As locals struggle to cope with the devastation, nervous eyes are turning to Mount Merapi, the most active volcano in Indonesia. Merapi lies just 29km from the epicentre of Saturday's quake.
Government officials say activity has already tripled since the earthquake struck. Hot clouds are spewing from its mouth at a rate of 150 a day, compared with 50 a day previously.
Edward Bryant, a geologist specialising in natural hazards at Wollongong University in New South Wales, Australia, believes Merapi could be on the brink of a major eruption.
"It's no surprise the volcano is becoming more active. This could well be a precursor for a major eruption. I think it will come to a climax," he says.
Java lies at the edge of a subduction zone where the Australian tectonic plate grinds beneath the Asian plate. Molten material hundreds of miles deep rises up beneath Java, following an arc called Indonesia's Ring of Fire.
Prof Bryant believes an upswelling of magma from beneath the earth's surface may have triggered the earthquake and simultaneously seeped into the base of the volcano, causing the lava dome that caps it to swell. Mount Merapi has erupted 68 times since 1548. An eruption in 1994 killed 43 people. Thousands of villagers live on the lava dome and farm the fertile soils on the flanks of the volcano.
Officials have already ordered the evacuation of people from a danger zone around the top of the volcano but, Prof Bryant says, pyroclastic flows of hot gas and ash could destroy nearby towns and villages.
"Ash clouds can be sent up into the sky which collapse under gravity, giving powerful hot pyroclastic flows that travel down the sides of the volcano.
"The heat and power of the blast means they can knock over walls and pick up large concrete structures and move them around like pebbles in a stream," he says.
Vulcanologists will be monitoring Mount Merapi closely and further earthquakes will increase fears that a dramatic eruption is imminent.
Since Saturday's quake, more than 500 aftershocks have struck the region.
Warnings to evacuate are likely to meet with resistance, however, unless officials can guarantee looters will be prevented from raiding homes, crops and livestock.
"We have been wrong in the past. You can get an increase in activity and evacuate people and all of a sudden the volcano goes dead. But historically, there's a strong trend that whenever you get an earthquake close to a volcano, you get an eruption soon afterwards," says Prof Bryant. - (Guardian service)