Latest quake triggered by Dec. 26 mega-shock
Latest quake triggered by Dec. 26 mega-shock
Michael Perry, Reuters/Sydney
A huge undersea earthquake that killed hundreds in Indonesia overnight was a result of increased geological stress caused by last December's mega-quake that sent a devastating tsunami across southern Asia, seismologists said.
And they warned of a third big earthquake in the area sooner or later.
Monday night's 8.7 magnitude shock was centered 160 km southeast of the epicenter of the 9.0 magnitude Dec. 26 quake off Sumatra's northern tip. Geoscience Australia said the earlier quake was two to four times larger.
Like the 2004 tremor, the latest one was a vertical earthquake where part of the ocean floor was thrust upwards by another tectonic plate pushing beneath it.
"It appears to be the same plate boundary where the Australian plate is slipping beneath the Sumatran (Sunda) plate," Geoscience Australia seismologist Phil Cummins told Reuters.
Seismologists had been warning of a second earthquake off Sumatra due to the increased geological stress caused by last December's quake.
Indonesia's disaster center said around 1,000 people had been killed on the island of Nias, off Sumatra's west coast, which took the full fury of the latest quake, one of the eight biggest in the world since 1900. The country's vice president said on Monday morning that the toll could reach 2,000.
Cummins said a third earthquake was to be expected because geological stress levels would rise further following the latest tremor.
"There is a chance that the next segment further to the southeast could rupture sooner than we expected," he said.
"But we can't predict the time. Rather than 100 years it might be 20 or 50 years," he said, but added it was possible it could be in the next three months.
Last December's quake generated a tsunami that hit 13 Indian Ocean nations, leaving more than 288,000 dead or missing.
The U.S. Geological Survey reported that Monday's quake was located 2.065 degrees north and 97.010 degrees east. The Dec. 26 quake was located 3.307 degrees north and 95.947 east.
Both quakes were shallow, at a depth of 30 km, which heightened the chances of a tsunami.
Australia's remote Cocos Islands in the Indian Ocean recorded a tiny tsunami on Tuesday, with a 10-cm wave followed by a 25 cm wave. Cocos recorded a 33-cm wave after the Dec. 26 quake.
Hawaii's Pacific Tsunami Warning Center, which issued and then canceled a tsunami warning after Monday's quake, said early warning systems put in place since December had worked.
"The international effort paid off. It all went smoothly," said the center's Dave Burwell.
Burwell said the center contacted a network of meteorological and geoscience offices in Asia who then alerted local communities to the tsunami warning.
The U.S. Geological Survey report on the latest earthquake also said it was "likely triggered by stress changes caused by the December 2004 earthquake".
Before that disaster, the previous quake of above magnitude 8 in this area occurred in 1861.