IODP Drilling Project Studies Fault Behind Devastating Japanese Earthquake
Nov 4, 2016
Research from Dr. Patrick Fulton of Geology & Geophysics, along with Emily Brodsky of the University of California, Santa Cruz, reveals that earthquakes redistribute fluid pressures within fault zones – possibly leading to triggering other earthquakes.
In March of 2011, a catastrophic 9.0 magnitude earthquake struck off the Pacific coast of Tōhoku, Japan. The earthquake was the most powerful ever recorded to have hit Japan, and the fourth most powerful in the world since modern records began in 1900.
Inside the fault that created the devastating earthquake, a study was conducted measuring the temperature continuously for nearly a year – revealing the thermal signature of pulses of water squirting out of fractures in response to other earthquakes on neighboring faults.
“The Tōhoku-oki earthquake resulted in the largest amount of slip ever observed. The overriding plate and seafloor jumped more than 50 meters to the East over the down-going Pacific plate. This large slip contributed to a much greater size earthquake and tsunami that had been expected for this region,” said Dr. Fulton.
The International Ocean Discovery Program’s (IODP) Japan Trench Fast Drilling Project (JFAST) temperature observatory was installed inside the Japan Trench plate boundary fault zone more than 4.5 miles beneath the ocean, stretching nearly a half mile.
The JFAST observatory data captured temperature measurements within the damage zone above the Japan Trench plate boundary fault.
According to the study, pressure from fluid can reduce the strength of a fault. Water pressure within fault zones (which impacts the risk of faults to slip), can then become disturbed by earthquakes on other faults. The findings from the study also suggest that fluid pressures could be involved in triggering other earthquakes.
“To earthquake physicists, like myself, this is extremely interesting. We have long known that changes in fluid pressures within rocks can make them break or cause faults to slip. Here we see earthquakes on distant faults causing fluids to move around in ways that would change the stress conditions within a plate boundary fault zone and perhaps trigger other earthquakes,” explained Dr. Fulton.
As a result, scientists can gain a better understanding of the processes that control earthquakes through observing the interactions between faults in the aftermath of a major earthquake.
“This extremely challenging project was only feasible due to the unique drilling capabilities, engineering expertise, and scientific community framework associated with IODP”, added Dr. Fulton.
“We hope that our results will contribute to a better understanding of how hydrogeology within faults can both change in response to earthquakes and also influence the occurrence of other earthquakes.”
The research paper can be downloaded in its entirety here.