EGU2020-19326
https://doi.org/10.5194/egusphere-egu2020-19326
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Transient tectonic switch in volcanic arcs: observations from the Southern Andes ( 33S - 38S).

Matteo Lupi, Daniele Trippanera, Diego Gonzalez-Vidal, Andres Tassara, Sebastiano D'Amico, Cabello Catalina, and Stef Marc Muelle
Matteo Lupi et al.
  • University of Geneva, Department of Earth Sciences, Geneva, Switzerland (matteo.lupi@unige.ch)

It has been shown that in the aftermath of megathrust earthquakes the forearc region moves trenchwards promoting crustal extension alterating the long term stress regime in place before the earthquake during the inter-seismic periods. In the far field such variations are less well-recognised and their influence on volcanic arc activity poorly constrained.

To tackle this problem we deployed a temporary seismic network in the volcanic arc of Southern Andes from November 2013 to April 2015 to investigate the tectonic deformation imposed by the M8.8 2010 Maule megathrust earthquake. The network is centred on the Nevados de Chillan Volcanic Complex is an Andean-transverse NW-oriented structure whose orientation is not well compatible with the current tectonic regime. The Nevados de Chillan faces one of the regions that slipped the most during the 2010 M8.8 Maule earthquake. The system was also reactivated after the earthquake and its activity is still ongoing at writing.

We compared the deformation of the geological records such as faults, fractures and dikes (assumed to be representative of inter-seismic periods) against the focal mechanisms inverted from shallow moderate-magnitude earthquakes occurred in the arc from 2010 to 2015. We found out that the geological record shows the imprinting of both long term inter-seismic and perturbed shorter term post-seismic deformation. In particular, the latter may create the conditions to re-activate NW pre-existing tectonic structures enhancing the magma upwelling sitting in the upper lithosphere.

Our work suggests that the kinematics driving the growth of NW-striking volcanic systems in the Southern Central Andes are affected by both magmatic and tectonic processes, with the latter experiencing short-lived perturbations.

How to cite: Lupi, M., Trippanera, D., Gonzalez-Vidal, D., Tassara, A., D'Amico, S., Catalina, C., and Marc Muelle, S.: Transient tectonic switch in volcanic arcs: observations from the Southern Andes ( 33S - 38S)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19326, https://doi.org/10.5194/egusphere-egu2020-19326, 2020

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Presentation version 1 – uploaded on 07 May 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: You say in your abstract that activity is still ongoing. What is the current state of activity?

    A: For instance, the Nevados the Chillan has been activated, extruded a dome that explodes from time to time. this system is elongated NW-SE

    Q: Are the fault controlling the offset between magma reservoir and volcano or you see a relationship between the location of the volcano with respect to the reservoir?

    A: We see that crustal-scale lineaments do cause a focusing of the magmatic fluids in the upper crust. We did not manage to map faults in the arc but to bridge with @Sjonni's question the main reservoir can be up to 20-30km away from the edifice, see for instance the example of the laguna del maule. One of the ideas that we are starting to explore is that backthrust may remamrkably contribute to the transport of fluids in the back arc

    Q: I just wanted to say that I really like the figures in your presentation! :) Do you think many magmatic reservoirs have an offset compared to their volcanic edifice in the world?

    A: Thanks :) We are processing an LET of East Java, and we sse it there as well, similar preliminary info from Costa Rica (Irazu-Turrialba). Images of volcanic arcs may shed more light on the role of large structures in transporting fluids