To scientists who study seismic hazards in the Caribbean, there was no surprise in the magnitude 7 earthquake that devastated the Haitian capital, Port-au-Prince, two weeks ago.
Except, perhaps, in where on the island of Hispaniola it occurred.
“If I had had to make a bet, I would have bet that the first earthquake would have taken place in the northern Dominican Republic, not Haiti,” said Eric Calais, a geophysicist at Purdue University who has conducted research in the area for years.
The fault that ruptured violently on Jan. 12 had been building up strain since the last major earthquake in Port-au-Prince, 240 years ago. Dr. Calais and others had warned in 2008 that a quake could occur along that segment, part of what is called the Enriquillo-Plantain Garden fault zone, although they could not predict when.
But about 100 miles to the northeast is a long segment of a similar fault, the Septentrional, that has not had a quake in 800 years. Researchers have estimated that a rupture along that segment — and again, they have no idea when one might occur — could result in a magnitude 7.5 quake that could cause severe damage in the Dominican Republic’s second-largest city, Santiago, and the surrounding Cibao Valley, together home to several million people.
“You can imagine the strain that has accumulated there,” said Paul Mann, a senior research scientist at the University of Texas, referring to the Septentrional fault. “It’s been going on for longer and accumulating faster. Therefore it’s going to produce a stronger earthquake.”
The recent quake on the Enriquillo fault and the forecast for the Septentrional are bleak reminders that the Caribbean is an active seismic zone, one with many hazards. Major earthquakes have regularly devastated the region’s cities, including the Jamaican capital, Kingston, which was destroyed twice in three centuries. An eruption of Mount Pelée killed 30,000 people in Martinique in the Lesser Antilles in 1902, and it and other volcanoes are currently active along that island arc on the Caribbean’s north and eastern reaches. Earthquakes and landslides along the Puerto Rico Trench, an undersea fault zone, have the potential to cause tsunamis.
The Haitian quake itself might have added to the risks, researchers say. Dr. Calais and colleagues and a team including Ross Stein of the United States Geological Survey in Menlo Park, Calif., have each calculated the stress changes on the Enriquillo fault that occurred when a 30-mile segment, centered in Léogâne about 18 miles west of Port-au-Prince, gave way this month. Although the results are preliminary, the work shows that stresses have increased just west of the segment and just east, within three miles of Port-au-Prince.
“This earthquake has increased the risk on other segments of that fault and perhaps on other faults as well,” Dr. Calais said. “The numbers are well within the range of stress changes that have triggered earthquakes on other faults.” But he said the quake probably did not increase the likelihood of a major tremor on the Septentrional fault.
The Haitian quake has produced a large number of aftershocks, about three times as many as quakes of similar magnitude in California and elsewhere, Dr. Stein said. But the intensity and frequency of those aftershocks have followed the patterns of other earthquakes, he said. Last Thursday, the geological survey issued a statement estimating that there was a 3 percent likelihood of a 7 magnitude aftershock in the next 30 days, and a 25 percent chance of one of magnitude 6. (On Wednesday, the area experienced a strong aftershock that was initially rated at 6.1 but was revised to 5.8.)
Of some concern, researchers said, was that none of the aftershocks have occurred in the area of increased stress nearer to Port-au-Prince, where ordinarily some might have been expected.
“One possibility is that these are simply calculations, and they may be wrong,” Dr. Stein said. “The other possibility is, O.K., this fault is fundamentally locked in some fashion, on pretty much all scales, and might be capable of popping off something large.”
In its statement, the geological survey cautioned that near the capital, “the fault still stores sufficient strain to be released as a large, damaging earthquake during the lifetime of structures built during the reconstruction effort.”
The region’s seismic activity is due to the movement of the Caribbean tectonic plate, which can be likened to a finger pushing its way against two larger plates, the North American and South American. Along the boundaries, the relative eastward movement of the Caribbean plate, at the rate of less than an inch a year, creates strike-slip faults, shallow fissures whose sides slide in relation to one another in an earthquake.
On the island of Hispaniola, which comprises the Dominican Republic and Haiti, the Caribbean-North American boundary stresses are expressed in numerous strike-slip faults, including the Enriquillo and Septentrional, which are relatively long and roughly parallel.
“It’s a bit unusual to have two parallel faults like that,” said Uri S. ten Brink, a geophysicist with the geological survey in Woods Hole, Mass. “It may simply be that for some reason there was already a weakened area further south.”
Dr. ten Brink’s main area of research is the Puerto Rico Trench, north of Puerto Rico and the United States Virgin Islands. This is a subduction zone — where the North American plate is sliding under the Caribbean, creating the potential for earthquakes and undersea landslides that can set off tsunamis.
“We’re trying to see if it’s a similar situation to the Sumatra fault,” Dr. ten Brink said, referring to the Indonesian subduction zone where a large earthquake in December 2004 created a tsunami that killed a quarter of a million people. Scientists have not yet found evidence of large subduction earthquakes on the Puerto Rican Trench, he said, “but that’s the $64,000 question.”To scientists who study seismic hazards in the Caribbean, there was no surprise in the... more
There have been numerous big and small earthquakes till date but the biggest earthquakes of all times had been recorded in the tape with an intensity of 9.5 on the Richter scale. In US, there has been a consistent record of earthquakes in history varying in dimension and chronology of earthquakes. Earthquakes in the US have contributed largely towards the record of earthquakes that has been listed so far globally. Here is the biggest earthquakes recorded.
Not only do many geological discoveries contribute to a better understanding of everyday life, but the past, present, and possible future of the planet itself.
Read More :http://constructionmanagementdegree.org/?page_id=421Not only do many geological discoveries contribute to a better understanding of... more
More than 20,000 people have evacuated homes in the Philippines after lava and ash flowed from one of the nation's most active volcanoes.
Soldiers and police directed the evacuation from around the foothills of Mayon volcano amid concerns that a big eruption could occur at any moment.
Philippine officials raised the alert level for Mayon on Monday.
Mayon, 330km (206 miles) south-east of the capital Manila, has erupted 48 times since records began.
The head of the disaster relief operations in the region, Cedric Daep, said the authorities aimed to evacuate nearly 50,000 people from villages within eight kilometres of the volcano by Thursday.
He said that after a series of ash puffs and ash explosions up to 1,000m high, a major explosion could not be ruled out.
After the most recent eruption of Mount Mayon in August 2006, huge deposits of volcanic ash were left on its slopes.
However, the volcano remains a popular tourist attraction and is famous for its perfect cone.
The Philippines is part of the so-called Pacific "Ring of Fire" that is known for its volcanic activity.
The Philippine Institute of Volcanology and Seismology lists 22 active volcanoes in the country.
In Bernhard Edmaier’s photographs, glowing rivers of lava and scarred volcanic plains share the stage with more obscure markers of tectonic activity—sulfurous crystals, eerily hued lakes, and pools of bubbling mud.In Bernhard Edmaier’s photographs, glowing rivers of lava and scarred volcanic... more
Some of the world’s baddest volcanoes, like Chile’s Chaitén volcano that erupted in 2008, are actually even worse than scientists previously thought. A study of Chaitén’s eruption revealed that locals only had 30 hours to to flee from first time they felt rumbling, not the weeks or months that it typically takes a volcano to go from tremors to eruption. That’s because Chaitén is a rhyolitic volcano; these volcanoes are largely fueled by a silica-based, very flow-resistant magma and they tend to build pressure over time before erupting violently [National Geographic News]. Thousands were able to escape before Chaitén’s blast, but scientists are warning that others living in the shadow of a rhyolitic volcano may not be so lucky.
The magma of the Chaitén volcano traveled up to 3 feet per second, according to the study published in Nature. It shot from a depth of more than five kilometres [3 miles] to the surface in about four hours…. The violent and unexpected nature of the blasts, together with their rarity, means the Chaiténeruption is the first rhyolite event to have been scientifically assessed in this way [ABC News]. In the U.S. there are large rhyolitic volcanoes in Wyoming, California, and New Mexico as well as in the Japanese islands and New Zealand’s Taupo Volcanic Zone. Scientists are saying that even though rhyolitic eruptions are rare, the study should serve as a warning call to step up monitoring of potentially active volcanoes.Some of the world’s baddest volcanoes, like Chile’s Chaitén volcano... more
BBC was inspired by the recent spate of natural disasters to befall Indonesia AGAIN, and interviewed my friend, Geologist Chris Rowan. In this interview, Chris explains to the BBC interviewer why scientists cannot predict earthquakes nor (to a lesser extent) tsunamis.BBC was inspired by the recent spate of natural disasters to befall Indonesia AGAIN,... more
An earthquake with a magnitude of 8.0 struck in the Samoan Islands region Tuesday.
The temblor generated three separate tsunami waves that are spreading, the largest of which measures 5.1 feet from sea level height, said Vindell Hsu, a geophysicist with the Pacific Tsunami Warning Center in Ewa Beach, Hawaii. Preliminary data had originally reported a larger tsunami.
A tsunami warning was in effect for American Samoa, Samoa, Cook Islands, Tonga and Fiji, among others in the South Pacific archipelago, according to a bulletin from the center.
A tsunami watch was issued for islands farther from the epicenter, including Hawaii and Papua New Guinea.
Officials were determining whether the tsunami could reach Hawaii, the center said. It was possible that a very decreased wave could reach Hawaii at 1:18 p.m. (7:18 ET), Hsu said.
The quake is not expected to generate a tsunami along the west coast of the United States or Canada, according to the West Coast and Alaska Tsunami Warning Center.
Further details were not immediately available.
There were no immediate reports of damage.
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The quake was recorded at 6:48 a.m. (1:28 p.m. ET) at a depth of about 7.4 miles (11.9 km), the USGS reported.
The airports in American Samoa and Samoa were closed in anticipation of a tsunami, but for now, "we haven't seen any big waves at the moment," Samoa airport employee Alefosao Mapulino said.An earthquake with a magnitude of 8.0 struck in the Samoan Islands region Tuesday.... more
There appears to be, to the surprise of planetary scientists, water, water everywhere on the Moon, but perhaps not many drops for future astronauts to drink.
Data from three spacecraft indicate the widespread presence of water or hydroxyl, a molecule consisting of one hydrogen atom and one oxygen atom as opposed to the two hydrogen and one oxygen atoms that make up a water molecule. The discoveries are being published Thursday on the Web site of the journal Science.
“It’s so startling because it’s so pervasive,” said Lawrence A. Taylor of the University of Tennessee, Knoxville, a co-author of one of the papers that analyzed data from a National Aeronautics and Space Administration instrument aboard India’s Chandrayaan-1 satellite. on the MoonThere appears to be, to the surprise of planetary scientists, water, water everywhere... more
At least 15 people were killed Wednesday when a powerful 7.0-magnitude earthquake struck off Indonesia's Java island, an official said.
"Fifteen people have been killed. Most of them were trapped under their houses," disaster management agency spokesman Priyadi Kardono told AFP.At least 15 people were killed Wednesday when a powerful 7.0-magnitude earthquake... more
Spot Cool Stuff has been thinking of cool spots lately. Big geologic spots, that is. Circles on the face of the planet of the sort that would make some one browsing around on Google Earth (or traveling in a spaceship) to stop and ask What the heck is that circular thing?
Here’s an overview (literally!) of seven of our favorite such spots:Spot Cool Stuff has been thinking of cool spots lately. Big geologic spots, that is.... more
When you visit a sandy beach, do you ever stop to think about those tiny grains under your feet, contemplate where they came from or what they might look like up close? Composed of the “remnants of volcanic explosions, eroded mountains, dead organisms, and even degraded man-made structures”, sand, when examined under a microscope, can reveal its true colors, shapes and textures.When you visit a sandy beach, do you ever stop to think about those tiny grains under... more
A massive earthquake last week has brought New Zealand closer to Australia, scientists say.
The 7.8 magnitude quake in the Tasman Sea has expanded New Zealand's South Island westwards by about 30cm (12in).
Seismologist Ken Gledhill, of GNS Science, said the shift demonstrated the huge force of the tremor.
But correspondents say that with more than 2,250km (1,400 miles) separating the countries, the narrowing will not exactly be visible.
Nor, as the New Zealand media have observed, is it likely to bring cheaper air fares.
The quake was powerful enough to generate a small tsunami with a wave of one metre (3ft) recorded on the west coast of New Zealand.
People in coastal areas were for a time advised to move to higher ground.
While the south-west of the South Island moved about 30cm towards Australia, the east coast moved only one centimetre westwards, Dr Gledhill said."Basically, New Zealand just got a little bit bigger is another way to think about it," he told AFP news agency.
Although it was New Zealand's biggest earthquake in 78 years, it caused only slight damage to buildings and property when it struck in the remote Fiordland region west of Invercargill last Thursday.
"For a very large earthquake, although it was very widely felt, there were very few areas that were severely shaken," Dr Gledhill said.
GNS Science is a research organisation run by the New Zealand government.
New Zealand frequently suffers earthquakes because it sits on the meeting point of the Australian and Pacific continental plates.A massive earthquake last week has brought New Zealand closer to Australia, scientists... more
A massive 7.8 magnitude earthquake last week has moved the south of New Zealand closer to Australia, scientists said Wednesday.
With the countries separated by the 2,250-kilometre-wide (1,400-mile-wide) Tasman Sea, the 30 centimetre (12 inch) closing of the gap in New Zealand's southwest won't make much difference.
But earthquake scientist Ken Gledhill of GNS Science said the shift illustrated the huge force of the tremor, the biggest in the world so far this year.
"Basically, New Zealand just got a little bit bigger is another way to think about it," he told AFP.
While the southwest of the South Island moved about 30 centimetres closer to Australia, the east coast of the island moved only one centimetre westwards, he said.
The biggest quake in New Zealand in 78 years caused only slight damage to buildings and property when it struck the remote southwest Fiordland region of the South Island last Thursday.
A small tsunami was generated by the earthquake, with a tide gauge on the West Coast of New Zealand recording a wave of one metre.
"For a very large earthquake, although it was very widely felt, there were very few areas that were severely shaken," Gledhill said.
Aerial inspection of the forested fiords near the quake's epicentre showed few land slips or other signs of damage.
This was partly because the type of rupture at the boundaries of the Australian and Pacific plates meant the energy from the quake was largely directed westwards towards the sea rather than inland towards the nearest towns.
The type of quake, known as a subduction thrust rupture, also meant the quake produced lower frequency shaking, felt as a rolling motion, rather than sharp jolts which would have caused more damage.
New Zealand frequently suffers earthquakes because it marks the meeting point of the Australian and Pacific continental plates.
Gledhill said the latest quake may have brought forward a major quake on the offshore section of the Alpine fault, off the coast of Fiordland in the Tasman Sea.
"There could easily be another large earthquake in another part of that region. We can't predict that obviously."A massive 7.8 magnitude earthquake last week has moved the south of New Zealand closer... more
Venus Express has charted the first map of Venus's southern hemisphere at infrared wavelengths. The new map hints that our neighbouring world may once have been more Earth-like, with both, a plate tectonics system and an ocean of water.
The map comprises over a thousand individual images, recorded between May 2006 and December 2007. Because Venus is covered in clouds, normal cameras cannot see the surface, but Venus Express used a particular infrared wavelength that can see through them.
Although radar systems have been used in the past to provide high-resolution maps of Venus's surface, Venus Express is the first orbiting spacecraft to produce a map that hints at the chemical composition of the rocks. The new data is consistent with suspicions that the highland plateaus of Venus are ancient continents, once surrounded by ocean and produced by past volcanic activity.
"This is not proof, but it is consistent. All we can really say at the moment is that the plateau rocks look different from elsewhere," says Nils Müller at the Joint Planetary Interior Physics Research Group of the University Münster and DLR Berlin, who headed the mapping efforts.
The rocks look different because of the amount of infrared light they radiate into space, similar to the way a brick wall heats up during the day and gives off its heat at night. Besides, different surfaces radiate different amounts of heat at infrared wavelengths due to a material characteristic known as emissivity, which varies in different materials. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument captured this infrared radiation during Venus's night-time orbits around the planet's southern hemisphere.
The eight Russian landers of the 1970s and 1980s touched down away from the highlands and found only basalt-like rock beneath their landing pads. The new map shows that the rocks on the Phoebe and Alpha Regio plateaus are lighter in colour and look old compared to the majority of the planet. On Earth, such light-coloured rocks are usually granite and form continents.
Granite is formed when ancient rocks, made of basalt, are driven down into the planet by shifting continents, a process known as plate tectonics. The water combines with the basalt to form granite and the mixture is reborn through volcanic eruptions.
"If there is granite on Venus, there must have been an ocean and plate tectonics in the past," says Müller.
Müller points out that the only way to know for sure whether the highland plateaus are continents is to send a lander there. Over time, Venus's water has been lost to space, but there might still be volcanic activity. The infrared observations are very sensitive to temperature. But in all images they saw only variations of between 3-20°C, instead of the kind of temperature difference they would expect from active lava flows.
Although Venus Express did not see any evidence of ongoing volcanic activity this time this time around, Müller does not rule it out. "Venus is a big planet, being heated by radioactive elements in its interior. It should have as much volcanic activity as Earth," he says. Indeed, some areas do appear to be composed of darker rock, which hints at relatively recent volcanic flows.
The new map gives astronomers another tool in their quest to understand why Venus is so similar in size to Earth and yet has evolved so differently.Venus Express has charted the first map of Venus's southern hemisphere at... more
More than 10,000 homes have been destroyed from an earthquake that struck southwest China, state media reported.
The 6.0-magnitude quake hit Yunnan province in southwest China Thursday evening, leaving more than 300 people injured, the Xinhua news service reported.
The quake happened at 7:19 p.m. (11:19 a.m. GMT) Thursday, at a depth of about 10 kilometers (6.2 miles), Xinhua reported.
Thirty people suffered severe injuries, and another 305 were slightly injured as of 1 a.m., relief officials in Yao'an County said.
Tents, medicine and food were seen being distributed by relief authorities, Xinhua said. Approximately 4,500 tents, 3,000 quilts and other relief material was being distributed, officials said, according to the Xinhua report.
Thursday's earthquake comes more than a year after a massive quake struck Sichuan province in China. The 8.0-magnitude quake on May 12, 2008 killed more than 68,000 people, left nearly 18,000 more missing and displaced 15 million others.More than 10,000 homes have been destroyed from an earthquake that struck southwest... more
An astonishing new map has revealed the elevation of nearly every place on Earth.
The Global Digital Elevation Model was created using nearly 1.3million images collected by a Japanese camera on board NASA's Terra spacecraft. It is made up of a giant grid of 23,000 tiles, with each height point spaced 98ft apart.
It shows a detailed representation of the planet's land mass. In this colourised version, low elevations are purple, medium elevations are greens and yellows, and high elevations are orange, red and white.
"This is the most complete, consistent global digital elevation data yet made available to the world," said Nasa scientist Woody Turner. "This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information."
Data from The Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) has been combined with other Aster images to create stunning terrain pictures of Death Valley and the Los Angeles Basin among others.
Aster was launched in 1999 along with four other instruments on the Earth Observing System. It takes about 600 high-resolution images a day, each one covering an area of 60 x 60 km.
It also provides scientists with information on land surface temperatures.
Researchers said it could be used for engineering, energy exploration, conserving natural resources, environmental management, firefighting, geology and city planning, to name just a few.
It is a large improvement on the previous best topographic map, where 80 per cent of the planet's landmass was surveyed during the Shuttle Radar Topography Mission.
'The Aster data filled in many of the voids in the shuttle mission's data, such as in very steep terrains and in some deserts,' said Michael Kobrick, from the Shuttle Radar project.
Nasa has 15 satellites that monitor the globe providing high-resolution data on how the globe in changing. Recently the Orbiting Carbon Observatory was destroyed during launch, which was a huge loss to the space agency's Earth Science program.An astonishing new map has revealed the elevation of nearly every place on Earth.... more
Hidden beneath the U.S. West's Great Basin, scientists have spied a giant blob of rocky material dripping like honey.
The Great Basin consists of small mountain ranges separated by valleys and includes most of Nevada, the western half of Utah and portions of other nearby states.
Here's how it works: "The Earth's mantle, which lies below the thin outer crust we live on, consists of rock which deforms plastically on very long time scales due to the heat and pressure at depth," West said. "In any material which can flow (including the mantle), a heavy object will tend to sink through lighter material."
And this is what the scientists think is happening with the lithospheric drip. A region of heavier material trapped in the lithosphere gets warmed up and begins to sink into the lighter, less dense mantle beneath, pulling a long tail of material after it.
"Honey dripping off of a spoon is a visual aid to what we think the drip looks like," West told LiveScience. "Dripping honey tends to lead with a large blob of honey, with a long tail of material following the initial blob."
He said the blob is between about 30 miles and 60 miles in diameter (between 50 km and 100 km) and extends from a depth of about 47 miles to at least 310 miles (75 km to 500 km) beneath Earth's surface.Hidden beneath the U.S. West's Great Basin, scientists have spied a giant blob of... more
"Forty years ago this month the lunar surface reverberated with life for the first time. Forty years from now will Mars, too, come alive? President Barack Obama has affirmed the broad goals for human spaceflight that his predecessor put forward in 2004: retire the shuttle in 2010, develop a replacement line of rockets (named Ares), return to the moon by 2020, and go to Mars, perhaps in the mid-2030s [see “To the Moon and Beyond,” by Charles Dingell, William A. Johns and Julie Kramer White; Scientific American, October 2007]. The program is known as Constellation.
Mountains higher than the walls of the Grand Canyon of the Colorado towered above the long, narrow valley of Taurus-Littrow. A brilliant sun, brighter than any sun experienced on Earth, illuminated the cratered valley floor and steep mountain slopes, starkly contrasted against a blacker-than-black sky. My crewmate Gene Cernan and I explored this nearly four-billion-year-old valley, as well as the slightly younger volcanic lava rocks and ash partially filling it, for three days in 1972—concluding the Apollo program. It was the first and, so far, only time a geologist has ever done hands-on study of another world. Now the U.S., the European Union, Russia and other international partners are contemplating sending astronauts to Mars to do fieldwork there, probably beginning within the first third of this century. What will be new and what will be familiar to the first geologist to step before a red Martian sunrise?
For each new body that people explore, we must build on our experience exploring the last place we have been—as geologists have done on Earth for more than two centuries. We must continually ask what may be similar and what may be different. How will Martian geology, accessibility, exploration strategy and optimal crew composition compare with the experience of Apollo?
On Mars, scientists expect influences that combine those affecting Earth and the moon, because the Red Planet is intermediate in size. Indeed, our growing geologic knowledge about Mars already confirms this blend of processes. Since the first photographs provided by orbital cameras and the Viking landers, we have known that geologic features on Mars resulted from combinations of internal and external influences."
Much more at link!
So cool to think about the inevitable day that people will explore Mars! Ponder the future!"Forty years ago this month the lunar surface reverberated with life for the... more
When Travis County installed two huge water pumps to water a nearby park, the water well used by Tecolote Farm, an organic farm, in Manor, TX ran dry. More than a year later, a University of Texas geology professor and his students are on site running experiments and tests in search for a water source.
If they do identify a water source, the county has agreed to pay $5000 for drilling test wells. I contacted the professor for an update a couple of days later to follow up on their results. I have not received a response.When Travis County installed two huge water pumps to water a nearby park, the water... more
