Damage as Gamma-limit of microfractures in anti-plane linearized elasticity

A homogenization result is given for a material having brittle inclusions arranged in a periodic structure. <br/> According to the relation between the softness parameter and the size of the microstructure, three different limit models are deduced via Gamma-convergence. <br/> In particular, damage is obtained as limit of periodically distributed microfractures

Bottleneck at Jaramillo for human migration to Iberia and the rest of Europe?

In the contemporary paleoanthropological literature, there is a general consensus that the earliest peopling of Europe occurred before the Brunhes–Matuyama geomagnetic polarity reversal at 0.78 Ma, based on convincing magnetostratigraphic evidence from Spain (e.g., Carbonell et al., 1995 and Parés and Perez-Gonzalez, 1999), Italy (Muttoni et al., 2011), and northern Europe (e.g., Parfitt et al., 2005). However, there is intense debate about how much before 0.78 Ma the earliest peopling occurred. Proponents of a long chronology claim that Europe was inhabited well before 1 Ma. There are sites that imply peopling of Europe before the Jaramillo normal geomagnetic polarity subchron (1.07–0.99 Ma; time scale of Lourens et al., 2004), even though the Jaramillo is nowhere to be found in these sections. Proponents of a shorter chronology (Muttoni et al., 2010, Muttoni et al., 2013 and Muttoni et al., 2014) put emphasis on the presence (or absence) of the Jaramillo in key hominin sections, while calling attention to large uncertainties in some of the other dating methods (biostratigraphic, ESR, cosmogenic), to infer that the earliest peopling of Europe occurred in a narrow time window of reverse polarity prior to the Brunhes–Matuyama boundary (0.78 Ma) but after the Jaramillo subchron (0.99–1.07 Ma). The Jaramillo has therefore attained the status of a marker datum useful for separating the long (>1 Ma) from the short (<1 Ma) chronology of the earliest peopling of Europe

The revision of the 30 October 1901 earthquake, west of Lake Garda (northern Italy)

On 24 November 2004 an earthquake (Mw 5.0) struck the west side of Lake Garda (northern Italy), producing moderate but widespread damage. It provided the opportunity of reviewing the seismicity of all the area over the past two centuries, whose former most significant event is the 30 October 1901 earthquake (Mw 5.5), while other minor but damaging events are the 5 January 1892 (Mw=5.0) and 16 November 1898 (Mw=4.6) earthquakes. On the reviewing we found common similarities in ground shaking distribution as recurrent damaged spots, amplification zones due to local site condition or energy radiation We believe that these findings are suitable to provide information for provisional purposes in low hazard level area hampered by the lack of knowledge about the seismic sources. New data are provided both in MCS scale and EMS. The sensitivity of a source parameters estimation technique was evaluated for the major event

Exhumation and update of a 25 year old data bank on the Messinian in Italy

The end product of a three years long research project on the distribution of Messinian age sediments in Italy, carried out by the Operational Unit 5.2.10 of the Progetto Finalizzato Geodinamica CNR, is represented by a data bank and a series of graphic outputs published in 1983 in a 467 pages long volume. Publication n. 514 described 610 subsurface sections from commercial wells and 245 measured sections from land. Outputs included graphic logs and a number of maps, originally produced at the scale of 1:1.500.000, showing the location of the sections or wells, the presence of the various units identified, and their thickness. Maps showing numerical data were presented as mean values per surface unit, each unit being 10’ x 10’ wide (~320 km2). Most of the data presented, with special reference to the commercial wells, were unpublished. But now, 25 years later, they may well be discussed openly, revealing their terrific geodynamic implications. The short duration of the Messinian Salinity Crisis (MSC), now astrochronologically calibrated with unprecedented precision (initiation of the crisis at 5.96 Ma, intra-Messinian unconformity at 5.62, initiation of the Lago-mare biofacies at 5.41 Ma, termination of the crisis at 5.33 Ma) in agreement with the 0.5 my estimated in 1983, is such that these computer generated maps can still provide a number of paleogeographic information and contain a strong geodynamic message. Important variations in thickness are recorded in the various lithologic units referred to the Messinian. Total thickness ranges from negative, where erosional gaps exist (i.e. at the foot of the Alps) to over 1000 m. High thicknesses are recorded in two different situations: at the depocenter of backarc and wedge-top evaporitic basins and in the Apennine foredeep, where sedimentation was essentially not evaporitic and/or with clastic gypsum. The top of the Messinian formations (the Miocene/Pliocene boundary) documented in wells and land outcrops has a vertical range in excess of 7000 m. The minimum elevation recorded is -5365 m a.s.l. in the area of the Po delta. The maximum elevation is 1806 m a.s.l. in central Apennines. In Sicily the elevation of the top of the Messinian (base of the Pliocene) ranges from -1156 m to 721 m a.s.l. (mean value per surface unit). A number of new information is now available as a result of exploration and/or production wells and surface exposures obtained in the last 25 years. We present an updated view for the northern Italy limited to the Po Pain and the southern border of the Alps. ENI geologists greatly contributed to the subsurface geology thanks to the interpretation of over 30000 km of seismic profiles and 1800 wells. New contributions include: − individuation of superimposed buried paleosols, indicative of different paleoclimate conditions in the Messinian succession cored in the Malossa field − persistent occurrence of dinoflagellates of paratethyian affinity (Galeacysta etrusca zone) in the post-evaporitic Messinian − evaluation of the Messinian sea level drop reconstructed by the geometry of the depositional architecture in the Venetian basin − new stratigraphic data from land exposures in the Venetian-Friulian Basin and in the Lake Garda area From a geodynamic point of view, the Po basin is the foredeep of the Apennine chain (accretionary complex) but it has been also the foreland basin of the south-verging Alps. In a broader geodynamic perspective the Mediterranean is a small ocean basin, that as a result of plate motions lost its connections with the Indian Ocean in Middle Miocene times, becoming an W-E elongated gulf tributary of the Atlantic Ocean. Being surrounded by orogenic belts active in Neogene times and crossed by the Maghrebian-Apenninic chain where it reaches its greater N-S width (~1200 km), the Mediterranean basin behaves as an amplifier of the climatic signal with occasional catastrophic episodes, as the MSC. The rate of deposition during the short-lived stage of maximum dessication was three order of magnitude greater than both prior and after the crisis. This is by far the greatest sea level drop registered in the entire history of our planet (1500 m in a few thousands years) causing the deposition of one million km3 of salts, the annihilation of the entire marine fauna living in the Mediterranean basin prior to its dessication, the deep entrenchment of the major rivers that had to adapt their course to the substantial change undergone by base level of erosion, the creation of erosional surfaces on the passive-type basin margins (as the south-verging Alps in Late Miocene times). The Adriatic sea is now the shallowest basin of the Mediterranean, but in Messinian times it was the deep, rapidly subsiding depocenter of the Apenninic foredeep. Its NW prolongation extended as far as the foot the Western Alps arc, in the Piedmont basin, some 600 km far from the present day coastline. There, the marine fossiliferous sediments of early Messinian and early Pliocene age indicate bathyal depths, but Messinian evaporites are recorded (in outcrops and/or in wells) only in the Apennine side. The Alpine margin is conversely characterized by erosional surfaces (sequence boundaries) and lacustrine sediments. The hydrologic budget that is now, and supposedly was in Messinian times, strongly negative in the Mediterranean basin, could well be positive in this northernmost portion, where the Alpine chain reached elevations even greater than the present ones, and the connection with the NNW-SSE trending sector of the Apennine foredeep was prevented by the “dorsale ferrarese” structure. The coherent picture deriving by the old, large data bank and the new acquisitions suggest that a lake was in existence in the depocenter of the Apenninic foredeep, with some connections with the Paratethyan basins to the east. The water table of the lake was some hundreds (300-500 m) meters below the level of the global ocean. Sedimentary composition indicates that the source area was from the north, not from the west (as it is nowadays). The same is true for the northern Adriatic, where provenance of the clastics is from the north (Eastern Alps), not from the west (Western and Central Alps). Recent studies proved that the influence of the Po drainage system likely started only in the early-middle Pleistocene. Lithogenesis, orogenesis, and morphogenesis are different processes that in general occur in successive phases. The Messinian events are so drastic and short-lived that their reconstruction requires a number of precise observational data but also a broad 3D perspective. Isopach map reconstructions are planned to reach the goal of a fully acceptable interpretation

Visual orbit for the low-mass binary Gliese 22 AC from speckle interferometry

Based on 14 data points obtained with near-infrared speckle interferometry and covering an almost entire revolution, we present a first visual orbit for the low-mass binary system Gliese 22 AC. The quality of the orbit is largely improved with respect to previous astrometric solutions. The dynamical system mass is 0.592 +- 0.065 solar masses, where the largest part of the error is due to the Hipparcos parallax. A comparison of this dynamical mass with mass-luminosity relations on the lower main sequence and theoretical evolutionary models for low-mass objects shows that both probably underestimate the masses of M dwarfs. A mass estimate for the companion Gliese 22 C indicates that this object is a very low-mass star with a mass close to the hydrogen burning mass limit.Comment: Accepted by Astronomy and Astrophysics, 6 pages, 2 figure

Korn's second inequality and geometric rigidity with mixed growth conditions

Geometric rigidity states that a gradient field which is $L^p$-close to the set of proper rotations is necessarily $L^p$-close to a fixed rotation, and is one key estimate in nonlinear elasticity. In several applications, as for example in the theory of plasticity, energy densities with mixed growth appear. We show here that geometric rigidity holds also in $L^p+L^q$ and in $L^{p,q}$ interpolation spaces. As a first step we prove the corresponding linear inequality, which generalizes Korn's inequality to these spaces

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