There are two types of fault lines running parallel to each other through the badly quake-hit Kumamoto Prefecture village of Nishihara, a research team led by Tohoku University seismology professor Shinji Toda has confirmed.
The magnitude-7.3 quake that struck the region on April 16 hit a seismic intensity of 7 on the 7-point Japanese scale in Nishihara. Toda and his team confirmed a normal dip-slip fault -- one that shifts vertically -- running parallel to a strike-slip fault -- one that shifts horizontally -- about 2 kilometers away. The Japan Meteorological Agency (JMA) has labeled the April 16 temblor a strike-slip fault quake, but the research team maintains that signs of horizontal movement in some places indicate the existence of a dip-slip fault as well.
The rips in the earth opened up by the quake were photographed from the air by the Geospatial Information Authority of Japan (GSI), and on April 24 Toda and his team travelled to Nishihara to examine the fissures first hand. At one running more than 2 kilometers northwest along the western slope of Mount Tawara, the earth had shifted vertically as much as 1.5 meters. Meanwhile, the parallel strike-slip fault had also moved by about 1.5 meters, but horizontally.
The April 16 earthquake is thought to have emanated from a hypocenter in the Futagawa fault zone. And Toda says that when it struck, it shifted the ground both horizontally and vertically along the fault plane, producing different types of deformations on the surface. He adds that the enormous energy unleashed by the quake caused a variety of stresses and deformations, a rare geological phenomenon called "slip partitioning."
Cambridge Dictionaries Onlineには“to suddenly release a violent force that cannot be controlled”と定義されていました。