Several Powerful Earthquakes In the News Today

Am posting several earthquake news related articles and links here:

Several powerful earthquakes today in Alaska, Japan and Peru. The earth seems to be entering yet another very active quake phase, very similar pattern I was watching before the West Coast earthquakes in the mid and late '80's.

Coincidentally, there are also some rather interesting articles on quakes published today, one on the 2004 India quake that moved land up to 60 meters. Also an article about talc being found in quake fault areas that is believed to help smooth the friction between moving plates.

And finally, links to two interesting lists and maps on the USGS site, a list of the several 5.0+ quakes in the word in the last 7 days and a map of all quakes in the world in the last 30 days that also shows definite movements along the various plate boundaries of the world.

http://www.stuff.co.nz/print/4167050a10.html


Powerful earthquakes hit Peru
LATEST: Two powerful earthquakes have struck Peru within minutes of each other, rattling buildings in the capital and triggering a tsunami warning.

The quakes had a magnitude of about 7.5 and office workers ran onto the streets in fear as buildings in Lima shook in two bouts that lasted around 20 seconds each.
The Pacific Tsunami Warning Center in Hawaii has just issued a region wide warning say it was declaring an "expanding regional tsunami warning and watch for parts of the Pacific located closer to the earthquake."

It said it was urgently evaluation the possibility of a Pacific wide tsunami.

New Zealand has been hit previously by tsunami generated by South American earthquakes. They take around 16 hours to cross the South Pacific.

Peruvian civil defense officials said there were no immediate reports of fatalities but radio stations said there was a fire in one district of Lima and that several poorly constructed homes in Pisco, a town near the epicenter of the quake, were knocked down.

Ambulance sirens blared in the darkened capital and the health ministry declared a disaster.

"People here hugging and crying in fear on the streets," said Cristyane Marusiak, a 31-year-old resident.

The U.S. Geological Survey said the first quake hit about 25 miles northwest of Chincha Alta and that the second quake hit shortly afterward, both with a magnitude of 7.5.

The USGS says earthquakes measuring more than 7 magnitude often result in fatalities.

http://www.desastres.org/noticias.php?id=15082007-18


No Tsunami Expected from Alaska Quake
Publicado - Published: 15/08/2007
HONOLULU.- A moderately strong earthquake occurred in Alaskan ocean waters at 10:22 a.m. today Hawai'i time, according to the United States Geographic Survey.

While destructive tsunamis generated by earthquakes in Alaska have reached Hawai'i shores in the past, the Pacific Tsunami Warning Center in 'Ewa Beach issued an advisory shortly after today's quake saying no widespread tsunami threat exists based on historical earthquake and tsunami data.

The quake's epicenter was approximately 13.2 miles beneath the ocean's surface and nearly 100 miles south-southwest of Adak, Alaska, and about 1,300 miles west-southwest of Anchorage, according to the center.

The USGS assigned a preliminary magnitude of 6.5 to the temblor.

http://www.bloomberg.com/apps/news?pid=20601080&sid=a4wDrMl7CRcs&refer=asia

Japan's East Coast Shaken By Magnitude 5.4 Quake (Update2)
By Ron Rhodes

Aug. 16 (Bloomberg) -- A magnitude 5.4 earthquake shook the east coast of Japan's main island of Honshu at 4:15 a.m. local time, followed by aftershocks. There were no reports of damage or injuries and no tsunami alerts were issued.

The first quake was centered about 64 kilometers (40 miles) southeast of Tokyo off the east coast of Chiba Prefecture, the U.S. Geological Survey said on its Web site. Temblors that followed originated in the same area.

The epicenter was 34 kilometers beneath the seabed. No tsunami warnings were issued. The Japan Meteorological Agency said the quake had an intensity of as much as 4, on the seven- point Japanese scale, in Chiba City and 3 in eastern Tokyo.

Aftershocks that followed shook buildings in central Tokyo. The first, with a magnitude of 4, was recorded in the same area at 5:04 a.m., followed by a magnitude 5 temblor at 8:20 a.m., and a magnitude 4.7 quake at 9:22 a.m., the Japanese agency said.

Japan, one of the world's most earthquake-prone countries, is located in a zone where the Eurasian, Pacific, Philippine and North American tectonic plates meet and occasionally shift, causing earthquakes. Quakes of magnitude 5 and more can cause considerable damage.

The last big earthquake in Japan struck July 16 in the north-central prefecture of Niigata, killing 11 people and injuring more than 1,000. Damage from the magnitude 6.8 quake forced Tokyo Electric Power Co. to shut down reactors at its biggest nuclear power plant.

A quake that hit the same area in 2004 killed 33 people, shut a section of a bullet train line and halted production at a semiconductor plant operated by Sanyo Electric Co.





http://www.hinduonnet.com/thehindu/thscrip/print.pl?file=2007081558450100.htm&date=2007/08/15/&prd=th&

2004 earthquake shifts southern Indian cities


Horizontal movement towards Nicobar
Major tectonic shift occurred at a fast pace
Land mass might take long to return to earlier position


HYDERABAD: The Andaman and Nicobar belt moved horizontally by 3 metres to 6 metres, Chennai by 2 cm, Bangalore by 1.5 cm and Hyderabad by 11 mm following the undersea Sumatra-Andaman earthquake in 2004.

In the normal course such a tectonic shift would have taken hundreds of years to occur but it happened in less than 10 minutes during the earthquake. The impact caused by the 9.2 magnitude temblor could be gauged by the fact that the Indian plate was moving at the rate of 4 cm a year with respect to the Burmese plate.

Scientists from the National Geophysical Research Institute (NGRI) who carried out GPS-based studies in the Andaman and Nicobar islands before and after the earthquake, told The Hindu on Monday that horizontal movement was noticed t owards the Nicobar side.

While a 3-m movement was found in the middle of Andamans, it was 6 m between Car Nicobar and Great Nicobar.

The entire island also subsided by 1 m to 2 m vertically. Interestingly, it began to rise again but at a slow speed, and 30 per cent of the land had ?'re-emerged,' said NGRI Director V.P. Dimri and seismologist V.K. Gahalaut.

Explaining that the uplift of the subsided land mass was occurring in a non-linear manner, they said it might take up to a couple of hundred years for it to return to the pre-2004 position.

Dr. Gahalaut said the boundary between the Indian plate and the Burmese plate, in the sub-duction zone, is about 150 km west of the Andamans. The overriding plate (Burmese) moved by 3 m to 6 m during the earthquake along the 1,500-km faultline extending from North Andaman to West Sumatra.

He explained that before the earthquake, the Indian and Burmese plates were moving together as they were locked and there was no relative movement between the two.

After the earthquake, they got disengaged and the Burmese plate was moving in a southwest direction with respect to the Indian plate at a rate which is faster than the normal plate motion but less than the speed which occurred during the massive temblor.




http://www.nature.com/news/2007/070813/full/070813-6.html

Published online: 15 August 2007; | doi:10.1038/news070813-6

Talc softens earthquake chafing
Mineral shown to ease part of California's quake zone.
Rex Dalton

At least one area of the San Andreas fault that 'creeps' rather than quaking is softened by some talc.

Punchstock

Talc, the balm that stops chafing for babies' bottoms, seems also to soften the rubbing along some faults within the Earth.

Researchers drilling deep into the San Andreas fault in California report in today's Nature1 the presence of talc inside a relatively sedate section of the famous fault. This seems to explain why this region of the fault typically creeps slowly to relieve stress, rather than experiencing the abrupt slips that cause large earthquakes.

"It looks like the talc prevents the fault from shooting off to cause big quakes," says Christopher Wibberley, a geologist at the University of Nice in France, who has written a companion analysis about the work for Nature2.

Talc is the softest known natural material. In this case, it is created by minerals and water reacting under the high pressure created by Earth's slabs grinding together 3,000 metres deep within the fault, which runs the length of much of California.

"I wasn't specifically looking for talc, so it was neat to find this result," says Diane Moore, a petrologist at the US Geological Survey in Menlo Park and lead author on the study.

Soft touch

The discovery was made after examining samples from near the bottom of a 3,000-metre shaft drilled into the fault line at Parkfield in 2005. This was done as part of a groundbreaking study to place monitoring devices deep into an active fault zone ?- a project known as the San Andreas Fault Observatory at Depth (SAFOD).

At Parkfield, which lies in a valley some 200 kilometres south of the San Francisco Bay, the fault creeps at a rate of as much as 28 millimetres a year. North and south of this sedate section, the fault is known for 'stick and slip' action, which leads to large earthquakes with little fault movement in intervening years.

Moore, who studies rock deformations, was looking for a mineral called serpentine in the drill cuttings ?- a relatively soft mineral found at Parkfield's surface that has previously been posited as the cause for slow creep in this part of the fault zone. Some think that this mineral is still too hard to really explain what's controlling the fault, but it was worth looking for.

Moore found serpentine. But she also discovered talc ?- a mineral that's chemically related to serpentine and often found alongside it ?- which is even softer. This far better explains the slow creep underground.

"This goes a long way toward explaining what is happening at that depth there," says Wibberley, adding that it doesn't explain activity along the other sections of the San Andreas fault.

The SAFOD team this June began to drill at an angle out of their primary shaft into other areas of the fault zone known to be more seismically active. Moore and her colleagues are keen to see how the presence of talc may differ in these parts of the fault.



Latest Earthquakes M5.0+ in the Workd - Past 7 days

Map and List of Recent Earthquakes - Last 30 Days