Vancouver Island in British Columbia, Canada, south along the Pacific Northwest coast as far as northern California, USA.

The length of the fault rupture was about 1,000 kilometers (620 miles) with an average slip of 20 meters (22 yards).

The earthquake caused a tsunami that struck the coast of Japan, and may also be linked to the Bonneville Slide.

February 15, 2012 Posted by | Seismic | , , , , , | 1 Comment

6.5 Magnitude EQ – Solomon Islands, 6.0 EQ – Near the East Coast of Honshu

At approximately 08:19:58 UTC on Tuesday, February 14th, a 6.5 magnitude earthquake based on water struck at a depth of 54.7 km (34.0 miles) in the region of the Solomon Islands, 72 km (44 miles) W of Kira Kira, Solomon Islands. Coords: 10.387°S, 161.262°E

…(USGS)

As well, a 6.0 Magnitude EQ struck near the East Coast of Honshu at 06:21:58, 93 km (57 miles) ESE of Mito, Honshu, Japan, at a depth of 10km (6.2 miles)… (USGS)

A powerful earthquake rocked eastern Japan Tuesday, but no tsunami warning was issued and no damage was reported at the crippled Fukushima nuclear plant.

The US Geological Survey said the 6.0 magnitude quake, with an epicentre 10 kilometres (six miles) deep, was centred 166 kilometres east-northeast of Tokyo, where correspondents said buildings swayed.

Japan’s meteorological agency also located the quake off the coast of Ibaraki prefecture, south of the stricken plant. A very small change of tidal level was forecast but was not expected to cause any damage. Nuclear plant operator Tokyo Electric Power Co. (TEPCO) said the stricken Fukushima Daiichi plant remained stable.

…(Vancouver Sun)

February 14, 2012 Posted by | Seismic | , , , , , , , , | Leave a comment

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