Temblors jolt Papua, Babuyan, Tonga isles
First posted 03:06am (Mla time) May 29, 2006
Inquirer
Philippine Daily InquirerEditor's Note: Published on page A1 of the May 29, 2006 issue of the Philippine Daily Inquirer
JAKARTA -- The Pacific’s volatile “Ring of Fire” yesterday unleashed three more earthquakes, a day after a temblor in Indonesia left more than 4,300 dead in one of the world’s most seismically active regions.
The quakes shook the South Pacific nations of Papua New Guinea and Tonga less than half an hour of each other on Sunday morning.
A third temblor rattled the Babuyan islands at 5 p.m. in northern Luzon.
Although the quakes in Papua New Guinea and Tonga were as powerful as that which hit the central Indonesian island of Java, there were no reports of deaths or subsequent tsunamis.
The first quake, with a magnitude of 6.2, struck 189 km off the coast of New Britain, an island off Papua New Guinea’s northeast coast, at 1:12 p.m. (0312 GMT).
The second quake hit the coast of Tonga, about 4,000 km and several time zones away, at 4:36 p.m. (0336 GMT). The US Geological Survey recorded that quake at a magnitude of 6.7.
Barry Hirshorn, a geophysicist with Hawaii’s Pacific Tsunami Warning Center, said the two quakes posed no risk of a Pacific-wide tsunami and were unlikely to be related.
“They’re probably unrelated, they just happened at the same time,” Hirshorn said.
Another geophysicist at the center, Victor Sardina, said he believed the earthquakes were unrelated to the magnitude-6.3 quake that leveled hundreds of buildings and killed thousands of people on the central Indonesian island of Java on Saturday.
“Sometimes, where there is a big earthquake in one area ... it might upset the tectonic activity in other areas, but not necessarily,” Sardina said.
“For that, we’d have to analyze a whole lot of archive data to see a certain pattern in terms of seismic activity,” he added. “I don’t think they’re related.”
Calls to Papua New Guinea’s National Disaster Center went unanswered on Sunday, and details on injuries or damage were not immediately available.
Police in Tonga’s capital, Nuku’alofa, and in the Ha’apai Islands group capital of Pangai to the north, reported no serious injuries or damage.
“Yes, we felt it,” said Constable Mosese Latu in Pangai, which was near the epicenter.
“There are no damage reports and no injuries -- everything’s fine,” Latu told The Associated Press in a telephone interview.
In Nuku’alofa, publisher Mary Fonua said the quake was short but sharp.
“We definitely felt it and we went running outside the moment it struck because it was a significant jolt,” Fonua said.
Ring of Fire
Papua New Guinea, Tonga and Indonesia are part of the Pacific “Ring of Fire” where earthquakes and volcanic activity are frequent.
Experts believe the activity in the earth’s crust over the past two days -- including the awakening of the Mount Merapi volcano near the epicenter of Saturday’s quake -- was linked to the Ring of Fire.
“There’s no doubt they are effects of the same cause -- the ring of weakness in the earth’s surface,” said Gary Gibson, professor of seismology at RMIT University in Melbourne, Australia.
The Ring of Fire, which stretches along the western coast of the Americas through the island nations of the South Pacific and on through Southeast Asia, is a series of fault lines -- or weaknesses -- in the hardened upper layers of the earth’s surface, known as the crust.
These lines of weakness are the meeting points of huge continental plates that make up the crust and which literally float on the molten rock of the earth’s core.
These plates are in constant motion, clashing with each other or moving away from each other, creating stresses and pressure buildups at their margins.
This stress is released through volcanic eruptions, when the molten rock is ejected as magma through fissures in the crust, or via earthquakes, when the pressure causes the crust to buckle and shift.
Most of these seismic events are small and occur under the sea, where the majority of the continental plate margins are found.
But occasionally they generate volcanic explosions, earthquakes or landslides.
According to the US Geological Survey (USGS), an average of 19.4 quakes of 7.0-plus strength occur on the Ring of Fire each year. Indonesia has suffered from three catastrophic earthquakes in the past 18 months.
On Dec. 26, 2004, the 9.3-magnitude quake unleashed tsunamis that crashed into Indian Ocean shorelines and killed 168,000 people in Indonesia’s Aceh province alone.
Six hundred people were killed in an 8.7-quake just 160 km to the south on March 28, 2005.
Comparatively small
Gibson said that the flurry of seismic activity of the past days was comparatively small.
“On any given day you would find seismic activity greater than this throughout the Pacific region,” he said.
“Last week, there was a sequence of earthquakes between New Zealand and Tonga that were far greater -- we got up to magnitude of 7.8 on one day,” he said. “But nobody knows anything about it because it didn’t affect anybody.”
Although this activity is the result of the weak points in the earth’s surface, experts are not convinced that they create a ripple, or domino, effect of one quake setting off another.
“Earthquakes do tend to happen in clusters but they aren’t triggered by one another,” he said.
“The seismic wave created by an earthquake can travel for hundreds of kilometers and then dissipate. The earth’s crust is actually very good at absorbing that energy. Reports from Agence France-Presse and Associated Press