Lusi mud eruption triggered by geometric focusing of seismic waves

Journal name:
Nature Geoscience
Year published:
Published online
Corrected online

The Lusi mud eruption in Java, Indonesia, began in May 2006 and is ongoing. Two different triggers have been proposed. The eruption could have been triggered by drilling at a gas-exploration well, as evidenced by pressure variations typical of an internal blowout1, 2. Alternatively, fault slip associated with the M6.3 Yogyakarta earthquake two days before the eruption could have mobilized the mud3, as suggested by mixing of shallow and deeply derived fluids in the exhaling mud3, 4 and mud-vent alignment along a tectonic fault. Here we use numerical wave propagation experiments to show that a high-impedance and parabolic-shaped, high-velocity layer in the rock surrounding the site of the Lusi eruption could have reflected, amplified and focussed incoming seismic energy from the Yogyakarta earthquake. Our simulations show that energy concentrations in the mud layer would have been sufficient to liquefy the mud source, allowing fluidized mud and exsolved CO2 to be injected into and reactivate the Watukosek Fault. This fault connects hydraulically to a deep hydrothermal system that continues to feed the eruption. We conclude that the Lusi mud eruption was a natural occurrence. We also suggest that parabolic lithologies with varying acoustic impedance can focus and amplify incoming seismic energy and trigger a response in volcanic and hydrothermal systems that would have otherwise been unperturbed.

At a glance


  1. Map of Java with relevant distances from the Yogyakarta earthquake.
    Figure 1: Map of Java with relevant distances from the Yogyakarta earthquake.

    The blue square marks the position of Lusi and arrows show the distance between the epicentre of the Yogyakarta earthquake and the systems that responded to that event.

  2. Geometry,
Vp variations with depth and model of Lusi used in the numerical study.
    Figure 2: Geometry, Vp variations with depth and model of Lusi used in the numerical study.

    a, Seismic profile of the geological structures8 beneath Lusi used to reconstruct the geology of the model. b, Vertical profile for V p velocities used in the model10. The acoustic impedance of faults is not known, so we assumed ρ=2,000kgm−3, V p=2,325ms−1 and V s=1,531ms−1. c, Distribution of V p velocities in the model domain. The mud layer is shaded grey, the cased and uncased well (not modelled) are shaded green and white, respectively.

  3. Results of the numerical study.
    Figure 3: Results of the numerical study.

    Simulation results for: a,d, Pwave; and b,c,e, f, Swave at 1.5Hz. e, Peak energy density of 1.25Jm−3 is reached above the seismic reflector and in the mud layer, demonstrating how the domed structure geometrically focuses energy. Dynamic stress σD (a,b), vertical displacement (c) and shear strain ε (f) induced by wave propagation shows how the lithology affects their distribution. Peaks of σD of 0.25MPa are observed immediately below the casing, whereas the induced dynamic stress in the mud layer is approximately 0.075MPa with peaks of 0.1MPa in the deeper part. Vertical displacements of 1.25mm occur in the mud layer, inducing peak strains of 20με.

  4. Conceptual stress path and proposed scenario for triggering the Lusi mud eruption.
    Figure 4: Conceptual stress path and proposed scenario for triggering the Lusi mud eruption.

    a, Amplified seismic energy perturbs the initial stress state (1), increasing pore pressure through cyclic shear stressing. Aftershocks (2) cyclically load the (impedance-reduced) mud layer, reaching the FSL. At the FSL, the mud layer either liquefied and lost strength (compacting), or strain hardened (dilatant). Fluid pressure reductions to below initial conditions trigger CO2 exsolution, mobilizing the mixture of mud, gas and water. b, State of system before the Yogyakarta earthquake with high fluid pressures and a narrow drilling window2. c, Liquefaction from Yogyakarta earthquake and aftershocks drew drilling mud into the layer. d, Liquefied mud layer injects and reactivates the pre-stressed Watukosek Fault system.

Change history

Corrected online 28 August 2013
In our 2013 article1, we adopted a published velocity profile2 described as check-shot data, which we used as an input constraint for our numerical simulations. We were subsequently alerted to artefacts in that velocity profile, so below we present revised simulation results, based on additional data.


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Author information


  1. Geodynamics/Geophysics, Steinmann Institute, University of Bonn, 53115, Germany

    • M. Lupi,
    • F. Fuchs &
    • S. A. Miller
  2. Geology Institute, ETH-Zurich, ETH 8092, Switzerland

    • E. H. Saenger


M.L. conducted the study, collected the data and constructed the geological model; E.H.S. conducted the numerical studies; F.F. conducted the seismological analysis; S.A.M. designed and coordinated the study and jointly wrote the manuscript with M.L. All authors contributed equally to the content.

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