Tokyo ? Microtremors that have been observed in Shikoku, Japan – one of the expected epicentral areas of a predicted Nankai earthquake with magnitude 8 on the Richter scale – have occurred in accordance with tectonic movement of a plate slipping below Shikoku Island, it has been learned by a group of researchers from Tokyo University and Stanford University.

The research group published its findings in Wednesday’s issue of the science magazine Nature.

The movement is called a “slow slip,” in which a plate slowly slips below another plate.

The Nankai Earthquake is expected to occur along the trough stretching between a plate under Shikoku and an oceanic plate moving beneath another from the southeast. While microtremors around the region were detected in 2002, the cause has been unknown so far.