Purdue professor studies how 2011 Japan earthquake increased, decreased risks on other fault lines

WEST LAFAYETTE, Ind. - A Purdue University geophysicist is studying how earthquake risks in other areas of Japan were affected by the March 10, 2011, Tohoku earthquakes that led to a devastating tsunami and nuclear reactor meltdown.

Andy Freed, an associate professor of earth, atmospheric and planetary sciences, recently returned from Tokyo, where he met with Japanese scientists to begin an analysis of the shifting stresses on the fault lines below the country.

"A major earthquake reorganizes the stress field of an area, relieving it in some spots and increasing it in others," Freed said. "The massive earthquake in 2011 was so strong that it is probably the first of a new sequence of earthquakes. We are just trying to figure out where future earthquakes are most likely to occur."

Japan has the densest seismic and geodetic array in the world to precisely track tiny movements in the Earth's surface down to one millimeter over the course of a year. A team led by Freed will analyze the data collected by the array and create a model of ongoing geodynamic processes and how stresses are evolving in the Earth's crust below Japan. The model will be used to help determine which faults throughout the region have been pushed closer to failing due to the 2011 Tohoku earthquake and have the potential to initiate a major earthquake in the near future.

"There are shifts and changes in the Earth's crust long after we stop feeling the ground shake," he said. "By understanding how the stress field evolves we may be able to point to areas where the earthquake hazard is increasing."

This kind of analysis requires a couple of years of post-seismic data to calibrate what is happening beneath the Earth and could not be done immediately following the earthquake. It also will take several more years of data to refine and validate the model, he said.

The team is focusing on the dozens of fault lines under Tokyo because of its population density and the risk to human life of a major earthquake there, but researchers will also work to understand how earthquake hazards are changing throughout all of Japan.

Freed's team includes scientists from the University of Tokyo and the University of Southern California. The National Science Foundation funded this work.

Writer: Elizabeth K. Gardner, 765-494-2081, ekgardner@purdue.edu

Broadcast media contact: Jim Schenke, 765-494-6262, jschenke@purdue.edu