NHK has learned a Japanese public research body will expand its network of crustal strain gauges to the southwestern region of Kyushu. Data taken by the devices help detect signs of an expected mega earthquake.

Japanese experts estimate there is a 70 to 80 percent chance a magnitude 8 to 9 quake will strike the Nankai Trough off Japan's Pacific coast in the next 30 years when crustal strain along tectonic boundaries in the trough is released.

The trough extends along a wide stretch from waters off the central prefecture of Shizuoka to an offshore area just east of Kyushu.

Strain is building up in the trough as the Philippine Sea Plate is sinking underneath, dragging down the edge of the Eurasian Plate.

Strainmeters, or instruments to continuously measure crustal strain, are currently in operation at 39 locations along the trough, but not in Kyushu.

The National Institute of Advanced Industrial Science and Technology, or AIST, will place a strainmeter deep underground in Kyushu's Oita Prefecture on Sunday.

The institute plans to provide data collected by the device to the Japan Meteorological Agency after conducting a verification test.

AIST also intends to set up a strainmeter in Miyazaki Prefecture, also in Kyushu, in the fiscal year starting in April.

The institute says researchers hope the devices will help them better understand crustal movements in and around Kyushu and enhance the accuracy of their observations of strain levels along the trough.