evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

sand volcano generated by a violent degassing from methane saturated aquifers the case study of medolla modena italy abstract sand volcano is an unusual and remarkable geological feature which forms when water saturated sand deposits are set in motion by liquefaction and are ejected onto the surface commonly it is generated during earthquakes as a result of liquefaction of waterlogged bodies at shallow depth often causing wide damages the generation of a sand volcano however can also occur unrelated to a seismic event on the 10th of october 2014 near medolla italy during a cone penetration test a large amount of natural gas co2 and ch4 together with a mixture of water and sand were erupted creating a sand volcano the study of this event gives the possibility of understanding the dynamics of sand volcano generation may enable to prevent other anomalies during future cpt tests and more importantly underlines the role that natural gas stored in a sand aquifer may play in triggering a liquefaction phenomenon our results suggest that episodes of gas eruptions require the onset of very peculiar conditions within the reservoir that feeds the emission the simulations suggest that a geyser discharging a mixture of gas and water capable of building a sand volcano requires the presence of a shallow pressurized reservoir 1 2 mpa where water coexists with a small amount of exsolved gas a volume fraction of 0 05 the violent degassing occurred in medolla confirms the role that a free gas phase may have in favoring the mobilization of liquid water and loose deposits even in the absence of a seismic event

stratigraphic and kinematic modeling of thrust evolution northern apennines italy we present a quantitative kinematic model of thrust evolution that allows detailed interpretation of the stratigraphic record of foreland basins simulation of thrusting and syntectonic sedimentation shows that changes in the relative rate of thrusting and mode of thrust activation can be determined by their expression in basin stratigraphy truncations and offlaps reflect thrust activity and hinterland migration of basin depocenters indicates out of sequence thrusting forward modeling of the stratigraphic record of the pliocene quaternary po basin italy enables the quantitative reconstruction of the displacement sequence of the thrust sheets prograding into the basin during the pliocene deep seated middle pliocene thrusting accompanied by out of sequence thrusting provides a consistent explanation for the observed stratigraphic record of the po piggyback basins

brittle failure mode plots for compressional and extensional tectonic regimes abstract equations governing different macroscopic modes of brittle rock failure extensional fracturing extensional shear fracturing compressional shear failure and reshear of existing faults can be represented on plots of differential stress vs effective vertical stress for a set of material properties such plots can be constructed for different tectonic regimes and correlated to depth for particular fluid pressure conditions allowing easy evaluation of the physical controls on brittle rock failure and ready comparison of the fields occupied by the three failure modes in different tectonic settings they emphasize the relative ease in terms of differential stress and fluid pressure levels of deforming a rock mass by brittle fracturing and faulting in extensional regimes compared with compressional aside from their relevance to general structural mechanics these generic failure plots have wide ranging application to understanding the initial development and progressive evolution of fault fracture systems both in sedimentary basins and as hosting structures for hydrothermal mineralization in different tectonic settings

the tectonic regime in italy inferred from borehole breakout data abstract in italy the horizontal stress directions are well constrained in many regions but the tectonic regime is not well known because the stress magnitudes are unknown our intention is to improve the knowledge of crustal stress in italy both at shallow depth and in low seismicity areas therefore we inferred the tectonic regime from the comparison between the depth of breakout occurrence and the physical properties of the rocks in 20 boreholes the critical value of the maximum horizontal stress for which the effective tangential stress at the borehole wall overcomes the rock strength to form breakouts could be computed from rock strength and density comparing the theoretical stress distributions for different tectonic regimes with the depth distribution of breakout occurrence it is possible to infer the tectonic regime that fits best to the breakout depth distribution we investigated boreholes up to 6 km deep located in different tectonic environments over the italian peninsula the po plain the apenninic chain the adriatic foredeep and the tyrrhenian quaternary volcanic region these wells are characterised by breakout data of good quality a b and c according to world stress map quality ranking system the results are in general agreement with the style of faulting derived from earthquake focal mechanisms and other stress indicators our results show a predominance of a normal faulting nf regime in the inner apennines and both normal faulting and strike slip faulting ss style in the surrounding regions possibly also associated with changes in the tectonic regime with depth

compaction induced stress variations with depth in an active anticline northern apennines italy 1 it is shown that the stress field can vary with depth even within a homogeneous tectonic setting as documented for the active mirandola fault related fold along the buried front of the northern apennines analyses of borehole breakouts and other well data integrated with seismological information and field evidence show that extension perpendicular to the fold axis above approximately 1200 m changes to a strike slip stress field and finally to compression near the main detachment at depth similar along depth strain variations recognized in non active anticlines are usually explained by invoking tangential longitudinal strain folding i e stretching above and shortening below a neutral surface or gravitational instabilities however in this study we propose that differential compaction may play a significant and generally overlooked role with the aid of numerical modeling it is shown that where fold limbs are onlapped by highly compactable deposits as in the mirandola area differential compaction induces stretching at shallow 1 2 km depths the amount of stretching is a function of the shape of the fold and of the thickness of the syn tectonic sediments we conclude that in the mirandola case study the stress variations observed with depth are the result of a combination of a regional compression at depth and local tension driven by differential compaction of growth strata on the limbs of the anticline with respect to its crest

thermal decomposition along natural carbonate faults during earthquakes earthquake slip is facilitated by a number of thermally activated physicochemical processes that are triggered by temperature rise during fast fault motion i e frictional heating most of our knowledge on these processes is derived from theoretical and experimental studies however additional information can be provided by direct observation of ancient faults exposed at the earth s surface although fault rock indicators of earthquake processes along ancient faults have been inferred the only unambiguous and rare evidence of seismic sliding from natural faults is solidified friction melts or pseudotachylytes here we document a gamut of natural fault rocks produced by thermally activated processes during earthquake slip these processes occurred at 2 3 km depth along a thin 0 3 1 0 mm principal slip zone of a regional thrust fault that accommodated several kilometers of displacement in the slip zone composed of ultrafine grained fault rocks made of calcite and minor clays we observe the presence of relict calcite and clay numerous vesicles poorly crystalline amorphous phases and newly formed calcite skeletal crystals these observations indicate that during earthquake rupture frictional heating induced calcite decarbonation and phyllosilicate dehydration these microstructures may be diagnostic for recognizing ancient earthquakes along exhumed faults

recent and active tectonics of the external zone of the northern apennines italy we present a comprehensive study of the recent and active tectonics of the external part of the northern apennines italy by using morphotectonic geological structural and stratigraphic analysis compared with the current seismicity of the region this analysis suggests that the external part of the northern apennines is characterised by presence of three major systems of quaternary compressive structures corresponding to 1 the apenninic watershed 2 the apennines po plain margin pede apenninic thrust front and 3 the emilia ferrara and adriatic fold systems buried below the po plain geological data and interpreted seismic sections indicate a roughly n s quaternary deformation direction with rates 2 5 mm year the shortening decreased since the pliocene when our data indicate compression in a nnw sse direction and rates up to 7 mm year the trend and kinematics of the structures affecting the apennines po plain margin and the po plain subsoil fit well the pattern of the current seismicity of the area as well as recent gps and geodetic levelling data pointing to a current activity of these thrust systems controlled by an overall compressive stress field close to the apenninic watershed earthquake focal mechanisms indicate that shallow extension is associated to deep compression the extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the apenninic watershed alternatively this thrust system may have been recently deactivated and overprinted by active normal faulting deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede apenninic thrust front and a major moho structure

experimental study of a kiglapait marginal rock and implications for trace element partitioning in layered intrusions abstract experiments on a chilled marginal rock from the kiglapait intrusion labrador have been performed in order to constrain the partitioning behaviour of major and trace elements during formation of kiglapait lower zone lz cumulates at 0 1 mpa and f o 2 close to fmq the liquidus is bracketed between 1225 and 1212 c and the only liquidus phases are plagioclase an 73 74 and olivine fo 82 85 in contrast lz troctolites contain fo 67 5 olivine and an 63 4 plagioclase plagioclase melt partition coefficients d s for li ti rb sr y zr ba la and eu determined by ion microprobe analysis of run products are similar to those for other basaltic systems but differ systematically from apparent d s calculated from bulk analyses of lz plagioclases and modelled liquid compositions obtained by summation the discrepancies in d s and phase compositions are inconsistent with diffusion controlled boundary layer growth crystallisation of trapped intercumulus liquid is quantitatively plausible however a the volume of liquid required to reconcile experimental and model d s 20 1 is larger than that estimated from observed proportions of intercumulus phases 11 2 and b this mechanism alone cannot reduce x an in lz plagioclases due to very slow al si interdiffusion the discrepancy between experiment and model is best resolved if the parental melt to lz cumulates was more evolved higher fe mg na ca ree and alkalis lower sr than the summed bulk composition in accord with a recent revision of the kiglapait fe mg based on olivine compositions

a discussion of hunter and sparks contrib mineral petrol 95 451 461 silica poor iron rich liquids like those estimated for skaergaard by wager and brown are preserved in labrador as chilled pillows iron rich rocks in the kiglapait intrusion have likewise been produced by liquids poor in silica there is no reason to expect such liquids in volcanoes so their absence as lavas means nothing about their possible plutonic occurrence successful tests of the siliceous liquid hypothesis would include showing that the proposed rhyolitic liquids can produce the observed olivines in the range fo 10 40 they would require showing that the observed low f o 2 oxide mineral assemblages can occur at the high silica contents proposed and that the silicate mineral assemblages and compositions can represent high silica liquids i doubt very much that these critical tests can be met

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

kiglapait geochemistry iii potassium and rubidium abstract the regular geometry and completeness of the kiglapait intrusion permit its bulk composition to be obtained by summation and the composition of successive liquids to be obtained by subtraction the summations for k and rb give 1806 and 1 08 ppm yielding r frsol k rb 1670 for the intrusion taken as equal to the parent magma r increases slightly from this initial value to 2000 at the end of crystallization where mgo approaches zero in the rocks k and rb are therefore closely coherent and their distribution coefficients can differ only by a small amount in the kiglapait system apparent feldspar liquid distribution coefficients d f l can be estimated from detailed plots of feldspar and liquid compositions against f l the kiglapait data imply that these coefficients are linear 1 1 functions of plagioclase composition within experimental error having values given by d k f l 1 42 x an d rb f l 1 13 x an with minimum values of 0 75 and 0 49 respectively the ratio r f r l lies in the range of 1 53 0 03 for the plagioclase composition range x an 0 34 to 0 67 showing that high r rocks such as anorthosite crystallized from high r liquids the apparent feldspar distribution coefficients are much closer to 1 0 than common literature values they can be reduced by assuming that the cumulate pile was continuously recharged by the circulating magma until an advanced stage of differentiation was reached and assuming that alkalies were exchanged to the feldspars from the magma when such an aquifer recharge model is calibrated using olivine liquid equilibria as a time marker for the liquid the inferred minimum equilibrium values of the distribution coefficients are d k f l 0 42 d rb f l 0 25 at the base of the intrusion their variation is given by d k f l 1 66 1 88x an d rb f l 1 17 1 41x an the equilibrium values are considered to be appropriate for deducing liquid compositions in plutonic bodies where alkali exchange can be shown or inferred to have been inhibited such as in small intrusions the apparent values are considered to be appropriate even though they may be artificial for large intrusions similar to the kiglapait the bulk k and rb concentrations in the kiglapait intrusion are consistent with a plagioclase rich abyssal tholeiite magma clinopyroxene and olivine fractionation in the mantle may contribute to the production of such high r magmas

fluid motions and compositional gradients produced by crystallization or melting at vertical boundaries the results of a continuing series of laboratory experiments designed to model the fluid motions which accompany crystallization are both described and related in a preliminary way to prototype flows in magma chambers previous experiments have demonstrated the importance of compositional inhomogeneity produced by crystallization and melting in a thermal gradient and coupled with double diffusive effects in driving convective flows which result in thermal and compositional stratification in an originally homogeneous fluid the present experiments examine effects produced in tanks cooled at the side by the upward flow of a less dense boundary layer depleted in the crystallizing component as crystals grow on the side wall these processes are examined in simple two and three component aqueous systems h2o na2co3 h2o na2co3 k2co3 h2o cuso4 na2so4 with one and two crystallizing phases in each of these systems an initially downward flow of a cooled boundary layer against the side wall is reversed as crystallization commences and depletes the boundary layer in the crystallizing component accumulation of this cooler but lighter depleted fluid at the top of the chamber produces thermal and compositional layering by a filling box mechanism partly modified by interchange between the boundary layer and the convecting layers outside when more than one component is present in the solution the crystallization process produces a differentiated fluid column i e one with compositional gradients which are different for each of the components the compositional and thermal distributions within the fluid change with time but finally appear to reach a steady state these distributions are the integrated result of compositional changes produced by crystallization from a thin boundary layer a small proportion of the bulk fluid which evolves in composition and temperature independently of the bulk fluid in a manner controlled by the dynamics of the system the paths of fluid evolution and the resulting sequence and abundance of crystalline products are very different from those predicted on the basis of simple thermally driven crystallization in the static system disequilibrium effects probably involving different kinetics of crystallization of different crystals in part determine crystallization in the experimental system these may or may not be important in real magmatic systems there is still much to learn before even the behaviour in these simple experimental systems is understood fully and the application of the results to the interpretation of the behaviour in real magma chambers in even further away however it is apparent that dynamic effects provide an additional degree of freedom in crystallization processes and allow evolution of small increments of solution to compositions much further along crystallization paths than that allowed in static equilibrium systems petrologists will have to free their thinking from classical constraints of static systems in order to interpret many magmatic phenomena

multiscale convective overturning in mesoscale convective systems reconciling observations simulations and theory abstract an analysis of how parameterized convection interacts with hydrostatic explicitly resolved precipitation processes to represent multiscale convective overturning in a mesoscale resolution numerical simulation is presented critically important ingredients of the successful simulation are identified and the degree to which simulations are consistent with observations and theoretical considerations is examined of particular concern is how convective parameterization routines reconcile the deep moist absolutely unstable structures that form in mesoscale convective systems it is found that these structures arise primarily from resolvable scale vertical motion and that the model responds to these structures not only by maintaining parameterized convection but also by developing a hydrostatic manifestation of convective overturning on its smallest resolvable horizontal scales the strongest and most distinctive mesoscale perturbations develop in regions where the mesoscale contribution to convectiv

the 2012 emilia seismic sequence northern italy imaging the thrust fault system by accurate aftershock location abstract starting from late may 2012 the emilia region northern italy was severely shaken by an intense seismic sequence originated from a m l 5 9 earthquake on may 20th at a hypocentral depth of 6 3 km with thrust type focal mechanism in the following days the seismic rate remained high counting 50 m l 2 0 earthquakes a day on average seismicity spreads along a 30 km east west elongated area in the po river alluvial plain in the nearby of the cities ferrara and modena nine days after the first shock another destructive thrust type earthquake m l 5 8 hit the area to the west causing further damage and fatalities aftershocks following this second destructive event extended along the same east westerly trend for further 20 km to the west thus illuminating an area of about 50 km in length on the whole after the first shock struck on may 20th a dense network of temporary seismic stations in addition to the permanent ones was deployed in the meizoseismal area leading to a sensible improvement of the earthquake monitoring capability there a combined dataset including three component seismic waveforms recorded by both permanent and temporary stations has been analyzed in order to obtain an appropriate 1 d velocity model for earthquake location in the study area here we describe the main seismological characteristics of this seismic sequence and relying on refined earthquakes location we make inferences on the geometry of the thrust system responsible for the two strongest shocks

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

syn convergent extension observed using the retreat gps network northern apennines italy 1 we present crustal deformation results from a geodetic experiment retreating trench extension and accretion tectonics retreat focused on the northern apennines orogen in italy the experiment centers on 33 benchmarks measured with gps annually or more frequently between 2003 and 2007 supplemented by data from an additional older set of 6 campaign observations from stations in northern croatia and 187 continuous gps stations within and around northern italy in an attempt to achieve the best possible estimates for rates and their uncertainties we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set including the more temporally limited campaign time series the filtered coordinate time series data are used to estimate site velocity we also estimate spatially variable seasonal site motions for stations with sufficient data the rms scatter of residual time series are generally near 1 mm and 4 mm horizontal and vertical respectively for continuous and most of the new campaign stations but scatter is slightly higher for some of the older campaign data velocity uncertainties are below 1 mm yr for all but one of the stations maximum rates of site motion within the orogen exceed 3 mm yr directed ne relative to stable eurasia this motion is accommodated by extension within the southwestern and central portions of the orogen and shortening across the foreland thrust belt to the northeast of the range the data set is consistent with contemporaneous extension and shortening at nearly equal rates the northern apennines block moves northeast faster than the northern adria microplate convergence between the northern apennines block and the northern adria microplate is accommodated across a narrow zone that coincides with the northeastern apennines range front extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography the observed crustal deformation is consistent with a buried dislocation model for crustal faulting but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

crystallization sequence and magma chamber processes in the ferrobasaltic sept iles layered intrusion canada the sept iles layered intrusion quebec canada 564 ma is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro and an upper border series with anorthosite capped by cupolas of a type granite chilled margin compositions suggest a ferrobasaltic parental magma close to that of the skaergaard intrusion but much richer in iron and titanium samples from drill cores and surface sampling of the 4 7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 fe ti oxide layers cm to m thick and many anorthositic autolithic blocks the sequence of crystallization in the layered series is plagioclase an72 34 and olivine fo75 21 followed by magnetite and ilmenite then ca rich pyroxene and finally apatite an olivine gap is observed between fo66 and fo59 the saturation of fe ti oxides before ca rich pyroxene is interpreted to be the result of the high feot and tio2 contents and the low cao content of the parental magma contamination by old continental crust has occurred during crystallization of the layered series as indicated by sr isotopic compositions 87sr 86sr564 0 70360 0 70497 the differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases cr content of magnetite and lower sr isotope ratios these reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma the author 2010 published by oxford university press all rights reserved for permissions please e mail journals permissions oxfordjournals org

the nain churchill boundary and the nain plutonic suite a regional perspective on the geologic setting of the voisey s bay ni cu co deposit northern labrador is the site of two major lithotectonic elements of eastern canadian shield geology first it encompasses a paleoproterozoic continental suture zone archean rocks of the nain province tectonically juxtaposed against paleoproterozoic and reworked archean rocks of the churchill province the nain churchill suture evolved between 1860 and 1740 ma impressing upon the archean and paleoproterozoic rocks a regional metamorphic and tectonic signature referred to as the torngat orogen an important component of the torngat orogen is the tasiuyak gneiss a paleoproterozoic metasedimentary unit that occupies most of the eastern margin of the churchill province second northern labrador is the site of a world renowned terrane of mesoproterozoic anorogenic igneous rocks the nain plutonic suite that sits astride the suture and acts as a stitching batholith between the nain and churchill provinces the nain plutonic suite comprising amalgamated granitic anorthositic dioritic and troctolitic intrusions largely obscures the suture for nearly half of its total length the suite evolved between 1350 and 1290 ma and is interpreted as a product of magmatism associated with limited intracontinental rifting of the conjoined nain churchill crust above a mantle plume the voisey s bay ni cu co deposit serendipitously discovered in 1993 resides within one of the oldest troctolitic intrusions of the nain plutonic suite a 1334 ma intrusion that transgresses a contact between archean and paleoproterozoic gneisses genetic controls on the setting of mineralization have been built upon the nain churchill boundary as a zone of weakness that was exploited by mantle magmas and have implicated the tasiuyak gneiss as a crustal sulfur source although the archean paleoproterozoic junction at voisey s bay is presently interpreted as representing the nain churchill boundary in reality the provincial affinity of the archean gneisses is equivocal this uncertainty dictates caution in assigning the nain churchill boundary as the convenient transcrustal conduit that allowed the voisey s bay mafic intrusions rapid transit from their mantle staging area modeling the sulfide deposit as being solely a result of sulfur saturation of mafic magma by proximal paleoproterozoic tasiuyak paragneisses is also questionable because other genetic processes may have been responsible for example desilication of gneiss is strongly indicated by aluminous refractory minerals in vestiges of fused tasiuyak gneiss the spatial distribution of the mineralized rock at voisey s bay apparently within the subchamber plumbing system feeding a larger intrusion and within remnants of the larger intrusion itself may serve as a paradigm for similar deposits in the nain area but the preerosional comparative morphology of that larger intrusion relative to the better preserved ones may never be known a thorough understanding of the setting and genesis of the voisey s bay deposit will better facilitate establishing exploration targets in other parts of the nain region in labrador as a whole and in other geologically similar regions of the world

structural evolution of a fold and thrust belt generated by multiple decollements analogue models and natural examples from the northern apennines italy this study analyses the role played by the mechanical proprieties of the rocks involved in a thrust system focusing on the problem of multiple decollements and of related compressional structures integration of geophysical seismic reflection profiles and geological data and scaled sandbox models are used to study the deformation style of two areas of the northern apennines italy the po plain and the umbria marche apennines both areas are characterised by a complex stratigraphy consisting of decollements located at different depths that influence the geometry and kinematics of the thrust system the main characteristic of the models presented here is the presence of two decollement horizons situated at the base and in an intermediate level of the models during deformation of the models these two decollement horizons generate two sets of structures with different geometrical characteristics and significance through the joint analysis of geophysical and geological data and model results wavelengths of the compressional structures analysed show that the structural style of the two analysed areas is almost similar moreover model results prove that the final configuration of the thrust system follows the general rules of evolution of a wedge deformed above a weak decollement and is largely governed by the larger deep seated structures

orogen parallel variation in exhumation and its influence on critical taper evolution the case of the emilia romagna apennine italy abstract the northern apennine prowedge exposes two adjacent sectors showing a marked along strike change in erosion intensity namely the emilia apennine to the northwest and the romagna apennine to the southeast this setting has resulted from pliocene erosion 5 ma and exhumation which have affected the whole romagna sector and mostly the watershed ridge in emilia such an evolution has conceivably influenced the equilibrium of this fold and thrust belt which can be evaluated in terms of critical coulomb wedge theory the present state of the thrust wedge has been assessed by crosschecking wedge tapers measured along transverse profiles with fluid pressure values inferred from deep wellbores the interpretation of available data suggests that both emilia and romagna are currently overcritical this condition is compatible with the presence in both sectors of active ne dipping normal faults which would work to decrease the surface slope of the orogenic wedge however the presence of late miocene pliocene passive roof and out of sequence thrusts in romagna may reveal a past undercritical wedge state ensuing during the regional erosion phase thereby implying that the current overcritical condition would be a recent feature the setting of the emilia apennine i e strong axial exhumation and limited erosion of the prowedge suggests instead a long lasting overcritical wedge which was probably contemporaneous with the pliocene undercritical wedge in romagna the reasons for this evolution are still unclear although they may be linked to lithosphere scale processes that have promoted the uplift of romagna relative to emilia the lessons from the northern apennine thus suggest that erosion and exhumation have the ability to produce marked along strike changes in the equilibrium of a fold and thrust belt

origin of strongly reversed rims on plagioclase in cumulates abstract narrow reversed rims on plagioclase are ubiquitous in troctolites and olivine gabbros of the kiglapait intrusion and may be a common feature of all such cumulates the rims occur at plag plag plag ol and less strongly at plag aug grain boundaries they are optically obvious at an and can reach an 32 mol or more in parallel k na drops sharply although ubiquitous from sample to sample the reversed rims are only locally present at grain boundaries even for the same pair of crystals in contact they are prominent in linear networks suggesting the last trace of intercumulus liquid a subsolidus origin is ruled out by the absence of reactants at plag plag and plag ol boundaries and by the local rather than pervasive development of rims the rims are required to grow from intercumulus liquid in which the partition of an component between crystals and liquid increases with the trapped augite component of the liquid calculations from published experimental data show that an 30 can easily be achieved by such a process it is also probable that the trapped liquid is part of an an rich boundary layer generated by solute rejection during adcumulus growth the ability of the rims to sustain steep k na gradients despite a long subsolidus cooling history proves that the k na exchange rate is vanishingly small over a geologic time scale in an rich feldspar suggesting that at low k content the potassium is site bound to the tetrahedral al si distribution reversed rims therefore provide important information on diffusion limits as well as on the late stage solidification history of plagioclase rich cumulates moreover they demonstrate that plagioclase geothermometry cannot be divorced from effects of liquid composition and structure as monitored for example by augite content

compressive and tensile failure at high fluid pressure where preexisting fractures have cohesive strength with application to the san andreas fault in thrusting and strike slip situations when the maximum principal horizontal stress s1 acts nearly normal to a fault a misoriented fault such as the san andreas pore fluid pressure the lithostatic load pf sv is required to reactivate movement on that fault pf sv may be achieved without causing hydraulic tensile fracturing if 1 previously existing cracks have regained cohesive strength by chemical processes 2 subcritical crack growth has been blunted and 3 the least principal horizontal stress s3 nearly equals sv where pf sv has been attained within a misaligned fault increasing the stress difference s1 s3 at constant pf sv will not lead to shear failure while a decrease in s1 s3 can lead to shear failure of that fault however where the cohesive strength of material in a broad misaligned fault zone is less than that of the surrounding intact rock increasing s1 s3 while pf sv can result in shear failure of fractures at near optimum angles to s1 but confined within this weak fault zone if this faulting results in the local short lived attainment of pf sv cataclastic deformation and frictional heating overcoming dilation and a simultaneous decrease in s1 s3 this combination of effects can trigger movement along the main trace of the misaligned fault when increasing pf results in hydraulic failure anisotropy in tensile strength or fracture toughness resulting from foliation within faults allows fractures to propagate along the planes of weakness rather than across the foliation perpendicular to s3

ground heating and methane oxidation processes at shallow depth in terre calde di medolla italy observations and conceptual model the toponym terre calde di medolla literally warm earths of medolla refers to a farming area located near the town of modena emilia romagna region northern italy which has always been known by the local population for the relatively high temperatures of the soil this phenomenon is particularly evident in wintertime when the snow cover over this area rapidly melts a detailed investigation carried out after the devastating 2012 emilia earthquake that affected this area showed soil temperatures up to 44 c i e 20 25 c above the local background value together with diffuse soil fluxes of ch4 0 2432 g m 2 d 1 and minor though significant co2 0 1184 g m 2 d 1 especially from subcircular a few meters in diameter zones ground heating and gas seepage appear spatially correlated thus suggesting a close relationship between the two phenomena the anomalous high ground temperature is not associated with an anomalous geothermal gradient or with the uprising of deep seated hot fluids according to the lateral and vertical distributions of the temperatures as well as the chemical and isotopic compositions of the soil gases the most reliable explanation is the exothermic oxidation of diffusely uprising biogenic methane at very shallow levels 1 m such a process occurs in the presence of free oxygen and methanotrophic bacteria and can then explain i the observed ground heating up ii the diffuse emission from the soil of co2 characterized by an extremely negative isotopic 13c 12c signature and iii the lack of diffuse and low ch4 fluxes according to these hypotheses the heating phenomena affecting the shallow groundwater and the ground surface as described by several witnesses in the area of the may june 2012 emilia earthquake could be related to either a coseismic or postseismic onset of new areas affected by ch4 seepage or an increase in preexisting ch4 fluxes

a new active tectonic model for the construction of the northern apennines mountain front near bologna italy 1 we integrate existing and new geologic data retreating trench extension and accretion tectonics retreat project particularly on the origin growth and activity of the mountain front at bologna italy into a new model that explains apennine orogenesis in the context of a slab rollback upper plate retreat process the bologna mountain front is an actively growing structure driving rock uplift 1 mm year cored by a midcrustal flat ramp structure that accommodates ongoing shortening driven by adria subduction at a rate of 2 5 mm year the data we use are assembled from river terraces and associated pleistocene growth strata geodesy including releveling surveys reinterpretation of published reflection lines and a new high resolution reflection line these data constrain a simple trishear model that inverts for blind thrust ramp depth dip and slip apennine extension is recognized both in the foreland as high angle normal faults and modest stretching in the carapace of the growing mountain front and in the hinterland with larger normal faults that accomplish some crustal thinning as the upper plate retreats this coevolution of extension and shortening shares some notable characteristics with other basement involved collisional orogens including the early tertiary laramide orogeny in the american west and the oligocene to miocene evolution of the alps we propose a possible relationship between underplating and the development of the po as a sag basin as a quaternary phenomenon that may also apply to past periods of apennine deformation tortonian continued shortening on the structure beneath the bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern apennines

kiglapait mineralogy iii olivine compositions and rayleigh fractionation models olivints present throughout the layered cumulates of the kiglapait intrusion record extreme iron enrichment during fractional crystallization mn is less compatible than fe the exchange coefficient kd for mn fe ol liq has values near 0 95 but they drop to 0 7 near the lower one upper one boundary ca is depleted by more than a factor of 30 relative to experimental values at 5 kbar pressure attempts to find a sink for ca in the lower zone without invoking liquid as a reactant are unconvincing and questions of metastability arise cumulus olivines vary systematically to lower fo contents with stratigraphic height using equilibrium values for the exchange coefficient kd fe mg ol ljq j and the observed mode of olivine and residual porosity a rayleigh fractionation calculation reproduces the observed lower zone trend without recourse to multiple injections of magma an anomalously fe rich region above the main ore band in the upper zone ascribed to ponding of fe rich magma at the floor of the intrusion until later buoyant residual magma entrained the fe rich residua such fe rich ponds probably account for the abnormal fe enrichment shown by some other fenner trend layered intrusions summation over the observed crystal compositions yields values of xjug that do not represent the equilibrium liquid but that reduce to it by a simple multiplier p 0 78 this result means that if ko is known the high temperature liquidus olivine compositions can be retrieved or vice versa because the observed olivine compositions are supported by realistic forward models there is no need to invoke evolved boundary layer liquids to explain the in situ crystallization of kiglapait cumulates classical cumulate theory suffices

a partisan review of proterozoic anorthosites most anorthosites of the massif type crystallized in the episode 1 7 1 2 gyr with a pronounced peak of the age distribution near 1 4 gyr they were emplaced anorogenically at depths as shallow as 7 km where the ambient temperature of country rocks was probably less than 250 c depths of emplacement may have been as great as 25 km or more in rare cases the greater depths of equilibration estimated from granulite facies metamorphism may be incorrectly interpreted as emplacement depths but in any case they are demonstrably not required or characteristic of anorthosite emplacement penetrative deformation and metamorphism of anorthosites are post emplacement accidents of the local geologic history and are not directly caused by the presence of anorthosites granitic rocks mangerite charnockite suite associated with anorthosite are in general later or contemporaneous products of crustal anatexis with chemical and isotopic signatures distinct from the anorthosites and their residua such granitic rocks should not therefore be summed with the anorthositic rocks to obtain bulk compositions the magmas that produced most anorthosites were dry as shown by high temperature mineralogy and anhydrous mineral assemblages in contact aureoles residua from their crystallization are ferrodiorites to ferrosyenites typical of closed system fractionation these residua were locally and frequently ejected into contemporaneously molten granite where they formed pillows and cooled rapidly the overall chemistry of anorthosites and residua is broadly tholeiitic and consistent with derivation from the mantle olivine bearing magmas locally ranged from leucotroctolite anorthosite to later but coexisting picrite or melatroctolite in the same pluton confirming a wide spectrum of magma types a signal feature of troctolitic and noritic magmas is their low augite content implying high content of spinel component large anorthosite complexes such as nain and harp lake consist of many plutons representing repeated injections of separate magma batches with varying chemistry the abundant true anorthosites richer in plagioclase than magmas cosaturated with a mafic phase must represent plagioclase enrichment by either mechanical or chemical processes or both the role of kinetics in nucleation and solidification of such rocks may be centrally important it is proposed that hyperfeldspathic plagioclase supersaturated liquids were generated by quasi isothermal extraction of mafic minerals from tholeiitic magma enroute to and at the site of emplacement and that such a kinetic process was uniquely permitted in an environment of aborted continental rifting anorthositic rocks may have much to say about the episodic versus continuous geochemical evolution of the earth s mantle

coseismic displacement bilateral rupture and structural characteristics at the southern end of the 1999 chi chi earthquake rupture central taiwan 1 the 1999 chi chi earthquake mw 7 6 was due to slip along the chelungpu fault a major n striking thrust fault in the fold thrust belt of western taiwan the surface rupture extends over 100 km in a n s trend with nw trending horizontal displacement increasing from 2 to 10 m from south to north the central segment of the chelungpu fault is characterized by bedding slip along the pliocene chinshui shale which has resulted in the development of a monoclinal structure on the hanging wall at the southern end of the chi chi earthquake rupture however the chelungpu fault connects with the ne striking tachienshan fault and cuts into miocene strata with complex structures on the hanging wall in this study we use digital cadastral data to calculate coseismic horizontal displacement around the chushan area results show the amount and direction of horizontal displacement to be ca 1 2 to 2 6 m and ca 220 to 260 respectively on the hanging wall and ca 1 4 m and 105 respectively on the footwall coseismic displacement and seismological data pertaining to the hanging wall at the southern end of the chi chi earthquake rupture indicate the existence of three distinct blocks horizontal displacement indicates the chushan block s movement trended sw this result reflects the chushiang and luliao faults being reactivated with different faulting mechanisms and slip azimuths this study considers a complex coseismic displacement field resulting from a bilateral rupture process whereby a southward rupture with sw trending movement results in right lateral strike slip faulting of the tachienshan fault and thrusting with a right lateral component on the ns strike of the chelungpu fault the northward rupture is associated with nw trending movement that results in activation of the luliao and chushiang faults

an experimental investigation into the role of phyllosilicate content on earthquake propagation during seismic slip in carbonate faults carbonate faults commonly contain small amounts of phyllosilicate in their slip zones due to pressure solution and or clay smear to assess the effect of phyllosilicate content on earthquake propagation in carbonate faults friction experiments were performed at 1 3 m s on end members and mixtures of calcite illite smectite and smectite gouge experiments were performed at 9 mpa normal load under room humidity and water saturated conditions all dry gouges show initial friction values i of 0 51 0 58 followed by slip hardening to peak values of 0 61 0 76 slip weakening then ensues with friction decreasing to steady state values ss of 0 19 0 33 within 0 17 0 58 m of slip contrastingly wet gouges containing 10 50 wt phyllosilicate exhibit i values between 0 07 and 0 52 followed by negligible or no slip hardening rather steady state sliding ss 0 2 is attained almost immediately microstructurally dry gouges show intense cataclasis and wear within localized principal slip zones plus evidence for thermal decomposition of calcite wet gouges exhibit distributed deformation less intense cataclasis and no evidence of thermal decomposition it is proposed that in wet gouges slip is distributed across a network of weak phyllosilicate formed during axial loading compaction prior to shear this explains the 1 subdued cataclasis and associated lack of slip hardening 2 distributed nature of deformation and 3 lack of evidence for thermal decomposition due to low friction and lack of slip localization these findings imply that just 10 phyllosilicate in the slip zone of fluid saturated carbonate faults can 1 dramatically change their frictional behavior facilitating rupture propagation to the surface and 2 significantly lower frictional heating preventing development of microscale seismic markers

regional ai fe mafic magmas associated with anorthosite bearing terranes proterozoic anorthosite massifs are nearly monomineralic accumulations of plagioclase feldspar which must result from unusual conditions of crystallization and emplacement1 2 their chemistry is compatible with derivation from a high alumina basalt parent of mantle origin1 and mafic magmas rich in aluminium and iron have long been suspected of having an important connection to anorthosites and their parent magmas1 4 regional examples of mafic magmas clearly compatible with an anorthosite lineage have not been generally recognized3 in part because of the paucity of candidates within the anorthosite massifs themselves samples of such magmas should also be sought in the country rocks surrounding the massifs here we report the widespread occurrence of al fe mafic magmas in the anorthosite bearing adirondack highlands of new york state they are chemically distinct from typical high ai basalt fe basalt and most common magma types identification of similar al fe basaltic magmas in other areas suggests that such magmas are characteristic of anorthosite bearing terranes

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

fault architecture and deformation mechanisms in exhumed analogues of seismogenic carbonate bearing thrusts abstract faults in carbonates are well known sources of upper crustal seismicity throughout the world in the outer sector of the northern apennines ancient carbonate bearing thrusts are exposed at the surface and represent analogues of structures generating seismicity at depth we describe the geometry internal structure and deformation mechanisms of three large displacement thrusts from the km scale to the microscale fault architecture and deformation mechanisms are all influenced by the lithology of faulted rocks where thrusts cut across bedded or marly limestones fault zones are thick tens of metres and display foliated rocks s cc tectonites and or ypr cataclasites characterized by intense pressure solution deformation in massive limestones faulting occurs in localized narrow zones that exhibit abundant brittle deformation a general model for a heterogeneous carbonate bearing thrust is proposed and discussed fault structure affected by stratigraphic heterogeneity and inherited structures influences the location of geometrical asperities and fault strain rates the presence of clay minerals and the strain rate experienced by fault rocks modulate the shifting from cataclasis dominated towards pressure solution dominated deformation resulting structural heterogeneity of these faults may mirror their mechanical and seismic behaviour we suggest that seismic asperities are located at the boundaries of massive limestones in narrow zones of localized slip whereas weak shear zones constitute slowly slipping portions of the fault reflecting other types of aseismic behaviour

stability of fault plane solutions for the major n italy seismic events in 2012 abstract we propose a critical analysis of the moment tensor solutions of the major seismic events that affected northern italy in 2012 inverting full waveforms at regional distance using the non linear method named inpar we investigate period dependent resolution that affects in particular the solutions of shallow events this is mainly due to the poor resolution of mzx and mzy components of the seismic tensor when inverting signals whose wavelengths significantly exceed the source depth as a consequence instability affects both source depth and fault plane solution retrieval and spurious large compensated linear vector dipole components arise the inversion performed at cutoff periods shorter than 20 s reveals in many cases different details of the rupture process which are supported by independent geodynamical arguments thus we conclude that inversion of full waveforms at cutoff period as short as possible should be preferred

real time determination of seismic moment tensor for the italian region this work has been funded by the 2005 2007 dpc s4 and 2008 2010 dpc s3 italian civil protection contracts

plagioclase fractionation and the common basalt a labor saving device is recalled which predicts the course of plagioclase fractionation in hat creek basalt within 2 mole an until the system is 80 crystallized referred to the smoothed hat creek data the effective plagioclase liquid partition coefficient d a an eff is estimated from d eff 1 81f dt prime 1 04 where f di prime is the cipw normative fraction di di fsp in this case 0 2 the data for hat creek basalt suggest an intercept constant equal to 1 08 rather than 1 04 this method of predicting plagioclase fractionation emphasizes the importance of initial liquid composition and structure and its success shows that the effects of temperature are minor and submerged in the general empirical expression for d eff experimental verification of the augite effect is found in earlier data for the system di an ab

fluid pressure stress field and propagation style of coalescing thrusts from the analysis of the 20 may 2012 ml 5 9 emilia earthquake northern apennines italy terra nova 25 72 78 2013 abstract two major earthquakes of ml 5 9 and 5 8 and hundreds of aftershocks affected the emilia region po plain italy between 20 may and june 2012 the events concentrate in the uppermost 10 km of the crust with few events up to 30 km two buried sub parallel n100 e striking thrusts of the northern apennines belt are reactivated these thrusts coalesce at the interface between the metamorphic basement of the belt and the overlying about 10 km thick sedimentary succession focal mechanisms indicate a compressive stress field with a sub horizontal roughly n s striking 1 this stress field is consistent with active shortening in northern apennines suprahydrostatic pore pressure and 1 2 3 are required to reactivate the thrusts the involved fluids could be gas and brines hosted in the folded sedimentary successions the time and spatial evolution of the seismicity indicates a foreland to hinterland propagation of the ruptures and a thin skinned deformation of northern apennines

a seismic sequence from northern apennines italy provides new insight on the role of fluids in the active tectonics of accretionary wedges abstract we analyze a seismic sequence which occurred in 2000 along the northern apennines accretionary wedge italy the sequence developed within the cretaceous triassic limestones of the tectonic wedge where methane rich and oil reservoirs are stored ruptures mainly developed on wnw ese striking thrusts the compressive stress field is consistent with that acting at regional scale in northern apennines seismic parameters indicate that fluids are involved in the seismogenic process the amplitudes of the p and s phases and data from some stations evidence a p to s conversion within v p v s 2 1 layer the attenuation properties of crust show a higher attenuation zone located west of the epicentral cloud eight hundred aftershocks delineate a sub vertical cloud of events between 7 and 14 km depth the space time evolution of the aftershocks is consistent with a diffusive spreading diffusivity 1 9 m 2 s along vertically superimposed thrusts diffusion also controls the time evolution of the sequence fluid pressure is estimated to be roughly equal to the vertical lithostatic stress the overpressure within reservoirs develops by tectonic compaction processes the fluids upraise along sub vertical fractures related to the shortening of the wedge the 2000 sequence occurred in an area that separates a thermal and deeper petroleum system from a shallower biogenic system the divider of these systems controls the attenuation properties of the crust the fluid rock interaction at seismogenetic depth is related to hydrothermal processes more than to compaction in accretionary wedges seismicity activating superimposed thrusts may drive methane and oil upraising from the upper crust

progressive offset and surface deformation along a seismogenic blind thrust in the po plain foredeep southern alps northern italy here we present for the first time in the po plain foredeep northern italy the middle to late pleistocene growth history of an outcropping secondary fold and related faults whose progressive deformation over an intermediate time window 105 years is driven by an underlying seismogenic blind thrust we trenched and logged an outcropping decametric secondary anticline related to a deeper blind compressional structure which deforms fluvial sediments and an overlying loess paleosol sequence folded units were dated using radiocarbon and optically stimulated luminescence methods to the late pleistocene holocene and tentatively correlated with glacial interglacial phases occurring during the time interval from marine isotope stage 6 to the present a multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline varying between 0 02 and 0 1 mm yr since circa 200 kyr trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break backward activation this generated a decametric surface fold whose most recent growth was associated with bending moment normal faulting in the crestal and forelimb region our observations demonstrate that near surface compressive tectonics can be caused by blind thrusting via a complex array of fault and folds upward strain propagation and generation of shallow low angle thrust and related folding seem to be mainly due to secondary fold related faulting according to an out of syncline thrusting mechanism

pattern recognition approach to the subsequent event of damaging earthquakes in italy abstract in this study we investigate the occurrence of large aftershocks following the most significant earthquakes that occurred in italy after 1980 in accordance with previous studies vorobieva and panza 1993 vorobieva 1999 we group clusters associated with mainshocks into two categories type a if given a main shock of magnitude m the subsequent strongest earthquake in the cluster has magnitude m 1 or type b otherwise in this paper we apply a pattern recognition approach using statistical features to foresee the class of the analysed clusters the classification of the two categories is based on some features of the time space and magnitude distribution of the aftershocks specifically we analyse the temporal evolution of the radiated energy at different elapsed times after the mainshock the spatio temporal evolution of the aftershocks occurring within a few days and the probability of a strong earthquake an attempt is made to classify the studied region into smaller seismic zones with a prevalence of type a and b clusters we demonstrate that the two types of clusters have distinct preferred geographic locations inside the italian territory that likely reflected key properties of the deforming regions different crustal domains and faulting style we use decision trees as classifiers of single features to characterize the features depending on the cluster type the performance of the classification is tested by the leave one out method the analysis is performed on different time spans after the mainshock to simulate the dependence of the accuracy on the information available as data increased over a longer period with increasing time after the mainshock

near real time ground motion updating for earthquake shaking prediction abstract one of the main challenges of modern engineering seismology is the mitigation of the adverse consequences of earthquakes although modern engineering techniques allow for the designing of earthquake resistant structures the ability to predict more reliable ground motion estimates and associated uncertainties is needed with this aim this study investigated the possibility of using data recorded during an earthquake to improve the empirical ground motion prediction equations gmpes in particular we propose a procedure that updates the coefficients of an initial gmpe to account for the specific features of a seismic source and propagation medium we applied the technique in the immediate postevent time period of three well recorded earthquakes that occurred recently in italy and caused casualties and significant damage the 6 april 2009 m w 6 3 l aquila earthquake the 20 may 2012 m w 5 9 emilia earthquake and the 25 october 2012 m w 5 2 pollino earthquake for possible future development using the same earthquakes and the networks with which they were recorded we also explored the potential of the technique as a possible real time application as in the case of earthquake early warning systems

kiglapait geochemistry vii yttrium and the rare earth elements abstract based on 51 wholerock analyses by xrf and summation over the layered group the kiglapait intrusion contains 4 7 1 6 1 2 ppm y which resides principally in augite and apatite using liquid compositions calculated by summation the partition coefficient daug ly is 0 95 0 12 from 84 to 97 pcs percent solidified and 1 5 0 4 above 97 pcs for feldspar the most likely value for d is 0 028 0 02 n 6 ree analyses for 13 whole rocks were interpreted with the aid of yttrium models to yield trends for wholerocks and liquids vs pcs summations over the rocks of the layered group gave la 2 5 ce 5 8 nd 3 9 sm 1 0 eu 0 8 tb 0 17 yb 0 37 and lu 0 06 ppm with 2 s d errors near 30 all these elements are highly incompatible until the arrival of augite which affects chiefly the hree and apatite which affects all but more strongly the lree the net result is that after apatite arrival at 94 pcs the liquid compositions are nearly constant hence dwr lree 1 0 these results are compatible with the mineralogy of the intrusion and the estimated partition coefficients for feldspar olivine augite apatite and fe ti oxide minerals for pre apatite liquids dfsp lree vary regularly with the normative di content of the liquid and change by an order of magnitude hence the bulk liquid composition must be considered in any attempt to invert the compositions of feldspars to parent liquids the eu anomaly at first decreases in kiglapait liquids due to plagioclase fractionation but then increases due to removal of augite and apatite with negative eu anomalies the features dominantly responsible for eu partitioning are liquid structure and for monoclinic ternary feldspars crystal structure the former is best monitored by the augite or diopside content of the liquid and the latter by the k content of the feldspar the chondrite normalized ree pattern for the intrusion has lan 7 4 lun 1 6 ce yb n 3 6 and eu eu 2 4 indicating its feldspar rich nature the chilled margin of the nearby hettasch intrusion has a similar but more evolved pattern corresponding roughly to the kiglapait liquid at 70 pcs as with other data those for the ree suggest source differences for the two intrusions rather than a relationship due to fractionation

marginal rocks resembling the estimated bulk composition of the kiglapait intrusion abstract the southern margin of the kiglapait intrusion labrador contains fine grained rocks 5 6 m above a contact with anorthosite of the nain complex and a laminated unit 3 m from the contact three fine grained samples and one of the laminated unit have a mean composition closely resembling that previously calculated by summation of the exposed layered group analyzed values agree closely with the earlier estimates for alkalies sr and y thus they support the mineral liquid partition coefficients previously calculated for these elements and for the rare earth elements based on new calculations the value for ferric oxide is revised to 1 04 from its original value of 1 91 the new samples are depleted in the incompatible elements titanium and phosphorus suggesting that they have lost some residual liquid by sidewall fractional crystallization and downward motion of rejected solute the marginal rocks provide no evidence for repeated injection of magma during lower zone time

strength evolution of simulated carbonate bearing faults the role of normal stress and slip velocity abstract a great number of earthquakes occur within thick carbonate sequences in the shallow crust at the same time carbonate fault rocks exhumed from a depth 20 mpa fault gouges undergo strain weakening that is more pronounced at slow slip velocities and causes a significant reduction of frictional strength from 0 7 to 0 47 microstructural analysis show that fault gouge weakening is driven by deformation accommodated by cataclasis and pressure insensitive deformation processes pressure solution and granular plasticity that become more efficient at slow slip velocity the reduction in frictional strength caused by strain weakening behaviour promoted by the activation of pressure insensitive deformation might play a significant role in carbonate bearing faults mechanics

the may 20 mw 6 1 and 29 mw 6 0 2012 emilia po plain northern italy earthquakes new seismotectonic implications from subsurface geology and high quality hypocenter location abstract this study presents new geological and seismological data that are used to assess the seismic hazard of a sector of the po plain northern italy a large alluvial basin hit by two strong earthquakes on may 20 mw 6 1 and may 29 mw 6 0 2012 the proposed interpretation is based on high quality relocation of 5369 earthquakes emilia sequence and a dense grid of seismic profiles and exploration wells the analyzed seismicity was recorded by 44 seismic stations and initially used to calibrate new one dimensional and three dimensional local vp and vs velocity models for the area considering these new models the initial sparse hypocenters were then relocated in absolute mode and adjusted using the double difference relative location algorithm these data define a seismicity that is elongated in the w nw to e se directions the aftershocks of the may 20 mainshock appear to be distributed on a rupture surface that dips 45 ssw and the surface projection indicates an area 10 km wide and 23 km long the aftershocks of the may 29 mainshock followed a steep rupture surface that is well constrained within the investigated volume whereby the surface projection of the blind source indicates an area 6 km wide and 33 km long multichannel seismic profiles highlight the presence of relevant lateral variations in the structural style of the ferrara folds that developed during the pliocene and pleistocene there is also evidence of a mesozoic extensional fault system in the ferrara arc with faults that in places have been seismically reactivated these geological and seismological observations suggest that the 2012 emilia earthquakes were related to ruptures along blind fault surfaces that are not part of the pliocene pleistocene structural system but are instead related to a deeper system that is itself closely related to re activation of a mesozoic extensional fault system