The Yomiuri ShimbunThe earthquake that struck Kumamoto Prefecture early Saturday had a magnitude of 7.3, the same as the Great Hanshin Earthquake in 1995, in which more than 6,400 people died or remain missing.

The Saturday quake had more than 10 times the energy of the magnitude-6.5 earthquake that occurred Thursday evening, which caused strong shaking in limited areas. On Saturday, violent tremors measuring as high as upper 6 on the Japanese intensity scale of 7 were felt over a wide area.

Experts said the earthquake occurred as multiple faults moved in conjunction with each other, and warned that earthquakes will continue over a wide area.

According to the Japan Meteorological Agency, this is the first magnitude-7 class earthquake with a shallow focus since a magnitude-7 quake in the Hamadori area in Fukushima Prefecture, that is believed to have been an aftershock of the Great East Japan Earthquake in 2011. In the Kyushu region it was the first of that size and type in 11 years, since the magnitude-7 earthquake with its focus in the Genkainada sea in western Fukuoka Prefecture in 2005.

According to the agency’s analysis, Saturday’s quake was a “strike-slip” type, in which the fault involved moved horizontally due to its being pulled to the northwest and southeast. Thursday’s quake and the 1995 Hanshin earthquake involved the same “strike-slip” mechanism.

Yuji Yagi, an associate professor of geodynamics at University of Tsukuba, analyzed the seismic waves from the Saturday quake and said the fault appeared to have moved over an area about 50 kilometers long and 20 kilometers wide.

The underground destruction stretched northeast from the quake’s focus and continued for about 20 seconds.

The focus of Saturday’s quake was located on the northern side of the Futagawa fault zone, which cuts east to west across Kumamoto Prefecture and is at least about 64 kilometers long in its entirety.

The government’s Earthquake Research Committee had deemed there to be “an almost zero to 0.9 percent chance” of a magnitude-7 earthquake occurring in the northeast part of the Futagawa fault zone within 30 years.

The Hinagu fault zone lies to the south of the focus of Saturday’s quake, stretching at least about 81 kilometers. Part of the Hinagu fault zone is believed to have moved in the Thursday earthquake.

Yasuhiro Suzuki, a professor of tectonic geomorphology at Nagoya University, said part of the Futagawa fault zone moved in the Saturday morning earthquake. “It’s appropriate to think of the Hinagu and Futagawa fault zones as connected active faults. The earthquake on Saturday occurred in conjunction with the quakes that have happened from Thursday on, so it appears that part of a very large fault moved,” Suzuki said.

According to Takeshi Matsushima, an associate professor at Kyushu University of solid-state geophysics, the ground in the Kyushu region is subject to forces that pull it north-south. This creates the Beppu-Shimabara rift zone, in which the ground is subsided from Oita to Kumamoto. It contains the Hinagu and Futagawa fault zones, as well as the Beppu-Haneyama fault zone.

Seismic activity has intensified from the southwest to the northeast of the rift zone.

Regarding this fact, the Japan Meteorological Agency said at a Saturday press conference that “large earthquakes have occurred in three locations: Kumamoto, Aso and the central areas of Oita Prefecture.”

The government’s Earthquake Research Committee has decided to hold an emergency meeting on Sunday regarding the quakes. It will examine the causes of the seismic activity and prospects for the future.Speech