recent dyke induced large scale block movement at mount etna and potential slope failure here we report the results of a geodetic survey undertaken on mount etna between 1981 and 1988 observed horizontal ground movements in the vicinity of the valle del bove caldera demonstrate that dyke emplacement during 1983 and 1985 resulted in the 2 8 m eastward displacement of a block of western caldera rim a history of past instability and collapse along the rim is indicated by the presence of large back rotated blocks of prehistoric volcanics1 furthermore the unusually linear form of the present western rim indicates past slope failure along north south aligned surfaces and therefore that dyke induced collapse may have been an important agent in caldera enlargement we suggest a self sustaining mechanism whereby the stress regime generated as a consequence of the caldera s existence results in the repeated injection of north south orientated dykes adjacent to the western rim2 3 dilation associated with magma intrusion leads in turn to periodic phases of slope instability and failure of the cliff wall causing a progressive westward migration of the western rim

a fractal approach to the temporal distribution of microseismicity at the low eastern flank of mt etna during 1989 1994 abstract seismicity affecting the low eastern flank of mt etna shows clustering in time we analysed a catalog of microearthquakes recorded by the four stations of the osservatorio sismologico di protezione civile di acireale during the period 1989 1994 in general a strong deviation from periodic and random distribution was found the temporal clustering is scale invariant and a fractal dimension can be derived to characterize it fractal dimensions seem to be correlated to the beginning of two major eruptions

exploration for dimensional stone implications and examples from the precambrian of southern finland dimension stone is a natural rock that must fulfil high qualitative standards defined by both geology based factors and non geological factors the stone itself appearance soundness and the market demand are the two most important aspects in the quality assessment the process of geological dimension stone exploration is a systematic and stepwise procedure including individual steps of desk study field mapping detailed examination geo radar survey and core drilling the location of all economically feasible dimension stone deposits is strictly controlled by geological factors knowledge of these factors is fundamental in identifying new sites with potential for dimension stone in this work the geological constraint on the occurrence of dimension stone in three areas in the precambrian of southern finland has been investigated the deposits are localized to part of an area in which different geological features in combination have produced rock of good dimension stone quality the study shows that for example vertical movements in the crust magmatic evolution of an intrusion and metamorphic grade define the location of rocks suitable for dimension stone

mt etna a model for the 1989 eruption abstract during the 1989 eruption of mt etna one of the most important in the last 20 years in terms of effusion rate a pair of fractures formed on the slopes of the southeast crater cone and propagated in a few days trending ca northeast and southeast with large quantities of magma being drained from the northern fracture in contrast the southern fracture after a short initial eruptive phase grew by 5 km in five days without eruptive or seismic activity when the fracture system crossed the southern scarp of the valle del bove wall some 6 km se of the active crater an intense seismic swarm started in the same area this lasted about four days and consisted of several hundred events clustering in a small focal volume although such a sequence of failure events contains elements of compatibility with a shallow dyke intrusion it did not lead to the expected flank eruption which would have threatened settlements just a few kilometres from the distal end of the fracture the question arises therefore whether or not the fracture system was dyke related and if so to what extent we attempt here to answer such a question by integration and interpretation of the available field observation and geophysical data indeed field observation constraints on the southern fracture system and the typical depth 2 km of the swarm do not contain evidence for shallow dyke emplacement beneath the lowermost part of the sse fracture conversely the inferred direction and shape of the tremor source the location and extent of a gravity anomaly observed a few months before the eruption the near horizontal migration of the seismic focii during the swarm and the change with time of related focal mechanisms lead us to hypothesize that the extreme development of the fracture system at its south was due to a deeper intrusion beneath the southern slope of the volcano

evidence of nonlinear elasticity of the crust from the mw7 6 manyi tibet earthquake satellite synthetic aperture radar sar interferometry shows that the magnitude 7 6 manyi earthquake of 8 november 1997 produced a 170 kilometer long surface break with up to 7 meters of left lateral slip reactivating a n76 e quaternary fault in western tibet the radar interferometric map reveals asymmetric along strike displacement profiles between the two sides of the surface rupture a pattern that cannot be explained with linear elastic theory this observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth a model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry a ratio that is consistent with laboratory and borehole measurements

decision criteria for the exploration of ornamental stone deposits application to the marbles of the portuguese estremoz anticline abstract ornamental stones are almost ready made raw materials with a high economic value for the building construction industry the discovery of new near surface deposits the very low exploitation efficiency the huge amounts of wastes produced and the land use accessibility conditions are the main challenges that the extractive industry for this mineral resource is facing nowadays research on advanced geological exploration tools and methodologies is needed to reply to those challenges during the process of geological ornamental stone deposits exploration the unique and decisive criteria that should be considered are its dimensions homogeneity and fracturing state lithostructural geological mapping and in situ fracturing surveys are the basic indispensable tools for their field assessment by applying these criteria and tools to a marble rich area in the portuguese estremoz anticline and a step by step numerical evaluation of the qualitative geological parameters the delimitation of the best target areas for exploitation or environmental rehabilitation has been effectively mapped

sustainable minerals operations in the developing world the sustainable development of minerals which are non renewable resources is a major challenge in today s world in this regard the true definition of sustainability is a debating point in itself can such a concept exist with respect to non renewable resources perhaps the ideal sustainability model is one that minimizes negative environmental impact and maximizes benefits to society the economy and regional national development developed and near developed economies rely for commodity supplies on developing countries where major mining operations are often a mainstay of the domestic economy limited environmental regulation and low wages lead to charges of exploitation also large numbers of people have no alternative to living by informal often dangerous artisanal mining this special publication gives examples from developing countries at all scales of mineral extraction the volume reviews environmental economic health and social problems and highlights the need to solve these before sustainability can be achieved the better solutions require mutual understanding through full involvement of all stakeholders education training and investment so that small scale ansd artisinal mines can grow into well managed operations at larger scales most major interantional mining companies have now inoproved their practices and are monitoring their progress although there is no room for complacency in this rapidly changing area

identifying seismicity patterns leading flank eruptions at mt etna volcano during 1981 1996 seismicity time properties of the etna volcano italy are investigated through a systematic pattern recognition analysis mean hypothesis testing mht has been applied to a long time database of instrumental data recorded from 1981 to 1996 to identify relevant correlation among seismic patterns main seismogenic volumes and the eight flank eruptions occured in the same period time evolution of the test statistic t ratio calculated on a temporal window starting 75 days prior to a volcanic eruption and extending 25 days after reveals that there is a pattern of seismic activity prior to the eruptions that can be used as a diagnostic tool as well as a physical modeling support in eruption forecasting

time clustering properties of seismicity in the etna region between 1874 and 1913 time properties of seismic activity of the etna volcano italy from 1874 to 1913 are investigated by fractal dimension analysis period selection was due to the interesting volcanic and seismic activity which had occurred within this time interval a catalogue was adopted revised by the reexamination of historical sources and with the addition of new material time evolution of the temporal fractal dimension dt calculated on a 40 seismic events moving window revealed the following correlations with the eruptive processes long term fractal dimension variations are due to the magma rise from the depth mid term variations are closely related to stress conditions at the volcano edifice and short term variations are induced by the onset of eruption the spatial localisation of data allowed interpretation of seismic activity in relation to the main structural systems outcropping on the volcano edifice and in the surrounding areas

new insights into the local crust structure of mt etna volcano from seismological and morphotectonic data abstract the reconstruction of the extensional active tectonic structures on the eastern flank of mt etna and of the related earthquakes allowed the analysis of fault parameters for more than 50 episodes of coseismic ground rupture for the last 250 years the calculation of statistical relationships among earthquake magnitude surface rupture length surface fault displacement and their combination was performed moreover we found out that the minimum earthquake magnitude to have ground rupture effect is ca 2 5 we were therefore able to hypothesize a reduced seismogenic layer 5 6 km under the lower eastern flank of the volcano we also analysed structural and marine geology data to find further surface evidences of the volcano dynamics we recognized for the first time a local component of uplift affecting the volcanic domain at least in the last 20 ka with a rate up to 3 5 mm yr that is likely related to a volcanic dome effect coupling the two aspects the seismological one and the morphostructural one of our research we propose a local thinning of the brittle crust in this sector of mt etna the thermal effects of the uprising magma on the rheology of the crust rocks well explain all our observations

evaluation of dimension stone in gneissic rocks a case history from southern finland abstract a dimension stone prospect in southern central finland was assessed by a detailed mapping geo radar survey and core drilling the prospect is a veined and bedded garnet cordierite gneiss consisting of a dark schistose medium grained palaeosome and a light coarse grained granitic leucosome both components are found mainly as thin units but the leucosome can occur as individual veins several metres thick which leads to disturbing variations in the appearance of the stone the soundness of the stone is defined by the amount of tight but open cracks in the palaeosome and weakness zones in the weathered leucosome as a whole the soundness is diminished down to 10 m below the outcrop surface furthermore a subhorizontal body of younger granite is identified at approx 8 20 m depth consequently the prospect is not feasible for production of dimension stone the core drilling was decisive in the final evaluation of the prospect because the true density of the cracks and the subsurface granite were identified by the method only with the use of core drilling could the proper interpretation of the characteristics of the prospect be made demonstrating the importance of three dimensional investigation of a dimension stone prospect

petrology and sr nd isotope geochemistry of recent lavas from mt etna bearing on the volcano feeding system abstract the volcanic activity of mt etna during the period 1971 1987 has been investigated based on new volcanological petrographic geochemical and isotopic data the magma output rate since 1971 is much higher than that of the last 200 years marking a significant change in the feeding regime of mt etna the highest output rate has been observed for the 1981 eruption sub aphyric lavas emitted during the excentric activity of 1974 are the most primitive of those studied mg 57 55 the major and trace element chemistry of the lavas indicates limited differentiation by crystal fractionation mainly involving mafic phases nevertheless the observed variability of some ratios between highly incompatible elements suggests possible source heterogeneities the sr nd isotopic compositions range between 0 70362 0 70377 and 0 512829 0 512892 respectively with the lowest and highest 87sr 86sr ratios measured in the 1981 and 1974 lavas the observed isotopic variability is not due to late contamination processes but probably to the mantle source variations in sr and nd isotopic composition could indicate the lack of large magma chambers at any level in mt etna feeding system suggesting a model in which magma reaches the surface through a network of dikes where complete homogenization of different batches cannot be attained

time correlation analysis of the microseismicity of the low eastern flank of mt etna volcano italy an analysis in terms of time correlation functions has been applied to the time distribution of microseismicity we considered the single station detections m 2 recorded by each one of the four working stations of the network of the osservatorio sismologico di protezione civile acireale catania located on the active faults systems timpe of the low eastern flank of mt etna information obtained on the time regularity of seismic crisis and on the time correlation between the activities recorded by different stations allowed a better understanding of the role of the two main structures the timpa di santa tecla is the most seismogenic structure in the area and probably played a role in the magma transfer process for the 1989 eruption modifications of the local stress field by actions of this feature may have produced gravitational instability along a second structural system the timpa di s leonardello with a time delay of about 100 days by contrast magma penetration associated with the larger eruption of 1991 1993 had a deeper rise system and had no effect on local stress conditions consequently there was no correlation between volcanism and seismicity

geological constraints on the paleozoic tectonic evolution of tectonostratigraphic terranes in the iberian massif abstract the presence of oceanic paleozoic sequences in the iberian variscan fold belt is used to identify and separate suspected exotic terranes from a reference iberian autochthon terrane which constitutes the greater part of it in this paper the relevant data characterizing the pre accretionary evolution of the paleozoic iberian terranes are presented as well as the available evidence concerning the accretionary process itself emphasis is placed on the analysis of the sedimentary igneous and structural expression of the major events which affected the iberian terranes before during and after their amalgamation the main conclusions of such an analysis may be summarized as follows 1 a recognition of rift and passive margin stages in all the iberian massif terranes during the early paleozoic 2 b late paleozoic accretion of the exotic terranes to the iberian autochthon via a long and complex process variscan orogeny which involved initial subduction underneath the latter and eventual obduction followed by oblique collision of a promontory the iberian autochthon northwestern margin with a northwestern continental block this latter process could account for the large scale crustal imbrication shown by the northern branch of the orogen coeval with predominant strike slip faulting in the southern branch as well as with the formation of the typical arcuate shape of this orogenic belt major present uncertainties relate to the palinspastic provenance of continental suspect terranes and their correlation with similar units in other circum atlantic paleozoic orogens a discussion and speculations on this subject are dealt with in the final section of this paper

transcurrent continental tectonics model for the ossa morena zone neoproterozoic paleozoic evolution sw iberian massif portugal the ossa morena zone sw iberian massif was affected by continuous orogen parallel transcurrent continental tectonics from the neoproterozoic to the carboniferous times involving transtension tt and transpression tp processes that co existed together occurred separately in neighbouring regions by the means of strain partitioning or even worked diachronically a first stage of transpression tp1 took place during the late neoproterozoic lower cambrian as a result of cadomian arc continent collisional processes structures generated by transtension tt1 from cambrian to lower devonian were related to strong lithosphere stretching responsible for the development of basins controlled by major detachments tilting rifting and important tectono thermal diachronic processes denudation phenomena and inhibition of sedimentation related with thermal uplift asthenosphere upwelling and consequent subsidence caused by isostatic equilibrium involving generalized transgressions were processes responsible for major unconformities the variscan tp2 tt2 episodes that followed diachronically tp1 tt1 by maintaining the orogen parallel transport direction were concomitant with syntectonic deposition of continental basins in the omz and foreland basins in the spz tt2 local transtension and tectonic exhumation of deep crustal rocks along major shear zones favoured the opening of tectonic troughs filled up by sediments and volcanism tp2 shortening have generated fold axes parallel to the orogen strike and composite dissymmetric flower structures

time seismicity patterns affecting local and regional fault systems in the etna region preliminary results for the period 1874 1913 an analysis of time correlation function and fractal dimension has been performed on the seismic activity that affected mt etna volcano italy during 1874 1913 in order to investigate the behaviour of some suspected magma controlling regional fault systems the time span considered has been characterized by intense seismic and volcanic activity with eight flank eruptions mainly occurring along the same north south fissure system the analysis of historical sources has been used to revise and improve the seismic catalogue all macroseismic information has been reinterpreted using the new european macroseismic scale 1998 ems the results contribute to the definition of the seismic behaviour of some regional fault systems relevant to the geodynamics of the area and provide some insights into the dynamic processes of mt etna volcano

upwards migration of seismic focii a forerunner of the 1989 eruption of mt etna italy data from a portable array of three component digital stations run at mt etna from 1988 to early 1990 highlight the seismic behaviour of the volcano before the 1989 eruption one of the most significant in terms of energy of the last two decades after a two year period of weak and discotinuous seismicity the depth of the seismically active volumes was observed to become shallower a few months before the volcanic event the overall migration of the events inferred by hypocentral locations and decreases of s p time differences at two stations agrees with other geophysical forerunners and allows further insights into the changes in the stress field leading to the eruption

evaluation of the quality of a granite quarry abstract the determination of the quality of a mass of granite with a view to its exploitation for ornamental purposes is carried out by means of the identification of the geological geotechnical and aesthetic factors that characterize the granite in order to draw up an optimal exploitation method for any given granite deposit an assessment of the relationship existing between these factors and the quality of the block is of the utmost importance using as a starting point data based on the observation of these factors at an extraction bank a simple linear index was elaborated using multivariant techniques permitting the classification of each block in terms of quality subsequently using geostatistical techniques the index is applied to areas of the extraction bank for which there are no a priori data with a view to predicting possible areas of maximum quality included is a description of an application whereby the quality of a granite quarry was evaluated on the basis of 569 observations at an extraction bank the methodology developed may be considered an objective quality evaluation method applicable to ornamental rock quarries

identifying and discriminating seismic patterns leading flank eruptions at mt etna volcano during 1981 1996 abstract seismicity affecting mt etna volcano italy has been investigated in order to identify and discriminate seismic patterns precursory to flank eruptions an intense period 1981 1996 of seismicity and volcanism during which eight flank eruptions occurred has been considered two statistical methods are used mean hypothesis testing and entropic decision trees the results of the two methods are consistent and reveal a pattern of deep and western events prior to the flank eruptions that can be used as a predictive tool as well as a physical modeling constraint

review of seismological studies at mount etna this paper reports the present state of seismological research at mt etna a schematic classification of the earthquakes that occur on the volcano is proposed based on both seismogram and spectrum features we have made both focal solutions and estimates of earthquake source parameters stress drop values between 2 and 20 bars and small source dimensions the crust of etna thus appears as an extremely heterogeneous medium that does not permit great stress accumulation the coexistence of an extensional regime with an older and deeper compressive one seems confirmed at depths greater than about 7 km eruptive and seismic phenomena occur mainly along the principal structural trends of the volcano but often the directions of the eruptive fractures and the earthquake concentration during the same eruption do not coincide tectonics seem to play an important role in controlling seismo volcanic behaviour