Identification of areas of potential soil instability and/or fault rupture through aerial photos and geomorphological studies

The geomorphologic investigation yields information about specific topographic features (e.g. sharp ridges) and landforms of particular interest for microzoning purposes (e.g. paleo-hydrography elements). The geomorphological study is also a useful contribution to constrain earthquake ground shaking scenarios. The geomorphological study of the municipal area of about 182 km2 of Catania was performed through photo interpretation

The seismotectonics of the Po Plain (northern Italy): tectonic diversity in a blind faulting domain

We present a systematic and updated overview of a seismotectonic model for the Po Plain (northern Italy). This flat and apparently quiet tectonic domain is in fact rather active as it comprises the shortened foreland and foredeep of both the Southern Alps and the Northern Apennines. Assessing its seismic hazard is crucial due to the concentration of population, industrial activities and critical infrastructures, but it is also complicated because a) the region is geologically very diverse, and b) nearly all potential seismogenic faults are buried beneath a thick blanket of Pliocene-Pleistocene sediments, and hence can be investigated only indirectly. Identifying and parameterizing the potential seismogenic faults of the Po Plain requires proper consideration of their depth, geometry, kinematics, earthquake potential and location with respect to the two confronting orogens. To this end we subdivided them into four main homogeneous groups. Over the past 15 years we developed new strategies for coping with this diversity, resorting to different data and modeling approaches as required by each individual fault group. The most significant faults occur beneath the thrust fronts of the Ferrara-Romagna and Emilia arcs, which correspond to the most advanced and buried portions of the Northern Apennines and were the locus of the destructive May 2012 earthquake sequence. The largest known Po Plain earthquake, however, occurred on an elusive reactivated fault cutting the Alpine foreland south of Verona. Significant earthquakes are expected to be generated also by a set of transverse structures segmenting the thrust system, and by the deeper ramps of the Apennines thrusts. The new dataset is intended to be included in the next version of the Database of Seismogenic Sources (DISS; http://diss.rm.ingv.it/diss/, version 3.2.0, developed and maintained by INGV) to improve completeness of potential sources for seismic hazard assessment

Ups and downs in western Crete (Hellenic subduction zone)

Studies of past sea-level markers are commonly used to unveil the tectonic history and seismic behavior of subduction zones. We present new evidence on vertical motions of the Hellenic subduction zone as resulting from a suite of Late Pleistocene - Holocene shorelines in western Crete (Greece). Shoreline ages obtained by AMS radiocarbon dating of seashells, together with the reappraisal of shoreline ages from previous works, testify a long-term uplift rate of 2.5-2.7 mm/y. This average value, however, includes periods in which the vertical motions vary significantly: 2.6-3.2 mm/y subsidence rate from 42 ka to 23 ka, followed by ~7.7 mm/y sustained uplift rate from 23 ka to present. The last ~5 ky shows a relatively slower uplift rate of 3.0-3.3 mm/y, yet slightly higher than the long-term average. A preliminary tectonic model attempts at explaining these up and down motions by across-strike partitioning of fault activity in the subduction zone

A fresh look at the seismotectonics of the Abruzzi (Central Apennines) following the 6 April 2009 L'Aquila earthquake (Mw 6.3)

This work aims at providing an updated and augmented view of present-day tectonics and seismogenic sources of the Abruzzi Apennines, focusing on its extensional domain. This paper was spurred by the 6 April 2009, L’Aquila earthquake (Mw 6.3), an event from which geologists learned important lessons-including rather surprising ones. Although the earthquake was not major compared with other catastrophic events that occurred in Italy and elsewhere, this destructive earthquake led to a thorough review of the geometry – and style, in some instances – that characterises earthquake faulting in this region. The poorly expressed field evidence of the 6 April event, especially in light of the damage it caused in the mesoseismal area, stressed the intrinsic limitation of the earthquake geologists’ toolbox. Abruzzi is the region of a true “seismological paradox”: despite the rather long earthquake history available for the region, the number of potential sources for earthquakes of M ≥ 6.0 proposed in the literature is two to five times larger than the number of events that appear in the full earthquake record. This circumstance is made even more paradoxical by recent palaeoseismological work that proposed recurrence times of only a few centuries for individual seismogenic sources. Do the evident faults mapped by previous workers all correspond to potential seismogenic sources? We aim at addressing this paradox by drawing an updated seismotectonic model of Abruzzi based on the lessons learned following the 2009 earthquake. The model is based on selected geological, geomorphological, seismological, historical and geodetic data and will ultimately feed an updated version of the DISS database (http://diss.rm.ingv.it/diss/)

Is blind faulting truly invisible? Tectonic-controlled drainage evolution in the epicentral area of the May 2012, Emilia-Romagna earthquake sequence (northern Italy)

For decades alluvial plains have been the areas of fastest population growth over most of the globe. Modern societies demand growing extensions of flat and easily accessible land to accommodate swelling urban areas, booming industrial districts, large power plants, and multi-runway airports. But how can we tell if one of such flat areas hides large active faults? How can we assign a significant pre-instrumental earthquake to its causative source? In other words, how can modern societies deal with buried, that is to say, invisible faults, and with the elusiveness of the hazard they pose

WP8 Modelling of topographic signal: Detailed characterisation of individual structures

This deliverable will describe in detail results obtained during the project for four key areas of the Po Plain, the target area for the INGV contribution to the project. The four area are: 1) Coastal Marche region (southeastern Po Plain – see Section 1) 2) Mantova/Mincio River area (central Po Plain – see Section 2) 3) Mirandola/Secchia-Panaro Rivers area (southern-central Po Plain – see Section 3) 4) Soncino/Oglio River area (western Po Plain – see Section 4

Fault-trapped waves depict continuity of the fault system responsible for the 6 April 2009 MW 6.3 L’Aquila earthquake, central Italy

We investigate fault-trapped waves observed at a permanent broad-band station (FAGN) installed on the San Demetrio Fault, about 20 km southeast of L'Aquila. This fault has the same strike of the Paganica Fault which was responsible for the MW 6.3, 6 April 2009 earthquake. The two faults display an en-echelon pattern with a few km offset. We have found that events causing efficient trapped waves are clustered at the northwestern and southeastern bottom ends of the ruptured Paganica fault plane. The efficiency of trapped waves at FAGN, which is located about 5 km far from the ruptured fault plane, indicates that the two faults are linked at depth. This suggests that fault segments in the study area can be part of a longer and continuous fault system which controls the seismic hazard of the region. Moreover, we have found that the two earthquake clusters generating the most efficient trapped waves occur in portions of the fault system with the highest fluid pressure

Seismogenic sources of the Adriatic domain

We present an overview of the seismogenic source model of the Adriatic domain included in the latest version of the DISS database (http://diss.rm.ingv.it/diss/) and in the European SHARE database (http://diss.rm.ingv.it/SHARE/). The model consists of Composite and Individual Seismogenic Sources located inside and along the margins of the Adria plate. In order to locate and parameterize the sources, we integrated a wide set of geological, geophysical, seismological and geodynamic data, either available from published literature or resulting from our own field work, seismic profile interpretations and numerical modelling studies. We grouped the sources into five regions based on geometrical and kinematic homogeneity criteria. Seismogenic sources of the Central Western Adriatic, North-Eastern Adriatic, Eastern Adriatic and Central Adriatic regions belong to the Northern Apennines, External Dinarides and offshore domains, respectively. They are characterized by NWeSE strike, reverse to oblique kinematics and shallow crustal seismogenic depth. Seismogenic sources of the Southern Western Adriatic region instead are EeW striking, dextral strike-slip faults, cutting both the upper and lower crust. The fastest moving seismogenic sources are the most southern thrusts of the Eastern Adriatic and the strike-slip sources of the Southern Western Adriatic, while the seismogenic sources of the Central Adriatic exhibit the lowest slip rates. Estimates of maximum magnitude are generally in good agreement with the historical and instrumental earthquake records, except for the North-Eastern Adriatic region, where seismogenic sources exhibit a potential for large earthquakes even though no strong events have been reported or registered. All sources included in the database are fully geometrically and kinematically parameterized and can be incorportaed in seismic hazard calculations and earthquake or tsunami scenario simulations

Damage distribution and seismological model of the November 24, 2004, Salo' (Northern Italy) earthquake

The West side of lake of Garda, in Northern Italy, was struck by a ML=5.2 earthquake on November 24, 2004. The felt area is rather large (from Venice to Milan) and the damaged area consists of 66 municipalities, with a number of homeless of about 2200 and estimated direct damages of 215 millions of euros. Most of the damaged structures are old masonry buildings and churches, while there were almost no damage to reinforced concrete structures. The observed distribution of macroseismic intensity shows a strong azimuthal dependence, with high intensity level in a 10x10 km2 area located SW to the epicentre and rather large dispersion of values (ranging from V to VII-VIII) in the first 10 km epicentral distance. Taking into account the vulnerability level of the damaged structures and the features of the geological formations, we tried to explain the observed damage distribution in terms of finite fault properties of the source, despite the moderate magnitude of the event. Thus we hypothesised a fault geometry from seismotectonic considerations and we simulated the event by a high frequency simulation technique (Deterministic Stochastic Method, DSM). The synthetic ground motion parameters were converted into intensity values by empirical relationships and local geological conditions were considered to explain some discrepancies between simulated and observed intensities. It was possible to adequately reproduce both the observed distribution of macroseismic intensity and the ground motion recorded by an accelerometric station located at about 13 km epicentral distance

The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy’s earthquake geology

This paper describes the main characteristics, the evolution, and the structure of the Database of Individual Seismogenic Sources (DISS) and particularly of its release of early 2007. The Database contains the results of the investigations of the active tectonics in Italy during the past 20 years. The first two sections of this paper document the recent evolution in mapping and archiving Italian active fault data in relation to important achievements in the understanding of Italian tectonics, some of which were spurred by significant earthquakes. The central sections describe the current structure of the Database, the reasons for its assumptions and data categories, its current contents, its evolution through several years of improvements. The last section describes how the current contents of the Database correspond with the existing strain and stress data available from focal mechanism, borehole breakout, and GPS data for the whole of Italy. The Database supplies a fresh and unified view of active and seismogenic processes in Italy by building on basic physical constraints concerning rates of crustal deformation, on the continuity of deformation belts and on the spatial relationships between adjacent faults, both at the surface and at depth