contemporaneous extension and compression in the northern apennines from earthquake fault plane solutions summary the northern apenninic arc belongs to the deformation zones surrounding the adriatic plate which behaves as a rigid block it is a ne verging fold and thrust belt which developed since the miocene with the migration of an extensional compressional pair previous seismological data are roughly in agreement with this deformation picture although the outer compressional front was not clearly defined by the few available solutions in this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the northern apennines defining the extent of these two zones and their interim1 deformation better than was previously done this is accomplished through the analysis of 125 new focal mechanisms of earthquakes 2 6 md 4 8 recorded by the national network of the lstituto nazionale di geofisica in the period 1988 1995 the two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the emilian tuscan apennines strikeslip events are scattered in most of the study area thrust faulting earthquakes are located in the internal part of the most recently active thrust front middle upper pleistocene there is a general trend of the compressional p axes of thrust fault and strike slip solutions to be perpendicular to the apenninic direction in the external zone while the tensional axes of the normal fault and strike slip solutions in the belt do not show a uniform orientation however clearly evident is the ene direction of extension in the peri tyrrhenian region consistent with the direction of shmln in the quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault plane solutions we determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault plane solutions determined in this study we found that the external belt is characterized by ne sw compression ol horizontal oriented n45 e while a normal faulting regime with o3 e w oriented is characteristic of the umbria tuscany back arc region

the structure and geomorphology of the dashgil mud volcano azerbaijan the large scale and small scale 10 m structure and geomorphology of the active dashgil mud volcano in central azerbaijan have been studied through historical records it is known that this mud volcano has major eruptions every 6 32 years the activity observed during two field trips in 1995 consisted of low energy venting and debouching of mud water oil and gas from three mud pools salses and about 20 individual cones gryphons located on the summit plateau of the mud volcano besides the bubbling mud pools ranging from 30 to 75 m across and the cones ranging from 0 8 to 3 m height a 200 m long string of about 10 sinter mounds was found on the summit plateau the internal structure of the mud volcano and the processes responsible for the observed dashgil geomorphology are discussed assuming the dashgil mud volcano to be continuously active with an average methane production similar to that observed in 1995 between the rare major eruptions we have conservatively estimated the dashgil mud volcano to produce an annual amount of at least 800 sm3 standard cubic metres of gas mainly methane which is emitted directly into the atmosphere this estimate indicates that the natural contribution of atmospheric greenhouse radiatively active gases from the world s terrestrial and submarine mud volcanoes is highly significant

the nature and hydrogeologic significance of mud diapirs and diatremes for accretionary systems in accretionary wedges often morphologically similar sedimentary intrusions when observed by remote geophysical means may have one of two quite different driving mechanisms and a highly variable significance for the regional hydrogeologic picture for example mud diapirs are driven by buoyancy forces that arise from bulk density contrasts in them mud and pore fluid upwell en masse and fluid migration is a related sometimes important but generally subsidiary process in contrast diatremes contain sediments fluidized during rapid fluid advection and are forcibly and directly driven by the hydrogeologic system the nature of fluid input from local and exotic source regions can therefore strongly affect sedimentary intrusive processes and vice versa this complicates the process of defining the main features of the hydrogeological systems operating in accretionary wedges focused vertical advection through steep sided piercement mud diapirs requires conduit systems otherwise flow will be diffuse and directed more horizontally out of the low permeability mud mass however where the permeability of the overburden is less than that of the diapir the whole diapir may act as a conduit apart from this special case conduits will be associated with highly anisotropic scaly fabrics that can sometimes develop in the marginal shear zone of diapirs scaly fabrics form during deformation and compaction of a mud matrix under conditions of constant or increasing effective stress however the effective stress path can be complex as it is both controlled by the relative rates of upward intrusion and burial by sedimentation and or structural thickening and the hydrogeologic system due to this it appears likely that even in a geographically related group of diapirs effective stress histories will vary widely between intrusions so that some can form advective pathways for fluids and some cannot mixed systems of behavior may also be present with local diatremes developing within diapirs above the terminations of conduit systems and rapidly expanding methane gas pockets the potentially heterogeneous near surface behavior may be why the surface manifestations of sedimentary intrusions are so variable when observed in the field diatremes can also form separately as large primary features above any structural or stratigraphic conduit that rapidly expels water or gas into the base of an unlithified sediment column when active large diatremes require enormous quantities of fluid water or gas to drive them particularly if they are long lived features and hence are a direct indication of at least an episodically vigorous hydrogeologic system

fluid flow in and around a mud volcano field seaward of the barbados accretionary wedge results from manon cruise a field of mud diapirs and mud volcanoes situated in the barbados trench at 13 50 n and extending along an old oceanic fracture zone mercurus was investigated during the manon cruise using both surface ship and nautile submersible sampling and measurements the entire zone from 13 50 n up to 14 20 n has an anomalously high heat flow which implies that fluids are drained into it from a segment of the accretionary wedge a few hundred kilometers wide two structures interpreted as diatremes atalante and cyclops expell large amounts of water and methane we propose that they were formed from the release of a light fluid when gas hydrates were dissociated in the sediment as the result of the circulation of warm fluid in the area however they expell only a small fraction of the incoming fluid implying that disperse flow is the dominant mode of expulsion in this area the chemoautotrophic communities on the surface of the structures rely mostly on sulfides submersible observations temperature measurements in the sediment and the chemistry of the pore fluid indicate that convection of seawater occurs within the first few meters of sediment through high permeability channels such as cemented carbonate conduits we propose that this convection is driven by the density difference between the pore fluid and seawater but fresh water released by the dissolution of shallow hydrates may also contribute this shallow convection may be a frequent process in cold seep environments

postseismic deformation following the 1997 umbria marche italy moderate normal faulting earthquakes 1 we combine aftershock strain mapping gps measurements and leveling profiles with forward modeling of viscoelastic relaxation to study the postseismic deformation of the 1997 umbria marche central apennines earthquake sequence we explore the feasibility of gps monitoring of postseismic transients for the first time in italy generated by shallow and moderate sources our data allow us to distinguish a preferred coseismic faulting model as well as insight into the rheology of the central apennines earth s crust the faulting model requires a listric geometry with most of the energy released in the lower half part of the elastic crust the rheological model consists of an elastic thin upper crust a transition zone of about 1018 pa s underlain by a low viscosity lower crust ranging from 1017 to 1018 pa s the postseismic deformation is both distributed in the transition zone lower crust and confined to the fault zone

a new estimate of global methane flux from onshore and shallow submarine mud volcanoes to the atmosphere a new estimate of global methane emission into the atmosphere from mud volcanoes mvs on land and shallow seafloor is presented the estimate considered a lower limit is based on 1 new direct measurements of flux including both venting of methane and diffuse microseepage around craters and vents and 2 a classification of mv sizes in terms of area km2 based on a compilation of data from 120 mvs the methane flux to the atmosphere is conservatively estimated between 6 and 9 mt y 1 this emission from mvs is 3 6 of the natural methane sources and is comparable with ocean and hydrate sources officially considered in the atmospheric methane budget the total geologic source including mvs seepage from seafloor microseepage in hydrocarbon prone areas and geothermal sources would amount to 35 45 mt y 1 the authors believe it is time to add this parameter in the intergovernmental panel on climate change official tables of atmospheric methane sources

onset development and cessation of basal early triassic microbialites betm in the nanpanjiang pull apart basin south china block abstract new investigations in the nanpanjiang basin indicate that the onset of the iconic microbialites associated with the paleozoic mesozoic boundary was early triassic in age bathymetry water agitation oxygenation light penetration and clastic load are shown to have exerted a direct control on the growth of microbialites carbonate supersaturation is also required for the deposition of the microbialites bathymetric control is further corroborated by the inheritance of the topography of a latest permian pull apart basin into early triassic times with a distribution of basal early triassic microbialites betm restricted to uplifted blocks and the accumulation of carbonaceous black shales in adjacent troughs the geographically most extensive nanpanjiang betm bloomed on a large nw se trending uplifted block exceeding 12 000 km 2 luolou platform centered on northwestern guangxi post triassic displacements along the youjiang fault obscure the paleogeographic relation of betm exposed west of this fault triassic foraminifers occur in the basal most betm episode which is locally bracketed by high energy grainstones made of reworked permian foraminifers therefore the permian triassic boundary ptb is within the unconformity that separates the late permian heshan fm from the basal most betm where accommodation space was sufficient up to five event surfaces are associated with the unconformity microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion although intercalated grainstone made of permian foraminifers indicate reworking chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity the upward shift from tabulated to domical microbial build ups is accompanied by accumulation of coquinoid lenses between domes which indicates deepening of the luolou platform betm the main drowning resulting from both regional tectonic subsidence and a global sea level rise led to the cessation of the betm that were buried under predominant fine siliciclastics any concomitant change in sea water chemistry appears unlikely

deep crustal roots beneath the northern apennines inferred from teleseismic receiver functions abstract teleseismic waveforms recorded by a regional array crossing the northern italian peninsula and northern corsica are analyzed using the receiver function technique to determine the first order crustal structure the receiver function approach is used to isolate receiver side ps conversions generated at the crust mantle boundary and any major velocity discontinuity beneath the stations we used the time delay between the direct p wave and the ps wave converted at the moho discontinuity to infer crustal thickness beneath the stations the crust mantle boundary is estimated at 25 1 km of depth in northern corsica 20 2 km beneath the elba island and 20 to 24 2 km beneath tuscany in the eastern portion of the array moho depth increases from 28 2 km beneath the adriatic coast to 49 3 km beneath the apennine chain in a distance of about 100 km a double ps conversion produced beneath the val tiberina graben to the west of the apennines corresponds to interfaces as deep as 20 2 and 52 2 km this observation supports the hypothesis of partial overlapping between the shallow tuscan moho and the deeper adriatic moho the westward deepening of the adriatic moho beneath the northern apennines can be explained by lithosphere delamination that has dragged downward the adriatic lower crust the deep crustal root estimated beneath the northern apennines indicates that this portion of the chain is isostatically overcompensated

active tectonics in central italy constraints from surface wave tomography and source moment tensor inversion abstract we investigate the lithosphere asthenosphere structure and active tectonics of central italy with emphasis on the umbria marche area by means of surface wave tomography and seismic moment tensor inversion the data include a large number of short period local and regional group velocity measurements sampling the umbria marche apennines and the adria margin respectively incorporation of published phase velocity measurements sampling italy and surroundings results from deep seismic soundings which go through the umbria marche area the local group velocity maps covering the area reactivated by the 1997 1998 umbria marche earthquake sequence suggest an intimate relationship between the lateral earth structure variations and the distribution of the active fault systems and related sedimentary basins the upper crustal models reveal the importance of inherited compressional tectonics on the recent extensional deformation and associated seismic activity source inversion studies of the main events of the 1997 earthquake sequence show the dominance of normal faulting mechanisms whereas selected aftershocks between the fault segments at the step over reveal that the prevailing deformation is of strike slip faulting type at the regional scale the crust exhibits clear layering and varies in thickness from about 25 km below the tuscan metamorphic complex tmc to about 30 km below the val tiberina extensional thick sedimentary basin and reaches about 35 km below the umbria marche geological domain umd the lithospheric mantle lid is thin about 30 km below tmc while it is about 70 km thick below umd a lithospheric root about 120 km wide between the tmc and umd reaches a depth of at least 130 km a low velocity zone defined mantle wedge vs less than 4 2 km s in the uppermost mantle overlying the high velocity lid is detached this wedge is about 20 km thick and decouples the underlying lid from the crust the retrieved crust and upper mantle structure beneath central italy is in agreement with bouguer anomaly and heat flow data and supports a delamination process the high velocity upper mantle underlying the mantle wedge is inferred to be subcrustal lithospheric material delaminated from the overlying crust

active stress map of italy we present a new map of the present day stress field in italy obtained from all the available data the map reports 200 horizontal stress directions inferred from 109 borehole breakout data 44 centroid moment tensor solutions 34 other focal mechanisms most of which are from polarity distributions seven stress inversions of microearthquake data two averages of t and p axes of earthquake focal mechanisms in zones of diffuse seismic activity and four fault slip data the integration of breakout data which yield horizontal stress directions with fault plane solutions which reflect the stress regime allows us to obtain an improved map of the present day stress in italy this stress field map can be used for a better comprehension of active tectonic processes for seismic hazard assessment and to foresee the behavior of faults recognized with other methods stress directions obtained from different data although relative to different depth intervals e g 0 7 km for breakouts and 0 20 km for most of the earthquakes and to different tectonic units are consistent since many regions in italy are characterized by an extensional stress regime we report the minimum horizontal stress shmin orientations the map shows that an extensional regime affects most of the apenninic belt conversely a compressional or transpressional regime characterizes the eastern alps the eastern side of the northern apennines and the southern tyrrhenian to northern sicily zone an abrupt change in stress directions marks the transition between northern and southern apennines suggesting that the two arcs are characterized by a different tectonic setting and recent evolution in this paper we report all the data analyzed to date with their geographic coordinates and average stress directions and we describe the main stress provinces in italy in the framework of the tectonic evolution of the region

genesis and evolution of the watukosek fault system in the lusi area east java abstract detailed analysis of two dimensional seismic lines acquired in the ne java basin has been performed to unravel the subsurface geology of the region around the lusi mud eruption this work revealed the existence of a system consisting of a complex set of faults here called the watukosek fault system forming triangular deformation zones converging at the top of the early miocene carbonates this system continues downwards with vertical individual fault segments often bordering the steep margins of the carbonate platforms the analysis of data includes the interpretation of seismic lines regional structural data inferred from basement gravity maps and present day main direction of stress results suggest that a possible rotation of stress direction from n40e s40w to n s occurred during the post miocene history of the java back arc tectonic evolution the watukosek fault system was first generated as a tensional lineament during the e w sinistral transpressive strain which involved the basement in this phase synthetic and antithetic riedel faults formed the former controlling the nw se orientation of the structural highs represented by oligo miocene carbonate platforms as a consequence of the rotation of the main principal stress direction to a n s direction the watukosek fault and similar parallel lineaments became sinistral riedel shears developing intense triangular deformation zones based on the stratigraphic position of gentle anticlinal deformations with axis corresponding to the n40e s40w oriented triangular deformation zones the transpressive strain linked to the n s main stress compression occurred likely in the late pliocene early pleistocene the detailed examination of a stratigraphy at the wells bjp 1 and porong 1 as well as b the seismo stratigraphic architecture of the entire succession in the study area allowed a new subsurface interpretation and revision of the stratigraphic units below lusi the thick early miocene tuban formation is found sandwiched between the coheval upper kalibeng formation and the early miocene carbonate of the kujung formation which in turn overlain the older ngimbang formation

subduction related intermediate depth and deep seismicity in italy insights from thermal and rheological modelling geological data suggest that after a period of oceanic lithosphere subduction about 170 km of continental lithosphere were subducted under the northern apennines since about 23 myear at rates of ca 1 cm year whereas more than 700 km of mesozoic oceanic lithosphere ionian lithosphere have been subducted under the calabrian arc at rates of about 3 cm year however a well developed wadati benioff zone can be only recognised below the calabrian arc down to depths of 450 500 km whereas intermediate depth seismicity reaches maximum depths of about 90 km under the northern apennines we model the thermal state of these two subduction zones and apply temperature dependent non linear rheological laws to evaluate the down dip extent of brittle regions in the two subduction zones we show that differences in subduction rate and in slab composition continental vs oceanic produce a far deeper down to 290 380 km brittle field in the colder calabrian slab than in the warmer northern apenninic slab 70 120 km thus explaining differences in the maximum depth of seismicity in both regions concerning deep earthquakes in the calabrian subduction zone models predict that metastable olivine persists down to depths of 430 km this could possibly explain the maximum depth of earthquakes in the area the small extent of the metastable olivine wedge produces a small density anomaly that cannot explain the pervasive down dip compression observed in the ionian slab 2004 elsevier b v all rights reserved

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

shallow rooted mud volcanism in lake baikal abstract lake baikal is the only freshwater basin containing sediments with gas hydrate accumulations some of which are associated with mud volcano activity twenty two mud volcanoes have already been identified in different areas of lake baikal but the formation process and source depth remained unknown due to a lack of conclusive evidences here we discuss a set of geological and geophysical data to report the discovery of the hydrate bearing akadem mud volcanic complex amvc on the academician ridge in central lake baikal the obtained results allowed for the first time to concretely estimate the source depth of the mobilized fluids and sediments analysis of diatom skeletons present in the mud breccia revealed that the oldest diatom specimen is cyclotella iris et var this species is characteristic for a short age interval ranging between 4 8 and 5 6 ma the same diatom was also detected between 230 and 310 m below the lake floor mblf in the borehole bdp 98 drilled near the amvc combining biostratigraphic correlation and seismostratigraphy it is estimated that the same interval is located at 200 300 mblf below the mud volcanic field the elevated heat flow measured at amvc indicates that the original base of gas hydrate stability regionally located at 212 mblf is currently shifted upwards of 100 m the acquired data are consistent with a scenario envisaging the rise of warm fluids throughout the mud volcano complex zone we suggest that migration of deep fluids could have initiated the gas hydrate dissociation and in turn rapidly generated overpressured shallow mud chambers the ultimate piercing and triggering of the mud volcanoes activity resulted in the eruption of mud breccia and formation of densely packed crater sites in the study area the depicted scenario can be applied to many mud volcanoes in lake baikal where similar anomalous heat flow conditions have been measured these findings also emphasize that the genetic association between gas hydrate dissociation and the initiation of eruptive activity explains numerous peculiarities of the baikal sedimentary volcanism e g lack of lithified rocks among mud breccia clasts gas hydrates moderately elevated heat flow this type of mud volcanism differentiates from the typically deeply rooted piercements observed worldwide in mature marine sedimentary basins ultimately our findings open a new prospective for mud volcano research worldwide emphasizing that gas hydrates are not just one of the common features for sedimentary volcanism but may have an active role as a triggering mechanism for the process itself

fracturing processes due to temperature and pressure nonlinear waves propagating in fluid saturated porous rocks a model is proposed of rock deformation fracturing in the subsurface of hydrothermal systems in response to deep fluid rock temperature and pore fluid pressure perturbations carried upward by hot and pressurized fluid fronts since during these episodes of unrest one also has to take into account that rock parameters can evolve a model of fluid diffusivity change as a function of pore fluid pressure is described through reformulating the linear thermoporoelastic equations rock deformation fracturing is thus thought of as being associated with migration of thermomechanical nonlinear waves which travel upward associated with an increase in concurrent fluid diffusivity on dynamical grounds it is assumed that on the boundary of the two superimposed horizons the overlying rock suddenly starts rupturing caused by the arrival of supercritical water from below which drives up a pore fluid pressure excess in this connection the purpose of this analysis is to investigate the general evolution of the subsurface pressure and temperature fields assuming that the original signal is itself strong enough to generate fracturing processes of the overburden rock on its arrival a general formulation provides evidence of nonlinear thermal waves compensated waves and residual pressure burgers waves that can be found for every value of the system parameters a mechanical analogy is also presented which is treated analytically and numerically allowing one to gain intuitive insight into such complex phenomena a characteristic of these nonlinear processes is that the resulting timescales of the order of years for the case of the campi flegrei and the izu peninsula can be particularly small corresponding to quick hyperthermal phenomena during the filtrating movement of fluid toward the earth s surface

genesis of mud volcanoes in sedimentary basins a solitary wave based mechanism 1 mud volcanoes represent the ground surface morphological expression of highly focused fluid flow inside sedimentary basins sedimentary basins show usually the presence of overpressured compartments encapsulated by low permeability bounds seals which can have different origins capillary barriers with high entry capillary pressure diagenetically sealed formations a mud volcano can be formed in response to the hydrofracturation of such a permeability barrier when introducing the pressure dependence of permeability in poroelasticity the theory predicts the upsurge of fluid pressure fronts after the hydrofracturation of the seal initial shock these fronts take the form of hydro mechanical non linear shock waves which are solutions of a burgers type equation these solitary waves are associated with an upsurge of pore water which depends on the pore fluid pressure gradient carried up with the waves the arrival of these waves at the ground surface can generate mud volcanoes type features with spots of highly focused flow

the volcano electric effect 1 the formation of a magmatic intrusion at depth is responsible for the formation of various thermohydromechanical thm disturbances including the upsurge of shock waves and diffusion of pressure fronts in the volcanic system we couple electromagnetic theory maxwell equations and thermoporoelasticity biot equations to look at the ground surface electrical signature of these thm disturbances the nature of this coupling is electrokinetic i e associated with water flow relative to the mineral framework and the drag of the excess of charge located in the vicinity of the pore water mineral interface the groundwater flow disturbance being related here to the thm disturbances in drained conditions a new set of laboratory data shows that the electrokinetic coupling is very substantial in fractured basaltic and volcaniclastic materials and in scoria with several hundreds of millivolts of electrical potential gradient produced per megapascal of pore fluid pressure variations our theoretical analysis predicts the diffusion of electromagnetic disturbances and quasi static electrical signals these signals can be used as precursors of a volcanic eruption indeed electromagnetic phenomena recorded at the ground surface of a volcanic system once properly filtered to remove external contributions provide a direct and quasi instantaneous insight into the thm disturbances occurring in the heart of the volcanic structure prior and during a volcanic event tomography of the quasi static electrical field is discussed and applied to self potential profiles performed at the piton de la fournaise volcano during the preparation phase of the march 1998 eruption

buoyancy driven deformation and contemporary tectonic stress in the lithosphere beneath central italy we studied the continental deformation and modelled the contemporary flow and stress distribution in the lithosphere beneath central italy we made use of a revisited crust and uppermost mantle earth structure that supports delamination processes the model behaviour is primarily determined by the thick high density lithospheric root to the east and the low viscosity shallow mantle wedge to the west the rate of the modeled crustal motion is in agreement with gps data and the pattern of lithospheric flow explains the heat flux the regional geology and provides a new background for the genesis and age of the recent tuscan magmatism the modelled stress in the lithosphere is spatially correlated with the prevailing stress field and the gravitational potential energy patterns and shows that buoyancy forces solely can explain the coexisting regional contraction and extension and the unusual sub crustal seismicity

magnetic anisotropy of plio pleistocene sediments from the adriatic margin of the northern apennines italy implications for the time space evolution of the stress field abstract the anisotropy of magnetic susceptibility ams of the marine fine grained plio pleistocene sediments that crop out at the eastern adriatic front of the central northern apennines italy indicates a prevalent sedimentary compactional magnetic fabric with variable overprint of the tectonic strain the degree of anisotropy and the geometry of the ams ellipsoids suggest a subdivision of the studied sediments in two distinct ages early middle pliocene and late pliocene early pleistocene the early middle pliocene sediments show a weak but well defined magnetic lineation parallel to the main fold and thrust axes throughout the region analogously to the messinian sediments located in a more internal western position of the apenninic chain since the late pliocene the ams data are not regionally coherent and indicate a reduced and locally variable tectonic influence on the magnetic fabrics the ams data have been integrated with the available geophysical information of the present day stress in the region with the aim to reconstruct the time spatial evolution of the stress field in the adriatic margin of the central northern apennines during the past 5 ma the present day stress field was evaluated using borehole breakout in deep wells about 50 wells focal mechanisms of crustal earthquakes 2 5 m d

episodic fluid expulsion from geopressured sediments numerical simulation of fluid explusion from geopressured sediments using a one dimensional finite difference model shows that large volumes of fluid can be transported through a fractured seal during short lived 100 year expulsion events in this model abnormal fluid pressures are maintained by an impermeable seal when the fluid pressure exceeds 85 of the lithostatic pressure a vertical fracture opens in the seal providing a permeable pathway from the geopressured sediments into the overlying section fluid pressure in the seal decreases as fluid flows through the fracture closing the fracture as sediments in the seal compact once the fracture closes the seal remains impermeable until fluid flowing from deeper in the section increases fluid pressure to the fracture criteria a process that takes 10 000 500 000 years fractures emplaced in relatively incompressible seals such as compacted and or cemented sediments remain open for 20 50 years fluid fluxes through the seal integrated over the life of these events are 1 5 107 kg m2 and temperatures in the overlying sediments are increased by 5 20 c these temperature anomalies decay to less than half their original value in 300 years suggesting that the thermal anomalies observed in wells that are attributed to fluid expulsion formed in response to a very recent or currently active event

mud volcanoes in deepwater nigeria abstract detailed study of 3d seismic data from deepwater nigeria has revealed the presence of features interpreted to be mud volcanoes they occur in an upper slope environment seen as 1 2 km circular features at the seabed seabed cores from the mud volcanoes contain oil gas and sand shale clast content richer than the seabed background pliocene fossils have been identified in the cores demonstrating transport of material from depth the features show a high seabed seismic amplitude above a chimney of chaotic seismic reflections and data wipe out the mud volcanoes in the study area shows two distinct clusters located over deeper structural culminations four active mud volcanoes area 1 are located above a rollover anticline in the central part of the area cuspate listric faults reach the seabed on the up slope side of these mud volcanoes four abandoned mud volcanoes have also been identified with progressively older ages towards the crest of the underlying structure these abandoned features are associated with an extremely chaotic seismic signature a combination of over pressured carrier beds and low integrity top seals are believed to be responsible for the formation of these mud volcanoes it is further believed that gas expansion subsequent to seal failure was the main driving force for what must have been violent eruptions the long lived mud volcano activity over the deep structural closure suggests a plumbing system that focuses on escaping compaction water and hydrocarbons through time in the south west of the study area another cluster of five mud volcanoes is located above a shale diapir the seabed expression of the members of this cluster is more varied some show a positive relief at the seabed while others show circular depressions the largest feature represents an assemblage of many smaller mud volcanoes with a common root system their seismic expression is also different from that of area 1 with a well defined sediment wedge at surface and a shallower root system these features are believed to represent a less violent type of mud volcano characterised by ductile flow tectonic stress due to growth of the underlying diapir is thought to have played an important role during eruption in addition to focused methane escape and the low mechanical strength of the overburden

linking structures with the genesis and activity of mud volcanoes examples from emilia and marche northern apennines italy mud volcanism is known to be strictly linked to tectonic structures since they have the ability to trap hydrocarbon and other fluids and eventually induce them to migrate from a deep reservoir e g sited into an anticline core where large overpressures may be generated to the surface a central theme is how fluids can migrate upward and which is the role in this process of near structures i e structures directly controlling the mud volcano system and far structures i e faults located far away from the mud volcano system in this study we investigate the role of both types of structures in the genesis and evolution of mud volcanoes in particular we investigate six mud volcano case studies from the emilia romagna and marche pede apennine margin in italy through integration of fieldwork interpretation of available seismic reflection profiles and aerial photos the results of these analyses support an intimate link of the investigated mud volcanoes with anticline structures we discuss two different fluid migration settings particularly i mud volcanoes emplaced on outcropping anticlines and ii mud volcanoes located on top of buried structures discerning when fluids are likely to exploit anticline related fracture sets or secondary structures and porosity finally we speculate on how far structures via the seismic triggering may play a role in the occurrence of historical eruption of some of the investigated mud volcanoes

numerical approach to problems of gravitational instability of geostructures with advected material boundaries summary we present a numerical approach for solving 2 d mantle flow problems where the chemical composition changes abruptly across intermediate boundaries the method combines a galerkin spline technique with a method of integration over regions bounded by advected interfaces to represent discontinuous variations of material parameters it allows direct approximation of a natural free surface position instead of a posteriori calculation of topography from the normal stress at the upper free slip boundary we formulate a model where a viscous incompressible fluid filling a square box is divided into layers not necessarily horizontal by advected boundaries across which the density and viscosity change discontinuously no slip or free slip conditions are assumed at the model sides the suggested approach being eulerian avoids the difficulties due to material discontinuities at intermediate boundaries like the moho or the earth s surface and is also free from the deficiencies of the lagrangian approach always resulting in mesh distortion we present two geophysical cases analysed by this technique the first case concerns the formation of sedimentary basins under the effects of heavy bodies sinking in the asthenosphere and of load due to sedimentary infills the second case demonstrates the evolution of salt diapirs and shows how their growth is affected by a laterally inhomogeneous sedimentary layer this numerical approach is well suited for problems of gravitational instability with discontinuities of density and viscosity across advected boundaries

mud volcanism an updated review abstract mud volcanism or sedimentary volcanism represents one of the most intriguing phenomena of the earth s crust with important implications in energy resource exploration seismicity geo hazard and atmospheric budget of greenhouse gases since the first review papers were issued at the beginning of 2000s a large amount of new geological geophysical and geochemical data has been acquired which clarified ambiguous concepts and significantly improved our knowledge of mud volcanism here we offer an updated review of the knowledge and implications of mud volcanoes with emphasis on the terminology used to describe different processes and structures the physical chemical and morphological characteristics of the several fluid emission structures the chemical properties of the released fluids in particular the molecular and isotopic composition of the gas the mud volcano formation dynamics and the several implications for petroleum exploration geo hazards and global atmospheric methane budget this review integrates new fluids data collected in azerbaijan and is complemented with field observations from various mud volcano provinces worldwide although the total number of mud volcanoes on earth is still uncertain 600 main onshore structures with a large variety in shapes and sizes are documented in recent global data sets and several thousand are assumed to exist in the oceans it is clear that a mud volcanoes are broadly distributed throughout the globe in active margins compressional zones of accretionary complexes thrust and overthrust belts passive margins deep sedimentary basins related to active plate boundaries as well as delta regions b they are specifically located in hydrocarbon bearing basins along anticline axes strike slips and normal faults and fault related folds in petroleum systems c they represent a specific category of natural gas oil seepage manifestation often related to deep and pressurised reservoirs d the main engine driving mud volcanism is given by a combination of gravitative instability of shales and fluid overpressure build up followed by hydrofracturing e hydrocarbons are generally of thermogenic origin while microbial gas is released in only a few cases mud volcanism on other planets e g mars and titan and microbial activity associated with gas seepage represent emerging issues and opportunities for future research

mariana blueschist mud volcanism implications for conditions within the subduction zone several recently discovered active mud volcanoes on the nonaccretionary mariana convergent plate margin are erupting slab derived fluids serpentine mud and metamorphosed rocks from depths of as great as 25 km blueschist materials from the metamorphosed subducted plate are contained in the muds pore fluids indicate a depth dependence for decarbonation the mud volcanoes record in situ conditions along the decollement including pressure and temperature conditions and physical properties within the subduction zone similar mud flow material occurs worldwide as sedimentary serpentinite deposits in accreted fragments of former convergent margins making this kind of mud volcanism a more important phenomenon in convergent margins than previously recognized

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

the interplay between global tectonic processes and the seismic cycle in the umbria marche seismogenic region summary for the central apennines peninsular italy a series of tectonic mechanisms are reproduced by means of finite element models in order to study the effects of active tectonics on the seismic cycle in the umbria marche seismogenic zone continental extension and rift push effects induced by small scale convection are modelled within 2 d viscoelastic models of the crust lithosphere system in vertical cross sections perpendicular to the strike of the major tectonic structures under study namely the apennines and the colfiorito fault zone where the 1997 seismic sequence took place with the aim of constraining the active tectonic mechanisms at the regional scale and the behaviour of the fault in the seismogenic zone at the local scale modelled baseline rate of change are compared with newly acquired gps data retrieved from the two permanent gps receivers of camerino came and elba elba deliberately installed along the modelled transect these receivers are located at both edges of the continental extension in the front of the apennines close to the adriatic plate in the east and in the rear of the chain in the tyrrhenian domain the deformation pattern inferred from seismicity and from the geodetic data is consistent with small scale convection in the tyrrhenian domain which reproduces extension in the rear of the apennines and compression in the front of the chain a convective mechanism associated with backarc opening and doming of the asthenosphere provides an extensional rate along a baseline connecting two sites in the front of the chain camerino and in its rear elba comparable to the observed baseline rate of change the viscosity of the lower crust plays a fundamental role in determining the style of stress in the crust lithosphere system once constrained by means of the extensional baseline rate inferred from gps the modelled slip across the colfiorito fault and the modelled earthquake recurrence time are consistent with the 1997 normal fault event and with palaeoseismicity respectively

receiver function arrays a reflection seismic approach summary the receiver function method rfm is a commonly used technique to study the crustal and upper mantle velocity structure early receiver function rf investigations were performed mostly at individual permanent stations they were focused on crustal structures and later on upper mantle velocity discontinuities 410 km and 660 km discontinuities only recently has research been directed towards the study of the lateral 2 and 3 d variability of major velocity boundaries in the crust and upper mantle by receiver function arrays using temporary and permanent three component short period and broad band seismic stations to improve the signal to noise ratio receiver functions are calculated for individual earthquakes and are then binned moveout corrected and stacked we show that this processing sequence is similar to that applied routinely in exploration seismology therefore existing tools from the near vertical data processing can be adopted for receiver functions velocity analysis tools solutions for static and residual static problems coherence enhancement of seismic phases migration etc the high spatial density of seismic stations of recent and future receiver function experiments provides the opportunity and obligation to use the more sophisticated migration methods full wavefield migration commonly and successfully used in exploration seismics parasynthetics calculated by the finite difference method for simple 2 d crustal models are employed here to test our processing approach and to show the potentials and limitations of stacking and migrating rf data we show that binning normal move out nmo corrections stacking and post stack migration of the synthetic data can reconstruct the models reliably with a high spatial resolution

the effect of fluid thermal expansivity on thermo mechanical solitary shock waves in the underground of volcanic domains this work is a further development of the modern thermo poro elasticity theory which has recently been applied to understand how fluid rock coupling dynamics related to unrest episodes in volcanic domains can both determine and occur with ground deformation and rock fracturing processes in particular by reformulating the energy equation one of the two nonlinear heat like equations upon which the thermo poroelasticity theory is based it is shown here how fluid thermal expansivity may influence fluid migration during its movement through subsurface volcanic porous per meable horizons with these new considerations it is found that a recent theory in which fluid rock coupling dynamics is interpreted in terms of thermal and mechanical solitary shock wave propagation remains valid however the natural time scale of the propagating wave is reduced and consequently darcy s velocity is increased as a result of fluid thermal expansivity

stress in the descending relic slab beneath the vrancea region romania we examine the effects of viscous flow phase transition and dehydration on the stress field of a relic slab to explain the intermediate depth seismic activity in the vrancea region a 2 d finite element model of a slab gravitationally sinking in the mantle predicts 1 downward extension in the slab as inferred from the stress axes of earthquakes 2 the maximum stress occurring in the depth range of 70 km to 160 km and 3 a very narrow area of the maximum stress the depth distribution of the annual average seismic energy released in earthquakes has a shape similar to that of the depth distribution of the stress in the slab estimations of the cumulative annual seismic moment observed and associated with the volume change due to the basalt eclogite phase changes in the oceanic slab indicate that a pure phase transition model cannot solely explain the intermediate depth earthquakes in the region we consider that one of the realistic mechanisms for triggering these events in the vrancea slab can be the dehydration of rocks which makes fluid assisted faulting possible

the physics of bubbles in surficial soft cohesive sediments abstract this paper reviews current understanding of the physics of bubbles in soft unlithified cohesive sediments certainly in the top 100 m from the sediment water interface but likely much deeper experimental evidence primarily ct scans and internal pressure records indicate that near surface bubbles grow by elastically compressing and fracturing these sediments which results in thin irregular disks of gas these data do not suggest either plastic or fluid behavior on the part of the bulk sediment in addition there is no hint of capillary invasion of gas into the pores of fine grained sediments the growth rate of an elastic fracturing disk shaped bubble can vastly exceed that of a spherical bubble depending on the eccentricity of the bubble this effect results from the far more favorable surface to volume ratio of flattened bubbles the initial rate of rise of bubbles in cohesive sediments also appears to be governed by a fracture process which is driven by pseudo buoyancy the rate of bubble rise could be controlled by various possible mechanisms but only the predictions from a visco elastic fracture propagation model seem to produce rise velocities that are not ballistic experimental evidence demonstrates that a rising bubble can deviate from its path to the surface if it encounters a zone of sediment with lower lateral fracture toughness such a bubble will begin to move in a lateral direction but stall because pseudo buoyancy is no longer operative subsequent bubbles will do the same and accumulate in the low fracture toughness zone this explains the occurrence of shallow sub seafloor domes of gas and modeling of this process predicts only modest over pressures in such structures

fluid migration and fluid seepage in the connemara field porcupine basin interpreted from industrial 3d seismic and well data combined with high resolution site survey data this study documents the suite of processes associated with source to seafloor fluid migration in the connemara field area on the basis of 3d seismic data well logs 2d high resolution seismic profiles subbottom profiles short cores and sidescan sonar data the combination of datasets yields details about fluid migration pathways in the deep subsurface in the unlithified shallow subsurface and about the distribution of fluid and gas seeps pockmarks at the sea floor the connemara field area is characterized by vertical fluid migration pathways seismic chimneys or gas chimneys that extend from the top of the jurassic sequence cross cutting the entire cretaceous sequence to the upper tertiary deposits over a vertical distance of up to 1 5 km their localization is mainly structurally controlled to the crest of tilted fault blocks along the main hydrocarbon migration pathways these chimneys are important conduits for focused vertical fluid gas flow from the deep to the shallow subsurface however gas seeps pockmarks at the sea floor are almost randomly distributed which indicates a change from focused to diffuse fluid gas migration in shallow unconsolidated sediment where the vertical chimneys reach up to unlithified eocene to miocene sands widespread deformation interpreted as fluidization occurs around the main conduit this deformation affects about 32 of the entire unconsolidated tertiary section late eocene miocene a plio pleistocene glaciomarine drift with up to five horizons with iceberg ploughmarks seals the tertiary sands in the near surface sediments it is observed that gas accumulation occurs preferentially at iceberg ploughmarks it is inferred that lateral migration at five levels of randomly oriented ploughmarks dispersed gas over larger areas and caused random pockmark distribution at the sea floor independent from the underlying focused migration pathways this study demonstrates that fluid flow migration changes from structurally controlled focused flow in the deep consolidated subsurface to diffuse flow controlled by sediment variability in the shallow subsurface this result is relevant to a better understanding of the distribution of seepage induced features at the seafloor related to focused hydrocarbon migration pathways known from industry data and fluid flow modeling

crustal structure and moho geometry beneath the northern apennines italy 1 we used receiver functions rfs from broad band seismic stations to investigate the crustal structure of the northern apennines italy additionally we use data obtained in this study to provide initial constraints for a map of the moho depth of italy ten stations were deployed along a transect n75 e during the 1994 geomodap project rf analysis shows the presence of lateral variations in the crust we observed patterns of symmetric and anti symmetric converted phases from radial and tangential rfs vs back azimuth these patterns can be explained by the presence of dipping interfaces and or anisotropy within the crust we then inverted rfs following the inversion scheme proposed by sambridge 1999 the results show the presence of s velocity inversions in the lower crust beneath the apennines the upwelling of moho in the tyrrhenian area and its progressive deepening from the tyrrhenian sea toward the adriatic coast

three dimensional numerical modeling of contemporary mantle flow and tectonic stress beneath the central mediterranean the structure density and effective viscosity of the crust and uppermost mantle beneath the central mediterranean influence lithospheric deformation mantle flow and tectonic stress state to estimate the contribution of buoyancy forces to regional dynamics three dimensional finite element models are developed to determine contemporary uppermost mantle flow and tectonic stresses we use density models for the crust and uppermost mantle derived from s wave seismic velocities and constrained by gravity data the viscosity model is constrained by the observed strain rate and regional heat flow data the modeled movement of the uppermost crust is consistent with the northeast oriented motion of the lithosphere and is in an agreement with the geodetic measurements the modeled flow patterns of the lower crust and uppermost mantle are consistent with the regional observations the models predict i northwest oriented movements beneath the southeast part of the adriatic sea region ii the northeastern subduction beneath the western part of the adriatic sea iii the upwelling beneath the tyrrhenian sea and its eastern coast iv the western movement of the ionian sea sub plate and v the subduction beneath the western calabria region our models predict also a distinct compressional regime along the northeast part of the italian peninsula and to the east of sicily and a tensional regime beneath the tyrrhenian sea umbria marche region and ionian sea the predicted tectonic stress regimes in the northern and central apennines are in agreement with stress regimes derived from earthquake fault plane solutions changes in the predicted crustal stress pattern and magnitude are likely to be caused by buoyancy driven mantle circulation beneath the region rather than by gravitational potential energy differences in the crust itself based on the model results we conclude that the buoyancy forces play an important role in the contemporary tectonics of the region

hydrothermal processes at milos island greek cyclades and the mechanisms of compaction induced phreatic eruptions abstract the few hundred meters thick rhyolitic tuff layers that cover the volcanic island of milos host intense hydrothermal alteration which completely transforms the tuffs into clays and locally into microcrystalline quartz aggregates at the top of one of these quartz layers hundreds of 15 20 m large and 3 4 m deep craters are found randomly scattered over a 1 2 km 2 area in another area craters with smaller diameters 1 2 m and depths 0 5 1 m are found geochemical data reveal that the quartz results from the leaching of the tuff or clay layers by a high temperature 100 200 c flow of steam and gas because of their micrometer size the quartz grains have a viscous rheology due to solution transfer creep the effective viscosity is as low as 10 14 pa s as a result the steam or water saturated porous quartz layers deform by compaction the compaction length is about 3 and 15 m when the fluid is superheated steam and water respectively when the upwelling fluid flow encounters a region with a reduced porosity compaction generates pocket like domains of enhanced porosity these pockets propagate toward the surface by deforming the solid framework of the porous layer one dimensional simulations of the porosity waves show that the steam or water concentration in the pockets likely exceeds 70 the fluid compressibility and viscosity drastically influence the development of the waves for steam like water like fluids the size of the pockets is about 15 20 m 3 4 m and their velocity is about 50 60 m yr 2 4 m yr the fluid overpressure carried by the waves is about 3 4 bar and 0 3 0 5 bar when the fluid is steam like and water like respectively for steam like fluids the 2 4 bar overpressures at the top of the waves are able to re open healed fissures at a depth of about 5 10 m then the steam catastrophically escapes from the rocks through these fissures and the eruption proceeds as a caldera collapse this leads to the suggestion that the arrival of steam pockets can trigger phreatic eruptions that form the 15 20 m large 3 4 m deep craters when the fluid is water like the overpressures are too small to generate an eruption the fluids percolate through the quartz aggregate leading to the formation of 2 3 m wide 0 5 1 m deep bowl like cavities this model is consistent with field observations at milos

modelling of possible mud volcanism on titan possible sedimentary basins on titan are potential sites for the formation of mud volcanoes in order to constrain the appearance of such features in remotely sensed imagery being acquired by the cassini spacecraft we have modelled the formation of mud volcanoes on titan for a series of plausible mud compositions climatic conditions and geological settings as well as addressing the full range of eruption variables mud viscosity conduit diameter and eruption duration we find that for an acetylene mud source containing 20 wt liquid methane in pore spaces overlain by a sheet of water ice 500 m thick a mud volcano can grow as high as 140 m assuming reasonable eruption parameters such an edifice may develop into a pancake like dome several kilometres in diameter if observed and properly characterised mud volcanoes would provide an important window on the subsurface distribution and dynamics of solids and liquids in sedimentary basins on titan

contribution of numeric dynamic modelling to the understanding of the seismotectonic regime of the northern apennines abstract in this paper we investigate the forces possibly active in the area of the northern apennines by means of two dimensional finite element modelling assuming a viscoelastic rheology the forces included in the models are related to continental convergence between africa and eurasia to negative buoyancy of the subducted adriatic lithosphere and to positive buoyancy of anomalously hot mantle material underneath tuscany model predicted stress distribution is compared with seismotectonic data available for the area of the northern apennines and with earthquakes distribution our results indicate that continental convergence cannot be the only mechanism acting in the study area since it causes insignificant subcrustal stresses in disagreement with intermediate seismicity observed under the apennines asthenospheric upwelling under tuscany back arc region is shown to play a crucial role in the present day dynamics of the tyrrhenian apennines positive buoyancy causes an upwards and eastwards flow that generates extensional bending stresses in tuscany and at the top of the slab under the apennines horizontal pushing of the slab is proposed as an alternative mechanism to slab pull to generate subcrustal stresses activation of slab pull does not result in a significant change in orientation of the principal stress axes at shallow depths with respect to the model in which only asthenospheric diapirism is active therefore the existence of a continuous gravitationally sinking slab cannot be ruled out on the basis of comparison with seismotectonic observations both models successfully reproduce extension in tuscany and compression in the outer margin of the apenninic belt but fail to reproduce extension along the inner portion of the chain our modelling highlights the importance of better constraining the lateral extent of the asthenospheric diapir in order to find out whether the extension and tectonic uplift in the apennines is caused by asthenospheric upwelling as in the area of tuscany

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

subcrustal earthquakes in the northern apennines italy evidence for a still active subduction previously unreported subcrustal earthquakes have been located up to 90 km depth beneath the northern apennines italy these earthquakes occur beneath a zone of abundant upper crustal seismicity mostly confined to the upper 20 km of the crust although there are relatively few well located subcrustal earthquakes there appears to be a general southwestward deepening of the hypocenters from the adriatic to the tyrrhenian sea consistent with other geophysical data which suggest that the adriatic lithosphere is presently subducting beneath the northern apennines

probabilistic longevity estimate for the lusi mud volcano east java abstract a new method for estimating the duration of a mud volcano eruption is applied to the lusi mud volcano in east java the estimate is based upon carbonates at depths in the range 2500 3500 m being the water source with an estimated area of 100 600 km 2 thickness of 0 2 1 0 km porosity of 0 15 0 25 an initial pressure between 13 9 and 17 6 mpa and a separate shallower source of mud c 1200 1800 m depth the resulting 50 percentile for the time it takes for flow to decline to 1 is 26 years by analogy with natural mud volcanoes it can be expected to continue to flow at lower rates for thousands of years assuming subsidence rates of between 1 and 5 cm day 1 land surface subsidence of between c 95 and c 475 m can be expected to develop within the 26 year time period

crustal versus asthenospheric relaxation and post seismic deformation for shallow normal faulting earthquakes the umbria marche central italy case summary following a normal mode approach for a strati ed viscoelastic earth we investigate the eiects induced by shallow normal faulting earthquakes on surface post seismic vertical displacement and velocity at the surface when stress relaxation occurs in the crust or in the asthenosphere the modelled earthquake is a moderate one characteristic of some slowly deforming plate boundaries in the central mediterranean region we focus on the umbria marche central italy region where deep seismic re ection studies crop03 and the 1997 earthquake sequence clearly show a seismogenic layer decoupled from the lower crust by a sizeable transition zone accordingly the crust is subdivided into three layers an elastic upper crust a transition zone and a low viscosity lower crust the fault is embedded in the upper crust the layered viscoelastic structure of the crust and mantle imposes a pattern and scale on the modelled coseismic and post seismic deformation with a major contribution from the transition crustal zone and low viscosity lower crust stress relaxation in the mantle being negligible we show that signi cant vertical deformation rates of the order of 1 mm yr 1 could be expected for a shallow and moderate event such as the recent umbria marche earthquake for viscosity values of 10 19 and 10 18 pa s in the crustal transition zone and lower crust respectively

pervasive pressure solution transfer in a quartz sand the kinetics of deformation of a quartz aggregate by pervasive pressure solution can be under certain conditions of temperature and grain size strongly dependent upon the diffusivity of silica into the grain to grain contacts an analysis of the factors affecting this key parameter and less well constrained in the analysis of the problem of rock deformation by pressure solution is presented this analysis is based on recent advances on studying silica surfaces and particularly on the existence of a silica gel layer on the silica surfaces undergoing dissolution by reinvestigating the electroviscous effect occurring at the grain to grain contact the present analysis shows that the diffusivity of silica at the grain to grain contacts is likely to be relatively similar to that in the bulk pore water maybe 1 order of magnitude smaller but not more this contradicts the previous work by rutter 1976 which has been the key reference used in many subsequent papers to justify an extremely low value for the diffusivity of silica at the grain to grain contacts 5 orders of magnitude smaller than the diffusivity of silica in free water this finding has dramatic implications concerning the deformation rate of quartz sands and sandstones by pressure solution in sedimentary basins with regard to 1 the limiting step affecting the kinetics of the process diffusion of the solute or dissolution precipitation chemistry and 2 the existence of a thermodynamic equilibrium state when deformation by pressure solution occurs over geological timescales a poroviscoplastic model is used to describe deformation associated with pervasive pressure solution transfer in quartz sands this model is shown to be consistent with the current state of knowledge of the surface chemistry of silica in addition the comparison between this model and both laboratory and field data is rather good