Why Philippines Earthquake Tsunami Warning Was Cancelled

The large earthquake that struck off the eastern coast of the Philippines today (Aug. 31) at 8:47 p.m. local time sparked tsunami warnings across a large swath of the neighboring Pacific region, yet those warnings were canceled not long after.

The magnitude-7.6 earthquake hit about 58 miles (63 kilometers) from shore along a tectonic boundary known as a subduction zone, where an oceanic plate is diving beneath a continental plate.

Earlier reports put the quake's magnitude at 7.9, but after more data from global networks of seismometers arrived, officials at the U.S. Geological Survey downgraded the magnitude to 7.6.

"There's a significant difference, but they're both really big earthquakes that can generate tsunamis, and if they occur on land they can kill lots of people," said Paul Caruso, a geophysicist with the U.S. Geological Survey in Golden, Colo.

In this case, the oceanic Philippine plate shoved deeper below the Sunda plate, a continental plate home to the Philippines, and portions of Indonesia, Malaysia, Thailand and Vietnam.

The quake ruptured at a depth of about 22 miles (35 km). That's fairly shallow, Caruso said, and shallower earthquakes are more likely to cause tsunamis.

"When you get a really deep quake, a lot of the energy is absorbed before it reaches the seafloor, and what causes a tsunami is the seafloor being pushed up," he told OurAmazingPlanet.

However, tsunami warnings that were in effect for the Philippines, Indonesia and Belau were cancelled by the Pacific Tsunami Warning Center in Hawaii at around 11 a.m. ET.

So-called subduction quakes — those that occur when an oceanic plate suddenly jolts deeper beneath a continental plate — are the most powerful type of earthquakes that occur on our planet.

They're also very good at shoving the seafloor, and the sheer area of the seafloor that is thrust upward — the length of the rupture, and its horizontal and vertical displacement —  determines the size of the tsunami that follows.

Data from sensors in the ocean near the site of the quake indicate a tsunami was generated, and waves are coming between 10 and 14 minutes apart, but it appears the waves aren't packing so much energy that they'll take a significant toll once they reach land.

In deep water, tsunami waves appear small, and only reach a massive size once they make it into shallower waters close to shore.

So, although today's quake was a significant one, it appears it didn't move the seafloor enough to cause a large tsunami.

However, Caruso warned that earthquakes can also trigger undersea landslides, which can, in turn, cause tsunamis.

It appears the earthquake has caused at least one death after a house collapsed, and Philippine authorities are warning residents to remain vigilant, in case any further earthquakes occur, the AP reported.

The tectonic region that ruptured today has a long history of shallow, strong earthquakes.

Reach Andrea Mustain at amustain@techmedianetwork.com, or follow her on Twitter @AndreaMustainFollow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook & Google+.

Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Loading...

Editor’s note:Yahoo Philippines encourages responsible comments that add dimension to the discussion. No bashing or hate speech, please. You can express your opinion without slamming others or making derogatory remarks.

  • Aquino appeals to Indonesia one more time to keep Filipina alive
    Aquino appeals to Indonesia one more time to keep Filipina alive

    Philippine President Benigno Aquino said he made one last appeal to the Indonesian government to spare a Filipina among nine prisoners set to be executed for drug trafficking on Tuesday as she could be a vital witness in prosecuting drug syndicates. It was Aquino's third personal appeal, after the Indonesian attorney general rejected the Philippines' request on Monday for a second judicial review of the case of Mary Jane Veloso, who her lawyers say merely served as an unknowing mule to drug …

  • Cheapest motorcycles in the Philippines under PhP 40,000
    Cheapest motorcycles in the Philippines under PhP 40,000

    Are you hunting for an affordable motorcycle which you can use for personal use or a family service vehicle? Carmudi PH presents to you some of the cheapest motorcycles in the Philippines today. These budget friendly motorbikes will surely not hurt your pockets, and you may even buy them on the spot instead of monthly […] The post Cheapest motorcycles in the Philippines under PhP 40,000 appeared first on Carmudi Philippines. …

  • Indonesia gears up for executions as families wail in grief
    Indonesia gears up for executions as families wail in grief

    Indonesia made final preparations Tuesday to execute eight foreigners by firing squad, as family members wailed in grief during last visits to their loved ones and ambulances carrying white coffins arrived at the drug convicts' prison. Relatives of Myuran Sukumaran and Andrew Chan, the Australian ringleaders of the so-called "Bali Nine" heroin trafficking group, arrived at Nusakambangan prison calling for mercy for their loved ones, with Sukumaran's sister collapsing in grief. They are among …

  • Labor Day heat index may heat feverish levels

    Temperatures could soar on Labor Day this Friday, with the "init factor" reaching the 40°C level in some areas of the country. Labor Day is a holiday in the Philippines, though many Filipinos are expected to go out to the streets to call for better working conditions. The so-called "init factor" or "heat index" gives the apparent temperature, taking into account the actual air temperature as well as other factors such as humidity. State weather agency PAGASA's Tuesday heat index indicated …

  • How Indonesia executes death row inmates
    How Indonesia executes death row inmates

    Indonesia is expected to soon execute by firing squad a group of nine convicts, most of them foreigners, for drug offences on the prison island of Nusakambangan in Central Java. The executions, which will be the second round under President Joko Widodo, have drawn international criticism and sparked diplomatic tensions with Australia, the Philippines, Nigeria and Brazil, which have nationals on death row. The group also includes a citizen from Indonesia. Recruits for the firing squad are …

  • Nine await mass execution in Indonesia, as foreign hopes for reprieve fade
    Nine await mass execution in Indonesia, as foreign hopes for reprieve fade

    By Kanupriya Kapoor CILACAP, Indonesia (Reuters) - Nine drug traffickers met their families for what could be the final time at an Indonesian maximum security prison on Tuesday, after Jakarta rejected international pleas for clemency and ordered their mass execution to proceed, possibly within hours. The death penalties imposed on eight foreigners and an Indonesian have been condemned by the United Nations, and strained ties between neighbours Australia and Indonesia. "We're hoping for a …

  • Isuzu PH announces new President
    Isuzu PH announces new President

    Isuzu Philippines Corporation (IPC) formally announced the appointment of Hajime Koso as the new president replacing outgoing president Nobuo Izumina, who will be assigned as the Director of Isuzu Body Corporation, an affiliate of Isuzu Motors Limited (IML) in Japan. A native of Okayama Japan, the 57 years old executive has been working for IML for 35 […] The post Isuzu PH announces new President appeared first on Carmudi Philippines. …

  • Pacquiao sees fist of God delivering win over Mayweather
    Pacquiao sees fist of God delivering win over Mayweather

    Filipino boxing hero Manny Pacquiao is confident he can beat American arch-rival Floyd Mayweather in Las Vegas on Saturday with the power of God, after abandoning a life he said was packed with sin condemning him to hell. Pacquiao is in top form both in mind and spirit after he traded his boozing, gambling and womanising ways for a devout life of prayer, his spiritual adviser, Jeric Soriano, told AFP in a recent Manila interview. Except the world got to him," Soriano said of Pacquiao's …

POLL

Should Aquino be held accountable over the Mamasapano operations?

Loading...
Poll Choice Options