Early capture of a central Apennine (Italy) internal basin as a consequence of enhanced regional uplift at the Early-Middle Pleistocene Transition

Extensional tectonics in the inner portion of the central Apennines began during the Late Pliocene-Early Pleistocene. It resulted in the formation of chain-parallel normal fault systems, whose activity through the Quaternary led to the formation of intermontane tectonic basins; these represented traps for continental sedimentary sequences. In particular, during the Early Pleistocene most of the central Apennine depressions hosted lakes, testifying to endorheic hydrographic networks. Afterwards, lacustrine environment was replaced by fluvial regimes, aged at the Middle Pleistocene, as the hydrographic systems of the basins were captured by headward regressive erosion coming from the outermost sectors of the chain. This is testified by a strong erosional phase that cut into the lake sequences, due to deepening of streams and river incisions, and the subsequent deposition of embedded fluvial deposits. This environmental change is commonly attributed to a regional relief enhancement, as a consequence of the increase of regional uplift of the central Apennines (and geologically seen in many parts of the Apennine chain), generically aged between the upper part of the Early Pleistocene and the lower part of the Middle Pleistocene [e.g. D’Agostino et al. 2001]. The Subequana Valley and Middle Aterno Valley are part of a cluster of Quaternary tectonic depressions distributed along the current course of the Aterno River - here termed the Aterno basin system - which also includes the L’Aquila and Paganica-Castelnuovo-San Demetrio basins to the north, and the Sulmona basin to the south. They are located in innermost sector of the central Apennines, in correspondence of the chain divide. These basins are hydrographically connected by the Aterno river, one of the moste important fluvial basins of the “Adriatic domain” which runs south-easterly along the eastern side of the Subequana basin and Middle Aterno Valley, flows to the Sulmona basin through the San Venanzio gorges, where it joins to the Pescara river. The depressions are bounded towards the NE by an active normal fault system that led the formation and the tectonic evolution of the basins [Falcucci et al. 2011]. The analysis of the early Quaternary geological evolution of this depression can represent a significant case study to refine the knowledge of the Early-Middle Pleistocene tectonic/environmental transition, especially in terms of timing, taking into account that uplift rate is defined as having been larger along the chain divide. We integrated geological, geomorphological, paleomagnetic and radiometric dating with the 40Ar/39Ar method to reconstruct the morpho-stratigraphic setting of the Subequana Valley-Middle Aterno river system, defining the paleo-environmental features and chronology of the depositional and erosive events that have characterised the Quaternary geological and structural evolution of these basins. In detail, a synchronous lacustrine depositional phase was recognised in the Subequana basin and the Middle Aterno Valley. Paleomagnetic analysis performed along some sections of these deposits exposed in the Subequana valley attested a reverse magnetisation, reasonably related to the Matuyama Chron. The lacustrine sequence of the Subequana valley passes upwards to sand and gravel, testifying for the infilling of the lake and the onset of a fluvial regime that displays a direction of the drainage towards the north, i.e. opposite to the present Aterno river flow. At the topmost portion of the lake deposits, two subsequent tephra layers were identified and dated by means of 40Ar/39Ar method, at ~890ka, for the lower tephra, and ~805ka for the upper one. It is worth noting that a “short” direct magnetisation event occurred just above the lower tephra, whose significance is still under investigation. This data constraints the infilling of the lake in the Subequana valley very close to the Early-Middle Pleistocene transition. Subsequent to the infilling of the Subequana basin, a fluvial regime, characterised by a northward drainage direction – i.e. opposite to the current one –, was established. Then, after a strong erosional phase, the presence of a new coeval fluvial depositional phase within the Subequana Valley and the Middle Aterno Valley, with flow direction towards the south-east, indicates the formation of a paleo-Aterno. We identified a further fluvial sequence, embedded within the lacustrine sequence through an evident erosional surface. These deposits are found at the northern part of the Subequana valley, where they laterally pass to fluvial deposits that crop out at the southern part of the Middle Aterno river valley; this sequence shows a flow direction consistent with the current direction of the Aterno river. This morpho-stratigraphic setting, schematized in Fig. 1, indicates that after an intense erosional phase, which dissected the lake sequence, the Subequana-Middle Aterno river valley system has been hydrographically connected by the course of a paleo-Aterno river; this river flowed southerly, towards the San Venanzio gorges.Such morpho-stratigraphic interpretation is corroborated by geological observations performed in the Sulmona basin. At the outlet of the Aterno river, we found slope derived breccias, commonly attributed to the Early Pleistocene, that lay over the bedrock Their depositional geometry suggests that the breccias deposited when the Aterno river thalweg was not present yet, that is when the Subequana Valley was hosting a lake and no drainage was hydrographically connecting the valley to the Sulmona basin. Then, an alluvial fan body unconformably overlays the breccias; the fan, suspended over the Aterno river thalweg, was fed by a stream incision coinciding with the paleo-San Venanzio gorges. Lastly, a fluvial deposit is found embedded within the breccias and the alluvial fan, sourcing from the San Venanzio gorges as well. A tephra layer was found interbedded to the sedimentary body. The volcanic deposit was related to the “Pozzolane Rosse” eruption of the Colli Albani district, dated at 456±4 ka BP [Galli et al. 2010]. This fluvial deposit indicates the presence a paleo-Aterno river flowing from the Subequana valley. Therefore, the described morpho-stratigraphic framework, and the obtained chronological elements constrain the capture of the endorheic hydrographic network of the Subequana valley-Middle Aterno Valley during a time span comprised between ~800ka and ~450ka. In this perspective, it is worth noting that endorheic hydrographic networks of other basins (e.g. the Leonessa basins) located along the innermost portion of the central Apennine chain were captured during the same time span by headward erosion of streams and rivers related to the “thyrrenian hydrographic system” [e.g. Fubelli et al 2009]. This provides new elements for unravelling coupling between river incision potential and capability, and the Apennine chain uplift

insights into bedrock paleomorphology and linear dynamic soil properties of the cassino intermontane basin central italy

Abstract Seismic amplifications are dictated by the depth of the bedrock and the stratigraphy and dynamic properties of the soil deposits. Quantifying these properties, together with their uncertainty, is a necessary task to perform a reliable assessment of the seismic risk at an urban scale. In this paper, a multidisciplinary analysis is presented, where information of different nature is combined. Borehole logs, geophysical, geological and geotechnical surveys are interpreted with the aid of analytical, numerical and geostatistical techniques to characterise the complex shape of the bedrock and the linear dynamic properties of the sedimentary deposits filling the Cassino basin, a Quaternary intermontane basin located in central Italy. The regional and local seismic hazard is firstly identified with geological surveys that reveal an active seismogenic fault capable of producing earthquakes with estimated magnitudes up to 6.5. Boreholes reaching depths variable up to a maximum of 180 meters and microtremor measurements, revealing the sharp impedance contrast at the transition between the sedimentary/arenaceous bedrock and the soft Quaternary infilling, are combined to identify the depth of the bedrock and the linear dynamic properties of soil deposits. These are one of the key factors governing the propagation to the ground level of seismic waves, and their assessment represents the first step for the seismic hazard characterisation of the plain

Cosesimic liquefaction phenomena from DInSAR after the May 20, 2012 Emilia earthquake

In this paper, we have investigated the capability of Differential Interferometry Synthetic Aperture Radar (DInSAR) technique to detect the ground effects induced by liquefaction phenomena occurred during the May 20, 2012 Emilia earthquake. To this aim, a set of COSMO-SkyMed (CSK) SAR images covering the coseismic phase has been used. The detected surface effects have been related to liquefaction of deep sandy layers. Thanks to the geological/geotechnical data in the area and a liquefaction susceptibility analysis of the subsoil, it has been identified a sandy layer between 9 and 13 m in deep, which probably liquefied during the earthquake. The estimated vertical displacements due to liquefaction are comparable with the values measured by DInSAR.Published5-95T. Sismologia, geofisica e geologia per l'ingegneria sismicaN/A or not JC

Surface Faulting Caused by the 2016 Central Italy Seismic Sequence: Field Mapping and LiDAR/UAV Imaging

The three mainshock events (M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016) in the Central Italy earthquake sequence produced surface ruptures on known segments of the Mt. Vettore-Mt. Bove normal fault system. As a result, teams from Italian national research institutions and universities, working collaboratively with the U.S. Geothechnical Extreme Events Reconnaissance Association (GEER), were mobilized to collect perishable data. Our reconnaissance approach included field mapping and advanced imaging technique, both directed towards documenting the location and extent of surface rupture on the main fault exposure and secondary features. Mapping activity occurred after each mainshock (with different levels of detail at different times), which provides data on the progression of locations and amounts of slip between events. Along the full length of the Mt. Vettore-Mt. Bove fault system, vertical offsets ranged from 0-35 cm and 70-200 cm for the 24 August and 30 October events, respectively. Comparisons between observed surface rupture displacements and available empirical models show that the three events fit within expected ranges.Published1585-16104T. Sismicità dell'ItaliaJCR Journa

New insights into earthquake precursors from InSAR

We measured ground displacements before and after the 2009 L’Aquila earthquake using multitemporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.Published120356T. Variazioni delle caratteristiche crostali e precursoriJCR Journa

Active and capable fault? The case study of Prata D'Ansidonia (L'Aquila, Central Apennine)

The study deals with the morphogenetic meaning of several linear scarps that carved the paleo-landsurface of Valle Daria, an extended geomorphological feature located between Barisciano (AQ) and Prata D'Ansidonia (AQ). These villages are situated in the southern termination of the L'Aquila intermontane basin (one of the largest basin of the central Apennines), nearby the epicentral area of the 6th April 2009 earthquake (Mw 6.1). These scarps, up to 3 meters high and up to 1.5 km long, define narrow/elongated flat-bottom depressions, filled by colluvial deposits. These depressions are carved into fluvial-deltaical conglomerates, dated back to the lower Pleistocene. Even if different authors have interpreted these shapes as a paleodrainage or secondary faults, a morphometrical study of the Valle Daria paleo-landsurface provided several information which cast doubt on these two interpretations. In order to better understand the nature and the state of activity of these lineaments, geological, geomorphological and geophysical surveys were carried out. A paleoseismological trench pointed out two events of deformation. The curvilinear shape of the shear plane seems to be related to a slow deformation, attributable to collapse-phenomena. Three GPR profiles, two ERT profiles and two microgravimetrical profiles seem to corroborate this interpretation. Therefore, this study permits to attribute the genesis of these scarps to tectono-karstic phenomena, excluding the presence of an active and capable fault.Published346-3494T. Sismologia, geofisica e geologia per l'ingegneria sismicaN/A or not JC

Engineering Reconnaissance Following the October 2016 Central Italy Earthquakes - Version 2

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. Each event was followed by numerous aftershocks. As shown in Figure 1.1, this earthquake sequence occurred in a gap between two earlier damaging events, the 1997 M6.1 Umbria-Marche earthquake to the north-west and the 2009 M6.1 L’Aquila earthquake to the south-east. This gap had been previously recognized as a zone of elevated risk (GdL INGV sul terremoto di Amatrice, 2016). These events occurred along the spine of the Apennine Mountain range on normal faults and had rake angles ranging from -80 to -100 deg, which corresponds to normal faulting. Each of these events produced substantial damage to local towns and villages. The 24 August event caused massive damages to the following villages: Arquata del Tronto, Accumoli, Amatrice, and Pescara del Tronto. In total, there were 299 fatalities (www.ilgiornale.it), generally from collapses of unreinforced masonry dwellings. The October events caused significant new damage in the villages of Visso, Ussita, and Norcia, although they did not produce fatalities, since the area had largely been evacuated. The NSF-funded Geotechnical Extreme Events Reconnaissance (GEER) association, with co-funding from the B. John Garrick Institute for the Risk Sciences at UCLA and the NSF I/UCRC Center for Unmanned Aircraft Systems (C-UAS) at BYU, mobilized a US-based team to the area in two main phases: (1) following the 24 August event, from early September to early October 2016, and (2) following the October events, between the end of November and the beginning of December 2016. The US team worked in close collaboration with Italian researchers organized under the auspices of the Italian Geotechnical Society, the Italian Center for Seismic Microzonation and its Applications, the Consortium ReLUIS, Centre of Competence of Department of Civil Protection and the DIsaster RECovery Team of Politecnico di Torino. The objective of the Italy-US GEER team was to collect and document perishable data that is essential to advance knowledge of earthquake effects, which ultimately leads to improved procedures for characterization and mitigation of seismic risk. The Italy-US GEER team was multi-disciplinary, with expertise in geology, seismology, geomatics, geotechnical engineering, and structural engineering. The composition of the team was largely the same for the two mobilizations, particularly on the Italian side. Our approach was to combine traditional reconnaissance activities of on-ground recording and mapping of field conditions, with advanced imaging and damage detection routines enabled by state-of-the-art geomatics technology. GEER coordinated its reconnaissance activities with those of the Earthquake Engineering Research Institute (EERI), although the EERI mobilization to the October events was delayed and remains pending as of this writing (April 2017). For the August event reconnaissance, EERI focused on emergency response and recovery, in combination with documenting the effectiveness of public policies related to seismic retrofit. As such, GEER had responsibility for documenting structural damage patterns in addition to geotechnical effects. This report is focused on the reconnaissance activities performed following the October 2016 events. More information about the GEER reconnaissance activities and main findings following the 24 August 2016 event, can be found in GEER (2016). The objective of this document is to provide a summary of our findings, with an emphasis of documentation of data. In general, we do not seek to interpret data, but rather to present it as thoroughly as practical. Moreover, we minimize the presentation of background information already given in GEER (2016), so that the focus is on the effects of the October events. As such, this report and GEER (2016) are inseparable companion documents. Similar to reconnaissance activities following the 24 August 2016 event, the GEER team investigated earthquake effects on slopes, villages, and major infrastructure. Figure 1.2 shows the most strongly affected region and locations described subsequently pertaining to: 1. Surface fault rupture; 2. Recorded ground motions; 3. Landslides and rockfalls; 4. Mud volcanoes; 5. Investigated bridge structures; 6. Villages and hamlets for which mapping of building performance was performed

Reconnaissance of 2016 Central Italy Earthquake Sequence

The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster

The origin of scarps in urban areas affected by active and capable normal faulting: only faults? Examples from the 2009 L’Aquila earthquake region (central Italy)

We present the results of geological investigation and multi-temporal aerial pho- tographs analysis performed in the southern epicentral area of the 2009 L’Aquila earthquake; here, some geomorphic hints of active normal faulting are reported in the available literature, and based on which seismotectonic models are proposed. Our investigations pointed out that the supposed signatures of faulting are instead related to other natural or anthropogenic processes. Moreover, our study highlights that landforms supposed to be or actually related to structural features cannot be utilised tout court for active fault mapping in areas where many processes, togeth- er to or other than tectonics, concur to sculpt the landscape.PublishedTorino2T. Tettonica attivarestricte

Le fasi di colluviamento tardoantiche nel Piano della Civita e la fine della frequentazione dell'abitato di Alba Fucens. Atti del Convegno in memoria di Joseph Mertens.

L’evidenza di abbandono di un abitato antico successivamente ad un forte terremoto porta logicamente ad ipotizzare una relazione diretta tra i due eventi. Ciò vale tanto più in riferimento all’età tarda, considerando che la catastrofe naturale potrebbe inserirsi in un quadro di decadenza preesistente dell’insediamento. Un’ipotesi come questa potrebbe toccare Alba Fucens, ove sono chiare e numerose le evidenze del terremoto tardoantico e ancora più chiaro è il fatto che l’insediamento, a un certo punto della sua storia e successivamente al terremoto, fu abbandonato. Tuttavia, su un piano generale, è opportuno sottolineare che la tesi secondo cui l’abbandono di un abitato antico sia da riferirsi esclusivamente a un forte terremoto deve essere sottoposta ad analisi di più ampia prospettiva. Queste devono coinvolgere aspetti difficilmente quantificabili, come gli effetti sulla popolazione del venir meno del tessuto urbanistico ed edilizio o – in senso ancora più ampio – la risposta delle società antiche alle ovvie ricadute economiche a scala locale o al cambiamento del tessuto relazionale con il territorio pure sinistrato. Le informazioni archeologiche relative ad Alba Fucens sembrano alimentare l’ipotesi della continuità abitativa su un ampio arco cronologico plurisecolare che include il momento dell’evento sismico, secondo il modello generale dello sviluppo “verticale”, in situ, degli abitati antichi periodicamente afflitti dalle conseguenze dei terremoti distruttivi, suggerito – a esempio – nel lavoro di Ambraseys (2005). In effetti, già Mertens (1991) citò le evidenze stratigrafiche di una continuità della vita nell’abitato di Alba colpito dal terremoto1, seppure con modalità precarie. Tali evidenze possono essere affiancate i) alle tracce di continuità abitativa tra Tarda Antichità e Alto Medioevo discusse nei più recenti lavori di Redi (2001) e Tulipani (2006) e ii) al ritrovamento di resti di strutture abitative tarde o altomedievali nel piazzale antistante il santuario di Ercole nelle ultime campagne di scavo (2008-2009). Sono altresì compatibili con la fonte che cita l’accampamento di militari bizantini durante la guerra gotica (Procopio, Bell. Goth., II, 7). Tutte 1 - Tale evento sismico è attributo da Mertens (1991) al IV secolo d.C.; in precedenza, l’autore (Mertens, 1981) aveva riferito di “catastrofi che si abbatterono sulla città alla fine del IV e nel corso del V secolo”. Il terremoto è invece attribuito al V-VI secolo da Galadini (2006) e Galadini et al. (2010). 2 evidenze e vicende apparentemente successive al terremoto distruttivo. Sembra pertanto chiaro che le ragioni dell’abbandono definitivo e completo dell’abitato storico non siano da riferirsi soltanto agli effetti – diretti e forse nemmeno indotti e di lungo periodo – dell’evento sismico tardoantico. In questo articolo, dopo una breve sintesi sullo stato delle conoscenze relative al terremoto che nella Tarda Antichità colpì Alba Fucens, si fornirà un’interpretazione sull’origine dei sedimenti che ricoprivano i resti archeologici prima delle attività di scavo. Tali successioni, risultanti dai processi sedimentari naturali e culturali che hanno interessato l’area dell’abitato antico, saranno descritte in dettaglio nell’Appendice 1. Nella prospettiva di questa analisi, sembra utile segnalare che, dal punto di vista geomorfologico, il Piano della Civita – area che ospita i resti attualmente visibili della città – si deve considerare come una sorta di piccolo bacino, cioè come un’entità fisiografica naturalmente predisposta alla sedimentazione, in funzione delle condizioni al contorno, rappresentate sostanzialmente dalla stabilità dei versanti adiacenti. L’interpretazione in termini di modalità deposizionale delle varie unità stratigrafiche che riempivano il Piano della Civita e la definizione dell’età della sedimentazione forniranno spunti per meglio definire la storia ambientale del sito e i suoi effetti sull’insediamento di Alba Fucens.Not submitted3.10. Storia ed archeologia applicate alle Scienze della TerraN/A or not JCRrestricte