Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Some deep-sea earthquakes send out early-warning signals, seismologists say

24.03.2005


Research published in Nature shows theoretical feasibility of quake forecasting



Earthquakes along a set of fault lines in the Pacific Ocean emit small "foreshocks" that can be used to forecast the main tremor, according to research in the March 24 issue of Nature. It is the first demonstration that some types of large imminent earthquakes may be systematically predictable on time scales of hours or less. Statistically reliable forecasting of imminent quakes has been an elusive goal for seismologists. Co-author Thomas Jordan, director of the Southern California Earthquake Center in the USC College of Letters, Arts and Sciences, stresses that quakes on land generally do not show many foreshocks and cannot be predicted with the methods outlined in the Nature paper.

The research team, led by Jeffrey McGuire of the Woods Hole Oceanographic Institution, studied past earthquakes along two so-called transform faults on the East Pacific Rise, where tectonic plates are spreading apart. Sensor data from the National Oceanic and Atmospheric Administration pinpointed the time and location of foreshocks and earthquakes. For the purposes of the study, the researchers defined a foreshock as any tremor of at least 2.5 magnitude on the Richter scale. Earthquakes were tremors of no less than 5.4 magnitude. The researchers then declared a hypothetical "alarm" for an hour within a 15-kilometer radius of the epicenter of every foreshock.


This retroactive and "naïve" early-warning system would have predicted six of the nine major earthquakes that occurred along the two faults between 1996 and 2001, researchers said. The finding suggests that short-term prediction – the ability to forecast an earthquake in the hours or minutes before it hits – may be feasible under certain circumstances. "This is the first demonstration of good short-term predictability for big earthquakes," Jordan said. "Some scientists believe that earthquakes come on suddenly with no warning signs, and the big ones are therefore unpredictable. In other parts of the oceans, they may be."

While any random guesser could have predicted six out of nine earthquakes by declaring enough alarms, the researchers’ system performed between 300 and 1,000 times better, Jordan said. And though the false-alarm rate was high, all false alarms taken together occupied only 0.15 percent of the total volume of space and time studied. The researchers believe they can improve both the accuracy and the lead-time of their forecasts. They hypothesize that both foreshocks and main tremors are caused by an earlier trigger event – possibly a slow, smooth sliding along the fault line that fails to generate seismic waves. Such an event – called an aseismic slow slip transient – may be detectable with the proper instruments, said Jordan, who points out that movement along the San Andreas fault is recorded by an extensive array of sensors.

"If you could do the same thing on the sea floor then you would probably see this thing coming," he said. Next year an oceanographic expedition led by McGuire will drop sensors along the East Pacific Rise to begin testing the researchers’ hypothesis. The possibility that slow slip transients may herald earthquakes has wider significance, researchers said. Slow slip transients have been detected in subduction zones, where one tectonic plate scrapes under another. The most powerful and dangerous earthquakes occur in subduction zones.

"The possibility that aseismic slip triggers large earthquakes on subduction megathrusts is especially intriguing given the observation that a slow slip transient occurred 15 minutes before the great 1960 Chilean megathrust earthquake," the authors wrote in Nature. "Notably, subduction zones are observed to have higher foreshock rates than continental regions." Still, Jordan said, the question of whether earthquakes on subduction zones are predictable systematically remains open and will require better observations.

Carl Marziali | EurekAlert!
Further information:
http://www.usc.edu

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>