The Japan Meteorological Agency continues to urge caution against a possible mega-quake in the Nankai Trough along the Pacific coast.
The agency says no irregular changes have so far been observed in the crustal strain.
A special advisory was issued for the first time on Thursday after a magnitude 7.1 tremor struck off Miyazaki Prefecture in southern Japan.
The quake caused tsunami that reached the coasts of Kyushu and Shikoku islands. A 50-centimeter tsunami was observed at a port in Miyazaki City.
On land, the tremor registered a maximum intensity of lower 6 on the Japanese scale of 0 to 7 in Nichinan City.
Intensities of upper 5 were registered in parts of Miyazaki and neighboring Kagoshima prefectures.
As of 2 p.m. Friday, more than 10 perceptible jolts were observed in the region, including one with a magnitude of 5.3 early in the morning.
The Meteorological Agency says the probability of a major earthquake in the Nankai Trough is higher than usual. It issued the special advisory urging caution under what is known as the Nankai Trough Earthquake Extra Information protocol.
Agency officials say the advisory does not mean that a quake will definitely strike within a certain timeframe. But they have asked 707 municipalities in 29 prefectures — extending from around Tokyo in the east to Okinawa in the south — to check their disaster preparedness.
The government is advising people to secure furniture, and to check evacuation sites and ways to confirm the safety of their family members.
Households with infants, the elderly and people with disabilities are being advised to consider evacuating voluntarily.