18 Avril 2016
A seismology expert says horizontal shifts by up to nearly 2 meters along a 50-kilometer fault caused Saturday's magnitude-7.3 quake in southwestern Japan.
Associate Professor Yuji Yagi of the University of Tsukuba assessed the movements of the fault, using data observed at various locations around the globe.
The professor says the horizontal shifts by up to 1.8 meters occurred along the fault about 50 kilometers long and about 20 kilometers wide.
The government's Earthquake Research Committee released its estimation that Saturday's quake likely occurred as the result of movement of some part of a major active fault called the Futagawa Fault.
Yagi says the fault he assessed coincides with the Futagawa Fault. But he says his assessment shows the fault could extend a further 10 kilometers northeastward than the government panel's estimation.
He says the quake caused damage in a northeast direction toward Minami-Aso Village where it registered an intensity of up to six-plus on the Japanese seismic scale of 0 to 7. Yagi says it was likely to have been the most severely-hit in the region.
Yagi says seismic waves can overlap each other in the direction of horizontal shifts, and increase the jolt of quakes. He says this mechanism could have contributed to the major damage in the village.