Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Japan Earthquake Appears to Increase Quake Risk Elsewhere in the Country

26.05.2011
Japan’s recent magnitude 9.0 earthquake, which triggered a devastating tsunami, relieved stress along part of the quake fault but also has contributed to the build up of stress in other areas, putting some of the country at risk for up to years of sizeable aftershocks and perhaps new main shocks, scientists say.

After studying data from Japan’s extensive seismic network, researchers from the Woods Hole Oceanographic Institution (WHOI), Kyoto University and the U.S. Geological Survey (USGS) have identified several areas at risk from the quake, Japan’s largest ever, which already has triggered a large number of aftershocks.


Map showing the 11 March 2011 magnitude 9.0 off Tohoku mainshock and 166 aftershocks of magnitude 5.5 and greater until May 20. Warmer color indicates more recent events. Larger symbol indicates greater quake magnitude.
(Modified from figure created by the U.S. Geological Survey)

Data from the magnitude 9.0 Tohoku earthquake on March 11 has brought scientists a small but perceptible step closer to a better assessment of future seismic risk in specific regions, said Shinji Toda of Kyoto University, a lead author of the study. “Even though we cannot forecast precisely, we can explain the mechanisms involved in such quakes to the public,” he said. Still, he added, the findings do bring scientists “a little bit closer” to being able to forecast aftershocks.

“Research over the past two decades has shown that earthquakes interact in ways never before imagined,” Toda, Jian Lin of WHOI and Ross S. Stein of USGS write in a summary of their paper in press for publication in the Tohoku Earthquake Special Issue of the journal Earth, Planets and Space. “A major shock does relieve stress—and thus the likelihood of a second major tremor—but only in some areas. The probability of a succeeding earthquake adjacent to the section of the fault that ruptured or on a nearby but different fault can jump” significantly.

The Tohoku earthquake, centered off northern Honshu Island, provided an “unprecedented” opportunity to utilize Japan’s “superb monitoring networks” to gather data on the quake, the scientists said. The Tohoku quake, the fourth largest earthquake ever recorded, was “the best-recorded [large quake] the world has ever known.”

This made the quake a “special” one in terms of scientific investigation, Lin said. “We felt we might be able to find something we didn’t see before” in previous quakes, he said.

The magnitude 9 quake appears to have influenced large portions of Honshu Island, Toda said. At particular risk, he said, are the Tokyo area, Mount Fuji and central Honshu including Nagano.

The Kantu fragment, which is close to Tokyo, also experienced an increase in stress. Previous government estimates have put Tokyo at a 70 percent risk for a magnitude 7 earthquake over the next 30 years. The new data from the Tohoku quake increase those odds to “more than 70 percent,” Toda said. “That is really high.”

Using a model known as Coulomb stress triggering, Lin and his colleagues found measureable increases in stress along faults to the north at Sanriku-Hokobu, south at Off Boso and at the Outer Trench Slope normal faults east of the quake’s epicenter off the Japan coast near the city of Sendai.

“Based on our other studies, these stress increases are large enough to increase the likelihood of triggering significant aftershocks or subsequent mainshocks,” the researchers said.

Stein of the USGS emphasized the ongoing risk to parts of Japan. “There remains a lot of real estate in Japan--on shore and off--that could host large, late aftershocks of the Tohoku quake,” he said.

“In addition to the megathrust surface to the north or south of the March 11 rupture, we calculate that several fault systems closer to Tokyo have been brought closer to failure, and some of these have lit up in small earthquakes since March 11. So, in our judgment, Central Japan, and Tokyo in particular, is headed for a long vigil that will not end anytime soon.”

Lin added that aftershocks, as well as new mainshocks, could continue for “weeks, months, years.”

Toda explained that the magnitude of future quakes is proportional to the length of the fault involved.

In a separate paper submitted to Geophysical Research Letters, the researchers “report on a broad and unprecedented increase in seismicity rate for microearthquakes over a broad (360 by 120 mile) area across inland Japan, parts of the Japan Sea and the Izu islands, following the 9.0 Tohoku mainshock.”

“The crust on the land was turned on…far away from a fault,” Lin said. Most of these are relatively small quakes—magnitude 2 to 4—“but a lot of them,” Lin said. “This is surprising; we’ve never seen this before,” he said. “Such small events…may have happened following major quakes in other places but may have been missed due to poor seismic networks.”

“The 9.0 Tohoku quake caught many people including scientists by surprise,” Lin said. “It had been thought that a large quake in this area would go up to about 8.2, not 9.0” That estimate was significantly influenced by historical data. “The Tohoku quake reminded us that considering only the historical earthquakes is inadequate, even in a country of relatively long written records like Japan and China,” he said.

“Historical records, and especially the instrumental records, are indeed too short to provide a full picture of the potential of large earthquakes in a region. Thus we must encourage many more studies to find geological evidence (for example, through analyzing sediment cores extracted on land and undersea) that might provide clues of large earthquake and tsunami events that occurred hundreds to thousands of years ago.”

“We must recognize that because our knowledge is incomplete, our estimation of seismic hazard is likely to be underestimated in many cases. Thus we must prepare for potential hazard that might be worse than we already know,” Lin said.

The finding that a quake such as this one can increase stresses elsewhere “means that new quakes could occur in the region,” Lin said. “We must factor in this new information on stresses into earthquake preparedness.”

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment.

Media Relations | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>