Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New analysis of earthquake zone raises questions

27.08.2008
Oregon State University scientists have completed a new analysis of an earthquake fault line that extends some 200 miles off the southern and central Oregon coast that they say is more active than the San Andreas Fault in California.

The Blanco Transform Fault Zone likely won't produce the huge earthquake many have predicted for the Pacific Northwest because it isn't a subduction zone fault.

But the scientists say an earthquake of magnitude 6.5 to 7.0 is possible, if not probable in the near future, and their analysis suggests that the region may be under some tectonic stress that potentially could affect the Cascadia Subduction Zone.

Results of the study were just published in the Journal of Geophysical Research.

During the past 40 years, there have been some 1,500 earthquakes of magnitude 4.0 or greater along the Blanco Transform Fault Zone, and many thousands of smaller quakes. The Blanco fault is the boundary between the Juan de Fuca and the Pacific plates. As the Juan de Fuca plate moves to the east, it is subducted beneath the North American plate at the rate of about 1.5 inches per year. But as it moves, it must break free of the adjacent Pacific plate.

This slippage causes the numerous earthquakes, according to John Nabelek, an associate professor in OSU's College of Oceanic and Atmospheric Sciences and one of the authors of the study. When the earthquakes that relieve stress do not account for predicted motion rates, he added, it raises questions.

"The eastern portion of the fault has moved at a predictable rate and the earthquake activity associated with it has been what we would expect," Nabelek said. "But the western part of the fault has been lagging in terms of the number and size of earthquakes. It seems to be straining, absorbing the motion.

"It could mean that the fault is getting ready for a large earthquake, or it could mean that the movement has been so gradual that we couldn't detect it," he added.

The OSU study is important because the Blanco Transform Fault has become the most intensely studied ocean transform fault in the world. Its close proximity to the Oregon coastline puts it within reach of land-based seismographs that can detect moderate ocean earthquakes. Another key is the research done at OSU's Hatfield Marine Science Center, where marine geologist Bob Dziak monitors undersea seismic activity using a hydrophone system deployed by the U.S. Navy.

In April of this year, Dziak reported on a swarm of 600 earthquakes in 10 days in this region, including magnitude 5.4 and 5.0 events.

"Land stations also detected a four-fold increase in the number of earthquakes along the Blanco fault in 2008 compared to background rates," Nabelek said, "with the largest anomaly in the enigmatic western part."

Jochen Braunmiller, a research associate in OSU's College of Oceanic and Atmospheric Sciences and lead author on the paper, says land-based seismographs can detect earthquakes of 4.0 or greater along the Blanco fault, and the ocean hydrophones monitored by Dziak can pick up quakes down to a magnitude of 3.0 and sometimes smaller, depending on location.

"Our monitoring may be missing a lot of earthquakes that are less than 3.0," Braunmiller said. "The western side of the fault may be experiencing a series of mini-quakes that we can't detect, or it could be slowing creeping along in a way we cannot measure.

"But we can't discount the possibility that its energy hasn't been released and it will some day in the form of a good-sized earthquake," Braunmiller added.

The risk of a major tsunami from an earthquake in this transform fault is slim, the scientists point out, because the plates move sideways past each other. "You need quite a bit of vertical displacement on the ocean floor to generate a tsunami," Braunmiller said, "and earthquakes along the Blanco fault don't generate it."

The Blanco Transform Fault Zone begins at a point about 100 miles off of Cape Blanco, south of Bandon, Ore., and extends in a northwest direction to a point about 300 miles off of Newport. Of all the world's ocean transform faults – or those that lie between tectonic plates – it is the closest to shore and can be monitored more readily by land-based seismographs.

Northwest scientists have approximately 60 such land-based seismographs deployed from British Columbia to California that can pick up moderate offshore quakes.

"Between the land-based network, the hydrophones and other instruments, the threshold of detection for earthquakes has definitely lowered over the past 20 years," Nabelek said. "But we still can't tell whether the western part of the fault has thousands, or even millions of infinitesimal slips – or it is building up to a major earthquake."

John Nabelek | EurekAlert!
Further information:
http://www.oregonstate.edu

More articles from Earth Sciences:

nachricht New plate adds plot twist to ancient tectonic tale
15.08.2017 | Rice University

nachricht Global warming will leave different fingerprints on global subtropical anticyclones
14.08.2017 | Institute of Atmospheric Physics, Chinese Academy of Sciences

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

Im Focus: Scientists improve forecast of increasing hazard on Ecuadorian volcano

Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).

The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New thruster design increases efficiency for future spaceflight

16.08.2017 | Physics and Astronomy

Transporting spin: A graphene and boron nitride heterostructure creates large spin signals

16.08.2017 | Materials Sciences

A new method for the 3-D printing of living tissues

16.08.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>