Seismic equipment is being installed throughout Indiana as part of a national program to better understand how and why earthquakes and volcanic events occur, and Purdue University professors and students spent time last summer surveying the state to find the locations best suited for the equipment.

The study is part of EarthScope, a National Science Foundation program that includes more than 400 portable seismometers that record data used to measure earthquakes, monitor the behavior of seismic waves, map movement of the Earth's surface and create images of the North American continent's crust and mantle. These observations will contribute to a better understanding of seismic hazards throughout the nation.

The network of seismometers, called USArray, has been migrating eastward across the United States since 2005. Indiana is among the strip of states from Michigan to Florida where installations began this fall.

Robert Nowack, a Purdue professor of geophysics, said the data collected in Indiana could address significant uncertainties about the New Madrid and Wabash Valley fault zones.

"This will be the most comprehensive seismic deployment in the region ever performed and will give us a much better understanding of the earthquake potential in this state," he said. "The information gathered could help save lives and money by leading to more informed building and bridge designs."

Approximately 23 sites will be installed across the state that include seismic, GPS, and other geophysical instrumentation.

All of the Indiana stations are expected to be installed and operational by late spring of 2012. Each station will remain at a location for two years before it is moved to a new location at the eastern edge of the array. Nearly 2,000 locations across the nation will have been occupied when the project is completed.

Hersh Gilbert, a professor of geophysics who, along with Nowack, led the Purdue siting team in Indiana, said the resulting data will be used to form high-resolution images of the Earth's interior to better understand the geology and tectonics of North America and the structures along which earthquakes occur.

The equipment also will be used for weather research, he said. Barometers and ultrasound sensors also have been added to the equipment to increase the types of data collected and its potential uses.

"This equipment captures everything from an aircraft flying above, a sonic boom in the area to different weather environments, as well as vibrations from earthquakes in the Midwest and around the world," Gilbert said.

"Massive amounts of data are being recorded, and scientists in any discipline from locations around the world will have access to it to perform research."

This past summer Gilbert, Nowack, and undergraduate students in Purdue's Department of Earth and Atmospheric Sciences Dane Dudley and Austin McGlannan performed reconnaissance to determine the best sites for seismic stations in Indiana and parts of northern Kentucky.

Dudley and McGlannan used geographic databases to identify optimal locations for seismic sensors. The team then visited the sites to inquire if landowners would be willing to host seismometers on their property and to verify that the locations were appropriate for a seismic station.

It is important that a site be free of local seismic noise, such as nearby rivers and road traffic, or exposure to too much wind, that can reduce the quality of the data recorded.

Each site also needs to have a strong wireless phone signal so that the seismic instrument can transmit data with good fidelity, Gilbert said.

At each location, a seismometer that measures north-south, east-west, and vertical movement is buried in a vault about six feet below the surface. Solar panels mounted on an eight-foot pole provide power.

Data is recorded continuously and is relayed in real-time via cell phone modems to the USArray operations center in California.

A permanent seismic station was previously set up on Purdue Research Foundation property about seven miles west of the West Lafayette campus. The station is part of a permanent backbone network of seismic stations that will provide a long-term data reference for comparison of observations made by the USArray.

Visualizations from the USArray network