On Boxing Day, 2004, a magnitude 9.1 earthquake struck the northern tip of Sumatra. The quake created a massive tsunami that within 2 hours had reached the other side of the Indian Ocean. The tsunami killed more than 230,000 people across 14 different countries.
The earthquake and tsunami occurred because of the subduction of the Australian plate under the Eurasian plate. This process caused the seafloor to lift which displaced the seawater above it. This is what would most likely take place to cause the next major earthquake in Indonesia.
Indonesia is quite a low country that is surrounded by water so, it would be flooded by the tsunami that is bound to happen. The earthquake may also cause mud to lift, while the heavier objects like houses and buildings would sink. Many homes and workplaces would be destroyed by the mud and water. Increased volcanic activity may also be a side effect of the earthquake.
Lives would be destroyed but the tsunami and earthquake. Not only would the death toll be very high but the survivors would also be very effected. It's likely that kilometres of farm land would be flattened, for the surviving farmers their lives would now be ruined.