Featured Research

from universities, journals, and other organizations

Sea floor earthquake zones can act like a 'magnifying lens' strengthening tsunamis beyond what was through possible

Date:
March 7, 2013
Source:
University of Southern California
Summary:
Until now, it was largely believed that the maximum tsunami height onshore could not exceed the depth of the seafloor. But new research shows that when focusing occurs, that scaling relationship breaks down and flooding can be up to 50 percent deeper with waves that do not lose height as they get closer to shore.

The earthquake zones off of certain coasts -- like those of Japan and Java -- make them especially vulnerable to tsunamis, according to a new study. They can produce a focusing point that creates massive and devastating tsunamis that break the rules for how scientists used to think tsunamis work.
Credit: Zacarias da Mata / Fotolia

The earthquake zones off of certain coasts -- like those of Japan and Java -- make them especially vulnerable to tsunamis, according to a new study. They can produce a focusing point that creates massive and devastating tsunamis that break the rules for how scientists used to think tsunamis work.

Related Articles


Until now, it was largely believed that the maximum tsunami height onshore could not exceed the depth of the seafloor. But new research shows that when focusing occurs, that scaling relationship breaks down and flooding can be up to 50 percent deeper with waves that do not lose height as they get closer to shore.

"It is as if one used a giant magnifying lens to focus tsunami energy," said Utku Kanoglu, professor at the Middle East Technical University and senior author of the study. "Our results show that some shorelines with huge earthquake zones just offshore face a double whammy: not only they are exposed to the tsunamis, but under certain conditions, focusing amplifies these tsunamis far more than shoaling and produces devastating effects."

The team observed this effect both in Northern Japan, which was struck by the Tohoku tsunami of 2011, and in Central Java, which was struck by a tsunami in 2006.

"We are still trying to understand the implications," said Costas Synolakis, director of the Tsunami Research Center at the USC Viterbi School of Engineering and a co-author of the study. "But it is clear that our findings will make it easier to identify locales that are tsunami magnets, and thus help save lives in future events."

During an earthquake, sections of the sea floor lift up while others sink. This creates tsunamis that propagate trough-first in one direction and crest-first in the other. The researchers discovered that on the side of the earthquake zone where the wave propagates trough-first, there is a location where focusing occurs -- strengthening it before it hits the coastline with an unusual amount of energy that is not seen by the crest-first wave. Based on the shape, location, and size of the earthquake zone, that focal point can concentrate the tsunami's power right on to the coastline.

In addition, before this analysis, it was thought that tsunamis usually decrease in height continuously as they move away from where they are created and grow close to shore, just as wind waves do. The study's authors instead suggest that the crest of the tsunami remains fairly intact close to the source.

"While our study does not preclude that other factors may help tsunamis overgrow, we now know when to invoke exotic explanations for unusual devastation: only when the basic classic wave theory we use does not predict focusing, or if the focusing is not high enough to explain observations," said Vasily Titov, a researcher at NOAA's Pacific Marine Environmental Laboratory and study co-author.

Animation of a formation and focusing of a Tsunami: http://www.youtube.com/watch?v=BUS4dsBf8BI&feature=youtu.be


Story Source:

The above story is based on materials provided by University of Southern California. Note: Materials may be edited for content and length.


Journal Reference:

  1. U. Kanoglu, V. V. Titov, B. Aydin, C. Moore, T. S. Stefanakis, H. Zhou, M. Spillane, C. E. Synolakis. Focusing of long waves with finite crest over constant depth. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2013; 469 (2153): 20130015 DOI: 10.1098/rspa.2013.0015

Cite This Page:

University of Southern California. "Sea floor earthquake zones can act like a 'magnifying lens' strengthening tsunamis beyond what was through possible." ScienceDaily. ScienceDaily, 7 March 2013. <www.sciencedaily.com/releases/2013/03/130307124800.htm>.
University of Southern California. (2013, March 7). Sea floor earthquake zones can act like a 'magnifying lens' strengthening tsunamis beyond what was through possible. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2013/03/130307124800.htm
University of Southern California. "Sea floor earthquake zones can act like a 'magnifying lens' strengthening tsunamis beyond what was through possible." ScienceDaily. www.sciencedaily.com/releases/2013/03/130307124800.htm (accessed October 25, 2014).

Share This



More Earth & Climate News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins