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Miami part of EarthScope: Continental scale seismic observatory
Miami University has joined the continent-wide EarthScope project with the recent installation of an EarthScope Transportable Array seismic station at the Ecology Research Center. EarthScope was recently selected by Popular Science magazine as Number One in Popular Science’s “Big Science: The Universe’s Top Ten Most Epic Science Projects,” even ahead of the international space station.
EarthScope is a National Science Foundation (NSF) program to study the structure and evolution of the North American continent by installing hundreds of ultra-sensitive seismometers, GPS stations and other scientific instruments across the United States.
Michael Brudzinski, associate professor of geology and environmental earth science, has been involved with EarthScope since it began in 2004. Among other projects, Brudzinski organized the efforts to identify where the EarthScope Transportable Array seismic stations will be placed in Ohio. He also has a host of students and research projects using data generated from EarthScope stations.
The Transportable Array (USArray), one component of EarthScope, is a network of 400 high-quality broadband seismographs that are being placed in temporary sites across the conterminous United States from west to east, and Alaska, in a regular grid pattern. After a residence time of two years, each instrument is picked up and “leap frogs” to the next location to the east.
“EarthScope’s Transportable Array is an unparalleled achievement in seismic recording and is providing new insight into how the Earth shakes and shimmies,” explained Brudzinski.
To see an animation of USArray seismic wave visualizations, click here.
Miami Research Projects
Brudzinski and his lab — including undergraduates, interns, masters and doctoral students and NSF postdoctoral research fellow Harmony Colella — have already been conducting research with data generated by the western Transportable Array stations. Brudzinski also has research projects under way that will make use of data from Ohio seismic stations.
The EarthScope seismic station at the ERC “will be a great educational resource for students here at Miami,” Brudzinski said. “Since I have had several active field experiments where students are involved in the deployment and servicing of seismometers in various parts of the world, it is a great help to have a real seismic station deployed in our backyard.”
“This is a good example of how Miami provides a unique combination of teaching and research opportunities for our students.” (see sidebar).
Research: EarthScope West Coast, Fault Tremor
“I have several student projects that use the portions of the EarthScope USArray that have been deployed out west in Oregon, Washington, California and Alaska, including Miami students deploying some of the seismometers in the Cascadia subduction zone,” Brudzinski said.
“These projects have been looking at earthquakes and their recently discovered cousin called fault tremor. This fault tremor is a much more subtle and frequent rumbling of fault slip that appears to be occurring on the deep roots of faults, and has been the primary research focus of my NSF CAREER grant. The tremor indicates movement on the fault just below the area of giant earthquakes like the one in Japan that generated the devastating tsunami. It has been suggested fault tremor could trigger large earthquakes, as it appears to be tickling the dragon’s belly.”
Brudzinski currently has four graduate students and six undergraduate students working on this aspect of the EarthScope USArray data. One of those graduate students is Stefany Sit, a fifth year doctoral student in seismology.
“The USArray seismometers allowed us to better monitor tectonic tremor and its potential relationship to large, hazardous earthquakes,” Sit said. She has been working on the project along with Devin Boyarko, who has just successfully defended his doctoral thesis and begun a career at Chevron.
“Because fault tremor is a relatively new signal, I work on detecting when and how often the signal is occurring. In the Pacific Northwest, large fault tremor episodes occur about every 15 months. A change in the recurrence interval might indicate when an earthquake is more likely to happen,” Sit explained.
EarthScope Transportable Array – Ohio projects:
Examining thickness of continental crust
Brudzinski’s summer intern, Calvin Johnson, an undergraduate doing a combined math-geology program at Fort Valley State University in Georgia and Pennsylvania State University, is working with Brudzinski on a project to better examine the thickness of the continental crust across Ohio, particularly in comparison to other portions of the eastern U.S.
“In our preliminary work, we see an unusual anomaly that suggests the crust under northern Ohio may be thicker, possibly due to processes related to assembling of the continent many hundreds of millions of years ago,” Brudzinski said. “This initial research was primarily done with our OhioSeis network, but the EarthScope USArray will provide a great improvement in our resolution to the structure of the crust in Ohio.”
The continental crust is the approximately 20-mile-thick upper layer of the Earth, and represents the most heterogeneous and resource rich portion of the Earth.
Examining Recent Seismic Activity in Ohio
“EarthScope also will help locate and define previously unknown faults in Ohio like the one that resulted in a swarm of earthquakes near Youngstown last year,” Brudzinski said.
Steve Holtkamp, doctoral student in geophysics, is working on a project that will use Transportable Array seismic station data to examine the recent seismicity in Ohio. “This project has mainly been focused on the Youngstown swarm and its potential relationship to wastewater pumping, but the arrival of the EarthScope Transportable Array will allow us to look for any other possible swarms of smaller seismicity that might go undetected with our current shoestring-budget OhioSeis network,” Brudzinski explained.
Miami’s Transportable Array Seismic Station
The installation at the Ecology Research Center (ERC) on June 29 of Transportable Array station P49A was one of the first in the state. All seismic stations in Ohio are planned to be installed before winter.
When completed, nearly 2,000 locations will have been occupied during the 10-year program. The first footprint was established from north to south along the westernmost quarter of the U.S. in 2004. The array has now arrived in Ohio, and will travel east after two years.