A MAGNITUDE 5.4 tectonic earthquake shook Cagayan province in northeastern Luzon early morning Monday, April 16, with intensity 1 felt all the way in Santiago City, Isabela and Laoag City in Ilocos Norte. The tremor was recorded at 3:43 a.m., according to the monitoring of the Philippine Institute of Volcanology and Seismology (Phivolcs). The epicenter was located around Gonzaga town. The initial Phivolcs bulletin said aftershocks were expected and at least two were recorded before noon, a magnitude 2.4 at 5:05 a.m. and magnitude 2 at 10:02 a.m.