Earthquakes
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Bizarro Earth

Tsunami watch in Indonesia lifted after two big earthquakes

Image
Epicenter of earthquake off the coast of northern Sumatra.
A massive earthquake struck off the coast of the Indonesian island of Sumatra on Wednesday afternoon, triggering a tsunami watch for the Indian Ocean, which was later canceled.

The quake struck about 434 kilometers (270 miles) southwest of Banda Aceh, the capital of Indonesia's Aceh province, and had a magnitude of 8.6, the U.S. Geological Survey said. It took place at a depth of 23 kilometers (14 miles).

A second large quake, with a magnitude of 8.2, occurred off the west coast of Sumatra about two hours later, the USGS said.

Gary Gibson from the Seismology Research Center in Melbourne, Australia, said the location of the second quake reduced the possibility of a tsunami.

There was also a series of smaller quakes off the west coast of northern Sumatra with magnitudes between 5.1 and 5.4.

There were no reports of destruction or deaths.

Indonesian President Susilo Bambang Yudhoyono said on local television that there were no reports of casualties or damage in Aceh.

Four people were slightly injured on Simeulue Island, off the coast of Aceh, the National Disaster Management Agency said Wednesday.

The Pacific Tsunami Warning Center issued a tsunami watch for the entire Indian Ocean. And a few hours later, the center announced the tsunami watch was canceled.

"A significant tsunami was generated by this earthquake. However, sea level readings now indicate that the threat has diminished or is over for most areas," the center said.

Radar

Tsunami - Caught On Camera

The following Channel 4 (UK) documentary captures the dreadful moments when a devastating tsunami washed away a quarter of a million people in the Indian Ocean in December 2004.


Bizarro Earth

USGS: Earthquake Magnitude 6.5 - Michoacan Mexico

Image
© USGS
Date-Time:

Wednesday, April 11, 2012 at 22:55:16 UTC

Wednesday, April 11, 2012 at 05:55:16 PM at epicenter

Time of Earthquake in other Time Zones

Location:

18.390°N, 102.652°W

Depth:

65.6 km (40.8 miles)

Region:

MICHOACAN, MEXICO

Distances:

69 km (42 miles) NW of Lazaro Cardenas, Michoacan, Mexico

129 km (80 miles) SSW of Uruapan, Michoacan, Mexico

143 km (88 miles) NW of Zihuatanejo, Guerrero, Mexico

384 km (238 miles) WSW of MEXICO CITY, D.F., Mexico

Bizarro Earth

Why Today's Indonesia Quake Didn't Make a Monster Tsunami

Indonesian Quake_110412
© USGSThe red star marks where the quake hit.

The magnitude 8.6 earthquake that struck in the Indian Ocean off the western coast of Sumatra today resurrected fears of a repeat of the 2004 Indian Ocean earthquake and tsunami that proved one of the most devastating natural disasters in modern memory.

However, this earthquake, which struck at 2:38 p.m. local time (4:38 a.m. ET), about 270 miles (435 kilometers) off the coast of the Indonesian island was a different animal altogether than the 2004 earthquake and tsunami, which killed more than 230,000 people and left millions homeless.

"It was quite a bit smaller," said Julie Dutton, a geophysicist with the U.S. Geological Survey. The 2004 quake was a magnitude 9.1 - the third most powerful earthquake ever recorded.

Perhaps more significantly, today's earthquake was a different kind of quake all together. Instead of occurring at a plate boundary along an area called a subduction zone, where one tectonic plate is diving beneath another, this earthquake occurred in the middle of an oceanic plate, where the faults in the crust essentially moved from side to side instead of up and down. These sorts of events are called strike-slip earthquakes.

"With a strike-slip event you don't have the same potential hazard for a tsunami as you do with a subduction event because the plates are moving adjacent to each other," Dutton told OurAmazingPlanet.

Bizarro Earth

Number of earthquakes more than double in Arizona in 2011

Image
© AGS
According to the Arizona Geological Survey, 131 earthquakes were detected in 2011 compared with 53 in 2010. That was twice as many as in 2009 and about a third more than in 2008. Most of the earthquakes were in the northwestern part of the state. The Yuma area was also shaken by earthquakes associated with the Gulf of California Rift Zone.

Many of these earthquakes (magnitude ca. 1.6) occurred near Lake Mead. These are attributed to mining and quarrying, and also to crustal adjustments to water going into and out of the lake. The strongest earthquakes (magnitude ca. 3.6) occurred near Clarkdale in the central part of the state. The Survey says that these events are consistent with past behavior: "a propensity for deeper seismicity to occur in two pockets, the northwestern Utah-Arizona border and well within the Colorado Plateau in the northeast corner of the state" and "the highest concentration of energy release correlates well with the pattern of established Quaternary faulting, indicating that this portion of the crust continues to be an active area of strain release and of particular interest for hazard studies in Arizona." The strain is due to on-going crustal extension.

Bizarro Earth

USGS: Earthquake Magnitude 8.6 - Off West Coast of Sumatra

Image
© USGS
Date-Time:
Wednesday, April 11, 2012 at 08:38:37 UTC
Wednesday, April 11, 2012 at 02:38:37 PM at epicenter

Time of Earthquake in other Time Zones

Location:
2.311°N, 93.063°E

Depth:
22.9 km (14.2 miles)

Region:
OFF THE WEST COAST OF NORTHERN SUMATRA

Distances:
434 km (269 miles) SW of Banda Aceh, Sumatra, Indonesia

550 km (341 miles) SW of Lhokseumawe, Sumatra, Indonesia

963 km (598 miles) W of KUALA LUMPUR, Malaysia

1797 km (1116 miles) WNW of JAKARTA, Java, Indonesia

Bizarro Earth

8.9 Aceh quake triggers Indian Ocean tsunami warning

An earthquake with an initial magnitude of 8.9 has struck under the sea off Indonesia's northern Aceh province.

The quake triggered a tsunami warning across the Indian Ocean region.

The Pacific Tsunami Warning Center said it was not yet known whether a tsunami had been generated, but advised authorities to "take appropriate action".

The region is regularly hit by earthquakes. The Indian Ocean tsunami of 2004 killed 170,000 people in Aceh.

The US Geological Survey, which documents quakes worldwide, said the Aceh quake was centred 33km (20 miles) under the sea about 495km from Banda Aceh, the provincial capital.

It was initially reported as 8.9 magnitude but was later revised down to 8.7 by the USGS.

The tsunami warning said quakes of such a magnitude "have the potential to generate a widespread destructive tsunami that can affect coastlines across the entire Indian Ocean basin".

Bizarro Earth

What's Happening Under Gibraltar?

The Strait of Gibraltar
© ESAThe Strait of Gibraltar, which lies between the southern coast of Spain and the northern coast of Morocco, is the only place where water from the Atlantic Ocean mixes with water from the Mediterranean Sea.
The ground beneath Portugal, Spain and northern Morocco shook violently on Nov. 1, 1755, during what came to be known as the Great Lisbon Earthquake. With an estimated magnitude of 8.5 to 9.0, the temblor nearly destroyed the city of Lisbon and its lavish palaces, libraries and cathedrals. What wasn't leveled by the quake was mostly demolished in the ensuing tsunami and fires that raged for days. Altogether, at least 40,000 people were killed.

More than 250 years later, geologists are still piecing together the tectonic story behind that powerful earthquake. A unique subduction zone beneath Gibraltar, the southernmost tip of the Iberian Peninsula, now seems to be culprit. Subduction zones are the spots where one of Earth's tectonic plates dives beneath another, often producing some of the world's strongest earthquakes.

"At a global scale, subduction is the only process that produces magnitude-8 or -9 earthquakes," said Marc-Andre Gutscher, a geologist at the University of Brest in France. "If subduction occurred, and is still occurring here, then it's highly relevant to understanding the region's seismic hazards."

Bizarro Earth

Papua New Guinea - Earthquake Magnitude 6.2

PNG Quake_060412
© USGSEarthquake Location
Date-Time
Friday, April 06, 2012 at 16:15:55 UTC

Saturday, April 07, 2012 at 02:15:55 AM at epicenter

Time of Earthquake in other Time Zones

Location
4.534°S, 153.497°E

Depth
85.4 km (53.1 miles)

Region
NEW IRELAND REGION, PAPUA NEW GUINEA

Distances
52 km (32 miles) E of Taron, New Ireland, PNG

150 km (93 miles) ESE of Rabaul, New Britain, PNG

884 km (549 miles) NE of PORT MORESBY, Papua New Guinea

2543 km (1580 miles) N of BRISBANE, Queensland, Australia

Bizarro Earth

USGS: Earthquake Magnitude 6.3 - Oaxaca, Mexico

Image
© USGS
Date-Time:
Monday, April 02, 2012 at 17:36:43 UTC
Monday, April 02, 2012 at 12:36:43 PM at epicenter

Location:
16.477°N, 98.287°W

Depth:
12.3 km (7.6 miles)

Region:
OAXACA, MEXICO

Distances:
27 km (17 miles) SSE (148°) from Ometepec, Guerrero, Mexico

33 km (21 miles) WNW (302°) from Pinotepa Nacional, Oaxaca, Mexico

109 km (68 miles) SW (216°) from Tlaxiaco, Oaxaca, Mexico

176 km (109 miles) SE (133°) from Chilpancingo, Guerrero, Mexico

179 km (111 miles) ESE (103°) from Acapulco, Guerrero, Mexico