February 10, 2012
3D Imaging Technology Could Help Multi-Fault Earthquake Preparations
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A team of U.S., Mexican, and Chinese geologists have used a new tool to help pinpoint the precise locations where earthquakes caused the planet's crust to rupture and alter the landscape, resulting in what they are calling the "most comprehensive before-and-after picture“¦ of an earthquake zone to date."
The 3D images, which were published in the February 10 issue of the journal Science, were captured from a 7.2. magnitude earthquake that occurred near Mexicali in northern Mexico on April 4, 2010, according to a February 9 University of California-Davis (UC-Davis) press release. Using light detection and ranging (LiDAR) equipment, the geologists were able to aerially scan approximately 140 square miles of terrain in under three days.
According to Rebecca Boyle of Popular Science, experts knew that the April 4 earthquake had "tore a 74-mile rupture through multiple faults in northern Baja California," but by using the high-resolution LiDAR technology and comparing existing maps of the region with the data gathered from the new images, "the researchers could see the where the Earth moved, and by how much. They even spotted new faults that had not been documented before."
"We can recognize their activity from how they disrupt the landscape, but we don't have a good way of assessing the potential size of earthquakes they produce, because they tend to rupture together with other, nearby faults in a complicated way," UC-Davis geologist and lead author Michael Oskin told Charles Q. Choi of OurAmazingPlanet on Thursday, adding that multi-fault earthquakes "can be especially dangerous if they occur near an urban area that is not well prepared."
Oskin and his colleagues worked alongside the National Center for Airborne Laser Mapping (NCALM) on the project, which involved flying over the area with their LiDAR equipment and bouncing a stream of laser pulses off the ground. The UC-Davis geologist said that they were already aware that the region they were studying had been mapped using similar technology by the Mexican government some four years earlier.
The researchers used a "virtual reality" facility at the university to analyze the data, comparing before and after photos from the location to determine what impact the earthquake had on the ground, the university said. By studying the deformation that occurred around seven small faults responsible for the seismic activity, they discovered how each of them played a role in causing the quake to occur.
"This gives new insight into how faults link together to produce large earthquakes, and how geologic structures incrementally grow these events -- for example, folding of rocks and growth of topography and basins around faults," Oskin told Choi. "We can immerse ourselves into the 3-D data set, down to the individual point measurements -- all 3.6 billion of them for the post-earthquake data set."
"We can learn so much about how earthquakes work by studying fresh fault ruptures," he added. "In this case, we have learned a great deal about how the rocks surrounding faults deform, which will give us better insight into how faults link together," which in turn could help scientists "develop better projections of how future, complex multi-fault ruptures may occur."
In addition to Oskin, UC-Davis graduate student Austin Elliott and researcher Peter Gold; J. Ramon Arrowsmith of Arizona State University; Alejandro Hinojosa Corona and J. Javier Gonzalez Garcia, CICESE in Mexico; Eric Fielding of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California; and Jing Liu-Zeng of the Chinese Academy of Sciences were all credited as authors of the study.
Image 2: This is a visualization of LiDAR data from the April, 2010 earthquake near Mexicali. Blue shows where ground surface moved down, red shows upward movement compared to the previous survey. Credit: Michael Oskin, UC Davis
On the Net:
- University of California-Davis
- National Center for Airborne Laser Mapping (NCALM)
- Arizona State University
- Jet Propulsion Laboratory (JPL)
- Chinese Academy of Sciences