Photo/IllutrationThe Asahi Shimbun

  • Photo/Illustraion
  • Photo/Illustraion

The Japan Meteorological Agency warned residents of Osaka and surrounding prefectures June 18 to brace for strong aftershocks over the coming week following the magnitude-6.1 earthquake that rocked the region around the morning commute.

On a more reassuring note, agency officials told a morning news conference that it is “unlikely at this point” that the seismic activity could lead to a long-anticipated Nankai Trough earthquake, which would have devastating consequences for a long stretch of densely populated Pacific coastline from Shizuoka Prefecture to Kyushu.

The earthquake struck at 7:58 a.m. and registered lower 6 in northern Osaka Prefecture on the Japanese seismic intensity scale of 7, making it the strongest to hit the prefecture since record keeping started in 1923, officials said.

Officials also said its focus was 13 kilometers below the surface in northern Osaka Prefecture.

By 11 a.m., 10 earthquakes with intensities ranging from 1 to 2 were recorded in the area.

The Arima-Takatsuki fault zone, which is located near the focus of the June 18 earthquake, triggered the Keicho-Fushimi earthquake in 1596 that is thought to have had a magnitude of 7.5.

Agency officials were trying to determine whether the fault zone had any bearing on the latest quake.

The government's Headquarters for Earthquake Research Promotion had put the probability of the fault zone triggering an earthquake with a magnitude of 7.5 or so within 30 years at under 0.1 percent.

However, Toshiyuki Matsumori, director of JMA’s Earthquake and Tsunami Observations Division, noted that “an earthquake with a magnitude of 6 or so can hit Japan anywhere and anytime.”

The JMA also said it is unlikely that another fault zone responsible for the 1995 Great Hanshin Earthquake that leveled the port city of Kobe had any influence on the June 18 quake based on the distance between the two points.