Photo/Illutration Seismic intensity levels on the Japanese scale of 7 following the magnitude-5.1 earthquake that struck Ibaraki Prefecture on Aug. 19 (Data from the Japan Meteorological Agency)

Two earthquakes rocked Ibaraki Prefecture and surrounding areas early on Aug. 19, prompting authorities to warn residents to stay alert for strong tremors over the next week.

A magnitude-4.7 quake hit the northern part of the prefecture at 12:48 a.m., followed two minutes later by a temblor of magnitude 5.1 at the same location, according to the Japan Meteorological Agency.

The second quake registered a seismic intensity of lower 5 on the Japanese scale of 7 in Hitachi.

No tsunami warning has been issued.

However, the JMA warns of possible earthquakes with maximum intensity of lower 5 for the next week.

The depth of the second earthquake was 8 kilometers.

It caused a seismic intensity of 4 in Takahagi, north of Hitachi, while Hitachiota, Hitachinaka, Tokai and other municipalities in the prefecture experienced a seismic level of 3.

Parts of Fukushima, Tochigi and Saitama prefectures also recorded a seismic intensity of 3.