BMKG said that the three areas prone to massive megathrust earthquakes were southwest of the Mentawai Islands off Sumatra, southwest of the Sunda Strait and Southern Bali. Mentawai, for example, experienced a massive 7.7-magnitude earthquake in 2010. Meanwhile, the southwestern part of the Sunda Strait to Bengkulu, specifically from Pangandaran to Cilacap, experienced a 7.7-magnitude earthquake that caused a tsunami. Recently, Malang (East Java) and the southern part of Sumba have also seen earthquakes with magnitudes of up to 8 on the Richter scale. The southern part of Bali is located on the same megathrust fissure with Malang and Sumba, Bali too possed the potential to suffer an 8-magnitude earthquake.
BMKG released this information to alert the public about the potential for earthquakes and tsunamis in their regions, so that they could be better prepared if and when a disaster occurred. Megathrust earthquakes, which occur on the fissure borders of the earth’s tectonic plates, are notorious for their excessive magnitudes that can reach beyond 9 on the Richter scale.