EGU2020-552
https://doi.org/10.5194/egusphere-egu2020-552
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Applying seismic ring-fault models to real case scenarios

Rodrigo Contreras Arratia and Jurgen Neuberg
Rodrigo Contreras Arratia and Jurgen Neuberg
  • University of Leeds, Institute of Geophysics and Tectonics, Leeds, United Kingdom of Great Britain and Northern Ireland (eerac@leeds.ac.uk)

Previous studies have found discrepancies concerning the seismic radiation between planar and curved faults; moment tensor (MT) interpretations, seismic moment estimation and waveforms change dramatically when the rupture is not planar. Therefore, assuming a point source on a planar fault for earthquakes in volcanic environments can be an oversimplification that needs to be addressed if we observe some seismological clues. First, we study waveforms for LP events at Etna. To explain these waveforms we propose a full-ring rupture with an inner net movement of magma, in in contrast to the planar fault approach that returns a pulsating rupture. Second, we study MT inversions for the biggest earthquakes during the 2014-2015 collapse of the Bardarbunga caldera, which show non-double couple solutions, with vertical compression axis. We calculate synthetic seismograms for partial-ring ruptures using an “ideal” seismic network, and one emulating the existing monitoring network at Bardarbunga. Observations using distal stations can return a better-constrained seismic moment, but they fail to characterise the dynamics involved. On the other hand, using proximal stations we obtain a reliable representation of the forces involved; however, the seismic moment is systematically overestimated due to the proximity to the curved source and the corresponding focussing effects. Finally, we correct the area of rupture due to fault shape to estimate the real cumulative seismic moment during the caldera collapse. The result shows a closer relationship between seismic and geodetic moment.

How to cite: Contreras Arratia, R. and Neuberg, J.: Applying seismic ring-fault models to real case scenarios, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-552, https://doi.org/10.5194/egusphere-egu2020-552, 2019

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Presentation version 1 – uploaded on 04 May 2020
  • AC1: Correction about question during chat, Rodrigo Contreras Arratia, 05 May 2020

    Dear all, 

    To clarify my answer on: "How the dip angle affect our results when the ring fault is sub vertical?" (paraphrasing).

    The moment-dip trade-off has an effect on point source inversions when the rupture is a vertical DC. However, in our case, even though the point sources are sub-vertical DC, the combined effect of the radiation leads to a moment tensor dominated by an isotropic and CLVD components. Therefore, the dip of the faults does not affect the correction factors (magnitude of the events) when we use the appropriate regional network.