Analysis of the liquefaction phenomena in the village of Vittorito (L��Aquila)

This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila earthquake (moment magnitude M_w = 6.3), approximately 45 km far from the epicentre. In the document, first, an estimation of the seismic motion in the area has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave velocity V_s and horizontal stress index K_D. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the area, produced by the L’Aquila earthquake, was very low.     

Model evaluation experiments in the North Atlantic Basin: simulations in nonlinear terrain-following coordinates

A primitive equation ocean circulation model in nonlinear terrain-following coordinates is applied to a decadal-length simulation of the circulation in the North Atlantic Ocean. In addition to the stretched sigma coordinate, novel features of the model include the utilization of a weakly dissipative, third-order scheme for tracer advection, and a conservative and constancy-preserving time-stepping algorithm. The objectives of the study are to assess the quality of the new terrain-following model in the limit of realistic basin-scale simulations, and to compare the results obtained with it against those of other North Atlantic models used in recent multi-model comparison studies.The new model is able to reproduce many features of both the wind-driven and thermohaline circulation, and to do so within error bounds comparable with prior model simulations (e.g., CME and DYNAMO). Quantitative comparison with comparable results obtained with the Miami Isopycnic Coordinate Model (MICOM) show our terrain-following solutions are of similar overall quality when viewed against known measures of merit including meridional overturning and heat flux, Florida Straits and Gulf Stream transport, seasonal cycling of temperature and salinity, and upper ocean currents and tracer fields in the eastern North Atlantic Basin. Sensitivity studies confirm that the nonlinear vertical coordinate contributes significantly to model fidelity, and that the global inventories and spatial structure of the tracer fields are affected in important ways by the choice of lateral advection scheme.     

Salt Waters of the Northern Apennine Foredeep Basin (Italy): Origin and Evolution

The salt waters from the Emilia-Romagna sector of the Northern Apennine Foredeep have been investigated using major and trace element and stable isotope (δ²H, δ¹⁸O, δ³⁷Cl, δ⁸¹Br and ⁸⁷Sr/⁸⁶Sr ratio). Ca, Mg, Na, K, Sr, Li, B, I, Br and SO₄ vs. Cl diagrams suggest the subaerial evaporation of seawater beyond gypsum and before halite precipitation as primary process to explain the brine’s salinity, whereas saline to brackish waters were formed by mixing of evaporated seawater and water of meteoric origin. A diagenetic end-member may be a third component for mud volcanoes and some brackish waters. Salinization by dissolution of (Triassic) evaporites has been detected only in samples from the Tuscan side of the Apennines and/or interacting with the Tuscan Nappe. In comparison with the seawater evaporation path, Ca–Sr enrichment and Na–K–Mg depletion of the foredeep waters reveal the presence of secondary processes such as dolomitization–chloritization, zeolitization–albitization and illitization. Sulfate concentration, formerly buffered by gypsum-anhydrite deposition, is heavily lowered by bacterial and locally by thermochemical reduction during burial diagenesis. From an isotopic point of view, data of the water molecule confirm mixing between seawater and meteoric end-members. Local ¹⁸O-shift up to +11‰ at Salsomaggiore is related to water–rock interaction at high temperature (≈150°C) as confirmed by chemical (Mg, Li, Ca distribution) and isotopic (SO₄–H₂O) geothermometers. ³⁷Cl/³⁵Cl and ⁸¹Br/⁷⁹Br ratios corroborate the marine origin of the brines and evidence the diffusion of halogens from the deepest and most saline aquifers toward the surface. The ⁸⁷Sr/⁸⁶Sr ratio suggests a Miocene origin of Sr and rule out the hypothesis of a Triassic provenance of the dissolved components for the analyzed waters issuing from the Emilia-Romagna sector of the foredeep. Waters issuing from the Tuscan side of the Apennines and from the Marche sector of the foredeep show higher ⁸⁷Sr/⁸⁶Sr ratios because of the interaction with siliciclastic rocks.     

Velocity and runout simulation of destructive debris flows and debris avalanches in pyroclastic deposits,Campania region,Italy

The Campanian Apennines are characterized by the presence of monocline ridges, mainly formed by limestone. During the periods of volcanic activity of the Somma-Vesuvius and Phlegrean Fields, the ridges were mantled with pyroclastic materials in varying thickness. The pyroclastics have been involved in destructive landslides both in historical time and in the recent past (1997, 1998, 1999). The landslides occur following intense and prolonged rainfalls. In some cases, landslides extended up to 4 km into the surrounding lowlands and reached towns, causing severe destruction and over 200 deaths. Generally, the landslides begin as small debris slides that develop into large, shallow debris avalanches or debris flows involving pyroclastic horizons and colluvial soils (0.5–2 m thick) on steep and vegetated slopes, often at the heads of gullies. During motion, the landslide materials eroded vegetation and soils from the slope, so that the moving material volume tended to increase. Then, proceeding towards and beyond the base of the slopes, the phenomena evolved into hyperconcentrated streamflow due to dilution by incorporating water. The results of motion analyses are described. An empirical rheological relationship was used including two principal terms that depend on the total normal stress and on the flow velocity. On this basis, the model has simulated the velocity and duration of debris avalanches and the distribution of the deposits. The selected areas were those of Sarno/Quindici and Cervinara, where a large amount of data is available both on the material properties and geomorphological setting. It was found that the majority of the cases at the two sites can be simulated successfully with only one specific pair of rheologic parameters. This provides the possibility for first-order predictions to be made of the motion of future landslides. Such predictions will be a valuable tool for outlining potential hazard areas and designing remedial measures.     

The February 2010 large landslide at Maierato, Vibo Valentia, Southern Italy

A large landslide formed at Maierato (Vibo Valencia District), Southern Italy, on 15 February 2010, at 1430?hours local time, when rapid failure occurred after several days of preliminary movements. The landslide has an area of 0.3?km², a runout distance of 1.2?km and an estimated volume of about 10?Mm³. The landslide caused nearly 2,300 inhabitants to be evacuated, with high economic losses. The most probable trigger of the landslide was the cumulative precipitation over the preceding 20?days (having a return period of more than 100?years), which followed a long period of 4?C5?months of heavy rainfall (of about 150% of the average rainfall of the period). This report presents a summary of our findings pertinent to the landslide??s activities based on our field investigations. In particular, this report covers (1) details of land deformation caused by the landslide, (2) geology pertinent to landslide development, (3) identification of the landslide mechanism and its triggering factors based on the analysis of the boring core specimens and landform features, as well as the available video of the event, and (4) preliminary evaluation of the stability of the original slope before the landslide using the finite element-based shear strength reduction method. The aim of the paper was to describe the landslide and explain its mechanism of occurrence.     

Flexural uplift of a lithospheric slab near the Vema transform (Central Atlantic): Timing and mechanisms

The Vema Transverse Ridge (VTR) is a prominent, long and narrow topographic anomaly that runs for over 300 km along a sea floor spreading flow line south of the Vema transform at 11° N in the Atlantic. It rises abruptly about 140 km from the axis of the Mid-Atlantic Ridge (MAR) in 10 Myr old crust and runs continuously up to 25 Myr old crust. It reaches over 3 km above the predicted lithospheric thermal contraction level. It is absent in crust younger than 10 Myr; thus, the uplift of the VTR must have ended roughly 10 Ma. The VTR is interpreted as the exposed edge of a flexured and uplifted slab of oceanic lithosphere that was generated at an 80 km long MAR segment. Based on satellite gravimetry imagery this MAR segment was born roughly 50 Ma and increased its length at an average rate of 1.6 mm/yr. Multibeam data show that the MAR-parallel sea floor fabric south of the VTR shifts its orientation by 5° to 10° clockwise in 11–12 Myr old crust, indicating a change at that time of the orientation of the MAR axis and of the position of the Euler rotation pole. This change caused extension normal to the transform, followed between 12 and 10 Ma by flexure of the edge of the lithospheric slab, uplift of the VTR at a rate of 2 to 4 mm/yr, and exposure of a lithospheric section (Vema Lithospheric Section or VLS) at the northern edge of the slab, parallel to the Vema transform. Ages of pelagic carbonates encrusting ultramafic rocks sampled at the base of the VLS at different distances from the MAR axis suggest that the entire VTR rose vertically as a single block within the active transform offset. A 50 km long portion of the crest of the VTR rose above sea level, subsided, was truncated at sea level and covered by a carbonate platform. Subaerial and submarine erosion has gradually removed material from the top of the VTR and has modified its slopes. Spreading half rate of the crust south of the transform decreased from 17.2 mm/yr between 26 and 19 Ma to 16.9 mm/yr between 19 and 10 Ma, to 13.6 mm/yr from 10 Ma to present. The slowing down of spreading occurred close in time to the change in ridge/transform geometry, suggesting that the two events are related. A numerical model relates lithospheric flexure to extension normal to the transform, suggesting that the extent of the uplift depends on the thickness of the brittle layer, consistent with the observed greater uplift of the older lithosphere along the VTR.     

Types of eruptions of Etna volcano AD 1670–2003: implications for short-term eruptive behaviour

Analysis of the historical records of Etnas eruptive activity for the past three centuries shows that, after the large 1669 eruption, a period of about 60 years of low-level activity followed. Starting from 1727, explosive activity (strombolian, lava fountaining and subplinian) at the summit crater increased exponentially to the present day. Since 1763, the frequency of flank eruptions also increased and this value remained high until 1960; afterward it further increased sharply. In fact, the number of summit and flank eruptions between 1961 and 2003 was four times greater than that of the pre-1960 period. This long-term trend of escalating activity rules out a pattern of cyclic behaviour of the volcano. We propose instead that the 1670–2003 period most likely characterises a single eruptive cycle which began after the large 1669 eruption and which is still continuing.On the basis of the eruptive style, two distinct types of flank eruptions are recognised: Class A and Class B. Class A eruptions are mostly effusive with associated weak strombolian activity; Class B eruptions are characterised by effusive activity accompanied by intense, long-lasting, strombolian and lava fountaining activity that produces copious tephra fallouts, as during the 2001 and 2002–2003 eruptions. Over the past three centuries, seven Class B eruptions have taken place with vents located mainly on the south-eastern flank, indicating that this sector of the volcano is a preferential zone for the intrusion of volatile-rich magma rising from the deeper region of the Etna plumbing system.Electronic Supplementary Material Supplementary material is available for this article at Editorial responsibility: M. Carroll     

On the MHD Acceleration of Astrophysical Jets

We present a 2.5D magnetohydrodynamic (MHD) simulation of the acceleration of a collimated jet from a magnetized accretion disk. We employ a MHD Adaptive Mesh Refinement (AMR) code (FLASH—University of Chicago). Thanks to this tool we can follow the evolution of the system for many dynamical timescales with a high-spatial resolution. Assuming an initial condition in which a Keplerian disk, thus with no accretion motions, is threaded by a uniform poloidal magnetic field, we show how both the accretion flow and the acceleration of the outflow occur, and we present in detail which are the forces responsible for the jet launching and collimation. Our simulation also shows how the collimating forces due to the self-generated toroidal magnetic field can produce some peculiar knotty features.     

The imaging and slitless spectroscopy instrument for surveys (ISSIS) for the world space observatory-ultraviolet (WSO-UV)

ISSIS is the Imaging and Slitless Spectroscopy Instrument for the World Space Observatory-Ultraviolet (WSO-UV) mission. ISSIS is a multipurpose instrument designed to carry out high resolution (<0.1 arcsec) imaging in the far UV with fields of view ≥2×2 arcmin². ISSIS has two acquisition channels: the High Sensitivity Channel (HSC) and the Channel for Surveys (CfS). The HSC is equipped with an MCP-type detector to guarantee high sensitivity in the 1150–1750 ? range and high rejection of lower energy radiation. The CfS is equipped with a large CCD detector (4k×4k) to obtain images from the far UV to the red (1150–8500 ?); the CfS is implemented to allow observing UV bright sources such as reflection nebulae or nearby massive star forming regions. The design drivers and the current status of the instrument are described in this contribution.