Assessing the volcanic hazard for Rome. 40Ar/39Ar and In-SAR constraints on the most recent eruptive activity and present-day uplift at Colli Albani Volcanic District

We present new 40Ar/39Ar data which allow us to refine the recurrence time for the most recent eruptive activity occurred at Colli Albani Volcanic District (CAVD) and constrain its geographic area. Time elapsed since the last eruption (36 kyr) overruns the recurrence time (31 kyr) in the last 100 kyr. New interferometric synthetic aperture radar data, covering the years 1993–2010, reveal ongoing inflation with maximum uplift rates (>2 mm/yr) in the area hosting the most recent (<200 ka) vents, suggesting that the observed uplift might be caused by magma injection within the youngest plumbing system. Finally, we frame the present deformation within the structural pattern of the area of Rome, characterized by 50 m of regional uplift since 200 ka and by geologic evidence for a recent (<2000 years) switch of the local stress-field, highlighting that the precursors of a new phase of volcanic activity are likely occurring at the CAVD

40Ar/39Ar and 14C geochronology of the Albano maar deposits: Implications for 2 defining the age and eruptive style of the most recent explosive activity at Colli 3 Albani Volcanic District, Central Italy

New 40Ar/39Ar and 14C ages have been found for the Albano multiple maar pyroclastic units and underlying 25 paleosols to document the most recent explosive activity in the Colli Albani Volcanic District (CAVD) near 26 Rome, Italy, consisting of seven eruptions (Albano 1 27 ^ = ^ oldest). Both dating methodologies have been applied on several proximal units and on four mid-distal fall/surge deposits, the latter correlated, according to two 28 current different views, to either the Albano or the Campi di Annibale hydromagmatic center. The 40Ar/39Ar 29 ages on leucite phenocrysts from the mid-distal units yielded ages of ca. 72 ka, 73 ka, 41 ka and 36 ka BP, 30 which are indistinguishable from the previously determined 40Ar/39Ar ages of the proximal Albano units 1, 2, 31 5 and 7, thus confirming their stratigraphic correspondence. 32 Twenty-one 14C ages of the paleosols beneath Albano units 3, 5, 6 and 7 were found for samples collected 33 from 13 proximal and distal sections, some of which were the same sections sampled for 40Ar/39Ar 34 measurements. The 14C ages were found to be stratigraphically inconsistent and highly scattered, and were 35 systematically younger than the 40Ar/39Ar ages, ranging 36 ^ from 35 ka ^ to 3 ka. Considering the significant consistence of the 40Ar/39Ar chronological framework, we interpret the scattered and contradictory 14C ages 37 to be the result of a variable contamination of the paleosols by younger organic carbon deriving from the 38 superficial soil horizons. 39 These results suggest that multiple isotopic systems anchored to a robust stratigraphic framework may need 40 to be employed to determine accurately the geochronology of the CAVD as well as other volcanic districts. 4

Age–depth model of the past 630 kyr for Lake Ohrid (FYROM/Albania) based on cyclostratigraphic analysis of downhole gamma ray data

Gamma ray (GR) fluctuations and potassium (K) values from downhole logging data obtained in the sediments of Lake Ohrid from 0 to 240 m below lake floor (b.l.f). correlate with fluctuations in δ18O values from the global benthic isotope stack LR04 (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial-interglacial cycles, with high clastic input during cold and/or drier periods and high carbonate precipitation during warm and/or humid periods at Lake Ohrid. Spectral analysis was applied to investigate the climate signal and evolution over the length of the borehole. Linking downhole logging data with orbital cycles was used to estimate sedimentation rates and the effect of compaction was compensated for. Sedimentation rates increase on average by 14 % after decompaction of the sediment layers and the mean sedimentation rates shift from 45 cm kyr-1 between 0 and 110 m to 30 cm kyr-1 from 110 to 240 m b.l.f. Tuning of minima and maxima of gamma ray and potassium values versus LR04 extrema, in combination with eight independent tephrostratigraphical tie points, allows establishing of a robust age model for the downhole logging data over the past 630 kyr. © Author(s) 2015

Major explosive activity in the Monti Sabatini Volcanic District(central Italy) over the 800-390ka interval: Geochronological-geochemical overview and tephrostratigraphic implications

A review of the existing chronological, stratigraphic and chemo-petrologic data of the major eruptive units from the early phase of activity (800-390ka) in the Monti Sabatini Volcanic District (MSVD), belonging to the ultra-potassic magmatic region of central Italy, is presented along with new radioisotopic age determinations and geochemical analyses. Through the combined use of electron microprobe glass compositions, selected trace-element compositions, and single-crystal 40Ar/39Ar age determinations, we provide a new chrono- and chemo-stratigraphic classification of the products emplaced in the 800-390ka time interval. Besides giving insights on the petrologic evolution of the Roman Comagmatic Region, the large dataset provides fundamental information that is applicable to tephrostratigraphic studies in the wide region encompassing the Tyrrhenian Sea margin to the Adriatic Sea basin. Distal tephras from this volcanic activity also act as important geochronologic markers for the coastal sedimentary successions deposited in response to glacio-eustatic fluctuations, as well as for successions in the Quaternary tectonic basins of the Central and Southern Apennines. An innovative approach based on the use of discrimination diagrams of Zr/Y vs Nb/Y ratios for fingerprinting altered volcanic rocks - recently developed and successfully employed in archaeometric studies - is here combined to the glass compositions for classifying the MSVD deposits and tested on two distal tephra layers, showing its potentiality for tephrostratigraphic correlation. © 2014 Elsevier Ltd

Fagliazione normale attiva lungo il versante occidentale del Monte Morrone (Appennino Centrale, Italia)

L’Appennino Centrale è interessato da sistemi attivi di faglie normali potenzialmente responsabili di terremoti di elevata magnitudo (fino a 7). Alcuni forti terremoti storici avvenuti in questo settore di catena appenninica sono stati attribuiti all’attivazione di alcune di questi sistemi di faglia, mediante analisi paleosismologiche e il confronto fra la distribuzione del danneggiamento associato a tali eventi sismici e la distribuzione spaziale delle faglie attive. Ad alcune di queste strutture tettoniche attive, invece, non è possibile associare alcun evento sismico storico noti da catalogo e per questo esse vengono considerate come strutture sismogenetiche silenti. Pertanto, a queste faglie è comunemente attribuita un’elevata pericolosità sismica. Il presente studio è mirato a caratterizzare l’attività tardo-Quaternaria di una queste faglie silenti, nello specifico quella che borda il versante occidentale del Monte Morrone (nell’Appennino abruzzese), cercando di definirne 1) la cinematica, 2) il tasso di movimento e 3) la massima magnitudo attesa da un evento di attivazione. Le analisi (comprendenti rilevamento geologico, geomorfologico e strutturale, nonché datazioni al 14C e determinazioni tefrostratigrafiche) effettuate lungo l’espressione in superficie di questa struttura tettonica, costituita da due segmenti di faglia paralleli, orientati NW-SE, hanno permesso di confermare che essa è prevalentemente caratterizzata da una cinematica normale, con una minore componente obliqua sinistra. Tale cinematica sarebbe consistente con un’estensione orientata circa N 20°. Il tasso di movimento del segmento di faglia occidentale è stato definito mediante l’individuazioni di depositi (prevalentemente conoidi alluvionali), cronologicamente vincolati, dislocati dall’attività di tale segmento. Lo slip rate è risultato essere dell’ordine di 0.4±0.07 mm/anno. Per quanto concerne il segmento orientale, la sua attività tardopleistocenica – olocenica è indicata dalla dislocazione lungo di esso di depositi di versante attribuiti all’UMG. Tuttavia, la mancanza di sedimenti e/o morfologie coevi nel blocco di letto ha impedito di valutare il tasso di movimento di questo segmento. Tuttavia, le analisi geologico-strutturali effettuate, unite ad una revisione critica della letteratura disponibile sui modelli evolutivi dei sistemi di faglie normali, hanno permesso di ipotizzare per il segmento di faglia orientale uno tasso di movimento >0 ma inferiore a quello definito per il segmento occidentale, ossia <0.4±0.07 mm/anno. Questo consente di definire per l’intero sistema di faglie del Monte Morrone uno slip rate compreso fra 0.4±0.07 e 0.8±0.09 mm/anno. Infine, applicando le equazioni empiriche proposte da Wells e Coppersmith (1994) che legano la magnitudo momento e i) la lunghezza in superficie della struttura tettonica e ii) il rigetto (massimo e medio) per evento di attivazione – considerando un tempo di ricorrenza di circa 2000anni – è stato possibile definire che la massima magnitudo attesa da un terremoto originato lungo il sistema di faglie normali del Monte Morrone (lungo circa 23 km) è dell’ordine di 6.6-6.7

Fagliazione normale attiva e deformazioni gravitative profonde di versante: il caso del versante occidentale del Monte Morrone (Appennino Centrale, Italia)

Questo lavoro ha l’obiettivo di indagare la relazione fra l’attività tettonica e l’innesco di deformazioni gravitative profonde lungo i versanti montuosi. In base alla letteratura esistente, la tettonica può svolgere un duplice ruolo nell’influenzare l’evoluzione in senso gravitativo dei versanti: i) un ruolo passivo, legato all’influenza sull’assetto strutturale dei versanti che può essere ereditato da una fase tettonica non più attiva; ii) un ruolo attivo, rappresentato dalle modifiche che essa può determinare sui versanti, producendo incrementi dell’energia del rilievo e dello stress tensionale subito dai volumi di roccia. In quest’ottica è stato effettuato uno studio lungo il versante occidentale del Monte Morrone, rilievo che delimita ad oriente il bacino di Sulmona, nell’Appennino abruzzese, e che costituisce un’anticlinale da thrust formatasi durante il Mio-Pliocene. Questo versante del rilievo è interessato da un sistema attivo di faglie normali (orientato NW-SE), lungo circa 23 km, costituito da due segmenti di faglia paralleli, uno localizzato nel settore intermedio del versante e uno localizzato alla base del rilievo. Lungo questo versante sono state riconosciute in passato alcune morfologie – quali trincee, depressioni allungate, scarpate in contropendenza – indicanti l’occorrenza di movimenti gravitativi profondi (tipo sackung). Sono state condotte osservazioni geomorfologico-strutturali atte a mappare tutti gli elementi morfologici legati ai movimenti gravitativi profondi. Sono stati altresì realizzati 4 scavi geognostici all’interno di due trincee gravitative per cercare di ottenere elementi utili alla caratterizzazione dell’evoluzione recente di questi fenomeni gravitativi (Fig.1). Le analisi condotte hanno permesso di definire che tali fenomeni gravitativi di grande scala sono determinati dall’incremento dell’energia del rilievo prodotta dall’attività del segmento di faglia occidentale. La faglia orientale, invece, viene esclusivamente utilizzata, nella sua porzione più superficiale, come superficie di scivolamento delle masse rocciose. L’innesco dei fenomeni gravitativi sarebbe dunque avvenuto successivamente all’inizio dell’attività del segmento di faglia occidentale che, secondo Gori et al. (2007), avrebbe avuto luogo in un momento successivo all’attivazione del segmento orientale, dopo il Pleistocene Inferiore. Questo quadro evolutivo è suggerito dal fatto che la formazione di alcune delle trincee gravitative ha dislocato brecce di versante attribuite al Pleistocene Inferiore. Queste, infatti, si sono depositate su un paleo-paesaggio, attualmente individuabile fra i due segmenti di faglia, sospeso sulla piana attuale, che era localizzato alla base della scarpata di faglia relativa al segmento orientale, quando quello occidentale non era ancora attivo. La realizzazione di scavi geognostici all’interno di due trincee gravitative ha permesso di individuare la dislocazione dei depositi di riempimento lungo le scarpate che delimitano tali depressioni e lungo piani di taglio gravitativi secondari. I depositi messi alla luce dagli scavi sono prevalentemente costituiti da detrito di versante, sedimenti di origine colluviali e paleosuoli. Datazioni radiometriche effettuate su campioni di materiale organico prelevato dai paleosuoli e su frammenti di carbone contenuti nelle unità colluviali, indicano che i movimenti lungo le scarpate delle trincee è proseguito anche nel corso del tardo Olocene, nello specifico successivamanete a 10660-10540 cal. a.C./10430-9910 cal. a.C.. Questo indicherebbe che le deformazioni gravitative che interessano il versante occidentale del Monte Morrone possono considerarsi attive. Infine, anche se non sono state riconosciute chiare evidenze che mettano in relazione eventi di attivazione del sistema di faglie normali del M. Morrone con episodi di accelerazione dei movimenti gravitativi, questo non può essere escluso e, anzi, deve essere considerato come probabile

Fracture and failure of thermally damaged concrete under tensile loading

Concrete is a brittle composite material where the failure mechanism is closely related to the initiation and propagation of cracks. The presence of microcracks and other defects in concrete allows, unlike in the case of an ideal brittle material, the existence of a failure process that includes the branching and bifurcation of the cracks, which gives rise to the appearance of an inelastic behavior and then to a higher energy consumption during failure and an extension of the zone in which fracture takes place. This work studies the failure behavior of damaged concretes in tension and compares the behavior of concrete of different strength levels and component materials when adopting temperature as the damaging tool. Two water/cement ratios, two types of coarse aggregates and the incorporation of natural pozzolans are included as variables. As a way to evaluate the damage produced in the internal structure of concrete, the dynamic modulus of elasticity was measured on each specimen. Measures of strength, deformability, and fracture energy determined over notched prisms are reported. In a complementary way, the results of compression tests (strength, static modulus of elasticity, and Poisson ratio) over cylindrical specimens are included.Facultad de IngenieríaLaboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológic

Time intervals to assess active and capable faults for engineering practices in Italy

The time span necessary to define a fault as ‘active and capable’ can mainly be derived from the framework of the regulations and the literature produced since the 1970s on risk estimation in engineering planning of strategic buildings. Within this framework, two different lines of thought can be determined, which have mainly developed in the USA. On the one side, there is a tendency to produce ‘narrow’ chronological definitions. This is particularly evident in the regulatory acts for the planning of nuclear reactors. The much more effective second line of thought anchors the chronological definitions of the terms ‘active’ and, therefore ‘capable’, to the concept of ‘seismotectonic domain’. As the domains are different in different regions of the World, the chronological definition cannot be univocal; i.e., different criteria are needed to define fault activity, which will depend on the characteristics of the local tectonic domain and of the related recurrence times of fault activation. Current research on active tectonics indicates that methodological aspects can also condition the chronological choice to define fault activity. Indeed, this practice implies the use of earth science methods, the applications of which can be inherently limited. For example, limits and constraints might be related to the availability of datable sediments and landforms that can be used to define the recent fault kinematic history. For the Italian territory, we consider two main tectonic domains: (a) the compressive domain along the southern margin of the Alpine chain and the northern and northeastern margins of the Apennines, which is characterised by the activity of blind thrusts and reverse faults; and (b) the extensional domain of the Apennines and the Calabria region, which is often manifest through the activity of seismogenic normal and normal-oblique faults. In case (a), the general geomorphic and subsurficial evidence of recent activity suggests that a reverse blind fault or a blind thrust should be considered active and potentially capable if showing evidence of activity during the Quaternary (i.e., over the last 2.6 Myr), unless information is available that documents its inactivity since at least the Last Glacial Maximum (LGM) (ca. 20 ka). The choice of the LGM period as the minimum age necessary to define fault inactivity is related to practical aspects (the diffusion of the LGM deposits and landforms) and to the evidence that ca. 20 kyr to assess fault inactivity precautionarily includes a number of seismic cycles. In the extensional domains of the Apennines and Calabria region, the general geological setting suggests that the present tectonic regime has been active since the beginning of the Middle Pleistocene. Therefore, we propose that a normal fault in the Italian extensional domain should be considered active and capable if it displays evidence of activation in the last 0.8 Myr, unless it is sealed by deposits or landforms not younger than the LGM. The choice of the LGM as the minimum age to ascertain fault inactivity follows the same criteria described for the compressive tectonic domain

Central Mediterranean tephrochronology between 313 and 366 ka. New insights from the Fucino paleolake sediment succession

Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfinavolcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion 40Ar/39Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval

Aligning MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for core chronology

The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through marine isotope record. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed paleoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. In this paper, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically-dated Mediterranean marine and continental proxy records. The alternative age model obtained shows consistent differences with that proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how important a detailed study of independent chronological tie points is for synchronizing different records and to highlight asynchronisms of climate events