changes in the salinity and porosity of sea ice samples during shipping and storage a theoreti cal examination of salinity and porosity changes introduced in sea ice samples by brine expulsion and gas entrapment caused by thermal cycling during shipping and storage shows that in extreme cases such effects can be significant resulting in 15 reductions in porosity 1 more representative scenarios give porosity changes of less than 2 which assuming that ice property variations scale with n 1 2 result in property variations of less than 1

an integrated geophysical investigation of the upper crust in the epicentral area of the 1980 ms 6 9 irpinia earthquake southern italy in this paper we investigate the upper crustal structure of the irpinia region southern apennines thrust belt italy through analysis and joint interpretation of gravity data seismic reflection lines and subsurface information from many deep wells the investigated region includes the epicentral area of the 1980 ms 6 9 irpinia earthquake and is one of the italian regions with the highest seismic hazard the upper crustal structure is imaged by modeling a series of 15 sw trending gravity profiles spaced about 5 km apart plentifully constrained by seismic reflection lines and wells thus reducing the inherent ambiguity of the gravity modeling despite of the complexity of the modeled bouguer anomalies the application of a calibrating procedure to constrain the range of variability of the density values as well as the use of geometric constraints results in a good level of stability in the final density cross sections which in fact appear coherent both in the density values and in the geometrical features the inferred model shows important lateral density variations that can be mostly related to nw trending geologic structures high density bodies delineate carbonate platform thrust sheets and broad antiforms involving mesozoic basinal rocks while low density shallow bodies are associated with pliocene basins in addition important density i e lithological variations are evident along the strike of the range the most relevant being an abrupt deepening of the apulia carbonate platform in the southeastern part of the investigated region in the epicentral region of the 1980 event we find that the geometry of the high density high velocity carbonates of the apulia platform appears correlated with the distribution of the aftershocks and with the p wave velocity anomaly pattern as inferred from a previous local earthquake tomography the structural highs of the apulia platform correspond to high velocity regions where aftershocks and coseismic slip of the mainshock are concentrated this correlation suggests that the apulia carbonate platform geometry played an important role in the rupture propagation and in the aftershock distribution

seismic imaging of complex structures by non linear traveltime inversion of dense wide angle data application to a thrust belt summary we have used a dense wide angle data set to test a two step procedure for the separate inversion of first arrival and reflection traveltimes data were collected in a complex thrust belt environment southern italy along a 14 km line with closely spaced sources 60 m and receivers 90 m we have applied a fully non linear tomographic technique specially designed to image complex structures to over 6400 first arrival traveltimes in order to determine a detailed velocity model a bi cubic spline velocity model parametrization is used the inversion strategy follows a multiscale approach and employs a non linear velocity optimization scheme the tomographic velocity model is adopted as the background reference medium for a subsequent interface inversion aimed at imaging a target upper crust reflector the interface inversion method is also based on a multiscale approach and uses a non linear technique for model parameters interface position nodes optimization we have applied the interface inversion method to over 1600 reflection traveltimes of a target event picked both in the near and in the wide angle offset range the retrieved interface is well resolved in the central part of the model where ray coverage mainly includes clear post critical reflections and the background velocity model is accurate in depth thanks to large offset deep turning rays the velocity and interface models thus determined are consistent with vertical seismic profiling data and correlate well with the geometry of known geological structures this study shows that the used inversion approach is efficient for target orientated investigations in complex geological environments

spatial prediction of river channel topography by kriging topographic information is fundamental to geomorphic inquiry and spatial prediction of bed elevation from irregular survey data is an important component of many reach scale studies kriging is a geostatistical technique for obtaining these predictions along with measures of their reliability and this paper outlines a specialized framework intended for application to river channels our modular approach includes an algorithm for transforming the coordinates of data and prediction locations to a channel centered coordinate system several different methods of representing the trend component of topographic variation and search strategies that incorporate geomorphic information to determine which survey data are used to make a prediction at a specific location for example a relationship between curvature and the lateral position of maximum depth can be used to include cross sectional asymmetry in a two dimensional trend surface model and topographic breaklines can be used to restrict which data are retained in a local neighborhood around each prediction location using survey data from a restored gravel bed river we demonstrate how transformation to the channel centered coordinate system facilitates interpretation of the variogram a statistical model of reach scale spatial structure used in kriging and how the choice of a trend model affects the variogram of the residuals from that trend similarly we show how decomposing kriging predictions into their trend and residual components can yield useful information on channel morphology cross validation analyses involving different data configurations and kriging variants indicate that kriging is quite robust and that survey density is the primary control on the accuracy of bed elevation predictions the root mean square error of these predictions is directly proportional to the spacing between surveyed cross sections even in a reconfigured channel with a relatively simple morphology sophisticated methods of spatial prediction are no substitute for field data copyright 2007 john wiley sons ltd

ionian marine terraces of southern italy insights into the quaternary tectonic evolution of the area 1 new detailed morphotectonic analyses of a well exposed flight of marine terraces along the ionian coast of southern italy has been carried out the area represents a key transect for investigating the middle late quaternary evolution of the southern apennines chain foredeep foreland geodynamic system a major result of the research is the reconstruction of a virtually complete 3d geometry of the marine surfaces along a coastal sector of ca 70 km which 1 documents the occurrence of 18 paleo shorelines and 2 provides evidence for a strong regional uplift affecting the investigated area following a systematic critical review of literature relating to geochronological data integrated with a morphogenetic model based on the interaction between tectonic uplift and eustatic sea level changes the different terraces are correlated to as many highstand sea level peaks dating the highest oldest terrace to ca 600 ka mis 15 the vertical and horizontal distribution of the terraces show a general convergence of the paleo shorelines toward nne which indicates a decreasing trend in differential uplift in that direction ranging from almost 2 mm a in the southwestern sector to about 0 2 mm a in the northeastern sector detailed mapping and 3d reconstruction also emphasize the partitioning of the area into three distinct sectors characterized by different tilting rates this behavior is likely caused by the combined role and activity of three major tectonic structures working at different scales and rates including 1 the reactivation of an out of sequence thrust 2 sliding along the basal detachment of the external apennines wedge and 3 a lithospheric scale duplexing crustal or deeper as a major conclusion within the external sector of the southern apennines chain and its foredeep regional shortening and a contractional tectonic regime persisted throughout the whole quaternary and it is probably still active

new insights into crustal structure cenozoic magmatism co2 degassing and seismogenesis in the southern apennines and irpinia region from local earthquake tomography we present high resolution vp and vp vs models of the southern apennines italy computed using local earthquakes recorded from 2006 to 2011 with a graded inversion scheme that progressively resolves the crustal structure from the large scale of the apennines belt to the local scale of the normal fault system high vp bodies defined in the upper crust and midcrust under the external apennines are interpreted as extensive mafic intrusions revealing anorogenic magmatism episodes that broadened on the adriatic domain during paleogene under the mountain belt a low vp region annular to the neapolitan volcanic district indicates the existence of a thermal fluid anomaly in the midcrust coinciding with a shallow moho and diffuse degassing of deeply derived co2 in the belt axial zone low vp vs gas pressurized rock volumes under the apulian carbonates correlate to high heat flow strong co2 dominated gas emissions of mantle origin and shallow carbonate reservoirs with pressurized co2 gas caps we hypothesize that the pressurized fluid volumes located at the base of the active fault system influence the rupture process of large normal faulting earthquakes like the 1980 mw6 9 irpinia event and that major asperities are confined within the high vp apulian carbonates this study confirms once more that preexisting structures of the pliocene apulian belt controlled the rupture propagation during the irpinia earthquake the main shock broke a 30 km long ne dipping seismogenic structure whereas delayed ruptures both the 20 s and the 40 s subevents developed on antithetic faults reactivating thrust faults located at the eastern edge of the apulian belt

relating arctic ambient noise to thermally induced fracturing of the ice pack thermally induced stresses within pack ice floes are simulated using a viscoelastic model that accounts for the time variation of the atmospheric forcing parameters and the temporal and spatial variations of snow cover to relate the model predicted stresses to the observed 500 hz under ice noise variations a fracturing paradigm was developed the fracturing paradigm includes factors related to ice tensile strength given its salinity and temperature and stress relief as a result of fracturing a fracture count time history was produced using the thermal stress model and the fracturing paradigm for the fall of 1988 in the eastern arctic ocean the results were compared with the observed 500 hz noise the fracture count shows increases for 11 of 13 under ice noise episodes most of the observed under ice noise episodes were of the type identified in previous studies i e those associated with nightly cooling in addition this study identifies under ice noise episodes related to longer term occurrences a

polyphase out of sequence thrusting and occurrence of marble detritus within the wedge top basin deposits in the mt massico southern apennines insights into the late miocene tectonic evolution of the central mediterranean we present a geological survey of the southwestern sector of the mt massico southern apennines which allowed us to reconstruct the stratigraphy and tectonic architecture of this area the mt massico is a key area to study the out of sequence thrusting stage that affected the southern apennine chain since the late miocene which despite the wide occurrence of these structures in the whole chain is a tectonic process up to now poorly investigated this area deserves to be analyzed also for the occurrence of marble detritus within a wedge top basin deposit representing the only place in the southern apennines where such a kind of metamorphic rocks occurs historically this area is known for the extraction of an ornamental stone named mondragone marble the marble is hosted as olistoliths and clasts within the deposits of the caiazzo fm unconformably covering a jurassic middle miocene succession mostly made of shallow water to deep basin carbonates the wedge top basin deposit mainly consists of a chaotic assemblage of conglomerates olistostromes and olistoliths of meso cenozoic limestones deep basin rocks and marbles embedded in a quartzose matrix the structural setting results from a polyphase deformation related to the superposition of two thrust systems the first thrust system includes a duplex verging to east with the cenozoic carbonates thrusted onto the caiazzo fm and the roof thrust cut by several breaching thrusts the late thrust system encompasses ramp dominated faults verging to the north folds minor thrusts and s c structures are associated with the major compressional structures to date the caiazzo fm and put a temporal constraint to the thrust fault activity we performed a nannoplankton content analysis that furnished for the base of this deposit an age not older than the upper tortonian these out of sequence thrusts hence have acted since the late miocene similar structures are widespread in the southern apennines and are interpreted as the surficial expression of envelopment thrusts formed at deeper structural levels with respect to the thrust front we envisage that the marble and plutonic supply was provided by the mesomediterranean continental crust in the late tortonian when this microcontinent was passing close to the apennine platform domain during its orogenic migration toward se

geostatistical analysis of ground survey elevation data to elucidate spatial and temporal river channel change a digital elevation model dem of a fluvial environment represented landform surface variability well and provided a medium for monitoring morphological change over time elevation was measured above an arbitrary datum using a ground based three dimensional tacheometric survey in two reaches of the river nent uk in july 1998 october 1998 after flood conditions and june 1999 a detailed geostatistical analysis of the elevation data was used to model the spatial variation of elevation and to produce dems in each reach and for each survey period maps of the difference in elevation were produced and volumetric change was calculated for each reach and each survey period the parameters of variogram models were used to describe the morphological character of each reach and to elucidate the linkages between process and the form of channel change operating at different spatial and temporal scales the analysis of channel change on the river nent shows the potential of geostatistics for investigating the magnitude and frequency of geomorphic work in other rivers a flood modified the channel features but low magnitude and high frequency flows rationalized the morphology in spite of relatively small amounts of net flux the channel features changed as a consequence of the reworking of existing material the blocking of chute entrances and redirection of the channel had a considerable effect on the behaviour of the channel such small changes suggested that the distributary system was sensitive to variation in sediment regime plots of the kriging variances against sampling intervals were used to quantify the temporal variation in sampling redundancy ranging between 11 per cent and 93 per cent these curves illustrated the importance of bespoke sampling designs to reduce sampling effort by incorporating anisotropic variation in space and geomorphic information on flow regime variation in the nugget parameter of the variogram models was interpreted as sampling inaccuracy caused by variability in particle size and is believed to be important for future work on surface roughness copyright 2003 john wiley sons ltd

thermomechanics of pack ice a thermodynamic formulation for pack ice is presented that includes a means of relating stresses in floes to thermally induced strain rates the formulation combines some basic thermodynamics as detailed in previous research the mechanics component includes viscous creep and mechanically induced strain rates due to typical floes being too large to bend or twist in response to spatially varying strain rates moreover the rheology quantifies the impact of existing cracks in the floe on the overall strain rate in the floe and the resulting stress state a paradigm is proposed which specifies tensile fracturing and the resulting stress relief as proportional to the amount of existing cracks in the floe and some measure of the tensile strength of the ice this allows the thermomechanical equations to be used for both first year and multiyear floes by differentiating the two by the extent of existing cracks the thermomechanical equations are applied in an inverse fashion to solve for flaw structure for a first year floe as well as a multiyear floe this is done by matching stresses predicted by the thermomechanical equations to observed stresses in the floes the results indicate that the top two thirds of the ice in the first year floe was relatively free of cracks while the bottom third of the floe had cracks covering 50 of the ice in the multiyear floe cracks covered 70 to 90 of the ice in the top two thirds of the floe while the bottom third of the floe had cracks covering 30 of the ice

high resolution seismic tomography across the 1980 ms 6 9 southern italy earthquake fault scarp 1 a high resolution multi fold wide angle seismic survey carried out across the irpinia fault southern italy yields new information about the shallow structure of this normal fault that was reactivated in 1980 the fault zone is imaged to a depth of about 60 m by using a non linear tomographic technique that is specially designed to image strongly heterogeneous media results confirm the location of the fault as previously inferred by a trench excavated in soft soils and clearly delineates a 30 35 m step in the bedrock this single step is indicative of a narrow fault zone which corresponds upward to warped soils exposed in the trench thus demonstrating that the near surface warping is directly related to a brittle faulting in the bedrock assuming that the vertical slip rate yielded by paleoseismic data 0 25 0 35 mm yr has been constant since the fault s inception the latter should date back to about 100 140 kys ago such a young age may explain why the irpinia fault is not associated with evident large scale geomorphic indicators of its activity

observations and modeling of thermally induced stresses in first year sea ice during spring 1992 ice property geophone meteorological and stress data were collected on first year ice southwest of cornwallis island within the canadian archipelago one of the goals of the study was to specify the average characteristics of the ice use these characteristics in a model of thermally induced stresses in the ice and examine the fracturing associated with the occurrence of those stresses the results of simulations with a thermal stress model indicate that stress variations within the ice can be reasonably approximated by a viscoelastic rheology the rheology takes into consideration thermally induced strains generated locally as well as strains generated elsewhere and then mechanically transmitted through the ice the geophone data showed both ice borne and water borne propagation paths for individual fracturing events the data imply a detection radius out to 500 600 m for the ice borne signatures of fractures an investigation of a region after fracturing showed that 1 fracturing occurred in an area with a 10 to 15 cm snow cover 2 the snow cover had been scored down to the surface of the ice and 3 cracks in the ice were found under each location where the snow had been scored the cracks were 5 6 m long and at least 15 cm deep a review of these and other experimental results draw us to the conclusion that the forces required to produce fractures in response to natural forcing is greater for first year floes than for multiyear floes

overthrust imaging with tomo datuming a case study through the use of iterative turning ray tomography followed by wave equation datuming or tomo datuming and prestack depth migration we generate accurate prestack images of seismic data in overthrust areas containing both highly variable near surface velocities and rough topography in tomo datuming we downward continue shot records from the topography to a horizontal datum using velocities estimated from tomography turning ray tomography often provides a more accurate near surface velocity model than that from refraction statics the main advantage of tomo datuming over tomo statics tomography plus static corrections or refraction statics is that instead of applying a vertical time shift to the data tomo datuming propagates the recorded wavefield to the new datum we find that tomo datuming better reconstructs diffractions and reflections subsequently providing better images after migration in the datuming process we use a recursive finite difference fd scheme to extrapolate wavefield withou

high resolution onshore seismic imaging of complex volcanic structures an example from vulcano island italy 1 detailed seismic images of subsurface structures of volcanic calderas are fundamental to improve the structural and volcanological knowledge of these high risk volcanoes however high quality seismic data are difficult to obtain in volcanic areas especially on shore we report the results of a high resolution seismic profiling of the western sector of la fossa caldera vulcano island italy using a high resolution vibrating source and both alternative acquisition and processing techniques we were able to overcome most of the inconvenience caused by volcanic lithotypes this study provides the subsurface distribution of volcanic deposits as well as the recognition of some significant intracaldera structures we located a parasitic vent or hyaloclastite mound buried under la fossa caldera which is dissipating co2 in an area where earthquakes have been recorded at about 1 km depth furthermore the deformation pattern found at the southernmost part of the profile is consistent with a caldera collapse after a dome intrusion the results suggest that the use of high resolution vibrating sources combined with alternative seismic acquisition techniques and nonconventional processing could help to recover detailed information on the shallow structures of volcanic areas

acoustic emission from the arctic ice sheet a theoretical analysis of the sound field in the arctic ocean due to a crack occurring in the ice sheet is given particular attention is paid to the contribution of that field to arctic ocean ambient noise the crack is modeled by an approximate equivalent source and the example chosen represents a small failure of the ice sheet under tension it is shown that if the ice sheet were completely continuous only a very small fraction of the energy released by the crack could be trapped as sound in the surface half channel of the ocean where it would contribute to the ambient noise this suggests that scattering of energetic elastic waves in the ice by natural inhomogeneities may be an important additional mechanism by which acoustic energy can leak into the surface channel the analysis is relevant to acoustic emission from any unbounded elastic plate in contact with two possibly different fluid half spaces

subsurface basin analysis of fault controlled turbidite system in bradano trough southern adriatic foredeep italy subsurface data seismic lines wireline logs cores and drill cuttings from intensive hydrocarbon exploration in the pliocene pleistocene bradano trough were used in performing a three dimensional basin analysis and in reconstructing the time space evolution of the basin a middle pliocene sedimentary system characterizes the hydrocarbon bearing sands of the major gas field of the bradano trough the candela field this system includes two phases of deposition in a migrating basin the first phase of deposition caused by strong subsidence due to continental shortening was accompanied by the influx of large quantities of clastic material the outer part of the basin was filled with turbidites the inner part is characterized by olistostromes formed by gravitational sliding along the slope which progressively prograded basinward the fault controlled bottom physiography acted as a channel for turbidity currents that deposited elongate bodies between the inner slope and the compressional faults growing outward the coarser grained material deposited in the trough by currents onlapped the upthrown flanks of the faults thus providing potential hydrocarbon traps turbidity currents carrying the finer grained material flowed over the fault scarps in the meanti e other external faults were activated as the turbidity currents spilled over the former faults deposition expanded laterally continuous basin subsidence kept pace with deposition and superposed wedges accumulated to a thickness of at least 1 000 m 3 281 ft the second phase of deposition is characterized by a decreasing rate of subsidence currents filled a flat trough with tabular turbidites which accreted longitudinally the sand bodies became more muddy clayey in the distal southern part of the basin at this point the system consisted of a major fan shaped sand body upcurrent downcurrent partially overlapping lobate sand bodies with large lobe fringes migrated transversally the entire fan system was later blanketed with mud and finally with a transient carbonate platform which preceded a new cycle of subsidence

development of channel organization and roughness following sediment pulses in single thread gravel bed rivers large episodic inputs of coarse sediment sediment pulses in forested mountain streams may result in changes in the size and arrangement of bed forms and in channel roughness a conceptual model of channel organization delineates trajectories of response to sediment pulses for many types of gravel bed channels channels exhibited self organizing behavior to various degrees based on channel gradient presence of large in channel wood or other forcing elements the size of the sediment pulse and the number of bed mobilizing flows since disturbance typical channel changes following a sediment pulse were initial decreases in water depth in variability of bed elevations and in the regularity of bed form spacing trajectories of change subsequently showed increased average water depth more variable and complex bed topography and increased uniformity of bed form spacing bed form spacing in streams with abundant forcing elements developed at a shorter spatial scale two to five channel widths than in streams without such forcing mechanisms five to 10 channel widths channel roughness increased as bed forms developed

interpretation of regional aeromagnetic data by the scaling function method the case of southern apennines italy a complex aeromagnetic anomaly in southern apennines italy is analysed and interpreted by a multiscale method based on the scaling function we use multiscale methods allowing analysis of a potential field along ridges which are lines defined by the position of the extrema of the field at the considered scales the method developed and applied in this paper is based on the study of the scaling function of the total magnetic field it allows recovering of source parameters such as depth and structural index the studied area includes a pleistocene volcanic structure mt vulture whose intense dipolar anomaly is superimposed on a longer wavelength regional anomaly the interpretation of ridges of the modulus of the analytic signal at different altitude ranges allows recognition of at least three distinct sources between about 5 km and 20 km depth their interpretation is discussed in light of borehole data and other geophysical constraints a reasonable geological model for these sources indicates the presence of intrusions probably linked to the past activity of mt vulture

temporal and spatial variability in thalweg profiles of a gravel bed river this study used successive longitudinal thalweg profiles in gravel bed rivers to monitor changes in bed topography followingfloodsandassociatedlargesedimentinputs variationsinchannelbedelevations distributionsofresidualwater depths percentage of channellengthoccupied byriffles andaspatial autocorrelationcoefficient moran si wereused to quantify changes in morphological diversity and spatial structure in redwood creek basin northwestern california bed topographyinredwoodcreekanditsmajortributariesconsistsprimarilyofaseriesofpoolsandriffles thesize frequency and spatial distribution of the pools and riffles have changed significantly during the past 20 years following large floods and highsediment input inredwood creek and its tributaries in 1975 variation in channelbed elevations was low and the percentageofthechannellengthoccupiedbyriffleswashigh overthenext20years variationinbedelevationsincreased while the length of channel occupied by riffles decreased an index standard deviation of residual water depth bankfull depth 100 wasdevelopedtocomparevariationsinbedelevationoverarangeofstreamsizes withahigherindexbeing indicativeofgreatermorphologicaldiversity spatialautocorrelationinthebedelevationdatawasapparentatbothfineand coarsescalesinmanyofthethalwegprofilesandtheobservedspatialpatternofbedelevationswasfoundtoberelatedtothe dominant channel material and the time since disturbance river reaches in which forced pools dominated and in which large woody debris and bed particles could not be easily mobilized exhibited a random distribution of bed elevations in contrast in reaches where alternate bars dominated and both wood and gravel were readily transported regularly spaced bed topography developed at a spacing that increased with time since disturbance this pattern of regularly spaced bed featureswasreversedfollowinga12 yearfloodwhenbedelevationsbecamemorerandomlyarranged copyright 1999 john wiley sons ltd

directionality of ice cracking events this paper presents the measured vertical directivity of ice cracking events extracted from a 341 s sample of ambient noise recorded under the polar ice pack the sample was taken with a vertical linear array of four hydrophones suspended over the arctic continental shelf in 500 m of water the hydrophone spacing was 100 m the samples from each hydrophone were bandpass filtered between 40 and 1250 hz and searched for corresponding peaks in the acoustic pressure the acoustic events are believed to be due predominantly to thermal ice cracking the angular distribution of the 765 arrivals detected has its maximum at 15 deg below the horizontal with most of the arrivals occurring between 0 and 25 deg below the horizontal an explanation for this observation is given in terms of a simple ray based model of the propagation of ice cracking noise the asymmetry in the angular distribution is shown to be due mostly to the source directivity favoring bottom reflected and refracted rays arriving at negative angl

advanced three dimensional seismic imaging of deep supercritical geothermal rocks in southern tuscany the seismic k horizon is the key to gaining understanding on the deep supercritical geothermal rocks in southern tuscany the k horizon is hosted in metamorphic rocks which cause strong seismic wavefield scattering resulting in a poor signal to noise ratio our study aims to reveal high resolution seismic images of the k horizon below a geothermal field in southern tuscany using an advanced threedimensional seismic depth imaging approach the key seismic pre processing steps in the time domain include muting a large amount of persistent noise based on the statistical analysis of the seismic amplitudes and tomostatics technique to correct for static effects we carried out seismic depth imaging using kirchhoff pre stack depth migration and fresnel volume migration techniques each migration technique was tested with constant and heterogeneous three dimensional velocity models due to the difficulties in determining emergent angles for this low signal to noise ratio data set the migration results with the heterogeneous three dimensional velocity model show less coherent reflections compared to the migration results using the constant velocity model both velocity models however lead to relatively the same structure and depth of the k horizon indicating the similarity of the average velocities along the wave propagation paths in both velocity models with both velocity models fresnel volume migration yields the k horizon with better reflection coherency and higher signal to noise ratio than standard kirchhoff pre stack depth migration nevertheless both migration techniques have been able to reveal the k horizon with relatively high resolution and provide a reliable basis for geothermal rock characterization as well as steering of the first geothermal well penetrating the k horizon

a geostatistical framework for quantifying the reach scale spatial structure of river morphology 1 variogram models related metrics and relation to channel form abstract fluvial geomorphology is fundamentally concerned with the association between form and process in rivers examining these interactions in complex natural channels requires a means of quantifying the variability and organization of bed topography this paper introduces a geostatistical framework for characterizing reach scale spatial structure transformation to a channel centered coordinate system allows topographic variations to be resolved into along and across stream components dimensionless variables obtained by scaling distances by the mean channel width and de trended elevations by the mean bankfull depth account for channel size and allow spatial patterns to be compared over time or among sites these patterns are effectively described by the variogram a spatial statistic that expresses dissimilarity as a function of distance fitting a parametric model to the sample variogram provides a rich description of channel form for example multiple nested structures can be combined to account for anisotropy with varying degrees of spatial variability observed over different length scales along and across the channel integral metrics derived from the variogram model yield a more compact summary and variogram maps a useful visualization to guide interpretation of these metrics i used a simple channel builder to isolate the effects of specific aspects of river morphology on the variogram this analysis indicated that geostatistical models were sensitive to changes in the size shape and orientation of channel features but not to a pure translation of the morphology the results also highlighted the importance of considering streamwise and transverse components jointly rather than in isolation

crustal structure in the southern apennines from teleseismic receiver functions while the upper crustal structure of the southern apennines is known lack of control on the deep structure allows competing thin skinned and thick skinned models of the orogen in thin skinned models the detachment decouples a stack of rootless nappes from the basement in thick skinned models basement is involved in the most recent phase of thrusting to examine crustal structure we use teleseismic data from the calabria apennine tyrrhenian subductionaccretion collision network cat scan array in southern italy we use receiver functions rf processed into a common conversion point stack to generate images of the crust interpretation and correlation to geological structure are done using inversions of individual station rfs we focus on a shallow discontinuity where p to s conversions occur in the foreland it corresponds to velocity jumps between carbonate and clastic strata with basement a similar interpretation for the apennines provides the most parsimonious explanation and supports a thick skinned interpretation in a thick skinned reconstruction the amount of shortening is much smaller than for a thin skinned model this implies considerably less pliocene pleistocene shortening across the apennines and suggests an east southeast motion of the calabrian arc subparallel to the southern apennines rather than a radial expansion of the arc

upper plate deformation as marker for the northern step fault of the ionian slab tyrrhenian sea central mediterranean abstract the eastern tyrrhenian margin etm the active boundary of the tyrrhenian sea backarc basin is the key for understanding the geodynamics of the central mediterranean numerous seismic tomography studies have been carried out in this region proposing different reconstructions of the lower subducting plate and cause of the slab break off existing beneath the southern apennines however the area and mode of the recent deformation of the tyrrhenian sea are still not fully defined and understood in this study we combine the analysis of a recent seismic tomography model and geological data in order to understand the relationship between the subducting lower plate and the tectonic evolution of the sedimentary basins formed on the upper plate with this aim we interpreted a large data set of seismic reflection profiles and several well logs the results consist in 2d and 3d geological models of the basins sedimentary infill and fault networks taking into account the geological data of the etm and those of the adjacent inner flank of the apennines we observe i a system of linked sedimentary basins developed on a narrow deformation belt bounded by transform fault zones ii a polyphase rifting within the upper plate iii an abrupt change of the direction of extension 90 from ne oriented in the lower pleistocene to se oriented in the middle pleistocene since these etm features are not the typical expressions of the current backarc extensional models we propose a link between the evolution of upper plate and the onset and development of a step subduction transform edge propagator fault along the northern margin of the ionian slab

a conceptual model of the impact of flaws on the stress state of sea ice recent theoretical advances have lead to a rheology for sea ice and an increased understanding of how stresses are generated in an ice floe by thermally induced strain rates one of the underlying assumptions of the ice rheology is that floes in general order of 300 m or greater in diameter are too large to bend or twist in response to vertical or horizontal variations in strain rates in essence there are no nonzero bending moments a numerical model based on this rheology has tieen used to produce good predications of observed ice stresses and times of ice fracturing lewis 1994 lewis et al 1994 on the basis of these results this paper presents a conceptual model of how existing flaws in an ice floe can impact the stress state of the ice while still assuming no bending or twisting of the floe a modified ice rheology is developed which quantifies the extent of existing cracks in the ice and how they impact the overall strain rate within a floe

fault geometries from the space distribution of the 1990 1997 sannio benevento earthquakes inferences on the active deformation in southern apennines in this study we analyze the recent 1990 1997 seismicity that affected the northern sector sannio benevento area of the southern apennines chain we applied the best estimate method bem which collapses hypocentral clouds to the events of low energy md max 4 1 seismic sequences in order to constrain the location and geometry of the seismogenetic structures the results indicate that earthquakes aligned along three main structures two sub parallel structures striking nw se 1990 1992 benevento sequence and one structure striking ne sw 1997 sannio sequence the southernmost nw se structure which dips towards ne overlies the fault that is likely to be responsible for a larger historical earthquake io max xi mcs 1688 earthquake the northernmost nw se striking structure dips towards sw the ne sw striking structure is sub vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake the spatio temporal evolution of the 1990 1997 seismicity indicates a progressive migration from se benevento to nw sannio associated to a deepening of hypocenters i e from about 5 to 12 km hypocenters cluster at the interface between the major structural discontinuities e g pre existing thrust surfaces or within higher rigidity layers e g the apulia carbonates available focal mechanisms from earthquakes occurred on the recognized nw se and ne sw faults are consistent with dip slip normal solutions this evidences the occurrence of coexisting nw se and ne sw extensions in southern apennines

depth and morphology of reflectors from the non linear inversion of arrival times and waveform semblance data part ii modelling and interpretation of real data acquired in southern apennines italy in order to retrieve a 2d background velocity model and to retrieve the geometry and depth of shallow crustal reflectors in the southern apennines thrust belt a separate inversion of first arrival traveltimes and reflected waveforms was performed data were collected during an active seismic experiment in 1999 by enterprise oil italiana and eni agip using a global offset acquisition geometry a total of 284 on land shots were recorded by 201 receivers deployed on an 18 km line oriented sw ne in the val d agri region southern apennines italy the two step procedure allows for the retrieval of a reliable velocity model by using a non linear tomographic inversion and reflected waveform semblance data inversion the tomographic model shows that the p wave velocity field varies vertically from approximately 3 km s to 6 km s within 4 km from the earth s surface moreover at a distance of approximately 11 km along the profile there is an abrupt increase in the velocity field in this zone indeed an ascent from 2 km depth to 0 km above sea level of the 5 2 km s iso velocity contour can be noted the retrieved velocity can be associated with plio pleistocene clastic deposits outcropping in the basin zone and with mesozoic limestone deposits the inversion of waveform semblance data shows that a p to p reflector is retrieved at a depth of approximately 2 km this interface is deeper in the north eastern part of the profile where it reaches 3 km depth and can be associated with a limestone horizon

seismological geological and geophysical constraints for the gualdo tadino fault umbria marche apennines central italy abstract the april 3 1998 mw 5 1 gualdo tadino earthquake central italy was the last significant event in the 6 month long umbria marche seismic crisis this event and its aftershocks occurred in an area where active faulting produces no striking geological and geomorphological effects in this study we investigated the ruptured fault using detailed seismological data and a re processed and re interpreted seismic reflection profile aftershock location and focal mechanisms were used to constrain the geometry and kinematics of the ruptured fault and a comparison was made with the subsurface image provided by the seismic profile we found that the 1998 gualdo tadino earthquake occurred on a wsw dipping normal fault with a length of about 8 km and a relatively gentle dip 30 40 confined between 3 5 and 7 km in depth kinematics of the mainshock and aftershocks revealed a ne trending extension in agreement with the regional stress field active in the northern apennines belt the mw 5 1 earthquake originated above the top of the basement and ruptured within the sedimentary cover which consists of an evaporites carbonates multilayer we hypothesised that the active fault does not reach the surface blind normal fault

neogene quaternary evolution of the offshore sector of the southern apennines accretionary wedge gulf of taranto italy abstract southern apennines represent a collisional orogenic belt whose compressional regime is commonly assumed to have ceased during middle quaternary on the other hand to the south the calabria arc is still characterized by subduction and the principal aim of the present research is to shed some light on the space and time transition from the ceased collision to the active subduction accordingly we investigated the offshore sector of the southern apennines accretionary wedge corresponding to the taranto gulf to gain insights into the offshore accretionary wedge we reconstructed a 3d geological and tectonic model by interpreting a grid of 40 seismic reflection lines 1100 km 80 intersections within an area of ca 104 km2 calibrated with 17 wells the geometric and chronological constraints allow documenting a systematic messinian quaternary thrust migration from internal towards external sectors of the wedge the migrating deformational process was essentially associated with a leading imbricate thrust system with a general ne younging direction where we could recognize and distinguish some major advancing phases characterized by alternating fast thrust propagation events and strain accumulation periods within the wedge this process is well emphasized by the jump of the foredeep and piggy back basins the ne wards wedge migration was also associated with a lithospheric scale flexural folding that generated a set of normal faults striking parallel to the coeval thrusts likely reactivating optimally oriented structures inherited from mesozoic events finally a persisting thrust activity up to the latest quaternary and possibly up to present in correspondence of the externalmost sector of the accretionary wedge has been documented and explained in terms of strain partitioning in the frame of a recent oblique convergence the results of this research have possible implications for the seismic hazard assessment of the broader region which is possibly greater than previously assumed

controlled source nonlinear tomography a powerful tool to constrain tectonic models of the southern apennines orogenic wedge italy the anatomy of the southern apennines is a matter of compelling debate both thick and thin skinned tectonic models are proposed due to paucity of deep seismic constraints we present new and well defined information on the velocity structure of the mountain range by using an innovative nonlinear tomographic technique applied to refraction wide angle reflection data the velocity interface model shows a high velocity region with values exceeding 7 km s at 8 9 km depth such large velocities cannot be related to sedimentary rocks and imply the presence of shallow crystalline rocks i e the basement involvement in the thrust belt the integration of our results with other geophysical data local earthquake tomography bouguer and magnetic anomalies confirms this interpretation which strongly supports thick skinned tectonics and has significant implications for the seismotectonics and hydrocarbon potential of the southern apennines our inversion approach can be effective in other orogenic wedges when seismic reflection profiling fails to uniquely resolve deep complex structures

spatial and source level distributions of ice cracking in the arctic ocean this paper reports measurements of the spatial and source intensity level distributions of ice cracking events occurring in the rough arctic pack ice these distributions are computed from a total of 916 detected events covering approximately 2 h of data distributed over several days during april 1988 measurements were obtained over the frequency band 4 200 hz on a 22 element vertical array and a 7 element horizontal array deployed below the arctic pack ice in 420 m of water the observed spatial distribution of detected events is consistent with the case where ice cracking events are uniformly distributed source levels from 110 to 180 db pa at 1 m were measured the calculated source level distribution for all events approximates a linearly decreasing function on a log db scale of the number of events versus source level the median mean and maximum numbers of events occurring per square kilometer per minute over a 1 db band of source levels centered at 110 db pa at 1 m are approximately 4 8 an

recent large magnitude floods and their impact on valley floor environments of northeastern yellowstone abstract the lamar river watershed of northeastern yellowstone contains some of the most diverse and important habitat in the national park broad glacial valley floors feature grassland winter range for ungulates riparian vegetation that provides food and cover for a variety of species and alluvial channels that are requisite habitat for native fish rapid neogene uplift and quaternary climatic change have created a dynamic modern environment in which catastrophic processes exert a major influence on riverine riparian ecosystems uplift and glacial erosion have generated high local relief and extensive cliffs of friable volcaniclastic bedrock as a result steep tributary basins produce voluminous runoff and sediment during intense precipitation and rapid snowmelt recent major floods on trunk streams deposited extensive overbank gravels that replaced loamy soils on flood plains and allowed conifers to colonize valley floor meadows tree ring dating identifies major floods in 1918 ca 1873 and possibly ca 1790 in 1996 and 1997 discharge during snowmelt runoff on soda butte creek approached the 100 year flood estimated by regional techniques with substantial local bank erosion and channel widening indirect estimates show that peak discharges in 1918 were approximately three times greater than in 1996 with similar duration and much greater flood plain impact nonetheless 1918 peak discharge reconstructions fall well within the range of maximum recorded discharges in relation to basin area in the upper yellowstone region the 1873 and 1918 floods produced lasting impacts on the channel form and flood plain of soda butte creek channels may still be locally enlarged from flood erosion and net downcutting has occurred in some reaches leaving the pre 1790 flood plain abandoned as a terrace gravelly overbank deposits raise flood plain surfaces above levels of frequent inundation and are well drained therefore flood plain soils are drier noncohesive gravels also reduce bank stability and may have persistent effects on channel form overall floods are part of a suite of catastrophic geomorphic processes that exert a very strong influence on landscape patterns and valley floor ecosystems in northeastern yellowstone

pitfalls in three dimensional seismic interpretation footprints of an irregular source receiver layout abstract this paper shows how nonuniform source receiver spacing in a three dimensional 3 d land acquisition creates footprints that could easily be mistaken for geology in a 3 d time migrated seismic volume from the midcontinent united states amplitude extraction along the top of the mississippian limestone formation shows a sinkhole like feature which is justified from a depositional perspective however an inspection of the acquisition layout shows that the sinkhole is a replica of the fold distribution in land surveys where source and receivers seldom have a regular distribution and for unconventional plays that are not developed through patterned drilling a thorough review of processing and acquisition parameters is necessary before interpreting amplitude maps

seismic modeling study of the earth s deep crust we use seismic modeling methods to validate the interpretation of deep crust seismic exploration an approximation of the stacked section is obtained with the nonreflecting wave equation and the exploding reflector approach using this technique and ray tracing algorithms we obtain a geological model by comparing the synthetic section with the real stacked section an isotropic constitutive equation is assumed in this phase the exact synthetic stacked section is then obtained by applying the standard processing sequence to a set of synthetic common shot profiles computed with the variable density acoustic wave equation we introduce elliptical p wave anisotropy and the effects of small scale inhomogeneities by using a von karman autocovariance probability function that simulates scattering q effects verification of the geological model by poststack migration constitutes an additional test the methodology which is suitable for areas of complex geology is applied to a seismic line acquired in the nort

acquisition and processing of high resolution reflection seismic data from a survey within the complex terrain of the bavarian folded molasse a high resolution reflection seismic survey was carried out in the southern part of the bavarian molasse basin in 1998 and 1999 the survey aimed to investigate the near surface structure of the complicated transition from the unfolded foreland molasse to the folded molasse and the folded molasse to the internally complicated thrust systems of the helveticum the ultrahelveticum and the rhenodanubian flysch the study is linked to the transalp seismic project and the results help to fill the gap between the surface and the upper 300 500 ms two way traveltime twt typical of deep reflection seismic experiments the environmental conditions encountered in the study area required that particular attention be paid to the acquisition parameters for the three seismic lines each about 4 km long the energy source was a small vibrator the geophone spread spacing and frequency range were adjusted to image reflectors which were expected to dip steeply southwards in general the unprocessed field records did not show signals that could be attributed to specific reflectors individual trace processing considerably improved the data quality taking into account the influence of the quaternary cover and also the strong lateral velocity variations of the shallow subsurface the effects of the various processing steps such as muting refraction statics residual statics and velocity analysis are discussed to assess the nmo velocities the qualitative analysis of the seismic energy in a common shotpoint gather offered advantages over an analysis in a common midpoint gather or in a stacked section and proved to be very effective as demonstrated along the miesbach 9801 line low velocity zones extend locally down to about 400 ms adjacent to zones of extremely high velocities close to the surface reflecting steeply dipping strata besides the quaternary cover on top the miesbach 9801 and miesbach 9802 lines exhibit many horizontal reflections in places down as far as 1400 ms twt indicating the sedimentary sequences of the unfolded foreland molasse the southern part of both lines is dominated by southward dipping reflection bands indicating units of the folded molasse the reflection pattern shown by the miesbach 9901 line suggests that there is almost no quaternary cover southward dipping elements reflect the internal structure of the folded molasse whereas a rather diffuse reflection signature may be attributed to rhenodanubian flysch units

late quaternary faulting within the southern apennines seismic belt new data from mt marzano area southern italy abstract an integrated geomorphological and geophysical investigation was performed in order to reconstruct the pliocene quaternary geomorphologic evolution and recent tectonics of mt marzano massif southern apennines italy the study area belongs to a region of high seismic energy release the last event being the strong ms 6 9 1980 irpinia earthquake most of the main faults of the area ceased their activity before development of the late pliocene age palaeosurfaces widely spread over the massif beginning in the lower part of the middle pleistocene strong extensional tectonics took place in the southern portion of the massif wnw trending faults created the buccino and s gregorio magno depressions which underwent subsidence until the holocene according to abundant morphostructural evidence during the late quaternary the n150 trending mt valva mt carpineta fault and the n110 100 trending mt ogna fault previously sealed by pliocene palaeosurfaces also were re activated morphostructural data were integrated with a high resolution seismic survey across the piano di pecore basin which is dammed by a fault that slipped 70 cm during the 1980 earthquake this fault produced no more than 50 60 m of throw during quaternary times most probably starting from 100 to 150 kyr bp

deep structure of the southern apennines italy thin skinned or thick skinned 1 the deep structure of the southern apennines sa accretionary wedge is still debated since industrial seismic reflection and well data provide reliable constraints only to a depth of about 10 km as a consequence two directly linked questions regard 1 the shortening in the accretionary prism particularly within the buried apulian thrust units and 2 the degree of involvement of the lower plate basement i e the apulian crystalline basement to address these issues we have constructed a regional section along a recently released deep seismic reflection profile crop 04 which intersects the entire sa the resulting cross section adequately constrained to a depth of about 15 km has been framed in a geodynamic scenario characterized by the eastward roll back of the westward subducting apulo adriatic lithosphere on the basis of this section we speculate on the deep structure building both thin and thick skinned thrust models a cross check of these end members models against documented tectonic geophysical and geochemical features shows that the thin skinned model is generally more consistent with the available data the development of basement slices with thicknesses of tens of kilometers is unlikely while it remains possible that the apulian basement could have been involved with its upper few kilometers in the thin skinned model the total shortening of the allochthonous units i e apennine and apulian carbonate platforms and lagonegro basin is estimated to be greater than 280 300 km some 90 km of shortening can be attributed to the apulian thrust units

methods for monitoring hydroacoustic events using direct and reflected t waves in the indian ocean 1 the recent installation of permanent three element hydrophone arrays in the indian ocean offshore diego garcia and cape leeuwin australia provides an opportunity to study hydroacoustic sources in more detail than previously possible we developed and applied methods for coherent processing of the array data for automated association of signals detected at more than one array and for source location using only direct arrivals and using signals reflected from coastlines and other bathymetric features during the 286 day study 4725 hydroacoustic events were defined and located in the indian and southern oceans events fall into two classes tectonic earthquakes and ice related noise the tectonic earthquakes consist of mid ocean ridge trench and intraplate earthquakes mid ocean ridge earthquakes are the most common tectonic events and often occur in clusters along transform offsets hydroacoustic signal levels for earthquakes in a standard catalog suggest that the hydroacoustic processing threshold for ridge events is one magnitude below the seismic network fewer earthquakes are observed along the java trench than expected because the large bathymetric relief of the source region complicates coupling between seismic and hydroacoustic signals leading to divergent signal characteristics at different stations we located 1843 events along the antarctic coast resulting from various ice noises most likely thermal fracturing and ice ridge forming events reflectors of signals from earthquakes are observed along coastlines the mid indian ocean and ninety east ridges and other bathymetric features reflected signals are used as synthetic stations to reduce location uncertainty and to enable event location with a single station

prestack depth migration of an alberta foothills data set the husky experience we produce depth images for an alberta foothills line by iteratively using a number of migration and velocity analysis techniques in imaging steeply dipping layers of a foothills data set it is apparent that thrust belt geology can violate the conventional assumptions of elevation datum corrections and common midpoint cmp stacking to circumvent these problems we use migration from topography in which we perform prestack depth migration on the data using correct source and receiver elevations migration from topography produces enhanced images of steep shallow reflectors when compared to conventional processing in addition to migration from topography we couple prestack depth migration with the continuous adjustment of velocity depth models a number of criteria are used in doing this these criteria require that our velocity estimates produce a focused image and that migrated depths in common image gathers be independent of source receiver offset velocity models are estimated by a series of iterative and interpretive steps involving prestack migration velocity analysis and structural interpretation overlays of velocity models on depth migrations should generally show consistency between velocity boundaries and reflection depths our preferred seismic depth section has been produced by using prestack reverse time depth migration coupled with careful geological interpretation

seismic exploration in complex terrains a processing experience in the southern apennines we discuss a data processing sequence adopted to reprocess a seismic line that crosses the italian southern apennines from the tyrrhenian sea to the adriatic margin and investigate both the overthrust and foreland areas we first determine the main causes of the very low s n ratio in the field data and then propose a processing sequence aimed at exploiting the signal content also making use of a priori geological knowledge of this area our work indicates a combination of causes for the very low quality of the seismic data these include length of the spread about 20 km that is unfavorable because of the rapid variation in the near surface geology tectonic complexity crooked line acquisition and the rough topography associated with outcropping rocks characterized by highly variable velocities based on the outcome of this data analysis we present a processing sequence driven by knowledge of the regional tectonic setting and by knowledge of the shallow subsurface geology the main effort is in remov

sediment supply and the development of the coarse surface layer in gravel bedded rivers the bed surface of most gravel rivers is considerably coarser than the sub surface or the gravel load transported over it a phenomenon affecting river dynamics morphology and ecology the coarse surface layer often called an armour or pavement has been attributed to an inherent tendency for small grains to settle between larger ones during active transport of all sizes1 2 and to selective erosion or trapping of finer particles when the coarse grains are relatively immobile3 4 where bedload supply is cut off below dams selective erosion causes coarsening5 6 using a simple quantitative model we propose that surface coarsening develops in gravel bedded rivers when local bedload supply from upstream is less than the ability of the flow to transport that load we present laboratory results which support this hypothesis and show that supply reduction causes changes in bedforms and progressive confinement of active bedload transport to a narrow band of finer bed surface bordered by a coarse less active bed it may therefore be possible to relate the degree of river bed surface coarsening to sediment supply resulting from land use

bar resistance in gravel bed streams at bankfull stage total flow resistance in gravel bed streams with high width depth ratios and low sinuosities is primarily a result of grain and bar roughnesses the relative importance of these two roughness elements has not been established the relative importance of grain and bar resistance is examined for 12 straight and divided gravel bed reaches at bankfull stage by using the keulegan equation to determine a resistance division of energy slope the remaining slope is assumed to represent the relative importance of bar resistance bar resistance accounts for 50 to 75 of the total resistance in these reaches calculated values of reach averaged bar slope correlate closely with field measurements of bar magnitude

comparison between reprocessed seismic profiles seismologic and geologic data a case study of the colfiorito earthquake area seismic reflection data are used to reconstruct the subsurface geologic structures below the umbria marche region in italy a highly seismogenic area with a recent history of seismic activity the 1997 1998 colfiorito sequence we reprocess three vibroseis seismic profiles acquired in the early 1980s for hydrocarbon exploration whose stacked sections were optimized for relatively deep oil targets on the reprocessed seismic profile closest to the epicentral area we construct the main reflectors to a depth of about 4 s two way time and compare this interpretation with the available hypocenters of the 1997 earthquakes the improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement rock geometry we find that part of the colfiorito sequence is localized around some of the reflectors in the reflection profile which we interpret as related to the active normal faults

active faults and induced seismicity in the val d agri area southern apennines italy summary the nw se trending val d agri extensional basin is one of the regions in italy with the highest seismogenic potential field data do not univocally define which of the fault systems bordering the basin on the two opposite sides is accommodating the active deformation in this study we detect and locate by using an automatic picking procedure almost 2000 low magnitude earthquakes 0 2 ml 2 7 recorded by a dense network during a 13 months long seismic experiment events are mostly located along the southwestern flank of the basin to the south intense swarm type microseismicity defines a major cluster 5 km wide from 1 to 5 km depth to the west a clear alignment of events characterized by normal faulting kinematics defines a ne dipping normal fault between 1 and 6 km depth the upward continuation of this structure 5 km long matches a mapped active normal fault recognized by field and palaeoseismological surveys a temporal correlation found between the intense swarm type microseismicity and the water level changes in the nearby artificial pertusillo lake suggests that this seismicity is reservoir induced

structural architecture of the central apennines interpretation of the crop 11 seismic profile from the adriatic coast to the orographic divide 1 we present an interpretation of the eastern half portion of the crop 11 line a deep reflection seismic profile 265 km long that cuts across the central apennines from the tyrrhenian coast to the adriatic coast in the study area the line cuts across a pile of thrust sheets that underwent tectonic transport between the messinian and the pleistocene in its easternmost part the line runs through the plio pleistocene deposits of the adriatic foredeep in the foreland region the crop 11 line integrates previous information on the crustal structure derived from petroleum exploration and from deep seismic sounding refraction experiments in particular the crop 11 line confirms the existence of a very thick sedimentary sequence underlying the mesozoic tertiary carbonates of the apulia platform interpreted as the paleozoic triassic sedimentary cover of a pre cambrian crystalline basement in the mountain chain where the base thrust of the orogenic wedge reaches a depth of about 25 km this sedimentary sequence appears to be the deepest geological unit incorporated in the thrust system this interpretation of the crop 11 profile suggests an unusual thin skin tectonic style implying the detachment from the original basement and the incorporation in the post tortonian tectonic wedge of a very thick paleozoic triassic sedimentary sequence possibly affected by low grade metamorphism in the lower part other new suggestions from the crop 11 seismic data concern the origin of the fucino basin one of the most remarkable plio pleistocene intramontane basins the normal faults bordering this structural depression as other important normal faults present in the central apennines e g the caramanico fault system in the majella region seem to have been controlled by gravitational collapse processes driven by uplift during crustal shortening rather than by a generalized extension subsequent to the apennine compression as usually reported in the geological literature if this interpretation is correct the strong seismic activity in correspondence to the apennine watershed may be related to the very recent increase in the structural relief caused by an out of sequence propagation of the active thrusts

pliocene quaternary orogenic systems in central mediterranean the apulia southern apennines tyrrhenian sea example in the central mediterranean the africa eurasia convergence led to the development of complex orogenic systems and backarc basins throughout pliocene quaternary times the southern apennines accretionary prism migrated towards the apulia foreland and contemporaneously the tyrrhenian sea backarc basin opened in this study we investigated the offshore of the southern apulia foreland and the southern apennines using seismic reflection profiles and well data in a dedicated gis software we made a detailed stratigraphic analysis reconstructed the structural pattern and built 2d geological models of the main geological surfaces the structure of the apulia region formed during two main tectonic stages lower pleistocene complex extensional faulting developed in a transtensional regime and middle upper pleistocene transpression shortening the southern apennines accretionary prism developed through the pliocene early lower pleistocene and was overprinted by late lower pleistocene middle pleistocene nw se sinistral faults through linking new data from the accretionary prism and the foreland with previous information from the tyrrhenian sea back arc we provide an original interpretation for the relationships between the various provinces that make the central mediterranean crustal puzzle and reconstruct the main phases of the evolution of its pliocene quaternary orogenic cycle we recognized collisional stages of uncoupled plates followed by late lower middle pleistocene post collisional stages of coupled continental plates this pleistocene plates re organization of central mediterranean was probably due to the rupture of the apulia ionian slab or to nnw intraplate shortening transmitted from africa

insights on the seismogenic layer thickness from the upper crust structure of the umbria marche apennines central italy 1 we reconstruct the subsurface geology in a region of the northern apennines central italy where a protracted extensional sequence occurred in 1997 1998 with maximum magnitude m 6 0 our study is mainly based on the interpretation of three reprocessed seismic reflection profiles crossing the epicentral area which constrain the subsurface geometry to a depth of about 12 km where most of the shallow seismicity occurs comparing the subsurface setting with accurately determined earthquake locations we find that the seismicity is located entirely within the sedimentary cover and does not penetrate the underlying basement this is explained by considering that the sedimentary cover is rather thick and composed of relatively strong lithologies platform carbonates and evaporites while the upper part of the basement consists of weak phyllites and siliciclastic rocks this weak horizon is also evidenced by the low vp values measured in deep wells of the region its effect is to decouple the sedimentary cover from the crystalline basement where only microseismicity occurs our study indicates that local structure and stratigraphy can significantly influence the distribution of seismicity within the upper crust particularly in complex geological environments such as thrust and fold belts

deep structure of the southern apennines as imaged by active and passive seismic data along the crop 04 crustal reflection seismic profile we combine active and passive seismic data to reconstruct a coherent picture of the deep crust beneath the southern apennines orogen the southern apennines collisional setting is characterized by deep structural complexities which have been here investigated through different seismic data from both active and passive surveys several geological reconstructions have been carried out in the last two decades to interpret the detected substructures but failed to provide a univocal interpretation of the apennine roots at present strong disagreements exist among geologists about the tectonic style of the chain in that portion of the italian peninsula in this study we rst combine ve passive seismic datasets from the overall available literature and we then project them at relative depths on a co located active seismic pro le crop 04 the general aim of the study is to shed light on the southern apennines structure at depths greater than 25 km where through the adopted approach an approximate shape of the lower crust and upper mantle structure can be delineated our results indicate the following 1 during the adriatic slab retreat the crust along the tyrrhenian margin was only marginally thinned moho depth about 28 30 km much less than along the tyrrhenian coast of the northern apennines and calabria where moho depth has been found at 20 25 km 2 the subduction process has locally been stationary for a long time leading to the complete eclogitization of the subducted crust and total regeneration of the tyrrhenian moho 3 subduction fluids underwent a complete migration out of the mantle wedge as testified by the high velocities found in the upper mantle below the moho in the tyrrhenian region observed nowhere else in the apennine subduction setting thematic collection this article is part of the apennines and tyrrhenian system collection available at https www lyellcollection org cc the apennines tyrrhenian system

a geostatistical framework for quantifying the reach scale spatial structure of river morphology 2 application to restored and natural channels abstract alluvial rivers are shaped by interactions between the bed topography the flow field and the movement of sediment to help refine our understanding of these connections between form and process i developed a geostatistical framework for quantifying the reach scale spatial structure of river morphology described in a companion paper in this study i applied this approach to a restored channel and three disparate reaches of a dynamic natural stream repeat topographic surveys of each site were used to examine relationships between channel change and the variability and organization of the topography for the restored river the development of point bars increased overall morphologic diversity primarily because of greater cross sectional asymmetry the three natural reaches experienced a variety of adjustments ranging from 1 gradual bar growth and bank erosion to 2 extensive deposition followed by channel abandonment and 3 chute cutoff and incision of a new channel in both the restored and natural streams geostatistical analysis which involved variogram modeling calculation of integral metrics and inspection of variogram maps provided an effective informative summary of the observed channel changes the use of dimensionless variables accounted for channel size highlighted differences in spatial structure and enabled a comparison among sites the restored reach had not yet achieved the same degree of heterogeneity as the more pristine channels emphasizing variability and spatial pattern via this geostatistical framework could yield insight on form process interactions and help to quantify geomorphic complexity and habitat heterogeneity in the applied context of river restoration

petroleum exploration in italy a review abstract petroleum exploration in italy began in the second half of the 19th century but the first consistent discoveries were only made after world war ii at present the original reserves of the italian petroleum fields amount to about 160 million tons of oil and 720 billion cubic metres of gas domestic production in 1990 was 4 6 million tons of oil and 17 3 billion cubic metres of gas the lithology of the italian sedimentary sequences was controlled by the geodynamic evolution of the western margin of the adria plate the permian triassic continental and shallow water environments pre dating the break up of pangea were followed by subsiding carbonate platforms and basins in the mesozoic tertiary compressive tectonics induced by the subduction of the adria continental margin produced a complex thrust belt bordered by a migrating foredeep filled with clastic sediments most of the oil and a minor part of the gas were generated by middle triassic lower jurassic shaly and carbonate source rocks most of the gas was sourced by pliocene pleistocene clays in the foredeep turbiditic deposits and has a bacterial origin a short review integrated with some actual examples of typical fields cortemaggiore costa molina settala agostino porto garibaldi barbara candela palino rospo vega exemplifies the different plays in the main tectonic domains

under ice noise resulting from thermally induced fracturing of the arctic ice pack theory and a test case application a theory is presented that relates thermally induced fracturing of pack ice to under ice noise level variations it begins with the governing equations for the thermomechanics of pack ice the thermomechanics relates thermally induced strain rates to the stresses within various vertical layers of the floe in addition paradigms are developed which specify the relative quantity of fracturing and stress relief in the floe as the tensile yield strength of the ice is exceeded the thermomechanics is complemented by an acoustic propagation model that relates the number of fracture events at a given time to the acoustic levels at arbitrary frequency and depth below the ice the acoustic theory assumes that each fracture acts as a simple monopole source the fractures are evenly distributed horizontally and the energy of each fracture propagates through the ice and the water column on the basis of the governing equations for elastic waves in a horizontally stratified medium the results indicate that noise episodes resulting from fracturing occurring over the top 40 cm of a 160 cm thick floe will propagate over distances of up to 100 km however noise episodes associated with fracturing occurring in the lower 100 cm of the floe will only propagate over a range of 10 km the thermomechanics and acoustic propagation theories were used to develop a numerical model for predicting under ice noise levels for a given thermal forcing of floes within the arctic ice pack the model was used to simulate stresses in a multiyear floe and under ice noise levels at 500 hz at 305 m below the floe model predicted ice stresses and under ice noise levels compare quite well to observed stresses and noise variations during the fall of 1988 in the eastern arctic ocean the model predicts that most of the thermally induced under ice noise at 500 hz was a result of fracturing occurring between 5 and 30 cm below the ice surface for a 1 6 m thick multiyear floe

active extension in val d agri area southern apennines italy implications for the geometry of the seismogenic belt summary integration of geologic geomorphologic and seismologic data sets is used to reconstruct the recent tectonic evolution and active deformation pattern in the val d agri area located in the seismically active axial sector of the southern apennines italy the western portion of the apennines thrust belt has been affected by pliocene quaternary extension during easterly roll back and crustal delamination of the adriatic slab the bulk of quaternary extension has been accommodated by sw dipping oblique and normal faults which have attained mature morphologic and structural features and nowadays separate mountain ranges from intermontane basins however in the present seismogenic belt coseismic faulting locally occurs on ne dipping structures which might cut the inherited pleistocene landscape in the val d agri basin in spite of the large early middle pleistocene displacement occurred on sw dipping faults bordering its eastern flank our investigations show that the recent basin evolution has been controlled by a ne dipping fault system monti della maddalena fault system mmfs this fault system cuts across the monti della maddalena range west of the agri valley and has not yet created an evident tectonic landscape notwithstanding fault motion since the middle pleistocene might explain geomorphologic and hydrographic anomalies of the agri river and its valley where fault controlled subsidence has captured the river course and produced an aggrading plain within a regional uplift context recent and ongoing motion is documented by fault scarplets in loose deposits 14c ages of palaeosols and the spatial relation with low to moderate instrumental seismicity results from fault kinematic analysis are compatible with fault plane solutions of local and regional seismic events and indicate ne sw oriented extension recognition of the mmfs as a potential seismogenic fault increases the longitudinal extent of the ne dipping morphologically immature seismic sources in the southern apennines and argues against the range bounding fault model for active extension in the region the regional size of the ne dipping seismogenic belt may result from impingement of a mantle wedge beneath the apenninic chain and possibly track the external front of crustal delamination

characteristics of turbulent unidirectional flow over rough beds double averaging perspective with particular focus on sand dunes and gravel beds 1 we address some unsolved methodological issues in modeling of natural rough bed flows by critically examining existing approaches that parameterize rough bed flows these often utilize loosely defined variables here we suggest that double averaging in time and in a volume occupying a thin slab in a plane parallel to the mean bed provides a rigorous straightforward alternative that can aid in the parameterization process we further present two examples two dimensional bed form and gravel bed flows we argue that the double averaging approach based on momentum equations should serve as a better methodological basis for modeling phenomenological developments and parameterizations these equations explicitly include drag terms and form induced momentum fluxes due to spatial heterogeneity of the time averaged flow in the near bed region they also provide a solid basis for better definitions of basic flow variables including the shear stress partitioning into turbulent and form induced momentum fluxes skin friction and pressure form drag we show that for a range of rough bed flows the vertical distribution of the double averaged velocity consists of two distinct regions 1 a linear region below roughness tops and 2 a logarithmic region above them