First observation of energetic neutral atoms in the Venus environment

The ASPERA-4 instrument on board the Venus Express spacecraft offers for the first time the possibility to directly measure the emission of energetic neutral atoms (ENAs) in the vicinity of Venus. When the spacecraft is inside the Venus shadow a distinct signal of hydrogen ENAs usually is detected. It is observed as a narrow tailward stream, coming from the dayside exosphere around the Sun direction. The intensity of the signal reaches several , which is consistent with present theories of the plasma and neutral particle distributions around Venus.     

Two unknown M > 6 historical earthquakes revealed by palaeoseismological and archival researches in eastern Calabria (southern Italy). Seismotectonic implications

The seismicity of Calabria is among the strongest in the whole of the Mediterranean, but is now well known on its Ionian side. Palaeoseismological investigations in eastern Calabria and archival research have tried to shed light on earthquake recurrence and seismogenetic source geometry. Trench investigation across the Lakes fault (Sila massif) shows this fault to be definitively responsible for the Mw = 6.7, 1638 earthquake, and provides a well‐constrained age range for its penultimate event (early 7th century AD). On the other hand, after research in local and national archives, another previously unknown relevant historical earthquake has been discovered (1744, Mw = 6.2), which struck an area conterminous to the SE tip of the Lakes fault. We hypothesize a NW–SE active Sila fault system that accommodates regional ～N–S extension through normal‐to‐sinistral segments, each one capable of generating earthquakes with magnitude in the range of 6.2–6.7. Since 1638, this system ruptured almost entirely from NW towards SE (1638–1744–1832), with the exception of the northwestern segment, the ‘silent’ Cecita fault.     

A search of cosmic-ray variations generated by pulsations of the heliosphere

Application of new statistical techniques to time series allow the investigation of cosmic-ray intensity variation in the periodicity range of 1 to 10 years. We can put significant levels to the existence of these oscillations and define their character as quasi-periodic and/or recurrent. Correlations between cosmic-ray intensity variations and solar activity changes during 1944–1979 are investigated. The two-year variation in cosmic rays is observed to be variable both in amplitude and phase, and not correlated with sunspot cyclic variations; but seems to depend on the magnetic polarity of the interplanetary medium. No significant evidence for the existence of longer period variations is obtained.     

Statistical Characterization of a Random Velocity Field Using Stacking Velocity Profiles

In petroleum exploration and production, it is important to have good estimations of the uncertainties on the reserves. Uncertainties in the velocity model used during the data processing are of major importance in this estimation. The use of geo-statistical tools can help in dealing with these uncertainties. Up to now, a strong limitation has been the inability to properly merge velocity functions measured in the wells with seismic velocity data. This was due to the different “supports” among the two, i.e. the well velocity may be regarded as a direct measurement of the instantaneous velocity field, while the seismic velocities correspond to an “average along the travelled paths” of this field. The problem is that, apart from the well positions, the instantaneous velocity field is out of reach. Luckily, for many practical applications, it is enough to know just its covariance model. However, no algorithmic method is available in the literature to yield the covariance model, and geologists are forced to use arbitrary distributions. The present paper proposes an original method to obtain a good estimate of this covariance model, using widely available information, mainly seismic stacking velocities. This method was first developed in a simple one-layer case with constant velocity, and then extended to more realistic situations. Finally, a real data application is performed, which highlights the robustness of the resulting estimation.     

Surface breaks along the coastal plain of Cirò (Ionian Calabria,southern Italy): geophysical and paleoseismological insights

On July 28, 2004, the coastal plain of Cirò (Calabria, Ionian Sea) was interested by the sudden opening of a ~5-km-long fracture, paralleling the coastline. All the buildings, roads, and pipelines crossed by the fracture were damaged, inducing several inhabitants to abandon their houses. The crack was 1–2-cm wide, downthrowing the seaward block up to 1–2 cm. This phenomenon is known for having already hit this area at least in the past century, both concurrently or not to earthquakes with epicentre far away from Cirò. In order to investigate the subsurface geometry, and the nature of the crack, we performed 5 electrical resistivity tomography and two paleoseismological trenches across it. The two methods provided evidences for the whole displacement of the local coastal succession, with offsets of several metres cumulated during the late Holocene. Giving the radiocarbon age of samples collected in trenches, we have constrained the dates of a couple of offset events which match some paleoearthquakes caused by the Lakes Fault, in the neighbouring Sila Massif. Excluding other possible causes (i.e. anthropic or tectonic), we are inclined to interpret these phenomena as the westernmost, surficial expression of a submarine deep-seated gravity sliding.     

Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton

We describe field occurrences of sapphirine-bearing granulites, charnockites and migmatites in the Gruf complex, Central Alps and present a new geological map and a structural analysis of the entire Gruf complex for the first time. We have carried out an accurate analysis of the relationships between granulite facies metamorphism, migmatisation and deformation within the complex, in relation to the intrusion of the Bergell pluton. Granulites and charnockites display fabrics different from those defined by the regional foliation and lineation, which are, typically for migmatites, disordered on the mesoscale. On a regional scale, strike variations are also related to the structural complexity of migmatites within which no major antiform could be identified. Irregular interfingering of sub-parallel leucosome veins and back-veining along the contact between the Gruf migmatites and the Bergell tonalite are evidence for contemporaneous emplacement and crystallisation at about 740 °C and 6.5–7.5 kbar in Oligocene times (ca 30 Ma). Metamorphic conditions in the charnockites and granulites (>920 °C for 8.5–9.5 kbar) largely exceed these regional metamorphic conditions and are dated at 282–260 Ma. We propose that the ascending Bergell pluton entrained the polymetamorphic, granulitic lower crust enclosed within the peripheral migmatitic Gruf complex.     

Hydrochemical and isotopic characterization of the hydrological budget of a MAB Reserve: Mar Chiquita lagoon,province of Buenos Aires,Argentina

Mar Chiquita is a coastal lagoon located in the Argentine Buenos Aires province in South America. The aim of this study was to perform a hydrochemical and stable isotopes characterization in order to better the understanding of the hydrology of the Mar Chiquita lagoon’s catchment and its water budget. Groundwater samples were taken from 144 wells and 21 samples from main streams, and seven lagoon water samples were also collected. Chemical analyses were carried out using standard laboratory methods, and isotopic determinations were made through laser spectroscopy using a DLT-100 liquid–water isotope analyzer. Hydrochemical analysis permits a general classification of groundwater and streamwater as sodium bicarbonate waters, while the lagoon chemical composition shows an evolution toward seawater composition, from the north to its mouth, which is located southerly. Isotopic data show a source of aquifer recharge from rainfall and a groundwater domain into the streams’ flow. Three main components can be recognized as end members in a plot of electrical conductivity (EC) versus δ¹⁸O: seawater, streamwater and groundwater. Obtained EC values for groundwater in the discharge zone (EC average value = 3,516 μS/cm) allow minimizing its direct contribution and to take into consideration two dominating end members: streamwater and seawater. Mar Chiquita lagoon’s water falls close to the line between streamwater and seawater end members according to its EC and δ¹⁸O. The obtained seawater proportion for these samples ranges from 84 % in the lagoon’s mouth to around 0 % in the more distal area.     

Twenty years of paleoseismology in Italy

Italy has one of the most complete and historically extensive seismic catalogues in the World due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the Iron Age. Seismic hazard studies have therefore always been mainly based upon this huge mass of data. Nevertheless, the Italian catalogue probably “lacks” many M ≥ 6.5 events, the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources. For these reasons, and as in other countries, earthquake data that in Italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment. Indeed, over the past 20 years, some hundred trenches have been excavated, supplying reliable and conclusive data on the recent activities of many faults. Through to many robust datings of surface fault events, these studies have provided the ages of several unknown or poorly known M ≥ 6.5 earthquakes. Here, we summarize the state of the art of paleoseismology in Italy, and present a first catalogue of 56 paleoearthquakes (PCI) that occurred mainly in the past 6 kyr. The PCI integrates the historical/instrumental seismic catalogue, and extends it beyond the recurrence time of the seismogenetic faults (2000 ± 1000 yr). We feel confident that the use of the PCI will enhance future probabilistic seismic hazard assessment, and thus contribute to more reliable seismic risk mitigation programs.     

Rotating magnetopolytropes: spherical figures of equilibrium due to balance of magnetic field and rotation

In this paper we compute spherical figures of equilibrium resulting from the balance of toroidal magnetic field and rotation. These two distortion effects are assumed to act on rotating magneto-polytropic constant-mass sequences, that is, sequences with each of their members having mass constant and equal to that of the corresponding nondistorted model.     

Three magnitude 7 earthquakes on a single fault in central Italy in 1400 years,evidenced by new palaeoseismic results

New palaeoseismic trenching across the main splay of the Fucino fault system provides evidence for a High Middle Age surface‐faulting episode conceivably associated with a disruptive earthquake, similar to the one that occurred in 1915 (Mw 7.0). The existence of this event, which has already been suggested by some previous studies, implies a shortening of the recurrence interval for Mw 7.0 earthquakes with respect to current knowledge. If we assume that the palaeoseismic Holocene record is complete, this shortening is focused in the historical period, when the Fucino structure sourced three strong earthquakes in only 1.4 ka. A similar clustering of energy release in the recent past is consistent with both palaeoseismological studies on other faults affecting the Apennine divide, and the high GPS strain rates observed in the same chain sectors.