Giusy Lavecchia
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Federico Pietrolungo
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Simone Bello
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Donato Talone
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Claudia Pandolfi
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Carlo Andrenacci
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Andrea Carducci
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Rita de Nardis*
DiSPuTer, Università G. d’Annunzio Chieti-Pescara, 66100 Chieti, Italy; and CRUST, Centro
InteRUniversitario per l’analisi Sismotettonica Tridimensionale, 66100 Chieti, Italy
Abstract
The Late Pliocene–Quaternary Outer Thrust System of the Apennine-Maghrebides fold-and-thrust belt extends
~2000 km from northern Italy to Sicily. Its northernmost arc is seismically active and represents a test
case to study geometries and seismogenesis of slowly deforming megathrusts developed within the continental
lithosphere. Two distinct SW-dipping reverse shear zones (T1 and T2) in the Outer Thrust System of eastern
Central Italy have been recently unveiled thanks to geological and integrated seismological information.
These shear zones penetrate the Adria continental lithosphere to a maximum depth of ~60 km, with an outward
convex shape associated with an outward-diverging radial pattern.
This paper presents new constraints on the megathrusts’ geometry in light of a novel microseismic catalog
(from 2009–2022) specifically focused on the compressional volume. Further details in the reconstruction of
T1 and T2 are derived from a recent compressional seismic sequence (November 2022, MW 5.5)
located in the Adriatic offshore. It activated the outermost T1 upper crustal segment with pure
compressional kinematics and illuminated T2 at lower crustal depths. We integrate geological sections,
seismic lines, serial hypocentral cross sections, and focal mechanisms to build a detailed nonplanar 3-D
model of the thrusts involved. In addition, we build Coulomb stress scenarios for analyzing the possibility
of the static interplay between the upper crust T1 segment activated by the 2022 sequence and the underlying
T2 crust segment. The overall results may be relevant for assessing seismic hazards in areas with
multi-depth active structures and for gaining insights into plate tectonic dynamics.
*rita.denardis@unich.it
CITATION: Lavecchia, G., Pietrolungo, F., Bello, S., Talone, D., Pandolfi, C., Andrenacci, C., Carducci, A.,
and de Nardis, R., 2023, Slowly Deforming Megathrusts within the Continental Lithosphere: A Case from Italy:
GSA Today, v. 34, p. 4–10, https://doi.org/10.1130/GSATG573A.1. © 2023 The Authors. Gold Open Access:
This paper is published under the terms of the CC-BY-NC license. Printed in USA.
Manuscript received 27 Apr. 2023. Revised manuscript received 10 Aug. 2023.
Manuscript accepted 6 Nov. 2023. Posted 5 Dec. 2023.
© The Geological Society of America, 2023. CC-BY-NC.
https://doi.org/10.1130/GSATG573A.1