predicting hydraulic tensile fracture spacing in strata bound systems a model is presented which predicts the spacing of tensile fractures due to fluid pressure increase in a multilayered sedimentary sequence comprising different typical sedimentary deposits such as mudstones siltstones and sandstones during normal burial and tectonic conditions strata will undergo both extensional forces and an increase in fluid pressures this model addresses the effects of the diffuse fluid pressure increase and is useful for engineered applications such as the injection of fluid into a reservoir that may cause an increase of fluid pressure beneath a caprock and for sedimentary sequences during normal digenetic processes of burial and fault activation analytical and numerical elastic stress strain solutions are compared to provide a robust normalised standard relationship for predicting the spacing of fractures key parameters are the local minimum horizontal stress variability of the tensile strengths of the layers of a sedimentary sequence and the thickness of the beds permeability and storage are also shown to affect the fracture spacing the model predicts many of the field observations made regarding strata bound fracture systems and should also prove useful in consideration of the impact of raised reservoir fluid pressures on caprock integrity

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

role of permeability and storage in the initiation and propagation of natural hydraulic fractures 1 joint sets within sedimentary basins are commonly interpreted to have formed by tensile failure in conditions where pore fluid pressure was elevated such tensile fractures are inferred to be a part of the process that relieves high fluid pressure by locally increasing rock permeability in spite of the importance of this feedback mechanism the detailed mechanics of hydraulic fracture genesis remain poorly understood we describe the results of both experimental and numerical studies of hydraulic fracture genesis on the basis of an experimental protocol that combines rock extension with elevated pore fluid pressure such that the hydraulic fracture criterion is met in the sample interior this is achieved by simultaneously dropping both minimum stress and external pore fluid pressure inducing a large fluid pressure drop between the sample interior and its ends poroelastic modeling suggests that the pore fluid pressure is highest close to but not at the sample ends and is locally maintained at levels that meet the hydraulic fracture criterion for up to 50 s application of this experimental protocol to an impure sample of sandstone resulted in the generation of several hydraulic fractures subparallel to the maximum principal stress fracturing did not occur in a drained test on the same sample demonstrating that the elevated pore fluid pressure was critical to fracture formation to better understand the experimental results we explore the role of rock permeability and storage on fracture processes using a numerical model that directly couples a lattice boltzmann model for fluid mechanics with a discrete element model for solid mechanics like the experiment the numerical simulations produced opening mode fractures when operated to replicate the conditions of the experiment fractures preferentially occur in portions of the model inferred to be mechanically weak local fluid pressure gradients strongly influence the state of stress in the solids and thereby fracture growth increasing the model permeability increases fracture propagation rate decreases sample deformation and increases fracture spacing sample deformation increases and fracture spacing decreases with increasing overpressure it appears that bulk forcing of the solid via fluid seepage forces is important in fracture genesis explaining the key roles of permeability and diffusivity in the hydrofracture process

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

rock properties in low porosity low permeability sandstones tight gas sand reservoirs are formally defined by the federal energy regulatory commission ferc as reservoirs with less than 0 1 md permeability although this is a permeability based definition these reservoirs frequently also have very low porosities 15 000 ft oil and gas investor 2005

seismic wave attenuation in carbonates 1 the effect of pore fluids on seismic wave attenuation in carbonate rocks is important for interpreting remote sensing observations of carbonate reservoirs undergoing enhanced oil recovery here we measure the elastic moduli and attenuation in the laboratory for five carbonate samples with 20 to 30 porosity and permeability between 0 03 and 58 1 mdarcy contrary to most observations in sandstones bulk compressibility losses dominate over shear wave losses for dry samples and samples fully saturated with either liquid butane or brine this observation holds for four out of five samples at seismic 10 1000 hz and ultrasonic frequencies 0 8 mhz and reservoir pressures attenuation modeled from the modulus data using cole cole relations agrees in that the bulk losses are greater than the shear losses on average attenuation increases by 250 when brine substitutes a light hydrocarbon in these carbonate rocks for some of our samples attenuation is frequency dependent but in the typical exploration frequency range 10 100 hz attenuation is practically constant for the measured samples

elastic piezosensitivity of porous and fractured rocks understanding the stress dependencies of seismic velocities is important for interpreting a variety of seismic data ranging from amplitude versus offset avo and velocity analysis to overpressure prediction and 4d seismic monitoring of reservoirs sometimes rather complex forms of these dependencies based on specific models of porous space geometry are used for example spherical contacts models duffy and mindlin 1957 merkel et al 2001 duffy merkel 2001 and crack contacts models gangi and carlson 1996 carcione and tinivella 2001 have been used in different studies gangi96 however usually the pore pressure velocity dependence along with the velocity dependence on the confining pressure are phenomenologically described by the following simple relationship zimmerman et al 1986 eberhart phillips et al 1989 freund 1992 jones 1992 prasad and manghnani 1997 khaksar et al 1999 carcione and tinivella 2001 kirstetter and macbeth 2001

a study of caprock hydromechanical changes associated with co2 injection into a brine formation a numerical study of hydromechanical changes during a deep underground injection of supercritical co2 in a hypothetical brine aquifer caprock system is conducted the injection process is simulated using a newly developed computer model for multi phase analysis of co2 and brine water flow coupled with heat transfer and rock deformations in this modeling co2 is injected at a constant rate over a 10 year period at a depth of 1 300 1 500 m the injection zone is overlain by a 100 m thick caprock located at 1 200 1 300 m which in one of the studied cases is intersected by a vertical fault the hydraulic mechanical as well as hydromechanical responses caused by the injection are studied this includes the spread of the co2 plume effective stress changes ground surface uplift stress induced permeability changes and mechanical failure analysis the analysis shows that most hydromechanical changes are induced in the lower part of the caprock near its contact with the injection zone whereas the sealing mechanism of the upper part may remain intact despite an injection pressure close to the lithostratic stress value

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

a new laboratory technique for determining the compressional wave properties of marine sediments at sonic frequencies and in situ pressures we describe a new laboratory technique for measuring the compressional wave velocity and attenuation of jacketed samples of unconsolidated marine sediments within the acoustic sonic frequency range 1 10 khz and at elevated differential confining pore pressures up to 2 413 mpa 350 psi the method is particularly well suited to attenuation studies because the large sample length up to 0 6 m long diameter 0 069 m is equivalent to about one wavelength thus giving representative bulk values for heterogeneous samples placing a sediment sample in a water filled thick walled stainless steel pulse tube causes the spectrum of a broadband acoustic pulse to be modified into a decaying series of maxima and minima from which the stoneley and compressional wave velocity and attenuation of the sample can be determined experiments show that pvc and copper jackets have a negligible effect on the measured values of sediment velocity and attenuation which are accurate to better than 1 5 for velocity and up to 5 for attenuation pulse tube velocity and attenuation values for sand and silty clay samples agree well with published data for similar sediments adjusted for pressure temperature salinity and frequency using standard equations attenuation in sand decreases with pressure to small values below q 1 0 01 q greater than 100 for differential pressures over 1 5 mpa equivalent to sub seafloor depths of about 150 m by contrast attenuation in silty clay shows little pressure dependence and intermediate q 1 values between 0 0206 0 0235 q 49 43 the attenuation results fill a notable gap in the grain size range of published data sets overall we show that the pulse tube method gives reliable acoustic velocity and attenuation results for typical marine sediments

acoustic measures of partial gas saturation in tight sandstones the acoustic properties of tight sandstones are very sensitive to partial gas water saturation measurements at 5 khz show that compressional velocity drops sharply with undersaturation extensional and shear losses at 5 khz are large in both fully and partially saturated sands the shear loss qs 1 declines linearly with increasing gas content the extensional loss qe 1 peaks at 0 80 water saturation q 1 is frequency dependent the attenuation is well explained by hydrodynamic relaxation in the grain contacts the measurements indicate velocity dispersions consistent with this mechanism ultrasonic velocities at 500 khz are roughly 10 25 higher than acoustic velocities at 5 khz the ultrasonic velocities exhibit a weak dependence on saturation frame moduli are unrelaxed at these frequencies

an overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability fluid properties and saturation however in order to use attenuation as an attribute to extract information on rock fluid properties from seismic data experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies an appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method but technical challenges kept this technique from being widely used there is a need for the standardization of devices employing this method and a comparison of existing setups is a step towards it here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency dependent attenuation in fluid saturated and or dry reservoir rocks under small strains 10 8 10 5 we list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one we also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far

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

pressure and fluid effect on frequency dependent elastic moduli in fully saturated tight sandstone we developed a system to explore the effects of pressure and fluid viscosity on the dispersion and attenuation of fully saturated tight sandstones especially at seismic frequencies calibration of the new system revealed that the system can operate reliably at frequencies of 2 200 106 hz tight sandstone with a crack pore microstructure was tested under nitrogen gas dry brine and glycerin saturation a frequency dependent effect was not found for the dry case however apparent dispersion and attenuation for the undrained unrelaxed transition was clearly observed for sample under brine or glycerin saturation the magnitude of which was largely suppressed by increasing effective pressure the measurement results illustrated that increasing the fluid viscosity or the effective pressure will shift the dispersion curve to the lower frequency range a simple squirt flow model with dual porosity scheme was used to compare with the measurement results although the estimated values deviated slightly from the data the trend fitted the saturated data relatively well especially at low effective pressures therefore considering the crack pore microstructure of the tight sandstone dispersion and attenuation are induced predominantly by the squirt flow stiffening effect from cracks to pores

an experimental investigation of factors influencing compressional and shear wave velocities and attenuations in tight gas sandstones results are presented for compressional and shear velocities and attenuations in fully brine saturated tight gas cores with porosities from 3 to 11 9 percent and clay contents from 1 to 38 percent the influence of porosity clay content frequency and stress on velocities and attenuations were examined using the amplitude spectra of p and s waves in the frequency domain attenuations of samples were obtained using the spectral ratio method for a few selected samples the attenuations were also measured using the length correlation method and these results were compared with the spectral ratio results in tight gas sandstones the attenuations obtained were 2 to 5 times greater than the attenuation obtained for berea sandstone in general the presence of clay softens the rock grain contacts causing smaller values of compressional vp and shear vs velocities as the clay content increases however the vp vs ratio was found to increase with clay content compressional and shear wave amplitude spectra

3d porosity and mineralogy characterization in tight gas sandstones tight gas reservoirs exhibit storage and flow characteristics that are intimately tied to depositional and diagenetic processes as a result exploitation of these resources requires a comprehensive reservoir description and characterization program to identify properties which control production in particular tight gas reservoirs have significant primary and secondary porosity and pore connectivity dominated by clays and slot like pores this makes them particularly susceptible to the effects of overburden stress and variable water saturation this paper describes an integrated approach to describe a tight gas sandstone at the pore scale in 3d in particular the primary and secondary porosity of a tight gas sandstone are identified and quantified in three dimensions using 3d x ray micro ct imaging and visualization of core material at the pore scale 3d images allow one to map in detail the pore and grain structure and interconnectivity of primary and secondary porosity once the tomographic images ar

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

a new seismic wave attenuation module to experimentally measure low frequency attenuation in extensional mode abstract a seismic wave attenuation module is developed to experimentally measure the attenuation in extensional mode qe 1 and the young s modulus of copper jacketed 60 mm long and 25 4 mm in diameter samples in a gas medium paterson rig the new module is suitable for natural rock samples and was tested under confining pressure up to 50 mpa and room temperature the module is designed to operate at a strain 10 6 for which rocks behave linearly to calculate attenuation both the applied force and the bulk shortening of the sample are measured employing linear variable differential transformers this technique allows measuring samples with a high degree of heterogeneity attenuation at low seismic frequencies 10 2 102 hz is obtained for rocks at dry and various saturation conditions we present a series of measurements on berea sandstone in a room dry condition and saturated with different fluids water and glycerine solutions with viscosities of 10 cp and 22 cp respectively at a confining pressure of 10 mpa and with a pore pressure of 1 mpa the accuracy of the attenuation data expressed as a phase shift is 0 0019 rad

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

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

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

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

microfracturing in the upper triassic sichuan basin tight gas sandstones tectonic overpressure and diagenetic origins the western sichuan basin located at the front of the longmen mountain in the western sichuan province of china is a foreland basin formed in the late triassic the upper triassic xujiahe formation in the basin is an ultralow permeability and low porosity tight gas sandstone reservoir microfractures such as intragranular microfractures grain edge microfractures and transgranular microfractures are abundant in the tight sandstones microfractures improve storage and permeability and impact distribution of natural gas microfractures reflect tectonic overpressure and diagenetic origins using quartz and calcite fluid inclusions and burial history tectonic microfractures were determined to be formed at the end of the triassic the end of the cretaceous and the end of the neogene early pleistocene microfractures related to overpressure being tension microfractures are commonly filled with bitumen and were formed at the middle to late cretaceous when the maximum pressure coefficients were 1 6 to 2 1 in the middle to late neogene the pressure coefficient was reduced to less than 1 3 because of fault activity and tectonic uplift in the southwestern sichuan basin and these tension microfractures closed and were filled with calcite the transition of stress state from compression to tension by overpressure is the reason that tension microfractures were formed in the compression setting diagenetic fractures were formed at the end of the late triassic to jurassic under intense compaction grain crushing crackle fractures in quartz and cleavage fractures in feldspar formed intragranular microfractures some transgranular microfractures caused by diagenesis are along the bedding plane and parallel to the directional mineral grains

laboratory based seismic attenuation in fontainebleau sandstone evidence of squirt flow at seismic frequencies 1 100 hz we studied attenuation in the laboratory using the forced oscillation method we adopted the longitudinal mode of oscillation which yields the young s modulus and the corresponding attenuation here defined as the inverse quality factor a fontainebleau sandstone with a porosity of 8 and a permeability of 12 md was saturated with different fluids and investigated at the confining pressures of 5 10 and 15 mpa at all the measured confining pressures while attenuation was zero for the dry sample for partial and full water saturation it gradually increased from nearly zero to 0 02 with increasing frequency the sample was then fully saturated with glycerin water mixtures of varying viscosities up to that of glycerin 8 92 485 and 1414 cp at the confining pressure of 5 mpa a bell shaped attenuation curve peaking at 6 hz with a magnitude of 0 11 was observed when the sample was fully saturated with glycerin 1414 cp a decrease in viscosity of the saturating fluid shifted the attenuation curve to higher frequencies and an increase in confining pressure caused a decrease in the overall magnitude of attenuation the data obtained for glycerin were compared to a simple squirt flow model with sufficient agreement implying that squirt flow is the dominant mechanism responsible for the observed attenuation

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

dispersion of elastic moduli in a porous cracked rock theoretical predictions for squirt flow abstract crustal rocks contain variable amount of both cracks and equant pores depending on tectonic and thermal stresses but also on their geological origin crack damage and porosity change result in effects on elastic waves velocities when rocks are fluid saturated dispersion of the p and s waves should be taken into account this paper deals with frequency dispersion of elastic moduli in a fluid saturated porous and cracked rock with the assumption that squirt flow is the dominant process we develop a theoretical approach to calculate both high hf and low lf frequency bulk and shear moduli the hf moduli are derived from a new effective medium model called cpem with an isotropic distribution of pores or cracks with idealized geometry respectively spheres and ellipsoids lf moduli are obtained by taking hf dry moduli from the cpem and substituting into gassmann s equations in the case of a porosity only supported by equant pores the calculated dispersion in elastic moduli is equal to zero in the case of a crack porosity no bulk dispersion is predicted but a shear dispersion appears finally in the general case of a mixed porosity pores and cracks dispersion in bulk and in shear is predicted our results show that the maximum dispersion is predicted for a mixture of pores and spheroidal cracks with a very small aspect ratio 10 3 our theoretical predictions are compared to experimental data obtained during hydrostatic experiment performed on a basaltic rock and a good agreement is observed we also used our theoretical model to predict elastic waves velocities and vp vs ratio dispersion we show that the p waves dispersion can reach almost 20 and the vp vs dispersion a maximum value of 9 for a crack porosity of about 1 since laboratory data are ultrasonic measurements and field data are obtained at much lower frequencies these results are useful for geophysicists to interpret seismic data in terms of fluid and rock interactions

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