EGU2020-9580, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-9580
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A Monte Carlo Markov Chain Approach to Stress Inversion and Forecasting of Eruptive Vent Locations

Lorenzo Mantiloni1,2, Tim Davis1,2, Ayleen Barbara Gaete Rojas1, and Eleonora Rivalta1
Lorenzo Mantiloni et al.
  • 1Helmholtz Zentrum Potsdam - Deutsches Geoforschungszentrum (GFZ), 2.1, Germany (lorenzo@gfz-potsdam.de)
  • 2Universität Potsdam

Current approaches to vent opening forecast produce probabilistic maps on the base of the spatial density of past eruptive vents, as well as the surface distribution of structural features such as faults and fractures. One of the main challenges in forecasting future vent locations in the case of distributed volcanism is that we usually deal with scarce, spatially scattered data to support these approaches. As sophisticated as our statistical analysis can be, such data are difficult to interpolate between and extrapolate from, resulting in spatially coarse forecasts and large uncertainties. More recently, Rivalta et al. (2019) proposed a forecasting strategy to predict future vent locations, combining the physics of magma transport at depth (where magma trajectories are assumed to be driven entirely by stress) with a Monte Carlo inversion technique for key stress parameters. This method has been first tested on the Campi Flegrei caldera; however, further validations and development are needed. Here we validate the strategy of Rivalta et al. with data from analog models (air injection in gelatine). We stress a gelatine block in controlled conditions (extension/compression, surface loading/unloading, layering) and observe air-filled crack trajectories. With these data, we test a flavour of the strategy that combines boundary element magma trajectory calculations with a  Monte Carlo Markov chain approach. We find the scheme is able to retrieve the parameters of the stress imposed on the gelatine and forecast subsequent vents in the same experimental setups. We also discuss how it may be applicable to natural cases, and what data are necessary for the approach to be feasible.

How to cite: Mantiloni, L., Davis, T., Gaete Rojas, A. B., and Rivalta, E.: A Monte Carlo Markov Chain Approach to Stress Inversion and Forecasting of Eruptive Vent Locations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9580, https://doi.org/10.5194/egusphere-egu2020-9580, 2020

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Presentation version 1 – uploaded on 01 May 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: How do you think the cracks will interact with layering?

    A: Layering is an interesting point and in fact we run two experiments with a two-layered gelatin. Cracks were accelerating when passing from a denser to a less dense layer. However we still assumed a homogeneous medium when performing inversions and forecasts. That would be a further step to develop in the future

    Q: Planning to include topography?

    A: Yes, in fact we also tried to apply surface loads and they can be modeled as well. The code can also reproduce topography and that will be a key point in the potential 3D update

    Q: How do the consecutive injections interact with one another?

    A: Unfortunately we neglected interactions between cracks. We always injected them separately, but the passing of one crack alters for sure the state of stress in the gelatin, at least in the surrounding area

    Q: And what are the main differences if you don't have a surface depression?

    A: As for surface depression, the main point is that its presence deflects crack trajectories away from its center when they approach the surface. If no depression were present, the cracks would just move straight upward, and with a surface load, they would be focused towards it

    Q: What do you mean by 'vent location'? Do you mean the sites where the first dike fingers reach the surface, or the eventual crater cones? These are not the same. Far from it.

    A: Sorry for the misleading term. In fact, "vent locations" stand for exactly the sites where the tip of the crack first reaches the surface

    Q: But these are normally not the crater cones you see on volcanic fissures

    A: Definitely not: what we observe in gelatin is a neat crack where the air bubble reaches the surface, and that is definitely different from what would happen in a real case with a magma dike. This is another point we will work on in the future