EGU2020-11814
https://doi.org/10.5194/egusphere-egu2020-11814
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Structural Complexity and Mechanics of a shallow crustal Seismogenic Source (Vado di Corno Fault Zone, Italy)

Michele Fondriest1, Fabrizio Balsamo2, Andrea Bistacchi3, Luca Clemenzi2, Matteo Demurtas4, Fabrizio Storti2, and Giulio Di Toro5
Michele Fondriest et al.
  • 1IsTerre, Universitè Greonoble Alpes (michelefondriest@yahoo.it)
  • 2Università degli Studi di Parma
  • 3Università degli Studi Milano Bicocca
  • 4University of Oslo
  • 5Università degli Studi di Padova

The mechanics and seismogenic behaviour of fault zones are strongly influenced by their internal structure, intended as three-dimensional geometry and topology of the fault/fracture network and distribution of the fault zone rocks with related physical properties.  In this perspective, the internal structure of the extensional seismically active Vado di Corno Fault Zone (Central Apennines, Italy) was quantified by combining high-resolution structural mapping with modern techniques of 3D fault network modelling over ∼2 km along fault strike. The fault zone is hosted in carbonate host rocks, was exhumed from ∼2 km depth, accommodated a normal slip of ∼1.5-2 km since Early-Pleistocene and cuts through the Pliocene Omo Morto Thrust Zone that was partially reactivated in extension.

The exceptional exposure of the Vado di Corno Fault Zone footwall block allowed us to reconstruct with extreme detail the geometry of the older Omo Morto Thrust Zone and quantify the spatial arrangement of master and subsidiary faults, and fault zone rocks within the Vado di Corno Fault Zone. The combined analysis of the structural map and of a realistic 3D fault network model with kinematic, topological and slip tendency analyses, pointed out the crucial role of the older Omo Morto Thrust Zone geometry (i.e. the occurrence and position of lateral ramps) in controlling the along-strike segmentation and slip distribution of the active Vado di Corno normal fault zone. These findings were tested with a boundary element mechanical model that highlights the effect of inherited compressional features on the Vado di Corno Fault Zone internal structure and returns distributions and particularly partitioning of slip comparable with those measured in the field.

Lastly, we discuss the exhumed Vado di Corno Fault Zone as an analogue for the shallow structure of many seismic sources in the Central Apennines. The mechanical interaction of the inherited Omo Morto Thrust Zone and the extensional Vado di Corno Fault Zone generated along-strike and down-dip geometrical asperities. Similar settings could play first-order control on the complex spatio-temporal evolution and rupture heterogeneity of earthquakes in the region (e.g. 2009 Mw 6.1 L’Aquila earthquake).

How to cite: Fondriest, M., Balsamo, F., Bistacchi, A., Clemenzi, L., Demurtas, M., Storti, F., and Di Toro, G.: Structural Complexity and Mechanics of a shallow crustal Seismogenic Source (Vado di Corno Fault Zone, Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11814, https://doi.org/10.5194/egusphere-egu2020-11814, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 01 May 2020
  • CC1: Comment on EGU2020-11814, Christopher Jackson, 04 May 2020

    Hi! Hugely exciting stuff, which provides some superb insights into the things we are imaging in 3D seismic data from several different basins! If you like, we could talk offline about some of the overlaps in our work. Oh, and a question: do you know if there was a strike difference between the pre-existing thrust and the normal fault? Thanks! Chris Jackson (Imperial College)

    • AC1: Reply to CC1, Andrea Bistacchi, 04 May 2020

      Hi, thanks for the nice comment! It would be interesting to chat offline, but I guess that at the moment it would be nicer for the community, and more in the spirit of this strange EGU meeting, if we try to chat online!

      BTW, if you are interested in fault zone architechture, have a look also at these:

      Best,

      andrea

      • AC2: Reply to AC1, Andrea Bistacchi, 04 May 2020

        Oops... the links in previous message got lost. I try again...

        • AC3: Reply to AC2, Andrea Bistacchi, 04 May 2020

          meetingorganizer.copernicus.org/EGU2020/EGU2020-22583.html

          meetingorganizer.copernicus.org/EGU2020/EGU2020-13800.html

           

          • AC4: Reply to AC3, Andrea Bistacchi, 04 May 2020

            Got it! Looks like the system removes hyperlinks...

            • CC2: Reply to AC4, Christopher Jackson, 04 May 2020

              Thanks Andrea! Even the system is learning this week! Yes. Let's chat later in the session. I meant we can chat after EGU, via email, if that's possible. Speak soon!

    • AC5: Reply to CC1, Michele Fondriest, 04 May 2020

      Dear Christopher,

      thanks for your nice comments. Sure, it would be nice to have a chat about potential work overlaps!!

      About the second question, the idea is that the original strike of the thrust is controlling the one of the subsequent normal fault; then the normal fault gets segmented where the lateral complexities of the thurst are (it seems so at least); in the ovestepping regions the strike of the normal faults is more controlled by current regional extension direction.

      Michele

      • CC3: Reply to AC5, Christopher Jackson, 04 May 2020

        Thanks Michele! We can chat later in the session more about this. Really interesting...

  • CC4: Comment on EGU2020-11814, Bailey Lathrop, 04 May 2020

    Hi Michele! Could you go into a little more detail on how you did the mechanical model? I wasn't quite sure and it looks ineretsting! Thanks!

    • CC5: Reply to CC4, Bailey Lathrop, 04 May 2020

      interesting**

      • AC7: Reply to CC5, Michele Fondriest, 04 May 2020

        Sorry ... Bailey

        and many other misspelled words

    • AC6: Reply to CC4, Michele Fondriest, 04 May 2020

      Dear Bealy, we used the Fault Response Modelling (FRM) module of MOVE. It is implemented in the software. It a Boundary Element Method (BEM) code based on elastic dislocation theory (like Poly3D of Stanford let's say; but you have less control on it I guess since it is built in the software). In our case, we made the mesh starting from our 3D model derived from the structural map, then we applied a remote stress field and look at displacements on fault surfaces.

      The idea was just to check what is the effect of a real complex geometry of master and secondary faults (likely deriving from the superposition of extension on a previous complex thrust zone) on dispacement distribution. Values of displacemnts themselves do not mean anything, are meaningful just in comparison; indeed the master fault in depth is likely to be a single one and the different segments join together, so the real displacement are much larger than on the secondary faults). This was a way to see locally (at the depth of section of the exposed fault zone) what happens in terms of displacement distribution if I make slide the system under a given stress field. The two scenarios with less and more extended master fault segments just consider a different effect of master fault displacement on the footwall block and the secondary faults, since in this kind of models the cumulatd displacement depend on the dimensions of the fault surfaces.

      Ciao Michele

      • CC6: Reply to AC6, Bailey Lathrop, 04 May 2020

        Very cool! That makes sense, thank you very much!