Slightly after thirty-five minutes past midnight on Sunday 15 January 2011 local time (slightly after 4.35 pm on Saturday 14 January, GMT) an Earthquake with a magnitude of 5.7 on the Richter Scale struck in the Babuyan Islands of the Northern Philippines, at a depth of about 22.4 km, according to the United States Geological Survey. There are no reports of any casualties or serious damage, nor has a tsunami warning been issued.
Map showing the location of the quake, from the United States Geological Survey.
The Babuyen Islands are part of the Luzon Volcanic Arc, a chain of volcanic islands running between Luzon in the Philippines to the south and Taiwan to the north. The arc lies on the western fringe of the Philippine Sea Plate, on the boundary with the Yangtze Plate, which is being subducted beneath it. As the subducting plate sinks into the Earth's interior, it is heated by the planet's internal heat and partially melts. Some of the melted rocks then rise through the overlying Philippine Sea Plate, forming the volcanoes of the Luzon Arc.
Diagrammatic representation of a volcanic island arc on a subductive margin.
There are five major islands in the Babuyans; Babuyan, Calayan, Camiguin, Dalupiri and Fuga.
Babuyan Island is dominated by Smith Volcano, a 688 m stratovolcano (cone-shaped volcano made up of layers of ash and lava) that last erupted in 1924.
Smith Volcano, on Babuyan Island.
Calayan Island is home to Babuyan Claro, an 843 m complex-stratovolcano (a stratovolcano with a structure more complicated than a simple cone) with a hot spring system on its southern flank, and four separate summit cones, Mount Cayonan, Mount Naydi, Mount Dionisio and Mount Pangasun. The last eruption on Babuyan Claro was in 1917, but an Earthquake on the island lead to emergency seismic monitoring in 1993, and a smoke cloud was reported over the summit in 2008.
Babuyan Claro, on Calayan Island.
There are seven volcanoes on Camiguin Island; Timpoong, Mambajao, Tres Marias, Guinsiliban Peak, Vulcan, Uhay and Hibok-Hibok. Of these only Hibok-Hibok is still active; its last major eruptive episode was in 1948-52, when more than 3000 people died and over half the population of the island emigrated.
Hibok-Hibok on Camiguin Island.
Dalupiri and Fuga lack volcanoes of note, but a new island, Didicas, emerged from the sea after a volcanic eruption in 1952. Mount Didicas now stands 288 m above the sea.
The new volcanic island of Didicas.