Osaka Inland Quake Occurs near Active Fault: Meteorological Agency

June 18, 2018

Tokyo- The 6.1-magnitude earthquake in northern Osaka Prefecture on Monday morning occurred "very close" to the Arima-Takatsuki fault zone, where a 7.5-magnitude quake happened in 1596, according to the Japan Meteorological Agency.

The latest temblor was the first to register at least lower 6, the third highest level on Japan's seismic intensity scale of 7, in the western prefecture, since the agency started earthquake monitoring in 1923.

Noting that it was an inland quake that happened inside the earth's crust, Toshiyuki Matsumori, head of the agency's earthquake and tsunami monitoring division, told a press conference that similarly large aftershocks may hit the region over the next week.

The research committee of the government's Headquarters for Earthquake Research Promotion has estimated the probability of an earthquake with a magnitude of around 7.5 occurring in the active fault over the next three decades at zero to 0.03 pct.

The committee, which includes members from the agency, is slated to examine any link between the Osaka quake and the fault zone at an emergency meeting on Monday afternoon.

The Rokko-Awajishima fault belt, which caused the 1995 Great Hanshin Earthquake, runs southwest of the Arima-Takatsuki belt.

Matsumori said there believed to be no direct link between the Rokko-Awajishima fault and the Osaka shake.

He also said the inland quake is unlikely to have implications for a predicted massive earthquake in the Nankai Trough off the country's central-western Pacific coast.

Many active faults exist around the latest quake's center.

An earthquake caused by the Uematch fault belt, which lies north and south under the city of Osaka, is expected to leave severe damage in the biggest city in western Japan.

"Chances cannot be ruled out that nearby areas will be hit by temblors triggered by the latest one," Tohoku University Prof. Shinji Toda warned.

"We can't deny the possibility of an even bigger earthquake in the region," Nagoya University Prof. Nobuo Fukuwa said. Jiji Press