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Video simulations of earthquakes made available to world

Last Updated on Tuesday, 28 September 2010 12:10
Published on Thursday, 23 September 2010 13:51
A Princeton University-led research team has developed the capability to produce realistic movies of earthquakes based on complex computer simulations that can be made available worldwide within hours of a disastrous upheaval.

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A still from the simulation of the Peruvian earthquake of 22 September 2010. Credit: (c) Princeton University
The videos show waves of ground motion spreading out from an epicentre. In making them widely available, the team of computational seismologists and computer scientists aims to aid researchers working to improve understanding of earthquakes and develop better maps of the Earth's interior. The team describe the system and how the videos are created in a paper in the October 2010 edition of Geophysical Journal International.

"In our view, this could truly change seismic science," said Princeton's Jeroen Tromp, a professor of geosciences and applied and computational mathematics, who led the effort. "The better we understand what happens during earthquakes, the better prepared we can be. In addition, advances in understanding seismic waves can aid basic science efforts, helping us understand the underlying physics at work in the Earth's interior. These visualizations, we believe, will add greatly to the research effort.''

The movies will be made available for free to scientists, members of the public and news organizations interested in featuring such images on television and the Internet. The easily downloadable videos can be viewed at: http://global.shakemovie.princeton.edu. They tell the story in a language that is easy to understand, said Tromp, who also is the director of the Princeton Institute for Computational Science and Engineering (PICSciE).

When an earthquake takes place, data from seismograms measuring ground motion are collected by a worldwide network of more than 1,800 seismographic stations operated by members of the International Federation of Digital Seismograph Networks. The earthquake's location, depth and intensity are also determined. The ShakeMovie system at Princeton will now collect these recordings automatically using the Internet.

The scientists will input the recorded data into a computer model that creates a ''virtual earthquake''. The videos will incorporate both real data and computer simulations known as synthetic seismograms. These simulations fill the gaps between data collected on the actual ground motion recorded at specific locations in the region, providing a more complete view of the earthquake.

The animations rely on software that produces numerical simulations of seismic wave propagation in sedimentary basins. The software computes the motion of the Earth in three dimensions based on the actual earthquake recordings, as well as what is known about the subsurface structure of the region.

The shape of underground geological structures in the area not recorded on seismograms is key, Tromp said, as the structures can greatly affect wave motion by bending, speeding, slowing or simply reflecting energy. The simulations are created on a parallel processing computer cluster built and maintained by PICSciE and on a computer cluster located at the San Diego Supercomputing Centre.

After the three-dimensional simulations are computed, the software program plugs in data capturing surface motion, including displacement, velocity and acceleration, and maps it onto the topography of the region around the earthquake. The movies then are automatically published via the ShakeMovie portal. An email also is sent to subscribers, including researchers, news media and the public.

The simulations will be made available to scientists through the data management centre of the Incorporated Research Institutions for Seismology (IRIS) in Seattle. This organization distributes global scientific data to the seismological community via the Internet. Scientists can visit the IRIS website and download information. Due to the research team's work, they now will be able to directly compare actual and synthetic seismograms.

Advanced computing power made the synthetic seismograms possible, according to Dennis McRitchie, another author on the paper and a lead high-performance computing analyst for Princeton's Office of Information Technology. ''This is computationally intensive - it takes five hours to produce a 100-minute simulation,'' McRitchie said. The effort to numerically solve the differential equations that govern how the waves propagate through these complicated earth models requires 384 computers operating in parallel to analyze and process the numbers.

When an earthquake occurs, seismic waves are generated that propagate away from the fault rupture and course along the Earth's surface. The videos show the up-and-down motion of the waves in red (up) and blue (down). Strong red waves indicate rapid upward motion. Strong blue waves indicate the Earth's surface is moving quickly downward.

The simulation shows that the waves are of uneven strength in different areas, depending on the quality of the soil and the orientation of the earthquake fault line. When the waves pass through soft, sedimentary soils, they slow down and gain strength. Waves speed up through hard rock, lessening the impact on surface areas above. A clock in the video shows the time since the earthquake occurred.

CONTACTS

Kitta McPherson
Princeton University
Tel: +1 629 258 5729
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Dr Robert Massey
Royal Astronomical Society
Tel: +44 20 7734 3307 / 4582 x 214
Mob: +44 794 124 8035
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

FURTHER INFORMATION

The ShakeMovie portal showing earthquakes around the world is similar to one maintained at the California Institute of Technology that routinely does simulations of seismic events in the Southern California region. Earthquake movies will be available for download about 1.5 hours after the occurrence of a quake of magnitude 5.5 or greater.

The earthquake videos can be downloaded from http://global.shakemovie.princeton.edu

The work appears in "Near real-time simulations of global CMT earthquakes", Geophysical Journal International, vol. 183, issue 1, pp. 381-389.

In addition to Tromp and McRitchie, other Princeton scientists on the paper include Ebru Bozdag and Daniel Peter, postdoctoral fellows and Hejun Zhu, a graduate student, all in the Department of Geosciences. The development of the simulations also involved staff at PICSciE as well as Robert Knight, a lead high-performance computing analyst and others in Princeton's Office of Information Technology.

Other authors on the paper include: Dimitri Komatisch of the Universite de Pau et des Pays de L'Adour in Paris; Vala Hjorleifsdottir of Lamont-Doherty Earth Observatory of Columbia University, Qinya Liu of the University of Toronto, Paul Friberg of Instrumental Software Technologies in New York and Chad Trabant and Alex Hutko of IRIS.

The research was funded by the National Science Foundation.

NOTES FOR EDITORS

THE ROYAL ASTRONOMICAL SOCIETY

The Royal Astronomical Society (RAS www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings in Burlington House, its London HQ, and throughout the country, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities, and represents UK astronomy nationally and internationally. The Society is located at Burlington House, Piccadilly, London. Over 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories, as well as historians of astronomy and others.

GEOPHYSICAL JOURNAL INTERNATIONAL

Geophysical Journal International (GJI) is the primary solid-Earth geophysics journal based in Europe, publishing the results of research on the earth's internal structure, physical properties, evolution and processes covering all aspects of theoretical, computational and observational geophysics. GJI is jointly published by the RAS and the Deutsche Geophysikalische Gesellschaft (German Geophysical Society).