Modelling the long‐term deformation of the sedimentary substrate of Mt. Etna volcano (Italy)

This study investigates in detail the deformation events that have affected the sedimentary successions forming the substrate of Mt. Etna volcano (Italy). Based on the geometric reconstruction of a buried sedimentary marker, we have been able to identify and quantify the effects of three different mechanisms of deformation that have affected the area in the last 600 ka. Numerical results from Finite Element Method (FEM) applied to model viscoelastic deformation suggest the occurrence of a crustal doming process originating at the mantle‐crust transition (~16 km). We propose that the source of deformation is related to the diapiric uprise of hydrothermal material originating in altered ocean‐like crust and its emplacement at a shallower level in the crust. This process has great relevance in the volcanic system and should be considered for the full assessment of its origin and evolution.     

New gravity maps of the Eastern Alps and significance for the crustal structures

The deep seismic profile Transalp crosses, from north to south, Germany, Austria and Italy. The gravity measurements for each country were made by national agencies with different reference systems and data reduction methods. Within the frame of the Transalp-project a comprehensive database of the Eastern Alps was compiled covering an area of 3.5° by 4° in longitude and latitude (275 by 445 km), respectively. To increase the data coverage in the south Alpine area two gravity surveys were carried out, resulting in 469 areally distributed new stations, of which 215 have been measured with the intent to improve the geoid in the area of the planned Brenner Basistunnel (BBT). The resulting gravity database is the best in terms of resolution and data quality presently available for the Eastern Alps. Here the free air, Bouguer and isostatic gravity fields are critically discussed. The spatial density of existing gravity stations in the three countries is discussed. On the Italian side of the Alps the spatial density is rather sparse compared to the Austrian side. The Bouguer-gravity field varies between − 190 * 10^− 5 m/s² and + 25 * 10^− 5 m/s², with the minimum located along the Alpine high topographic chain, but with a small offset (a few tens of km) to the greatest topographic elevation, showing that the Airy-type local isostatic equilibrium does not fully apply here. The maximum of the Bouguer anomaly has an elongated shape of 100 by 50 km located between the towns of Verona and Vicenza and covers the Venetian Tertiary Volcanic Province (VTVP), a feature not directly related to the plate collision in the Eastern Alps. The gravity high is only partly explainable by high-density magmatic rocks and requires also a deeper source, like a shallowing of the Moho. The isostatic residual anomalies (Airy model) are in the range ± 50 * 10^− 5 m/s², with the greatest positive anomaly corresponding to the location of the VTVP, indicating here under-compensation of masses. At last a discussion of a 2D density model based on reflection seismic data and receiver functions is made.     

Toroidal path filter for orbital conjunction screening

For satellite conjunction prediction containing many objects, timely processing can be a concern. Various filters are used to identify orbiting pairs that cannot come close enough over a prescribed time period to be considered hazardous. Such pairings can then be eliminated from further computation to quicken the overall processing time. One such filter is the orbit path filter (also known as the geometric pre-filter), designed to eliminate pairs of objects based on characteristics of orbital motion. The goal of this filter is to eliminate pairings where the distance (geometry) between their orbits remains above some user-defined threshold, irrespective of the actual locations of the satellites along their paths. Rather than using a single distance bound, this work presents a toroid approach, providing a measure of versatility by allowing the user to specify different in-plane and out-of-plane bounds for the path filter. The primary orbit is used to define a focus-centered elliptical ring torus with user-defined thresholds. An assessment is then made to determine if the secondary orbit can touch or penetrate this torus. The method detailed here can be used on coplanar, as well as non-coplanar, orbits.     

Estimation of transmissivity and storage coefficient by means of a derivative method using the early-time drawdown

A novel methodology is proposed to calculate transmissivity (T) and storage coefficient (S) in a confined aquifer, based on the Theis (1935) solution and using only the first derivative of the drawdown with respect to time. By analyzing the behavior of the third derivative of the drawdown with respect to the logarithm of time, it is apparent that the third derivative vanishes when the first derivative attains its peak value. Since the third log-derivative is zero if, and only if, the argument, u, of the Theis well function is equal to unity, this condition can be used to estimate T and S, knowing the time at which the first derivative reaches its peak, and so overcoming the problem of actually computing the third log-derivative, which is very unstable. The main characteristic of the proposed method is that it does not require long pumping tests, since T and S are calculated using only the early-time drawdown. The proposed method was verified with a synthetic, an experimental and a field pumping test showing its validity when applied to homogeneous media. Theis CV (1935) The relation between lowering the piezometric surface and the rate and duration of discharge of a well using groundwater storage. Trans Am Geophys Union 16(2):519–524     

Cementation effects in two lacustrine clayey soils

This paper describes the main findings of a laboratory study on the mechanical behaviour of cemented geologically normally consolidated lacustrine clayey soils from two sites, Bacinetto (BA) and Avezzano (AZ), in the Fucino basin (Italy). One-dimensional and triaxial compression tests were carried out in order to investigate the effects of the presence and of the progressive degradation of the interparticle cementation bonds. The two tested soils showed quite different physical and mechanical properties, the more apparent ones being plasticity and yield stress values. The experimental results allowed the gross yield curves and the critical state conditions to be identified for both soils (BA clay and AZ silt). A number of typical features generally exhibited by cemented soils were clearly apparent: yield stresses greater than the in situ stress states, both soils being geologically normally consolidated; high values of compressibility index after yielding, which gradually reduce with increasingly applied stresses; strength reductions associated with a globally contractive behaviour. A convenient normalisation of the experimental results, in which the critical state conditions are assumed as a reference state, allowed the effects of cementation bonds and of their progressive degradation to be highlighted. In particular, BA samples were found to be characterised by different structures related to different degrees of cementation. Furthermore, despite the larger values of the yielding stresses exhibited by AZ silt, stronger effects of cementation are apparent in BA soil. Experimental results seem to indicate that at high values of the applied stress and strain paths, when bonds are largely damaged, the structures of the natural and parent reconstituted BA soil continue to be different.     

Fault-controlled Soil CO2 Degassing and Shallow Magma Bodies: Summit and Lower East Rift of Kilauea Volcano (Hawaii), 1997

Soil CO₂ flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower East Rift Zone of Kilauea volcano. Anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles. This result contrasts with what was recently observed on Mt. Etna, where most of the surveyed faults were associated with anomalous soil degassing. The difference is probably related to the differences in the state of activity at the time when soil gas measurements were made: Kilauea was erupting, whereas Mt. Etna was quiescent although in a pre-eruptive stage. Unlike Mt. Etna, flank degassing on Kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing East Rift eruption or in areas of the Lower East Rift where other shallow, likely independent reservoirs are postulated. Anomalous soil degassing was also found in areas without surface evidence of faults, thus suggesting the possibility of previously unknown structures. Received: November 2003, revised: January 2005, accepted: January 2005