reservoir structure and wastewater induced seismicity at the val d agri oilfield italy shown by three dimensional vp and vp vs local earthquake tomography wastewater injection into a high rate well in the val d agri oilfield the largest in onshore europe has induced swarm microseismicity since the initiation of disposal in 2006 to investigate the reservoir structure and to track seismicity we performed a high spatial resolution local earthquake tomography using 1281 natural and induced earthquakes recorded by local networks the properties of the carbonate reservoir rock fracturing pore fluid pressure and inherited faults control the occurrence and spatiotemporal distribution of seismicity a low vp high vp vs region under the well represents a fluid saturated fault zone ruptured by induced seismicity high vp high vp vs bumps match reservoir culminations indicating saturated liquid bearing zones whereas a very low vp low vp vs anomaly might represent a strongly fractured and depleted zone characterized by significant fluid withdrawal the comprehensive picture of the injection linked seismicity obtained by integrating reservoir scale tomography high precision earthquake locations geophysical and injection data suggests that the driving mechanism is the channelling of pore pressure perturbations through a high permeable fault damage zone within the reservoir the damage zone surrounds a pliocene reverse fault optimally oriented in the current extensional stress field the ruptured damage zone measures 2 km along strike 3 km along dip and is confined between low permeability ductile formations injection pressure is the primary parameter controlling seismicity rate our study underlines that local earthquake tomography also using wastewater induced seismicity can give useful insights into the physical mechanism leading to these earthquakes

joint inversions of seismic and geodynamic data for models of three dimensional mantle heterogeneity the seismic models of three dimensional 3 d mantle heterogeneity may be interpreted in terms of the density perturbations which drive mantle flow and thus provide important predictions of flow related observables such as the nonhydrostatic geoid the current models of global scale shear velocity heterogeneity provide reasonably good fits to the long wavelength nonhydrostatic geoid data 60 70 variance reductions but rather poor fits to the corresponding free air gravity anomalies 30 40 variance reductions this major difference is due to two factors 1 the very different amplitude spectrum of the gravity anomalies which is nearly flat for degrees l 3 the largest mismatch between the pattern of predicted and observed gravity anomalies is in the southern hemisphere this observation suggests that one reason for the poor overall match between the two fields may be that the global seismic data are not resolving sufficiently well the heterogeneity in the southern hemisphere portion of the deep mantle in contrast the gravity data provide accurate and geographically uniform constraints on the vertically integrated heterogeneity in the mantle we therefore perform a series of experiments in which we simultaneously invert a large set of seismic data which includes long period waveforms ss s and scs s differential travel times and normal mode structure coefficients and the long wavelength gravity anomaly data we thus determine whether it is possible to derive new 3 d heterogeneity models which satisfy both data sets the gravity anomaly data are interpreted in the context of spherically symmetric viscous flow models of the mantle in these inversion experiments we test several radial viscosity and ln ln profiles and thereby assess their plausibility the joint seismic geodynamic inversions reveal that it is indeed possible to greatly improve the fit to the free air gravity anomalies with variance reductions of 80 90 readily accessible while preserving the fit to the seismic data this improvement is achieved with some adjustment to the heterogeneity in the depth range 1500 2500 km where the seismic data constraints appear to be weakest the joint inversions also reveal new structures in the southern hemisphere portion of the lower mantle which apparently are not resolved by the seismic data alone

a detailed analysis of wastewater induced seismicity in the val d agri oil field italy the val d agri basin in the apennines seismic belt hosts the largest oil field in onshore europe high quality recordings from a temporary dense network unravel a swarm of 111 small magnitude events ml 1 8 occurred in june 2006 during the first stage of wastewater injection into a high rate well high precision relative locations define a preexisting blind fault located 1 km below the well inside fractured and saturated carbonates where wastewater is reinjected seismicity begins 3 h after the initiation of injection the seismicity rate strictly correlates with injection curves and temporal variations of elastic and anisotropic parameters seismicity is induced by rapid communication of pore pressure perturbations along a high permeability fault zone favorably oriented with respect to the local extensional stress field our accurate 3 d locations of 219 events ml 2 2 detected by the local operator network after june 2006 concentrate on the preexisting fault measuring 5 km along dip over the following 7 5 years the seismicity rate correlates with short term increases in injection pressure

influence of pore pressure on the event size distribution of induced earthquakes 1 during an enhanced geothermal system egs experiment fluid is injected at high pressure into crystalline rock to enhance its permeability and thus create a reservoir from which geothermal heat can be extracted the fracturing of the basement caused by these high pore pressures is associated with microseismicity however the relationship between the magnitudes of these induced seismic events and the applied fluid injection rates and thus pore pressure is unknown here we show how pore pressure can be linked to the seismic frequency magnitude distribution described by its slope theb value we evaluate the dataset of an egs in basel switzerland and compare the observed event size distribution with the outcome of a minimalistic model of pore pressure evolution that relates event sizes to the differential stress d we observe that the decrease of b values with increasing distance of the injection point is likely caused by a decrease in pore pressure this leads to an increase of the probability of a large magnitude event with distance and time

variations of attenuation and vp vs ratio in the vicinity of wastewater injection a case study of costa molina 2 well high agri valley italy by analyzing seismicity induced by the injection of wastewater into the costa molina 2 well we characterized the attenuation in the area attenuation quality factors qp and qs were calculated using peak frequency method which is suitable for small magnitude earthquakes registered in the region anomalously high attenuation with values of effective qp 48 and qp qs ratio below 1 in the vicinity of the injection well was found in comparison with qp 60 for the rest of the region furthermore vp vs ratio was also found high in the close vicinity of the injection well we discuss how sedimentary rocks possibly change their geomechanical properties due to salt water injection and show that observed changes of attenuation increase and vp vs ratio increase are consistent with the geomechanical models and experiments our findings indicate that the observed anomaly in the vicinity of the costa molina 2 well is due to i changes of the properties of the rock mass affected by injection ii 3d structure in

reconstruction of continental margin architecture deformed by the contraction of the lagonegro basin southern apennines italy thrust propagation through previously rifted continental margins may result in fold and thrust belts whose structure is strongly controlled by the inherited basin architecture as it occurs in southern italy the lagonegro units of the southern apennines comprise a deformed pelagic basin succession showing variable stratigraphic characteristics mainly lateral variations in both facies and thickness interpreted to be due to a complex basin topography related to a triassic rifting event in contrast to previous studies cross section balancing and restoration indicate that the lagonegro units exposed in the high agri valley area suffered relatively limited internal shortening 8 km i e 35 early deformation of these rocks later incorporated into a large displacement thrust sheet was dominated by folding around present day roughly north south trending axes the attainment of a regional decollement level was favoured by an early mild inversion of the basin producing a roughly similar structural elevation of both hanging wall and footwall successions to mesozoic faults most of the contractional deformation was accommodated by buckling of the mesozoic syn rift strata between synsedimentary faults which represented major mechanical interfaces early strain localization in the lagonegro basin ahead of the active thrust front was most probably mechanically controlled by a faulted crustal segment which originally lay within the continental margin between two massive carbonate platforms

fluid induced seismicity guided by a continental fault injection experiment of 2004 2005 at the german deep drilling site ktb 1 recent hydraulic experiments at the ktb site have shown that seismicity induced by long term fluid injection directly into a continental crustal fault remains guided by this fault the seismicity is triggered by pressure perturbations as low as 0 01 1 bars at the hypocenters a combination of sequential one year fluid extraction 2002 2003 and one year fluid injection 2004 2005 experiments has shown that only positive pore pressure perturbation i e injections was able to induce the seismicity moreover the onset of seismicity roughly coincides with the time of compensation of the extracted fluid volume by the following injection this confirms that the pressure diffusion is a dominant mechanism of seismicity triggering by fluid injections the probed fault shows a significant anisotropy and non linearity of its hydraulic behaviour its hydraulic diffusivity is up to one order of magnitude larger than that of surrounding rocks

temporal variation of seismic velocity and anisotropy before the 2009 mw 6 3 l aquila earthquake italy we describe a set of seismological observations of the foreshock sequence preceding the 6 april 2009 m w 6 3 l9aquila earthquake the dense configuration of the seismic network in the epicenter area and the occurrence of a long foreshock sequence provide the opportunity for a detailed reconstruction of the preparatory phase of the main shock approaching the earthquake we observed clear variations in the seismic wave propagation properties the elastic properties of rocks in the fault region underwent a sharp change about a week before the earthquake from our observations we infer that a complex sequence of dilatancy diffusion processes takes place and that fluids play a key role in the fault failure process

site and building characterization of the orvieto cathedral umbria central italy by electrical resistivity tomography and single station ambient vibration measurements abstract a multidisciplinary approach based on the integration of geological and in situ geophysical techniques was applied to investigate the orvieto cathedral umbria central italy and the underlying subsurface notwithstanding this cathedral has successfully survived different earthquakes occurred in the region it shows some signs of damage that arise uncertainties about its safety under future seismic events in order to investigate its unknown foundation geometry to reconstruct the geological setting and to characterize from a static and dynamic point of view the site structure system geological investigations together with electrical resistivity tomography and horizontal to vertical spectral ratio analysis of single station ambient vibration recordings were carried out the exploitation of these two different geophysical techniques allowed us 1 to delineate the unknown foundation geometry of the orvieto cathedral 2 to estimate the main resonance frequencies of the cathedral and 3 of the orvieto site and 4 to retrieve information about its deep subsurface engineering geological structure

thermal expansion measurements at very high pressure systematics and a case for a chemically homogeneous mantle new data on thermal expansivity of iron to over 400 kbar in laser and electrically heated diamond anvil cells and on mgo and forsterite from spectroscopic data to over 200 kbar and previously measured adiabats boehler 1982 imply that at high pressure may be described by a constant value of 1n 1nv t 5 5 0 5 this behavior is supported by previous measurements at lower pressures on a large variety of materials densities of magnesio wustite and silicate perovskite in a pyrolitic ratio calculated at lower mantle conditions using a finite strain equation and at high pressures using the above systematics match those in prem through the entire lower mantle making a strong case for a uniform mantle

finite element modelling of stress field perturbations and interseismic crustal deformation in the val d agri region southern apennines italy abstract the val d agri area provides the opportunity to analyse active structures in a seismic region for which a large amount of subsurface data is available this area which was struck in 1857 by one of the most destructive earthquakes in italy mw 7 03 represents a unique natural laboratory to gain new insights into geometry modes and rates of faulting controlling crustal deformation in an actively extending orogen in this study a crustal geological section through the southern apennines is discretized into a finite element model fem we present a 2d elastoplastic fem that reproduces stress perturbations and strain field around the val d agri active fault system the influence of fault strand activity on interseismic crustal deformation is tested by a series of computer models whose predictions are compared with the horizontal velocity components of continuous gps sites in the region and with stress directions and geological data the best fit with available geological and geophysical constraints is obtained with a 300 km long 29 km deep model formed by a multilayer including three components having different rheological characteristics and including several shallow locked fault segments which branch into a freely slipping major basement fault at depth finite element modelling provides new insights into the controversial and widely debated active tectonic setting of the study area pointing out the fundamental role played by a structural reactivation process involving inherited long lived mature fault systems at depth our fem reconciling apparently contrasting geological and geophysical constraints from the study area points to maximum stress build up and strain accumulation at a depth of 15 5 km such a depth range is suggested as the most likely one for the nucleation of large events such as the 1857 val d agri earthquake

thermal inertia and reversing buoyancy in flow in porous media 1 the displacement of fluids through porous rocks is fundamental for the recharge of geothermal and hydrocarbon reservoirs grant et al 1982 lake 1989 for contaminant dispersal through the groundwater bear 1972 and in controlling mineral reactions in permeable rocks phillips 1991 in many cases the buoyancy force associated with density differences between the formation fluid and the displacing fluid controls the rate and pattern of flow through the permeable rock phillips 1991 barenblatt 1996 turcotte and schubert 2002 here using new laboratory experiments we establish that a striking range of different flow patterns may develop depending on whether this density contrast is associated with differences in temperature and or composition between the two fluids owing to the effects of thermal inertia in a porous rock thermal fronts lag behind compositional fronts woods and fitzgerald 1993 turcotte and schubert 2002 so that two zones of different density develop in the region flooded with injected fluid this can lead to increasing decreasing or even reversing buoyancy in the injected liquid in the latter case it may then form a double flood front spreading along both the upper and lower boundary of the rock recognition of these different flow regimes is key for predicting sweep efficiency and dispersal patterns in natural and engineered flows and offers new opportunities for the enhanced recovery of natural resources in porous rocks

aspherical earth structure from fundamental spheroidal mode data free oscillation data reveal heterogeneity in the earth s mantle whose geographical pattern is dominated by spherical harmonics of angular degree two and correlates well with the hydrostatically referenced geoid the heterogeneity can be modelled as localized in the transition zone 420 670 km depth and may be related to a large scale component of mantle convection

is there a link between mineralogy petrophysics and the hydraulic and seismic behaviors of the soultz sous forets granite during stimulation a review and reinterpretation of petro hydromechanical data toward a better understanding of induced seismicity and fluid flow

on the scale of mantle heterogeneity abstract a data set comprising 3313 residuals measured from digital records of 429 earthquakes is analyzed for the heterogeneity of the earth s mantle the smoothed ss residuals reveal a large pattern of heterogeneity and agree well with the major tectonic features on the earth s surface and the residual patterns predicted by upper mantle and whole mantle models the spectrum of ss residuals indicates that the heterogeneity in the earth s mantle which probably reflects the patterns of mantle convection is dominated by long wavelength features our analysis of the power of ss residuals as a function of harmonic degree shows a distinct difference in the rate of decrease of the power below and above degree 8 the rate is first slower than l 1 and then it exceeds l 2 this is also true for ss residuals predicted for model sh 425 2 and love wave phase velocities at 100 s measured by other researchers this indicates that there is a preference for features with dimensions larger than 2500 3500 km we find that the power spectrum of the velocity anomalies associated with the subducted slabs is two orders of magnitude lower for 1 l 8 than that of velocity anomalies obtained by inversion of waveform data for the ocean basins correlation of the ss residuals with the square root of age of the oceanic lithosphere is highly significant however the age correlation predicts only 10 of the variance this means that the thermal signature of the spreading center represents only a small fraction of the thermal anomalies introduced into the upper mantle by convection

whole mantle p wave travel time tomography abstract a method of tomographic inversion to obtain three dimensional velocity perturbations in the earth s whole mantle has been developed and applied to more than two million p wave arrival time data reported by international seismology center isc the model is parameterized with 32 768 blocks the divisions in latitude longitude and radius are 32 64 and 16 respectively horizontal cell size is 5 6 5 6 the layer thicknesses vary with depth 29 km just below the surface and 334 km just above the core mantle boundary starting from a spherically symmetric earth model we obtained a three dimensional model using the following iterative procedures first we relocated all the events second we backprojected the residual into the whole mantle third we refined the spherically symmetric earth model the solutions have been converged in five iterations we adopted the following techniques in the backprojection procedure the first order smoothness was introduced as a damping which makes the solution independent of the starting model and its apparent fluctuation minimal the basic equations for delay times and smoothness are solved using the conjugate gradient method an iterative method which guarantees the convergence of solution into the exact least squares solution the weight on the smoothness i e the damping factor was objectively determined by a simplified cross validation technique the final solution was obtained as an average of the ten solutions each of which was derived from one tenth of the total data set the reliability of the solution is examined in two ways 1 mapping the resolution given by the reconstruction of checkerboard patterns and 2 mapping the variance given from the gaussian noise input this is the first result which delineates the whole mantle structure with its reliability mapping the longest wavelength anomalies of the lower mantle are similar to those of previous studies by dziewonski 1984 and hager and clayton 1989 however the shorter wavelength patterns have many discrepancies the fast anomalies of the uppermost mantle beneath the shield and the slow anomalies beneath the active tectonic regions are clearly seen we also revealed the l 2 pattern at the transition zone reported by the previous surface wave and free oscillation studies the most striking feature is that of the fast anomalies lying along the extension of the large subducting plate up to depths of about 1000 km or more the resolving powers in these regions are generally good

induced seismicity associated with fluid injection into a deep well in youngstown ohio 1 over 109 small earthquakes mw 0 4 3 9 were detected during january 2011 to february 2012 in the youngstown ohio area where there were no known earthquakes in the past these shocks were close to a deep fluid injection well the 14 month seismicity included six felt earthquakes and culminated with a mw 3 9 shock on 31 december 2011 among the 109 shocks 12 events greater than mw 1 8 were detected by regional network and accurately relocated whereas 97 small earthquakes 0 4 mw 1 8 were detected by the waveform correlation detector accurately located earthquakes were along a subsurface fault trending ene wsw consistent with the focal mechanism of the main shock and occurred at depths 3 5 4 0 km in the precambrian basement we conclude that the recent earthquakes in youngstown ohio were induced by the fluid injection at a deep injection well due to increased pore pressure along the preexisting subsurface faults located close to the wellbore we found that the seismicity initiated at the eastern end of the subsurface fault close to the injection point and migrated toward the west away from the wellbore indicating that the expanding high fluid pressure front increased the pore pressure along its path and progressively triggered the earthquakes we observe that several periods of quiescence of seismicity follow the minima in injection volumes and pressure which may indicate that the earthquakes were directly caused by the pressure buildup and stopped when pressure dropped

discharge estimation of submarine springs in the dead sea based on velocity or density measurements in proximity to the water surface the dead sea is a closed lake the water level of which is lowering at an alarming rate of about 1 m year factors difficult to determine in its water balance are evaporation and groundwater inflow some of which emanate as submarine groundwater discharge a vertical buoyant jet generated by the difference in densities between the groundwater and the dead sea brine forms at submarine spring outlets to characterize this flow field and to determine its volumetric discharge a system was developed to measure the velocity and density of the ascending submarine groundwater across the center of the stream along several horizontal sections and equidistant depths while divers sampled the spring this was also undertaken on an artificial submarine spring with a known discharge to determine the quality of the measurements and the accuracy of the method the underwater widening of the flow is linear and independent of the volumetric spring discharge the temperature of the dead sea brine at lower layers primarily determines the temperature of the surface of the upwelling produced above the jet flow as the origin of the main mass of water in the submarine jet flow is dead sea brine based on the measurements a model is presented to evaluate the distribution of velocity and solute density in the flow field of an emanating buoyant jet this model allows the calculation of the volumetric submarine discharge merely requiring either the maximum flow velocity or the minimal density at a given depth

temporal relationship between injection rates and induced seismicity normalized cross correlation of effective functions was originally developed to differentiate induced and natural seismicity we apply this methodology to data sets acquired during hydraulic stimulation of shale gas to study temporal relationship between seismicity and the injection delays of seismicity induced by hydraulic fracturing are compared with delays of seismicity related to changes of the water level in a dam a new observation is made we show that seismicity induced by hydraulic fracturing and measured by the normalized cross correlation can have very positive to even short negative delay after the injection we explain this observation by rapid decline of induced seismicity after decrease of injection on the contrary we show that the seismicity triggered by water impounding in a dam is characterized by longer delays due to much greater distance between lake and the induced seismicity we show how it is possible to measure the delay by the cross correlation methodology despite periodicity of the signals

aseismic motions drive a sparse seismicity during fluid injections into a fractured zone in a carbonate reservoir author s duboeuf l de barros l cappa f guglielmi y deschamps a seguy s abstract 2017 american geophysical union all rights reserved an increase in fluid pressure in faults can trigger seismicity and large aseismic motions understanding how fluid and faults interact is an essential goal for seismic hazard and reservoir monitoring but this key relation remains unclear we developed an in situ experiment of fluid injections at a 10 meter scale water was injected at high pressure in different geological structures inside a fault damaged zone in limestone at 280 m depth in the low noise underground laboratory france induced seismicity as well as strains pressure and flow rate was continuously monitored during the injections although nonreversible deformations related to fracture reactivations were observed for all injections only a few tests generated seismicity events are characterized by a 0 5 to 4 khz content and a small magnitude approximately 3 5 they are located within 1 5 m accuracy between 1 and 12 m from the injections comparing strain measurements and seismicity shows that more than 96 of the deformation is aseismic the seismic moment is also small compared to the one expected from the injected volume moreover a dual seismic behavior is observed as 1 the spatiotemporal distribution of some cluster of events is clearly independent from the fluid diffusion 2 while a diffusion type pattern can be observed for some others clusters the seismicity might therefore appear as an indirect effect to the fluid pressure driven by aseismic motion and related stress perturbation transferred through failure

turbulent 3 d thermal convection in an infinite prandtl number volumetrically heated fluid implications for mantle dynamics summary the structure and time dependence of 3 d thermal convection in a volumetrically heated infinite prandtl number fluid is examined for high values of the rayleigh number the methods employed allow the numerical experiments to proceed for long enough times to derive good estimates of mean and fluctuating parts of the structure an iterative multirigid method to solve for the buoyant incompressible viscous flow at each time step of the energy equation is a novel aspect of the methodology a simple explicit time step of the energy equation is utilized that vectorizes well on serial computers and which is ideally suited to massively parallel computers numerical experiments were carried out for rayleigh numbers from 3 106 to 3 107 in a cartesian region with a prescribed temperature at the top boundary and an adiabatic bottom boundary over this complete range of rayleigh number the flow structure consists dominantly of cold nearly axisymmetric plumes that migrate horizontally sweeping off the cold thermal boundary layer that forms at the top of the convecting fluid plumes disappear by coalescing with other plumes new plumes are created by thermal boundary layer instability sheet plumes form only occasionally and do not penetrate to significant depths in the fluid plumes have sizes comparable to the thickness of the thermal boundary layer and an average spacing comparable to the fluid depth no persistent large scale motion in the fluid can be identified its absence may reflect the large subadiabatic stratification that develops beneath the thermal boundary layer as cold plumes penetrate to the bottom boundary without thermally equilibrating with surrounding fluid we consider the possible implications for convection in planetary mantles and for the existence of plate tectonics

a simple model of the 1982 83 californian el nino steric height steric height anomaly sea level and sea level anomaly show that the 1940 41 and the 1982 83 californian el nino events were resonant responses of the california current to the expansion and intensification of the aleutian low and decrease in strength of the north pacific high in both cases the subsurface anomalies were dynamically produced by onshore transport of subarctic water and a downward tilt of the inshore thermocline sea surface temperature anomalies however resulted from thermodynamic as well as dynamic processes most previous californian el nino or anti el nino events probably were resonant or anti resonant responses of the seasonal cycle of the california current to anomalous large scale atmospheric forcing

evidence of low magnitude continued reservoir induced seismicity associated with the pertusillo artificial lake southern italy the most common observations of reservoir induced seismicity ris by filling artificial lakes are generally associated with the initial impoundment of the lake or the lake level increase above a previous maximum rarely ris persists for many years without a decrease in frequency or magnitude if this occurs it is called protracted or continued seismicity pertusillo artificial lake in high agri valley southern italy is a small reservoir with a water column that fluctuates yearly by about 10 15 m on average corresponding to a pressure perturbation at the bottom of the lake of 0 10 0 15 mpa although the reservoir was filled in 1963 the microearthquake activity still occurring around the lake allows the categorization of such ris as continued seismicity we collected all microearthquakes m l 2 7 recorded near the reservoir by two different seismic networks from january 2005 to june 2012 and analyzed their frequency magnitude distribution which showed a b value b 1 40 much higher than that expected for the investigated area even though the spatial seismicity pattern shows two distinct clusters to the northeast and southwest of the lake we found that only the southwest seismicity is significantly correlated with the water level the findings suggest that the physical driving mechanism is the 1d pore fluid pressure diffusion along the northeast southwest fault zones connecting the reservoir to the southern termination of the monti della maddalena fault system with an average hydraulic diffusivity of 7 8 m2 s online material figures of magnitude comparisons between catalogs temporal occurrence of events rainfall versus number of earthquakes and number of events versus water level and animated 3d views of seismicity and reservoir

mantle phase transitions and layered chaotic convection we report preliminary results from a sequence of very high resolution simulations of the mantle convection process based upon an axisymmetric anelastically compressible spherical model with both olivine spinel and spinel post spinel phase transitions our analyses strongly suggest that at earth like rayleigh numbers near 107 the circulation may be quite strongly layered although a very long timescale transient exists that is characterized by brief excursions into the whole mantle state we suggest the use of a new diagnostic tool that may be employed to determine whether or not the layered state is characteristic of the present day earth

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

fluid injection induced seismicity reveals a ne dipping fault in the southeastern sector of the high agri valley southern italy on 2 june 2006 the wastewater produced during the oil and gas field exploitation in high agri valley southern italy started to be managed by disposal through pumping the fluids back into the subsurface at the costa molina 2 cm2 injection well located in the southeastern sector of the valley the onset of microearthquakes ml 2 after 4 days at about 1 3 km sw of cm2 well suggests fluid injection induced seismicity by the diffusion of pore pressure moreover the space time evolution of 196 high resolution relocated events reveals a previously unmapped ne dipping fault we investigate the physical processes related to the fluid injection induced seismicity and delineate the previously unmapped fault by jointly analyzing seismicity data geological observations fluid injection data the stratigraphic log of the cm2 well and the electrical resistivity tomography survey carried out in the study area

orogens and slabs vs their direction of subduction abstract subduction zones appear primarily controlled by the polarity of their direction i e w directed or e to nne directed probably due to the westward drift of the lithosphere relative to the asthenosphere the decollement planes behave differently in the two end members in the w directed subduction zone the decollement of the plate to the east is warped and subducted whereas in the e to nne directed it is ramping upward at the surface there are w directed subduction zones that work also in absence of active convergence like the carpathians or the apennines w directed subduction zones have shorter life 30 40 ma than e or ne directed subduction zones even longer than 100 ma the different decollements in the two end members of subduction should control different ptt paths and therefore generate variable metamorphic assemblages in the associated accretionary wedges and orogens these asymmetries also determine different topographic and structural evolutions that are marked by low topography and a fast eastward migrating structural wave along w directed subduction zones whereas the topography and the structure are rapidly growing upward and expanding laterally along the opposite subduction zones the magmatic pair calc alkaline and alkaline tholeiitic volcanic products of the island arc and the back arc basin characterise the w directed subduction zones magmatic rocks associated with e or ne directed subduction zones have higher abundances of incompatible elements and mainly consist of calc alkaline shoshonitic suites with large volumes of batholithic intrusions and porphyry copper ore deposits the subduction zones surrounding the adriatic plate in the central mediterranean confirm the differences among subduction zones as primarily controlled by the geographic polarity of the main direction of the slab the western margin of the adriatic plate contemporaneously overridden and underthrust europe toward the west to generate respectively the alps and the apennines while the eastern margin subducted under the dinarides hellenides these belts confirm the characters of the end members of subduction zones as a function of their geographic polarity similarly to the pacific subduction zones

short wavelength lower mantle seismic velocity anomalies the lower mantle seismic velocity anomalies display very smooth shapes and low amplitudes in apparent contradiction with the thermal anomalies obtained from chaotic convection models an attempt to reconcile theoretical convection models with tomographic results is presented in this paper along with a coherent approach of lower mantle convection the influences of radial and angular filtering on the shapes and on the amplitudes of anomalies have been monitored a tremendous spreading of the radial anomalies into horizontal structures and a significant loss of amplitude of the anomalies result from this exercice the level of the root mean square of the thermal anomalies falls from several tens of degrees to values in close agreement with tomographic results this study shows that the short wavelength of lower mantle velocity anomalies are dramatically hidden by the truncation level of seismic tomography

global postseismic rebound of a viscoelastic earth theory for finite faults and application to the 1964 alaska earthquake a spherically symmetric earth model with viscoelastic rheology is used to study the postseismic rebound associated with finite lithospheric dislocations we perform a systematic study of surface deformations due to sources characterized by two and three dimensional faults modeled by a linear and planar distribution of point sources our approach is based on the normal mode technique for a layered earth with linear viscoelastic rheology and allows for a self consistent description of the time evolution of postseismic displacements due to strike and dip slip faults as a case study we compare the predicted horizontal displacements due to the 1964 alaska earthquake with very long baseline interferometry vlbi baselines changes observed in this region in the period 1984 1989 although subduction and postglacial isostatic adjustment are expected to contribute significantly to present day velocities our results show that the postseismic rebound due to the 1964 alaska earthquake plays a relevant role in the changes of several vlbi baselines the last section is devoted to the analysis of the evolution of other north american baselines as suggested by recent investigations based on forward approaches isostatic readjustment of the earth s crust in response to the melting of the last pleistocene ice sheets is a major contributor to baseline variations in this area our results indicate that a correct interpretation of vlbi baseline changes in north america should account also for the effects of postseismic deformation

observations of static coulomb stress triggering of the november 2011 m5 7 oklahoma earthquake sequence in november 2011 a m5 0 earthquake occurred less than a day before a m5 7 earthquake near prague oklahoma which may have promoted failure of the mainshock and thousands of aftershocks along the wilzetta fault including a m5 0 aftershock the m5 0 foreshock occurred in close proximity to active fluid injection wells fluid injection can cause a buildup of pore fluid pressure decrease the fault strength and may induce earthquakes keranen et al 2013 links the m5 0 foreshock with fluid injection but the relationship between the foreshock and successive events has not been investigated here we examine the role of coseismic coulomb stress transfer on earthquakes that follow the m5 0 foreshock including the m5 7 mainshock we resolve the static coulomb stress change onto the focal mechanism nodal plane that is most consistent with the rupture geometry of the three m 5 0 earthquakes as well as specified receiver fault planes that reflect the regional stress orientation we find that coulomb stress is increased e g fault failure is promoted on the nodal planes of 60 of the events that have focal mechanism solutions and more specifically that the m5 0 foreshock promoted failure on the rupture plane of the m5 7 mainshock we test our results over a range of effective coefficient of friction values hence we argue that the m5 0 foreshock induced by fluid injection potentially triggered a cascading failure of earthquakes along the complex wilzetta fault system

the effect of small scale structure on normal mode frequencies and global inversions presently very little is known about the characteristic length scales of the structures in the upper mantle in generating synthetic seismograms and in large scale inversions one usually assumes that the upper mantle is smooth so that ray theory can be used however it is known that structures in the mantle exist on a scale of a few hundred kilometers notably near subduction zones and other tectonic features in this paper a model of all the subduction zones and spreading ridges is used to investigate the effect of small scale structures on normal mode frequency shifts and on global inversions the normal mode frequency shifts for this model have the same characteristics as observed normal mode frequency shifts furthermore the global models obtained from inversions of synthetic data for the model of subduction zones and spreading ridges are similar in character to the models obtained from global inversions of real data for a realistic set of wave paths the model obtained from the synthetic inversions differs appreciably from a smoothed version of the true model this is due to an uneven path coverage and to a lesser extent due to neglecting scattering effects this means that the models obtained from global inversions of seismological data may contain appreciable artifacts

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

geodetic strain rate and earthquake size new clues for seismic hazard studies abstract earthquakes deliver in few seconds the elastic energy accumulated in hundreds of years where and when will be the next earthquake remains a difficult task due to the chaotic behaviour of seismicity and the present lack of available tools to measure the threshold of the crustal strength however the analysis of the background strain rate in italy and the comparison with seismicity shows that larger earthquakes occur with higher probability in areas of lower strain rate we present a statistical study in which a relationship linking the earthquake size magnitude and the total strain rate sr is found we combine the information provided by the gutenberg richter law gr of earthquake occurrence and the probability density distribution of sr in the italian area following a bayesian approach we found a simple family of exponential decrease curves describing the probability that an event of a given size occurs within a given class of sr this approach relies on the evidence that elastic energy accumulates in those areas where faults are locked and the sr is lower therefore in tectonically active areas sr lows are more prone to release larger amount of energy with respect to adjacent zones characterised by higher strain rates the sr map of italy compared with 5 years seismicity supports this result and may become a powerful tool for identifying the areas more prone to the next earthquakes

buoyancy driven flow in a confined aquifer with a vertical gradient of permeability we examine the injection of fluid of one viscosity and density into a horizontal permeable aquifer initially saturated with a second fluid of different viscosity and density the novel feature of the analysis is that we allow the permeability to vary vertically across the aquifer this leads to recognition that the interface may evolve as either a rarefaction wave that spreads at a rate proportional to t a shock like front of fixed length or a mixture of shock like regions and rarefaction wave type regions the classical solutions in which there is no viscosity ratio between the fluids and in which the formation has constant permeability lead to an interface that spreads laterally at a rate proportional to t 1 2 however these solutions are unstable to cross layer variations in the permeability owing to the vertical shear which develops in the flow causing the structure of the interface to evolve to the rarefaction wave or shock like structure in the case that the viscosities of the two fluids are different it is possible that the solution involves a mixture of shock like and rarefaction type structures as a function of the distance above the lower boundary using the theory of characteristics we develop a regime diagram to delineate the different situations we consider the implications of such heterogeneity for the prediction of front locations during text co 2 sequestration if we neglect the permeability fluctuations the model always predicts rarefaction type solutions while even modest changes in the permeability across a layer can introduce shocks this difference may be very significant since it leads to the text co 2 plume occupying a greater fraction of the pore space between the injector and the leading edge of the text co 2 front in a layer of the same mean permeability this has important implications for estimates of the fraction of the pore space that the text co 2 may access

global love wave phase velocity variation and its significance to plate tectonics abstract global love wave phase velocity variation was constructed for periods between 80 and 200 s by using approximately 9000 paths from 971 earthquakes with m 5 5 the data set was from gdsn and geoscope networks between 1980 and 1987 we examined both the spherical harmonic expansion method and the block parameterization method with a simple constant damping parameter approach synthetic tests showed that more accurate results were obtained by the block parameterization method than by the spherical harmonic expansion method we adopted the block inversion method with a nearly equal area block 5 5 near the equator discretization the general pattern of the resulting maps were consistent with previous global and local studies with a discretization of 5 by 5 the maps were detailed enough to test some plate tectonic models for the pacific atlantic and indian oceans surface wave velocities increased smoothly to plate ages older than 100 ma simple forward modeling showed that seismic phase velocity variation with a continuous thickening of lithosphere up to about 150 ma fits the present observation disagreeing with the model deduced from the heat flow and ocean depth data which change variations at about 60 80 ma the seismic phase velocity variations in different oceans showed systematic differences at younger ages and convergence beyond 100 ma the difference at younger ages implies a failure of scaling derived from a simple thermal boundary layer model for oceanic plates age seismic phase velocity relationships on each side of ridges were also examined and asymmetric velocity variations were found which suggests differences in thermal states from one side of the ridge to the other in order to further examine the thermal state of the lithosphere average age phase velocity relations were established for each ocean and subtracted from phase velocity variation maps the results indicated broad low velocity regions in the south pacific super swell region the south and west indian ocean and high velocity regions east of the east pacific rise and in the north to northeast indian ocean the results reflect the asymmetry of phase velocity variation about ridges there is some correlation between hot spot locations and low velocity anomalies but additional large scale thermal anomalies exist under old oceanic plate

comparison between tomographic structures and models of convection in the upper mantle summary gruneisen s and third order finite strain theories are used to compute the density and seismic wave velocities of minerals assuming the minealogical model of ito takahashi 1987 seismic velocities of the upper mantle are calculated using the hashin shtrikman averaging procedure 1 d profiles are first obtained along adiabats and compared to the iasp91 model different adiabats are considered in order to take into account the thermal effect of phase transitions the best results are found with adiabats initiated at 1473 1573 and 1613 k for olivine and spinel respectively the incorporation of thermal effects resulting from phase transitions gives velocity jumps at discontinuities close to those of iasp91 next a model of convection constructed by dupeyrat sotin parmentier 1995 incorporating plate tectonics is used to compute 1 d profiles and 2 d fields of seismic anomalies in the upper mantle averaged profiles show seismic velocity gradients very close to those of iasp91 but individual values are much too high suggesting that the mean temperature profile of the convection model is too cold by 400 k when low pass filtered to the resolution scale of presently available tomogrphic models both the amplitude and shape of the computed seismic anomalies are consistent with the results of tomographic studies the amplitude of the anomalies ranges between 2 7 and 3 8 for p wave slownesses and from 3 3 to 4 5 for s wave slownesses these anomalies correspond to lateral temperature variations of 465 to 520 k these calculations are used 1 as an aid to the interpretation of global tomographic models for instance by computing spectra of lateral heterogeneities and 2 to test the adequacy of the basic assumptions used in the computation of numerical models of mantle convection and to build a theoretical temperature profile that would give the best fit to iasp91 in the uppermost mantle this theoretical model has a shape close to both the convection model and the 1473 k adiabat but in the transition zone the profile is highly subadiabatic the spectra obtained for the synthetic seismic anomalies resemble that of tomographic studies with most of the energy contained within gravest angular orders l and a fast decrease of energy with increasing l the spatial filtering has clearly different effects on heterogeneities depending on their respective wavelengths it is suggested that the change of decreasing rate observed in tomographic models at l 7 is closely related to the filter wavelength and may correspond at a lesser extent to a characteristic wavelength to mantle heterogeneities

intermittent layered convection in a model mantle with an endothermic phase change at 670 km it is not yet known whether convection in the earth s mantle occurs in cells that extend throughout the entire depth of the mantle or if the upper and lower mantle convect in independent layers both possibilities seem to be consistent with geochemical and seismologi cal observations1 4 it is generally accepted however that the seismologically observed boundary between the upper and lower mantle at 670 km depth arises from the endothermic phase change spinel perovskite mgo here we investigate the results of including this phase change in a model of mantle convection for realism and to eliminate scaling problems our calculations use commonly accepted values of geophysical parameters for a clapeyron slope y 2 106 a value close to experimental results and theoretical expectations we observe local intermittent mixing between the upper and lower mantle such behaviour may offer a way to reconcile the existence of geophysical evidence for both whole mantle and layered convection

experimental insights on the development of buoyant plumes injected into a porous media we describe a series of new laboratory experiments which examine the rise of a two dimensional buoyancy driven plume of freshwater through a porous layer initially saturated with aqueous saline solution measurements show that the plume head accounts for a constant fraction of about 0 7 of the buoyancy supplied at the source and that it grows as it rises through the porous layer however the morphology of the plume head becomes increasingly complex as the ratio of the injection speed to the buoyancy rise speed increases with the fluid spreading laterally and developing localized buoyant fingers which intermingle with the ambient fluid behind the plume head a tail of nearly constant width develops providing a pathway from the source to the plume head these starting plume dynamics may be relevant for buoyancy driven contaminant dispersal and also for the convection which develops during co2 sequestration as co2 dissolves into aquifer water

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

three dimensional structure of the upper mantle beneath the atlantic ocean inferred from long period rayleigh waves 2 inversion the three dimensional shear wave velocity structure of the upper mantle beneath the atlantic ocean is investigated by inversion of fundamental mode of rayleigh wave group and phase velocities the results are reliable down to 300 km depth and improve upon the image of upper mantle structure given by global tomographic models the inversion of two dimensional lateral distributions of group and phase velocities regionalized without a priori constraints shows that shear wave velocities are correlated with lithospheric age beneath the north atlantic our data set fails to quantify the correlation between shear velocities and lithospheric age because of the small lateral extent of young regions 22 ma and of strong transverse gradients in contrast with similar studies in the indian and pacific oceans slow velocities associated with the location of the mid atlantic ridge are restricted to the lithosphere therefore the atlantic mid oceanic ridge behaves as a shallow structure which is weakly related to deep upwelling asthenospheric flows at depths greater than 200 km the central part of the atlantic is characterized by the highest velocity anomaly this anomaly can be interpreted in different ways part of this anomaly might correspond to a negative vsh vsv vsv ratio implicitely included in the isotropic inversion we also tentatively interpret this anomaly as an important contributor to a shallow degree two pattern of shear wave velocity distribution for the atlantic area