The Lusi mud volcano

The Lusi mud volcano represents one of Indonesia's worst environmental disasters (BBC News). It has been erupting almost constantly for two years and now covers 7 km² of the Porong subdistrict of Sidoarjo in east Java. 30,000 people have lost their homes and there have been 13 fatalities. The disaster was almost certainly man-made—but this conclusion has been widely contested by the company involved and some scientists. A gas exploration borehole drilling down to 2834 m experienced an influx of salt water and gas 2 days before the eruption started. The influx was not spotted and when valves on the surface were eventually shut-in, the pressure in the wellbore was high enough to cause fractures to form in the subsurface rock strata. These allowed salt water and gases to mix with soft mud and for the mix to leak to the surface 150 m away from the drill rig. But Indonesia is seismically active and an earthquake also occurred two days before the eruption. With an epicentre 250 km from the eruption and a moment magnitude of 6.3 it was too small and too far away to have triggered the eruption. The company responsible for the borehole and a minority of scientists propose that the earthquake triggered the disaster. In this presentation it is shown that the earthquake mechanism is not credible—in contrast there is hard evidence that demonstrates that the exploration drilling was the cause.