|  Author | Topic: Earthquakes III (Read 7,418 times) |
Big Bunny
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|  | Re: Earthquakes III
« Reply #30 on Mar 8, 2010, 9:37am » | |
Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
08-MAR-2010 11:37:35 18.70 145.93 5.0 219.2 MARIANA ISLANDS
08-MAR-2010 09:47:10 19.34 144.73 6.0 446.5 MARIANA ISLANDS
http://www.iris.edu/seismon/
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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: Earthquakes III
« Reply #31 on Mar 8, 2010, 7:18pm » | |
Chile quake moved entire city 3 metres to west: study
* From correspondents in Santiago
* From: AFP
* March 09, 2010 10:22AM
THE massive earthquake which struck the west coast of Chile last month moved the entire city of Concepcion more than three metres to the west.
Preliminary measurements drawn from global positioning stations showed that Concepcion, Chile's second largest city, is now 3.04 meters further west than it was prior to the 8.8-magnitude quake which struck February 27.
It was the fifth most powerful quake recorded since instruments have been available to measure seismic shifts and there have been hundreds of aftershocks, several exceeding magnitude 6.0.
The Chilean capital of Santiago also shifted 27.7 centimetres to the west, according to measurements gathered by a team of Chilean and US scientists and released by Ohio State University.
On South America's east coast, Argentina's capital Buenos Aires moved nearly four centimetres to the west and significant displacements were recorded as far away as the Falkland Islands.
http://www.news.com.au/breaking-news/wor....-12258 38565777
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: Earthquakes III
« Reply #32 on Mar 11, 2010, 10:43am » | |
 Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
11-MAR-2010 15:06:03 -34.22 -71.89 6.0 32.0 NEAR COAST OF CENTRAL CHILE
11-MAR-2010 14:55:30 -34.29 -71.66 6.9 44.4 NEAR COAST OF CENTRAL CHILE
11-MAR-2010 14:39:48 -34.29 -71.95 7.2 35.0 NEAR COAST OF CENTRAL CHILE
http://www.iris.edu/seismon/
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #33 on Mar 20, 2010, 11:06am » | |
Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
20-MAR-2010 14:00:51 -3.38 152.23 6.2 423.5 NEW IRELAND REGION, P.N.G.
http://www.iris.edu/seismon/
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #34 on Mar 20, 2010, 11:53pm » | |
Hundreds evacuated after volcano erupts
* From correspondents in Reykjavik, Iceland
* From: AFP
* March 21, 2010 2:06PM
![[image]](http://img638.imageshack.us/img638/2388/47508859volcano7488458.jpg "[image]")
The eruption lit up the night sky just after midnight on Saturday
A VOLCANO in the area of the Eyjafallajoekull glacier in southern Iceland erupted today, forcing more 500 people in its vicinity to evacuate their homes, authorities said.
"We estimate that no one is in danger in the area but we have started an evacuation plan and between 500 and 600 people are being evacuated" Sigurgeir Gudmundsson of the Icelandic civil protections department said.
Public broadcaster RUV reported that the eruption had started shortly after midnight and that the area's main road had been closed.
A volcano in the area of the Eyjafjallajokull glacier last erupted in 1821 and 1823.
http://www.news.com.au/breaking-news/hun....0-1225843382083
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: Earthquakes III
« Reply #35 on Mar 25, 2010, 2:13am » | |
Volcanic eruption seen from plane
![[image]](http://img691.imageshack.us/img691/120/volcano16389480.jpg "[image]")
Mushroom cloud ... the Soufriere Hills volcano erupts. (Mary Jo Penkala/Solent)
09:30 AEST Thu Mar 25 2010
By ninemsn staff
A holidaymaker onboard a passenger jet has captured the spectacular eruption of a Caribbean volcano.
Hairdresser Mary Jo Penkala took the photographs after the pilot of the Boeing 737 told passengers the Soufriere Hills volcano in Montserrat was shooting ash and dust 12,000m into the sky.
"It was certainly an interesting start to our vacation," Mrs Penkala said.
Half of the Monsterrat island is uninhabited because of constant volcanic eruptions.
http://news.ninemsn.com.au/glance/1031796/volcanic-eruption-seen-from-plane
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #36 on Mar 25, 2010, 11:04am » | |
Strong quake strikes near Manila
A strong earthquake has struck close to the Philippine capital, Manila, but officials say there are no immediate reports of damage.
Residents said that buildings in the city shook after the tremor and employees rushed out of buildings.
The quake, with a magnitude of 6.1, struck in the sea 135km (85 miles) to the southwest of Manila, the US Geological Survey said.
An hour after the quake, officials said there were no reports of damage.
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/asia-pacific/8586460.stm
Published: 2010/03/25 07:24:33 GMT
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #37 on Mar 31, 2010, 12:39am » | |
Undersea volcano could destroy Italy 'as soon as tomorrow', expert warns
* From correspondents in Rome
* From: AFP
* March 30, 2010 12:52AM
EUROPE'S largest undersea volcano could disintegrate and unleash a tsunami that would engulf southern Italy "at any time", a prominent vulcanologist has warned.
The Marsili volcano, which is bursting with magma, has "fragile walls" that could collapse, Enzo Boschi told the leading daily Corriere della Sera.
"It could even happen tomorrow," Prof Boschi, president of the National Institute of Geophysics and Volcanology said
"Our latest research shows that the volcano is not structurally solid, its walls are fragile, the magma chamber is of sizeable dimensions," he said.
"All that tells us that the volcano is active and could begin erupting at any time."
The event would result in "a strong tsunami that could strike the coasts of Campania, Calabria and Sicily," Prof Boschi said.
The undersea Marsili, 3000m tall and located some 150km south-west of Naples, has not erupted since the start of recorded history.
It is 70km long and 30km wide, and its crater is some 450m below the surface of the Tyrrhenian Sea.
"A rupture of the walls would let loose millions of cubic metres of material capable of generating a very powerful wave," Prof Boschi said.
"While the indications that have been collected are precise, it is impossible to make predictions.
"The risk is real but hard to evaluate."
http://www.news.com.au/breaking-news/und....0-1225847214540
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #38 on Mar 31, 2010, 12:45am » | |
Toads can predict earthquakes - study
* From: NewsCore
* March 31, 2010 9:51AM
FOR ages, mankind has craved a tool that can provide an early warning of that terrifying moment when the earth begins to shake - and if a scientific paper published today is confirmed, we may at last have found one.
The best hope yet of an earthquake predictor could lie in a small, brown, knobbly amphibian, it suggests.
The male common toad (Bufo bufo) gave five days' warning of the earthquake that ravaged the town of L'Aquila in central Italy on April 6, 2009, killing more than 300 people and displacing 40,000 others, the study says.
Biologist Rachel Grant of Britain's Open University embarked on a toad-monitoring project at San Ruffino lake 74km north of L'Aquila, 10 days before the 6.3-magnitude quake struck.
Her two-person team observed the site for 29 days, counting toad numbers and measuring temperature, humidity, wind speed, rainfall and other conditions.
By March 28, more than 90 male toads had mustered for the spawning season, but two days later, their numbers suddenly fell, Grant reports.
By April 1 - five days before the quake - 96 per cent of the males had fled.
Several dozen ventured back on April 9 for the full moon, a known courtship period for toads, although the tally was some 50-80 per cent fewer than in previous years.
After this small peak, the numbers fell once more, only picking up significantly on April 15, two days after the last major aftershock, defined as 4.5 magnitude or higher.
In addition, the number of paired toads at the breeding site also dropped to zero three days before the quake. And no fresh spawn was found at the site from April 6 until the last big after-tremor.
Ms Grant said the toads' comportment is a "dramatic change" for the species.
Once male toads hole up at a breeding site, they usually never leave until the annual spawning season is over, she notes.
Eager to answer the riddle, Ms Grant obtained Russian measurements of electrical activity in the ionosphere, the uppermost electromagnetic layer in the atmosphere, which were picked up by very low frequency (VLF) radio receivers.
The toads' two periods of exodus both coincided with bursts of VLF disruption.
Previous research has attributed perturbations in the ionosphere to releases of radon, a radioactive gas generated underground, or to gravity waves prior to a quake, although much about this phenomenon is unclear.
In the quest to find an earthquake predictor, elephants, horses, wolves, snakes and fish have all been variously put forward.
This study, though, is exceptional. It puts the flesh of data and first-hand observation on the bones of anecdotal evidence, even if there is no confirmed explanation as to why the toads bolted as they did.
"Our study is one of the first to document animal behaviour before, during and after an earthquake," Ms Grant said.
"Our findings suggest that toads are able to detect pre-seismic cues such as the release of gases and charged particles and use these as a form of early warning system."
The paper is published in the Journal of Zoology by the Zoological Society of London.
http://www.news.com.au/breaking-news/wor....i-1225847829530
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #39 on Mar 31, 2010, 12:50am » | |
Further to the recent Icelandic volcanic eruption:
Saturday 6th March 2010
Eyjafjoll volcano, Iceland
An earthquake swarm began under Eyjafjoll volcano in January 2010. There was a 40 mm inflation of the volcano. At the beginning of March 2010 over 3000 earthquakes were measured in a 24 hour period, with a maximum at magnitude 3.1. The last eruptions at Eyjafjoll volcano were in 1821-23.
Sunday 21st March 2010
Eyjafjoll volcano, Iceland
An eruption began near the Eyjafjallajökull glacier on 21st March 2010. Locals reported lava fountaining and a lava flow from the glacier. Residents were evacuated. The eruption was limited to an area with little ice, so the threat of a flood was reduced. All flights to and from Iceland have been cancelled because of the eruption. There is a 120 mile radius no fly zone around the volcano.
Tuesday 23rd March 2010
Eyjafjoll volcano, Iceland
Eruptions continue at Eyjafjoll (Eyjafjallajökull) volcano in Iceland. 500 people have been evacuated from near the volcano. The eruptions at the volcano began on the evening of 20-21 March with Hawaiian style activity, at a 500 m long NE-SW fissure. The eruptions were on the NE flank of the volcano at an elevation of 1000 m. There were small ash emissions and a lava flow. The eruption occurred on a 2 km wide area of ice-free land between Eyjafjallajökull and neighboring Katla volcano. Eyjafjöll has been much less active than neighboring volcanoes. Since 1600's there have only been three eruptions at Eyjafjoll, while nearby Katla had 20 eruptions.
http://www.volcanolive.com/news.html
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #40 on Apr 5, 2010, 12:09am » | |
Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
05-APR-2010 01:25:40 32.37 -114.85 4.6 11.8 W. ARIZONA-SONORA BORDER REGION
05-APR-2010 00:07:11 31.89 -114.78 5.1 9.6 GULF OF CALIFORNIA
04-APR-2010 23:25:09 32.12 -115.06 5.4 10.0 CALIF.-BAJA CALIF. BORDER REGION
04-APR-2010 23:15:14 31.90 -115.14 5.2 10.0 BAJA CALIFORNIA, MEXICO
04-APR-2010 22:40:45 32.19 -115.10 7.0 10.0 CALIF.-BAJA CALIF. BORDER REGION
31-MAR-2010 09:20:25 32.36 -115.22 4.1 8.0 CALIF.-BAJA CALIF. BORDER REGION
30-MAR-2010 09:14:18 31.68 -113.53 4.5 10.0 GULF OF CALIFORNIA
28-MAR-2010 17:22:51 23.58 -108.84 4.2 10.0 GULF OF CALIFORNIA
http://www.iris.edu/seismon/
![[image]](http://img535.imageshack.us/img535/6005/779014californiaearthqu.jpg "[image]")
Large earthquake shakes southern California
* By staff writers
* From: news.com.au
* April 05, 2010 1:37PM
![[image]](http://img542.imageshack.us/img542/7660/905811bajaearthquake376.jpg "[image]")
A US Border Patrol agent walks past rows of broken glass from windows in downtown Calexico, California / AP Source: AP
* Video: http://img14.imageshack.us/img14/2185/largeearthquakeshakesso.mp4
ONE person has been reported dead after a 7.2-magnitude earthquake rocked Southern California. The Southern California Seismic Network recorded the quake shortly after 8.45am (AEDT).
The US Geological Survey said the 7.2 magnitude quake struck in Baja, California, about 173km east-southeast of Tijuana.
![[image]](http://img694.imageshack.us/img694/9571/27371201103047340.gif "[image]")
CNN reported the earthquake was stronger than the one that hit Haiti in January, and shook highrise buildings hundreds of kilometres away in Los Angeles and San Diego.
There have been a series of aftershocks in the region, with several topping magnitude 5 according to data recorded by the US Geological Survey.
One person was killed when a building collapsed in Mexicali, the capital of Baja California, according to the assistant director of civil protection in Tijuana, CNN reported.
Mexicali, a city of 900,000 people, is just 18km from the epicentre and there were reports of sides of buildings falling apart, telephone poles collapsing and roads cracking.
But there were no reports of major damage or casualties in the US from the earthquake, which struck at 3.40pm (local time) at a depth of 10km, 26km south-southwest of Guadalupe Victoria, Baja California, Mexico.
Twitter users reported that Disneyland was evacuated. People were stuck in lifts and of many reported water sloshing out of swimming pools.
A spokesperson for Disneyland told news.com.au all rides were initially closed down following the earthquake, but they are back operating as normal.
"Our normal protocol following an earthquake is to cycle out all attractions for a safety inspection," the spokesperson said. "We have no reports of injury or damage. Nearly all attractions have been inspected and are back online."
The strong earthquake south of the US-Mexico border shook high-rises in downtown Los Angeles and San Diego and was felt across Southern California and Arizona.
Residents said the quake shook "for a long time".
"We felt it for about 30 seconds. It was rolling," San Diego County Sheriff's Lt. Scott Ybarrondo told CNN. "Nothing fell off the walls here, but we have reports of pictures falling off walls elsewhere in the county."
The quake was felt as far north as Santa Barbara, USGS seismologist Susan Potter said.
A 4.1-magnitude tremor was recorded near Santa Rosa, in northern California, about nine minutes after the Baja California quake, CNN said. The USGS recorded a 5.1 aftershock 1.6km from Imperial, California.
People trapped in lifts, buildings damaged
In LA, the city fire department went on "earthquake status", and some stalled lifts were reported. No damage was reported in LA or San Diego.
One woman called firefighters and said she was stuck in a lift descending from the 34th floor in a building in Century City, but there was no way to immediately know if the breakdown was tied the quake, LA firefighter Eric Scott said.
Los Angeles City Fire Department crews responded to people trapped in stalled elevators in the city, but there were no reports of serious damage, power outages or injuries in L.A.
In San Diego several buildings and water mains were reported damaged, according to the San Diego Fire Department.
While in Yuma, Arizona, the sheriff's department said it was responding to building alarms.
The quake was felt for about 40 seconds in Tijuana, Mexico, causing buildings to sway and knocking out power in parts of the city. Families celebrating Easter ran out of the homes, with children screaming and crying.
Baja California state Civil Protection Director Alfredo Escobedo said there were no immediate reports of injuries or major damage. But he said the assessment was ongoing.
In the Phoenix area, Jacqueline Land said her bed in her second-floor apartment felt like a boat gently swaying on the ocean.
"I thought to myself, 'That can't be an earthquake. I'm in Arizona,'" the Northern California native said. "And I thought, 'Oh my God, I feel like I'm nine years old.'"
Mike Wong, who works at a journalism school in downtown Phoenix, said he was in his second-floor office getting some work done when he heard sounds and felt the building start to sway.
"I heard some cracking sounds, like Rice Krispies," coming from the building, he said. "I didn't think much of it, but I kept hearing it, and then I started feeling a shake. I thought, 'You know what? I think that might be an earthquake."
Mr Wong said the swaying lasted for "just a few seconds", and he didn't notice any damage.
"Because of the location of the earthquake, it will have been felt by a large number of people," said Susan Potter, a geophysicist with the USGS told The Wall Street Journal.
Within an hour of the earthquake, more than 4000 people had filed reports with the USGS saying they had felt shaking.
By comparison, the earthquake that hit Haiti on January 12 was a 7.0 magnitude earthquake. An earthquake that struck near Concepcion, Chile on February 27 was listed as an 8.8-magnitude earthquake.
- with The Associated Press
http://www.news.com.au/world/large-earth....i-1225849747564
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
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Big Bunny
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| | Re: Earthquakes III
« Reply #41 on Apr 5, 2010, 9:12am » | |
Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
05-APR-2010 12:11:01 -0.13 125.16 5.0 10.0 SOUTHERN MOLUCCA SEA
05-APR-2010 10:05:42 -0.17 125.01 6.2 10.0 SOUTHERN MOLUCCA SEA
http://www.iris.edu/seismon/
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #42 on Apr 6, 2010, 6:47pm » | |
Latest significant seismic activity:
DATE LAT LON MAG DEPTH REGION
06-APR-2010 22:15:02 2.24 97.05 7.8 46.0 NORTHERN SUMATERA, INDONESIA
04-APR-2010 12:43:15 2.53 95.81 4.4 35.0 OFF W COAST OF NORTHERN SUMATERA
03-APR-2010 22:33:43 -2.21 100.08 5.1 44.1 SOUTHERN SUMATERA, INDONESIA
03-APR-2010 14:50:01 1.83 98.99 4.8 133.9 NORTHERN SUMATERA, INDONESIA
02-APR-2010 02:21:22 -1.83 100.60 4.7 82.6 SOUTHERN SUMATERA, INDONESIA
29-MAR-2010 05:01:00 0.89 97.43 4.4 35.0 NORTHERN SUMATERA, INDONESIA
24-MAR-2010 09:29:43 -6.59 104.62 4.8 77.0 SUNDA STRAIT
http://www.iris.edu/seismon/
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #43 on Apr 6, 2010, 7:01pm » | |
Huge quake hits Sumatra
Updated 7 minutes ago
![[image]](http://img708.imageshack.us/img708/8701/r54406231771398228872.jpg "[image]")
Graphic showing the 7.8 magnitude earthquake that struck off the coast of Sumatra (http://neic.usgs.gov)
A huge 7.7-magnitude earthquake has struck just off the west coast of Sumatra in Indonesia.
The quake struck the Simeulue region around 205 kilometres from the town of Sibolga shortly before 5:15am (local time) today at a depth of about 46 kilometres.
Witnesses have reported power blackouts and panic on Simeulue island in the wake of the quake but there have been no reports of damage or casualties so far.
Indonesia's quake agency says there have been at least three aftershocks off Aceh. Metro TV is reporting that people have rushed to higher ground in some areas.
There are conflicting reports about the chances of the earthquake generating a major tsunami.
The Pacific Tsunami Warning Centre said: "A destructive widespread tsunami threat does not exist based on historical earthquake and tsunami data."
But it added: "There is the possibility of a local tsunami that could affect coasts" no more than 100km from the epicentre of the quake."
Tsunami waves up to 14 centimetres have been recorded at Teluk Dalam on Pulau Nias island, south west of Sibolga.
But Thailand issued a tsunami alert, warning people to evacuate from coastal areas.
The US Geological Survey originally measured the quake at 7.6 before upgrading it to 7.8 and then downgrading it to 7.7.
Indonesia sits in the Pacific ring of fire, an area prone to earthquakes because of the constant movement of volcanic belts and plates.
In December 2004 a magnitude 9.15 quake off the coast of Sumatra's Aceh province triggered an Indian Ocean tsunami that killed about 226,000 people in Indonesia, Sri Lanka, India, Thailand and nine other countries.
In March 2005 about 1,300 people were killed after an 8.7-magnitude quake struck off the coast of the Indonesian island of Nias, west of Sumatra.
A 7.6-magnitude quake in West Sumatra province in September last year killed about 1,000 people, according to official figures.
http://www.abc.net.au/news/stories/2010/04/07/2865886.htm
|
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
"In the final analysis, our most basic common link is that we all inhabit this small planet, breathe the same air, and we all cherish our children’s future."
John F. Kennedy |
|
Big Bunny
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| | Re: Earthquakes III
« Reply #44 on Apr 10, 2010, 7:02pm » | |
Not So Fast! Andes Rise Was Gradual, Not Abrupt
![[image]](http://img530.imageshack.us/img530/5536/100401143119large222021.jpg "[image]")
Jirishanca, Yerupaja and Siula mountains in high Andes. (Credit: iStockphoto/Steve Estvanik)
ScienceDaily (Apr. 4, 2010) — Trailing like a serpent's spine along the western coast of South America, the Andes are the world's longest continental mountain range and the highest range outside Asia, with an average elevation of 13,000 feet.
The question of how quickly the mountains attained such heights has been a contentious one in geological circles, with some researchers claiming the central Andes rose abruptly to nearly their current height and others maintaining the uplift was a more gradual process.
New research by U-M paleoclimatologist Christopher Poulsen and colleagues suggests that the quick-rise view is based on misinterpreted evidence. What some geologists interpret as signs of an abrupt rise are actually indications of ancient climate change, the researchers say. Their findings are scheduled to be published online April 1 in Science Express.
The confusion results when ratios of oxygen's two main isotopes, oxygen-18 and oxygen-16, are used to estimate past elevation, said Poulsen, an associate professor with appointments in the departments of Geological Sciences and Atmospheric, Oceanic, and Space Sciences.
"In the modern climate, there is a well-known inverse relationship between oxygen isotopic values in rain and elevation," Poulsen said. "As a rain cloud ascends a mountain range, it begins to precipitate. Because oxygen-18 is more massive than oxygen-16, it is preferentially rained out. Thus, as you go up the mountain, the precipitation becomes more and more depleted in oxygen-18, and the ratio of oxygen-18 to oxygen-16 decreases."
Geologists use the ratio of these isotopes, preserved in rock, to infer past elevations.
"If the ratio decreases with time, as the samples get younger, the interpretation would typically be that there has been an increase in elevation at that location," Poulsen said. In fact, that's exactly the conclusion of a series of papers on the uplift history of the Andes published over the past four years. Using oxygen isotopes in carbonate rocks, the authors posited that the central Andes rose about 8,200 to 11,500 feet in three million years, rather than gaining height over tens of millions of years, as other geologists believe.
But elevation isn't the only factor that affects oxygen isotope ratios in rain, Poulsen said. "It can also be affected by where the vapor came from and how much it rained---more intense rainfall also causes oxygen-18 to be preferentially rained out." Skeptical of the rapid-rise scenario, he and his colleagues performed climate modeling experiments to address the issue.
"The key result in our modeling study is that we identified an elevation threshold for rainfall," Poulsen said. "Once the Andes reached an elevation greater than 70 percent of the current elevation, the precipitation rate abruptly increased. In our model, the increased precipitation also caused the ratio of oxygen-18 to oxygen-16 to significantly decrease. Our conclusion, then, is that geologists have misinterpreted the isotopic records in the central Andes. The decrease in the ratio is not recording an abrupt increase in elevation; it is recording an abrupt increase in rainfall."
This conclusion is backed up by geochemical and sedimentological data, Poulsen said. "There is evidence that the central Andes became less arid at the same time that the isotope records show a decrease in the ratio of oxygen-18 to oxygen-16."
Poulsen's coauthors are Todd Ehlers of the University of Tuebingen in Germany and U-M graduate student Nadja Insel.
Funding was provided by the National Science Foundation, the U-M Graham Environmental Sustainability Institute and the Alexander von Humboldt Foundation.
Journal Reference:
1. C. J. Poulsen, T. A. Ehlers, N. Insel. Onset of Convective Rainfall During Gradual Late Miocene Rise of the Central Andes. Science, 2010; DOI: 10.1126/science.1185078
http://www.sciencedaily.com/releases/2010/04/100401143119.htm
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