Featured Research

from universities, journals, and other organizations

Earthquakes At Edges Of Tectonic Plates Can Trigger Second Earthquakes At Different Time And Place

Date:
February 4, 2008
Source:
Penn State
Summary:
Earthquakes occurring at the edges of tectonic plates can trigger events at a distance and much later in time. These doublet earthquakes may hold an underestimated hazard, but may also shed light on earthquake dynamics.

Earthquakes occurring at the edges of tectonic plates can trigger events at a distance and much later in time, according to a team of researchers reporting in the journal Nature on January 31. These doublet earthquakes may hold an underestimated hazard, but may also shed light on earthquake dynamics.

"The last great outer rise earthquakes that occurred were in the 1930s and 1970s," said Charles J. Ammon, associate professor of geoscience, Penn State. "We did not then have the equipment to record the details of those events." The outer rise is the region seaward of the deep-sea trench that marks the top of the plate boundary.

In late 2006 and early 2007, two large earthquakes occurred near Japan separated by about 60 days. These earthquakes took place in the area of the Kuril Islands that are located from the westernmost point of the Japanese Island of Hokkaido to the southern tip of the Kamchatka Peninsula. The first event took place on Nov. 15, 2006 when the edge of the Pacific plate thrust under the arc of the Kuril Islands, initiating a magnitude 8.3 event and causing some damage in Japan and a small tsunami that caused minor damage in Crescent City, California. About 60 days later, on Jan. 13, 2007, a magnitude 8.1 earthquake occurred in "the upper portion of the Pacific plate, producing one of the largest recorded shallow extensional earthquakes."

This second earthquake was not at a plate boundary and was not directly caused by subduction -- the moving of one plate beneath the other. Rather, it was a normal faulting event, where the Pacific plate stretched, bent and broke.

While Japan and the Kamchatka Peninsula are active earthquake areas, the region of the Kuril Islands where the large November earthquake occurred, had not had a large earthquake since 1915 and researchers are unsure of the exact nature of that event.

Working with Hiroo Kanamori, the John E. and Hazel S. Smits professor of geophysics, emeritus, California Institute of Technology, and Thorne Lay, professor of Earth & planetary sciences, University of California, Santa Cruz, the Penn State researcher looked at the sequence of seismic activity that link these two earthquakes into a doublet.

"Such large doublet earthquakes, though rare, could be an underestimated hazard," says Ammon. "We are also interested in what these events tell us about how earthquakes interact, how the stresses and interactions allow one earthquake to trigger another."

Looking at the seismic record, the researchers found a series of smaller, foreshock earthquakes beginning about 45 days before Nov. 15. On Nov. 15, there was the magnitude 8.3 earthquake on the plate boundary, the largest event of 2006.

"Within minutes of the Nov. 15 earthquake, seismic activity began on the Pacific plate in the area where the January earthquake would take place," says Ammon. "This large second earthquake generated a larger amplitude of shaking in the frequency range that affects human-made structures than the first earthquake."

Usually, aftershocks from a large earthquake are at least one order of magnitude less than the main event and taper off rapidly. In this case, the events within the Pacific plate east of the plate boundary did not taper off, and the second event that occurred in January was about the same size as the first earthquake.

Earthquakes at plate boundaries in subduction zones occur when the plate that is going under -- being subducted -- gets temporarily stuck and causes compression in the plate away from the edge. Tension builds and when the plate overcomes the friction holding it, it moves downward, slipping under the top plate and causing an earthquake. According to the researchers, the second earthquake that occurred on the Pacific plate happened because of bending experienced by the pacific plate that occurs before it subducts beneath the upper plate. As the front edge of the plate slipped, the plate east of the November earthquake bent, cracked and broke in January.

Like pie crust, when the Earth's crust bends, small cracks begin to appear -- these were the small shocks that began immediately after the first earthquake -- but when the bending becomes severe, a larger region of the crust breaks -- creating the second, very large event.

In the United States, subduction zones exist only in the Pacific Northwest, Alaska and the area around Puerto Rico. The researchers note, "Triggering of a large outer rise rupture with strong high-frequency shaking constitutes an important potential seismic hazard that needs to be considered in other regions."

The National Science Foundation and the U.S. Geological Survey funded this research.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Earthquakes At Edges Of Tectonic Plates Can Trigger Second Earthquakes At Different Time And Place." ScienceDaily. ScienceDaily, 4 February 2008. <www.sciencedaily.com/releases/2008/01/080130130636.htm>.
Penn State. (2008, February 4). Earthquakes At Edges Of Tectonic Plates Can Trigger Second Earthquakes At Different Time And Place. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2008/01/080130130636.htm
Penn State. "Earthquakes At Edges Of Tectonic Plates Can Trigger Second Earthquakes At Different Time And Place." ScienceDaily. www.sciencedaily.com/releases/2008/01/080130130636.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Higgins Breaks Record at Mt. Washington

Higgins Breaks Record at Mt. Washington

Driving Sports (July 24, 2014) Subaru Rally Team USA drivers David Higgins and Travis Pastrana face off against a global contingent of racers at the annual Mt. Washington Hillclimb in New Hampshire. Includes exclusive in-car footage from Higgins' record attempt. Video provided by Driving Sports
Powered by NewsLook.com
Storm Kills Three, Injures 20 at Virginia Campground

Storm Kills Three, Injures 20 at Virginia Campground

Reuters - US Online Video (July 24, 2014) A likely tornado tears through an eastern Virginia campground, killing three and injuring at least 20. Linda So reports. Video provided by Reuters
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:
from the past week

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