UC Santa Cruz researchers Casey Moore and James Kirkpatrick left the port of Shimizu, Japan on April 1 on a scientific expedition to analyze the fault located in the Japan Trench. The trench was the source of the Tohoku earthquake and following tsunami that devastated the coasts of Japan in March 2011.
Despite beginning research a year after the earthquake occurred, Emily Brodsky, UCSC professor of earth and planetary sciences and member of the project management team charged with overseeing the Japan Trench Fast Drilling Project (JFAST), said that JFAST continues to move rapidly.
“Starting in 2008, we started preparing to go after the next big earthquake,” Brodsky said. “From putting together a proposal to everything else, the Integrated Ocean Drilling Program (IODP) pushing this project through in only a year is unheard of.”
Moore and Kirkpatrick were among a team of researchers that embarked on the scientific drilling ship Chikyu, which is capable of drilling 7,000 meters below the seafloor, and will be used to obtain data and samples from the fault itself to analyze shifts in temperature on and off the fault.
The Chikyu is operated by the IODP, the international scientific research program behind JFAST. The expedition’s destination lies 200 kilometers east of the Japanese city of Sendai and seven kilometers down through the ocean and into the fault line of the Japan Trench.
“The purpose of the expedition is to try to understand how the fault we intend to drill was able to slip more than 50 meters — the longest documented slip in an earthquake ever,” said Moore, a research professor of earth and planetary sciences.
One hypothesis made by JFAST to explain the fault slip that caused the earthquake suggested low friction between the Pacific and Okhotsk tectonic plates that make up the Japan Trench.
“The low friction may be due to water ‘lubricating’ the fault,” Moore said. “Imagine hydroplaning when you put on the brakes in your car.”
Brodsky said that measuring the heat from the friction of the movement that caused the earthquake would determine whether low friction was the cause of the slip.
“We are still confused about how friction affects tectonic plates during earthquakes,” Brodsky said. “Something is holding the plates back from moving, but we don’t fully understand what that is. Although it has been a year since the earthquake, we predict that there is still half a degree of temperature difference due to the friction between the plates left.”
Brodsky said the temperatures remaining after earthquakes of past expeditions similar to JFAST have previously been reported as being only one-tenth of the original temperature caused by a slip. The half-degree prediction indicates how fast JFAST was able to start their research, in addition to how much heat the 50-meter slip was predicted to have generated.
“This earthquake left potentially the largest heat signal ever generated,” Brodsky said.
Although drilling six kilometers into the ocean and another kilometer through the seafloor has never been attempted before, the research team has faith that IODP engineers have created a drill that will enable them to successfully carry out their research.
“The most challenging issue is drilling the hole,” Moore said. “The deep water puts a lot of stress on the drill pipe and limits what you can do.”
If the drill is successful, the JFAST team’s main goal is to obtain a sample from the fault where the slip occurred. Researchers like Kirkpatrick would then plan to analyze and compare the sample to other faults and slips that have been examined on the surface of the Earth in other expeditions. Brodsky said that a sample from the fault can tell scientists where other earthquakes can occur, in addition to how earthquakes are triggered in general.
Although the drilling team will have to go to extreme lengths in order to collect the necessary data, the researchers remain hopeful that the project will be successful.
“We’re drilling in seven-kilometer water depth, which has never been done before, and we’re hoping it can be done,” Brodsky said. “This is high-risk, high-reward science.”