Deadly Quakes Inside Continental Plates

Earthquake preparedness is high around seismically active tectonic plate boundaries, often saving many lives and structures. Quake death rates within continental interiors are higher than that of continental plate boundaries. Their faults are often very complex and slow-moving, sometimes taking thousands of years to rupture.

Knowledge of seismic risk is badly skewed in favor of earthquakes that occur on plate boundaries, such as the March 11 temblor that hit northeast Japan, rather than those that strike deep inland, a pair of scientists said on Sunday.

In commentary appearing in the journal Nature Geoscience, Philip England of Oxford University and James Jackson of Cambridge University say that in seismic terms, the 9.0-magnitude Sendai quake was "a remarkable story of resilience."

Good civic training and building construction meant that the death rate was "impressively low," they said. Around 25,000 people died, or 0.4 percent of those exposed to the event, and most of these died from the tsunami that followed.

The March 11 event occurred on a plate boundary, where the jigsaw of plates that float on Earth's crust jostle and grind and slide under each other.

England and Jackson say plate boundaries are relatively well-studied, but a far greater threat lurks in continental inland areas.

"Death rates in earthquakes within continental interiors have often exceeded five percent and can be as high as 30 percent," they warn.

According to their count, over the past 120 years, there have been around 130 quakes around the world where a thousand people or more have died.

Of these, about 100 have occurred in continental interiors, causing 1.4 million deaths, whereas earthquakes at plate boundaries have inflicted 800,000 deaths, roughly half of them by tsunamis.

Among the inland killers were those in Bam, Iran, which cost 30,000 lives in 2003; in Muzzafarabad, Pakistan, which led to 75,000 deaths in 2005; and the 2008 Wenchuan quake in China in 2008 in which 70,000 died.

The main reason for these high tolls is because inland quake zones are poorly mapped, the commentary says.

Their faults are often very complex and slow-moving, sometimes taking hundreds or even thousands of years to build up tension to the point where they rupture.

Jackson and England call for the study of inland faults to be given the same priority as boundary faults, starting with the 10 million square kilometers (3.86 million sq. miles) of the Alpine-Himalayan belt, which stretches from Italy, Greece and Turkey, across the Middle East, Iran and central Asia, to China.

"The severity of this threat is increasing rapidly as millions of people every year migrate into mega-cities in vulnerable locations, many of which were devastated by earthquakes in the past, when their populations were much smaller."

Iceland Volcano Erupts

Grimsvoetn volcano, located beneath Iceland's Vatnajoekull glacier, last erupted in 2004. Last year, Iceland's Eyjafjoell volcano, southwest of Grimsvoetn, shut down large swathes of European airspace for almost a month. For now, it is not known if Grimsvoetn will produce the troublesome fine ash Eyjafjoell generated.

The Grimsvoetn volcano under Iceland's largest glacier began erupting Saturday, the Icelandic Meteorological Office said, reporting a tall plume of smoke rising from the crater.

"An eruption at Grimsvoetn has started and there's an airplane on its way there now to investigate further," Haraldur Eirkisson of the office told AFP.

"There was a cloud rising up from Grimsvoetn around 1900 GMT and at just before 2000 GMT it had reached an altitude of 11 kilometers (6.8 miles)," he added.

Another meteorologist at the same office, Fridjon Magnusson, told AFP less than two hours later that the column of smoke had swelled to reach an altitude of 20 kilometers.

Grimsvoetn is Iceland's most active volcano, having erupted nine times between 1922 and 2004. It lies beneath the Vatnajoekull glacier in the southeast of the North Atlantic island nation.

The eruption in April last year of Iceland's Eyjafjoell volcano, southwest of Grimsvoetn, shut down large swathes of European airspace for almost a month amid fears the volcanic ash could wreak havoc on aircraft engines.

No two volcanic eruptions are the same, and it remained unclear late Saturday if the new eruption threatened to emit a similar kind of ash -- fine, with very sharp particles -- like the massive plume that burst from Eyjafjoell.

"The eruption has not yet spread very far, and is still looming over the Vatnajoekull glacier," Magnusson pointed out.

"These are just the first few hours of the eruption. We can't say yet whether this will have an effect on air traffic like Eyjafjoell," he added.

The problem with last year's eruption, which caused the planet's biggest air space shutdown since World War II, was according to the researchers that it happened under a glacier, bursting through 200-300 meters of ice.

It was the "interaction between the cold water and the hot magma that made the particles really tiny," and therefore especially dangerous to aircraft, Susan Stipp, a professor at the Nano-Science Centre at the University of Copenhagen, told AFP late last month.

"The (ash) particles were small so they went high and far. They were sharp, so they were a danger to airplane windows. It's like sand-blasting the airplane. And they were small and could melt at temperatures common in jet engines ... and could cause failure," she told AFP.

While Saturday's eruption had sent smoke high in the sky, Magnusson pointed out that there so far was only "heavy ash at the bottom of the bloom (that) has not reached high heights."

Bjarni Steinthorsson, a farmer who lives near the Vatnajoekull glacier, meanwhile told the Morgunbladid daily's website small amounts of ash had begun falling in the area and "the snow is getting darker."

He said that he expected more ash to fall overnight, although what happened would depend on the direction of the winds, which were currently almost still at the eruption site.

Iceland's State Road Authority meanwhile announced late Saturday it had temporarily closed a road near the glacier that is part of the national highway system.

Grimsvoetn is also located under a glacier, in an enormous, eight-kilometer (five-mile) diameter caldera -- a collapsed volcanic crater -- near the center of the Vatnajoekull icefield.

When it last erupted in November 2004, volcanic ash fell as far away as mainland Europe and caused minor disruptions in flights to and from Iceland.

Geologists had worried late last year the volcano was about to blow when they noticed a large river run caused by rapidly melting glacier ice.

Eruptions at Grimsvoetn traditionally result in massive flooding, although this has little impact since the surrounding areas are uninhabited.

Ash cloud from Icelandic volcano could hit Scotland by midday Tuesday

Ash from an erupting Icelandic volcano could reach northern Scotland by Tuesday and parts of Britain, France and Spain by Thursday or Friday if the eruption continues at the same rate, airlines were warned on Sunday. 

The warning is based on latest 5-day weather forecasts, but must be treated with caution because of the forecast period and the presence of different air currents from those prevailing at the time of last year's ash crisis, weather officials said.

European authorities said on Sunday no disruption was expected to European or transatlantic airspace over the next 24 hours from the eruption of Iceland's most active volcano on Saturday.

The warning comes nearly a year after one volcano erupted in Iceland and caused havoc for air passengers.

Grimsvoetn, Iceland’s most active volcano at the heart of its biggest glacier, began erupting late on Saturday, sending a plume of smoke and ash 12miles high.

So much ash was blasted into the sky that it blocked out the sun and covered nearby villages and farms.

Iceland volcano: Grimsvotn eruption hits flights

Iceland has closed its main international airport and cancelled domestic flights after its most active volcano, Grimsvotn, began erupting.

A plume of smoke has risen 20km (12 miles) into the sky from the volcano.
But Iceland's Meteorological Office says the eruption should not cause widespread disruption to air traffic.
Last year, ash clouds from another Icelandic volcano, Eyjafjallajokul, led to the closure of a large section of European airspace.
Governments feared that ash particles could cause aircraft engines to fail, and the closure caused chaos to air travellers.
Different ash Hjordis Gudmundsdottir, a spokeswoman for the Isavia civil aviation authority said: "We have closed the area until we know better what effect the ash will have."
The authority said Keflavik airport, the country's main hub, would remain shut for the rest of Sunday.
But officials say the eruption is unlikely to have the same impact as Eyjafjallajokul in 2010.
University of Iceland geophysicist Magnus Tumi Gudmundsson said this was Grimsvotn's largest eruption for 100 years, "much bigger and more intensive than Eyjafjallajokull".
He added: "There is a very large area in south-east Iceland where there is almost total darkness and heavy fall of ash. But it is not spreading nearly as much. The winds are not as strong as they were in Eyjafjallajokull."
He said this ash was coarser than last year's eruption, falling to the ground more quickly instead of floating long distances.
Europe's air traffic control organisation said on Sunday: "There is currently no impact on European or trans-Atlantic flights and the situation is expected to remain so for the next 24 hours.
"Aircraft operators are constantly being kept informed of the evolving situation."
Threat to engines Grimsvotn lies under the the largest glacier in Europe, Vatnajokull in south-east Iceland.
When it last erupted in 2004, transatlantic flights had to be re-routed south of Iceland, but no airports were closed.
Last year's outpouring of ash from Eyjafjallajokull led to the largest closure of European airspace since World War II.
About 10 million travellers were affected and some questioned whether the shutdown was an over-reaction.
However, a scientific study published last month said the safety concerns had been well founded.
Researchers from the University of Copenhagen and the University of Iceland said ash particles from the early part of the Eyjafjallajokull eruption were especially abrasive, posing a possible threat to aircraft engines.

Japan earthquake caused a displacement of about two meters

ScienceDaily (Apr. 8, 2011) — Researchers at the Institute of Geomatics -- Research Centre of the Polytechnic University of Catalonia (UPC) and the Government of Catalonia -- have estimated the ground deformation suffered in the area of Sendai, Japan, as a consequence of the earthquake of March 11, 2011 and its aftershocks. The estimate was derived from radar observations acquired by the Envisat satellite of the European Space Agency. According to this estimate, obtained over an area of approximately 300 x 100 km around the city of Sendai, the terrain has suffered a co-seismic deformation -- permanent deformation of Earth's surface -- associated with the earthquake of up to 1.69 m.

This value refers to the line connecting the satellite and the observed area, which is tilted about 41º from the vertical. The estimated value of 1.69 m is a deformation value relative to the observed area: the absolute deformation (i.e., calculated over an area not affected by the earthquake) is surely larger and cannot be estimated with this technique.

The minimum distance from the epicentre to the study area is 100 km approximately. At these distances the vast majority of earthquakes do not cause co-seismic deformation. However, in this case, there has been considerable deformation due to the exceptional magnitude of this earthquake.

The deformation can be seen in the map shown above, where the displacements are represented in a colour scale from black (no relative motion) to red (area of maximum deformation, which is the closest to the epicentre). There is relative deformation of 1.69 m from the area that appears black to the maximum area in red.

This study conducted by the Institute of Geomatics, and led by Dr. Michele Crosetto, head of the Remote Sensing Unit, is based on a well-known satellite-based microwave remote sensing technique called differential interferometry SAR (Synthetic Aperture Radar).

What does the observed deformation entail?

As mentioned above, the estimated 1.69 m deformation refers to the line connecting the satellite and the observed area. We know from other sources, such as measures of GPS (Global Positioning System), that the horizontal displacement has been of approximately 3 m eastwards, 0.5 m northwards and the vertical displacement varies between 0.5 and 1 m. The most important of these three components is probably the subsidence as it affects land elevation above sea level. Coastal areas are likely to be the most affected: in the worst case scenario, subsidence might lead to land loss. This is a phenomenon similar to what might result from climate change, although in this case, land would be lost as a result of sea-level rise.

How were the results derived?

SAR interferometry is a remote sensing technique used to monitor surface deformations. This technique, based on the analysis of SAR satellite data, has been used in various applications such as studying the dynamics of glaciers, earthquakes, volcanoes, mining, civil works, landslides and deformations due to exploitation of aquifers.

The results of this study were obtained using SAR data from the sensor ASAR mounted on the satellite Envisat of the European Space Agency. Specifically, in this case, two SAR images acquired before (19/02/2011) and after the seismic event (03/21/2011) have been used.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Universitat Politècnica de Catalunya.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Mississippi River Flooding

(Reuters) - Government engineers will blow up a third section of a Mississippi River levee on Thursday to manage flooding, as a wall of water roared down the nation's largest river system, threatening towns and cities all the way to the Gulf of Mexico.
The U.S. Army Corps of Engineers blew up a two-mile section of the Birds Point levee Monday night, inundating about 130,000 acres of Missouri farmland in a desperate attempt to ease flooding in towns in Illinois and Kentucky.
Water levels did recede but a second, smaller section was detonated Tuesday afternoon to allow water back into the river. A third and last blast was scheduled for Wednesday but was delayed until 1 p.m. on Thursday by "logistical difficulties," the Corps said in a statement on Wednesday night.
The Corps, which is responsible for the system of locks and dams along the Mississippi River, would then turn its attention to the growing threat further south.
"The entire system is experiencing flooding and we will continue our fight downstream," said Major Gen. Michael J. Walsh, president of the Mississippi River Commission, in a statement.
President Barack Obama on Wednesday declared parts of Kentucky, Mississippi and Tennessee as disaster areas due to flooding, freeing up federal aid to help those affected.
Arkansas closed a 15-mile stretch of westbound lanes of one of the busiest road arteries in the nation, Interstate 40, for the time ever due to flooding, according to the state's transportation department. More than 31,000 vehicles travel daily through the section of road closed, and 65 to 70 percent of those are trucks, said Glenn Bolick, Arkansas Transportation
Department spokesman.
Highway officials were diverting traffic onto rural roads but even some of these were flooded, they said.
Further downstream in Mississippi, some residents of the historic Civil War town of Vicksburg were moving to higher ground on Wednesday to avoid the rising flood waters.
"We are not going to stay here," said Vicksburg resident Harold Manner. "The families all around us are taking what they can and moving out of here, at least for now."
The levee system in Mississippi is holding for now but it has never been tested like this before, officials said.
"Compared to the Great Mississippi Flood of 1927 this flood is going to be a lot nastier," said Marty Pope, senior hydrologist for the National Weather Service in Jackson.
Mississippi Governor Haley Barbour has had sandbags delivered to his Yazoo City home to prevent it from flooding.
Large amounts of rain and melt from the winter snow has caused a chain reaction of flooding from Canada and the Dakotas through Illinois, Indiana, Missouri, Kentucky, Arkansas and Tennessee. It is expected to soon hit Mississippi and Louisiana at the mouth of the Mississippi River.