The earthquake hit just before 3 am local time. The IMO website showed a magnitude of 3,8 but seismologists have referred to the earthquake as a 4,0 one in discussions with Icelandic media.
The earthquake is the largest to hit the area since 1996 when the magnitude was 5,0. Its believed to have started the eruption in Gjalp. The earthquake last night is estimated to have occurred at a depth of approximately six kilometers below the glacier surface.
"It's the largest earthquake measured in the area since the eruption in Gjalp in 1996. There's full reason to expect an eruption,“ says Kristin Jonsdottir, at the IMO. More on Jonsdottir's views and the possible volcano eruption here.
See Icelandic version here.
The seismic activity in Bardarbunga on the Vatnajokull glacier is very powerful and therefore full reason to expect a volcanic eruption according to a specialist at The Icelandic Meteorological Office. A live webcam has been placed in the vicinity of Bardarbunga.