Belt-Parallel Shortening in the Northern Apennines and Seismotectonic Implications

Abstract

Major seismic activity in the Northern Apennines concentrates in few zones, distributed in a peculiar way. It is argued that such context may be plausibly explained as an effect of belt-parallel shortening, which has caused oroclinal bending of the longitudinal ridges formed during the Late Miocene to Lower Pliocene evolutionary phase. The main effects of this process, developed since the upper Pliocene, have mainly affected the outer sectors of the belt. The major seismic sources have generated in the zones where different oroclinal bendings of adjacent ridges have produced extensional/transtensional deformation. In the inner side of the Northern Apennines, belt parallel shortening has occurred at a lower rate. The main effects have resulted from the shortening of the Albano-Chianti-Rapolano-Cetona ridge. In particular, the proposed tectonic setting may account for the moderate seismic activity that occurs in the Firenze, Elsa, Pesa, Siena and Radicofani basins.

Present Velocity Field in the Italian Region by GPS Data: Geodynamic/Tectonic Implications

“…The GPS velocity field given in Figure 9 is compatible with the kinematic pattern of the Apennine belt deduced by the analysis of long-term evidence [8]- [14] [76] [77], with particular reference to the fact that the outer belt moves significantly faster and with a greater eastward component with respect to the inner belt (Figure 8).…”

Best Strategy for the Development of a Seismic Prevention Plan

“…Unfortunately, the limited length of the known seismic history that can be tentatively taken as reliable and complete (since 1400 A.D.) only allows the recognition of few migrating periAdriatic seismic sequences. However, it must be considered that the reliability of our assumption is also supported by the fact that the observed behaviour of seismicity is based on a physically plausible tectonic interpretation, supported by a huge amount of evidence from all branches of Earth Sciences [7,[10][11][12][13][14][15][16][17]. Red bars in the diagrams indicate the total seismic slip (metres) occurred during the related year, computed by the relation log 10 u= −4.8 + 0.69M, where u is the average seismic slip on the fault (in metres) and M is the earthquake magnitude [13].…”

“…A detailed description of the evidence and arguments that led us to advance the above prediction is reported in some recent publications [7][8][9].…”

“…Since it is well known that earthquakes are deterministic phenomena, closely connected with the progressive development of crustal deformations, any attempt at recognizing the future paths of seismicity in the study area can provide reliable results only if it is carried out by an adequate deterministic approach, based on a profound knowledge of the ongoing tectonic context. This kind of approach has been described in some publications [7][8][9]. Abstract.…”

“…Since it is well known that earthquakes are deterministic phenomena, closely connected with the progressive development of crustal deformations, any attempt at recognizing the future paths of seismicity in the study area can provide reliable results only if it is carried out by an adequate deterministic approach, based on a profound knowledge of the ongoing tectonic context. This kind of approach has been described in some publications [7][8][9]. In this note, we report a synthesis of the proposed procedure, in particular we describe the mechanism that it is supposed to control the spatio-temporal distribution of seismicity in the central Mediterranean region and the way by which such knowledge can allow the recognition of the Italian zones most prone to the next strong earthquakes in Italy.…”