The Japan Meteorological Agency has not detected any abnormal changes since it began closely monitoring any signs of a megaquake. 

Following the magnitude 7.1 earthquake that occurred in the Hyuganada Sea in southwestern Japan on August 8, an alert warning for a possible megaquake in the Nankai Trough region was issued. 

The weather agency has said that there is now a greater likelihood of a significant earthquake occurring at the assumed source area of the Nankai Trough earthquake than would normally be expected. 

The agency has confirmed that 24 earthquakes with a Japanese seismic intensity of 1 or higher, including one with an intensity of lower 6, have been observed in the assumed source area of the earthquake by noon on August 12. 

The maximum Japanese seismic intensity is 7. 

The Japan Meteorological Agency and the Cabinet Office are urging people to maintain an evacuation-ready stance for one week following the earthquake. 

The agency said on August 13 that if no further changes are observed, the alert for a major earthquake will end at 5 p.m. on August 15.