Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Prelude to an Earthquake?


Berkeley Lab Scientist Studies Possible Precursors in Micro-quakes

A Berkeley Lab scientist has identified possible precursors to two recent California earthquakes.

A geophysicist from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has identified possible seismic precursors to two recent California earthquakes, including the 1989 Loma Prieta earthquake that wreaked havoc throughout the Bay Area.

After sifting through seismic data from the two quakes, Valeri Korneev found a spike in the number of micro-earthquakes followed by a period of relative calm in the crust surrounding the quakes’ epicenters — months before the quakes occurred. Although more work needs to be conducted to determine whether other large quakes are foreshadowed by a similar rise and subsequent decline in small-magnitude tremors, Korneev’s analysis suggests that these peaks may be indicative of the total set of geological stresses that affect the timing and location of large earthquakes. Understanding this total stress picture may eventually make it be possible to predict destructive earthquakes within a much shorter time frame than currently possible.

“Peaks in seismic activity in the crust surrounding a fault could help signal the arrival of large earthquakes,” says Korneev of Berkeley Lab’s Earth Sciences Division. “These peaks may be a good mid-term precursor and allow authorities to declare alerts several months before earthquakes.”

He will present his research Dec. 9 at the American Geophysical Union’s Fall meeting in San Francisco.

Predicting the location and date of impending earthquakes has so far remained elusive. Instead, scientists rely on earthquake forecasts, which are statistical tools that offer the probability of a quake occurring within a certain time frame. These forecasts are largely based on the seismic history of known fault lines. For example, the U.S. Geological Survey’s official seismic risk assessment gives a 27 percent chance that a magnitude 7.0 earthquake will occur on the Bay Area’s Hayward Fault sometime in the next 30 years.

“Such long-term statistical forecasts, though useful to government planners, are not effective for taking near-term, damage-minimizing action,” says Korneev. “We are not able to stay alert every day.”

But the prospect of more precise predictions has been hindered by a lack of detectable changes in a fault’s behavior prior to a quake. It’s as if some destructive earthquakes occur out of the blue, completely unannounced.

Then, in 2004, a magnitude 6.0 quake rattled the town of Parkfield, California, also known as the seismology capital of the world. Here, where the San Andreas Fault cuts through central California, a magnitude 6.0 quake has occurred roughly every 22 years for about the last 100 years. The 2004 quake happened after a 38-year lull, and geologists were ready with an extensive network of instruments and boreholes that record every seismic hiccup in the area.

Soon after the quake, scientists pored over the network’s data to determine if the San Andreas Fault had dropped any clues that a quake was imminent. The first reports failed to find anything unusual. The few years preceding the quake were marked by the San Andreas Fault’s typical restlessness. There was no ominous build-up or calm before the storm, just a steady stream of normal data.

Korneev, however, decided to exclude from his analysis those tremors that occurred directly along the narrow portion of the San Andreas Fault that ruptured during the quake. Instead, he only included seismic activity that occurred along the fault’s flanks. According to Korneev, earthquakes directly within the creeping or moving portion of the fault zone were excluded because they manifest stress-release processes rather than stress accumulation.

Minus the data from the fault-zone quakes, his new analysis revealed a possible harbinger. He found a sharp increase in seismic activity that started one year before the 2004 quake and peaked four to six months before the quake. This spike was followed by a steady decrease in activity during the last few months leading up to the quake.

Inspired by this discovery, Korneev conducted a similar analysis of the seismic activity that preceded the 1989 magnitude 7.0 Loma Prieta earthquake, which was also sparked when a portion of the San Andreas Fault shifted. He focused his attention on the area to the west of Hayward Fault zone and the other seismically active areas adjacent to the epicenter. In the two months prior to the Oct. 17 quake, seismic activity increased to about eight times above normal levels. This peak was followed by a decrease in activity leading up to the powerful earthquake.

Korneev interprets the observed increase in seismic activity prior to the large quakes as a signature of the escalating stress level in the surrounding crust. He attributes the peak and subsequent reduction in seismic activity to damage-induced rock softening processes.

“Peaks in seismicity occurring several months before two recent large San Andreas Fault quakes indicate that they are good candidates for earthquake prediction studies,” says Korneev. “The precursor is an increase in small magnitude earthquakes in the crust surrounding the impending quake’s epicenter. This could give seismologists a clue as to what to look for when monitoring fault zones.”

In the future, Korneev would like to determine whether other well-studied large earthquakes in California were also prefaced by this phenomenon, which he calls microseismic emission precursors. He would also like to begin monitoring the seismic activity surrounding the Hayward Fault in California, which is due for a major earthquake.

Data processing for this research was conducted at Berkeley Lab’s Center for Computational Seismology.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

Dan Krotz | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

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

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>