historical earthquakes and variable kinematic behaviour of the 2009 l aquila seismic event central italy causative fault revealed by paleoseismological investigations abstract paleoseismological investigations has been carried out along the causative fault of the mw 6 1 2009 l aquila earthquake we dug three trenches in two different sites on the paganica fault to understand its holocene kinematic behavior paleoseismological results show a minimum of three faulting events preceding the 2009 earthquake the most recent recognized event occurred after 1420 1610 a d tentatively attributed to the 1703 february 2 seismic shock a previous event happened between 1st 2nd century a d and 7th 9th century a d probably in the interval 4th 6th century a d while another identified previous event occurred prior to 1st 2nd century a d the observed minimum displacement per event varies from 0 25 m to 0 50 m consistent with a fault length of about 22 27 km from which we infer a maximum expected mw 6 6 6 7 this implies that the paganica fault may occasionally rupture during 2009 like seismic events as well as during larger earthquakes activating contemporaneously to nearby active faults kinematically and structurally linked to the paganica fault more specifically on the basis of our data and of recent paleoseismologic studies we hypothesize a linkage of the investigated fault with the upper aterno valley fault system in this perspective the paganica fault can rupture as an independent fault segment with recurrence interval of about 3 hundreds of years and together with the upper aterno valley fault system with recurrence interval that varies between 1000 and 1500 years

quaternary rock avalanches in the apennines new data and interpretation of the huge clastic deposit of the l aquila basin central italy abstract in this paper we inferred the origin of a huge clastic deposit i e l aquila breccia which widely crops out within the l aquila intermontane basin a tectonic depression in central apennines that is bounded by seismogenic active faults as demonstrated by the earthquake occurred on april 6 2009 mw 6 1 the genesis of this deposit is still debated in the literature for this reason a number of methods have been applied mainly aimed at evidencing its geomorphological and sedimentological features as well as at defining its geometry and volume through cross sections constrained by borehole data and field observations on the basis of the obtained results we identified such deposit as resulting from a quaternary rock avalanche event in particular the rock avalanche would have detached during the cold climate phases of late middle pleistocene from the southern slope of the gran sasso range a sector characterized by the presence of numerous dgsd related landforms we performed morphometric analyses of the gran sasso slope in order to define the potential source area of the inferred rock avalanche and according to the results the volume estimated from this area about 108 m3 is coherent with the volume calculated for the preserved rock avalanche deposit furthermore we analyzed the main features of the deposit i e age and morphometric parameters also in the light of similar rock avalanche events occurred in the same region during the quaternary with the aim of discussing potential analogues and better understanding the role of gravity induced processes in the quaternary morpho evolution of the apennine chain

the seismic response at high frequency in central l aquila a comparison between spectral ratios of 2d modeling and observations of the 2009 aftershocks abstract the city of l aquila is built on a deep intramontane basin filled by silty clay of lacustrine origin with average s wave velocity of about 725 m s topped by a calcareous breccias unit with a higher speed of about 900 m s new geologic and geophysical investigations following the 6 april 2009 m w 6 3 l aquila italy earthquake have allowed us to develop a new velocity model for the basin deposits that coupled with the inversion of velocity includes lateral velocity variations in the top breccia layer and a newly found red silts unit the limi rossi del colle dell aquila lrca the city area where the lrca unit outcrops is correlated with clusters of reinforced concrete buildings that collapsed in the normal faulting earthquake we simulate the 2d seismic response of this new velocity model along two orthogonal cross sections and compare the synthetic spectral ratios to the experimental ones evaluated using aftershock recordings as a result taking into account the full scatter about the mean of the observed spectral ratios we are able to predict not only the main features of the primary observed low frequency resonance peak but also the level of amplification at high frequency at most of the sites investigated

impact of subglacial geothermal activity on meltwater quality in the jokulsa a solheimasandi system southern iceland the influence of subglacial geothermal activity on the hydrochemistry of the jokulsa a solheimasandi glacial meltwater river south iceland is discussed a radio echosounding and global positioning system survey of south west myrdalsjokull the parent ice cap of the valley glacier solheimajokull establishes the geometry and position of a subglacial caldera a cauldron in the ice cap surface at the basin head is also defined signifying one location of geothermally driven ablation processes background h 2 s concentrations for the jokulsa meltwaters in summer 1989 show that leakage of geothermal fluids into the glacial drainage network takes place throughout the melt season chemical geothermometry na k ratio applied to the bulk meltwaters tentatively suggests that the subglacial geothermal area is a high temperature field with a reservoir temperature of 289 304 c a major event of enhanced geothermal fluid injection was also detected against a background of an apparently warming geothermal reservoir the event began on julian day 205 24 july with a burst of subglacial seismic activity meltwater hydrochemical perturbations followed on day 209 and peaked on day 213 finally leading to a sudden and significant increase in flow on day 214 the hydrochemical excursions were characterized by strong peaks in meltwater h 2 s so 2 4 and total carbonate concentrations transient decreases in ph small increases in ca 2 and mg 2 and sustained increases in electrical conductivity the event may relate to temporary invigoration of the subglacial convective hydrothermal circulation seismic disturbance of patterns of groundwater flow and geothermal fluid recruitment to the subglacial drainage network or a cyclic sweeping out of the geothermal zone by the annual wave of descending groundwater time lags between seismic events and meltwater electrical conductivity responses suggest mean and maximum intraglacial throughflow velocities of 0 032 0 132 ms 1 respectively consistent with a distributed drainage system beneath solheimajokull because increases in flow follow hydrochemical perturbations the potential exists to use meltwater hydrochemistry to forecast geothermally driven flood events in such environments

seasonal evolution of water contributions to discharge from a greenland outlet glacier insight from a new isotope mixing model the greenland ice sheet gris subglacial hydrological system may undergo a seasonal evolution with significant geophysical and biogeochemical implications we present results from a new isotope mixing model to quantify the relative contributions of surface snow glacial ice and delayed flow to the bulk meltwater discharge from a small 5k m 2 land terminating gris outlet glacier during melt onset may and at peak melt july we use radioactive 222 rn and stable isotopes 18 o deuterium to differentiate the water source contributions atmospherically derived 7 be further constrains meltwater transit time from the glacier surface to the ice margin we show that 1 222 rn is a promising tracer for glacial waters stored at the bed and 2 a quantitative chemical mixing model can be constructed by combining 222 rn and the stable water isotopes applying this model to the bulk subglacial outflow from our study area we find a constant delayed flow stored component from melt onset through peak melt this component is diluted first by snowmelt and then by increasing glacial ice melt as the season progresses results from this pilot study are consistent with the hypothesis that subglacial drainage beneath land terminating sections of the gris undergoes a seasonal evolution from a distributed to a channelized system

ancient shelf ridges a potentially significant component of the transgressive systems tract case study from offshore northwest java detailed stratigraphic evaluation of three dimensional 3 d seis mic volumes calibrated with well log and core data from the mio cene section of the offshore northwest java shelf reveals the exten sive presence of preserved shelf ridge deposits these features are long linear bodies ranging from 0 3 to 2 0 km wide more than 20 km long and up to 17 m high on close inspection these features appear to be asymmetric characteristically sharp edged and thicker on one side and gradually thinning with an irregular edge on the other side possible sand waves smaller in scale are observed super imposed on these ridges and oriented oblique to the long axes of the ridges the observed shelf ridge deposits tend to be sand prone and overlie ravinement surfaces the ridges appear to be oriented parallel with the axes of broad paleoembayments associated with the structural fabric of the basin in addition to shelf ridges shelf ribbons possibly less than 5 m thick and less than 100 m wide are also imaged sand ridges are common on modern shelves but significantly less commonly recognized in the subsurface or in outcrop the features observed here represent examples of preserved ancient shelf ridges these ridges are thought to have formed as a result of erosion and subsequent reworking of sand prone deltaic and or coastal plain deposits by shelf tidal currents which became active immediately after shoreline transgression these deposits appear to have migrated across the ancient sea floor and represent an important component of the transgressive systems tract these transgressive systems tract deposits have significant exploration potential because they are commonly sand prone and tend to be encased in shelf mudstone seal facies depending on the degree to which sand is present in interridge locations these linear sand bodies can comprise potential stratigraphic traps begin page 76

hvnsr survey in historical downtown l aquila central italy site resonance properties vs subsoil model abstract this paper presents and discusses the results of a detailed seismic noise survey carried out in historical downtown l aquila after the earthquake of 6 apr 2009 m w 6 3 seismic noise data were interpreted through numerical simulations with the support of a subsoil model characterised by four main units from the top to the bottom i soft soils anthropogenic filling material and terra rossa ii l aquila breccia iii l aquila pelite and sand and iv the meso cenozoic carbonate bedrock the hvnsr analysis permitted the identification of two peaks f0 and f1 nearly everywhere f0 0 4 0 7 hz is due to the superposition of l aquila pelite and sand on the carbonate bedrock at 200 300 m below ground level f1 3 15 hz is caused by shallower impedance contrasts due to 3 20 m thick soft sediments overlying l aquila breccia and by the weathering profile of l aquila breccia a numerical simulation was carried out for three different models characterised by i lithology lateral variation in the first 100 m of thickness due to the substitution from north to south of l aquila breccia with l aquila pelite and sand ii the thickness variation of soft top soil onto l aquila breccia and iii the presence of a weathered layer in the upper part of the l aquila breccia the numerical simulation results fit the experimental seismic noise data a spatial correlation between areal distributions of severe damages with that of f1 resonance frequency is found so it follows that the severe damage during the l aquila earthquake of 6 apr 2009 could have been caused by the seismic local effect of the soft top soil and the weathering profile of l aquila breccia

coupling basin infill history and mammal biochronology in a pleistocene intramontane basin the case of western l aquila basin central apennines italy the western l aquila basin recorded in quaternary times two well distinguished phases of intramontane basin fill concomitant with uplift of central apennines and characterized by diverse large mammal assemblages the first phase was dominated by alluvial fan and lacustrine palustrine sedimentation respectively gelasian and calabrian in age that took place within an internally drained fault controlled hydrographic system a late villafranchian earliest galerian large mammal assemblage approximately 1 3e1 1 ma pertains to this phase and includes mammuthus meridionalis stephanorhinus etruscus and the large cervid arvernoceros aff a giulii the second phase of filling middle pleistocene to holocene in age is dominated by fluvial sedimentation which is related to a through going fluvial system developed after the emptying of the former lake a middle galerian large mammal assemblage approximately 600 ka comes from the oldest deposits of this phase biochronological data help date steps of geological and morphological evolution in an intramontane setting and permit to temporally constrain the major change in local hydrography and sedimentation at the early middle pleistocene transition this change was likely forced by an increment of uplift rates which is well recorded along the axial range and peripheral belts of the apennines 2011 elsevier ltd and inqua

post rift sequence architecture and stratigraphy in the oligo miocene sardinia rift western mediterranean sea abstract rift basins provide important sedimentary archives to reconstruct past tectonic and climatic conditions understanding their sedimentary history is however largely hampered by the competing influence of tectonic versus climatic forcing the aim of this study is to comprehend the effects of local to regional tectonic and global climatic eustatic changes on shallow marine depositional systems in the sardinia rift western mediterranean sea for this purpose the stratigraphic and depositional relations of a mixed siliciclastic carbonate ramp at the porto torres basin margin were studied along extensive proximal to distal transects three depositional sequences ds1 to ds3 of late burdigalian to early serravallian age have been identified which are separated by erosional unconformities each contains a lower transgressive part and an upper regressive part the former includes shoreface sandstone ds2 or coral reef ds3 deposits on the proximal ramp and channelized sheet sandstone ds1 or basinal mudstone ds2 ds3 deposits on the distal ramp typically recording an upsection trend of sediment starvation the latter is represented by basinward prograding coralline red algal carbonate wedges due to enhanced shallow water carbonate production rates in the long term the depositional evolution from ds1 to ds3 reveals basin margin progradation associated with decreasing siliciclastic supply integrated calcareous nannoplankton foraminiferal pectinid biostratigraphy links the depositional sequences to third order sea level cycles and allows to correlate the erosional unconformities at the top of ds1 and ds2 with the bur 5 lan 1 and lan 2 ser 1 sequence boundaries the improved sequence stratigraphic framework enables better regional and global correlations this shows that rhodalgal carbonate slopes started prograding in the western branch of the sardinia rift during the late burdigalian because 1 of a worldwide bloom of rhodalgal facies and 2 decreasing tectonic activity at the transition from the syn rift to the post rift stage caused a continuous reduction of the siliciclastic sediment input

solute dynamics of meltwater of gangotri glacier garhwal himalaya india the present study investigates solute dynamics of meltwater of gangotri glacier system in terms of association of different chemical compounds with the geology of the area in the meltwater the presence of cations varied as c mg2 c ca2 c na c k while order of concentration of anions has been c hco3 c so42 c cl c no3 in years 2003 and 2004 the magnesium and calcium are found as the dominant cations along with bicarbonate and sulphate as dominant anions the high ratios of c ca2 mg2 total cations and c ca2 mg2 c na k indicate that the meltwater chemistry of the gangotri glacier system catchment is mostly controlled by carbonate weathering attempts are made to develop rating curves for discharge and different cations sporadic rise in discharge without corresponding rise in concentration of most of cations is responsible for their loose correlation in a compound valley glacier like gangotri glacier

the seismic response of two dimensional sedimentary deposits with large vertical velocity gradients an extension of the aki larner technique to vertically inhomogeneous media is presented so that vertical velocity gradients may be taken into account in two dimensional models only sh waves are considered here but the theory is valid for p and sv waves as well this method is applied to investigate the seismic response of two dimensional sedimentary deposits with large velocity gradients three different cases are considered a shallow high contrast valley a deep high contrast valley and a deep low contrast valley in each case a comparison is performed with the results of a two dimensional model taking into account only homogeneous sediments and a one dimensional model taking into account the vertical inhomogeneity of sediments the presence of a large velocity gradient does not change a lot the qualitative behavior of a two dimensional deposit local surface waves and or two dimensional resonance patterns are observed as in the case of homogeneous sediments nevertheless the surface waves are much more dispersive with lower phase and group velocities and larger amplitudes only very deep valleys give rise to the development of two dimensional resonance on the other hand the amplifications obtained in such deposits may reach much larger values than those predicted with either two dimensional homogeneous models or one dimensional inhomogeneous models since these results have been obtained for realistic values of valley geometrical and mechanical considerations they should find some application in earthquake engineering or seismic microzonation studies

seismic expression of channel outcrops offset stacked versus amalgamated channel systems abstract forward seismic models of two seismic scale outcrops of different style channel systems have been made to investigate their seismic signature these two outcrops illustrate the geometric end members of channel stacking architecture in response to low and high accommodation space the eocene nohut tepe channel system of the elazig basin in eastern turkey was deposited in an area of high accommodation resulting in an aggradational geometrical offset stacking of channels up against a slope the eocene ainsa ii channel system of the tremp pamplona basin in the spanish pyrenees was deposited in an area of low accommodation resulting in a tabular compound sheet geometry with amalgamated channel bodies separated by clay drapes depth models were drawn from outcrop photos and converted to impedance models by assigning acoustic impedance properties to the sand filled channels and surrounding and interbedded mud and clay layers these were the input for the forward seismic models which constructed various frequency synthetic seismic sections of the two outcrops analysis of the outcrop synthetic seismic identified three distinct reflection configurations type i is characterised by a strong black peak and white trough reflection which is due to a discrete channel body type ii is characterised by multiple offset time stepped black peak reflections that are underlain by one continuous strong white trough reflection which is due to offset stacked channel bodies type iii is characterised by strong black peaks which onlap an underlying continuous white trough reflection caused by the lateral amalgamation of channel bodies these three types of reflection configurations observed on the outcrop synthetic seismic can also be found on actual seismic from channelised turbidite systems which aids in interpreting channel stacking architecture accommodation space prediction and depositional styles from the actual seismic data channel stacking architecture is clearly an important aspect which needs to be considered when making channel system interpretations based on seismic data

isotopic and ionic variations in glacier river water during three contrasting ablation seasons the significance of the baseflow component of glacier river discharge in summer varies with geographical location altitude glacier geometry and glacier size baseflow is maintained by meltwater generated above the transient equilibrium line and by water released from temporary storage on in or beneath the glacier at the norwegian glacier austre okstindbreen where precipitation is generally high throughout the year and the summers are cool and wet observations in three successive but contrasting years have shown that na ion concentrations in the glacier river water are influenced strongly by the amount of snowmelt this itself depends on the preceding winter conditions which determine the amount of accumulation and on the current summer s weather the efficiency of the glacier s drainage systems depends on the general progress of summer ablation the speed with which the systems develop influences ion provision from subglacial sources ca 2 ion concentrations are largely determined by subglacial conditions oxygen isotope variations in glacier river water reflect the relative contributions made to total discharge by snow meltwater and other sources the composition of the snow cover which is a function of winter temperatures has a strong influence ice meltwater has low isotopic variability but the isotopic composition of rainfall varies markedly a simple model of mixing of englacial and subglacial waters each of a constant composition cannot be applied to a high latitude glacier of the size and altitudinal range of austre okstindbreen

sedimentary and tectonic evolution of plio pleistocene alluvial and lacustrine deposits of fucino basin central italy abstract the fucino basin was the greatest lake of the central italy which was completely drained at the end of 19th century the basin is an intramontane half graben filled by plio quaternary alluvial and lacustrine deposits located in the central part of the apennines chain which was formed in upper pliocene and in quaternary time by the extensional tectonic activity the analysis of the geological surface data allows the definition of several stratigraphic units grouped in lower units and upper units the lower units upper pliocene are exposed along the northern and north eastern basin margins they consist of open to marginal lacustrine deposits breccia deposits and fluvial deposits the upper units lower pliocene holocene consist of interbedded marginal lacustrine deposits and fluvial deposits thick coarse grained fan delta deposits are interfingered at the foot of the main relief with fluvial lacustrine deposits most of the thickness of the lacustrine sequences more than 1000 m thick is buried below the central part of the fucino plain the basin is bounded by e w wsw ene and nw se fault systems velino magnola fault e w and tremonti celano aielli fault wsw ene and s potito celano fault nw se in the north the trasacco fault the pescina celano fault and the serrone fault nw se in the south east the geometry and kinematic indicators of these faults indicate normal or oblique movements the study of industrial seismic profiles across the fucino basin gives a clear picture of the subsurface basin geometry the basin shows triangular shaped basin fill geometry with the maximum deposits thickness toward the main east boundary fault zones that dip south westward serrone fault trasacco fault pescina celano fault on the basis of geological surface data borehole stratigraphy and seismic data analysis it is possible to recognize and to correlate sedimentary and seismic facies the bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of meso cenozoic carbonate rocks the shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the nw se boundary faults in fact the continental deposits are frequently in on lap contact over the carbonate substratum several disconformable contacts occurred during the sedimentary evolution of the basin the main faults with antithetic and synthetic fault planes displace the whole sedimentary sequence up to the surface indicating a recent faults activity 1915 avezzano earthquake ms 7 0 the stratigraphic and tectonic setting of the fucino basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural sedimentary evolution of the plio quaternary deposits the geometry of the depositional bodies of the fault planes and their relationships indicate that the fucino basin was formed as a half graben type structure during plio quaternary extensional events some internal complexities are probably related to the fold and thrust structures of the apenninic orogeny formed in messinian time in this area and to a different activity timing of the e w and wsw ene fault systems and the nw se fault systems we believe based on the similarity of the surface characteristics that the structural setting of the fucino basin can be extrapolated to the other great intramontane basins in central italy e g rieti l aquila sulmona sora isernia basins

the 2009 l aquila central italy mw6 3 earthquake main shock and aftershocks 1 a m w 6 3 earthquake struck on april 6 2009 the abruzzi region central italy producing vast damage in the l aquila town and surroundings in this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks the distribution of aftershocks 712 selected events with m l 2 3 and 20 with m l 4 0 defines a complex 40 km long nw trending extensional structure the main shock fault segment extends for 15 18 km and dips at 45 to the sw between 10 and 2 km depth the extent of aftershocks coincides with the surface trace of the paganica fault a poorly known normal fault that after the event has been quoted to accommodate the extension of the area we observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes

effects of topography on seismic wave propagation an example from northern taiwan topography influences ground motion and in general increases the amplitude of shaking at mountain tops and ridges whereas valleys have reduced ground motions as is observed from data recorded during and after real earthquakes and from numerical simulations however recent publications have focused mainly on the implications for ground motion in the mountainous regions themselves whereas the impact on surrounding low lying areas has received less attention here we develop a new spectral element mesh implementation to accommodate realistic topography as well as the complex shape of the taipei sedimentary basin which is located close to the central mountain range in northern taiwan spectral element numerical simulations indicate that high resolution topography can change peak ground velocity pgv values in mountainous areas by 50 compared to a half space response we further demonstrate that large scale topography can affect the propagation of seismic waves in nearby areas for example if a shallow earthquake occurs in the i lan region of taiwan the central mountain range will significantly scatter the surface waves and will in turn reduce the amplitude of ground motion in the taipei basin however as the hypocenter moves deeper topography scatters body waves which subsequently propagate as surface waves into the basin these waves continue to interact with the basin and the surrounding mountains finally resulting in complex amplification patterns in taipei city with an overall pgv increase of more than 50 for realistic subduction zone earthquake scenarios off the northeast coast of taiwan the effects of topography on ground motion in both the mountains and the taipei basin vary and depend on the rupture process the complex interactions that can occur between mountains and surrounding areas especially sedimentary basins illustrate the fact that topography should be taken into account when assessing seismic hazard

geometry and evolution of a fault controlled quaternary basin by means of tdem and single station ambient vibration surveys the example of the 2009 l aquila earthquake area central italy we applied a joint survey approach integrating time domain electromagnetic soundings and single station ambient vibration surveys in the middle aterno valley mav an intermontane basin in central italy and the locus of the 2009 l aquila earthquake by imaging the buried interface between the infilling deposits and the top of the pre quaternary bedrock we reveal the 3 d basin geometry and gain insights into the long term basin evolution we reconstruct a complex subsurface architecture characterized by three main depocenters separated by thresholds basin infill thickness varies from 200 300 m in the north to more than 450 m to the southeast our subsurface model suggests a strong structural control on the architecture of the basin and highlights that the mav experienced considerable modifications in its architecture over time the buried shape of the mav suggests a recent and still ongoing predominant tectonic control by the nw se trending paganica san demetrio fault system psdfs which cross cuts older ca ene and nne trending extensional faults furthermore we postulate that the present day arrangement of the psdfs is the result of the linkage of two previously isolated fault segments we provide constraints on the location of the southeastern boundary of the psdfs defining an overall 19 km long fault system this allows for earthquakes larger than m6 5 this study emphasizes the benefit of combining two easily deployable geophysical methods for reconstructing the 3 d geometry of a tectonically controlled basin our joint approach provided us with a consistent match between these two independent estimations of the basin substratum depth within 15

the 2009 central italy earthquake seen through 0 5 myr long tectonic history of the l aquila faults system abstract on 6 april 2009 a mw 6 3 earthquake struck l aquila and dozens of neighbouring villages abruzzo central italy causing 308 deaths and with thousands injured within italian seismicity this was the strongest event since 1980 irpinia mw 6 9 and the first located so close to a large city since 1908 messina mw 7 3 consistent data from an integrated approach including stratigraphy geomorphology tephrochronology and paleoseismology have allowed us to identify a 19 km long hitherto poorly known structure as being responsible for this earthquake paganica san demetrio fault system psdfs the fingerprinting of four well dated tephra layers and a detailed outline of the geomorphological and stratigraphic setting have provided the basis for assessing the behaviour of the psdfs since its early activity here dated at least ca 500 ka to the present the slip rate of the structure calculated over different time windows has fluctuated slightly ca 0 5 mm yr paleoseismological analyses revealed the traces of the last surface faulting events thus we unambiguously recognise the offset associated with the mw 6 7 earthquake of 1703 which was previously related to other conterminous structures along with an older comparable strong event speculatively ascribed to an event purely known as the ad 801 central apennine earthquake this study shows that a long term to short term integrated approach is crucial in seismic hazard evaluation especially when dealing with fault systems that are difficult to trace geomorphically despite being capable of generating 2009 like earthquakes or even stronger events when conterminous structures are also involved

solute acquisition in glacial melt waters i fjallsjokull south east iceland bulk melt waters with closed system characteristics l etude de la composition des eaux de surface cations alcalinite sulfates et ph montre des modifications par rapport aux precipitations par l acquisition de substances dissoutes provenant de l alteration et de la dissolution de debris rocheux dans un systeme ouvert aux gaz carbonique atmospherique les eaux resurgentes ont des compositions variables calcite qui peuvent provenir de l eau de surface

comments on the use of chemically based mixing models in glacier hydrology the assumptions involved in the use of chemically based mixing models for analysis of flow routing of meltwaters in glacierized basins are critically evaluated the assumption that glacial drainage systems consist of only two primary flow components is arbitrary and must be supported by independent evidence recent studies of the processes by which meltwaters acquire solute indicate that the assumption that flow components have unique and constant chemical compositions is unlikely to lie correct source water composition and weathering potential will vary over the course of a melt season and the extent of subglacial weathering is strongly dependent upon such factors as meltwater residence time and the availability of reactive sediment both of which are known to vary on diurnal to seasonal time scales mixing of flow components does not appear to be confined to the terminal regions of glaciers and is therefore unlikely to be conservative as assumed a multi parameter mixing model is applied to the analysis of data on the chemistry of waters sampled from bureholes drilled through haut glacier d arolla switzerland to demonstrate the range of dissolved species for which the assumption of conservative mixing is violated the consequences of this violation for quantitative hydrograph separation are shown to be highly significant the utility of mixing models as a tool for the investigation of glacier hydrological systems is questionable and the results of previous studies are unreliable

fault and basin depocentre migration over the last 2 ma in the l aquila 2009 earthquake region central italian apennines abstract morphological stratigraphical and structural investigations integrated with palaeomagnetic and tephrostratigraphic studies and 40 ar 39 ar measurements allowed us to define the quaternary tectonic sedimentary evolution of the epicentral area of the l aquila 2009 earthquake m w 6 3 this area roughly matches the paganica san demetrio castelnuovo psc intermountain basin filled by a fluvio lacustrine succession that is variously deformed by normal faults at its early stage early pleistocene ca 2 ma the basin hosted a lake that was characterised by whitish carbonate silt and mud deposition towards the end of the early pleistocene this was partly filled by a south eastward prograding deltaic system the south easternmost portion of the deltaic system was successively abandoned and eroded while sedimentation of a braided river system developed in a smaller area westwards before 780 ka this fluvio lacustrine system the lower psc syntheme ended and the area underwent erosional and pedogenic processes these processes continued up to 460 ka with the onset of fluvial gravel and volcanic rich silty sand deposition over a narrow area of the south western psc basin an earlier unit of the upper psc syntheme early middle pleistocene around 460 ka when most of this area was again subjected to denudational processes the sedimentation migrated into the previously exposed north western area of the psc basin where fluvial alluvial sediments were deposited between ca 460 ka and ca 350 ka a later unit of the upper psc syntheme between ca 350 ka and the present the sedimentation continued uninterrupted in a slight westwards restricted area of the psc basin upper late psc syntheme the significant contraction of the basin the shifting of its depocentre the variation in its geometry and in the spatial distributions and thicknesses of the units constituting the lower upper and late psc synthemes provide evidence for strong tectonic control this resulted in progressive reduction of the activity of the south easternmost tectonic structures and parallel migration of the fault activity on the westernmost structures in this perspective the fault system responsible for the l aquila 2009 earthquake can be seen as the most recent expression of a long lasting westwards polarised process of tectonic activity transfer

geochemical weathering at the bed of haut glacier d arolla switzerland a new model waters were sampled from 17 boreholes at haut glacier d arolla during the 1993 and 1994 ablation seasons three types of concentrated subglacial water were identified based on the relative proportions of ca 2c h co 3 and so4 2 to si type a waters are the most solute rich and have the lowest relative proportion of si they are believed to form in hydrologically inefficient areas of a distributed drainage system most solute is obtained from coupled sulphide oxidation and carbonate dissolution so cd it is possible that there is a subglacial source of o2 perhaps from gas bubbles released during regelation because the high so4 2 levels found up to 1200 eq l are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 c c 414 eq l a more likely alternative is that sulphide is oxidized by fe 3c in anoxic environments if this is the case exchange reactions involving fe iii and fe ii from silicates are possible these have the potential to generate relatively high concentrations of hco3 with respect to so4 2 formation of secondary weathering products such as clays may explain the low si concentrations of type a waters type b waters were the most frequently sampled subglacial water they are believed to be representative of waters flowing in more efficient parts of a distributed drainage system residence time and reaction kinetics help determine the solute composition of these waters the initial water rock reactions are carbonate and silicate hydrolysis and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites hydrolysis is followed by so cd the so4 2 concentrations usually are 414 eq l although some range up to 580 eq l which suggests that elements of the distributed drainage system may become anoxic type c waters were the most dilute yet they were very turbid their chemical composition is characterized by low so4 2 h co3 ratios and high ph type c waters were usually artefacts of the borehole chemical weathering environment true type c waters are believed to flow through sulphide poor basal debris particularly in the channel marginal zone the composition of bulk runoff was most similar to diluted type b waters at high discharge and was similar to a mixture of type b and c waters at lower discharge these observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric co2 t he progression of reactions is from carbonate and silicate hydrolysis through sulphide oxidation by first oxygen and then fe iii which drives further carbonate and silicate weathering a crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 1 we speculate that microbial oxidation of organic carbon also may occur both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions hence we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric co2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity which catalyses the reduction of fe iii and the oxidation of fes2 copyright 2002 john wiley sons ltd

high resolution seismic reflection exploration for evaluating the seismic hazard in a plio quaternary intermontane basin l aquila downtown central italy abstract on april 6 2009 a mw 6 1 earthquake struck the plio quaternary intermontane l aquila scoppito basin in central italy causing severe damage to l aquila historical downtown and surroundings which were affected by notable site effects previous work has suggested that different site effects may be related to the complex subsurface geologic architecture given the variable thickness and lithology of l aquila scoppito basin filling deposits on top of which the city was built to improve the 3d geological model of l aquila downtown for seismic site response evaluation and to estimate the seismic hazard of possible buried active normal faults a multitask project was carried out consisting mainly of the integration of surface geology geological subsurface datasets and geophysical surveys data were interpreted with the aim of creating and building a detailed stratigraphic and tectonic model for the plio quaternary cover of the continental basin and the buried morphology of the meso cenozoic bedrock we discuss and interpret the results concerning a 1 km long high resolution seismic reflection profile and refraction tomography integrated with stratigraphy from deep and shallow boreholes the results allowed the reconstruction of the plio quaternary succession below l aquila downtown the plio quaternary basin depocentre is located in a minor nnw sse graben an extensional structure within the main regional graben that borders l aquila scoppito basin finally data interpretation allowed us to define the subsoil geological model of the study area to evidence the recent activity of several faults and to reconstruct the plio quaternary tectono stratigraphic evolution of the basin together the data are useful to evaluate the seismic hazard of cities with great cultural heritage of central italy such as the case study of l aquila downtown

hydrochemistry of carbonate terrains in alpine glacial settings nearly 200 analyses of meltwaters ice and snow from three alpine glacial sites in carbonate terrain are summarized and discussed in terms of sources of solutes and kinetic controls on the progress of weathering reactions most data derive from the swiss glacier de tsanfleuron which is based on cretaceous and tertiary pure and impure limestones two other sites marmolada italian dolomites and the saskatchewan glacier alberta are based on a mixed calcitic dolomitic substrate most solutes originate from carbonate dissolution moreover where pyrite is present its oxidation supplies significant sulphate and forces more dissolution of carbonate the ratios sr2 ca2 and mg2 ca2 are much higher in tsanfleuron melt waters than local bedrock a phenomenon that can be reproduced in the laboratory at small percentages of dissolution these anomalous ratios are attributed to incongruent dissolution of traces of the metastable carbonates mg calcite and aragonite these phases also provide na to solution k is argued to originate mainly by ion exchange on clays with solute ca2 quartz and very minor feldspar dissolution are also inferred locally enhanced input from atmospheric sources is recognized by high cl and associated na the progress of weathering reactions has been evaluated by the trends in the data computer modelling and some simple laboratory experiments the most dilute samples show a trend towards removal of co2 to low partial pressures c 10 5 5 atmospheres reflecting initially rapid carbonate dissolution and relatively slow dissolution of gaseous co2 later addition of atmospheric co2 or acid from pyrite oxidation allows further carbonate dissolution but solutions show a wide range of saturations and co2 pressures as high as 10 2 2 where pyrite oxidation is important in a carbonate terrain measurement of electroconductivity corrected to 25 c and alkalinity in the field allows the following preliminary deductions where meq stands for milliequivalents formula presented where s is the minimum meq ca2 mg2 produced by simple dissolution of carbonate unconnected with pyrite oxidation as with any proxy method these deductions do not remove the need for chemical analysis of waters in a given study area copyright 1994 john wiley sons ltd

new insights into the onset and evolution of the central apennine extensional intermontane basins based on the tectonically active l aquila basin central italy study of the tectonically active l aquila basin offers new insights into both the creation of the extensional intermontane basins of the central apennines of italy and their tectono sedimentary evolution through time the combination of large mammal remains ostracods molluscs mousterian tools and 14 c dating allows better definition of the onset and stratigraphic evolution of the l aquila basin interpretation of a seismic reflection profile and well log data allow evaluation of the subsurface setting of this sedimentary basin and its tectono sedimentary evolution the occurrence of a wedge shaped seismic unit at the base of the basin sedimentary succession defines the first phase of basin fill during a late piacenzian gelasian synrift stage activity along the main fault of the extensional fault system responsible for the onset and subsequent development of the western sector of the l aquila basin l aquila scoppito subbasin migrated from southwest to northeast reaching the presently active mount pettino normal fault only in the late pleistocene holocene the onset of sedimentation in the l aquila basin was synchronous with the onset in the tiberino basin and so the idea that these extensional gsa bulletin month month 2017 v 129 no intermontane basins become progressively younger from the tyrrhenian toward the adriatic side of the central apennines is rejected in the northern and central apen nines only two major syndepositional ex tensional domains can be recognized a late miocene rifting area which includes all the late miocene extensional basins in tuscany and a late pliocene to earliest pleistocene rifting area which possibly includes all the intermontane basins from the tiberino basin to the sulmona basin the different time gaps between compressional and exten sional deformation at any given locality in the central apennines could indicate a partial decoupling of processes responsible for the migration of shortening and extension toward the foreland diachroneity between the eastward migration of shortening in the foreland and extension in the inner part of the orogen supports the notion that the central apennines were created as a result of a partially decoupled collision zone study of the onset of the central apennine extensional intermontane basins together with their seismic activity indicates that the central apennine postorogenic extensional domain represents an archive of 3 m y of continued crustal extension these findings help to refine models of the long term extensional rate of the central apennines and they provide a basis for more reliable seismotectonic models for one of the most seismically active sectors of the central mediterranean area

hydrochemical analysis of spatial and temporal variations of solute composition in surface and subsurface waters of a high arctic catchment abstract spatial and seasonal variations of solute composition were studied in different compartments of a partly glaciated arctic catchment at liefdefjorden nw spitsbergen main emphasis was put on the snowmelt period from june till end of july water samples were taken periodically from soils along longitudinal streamwater profiles and from surface runoff concentrations of total monomeric al c altot in soil solutions were generally low and were below the detection limit of a modified hydroxychinolin method in surface waters comparing these concentrations withc altot in pristine and strong acid influenced areas of temperate latitudes no signs of an exhaustion of geochemical buffer systems could be assessed in this arctic catchment spatial variations in bulk ion composition of soil solutions exceeded seasonal variations during snow melt spatial variations could not be attributed to hillslope position of soil sampling sites thus spatial heterogeneity of rock mineralogy and soil substrates determined soil solution composition bulk ion composition strongly pointed to calcite dissolution as the dominant geochemical process thereby dissolution is enhanced by biologically produced co2 in areas with continuous vegetation cover in soil solutions co2 oversaturation reached maximum values of 20 fold the mean atmospheric partial pressure of co2 ion composition along longitudinal stream water profiles revealed seasonal as well as spatial trends solute enriched subsurface flow contributed significantly to total discharge in the biologically active part of the catchment during mid melting season precipitation events at late summer displaced solute enriched subsurface waters from the active layer resulting in maximum solute concentrations in stream water

a micromorphological index of soil development for the quaternary geology research abstract profile development indices of harden harden j w 1982 a quantitative index of soil development from field examples from a chronosequence in central california geoderma 285 1 98 and ferrari and magaldi ferrari g magaldi d 1983 significato ed applicazioni della paleopedologia nella stratigrafia del quaternario boll mus civ st nat verona 10 315 340 have shown their utility for comparative dating of some paleosols during geomorphological and geological surveys in italy and other countries pedostratigraphic methods have been commonly applied to soil profiles formed in continental formations unfortunately buried and relict paleosols are very scarce or badly preserved in some areas of italy due to past and recent tectonic activity and to strong human impact dating back to prehistoric times in order to use relict paleosols for correct chronostratigraphic interpretation of relict paleosols and in order to correlate them with old landscape forms for the reconstruction of quaternary sequences a new micromorphological index misodi for assessing soil development and degree of weathering was devised the index was tested in the extensional tectonic basin of l aquila scoppito abruzzi central italy where some chronostratigraphic information is available results demonstrate that there is a good relationship between presumed relative age of paleosols and degree of weathering and pedogenesis in b and b c horizons as assessed by this index the index has the potential to be adapted for application to other paleosol types in other countries

the composition of the englacial and subglacial component in bulk meltwaters draining the gornergletscher switzerland a new method of hydrograph separation for bulk meltwaters draining alpine glaciers is proposed it is based on the two component subglacial and englacial mixing model of collins 1978 but allows the composition of the subglacial component to vary between ascending and descending lines of the hydrograph the mean englacial component can be derived from linear relationships between sulphate concentrations and other ions in bulk meltwaters on certain occasions during the ablation season the maximum concentration of ions in the subglacial component can be determined from the linear relationship between bulk meltwater sulphate concentrations and discharge the bulk discharge is then a direct measure of the mass fraction of the englacial component at maximum discharge the contribution of the subglacial component approaches zero which has implications for the storage and mixing of waters in subglacial reservoirs further the subglacial component is not of constant composition and may itself be a mixture of dilute supraglacial and concentrated subglacial water

the impact of supraglacial debris on proglacial runoff and water chemistry debris is known to influence the ablation topography and hydrological systems of glaciers this paper determines for the first time how these influences impact on bulk water routing and the proglacial runoff signal using analyses of supraglacial and proglacial water chemistry and proglacial discharge at miage glacier italian alps debris does influence the supraglacial water chemistry but the inefficient subglacial system beneath the debris covered zone also plays a role in increasing the ion contribution to the proglacial stream daily hydrographs had a lower amplitude and later discharge peak compared to clean glaciers and fewer diurnal hydrographs were found compared to similar analysis for haut glacier d arolla we attribute these observations to the attenuating effect of the debris on ablation smaller input streams on the debris covered area a less efficient subglacial system and possible leakage into a raised sediment bed beneath the glacier strongly diurnal hydrographs are constrained to periods with warmer than average conditions average weather conditions result in a hydrograph with reverse asymmetry conductivity and discharge commonly show anti clockwise hysteresis suggesting the more dilute rapidly routed melt component from the mid glacier peaks before the discharge peak with components from higher up glacier and the debris covered areas arriving later at the proglacial stream the results of this study could lead to a greater understanding of the hydrological structure of other debris covered glaciers with findings highlighting the need to include the influence of the debris cover within future models of debris covered glacier runoff

soft sediment deformation structures interpreted as seismites in lacustrine sediments of the prebetic zone se spain and their potential use as indicators of earthquake magnitudes during the late miocene lacustrine formations of late miocene age in the prebetic area se spain show several types of deformational structures that are interpreted as seismites they are present in both marginal and deep lacustrine facies seismites formed in marginal lake environments comprise sand dikes pillows and intruded and fractured gravels in deep lacustrine facies the seismites are represented by pseudonodules mushroom like silts protruding into laminites mixed layers disturbed varved lamination and loop bedding the measured orientations of these structures are consistent with the orientations of the main faults limiting the basins showing that their origin is clearly related to the tectonic stress field that prevailed in the region during the late miocene the magnitudes of the earthquakes that deformed the sediments have been estimated after published data from both ancient and recent lake deposits accumulated in tectonic active regions elsewhere a rank of earthquake magnitudes with two end members i e the lowest magnitudes recorded by loop bedding in laminites and the highest magnitudes represented by intruded and fractured gravels is proposed

resolution of ambiguities of seismic refraction traveltime curves ambiguities are inherent in seismic refraction traveltime curves based on first arrivals recorded from a multi layered medium even for reversed profiles inflections of traveltime curves caused by the onset of arrivals from successively deeper horizons frequently cannot be delineated from those caused by lateral geologic changes in addition the secondary arrivals which may represent essential portions of a traveltime curve are not available numerous inversions having different geologic implications are possible ambiguities may be resolved by using multiple shotpoints for each spread and combining their individual first arrival traveltime curves to yield a consistent set of curves for each refracting horizon a set of rules applies for combining individual traveltime curves based on reversed split and offset profile configurations the combined curves lend themselves to a unique inversion