Abstract
AbstractUnderstanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.
Highlights
Understanding the recent geological evolution of highly populated regions is of paramount importance, especially when they are subject to seismic hazards, as is the central portion of the Po Plain
Evidence of Quaternary deformation in the sedimentary successions deposited along the southernmost portion of the central Southern Alps and along the Northern Apennines front is documented in seismic sections and drillings, especially along the southern portion of the Po Plain (Fig. 3), due to propagation of the Northern Apennines thrusts (Fantoni et al, 2004; Bresciani and Perotti, 2014)
Reconstructions of the regional subsurface Quaternary succession Starting from the 3D model of the middle-upper Quaternary successions of the Lombardian Po Plain (Cavallin et al, 2020), we obtained three original cross sections (Fig. 2) in the area of the present work (Fig. 6a)
Summary
Understanding the recent geological evolution of highly populated regions is of paramount importance, especially when they are subject to seismic hazards, as is the central portion of the Po Plain. The same scenario is suggested by displacements obtained from GPS measurements and SAR interferometry (Devoti et al, 2011, Farolfi et al, 2018; Anderlini et al, 2020), and from the distribution and intensity of seismic activity (Michetti et al, 2012). All these data show a larger amount of shortening and a higher cumulate moment tensor passing from the east to the west of the plain
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