Why Japan’s earthquake has Bali on edge over magnitude 9 ‘megathrust’ risk
Bali, Sumba and the Flores Islands are expected to be the worst hit from a megathrust earthquake in the Sumba fault

Hours after the quake, the Japan Meteorological Agency issued a special advisory warning of a slightly elevated risk of a temblor with a magnitude of 8 or stronger in the coming days. It said there was a 1 per cent chance of a megaquake, compared with 0.1 per cent at other times.
Monday’s temblor came just days after the Bali Meteorology, Climatology, and Geophysics Agency (BMKG) issued a fresh round of warnings about the risk of a megathrust earthquake with a magnitude of 9.0 on the Richter scale hitting the island.
According to the US Geological Survey, megathrust happens when a stuck tectonic plate along a fault slips under its neighbour, resulting in giant earthquakes. Other more frequent smaller earthquakes also occur within the lower plate or the crust of the upper plate.
Bali, Sumba and the Flores Islands are expected to be the worst hit from a megathrust earthquake, according to The Bali Sun.

The BMKG, however, stressed that the warnings were a risk assessment rather than a prediction.