Research Press Release

Earthquake an unlikely cause of Lusi mud eruption

Nature Geoscience

June 30, 2015

The devastating Lusi mud eruption in Indonesia is unlikely to have been triggered by the Yogyakarta earthquake that occurred two days before the initial eruption, write Mark Tingay and colleagues in a Correspondence published online in Nature Geoscience.

The Lumpur Sidoarj, or Lusi mud eruption, which began in May 2006, has discharged hundreds of thousands of cubic metres of mud from the ground and is ongoing. The flow of mud has displaced almost 40,000 people and cost billions of US dollars in damage. The cause of the eruption is vigorously debated. Hypotheses include a natural trigger by passing seismic waves from the Yogyakarta earthquake and a human-induced trigger associated with nearby gas drilling operations.

The authors analysed the concentration and composition of gases emitted from a borehole located close to the eruption vent in the days before and after the Yogyakarta earthquake. They find no record of raised gas emission from the vent in the immediate aftermath of the quake ? a signal that would be expected if seismic waves from this earthquake had caused liquefaction in a subsurface layer of clay prompting the mud to erupt. Furthermore, the composition of the gases indicates that the erupted fluids did not come from the clay layer. Instead, the fluids may have come from a deeper volcanic rock layer and mixed with mud on their way to the surface. The bottom of the borehole is thought to lie within this deep volcanic rock layer. Tingay and colleagues note that these observations are consistent with the hypothesis that the mud eruption was triggered by drilling operations.

This press release refers to a Nature Geoscience Correspondence, not a Nature Geoscience research paper or article. The data herein have been peer reviewed for accuracy. Correspondence pieces provide a perspective on a science-based matter of public importance.

DOI:10.1038/ngeo2472 | Original article

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