Publication Date:
2023-03-20
Description:
The footwall of the surface rupturing Paganica normal fault, the source of the 2009 L’Aquila earthquake (Mw 6.1) in the Central Apennines (Italy), was investigated using integrated geological and geomorphological approaches. The aim was to constrain the active tectonics by studying the Raiale River that orthogonally crosscuts the fault trace, where it provides a useful geomorphological marker of long-term fluvial incision and footwall uplift. Using morphostratigraphy and paleomagnetic analysis, the Plio–Pleistocene morphotectonic evolution of the area was reconstructed, comprising an ancient continental basin and paleolandforms that predate the footwall incision. Starting from the Late Early Pleistocene–Middle Pleistocene, fluvial dissection was mainly due to marked river downcutting triggered by significant activity of the Paganica Fault, which caused progressive base-level lowering. The Raiale River downcutting formed five Middle–Late Pleistocene fluvial terraces, that, along with absolute Optically Stimulated Luminescence (OSL) dating, allowed the identification of paleolongitudinal profiles with a diverging downstream configuration. Terrace dating yielded a minimum incision rate of 0.25 ± 0.02 mm/a, which only partially compensates the footwall uplift and can thus be considered as a minimum value for the Paganica Fault throw rate, which could reach up to ~0.45 mm/a. In parallel, using terrestrial cosmogenic nuclides, a denudation rate of 0.02–0.04 mm/a was measured on the summit of the footwall block. This denudation is in keeping with the drainage incision, suggesting a non-steady state for the fault footwall topography and a dominance of relief growth. Last, the analysis of the modern Raiale River longitudinal profile denoted an ungraded status, with two main knickzones that we interpret as transient forms due to tectonic perturbations, likely triggered by activity of the Paganica Fault during the end Early Pleistocene and the Late Pleistocene. Considering the 2009 L’Aquila earthquake coseismic rupture, we observe that the younger transience on the Raiale River longitudinal profile, if it is of tectonic origin, could have only been produced by much larger seismic events (i.e., Mw 〉 6.5) than those documented in the area by paleoseismological investigations. The collective results confirmed that in the Central Apennines, conditions of dynamic equilibrium are often not met, and that the persistence of transient perturbations induced by tectonics should be accounted for.
Description:
The work was financially supported by the MIUR (Italian Ministry of Education, University and Research) project “FIRB Abruzzo - High-resolution analyses for assessing the seismic hazard and risk of the areas affected by the 6 April 2009 earthquake”, ref. RBAP10ZC8K_005 and RBAP10ZC8K_007, and by Agreement INGV-DPC 2012-2021. The airborne LiDAR survey performedby the Civil Protection of Friuli Venezia Giulia (Italy) was kindly released by Italian Civil Protection Department Special thanks to Simone Atzori, who provided the InSAR data.
Description:
Published
Description:
108411
Description:
2T. Deformazione crostale attiva
Description:
JCR Journal
Keywords:
Earthquake geology
;
Active faults
;
L'Aquila earthquake
;
Morphotectonics
;
active faulting
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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