Imaging the tectonic framework of the 24 August 2016, Amatrice (central Italy) earthquake sequence: new roles for old players?

Lorenzo Bonini Lorenzo Bonini,Gianluca Valensise Gianluca Valensise,Paola Vannoli Paola Vannoli,Gabriele Tarabusi Gabriele Tarabusi,Umberto Fracassi Umberto Fracassi,Pierfrancesco Burrato Pierfrancesco Burrato,Vanja Kastelic Vanja Kastelic,Francesco Emanuele Maesano Francesco Emanuele Maesano,Michele Matteo Cosimo Carafa Michele Matteo Cosimo Carafa,Mara Monica Tiberti Mara Monica Tiberti,Roberto Basili Roberto Basili

doi:10.4401/ag-7229

Lorenzo Bonini Lorenzo Bonini, Gianluca Valensise Gianluca Valensise + Show 9 more

Open Access

https://doi.org/10.4401/ag-7229

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Abstract

We reconstruct the tectonic framework of the 24 August 2016, Amatrice earthquake. At least three main faults, including an older thrust fault (Sibillini Thrust), played an active role in the sequence. The mainshock nucleated and propagated along an extensional fault located in the footwall of the Sibillini Thrust, but due to the preliminary nature of the data the role of this thrust is still unclear. We illustrate two competing solutions: 1) the coseismic rupture started along an extensional fault and then partially used the thrust plane in extensional motion; 2) the thrust fault acted as an upper barrier to the propagation of the mainshock rupture, but was partially reactivated during the aftershock sequence. In both cases our tectonic reconstruction suggests an active role of the thrust fault, providing yet another example of how structures inherited from older tectonic phases may control the mainshock ruptures and the long-term evolution of younger seismogenic faults.

Highlights

The Mw 6.0, 24 August 2016, Amatrice earthquake devastated a mountainous area of the Central Apennine, claiming nearly 300 casualties
Ongoing extension in the area is testified by the analysis of crustal strain and seismicity data (e.g. Carafa and Bird, 2016), yet the tectonic setting and the landscape of the region are still dominated by the contractional structures of the Neogene-Quaternary Apennines fold-and-thrust belt
In addition to the previously described tectonic features, i.e. the normal faulting source of the mainshock, the portion of the Sibillini Thrust reactivated as a normal fault and the antithetic fault, all sections show a cloud of seismicity defining a very low-angle E-dipping plane that extends beneath the source of the mainshock at ~10 km depth (Fig. 2b-d-f)

Summary

INTRODUCTION

The Mw 6.0, 24 August 2016, Amatrice earthquake devastated a mountainous area of the Central Apennine, claiming nearly 300 casualties. Its aftershock sequence spreads over a NNW-SSE trending, ~30-km-long, ~15-kmwide area (Fig. 1). The moment tensor solutions of the mainshock and of the largest aftershocks (http://cnt.rm.ingv.it/tdmt) indicate the activation of extensional faults striking NNW-SSE and dipping 40°-50°. Carafa and Bird, 2016), yet the tectonic setting and the landscape of the region are still dominated by the contractional structures of the Neogene-Quaternary Apennines fold-and-thrust belt. The currently active structures have not yet fully reshaped the Apennines highs-and-lows of contractional origin with extensional basin-andrange-type landforms. This study provides a preliminary interpretation of the sources of the Amatrice earthquake sequence through the integration of all available geological, seismological, and geodetic data.

SEISMOTECTONIC MODELING

DISCUSSION

CONCLUSIONS