Modelling of ground acceleration in the near source range: the case of 1976, Friuli earthquake (M = 6.5), northern Italy

A mixed statistical-deterministic model of earthquake rupture is developed for evaluating the strong ground motion in the near source range (receiver distance comparable to the fault length). The source parametrization is based on the k-square model and the propagation is computed by asymptotic Green's functions. The method is applied to the case of 1976, Friuli earthquake (M = 6.5) in northern Italy which occurred on a low-dip thrusting fault. Acceleration records at 29 stations are computed for 100 simulations of rupture histories. The mean value map of peak ground accelerations shows clearly a maximum to the south due to the inner geometry and directivity of the source. The variation of the estimated PGA versus the epicentral distance is strongly dependent on azimuth and is not decreasing monotonically. The comparison of these curves with those predicted by empirical acceleration–distance relationships shows discrepancies in the near source distance range. This study shows the importance of considering the complexity of the source rupture process for strong motion estimate in the near source range.     

Scaling of peak ground motions from digital recordings of small earthquakes at Campi Flegrei,southern Italy

The dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes (0.7<M _L<3.2) recorded digitally at distances of a few km in the Campi Flegrei volcanic area near Naples, Italy, during the ground uplift episode of 1982–1984. Numerical simulations, using the -square spectral model with constant stress drop and ane ^–kf high frequency decay, fit well both the velocity and acceleration data for an averagek=0.015. The observed ground motions in the 1–24 Hz frequency band appear to consist of radiation from simple sources modified only slightly by attenuation effects. Moreover, the scaling of peak values agrees closely with those determined in nonvolcanic areas, once the difference in stress drop is taken into account.     

Tectonic structure and post-Hercynian evolution of the Serre, Calabrian Arc, southern Italy: Geological, petrological and radiometric evidences

Conflicting opinions exist concerning the structure and the post-Hercynian evolution of the Serre. The present paper deals with these topics on the basis of new geological, petrological and radiometric evidence. The composition of the so-called Stilo and Polia-Copanello units has been redefined. The above domains—former sections of upper and lower Palaeozoic continental crust respectively—came into contact, due to transcurrent movements 130–140 Ma ago. A significant vertical component during the transcurrent movements, probably, exhumed the former section of lower crust. The above domains, juxtaposed, were successively involved as a single kinematic body in the Alpine orogenesis. The results enable us to make inferences for the Calabrian Arc evolution and call attention to similarities between an Austro-Alpine element (Stilo + Polia-Copanello) of the Calabrian chain and a South-Alpine sector of the Alps (Ivrea + Ceneri zones).     

Sulfide mineralogy in the polymetallic cassiterite deposits of Dachang,P.R. China

Several important mineral deposits of Sn, Zn, Cu, Pb, and other metals associated with Devonian sediments and Yanshanian (Cretaceous) granitic rocks are known in the Dachang district (Guangxi). Early genetic hypotheses related the origin of the deposits entirely to the Yanshanian granites. Recently, it was suggested that in Devonian times an earlier syngenetic metal concentration may have occurred, later overprinted by the Yanshanian metallogeny. This contribution is aimed at placing constraints on the physicochemical conditions during the Yanshanian ore formation-remobilization by studying the sulfide chemistry (arsenopyrite, sphalerite, stannite) and fluid inclusion data on the two major deposits in the area, i.e., the polymetallic cassiterite deposit of Changpo and the Zn-Cu skarn deposit of Lamo. Sphalerite and arsenopyrite are quite abundant in both deposits; stannite is minor, but fairly widespread at Changpo, and quite rare at Lamo. They are accompanied by pyrite, pyrrhotite, galena, chalcopyrite, cassiterite, fluorite, and a large variety of other sulfides and sulfosalts. The main compositional data for sphalerite and arsenopyrite are summarized as follows:Changpo: arsenopyrite associated with pyrrhotite 31.4–36.1 at% As; Associated with pyrite 31.9–33.1 at% As; sphalerite associated with pyrrhotite 18.3–22.2 mol% FeS; associated with pyrite 10.6–18.6 mol% FeS.Lamo: arsenopyrite associated with pyrrhotite 32.9–35.3 at% As; associated with pyrite 30.3–31.7 at% As; sphalerite associated with pyrrhotite, 17.2–24.4 mol% FeS; associated with pyrite 4.2–19.6 mol% FeS.Partitioning of Fe and Zn between coexisting sphalerite and stannite from Changpo indicates temperatures of 300°–350°C. For Lamo, the following fluid inclusion data are available: fluorite, salinities of 0–9.5 equiv. wt% NaCl, and homogenization temperatures between 160°C and 250°C; quartz, moderate salinities (0–4.6 equiv. wt% NaCl), and homogenization temperatures of 208°–260°C. Combining the mineralogical evidence with the compositional and fluid inclusion data, it is suggested that the evolution of the environment during the Yanshanian event was characterized by the following parameters: pressure was relatively low (on the order of 1–1.5 kb); temperature may have been as high as 500°C during deposition of the As-richest arsenopyrites, but eventually dropped below 200°–250°C in the latest stages; with an increase in sulfur activity and/or the decrease in temperature pyrrhotite was no longer stable in the latest stages of mineralization.     

Kinematical properties of early-type galaxies

Summary In the last decade, our understanding of early-type galaxies has greatly changed: from rather uninteresting oblate spheroids flattened by rotation to multicomponent stellar systems whose structure, formation mechanisms, and evolution, are far from being understood. This new scenario is mainly the consequence of the huge growth, in quantity and in quality, of kinematical data obtained from high signal to noise spectral data. Rotation curves and velocity dispersion profiles extending out to almost 2 effective radii are now available, together with line asymmetry measurements, for the stellar components of a fairly large sample of galaxies. For a few galaxies, outer halo tracers such as globular clusters and/or planetary nebulae allow to explore the kinematics out at 4 6r _e. In this article we focus on these data giving particular emphasis on the most recent results. Reference is given to other review articles complementing the approach presented here.     

Sensitivity Analysis on GIS Procedures for the Estimate of Soil Erosion Risk

Land degradation by water erosion is one of the majorissues in the field of environmental planning. Soilerosion and sediment transport are spatiallydistributed processes, and their evaluation can beeasily realised by means of the use of GeographicInformation Systems. The greater availability ofdigital and geo-lithological data managed and storedinside GIS has implied the development of techniquesand procedures aimed at the definition of the spatialprediction of erosion and deposition rates across acatchment. In this paper using terrain data measuredon an experimental basin in southern Italy, asensitivity analysis on different GIS-basedmethodologies for the estimate of a Length-Slope factorhas been developed with the aim of determining whichof these is more reliable for spatial erosion riskassessment. Specifically, by using the unit stream powertheory, different estimates are shown, depending on thescheme adopted to represent the hydrological andtopographic three-dimensional effects inside theLength-Slope factor. The performances of theprocedures analysed have been evaluated through theinformation content of the corresponding spatialdistributions, estimated as an entropy measure. Theresults obtained have shown that among the approachesutilised to describe the routing of the surface runoffalong the hillslope profiles, the two-dimensionalscheme appeared to be more realistic both on divergingand converging surfaces. Such a scheme, during thecomputational phases also aimed at distinguishing the areasof the basin experiencing net erosion from those areasexperiencing net deposition, resulted, being inaccordance with on-site investigations.     

Guidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project

Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V_S,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.     

Key factors affecting prediction of seismic pore water pressures in silty sands based on damage parameter

The paper provides insight into factors affecting the prediction of seismic pore-water pressure build up in clean sands and sand–silt mixtures for modeling purposes. Laboratory pore pressure measurements were conducted using stress-controlled undrained cyclic simple shear (CSS) tests carried out on both reconstituted and undisturbed specimens of silty sands under different initial conditions (density state, effective vertical stress, initial fabric and fines content). Test results were interpreted by using a damage concept-based model which is actually implemented for clean sands in non-linear time domain site response analysis codes. In the present work, such a model was properly modified for sands having fines contents higher than 35%. The general applicability of the modified procedure for predicting pore water pressure response of silty sands under irregular shear stress loading using data from stress-controlled CSS tests was also verified and all factors affecting calibration parameters of the model were throughly analyzed.