anomalous seismicity in the lower crust of the santiago basin chile abstract in central chile intraplate crustal seismicity is mostly constrained to the upper 20 km nevertheless sparse observations of earthquakes have been reported deeper without a definitive explanation in the lower crust of the santiago basin located within a compressional subduction environment we have observed a series of events organized in two clusters this work presents a detailed study of these earthquakes recorded from november 2002 to april 2005 with depths from 28 to 36 km and magnitudes ranging from 2 8 to 4 3 using a local network composed of vertical short periods broadbands and accelerometers we performed a time and spectral waveform analysis to determine their exact location and certain source parameters seismic moment corner frequency and seismic energy we found that each cluster presents extremely well correlated waveforms indicating that each event in the cluster ruptures the same patch in the same fashion even more we determined that representative events show a large apparent stress drop releasing six times more energy than interplate events for a given seismic moment the most plausible interpretation seems to be a decollement between the crust and the mantle where few but strong asperities are located in a broader region that continuously creeps we believe that this work will help improve our understanding of the processes involved in subduction zones as well as the assessment of the seismic hazard for the santiago metropolitan area

earthquake nests as natural laboratories for the study of intermediate depth earthquake mechanics article the physical mechanism of intermediate depth earthquakes is still under debate in contrast to conditions in the crust and shallow lithosphere at temperatures and pressures corresponding to depths 50 km rocks ought to yield by creep or flow rather than brittle failure some physical process has to enable brittle or brittle like failure for intermediate depth earthquakes the two leading candidates for that are dehydration embrittlement and ther mal shear runaway given their great depth intermediate depth earthquake processes can t be observed direct ly insteadwe must relyona combination ofseismologyand thestudy of laboratory analogs tounderstand them earthquake nests are regions of highly concentrated seismicity that are isolated from nearby activity in this paper we focus on three intermediate depth earthquake nests vrancea hindu kush and bucaramanga and what they reveal about the mechanics of intermediate depth earthquakes we review published studies of tectonic setting focal mechanisms precise earthquake locations and earthquake source physics at these locations with an emphasis on the bucaramanga nest all three nests are associated with subducting litho sphere and at least two of the nests have consistently larger stress drops compared to shallow seismicity in contrast the bucaramanga nest has a larger b value larger variability of focal mechanisms and shows no evidence of aftershock sequences unlike the other two we also report for the first time finding a signifi cant number of repeating earthquakes some with reverse polarity

interplay between subduction retreat and lateral extrusion tectonics of the western carpathians 1 analysis of brittle microstructures reveals three tertiary deformation events in the western carpathians 1 late paleogene bedding parallel extension 2 oligocene to middle miocene nne ssw compression and ese wnw extension 3 post mid miocene nw se extension these regional deformations applied to crustal blocks in the intra carpathian region resulted from forces which were induced by the coupled plate tectonic processes of subduction retreat beneath the carpathian arc and lateral extrusion from the eastern alps toward the carpathian region material flow from the alps spread toward east and ne guided by sinistral strike slip zones along the ne trending continental margin subduction retreat was terminated by mid miocene soft collision of the inner western carpathians with the european foreland ongoing subduction retreat beneath the eastern carpathians caused post mid miocene back arc extension forming the pannonian basin extension spread into the western carpathians by reactivating the extrusion related strike slip faults as normal faults

three dimensional p wave velocity image under the carpathian arc abstract an inversion of p wave travel time residuals from selected earthquakes in the distance range 30 98 to two seismic station networks was used to model p wave velocity anomalies down to 250 km depth in the first inversion experiment a region between 43 5 47 5 n and 21 29 e was modelled using 35 seismic stations while in the second one a region between 44 47 n and 25 29 e was modelled using 19 seismic stations the 4 layer block model of the first inversion offers 19 reduction in residual variance while the 5 layer block model of the second one offers 26 reduction the rest being explained by noise and smaller scale heterogeneities the obtained velocity anomalies correlate remarkably well with the gravity anomalies and with the tectonic model for the vrancea region of fuchs et al 1979

nature of the vrancea seismic zone eastern carpathians new constraints from dispersion of first arriving p waves abstract the vrancea region of the southeastern carpathians is one of the most active seismic zones in europe and it is well known for its strong intermediate depth earthquakes seismic tomography had revealed a high velocity body beneath vrancea and the moesian platform that extends to a depth of at least 350 km and can be interpreted as descending lithosphere the strong earthquakes occur within the northeastern part of this high velocity body in a very limited seismogenic volume at intermediate depth 70 180 km several geodynamic models have been proposed for this area they can be split into two main categories in terms of the nature of the high velocity anomaly which may a be associated with descending relic oceanic lithosphere beneath the bending zone of the se carpathians either attached or already detached from the continental crust or b it may represent continental lithosphere that has been delaminated after continental collision and orogenic thickening based on currently available information it appears difficult to distinguish between these two types of models in this paper we attempt to shed more light on the nature of the seismic anomaly as well as that of the origin of the intermediate depth seismicity in the vrancea zone by investigating the waveform character of p waves excited by local earthquakes beneath this area and in particular the dependence of group arrival times on frequency we present observations of such a dispersion from stations situated at the bending zone of the se carpathians on the other hand signals from the same earthquakes but observed at reference stations outside of the anomalous zone do not show that frequency dependence a natural explanation for these observations is that it is caused by the presence of a low velocity channel at the top of the seismic anomaly which is too thin to be resolved by classical seismic tomographic techniques similar observations of dispersed first arriving p waves have been made above subduction zones around the world in which low velocity layers with a thickness of several kilometers are known to exist this suggests that a tabular slab of subducted oceanic crust is present within the seismic anomaly under the vrancea region and that the anomaly consists of subducted oceanic lithosphere rather than continental lithosphere at least at depths shallower than the seismically active zone

the evolution of the carpathians pannonian system interaction between neotectonics deep structure polyphase orogeny and sedimentary basins in a source to sink natural laboratory abstract the carpathians pannonian basin system provides a natural laboratory for analysing lithospheric to surface controls on tectonic topography development in a coupled source to sink environment to link processes taking place at depth and at the surface recent research focused on the interplay between basin evolution active tectonics topography evolution and intraplate folding mechanisms neotectonic processes control landscape development and natural hazards in particular the seismicity during the late stage late neogene quaternary evolution of both the carpathians pannonian basin system and its interaction with the adjacent dinarides and balkans the deep structure of the se carpathians exerts a strong control on the post collisional evolution of the system new constraints are available from seismic tomography deep seismic reflection and refraction profiling and detailed studies of the vreancea seismicity inherited orogenic fabric and structure of the active black sea sink has a strong influence on the localisation of the neogene sediment pathways a close relationship has been established between the timing and mechanisms of stress changes in the pannonian and transylvania basins and structural episodes in the surrounding thrust belts pointing to an intrinsic mechanical coupling with these basins the orogen and its foredeep basin inversion taking place during the pliocene quaternary times in the entire carpathians pannonian system is related to changes in the regional stress field leading to differential vertical movements associated with a laterally variable folding mechanism active in the entire system short crustal folding patterns alternate with lithospheric wavelengths in the se carpathians foreland east and south carpathians transylvania and pannonian basins the lateral variability is the result of a marked contrast in rheology between these areas directly related to the crustal configuration thermal properties and late stage collision kinematics with the carpathians foreland lateral variations in the properties of the downgoing plates largely control the collision mode in the carpathians and the post collisional evolution of the entire system

broadband ground motion simulation of the 2004 and 1977 vrancea romania earthquakes using empirical green s function method we estimated the parameters of strong motion generation areas and simulated broadband ground motions for the moderate october 27 2004 m w 5 8 and damaging march 4 1977 m w 7 4 vrancea romania intermediate depth subduction earthquakes using the empirical green s function method the method allows the simulation of ground motions in a broadband frequency range by summing up the subevent records corresponding to small magnitude events in the near source areas which are assumed to follow the source scaling relationship and the omega square source spectral model we first estimated the strong motion generation area that reproduces near source ground motions in a broadband frequency range of 0 3 10 hz for the 2004 earthquake by fitting the synthetic acceleration velocity and displacement waveforms to the observed data the source properties of the obtained strong motion generation area are in agreement with the predictions made using an empirical source scaling relationship for crustal earthquakes implying a stress drop of approximately 10 mpa for the 2004 earthquake we then modeled the strong motion generation area for the 1977 damaging earthquake using the 2004 earthquake as an empirical green s function and constructing a source model based on its estimated source parameters to simulate the unique record at bucharest capital city of romania the rupture was assumed to have propagated from the northeast bottom of the strong motion generation area having a stress drop of 50 mpa broadband ground motion simulations were further compared in terms of the modified mercalli intensity values calculated from the peak ground accelerations and peak ground velocities of synthetic waveforms with the observed medvedev sponheuer karnik intensity values our estimates of the source properties for the 2004 and 1977 vrancea intermediate depth earthquakes support the size dependent stress drop

active crustal deformation from the azores triple junction to the middle east the co seismic crustal deformation along the africa eurasia eurasia arabia plate boundary from the azores triple junction 30 w up to the karliova triple junction 41 e is examined based on the moment tensor summation of mainly post 1964 earthquakes with ms 5 0 strain rates range from 10 8 yr to 10 6 yr while values exceeding 10 7 yr were calculated for the back arc aegean area and for the north anatolian fault zone a remarkable stability in the azimuth of the component of compression and of extension is observed in the area that extends west of italy 17 e up to the azores triple junction along this region the deformation is taken up by compression along a mean direction of n140 with rates from 1 1 to 2 8 mm yr and by extension along a mean direction of n50 with rates from 2 4 to 12 0 mm yr at the gloria fault and in the surrounding area dextral strike slip motion occurs at a rate of 11 mm yr from sicily up to the eastern end of the hellenic arc the crust is compressed at azimuths in the range n20 n31 with an average value of 26 5 this compression is occurring at a rate of 1 21 mm yr with an average value of 9 8 mm yr in the back arc aegean area extension is occurring along a mean azimuth of n156 with a rate of 5 2 3 8 mm yr the average shortening rate along the convex side of the hellenic arc is 12 mm yr from the eastern end of the north anatolian fault 41 e up to the northern aegean trough extension along n68 n179 and compression along n158 n89 occurs which results in dextral strike slip motion the rate of extension reduces from east to west from 30 mm yr to 5 mm yr while the rate of compression reduces from 17 mm yr to 5 mm yr the northwards motion of arabia results in a n31 trending compression at a rate of 7 mm yr along the east anatolian fault zone

neogene kinematics of the transylvanian basin romania the transylvanian basin is a major sedimentary basin located in the eastern part of the european alpine orogenic system it has a sedimentary fill more than 5 km up to 8 km in some small areas thick of upper cretaceous to upper miocene deposits it represents the main gas producing province in romania and central eastern europe in this article we analyze seismic lines and structural data from the basin as well as from its northern eastern and southeastern borders these data indicate a tectonic origin for the neogene structures from the transylvanian basin these structures include 1 northeast and southwest dipping thrust faults and 2 east northeast and west northwest striking strike slip faults having normal or reverse slip secondary structures such as salt diapirs and folds are related to these faults structural data from the basin and its border indicate a neogene overall compressional transpressional regime having maximum principal stress oriented north to northeast daniel ciulavu received a diploma in geology and geophysics at the university of bucharest in 1989 and his ph d in geology at the vrije universiteit amsterdam netherlands in 1999 he worked two years for geasol s a romania in hydrogeology coal and alluvial gold exploration since 1991 he has been on the staff of the university of bucharest where he teaches the courses on structural geology in the department of geophysics and kinematic analysis for master s students corneliu dinu received a diploma in geology in 1966 and his ph d in 1976 at the university of bucharest romania after graduation he worked as field geologist for prospectiuni s a romania since 1970 he has been on the staff of the university of bucharest where he is professor of structural geology and basin analysis since 1990 he has served as the dean of sciences at the faculty of geology and geophysics university of bucharest alexandru szakacs received a diploma in geology in 1974 and his ph d in 2000 at the university of bucharest romania he is senior geologist at the romanian institute of geology he has 25 years of experience in studying the neogene volcanism of the carpathian pannonian area he has also worked on the neogene volcanism of the cordillera betica spain dorin dordea received a diploma in geology in 1974 at the university of cluj romania his field of activity is remote sensing he has worked in several areas in africa and romania since 1999 he has served as the chief geologist of prospectiuni s a bucharest romania he is now working on the application of remote sensing in mining exploration

slab break off abrupt cut or gradual detachment new insights from the vrancea region se carpathians romania slab break off is a plate tectonic process which does not only return lithospheric material into the deeper mantle but also has severe effects on surface movements and seismic hazard slab pull induced seismicity is reduced when the subducted slab decouples from the overlying crust in the vrancea region se carpathians strong earthquakes frequently occur at intermediate depths 70 180 km in a laterally small volume while the crust shows low but distributed seismicity the stress pattern shows similar partitioning with vertical extension in the slab and no preferred orientation in the overlying crust both features indicate a decoupling between slab and overlying crust either by slab break off or delamination however the strong vertical elongation of the slab requires that the upper end of the slab is fixed vertically thus a soft coupling is assumed that is strong enough to enable elongation of the slab but weak enough to inhibit quasi static stress transfer to the overlying crust

seismic scattering and absorption mapping from intermediate depth earthquakes reveals complex tectonic interactions acting in the vrancea region and surroundings romania abstract the vrancea region located at the southeastern edge of the carpathians arc bend is a region of intense seismicity whose major earthquakes produce hazard in southeastern europe despite the consequent focus of the geophysical and geological community on providing accurate structural and dynamical models of vrancea these are still subject to numerous controversies and debates in the present study we use intermediate depth seismicity recorded by the broadband stations of the romanian seismic network between 2009 and 2011 to measure s wave peak delay times and late time coda quality factors after mapping these two quantities in space a cluster analysis provides a quantitative structural interpretation of the region in terms of different attenuation mechanisms affecting the seismic wave field i e seismic scattering and seismic absorption the results show that scattering is higher west and northwest of vrancea while absorption dominates in the focsani basin located in the forearc region in general we obtain higher absorption in stable regions with patterns emphasized at high frequency affected by the presence of hydrocarbons and natural gas reservoirs in the upper crustal layers regions characterized by active seismicity and structural heterogeneity show higher scattering spatially correlated with the highest velocity contrasts and the lowest density the high frequency scattering absorption contrasts obtained using the cluster analysis depict a southwest to northeast lithospheric contrast following the epicentral trend of vrancea earthquakes and characteristic of either lithospheric subduction or delamination low frequency cluster analysis results sampling deeper earth layers mark a unique high absorption trend perpendicular to the epicentral trend feasibly linked to neogene volcanism and induced by the back arc mantle upwelling its most recent expression is ciomadul volcano located at the northwestern limit of the absorption trend

investigation of a high stress drop earthquake on august 30 1986 in the vrancea region abstract several source parameters of the intermediate depth vrancea earthquake from august 30 1986 were computed starting from strong motion data among them most striking for a mw 7 2 event is the high seismic energy 4 5 1023 erg corresponding to ms 7 9 and four independent estimates of effective stress about 1100 bar the high fracture energy per unit area of the fault 2 1010 erg cm2 and a somewhat low apparent stress about 400 bar are indicators of a low rupture velocity a single asperity with an area of about 160 km2 was identified on the 700 km2 fault area the rupture duration of about 4 s is in agreement with the inverse of corner frequency and with teleseismic determinations the depth of the main shock was checked against determinations from pp p intervals and so the initiation of rupture was fixed around 130 km depth

understanding the kinematic evolution and genesis of a back arc continental sag basin the neogene evolution of the transylvanian basin abstract formation and evolution of back arc basins is related to the interplay between subduction and convergence velocities during the formation of an orogenic chain sedimentary basins lacking fault systems that are genetically associated can be locally observed in the hinterland of the main orogenic belt in the usual location of a back arc basin these are interesting features potentially driven by a number of contrasting mechanisms such as lithospheric traction forces driven by plate boundary processes lateral migration of lower crustal material during orogenesis or sub lithospheric processes such as the rapid retreat of subducted slabs the transylvanian basin is a miocene basin that evolved at the rear of the main carpathians arc during the subduction of a slab attached to stable europe the pannonian basin is a typical continental extensional back arc domain to the east transylvania accommodated up to 3 5 km of middle upper miocene sediments deposited in a period coeval with the shortening in the neighbouring carpathians the basin fill was subsequently exhumed and partly eroded when the carpathians collided with the european craton in late miocene times this was associated with contractional deformation and widespread salt diapirism that forms the bulk of miocene deformation observed inside the basin our study shows that no significant normal faults are present inside the basin that could have accommodated 3 5 km subsidence in terms of upper crustal extension furthermore the basin kinematics cannot be linked directly with any other mechanical process explaining the observed miocene subsidence therefore we discuss several mechanisms that may explain regional scale observations and we conclude that the miocene transylvanian basin most likely formed in response to an asymmetric simple shear extension assisted by erosion and or lower crustal flow the upper crustal effects were localized in the neighbouring pannonian basin

quantitative relations of seismic source parameters and a classification of earthquakes abstract relations between earthquake parameters moment m0 fault area s fault length l and width w stress drop time characteristics and magnitudes and faulting type dip slip ds and strike slip ss are quantitatively analyzed using a dataset of 240 events m 5 the analysis is carried further toward an earthquake systematization by introducing earthquake classes the results are 1 1 l w 2 1 for ds l w 2 30 for ss and l w 3 7 for giant m0 1029 dyne cm earthquakes respectively 2 2 log m0 1 5 log s 22 2 s in km2 and tentatively log m0 2 45 log s 17 49 for ds and ss and giant earthquakes respectively 3 3 the large scatter of data in m0 s dependences is the result of the combined effect of the variation in and l w 4 4 the concept of constant is replaced by variable to explain the large variations in relations between m0 s l and w for both ds and ss earthquakes and partly between body and surface wave magnitudes low intermediate and high stress drop gd 30 30 60 and 60 bar respectively earthquakes are defined 5 5 a relation of reciprocity exists between seismic slip fault length and width and stress drop 6 6 a saturation of s for some very large earthquakes is suggested from the interpretation of actual data on m0 s l w etc 7 7 the total source duration tsd increases with m0 in relation with earthquake type and tentatively log m0 2 16 log tsd 24 50 holds for ds earthquakes 8 8 log m0 1 5 mm 16 1 holds for mm brune engen mantle wave magnitude 8 5 8 75 9 9 more magnitudes of shorter or longer period on both body and surface wave basis are useful in constraining significant earthquake features 10 10 low and high frequency earthquakes can be distinguished using the gutenberg richter relation ms mb as a reference relation or a relation between ms and mmaxb 11 11 aki s similarity conditions are extended by adding two more conditions as to express more specifically four basic features geometry deformation frequency and time of the earthquake source 12 12 a reference earthquake is defined by criteria consistent with the similarity conditions 13 13 on this basis and in view of nonsimilarity of earthquakes in their totality a scheme for earthquake classification is proposed

source parameters of intermediate depth vrancea romania earthquakes from empirical green s functions modeling abstract several source parameters source dimensions slip particle velocity static and dynamic stress drop are determined for the moderate size october 27th 2004 mw 5 8 and the large august 30th 1986 mw 7 1 and march 4th 1977 mw 7 4 vrancea romania intermediate depth earthquakes for this purpose the empirical green s functions method of irikura e g irikura k 1983 semi empirical estimation of strong ground motions during large earthquakes bull dis prev res inst kyoto univ 33 part 2 no 298 63 104 irikura k 1986 prediction of strong acceleration motions using empirical green s function in proceedings of the 7th japan earthquake engineering symposium 151 156 irikura k 1999 techniques for the simulation of strong ground motion and deterministic seismic hazard analysis in proceedings of the advanced study course seismotectonic and microzonation techniques in earthquake engineering integrated training in earthquake risk reduction practices kefallinia 453 554 is used to generate synthetic time series from recordings of smaller events with 4 mw 5 in order to estimate several parameters characterizing the so called strong motion generation area which is defined as an extended area with homogeneous slip and rise time and for crustal earthquakes corresponds to an asperity of about 100 bar stress release miyake h t iwata and k irikura 2003 source characterization for broadband ground motion simulation kinematic heterogeneous source model and strong motion generation area bull seism soc am 93 2531 2545 the parameters are obtained by acceleration envelope and displacement waveform inversion for the 2004 and 1986 events and msk intensity pattern inversion for the 1977 event using a genetic algorithm the strong motion recordings of the analyzed vrancea earthquakes as well as the msk intensity pattern of the 1977 earthquake can be well reproduced using relatively small strong motion generation areas which corresponds to small asperities with high stress drops 300 1200 bar and high particle velocities 3 5 m s these results imply a very efficient high frequency radiation which has to be taken into account for strong ground motion prediction and indicate that the intermediate depth vrancea earthquakes are inherently different from crustal events

a 2 d velocity model of the vrancea region in romania prediction of teleseismic waveforms summary in previous studies anomalies in arrival time and amplitudes of depth phases pp and sp recorded at teleseismic distances and produced by large intermediate depth events of the vrancea region were pointed out perrot et al 1994 the modelling of major recent events has shown that the presence of a dipping interface and thick low velocity sediment layer in the upper crust above the hypocentral area can explain such anomalies simulating broad band records of the 1990 may 31 earthquake it is shown that the 2 d crustal velocity model derived by perrot et al 1994 can also be used to explain observed waveforms in an extended azimuthal range from 105 to 243 and is valid for earthquakes having different hypocentral locations in the deep vrancea seismic zone using records in the azimuthal range where a classical spherical model produces a good fit to the observed waveforms the source is best modelled by two point sources at 90 and 93 km depth releasing the same amount of seismic moment and separated by 1 5 s in time synthetics calculated for this source time history and the 2 d velocity model above the source give a much improved fit of the observed waveforms over what could be achieved with a 1 d spherical model the results suggest that teleseismic waveforms could be reasonably well predicted for any event in the region with the 2 d velocity model which accounts for the main structural features in the upper crust of the vrancea region

on the thermal regime of some tectonic units in a continental collision environment in romania an analysis of the evolution of the main tectonic units in romania shows that the thermal regime of the lithosphere should be derived according on the one hand to the particular tectonic interactions the various tectonic units have been involved in and on the other hand to the investigated depth interval a steady state conduction model of the crustal temperature field based on the heat flow distribution and information on the structure is presented for the romanian territory it shows large lateral thermal variations between tectonic units as a result of different geological and thermal histories within the frame of a complex modelling of the thermal evolution of the lithosphere in the east carpathians as proposed in this study the zero order thermal effects of the pre miocene oceanic subduction of the eurasian plate are evaluated the deep thermal structure of the subducted slab is derived and shown to be compatible with the velocity structure of the lithosphere and the intermediate depth seismicity of the vrancea area

vrancea source influence on local seismic response in bucharest the mapping of the seismic ground motion in bucharest due to the strong vrancea earthquakes is carried out using a complex hybrid waveform modeling method that allows easy parametric tests starting from the actually available strong motion database we can make realistic predictions for the possible ground motion the basic information necessary for the modeling consists of a the representative mechanisms for the strong subcrustal events b the average regional structural model and c the local structure for bucharest two scenario earthquakes are considered and the source influence on the local response is analyzed in order to define generally valid ground motion parameters to be used in the seismic hazard estimations the source has its own detectable contribution on the ground motion and its effects on the local response in bucharest are quite stable on the transversal component t while the radial r and vertical v components are sensitive to the scenario earthquake although the strongest local effects affect the t component both observed and synthetic a complete determination of the seismic input for the built environment requires the knowledge of all three components of motion r v t the damage observed in bucharest for the march 4 1977 vrancea event the strongest earthquake to strike the city in modern times is in agreement with the synthetic signals and local response

high resolution teleseismic body wave tomography beneath se romania ii imaging of a slab detachment scenario summary non linear teleseismic bodywave tomography with data of the 1999 calixto field experiment carpathian arc lithosphere x tomography in romania provides high resolution imaging of the upper mantle structure in this paper we present the relative p wave velocity distribution of the lithosphere asthenosphere system smearing from strong crustal velocity anomalies into the upper mantle is successfully suppressed by traveltime corrections with an a priori 3 d regional crustal velocity model see martin et al 2005 herein referenced as paper 1 our high resolution image shows a high velocity body beneath vrancea and the moesian platform with a ne sw orientation between 70 and 200 km depth beneath 200 km a change in the orientation from ne sw to n s can be observed the body reaches a maximum depth of about 350 370 km the velocity perturbation is maximal between 110 and 150 km depth 5 2 5 8 per cent and almost constant for depths beneath 200 km 3 2 3 8 per cent as most authors of previous studies agree on miocene subduction along the arc followed by soft continental collision we interpret the high velocity body as the subducted yet not fully detached slab the ne part of the slab appears to be mechanically coupled to the moesian lithosphere and hosts the intermediate depth seismicity in contrast the aseismic sw part is interpreted as decoupled from the overlying lithosphere and torn off from the underlying lithospheric material beneath 200 km depth low velocity anomalies nw of the slab above 110 km depth are interpreted as a shallow asthenospheric upwelling further low velocity anomalies are in agreement with a lithosphere asthenosphere boundary at 110 150 km depth below the moesian platform and deeper than 200 km under the east european platform eep the tomographic images support models proposing slab rollback during subduction collision followed by slab steepening and lithospheric delamination the different degrees of mechanical coupling of the slab to the overlying lithosphere allow to understand the loci of seismicity as volumes of stress concentration independent on the specifics of data interpretation our high resolution image is a novel contribution to understand the process of ongoing lithospheric detachment associated with strong intermediate depth seismicity in se romania

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

a gis based study of earthquake hazard as a tool for the microzonation of bucharest abstract bucharest the capital of romania is situated close to one of the most seismically active areas in europe the vrancea region in the eastern carpathians the necessity of a well documented microzonation of the city and its immediate surroundings is clearly evident due to this seismic risk in the absence of a sufficient dense network of ground motion recording stations in bucharest the only possible way to realise a comprehensive microzonation is to correlate detailed subsurface geological data at instrumented sites with the macroseismic intensities and to extrapolate the results to non instrumented areas in this regards the geology of bucharest is relatively well known based on a great number of geotechnical drillings about 1200 for the first time a digital geological model dgm of the subsurface of bucharest was obtained based on the integration of numerous borehole data with a geographic information system gis transfer functions and dynamic ground responses were calculated with the linear modelling software proshake using soil profiles taken from discrete locations in the developed model and shear wave velocities and densities characteristic for each quaternary unit the distribution of computed spectral amplifications and spectral accelerations were generated for the ground surface of bucharest by interpolation important insights were made concerning the primary geological influencing factors on the observed historical damages to buildings which resulted from earthquakes through statistical regression analyses between various geotechnical properties and parameters associated with the historical damages

effect of rainfall intensity slope and antecedent moisture content on sediment concentration and sediment enrichment ratio abstract the transportability of sediment by runoff and its potential for subsequent deposition is dependent on the size and distribution of the transported material and the sediment concentration the size distribution of the eroded sediment is also expected to vary depending on which erosion process is predominant this study discusses the results of laboratory analysis to evaluate the effect of rainfall intensity slope steepness soil types and antecedent moisture content on sediment concentration runoff coefficients and sediment enrichment ratios to achieve the objectives laboratory experiments were conducted using fel 3 rainfall simulator and erosion pan rainfall intensity of 120 70 and 55 mm h was applied sequentially at 9 25 and 45 slope for three soil types found in alemaya watershed eastern ethiopia alemaya black soil soil a regosols soil b and cambisols soil c varied from clay to sandy clay loam in texture with wet and dry antecedent moisture contents the rate of sediment concentration significantly varied with moisture contents for soil a sediment concentrations 24 3 g l from an initially air dry surface and 18 7 g l from an initially wet surface were observed wetting decreased sediment concentration of soil a b and c by 23 45 7 and 1 3 respectively sediment concentration didn t show any trend with rainfall intensities for soil b the highest average silt enrichment ratio of 2 15 was observed followed by average clay enrichment ratio of 1 61 for soil a and soil c average clay enrichment ratios of 1 13 and 1 91 were observed respectively initial moisture contents had effect on the enrichment ratio however the actual effect varied with soil type and the size of the particle results of the study indicated that the actual effect of slope as well as rainfall intensity on sediment concentration and sediment yield vary with soil types and moisture contents

relative seismic moment tensor determination for vrancea intermediate depth earthquakes the method of relative seismic moment tensor determination proposed bystrelitz 1980 is extended a from an interactive time domain analysis to an automated frequency domain procedure and b from an analysis of subevents of complex deep focus earthquakes to the study of individual source mechanism of small events recorded at few stations

quantitative modeling of the lithosphere dynamics earthquakes and seismic hazard abstract understanding of lithosphere dynamics tectonic stress localization earthquake occurrences and seismic hazards has significantly advanced during the last decades meanwhile despite the major advancements in geophysical sciences yet we do not see a decline in earthquake disaster impacts and losses although earthquake disasters are mainly associated with significant vulnerability of society comprehensive seismic hazards assessments and earthquake forecasting could contribute to preventive measures aimed to reduce impacts of earthquakes modeling of lithosphere dynamics and earthquake simulations coupled with a seismic hazard analysis can provide a better assessment of potential ground shaking due to earthquakes here we present a block and fault dynamics bafd model which simulates earthquakes due to lithosphere dynamics and allows for studying the influence of fault network properties and regional movements on seismic patterns the model s performance is analyzed in terms of reproduction of basic features of the observed seismicity such as the frequency magnitude relationship clustering of earthquakes occurrences of large events fault slip rates and earthquake mechanisms several studies related to the application of the bafd model to the following earthquake prone regions are reviewed the southeastern carpathians caucasus the western india tibet himalaya and the sunda arc we examine then a new approach to seismic hazard analysis which is based on instrumentally recorded historical and bafd simulated earthquakes and analyze how earthquake modeling can assist in hazard assessment finally we discuss perspectives in modeling of earthquake occurrences and improvements in hazard assessment

thermo mechanical controls on the mode of continental collision in the se carpathians romania abstract the carpathians orogenic system with its along arc variations in topography developed in the aftermath of continental collision is associated with unusual foredeep basins large scale strain and seismicity concentration and high velocity mantle bodies the east carpathians continental collision was non cylindrical leading to large scale variations in thrust nappe kinematics orogenic uplift patterns and foredeep subsidence controlled by the mechanics and geometry of the lower plate thermo mechanical modelling demonstrates that in this low rate convergence regime the subducted lithosphere had enough time to interact with the mantle to advance towards a thermal resettlement this is favored by the low degree of metamorphism mechanical weakness of the lower plate and the lack of active surface processes at the contact with and in the upper plate in contrast low buoyant thick lower crust and active surface processes keep the continuity of the slab intact and promote the development of typical foredeep basins the model explains in a self consistent manner the unusual geometry of the vrancea seismogenic slab in the bend zone of the romanian carpathians the model is also consistent with the presence of two high velocity bodies inferred from seismic tomography studies and explains the depth zonation of seismicity in the vrancea area differences between the northern part of east carpathians and the southeastern bend of the carpathians arc are largely controlled by lateral variations in crustal structure topography emplacement and surface processes along the arc mechanical heterogeneity of the carpathians subduction leads to the development of two end member modes of collision allowing a study of these states and their transition lithospheric configuration and tectonic topography appear to be prime factors controlling variations in slab behavior in the se carpathians at the terminal phase of continental convergence slab delamination roll back and depocenter migration appear to play a more limited role at shallow and lithospheric levels

integrated transnational macroseismic data set for the strongest earthquakes of vrancea romania abstract a unique macroseismic data set for the strongest earthquakes occurring since 1940 in the vrancea region is constructed by a thorough review of all available sources inconsistencies and errors in the reported data and in their use are also analysed the final data set which is free from inconsistencies including those at the political borders contains 9822 observations for the strong intermediate depth earthquakes 1940 mw 7 7 1977 mw 7 4 1986 mw 7 1 1990 may 30 mw 6 9 1990 may 31 mw 6 4 and 2004 mw 6 0 this data set is available electronically as supplementary data to the present paper from the discrete macroseismic data the continuous macroseismic field is generated using the methodology developed by molchan et al 2002 the procedure along with the unconventional smoothing method modified polynomial filtering mpf uses the diffuse boundary db method which visualises the uncertainty in the isoseismal boundaries the comparison of dbs with previous isoseismal maps supplies a good evaluation criterion of the reliability of earlier published maps the produced isoseismals can be used not only for the formal comparison of the observed and theoretical isoseismals but also for the retrieval of source properties and the assessment of local responses molchan et al 2011

kinematic evolution of the romanian carpathians abstract the regional pattern of contraction and extension directions and the evolution of the strain field from paleogene to neogene times enabled a reconstruction of the migration path of the carpathian collision front the carpathian nappes were thrust around the moesian plate during paleogene and early neogene times and protruded into a small oceanic embayment between the moesian and european plates the arc structure of the carpathian fold thrust belt was formed in late neogene times as a result of the eastward escaping tisza dacia block due to n directed convergence of the adriatic plate and the retreating subduction of an oceanic slab brittle deformation structures in the romanian carpathians suggest three tectonic events related to major plate motions 1 paleogene to middle miocene ne to ene contraction caused right lateral curved strike slip faults 2 middle miocene to pliocene fan shaped orientations of contraction directions were caused by right lateral oblique convergence in the southern carpathians frontal convergence in the southern eastern carpathians and left lateral convergence in the northern eastern carpathians 3 pleistocene to holocene general e w extension and n s contraction in the carpathian arc and local ese wnw contraction in the vrancea area is related to the late roll back stage and break off of the subducted slab in the bend area

the vrancea seismic zone and its analogue in the banda arc eastern indonesia abstract it is now widely although not universally accepted that the carpathian orogen marks the site of an arc continent collision that followed the subduction of a now vanished small ocean basin seismic tomography has defined a high velocity anomaly in the upper mantle similar to those associated with subduction zones worldwide there is however no recognisable wadati benioff zone wbz and intermediate depth seismicity is confined to a relatively small roughly cylindrical and vertically elongated region beneath the extreme southeastern corner of the mountain chain there is no consensus in the published studies as to the origin of this vrancea zone the banda sea region of eastern indonesia has sometimes been cited as an analogue for the pannonian transylvanian basin and the enclosing carpathian orocline but at first sight the patterns of seismicity appear very different intermediate depth seismic activity defines a subducted slab that dips north south and west beneath the banda sea a configuration explained as a consequence of the rapid expansion of the sea during roll back subduction if the similar scenario proposed for the carpathians is correct then it is the absence of a carpathian wbz that is actually anomalous closer examination of banda arc seismicity shows that it can be divided into two parts these being a scoop shaped wbz and an adjacent damar zone of much more intense intermediate depth activity at its eastern end the damar zone merges with the wbz but in the west there is evidence for separation from it a plausible explanation of this pattern is that a lower layer of the downgoing slab is peeling away from the remainder the banda australia collision is now almost complete and the activity in the wbz proper can be expected to decrease damar zone activity on the other hand may persist for a much longer period migrating towards the foreland as the detaching layer separates from the remainder of the subducted lithosphere in a few million years the seismicity of the banda region could well resemble the present day seismicity of the carpathian orogen

a statistical procedure for the analysis of seismotectonically induced hydrochemical signals a case study from the eastern carpathians romania changes in the stress field of an aquifer system induced by seismotectonic activity may change the mixing ratio of groundwaters with different compositions in a well leading to hydrochemical signals which in principle could be related to discrete earthquake events due to the complexity of the interactions and the multitude of involved factors the identification of such relationships is a difficult task in this study we present an empiric statistical approach suitable to analyse if there is an interdependency between changes in the chemical composition of monitoring wells and the regional seismotectonic activity of a considered area to allow a rigorous comparison with hydrochemistry the regional earthquake time series was aggregated into an univariate time series this was realized by expressing each earthquake in form of a parameter beq taking into consideration both energetic magnitude of a seismic event and spatial parameters position of epi hypocentrum relative to the monitoring site the earthquake and the hydrochemical time series were synchronised aggregating the e parameters into bearthquake activityq functions e which takes into account the time of sampling relative to the earthquakes which occurred in the considered area for the definition of the aggregation functions a variety of different beq parameters were considered the set of earthquake functions e was grouped by means of factor analysis to select a limited number of significant and representative earthquake functions e to be used further on in the relation analysis with the multivariate hydrochemical data set from the hydrochemical data a restricted number of hydrochemical factors were extracted factor scores allow to represent and analyse the variation of the hydrochemical factors as a function of time finally regression analysis was used to detect those hydrochemical factors which significantly correlate with the aggregated earthquake functions this methodological approach was tested with a hydrochemical data set collected from a deep well monitored for two years in the seismically active vrancea region romania three of the hydrochemical factors were found to correlate significantly with

variable rupture mode of the subduction zone along the ecuador colombia coast three large earthquakes occurred within the rupture zone of the 1906 colombia ecuador earthquake m w 8 8 in 1942 m s 7 9 1958 ms 7 8 and 1979 m s 7 7 we compared the size and mechanism of these earthquakes by using long period surface waves tsunami data and macroseismic data the 1979 event is a thrust event with a seismic moment of 2 9 10 28 dyne cm and represents subduction of the nazca plate beneath south america the rupture length and direction are 230 km and n40 e respectively examination of old seismograms indicates that the 1906 event is also a thrust event which ruptured in the northeast direction the seismic moment estimated from the tsunami data and the size of the rupture zone is 2 10 29 dyne cm the 1942 and 1958 events are much smaller about 1 5 to 1 10 of the 1979 event in the seismic moment than the 1979 event we conclude that the sum of the seismic moments of the 1942 1958 and 1979 events is only formula of that of the 1906 event despite the fact that the sequence of the 1942 1958 and 1979 events ruptured approximately the same segment as the 1906 event this difference could be explained by an asperity model in which the fault zone is held by a discrete distribution of asperities with weak zones in between the weak zone normally behaves aseismically but slips abruptly only when it is driven by failure of the asperities a small earthquake represents failure of one asperity and the rupture zone is pinned at both ends by adjacent asperities so that the effective width and the amount of slip are relatively small a great earthquake represents failure of more than one asperity and consequently involves much larger width and slip

modelling the coupling between salt kinematics and subsidence evolution inferences for the miocene evolution of the transylvanian basin large scale diapiric salt movements affect the architecture of sedimentary basins and often prevent the understanding of their mechanics by hiding or distorting subsidence patterns one good example is the evolution of the transylvanian basin which formed during miocene times in an area located in between the rapid slab rollback and continental collision recorded at the exterior of the carpathians and the extension of the neighbouring pannonian basin in the absence of major genetic fault systems quantifying these external tectonic forcing factors requires an accurate reconstruction of subsidence evolution having the advent of a detailed 3d geometrical model of the transylvanian basin we apply a 3d numerical modelling technique that couples salt re distribution and subsidence evolution to quantify and understand the basin kinematics and vertical motions two techniques backward and forward modelling are coupled in order to discriminate between salt migration driven by overburden and the influence of external tectonic forcing factors the results show that salt kinematics was more complex than simple unidirectional migration suggesting the existence of areas with significant subsidence hidden by the inward salt migration and areas with apparent large subsidence that are in reality artefacts of outwards salt migration additionally the results suggest that parts of the basin have been successively affected by in and out ward salt migration events an effect of localising subsidence and overburden furthermore accelerated moments of salt migration took place during the main miocene contraction events recorded at the exterior of the carpathians demonstrating that salt migration is enhanced by intraplate stresses our study also infers that the subsidence of the transylvanian basin is the result of the superposition of the contraction at the exterior of the orogenic chain and the back arc extension

a note on the depth recurrence and strain release of large vrancea earthquakes the large 1940 vrancea event with body wave magnitude mb 7 3 was investigated in terms of the depth of rupture initiation and extent it was found that the rupture started at 150 km depth and propagated downwards the ruptured zones of the 1977 1986 and 1990 vrancea events were estimated from the distribution of aftershocks located with the joint hypocentre determination method their depth ranges are 90 110 km 130 150 km and 70 90 km respectively because the body wave magnitudes mb were saturated for the last three events and the surface wave magnitudes ms were underestimated not being corrected for depth we chose the moment magnitudes to quantify the four events 7 7 1940 7 4 1977 7 1 1986 and 6 9 1990 respectively the depth interval 110 130 km is found to be unbroken since at least 1838 or 1802 and therefore is expected to accommodate the next large moment release mw 7 0 to 7 4 the strain in the vertical and in the se nw directions is about 0 0003 giving a moderate strain rate of about 10 13 s 1 a correlation between the depth interval of the large events and the year of occurrence in a century is suggested offering a physical basis to the observed quasi cyclicity

an improved approach for evaluating the time dependent stability of colluvial landslides during intense rainfall the paper presents an improved analytical approach for evaluating the time dependent stability of colluvial landslides during intense rainfall infiltration the approach comprises two steps first to simulate rainfall infiltration and then to compute the safety factor in terms of the irregularity of the natural landslide surface in implementation of the method the landslide is divided into several soil slices with approximately straight sides each single slice is regarded as a finite slope so that the infiltration formula and safety factor can be deduced the infiltration formula is derived with combination of the green ampt model and mass conservation law considering seepage perpendicular and parallel to slope surface simultaneously in the modified infiltration model both size effect and angle effect are vividly observed in the process of rainfall infiltration into the finite slope while the former of which is not presented in the original green ampt model the safety factor is computed using the limit equilibrium method with the influence of infiltrating water on the shear strength gravity and seepage force of soil slices considered by case study of the shuping landslide in three gorges decline in the safety factor and the decrease in the tendency are definite specifically under the rainfall intensity of 50 mm h the failure of shuping landslide is most likely to occur at the time of 102 h in addition the results highlight shallow failure along the wetting front under intense rainfall

s wave attenuation characteristics beneath the vrancea region in romania new insights from the inversion of ground motion spectra the s wave attenuation characteristics beneath the vrancea region in romania are analyzed from the spectra frequency range 0 5 20 hz of more than 850 recordings at 43 accelerometric stations of 55 intermediate depth earthquakes m 4 0 7 1 that occurred in the vrancea seismogenic zone the method commonly chosen for this type of investigation in the case of crustal earthquakes is the generalized inversion technique git e g andrews 1986 castro et al 1990 yet the vrancea dataset is entirely different from common crustal datasets because of the strong clustering of the hypocenters within a very small focal volume there are only few crossing ray paths from sources to receivers as a consequence inhomogeneities in the attenuation properties are not averaged out which leads to unphysical results if the standard git approach is adopted the problem is discussed qualitatively by performing tests with synthetic data and solved quantitatively by adapting the git technique in view of these peculiarities with the optimally adapted inversion scheme it is possible to unravel differences in the attenuation characteristics between two or more sets of stations the results show that the attenuation of seismic waves is roughly comparable in the low frequency range 4 5 hz but stronger by up to an order of magnitude at higher frequencies within the carpathian mountain arc as compared with the foreland area modeling this strongly frequency dependent lateral variation of seismic attenuation by a significantly lower q beneath vrancea 1 provides a very good fit of observed strong motion characteristics 2 sheds new light on the distribution of intensities of the previous strong earthquakes 3 will have strong implications for future hazard assessment and 4 is fully compatible with structural models from deep seismic sounding tomography and teleseismic attenuation

revised crustal architecture of the southeastern carpathian foreland from active and passive seismic data 1 integration of active and passive source seismic data is employed in order to study the nature of the relationships between crustal seismicity and geologic structures in the southeastern se carpathian foreland of romania and the possible connection with the vrancea seismogenic zone vsz of intermediate depth seismicity one of the most active earthquake prone areas in europe crustal epicenters and focal mechanisms are correlated with four deep industry seismic profiles the reprocessed danube and carpathian integrated action on process in the lithosphere and neotectonics dacia plan profile and the deep reflection acquisition constraining unusual lithospheric activity ii and iii dracula profiles in order to understand the link between neotectonic foreland deformation and vrancea mantle seismicity projection of crustal foreland hypocenters onto deep seismic profiles identifies several active crustal faults in the se carpathian foreland and suggests a mechanical coupling between the mantle located vsz and the overlying foreland crust the coupled associated deformation appears to take place on the trotus fault the sinaia fault and the newly detected ialomita fault seismic reflection imaging reveals the absence of west dipping reflectors in the crystalline crust and a slightly east dipping to horizontal moho in the proximity of the vrancea area these findings argue against previously purported mechanisms to generate mantle seismicity in the vsz including oceanic lithosphere subduction in place and oceanic slab break off furthermore suggesting that the vrancea seismogenic body is undetached from the overlying crust in the foreland

numerical modelling of earthquake flow in the southeastern carpathians vrancea effect of a sinking slab abstract the earthquake prone vrancea region is modelled as a system of perfectly rigid blocks separated by infinitely thin plane faults the interaction of the blocks along the fault planes and with the surrounding medium is assumed to be a viscous elastic the displacements of the block system are caused by motions of boundary blocks the velocities of the motions are found from a model of mantle flows induced by a sinking slab beneath the vrancea region when a ratio of stress to pressure for some portion of a fault plane exceeds a certain strength level a stress drop earthquake occurs as a result of the numerical simulation a catalog of synthetic earthquakes is produced several numerical experiments for various model parameters show that the spatial distribution of synthetic events is significantly sensitive to the directions of the block movements small variations in a slab rotation control the pattern of the synthetic seismicity the results of the analysis show that the catalogs obtained by the simulation of the block structure dynamics have certain features similar to those of the real earthquake catalog of the vrancea region

thermal evolution and geometry of the descending lithosphere beneath the se carpathians an insight from the past abstract mantle heterogeneities imaged by seismic tomography in the se carpathians contain information on the present thermal state of the mantle based on p wave seismic velocity anomalies we develop a model of the present mantle temperature beneath the region and combine the model with a model of crustal temperature constrained by heat flow data the modeled temperatures are assimilated into the geological past using the information on the regional movement in the early and middle miocene prominent thermal states of the lithospheric slab descending in the region are restored from its diffuse present state in miocene times the slab geometry clearly shows two portions of the sinking body the northwest southeast oriented portion of the body is located in the vicinity of the boundary between the east european and scythian platforms and this portion of the sinking body may be a relic of cold lithosphere that has traveled eastward another portion has a northeast southwest orientation and is related to the present descending slab above a depth of 60 km the slab had a concave thermal shape confirming the curvature of the carpathian arc and a convex surface below that depth the slab maintained its convex shape until it split into two parts at a depth of about 220 km we propose that this change in the slab geometry which is likely to be preserved until the present can cause stress localization due to the slab bending and subsequent stress release resulting in large mantle earthquakes in the region also we hypothesize that either the processes of dehydration and partial melting of the descending lithospheric slab or dragging down of hotter rocks from the adjacent uppermost mantle by the slab are possible causes of the reduction in seismic velocities beneath the transylvanian basin

source side shear wave splitting and upper mantle flow in the romanian carpathians and surroundings we present shear wave splitting measurements from 5 earthquakes that occurred in the vrancea seismic zone of the carpathian arc s waves from these events all with magnitudes 5 4 mw and deeper than 88 km were recorded at broadband stations of the global seismic network and the geoscope and geofon networks and used by us to measure shear wave splitting corrected for sub station splitting and anisotropy in order to carry out these corrections we used published shear wave splitting parameters thus isolating contributions to observed splitting from the vrancea source region and upper mantle surrounding the carpathian arc the resulting 32 good observations of source side shear wave splitting along with 54 null splitting observations which yield two potential splitting directions clearly show that upper mantle anisotropy is strongly variable in the region of the tightly curved carpathian arc shear waves taking off from vrancea along paths that sample the east and southern carpathians have fast anisotropy axes parallel to these ranges whereas those leaving the source region to traverse the upper mantle beneath the transylvanian basin i e mantle wedge side trend ne sw shear waves sampling the east european and scythian platforms are separable into two groups one characterized by fast shear trends to the ne sw and a second deeper group with trends to nw se also the majority of null splits occur along paths leaving vrancea in these ne e azimuths we interpret these results to indicate the presence of at least three distinct upper mantle volumes in the carpathians region the upper mantle beneath the carpathian arc is strongly anisotropic with fabrics parallel to the local arc strike the transylvanian basin upper mantle fabrics trend ne sw and the anisotropy beneath the westernmost east european platform may be characterized by a shallow nw se trending fabric concentrated in the cratonic lithosphere of the east european platform and a second deeper fabric with e w trend marking asthenospheric flow beneath the craton s base this more complex anisotropy beneath the western edge of the east european platform would account for both the variability of observed splitting of waves that sample this volume and also the strong prevalence of nulls observed along eastward departing azimuths

some source and medium properties of the vrancea seismic region romania abstract simple spectral theory of seismic sources was used to determine source parameters directly related to medium properties stress drop seismic efficiency and fracture energy and quality factors of the vrancea romania seismic region the results show an increase in maximum static stress drop maximum seismic efficiency and fracture energy with depth the seismic efficiency is magnitude independent but the stress drop is magnitude independent only for events with ml 3 8 below this value the logarithm of stress drop increases quasi linearly with magnitude in the depth interval 50 160 km the stress drop increases with a slope of about 2 3 bar km the fracture energy per unit area of the fault has values of the order of 105 108 erg cm2 the frequency independent quality factors indicate that the attenuation of p waves is generally higher than that of s waves and that qp values are in agreement with recent tectonic models for the vrancea region total decoupling of the slab now sinking gravitationally is present only in the southwestern part of the vrancea region as suggested by the spatial position of intermediate depth hypocenters

the crustal structure beneath se romania from teleseismic receiver functions summary due to vigorous neogene geodynamic processes including oceanic subduction slab break off and mountain building in the carpathian arc the architecture of the lithosphere in romania is quite complicated to improve the knowledge about the lithosphere asthenosphere system in this region the passive seismological calixto99 experiment was conducted in 1999 in the se part of romania here we present crustal models derived from the analysis of teleseismic recordings with the receiver function rf method of the 120 temporarily installed stations and of the permanent geofon stations mlr and tirr the rf results extend the known crustal models which are based mainly on seismic refraction work and analysis of regional earthquakes we apply a grid search inversion at 30 stations and use two different error estimation methods to determine the moho depth and the average crustal vp vs ratio the complex 3 d intracrustal structure especially the deep sedimentary basins distorts significantly the rf waveforms within the whole station network this leads to ambiguous results at some stations our model of the moho depth has a maximum crustal thickness in the se carpathian mountains at station mlr with a depth of about 45 km and an average crustal vp vs ratio of 1 79 the surrounding crust in se romania has a thickness of mainly 35 40 km the rfs at mlr are characterized by clear azimuthal effects that can be correlated with the variation of the sediment thickness in the foredeep of the carpathian mountains a rf waveform inversion verifies these results and gains improved 1 d s wave velocity models at several stations in se romania

tectonic significance of changes in post subduction pliocene quaternary magmatism in the south east part of the carpathian pannonian region the south eastern part of the carpathian pannonian region records the cessation of convergence between the european platform moesia and the tisza dacia microplate plio quaternary magmatic activity in this area in close proximity to the vrancea zone shows a shift from normal calc alkaline to much more diverse compositions adakite like calc alkaline k alkalic mafic na alkalic and ultrapotassic suggesting a significant change in geodynamic processes at approximately 3 ma we review the tectonic setting timing petrology and geochemistry of the post collisional volcanism to constrain the role of orogenic building processes such as subduction or collision on melt production and migration the calc alkaline volcanism 5 3 3 9 ma marks the end of normal subduction related magmatism along the post collisional c limani gurghiu harghita volcanic chain in front of the european convergent plate margin at ca 3 ma in south harghita magma compositions changed to adakite like calc alkaline and continued until recent times 0 03 ma interrupted at 1 6 1 2 ma by generation of na and k alkalic magmas signifying changes in the source and melting mechanism we attribute the changes in magma composition in front of the moesian platform to two main geodynamic events 1 slab pull and steepening with opening of a tear window adakite like calc alkaline magmas and 2 renewed contraction associated with deep mantle processes such as slab steepening during post collisional times na and k alkalic magmas contemporaneous post collisional volcanism at the eastern edge of the pannonian basin at 2 6 1 3 ma was dominated by na alkalic and ultrapotassic magmas suggesting a close relationship with thermal asthenospheric doming and strain partitioning related to the adriatic indentation similar timing magma chamber processes and volume for k alkalic shoshonitic magmas in the south apuseni mountains 1 6 ma and south harghita area at a distance of ca 200 km imply a regional connection with the inversion tectonics

discussion of origins of hinterland basins to the rif betic cordillera and carpathians abstract the hinterland basins of the rif betic cordillera western alboran sea and the carpathians pannonian basin are in part composed of a thick in excess of 3 4 km thermal sag basin sequence the underlying crust has been thinned to 25 km in parts of the pannonian basin and to 15 km in parts of the alboran sea modern tectonic models for these areas envision tectonic collision and thickening of the crust followed by crustal thinning either by gravitational collapse back arc extension or a combination of the two contemporaneous with thrusting basin and range type extension has been envisioned for parts of these extensional collapse systems extensional features are common and they interact in a complex way with strike slip systems flexural cantilever modelling agrees with earlier mckenzie type pure shear modelling of the extensional systems in suggesting that extension alone cannot generate sufficient thermal decay to explain the great thickness of the sag basins associated with the alboran sea and pannonian basin consequently it is suggested that uplift of the asthenosphere accompanying subduction roll back is an important factor in the evolution of these basins roll back of the mantle lithosphere permits hot asthenospheric mantle to upwell and lie close to the base of the crust initially uplift and erosion of the crust overlying the asthenosphere occurs as the thermal perturbation cools the crust thermally subsides to produce a large sag basin

slab behaviour and its surface expression new insights from gravity modelling in the se carpathians abstract we use lithosphere scale gravity models to calculate gravity anomalies resulting from oceanic subduction continental collision slab steepening delamination and break off local isostasy was assumed for determining vertical movements caused by mass changes related to these tectonic processes our results show that subduction is accompanied by basin subsidence on the upper plate caused by the heavy lithospheric root of the subducting slab the basin evolution goes parallel with the slab evolution and shows considerable modifications when the processes at depth change slab steepening delamination break off characteristic gravity anomaly curves were acquired for the different tectonic scenarios these curves together with other data e g basin evolution on the upper and the lower plate were used for the reconstruction of the tectonic evolution of the se carpathians which includes tertiary subduction and collision followed by slab steepening and delamination

three dimensional numerical modeling of contemporary mantle flow and tectonic stress beneath the earthquake prone southeastern carpathians based on integrated analysis of seismic heat flow and gravity data the principal purpose of the study is to understand the interplay between intermediate depth large earthquakes in the southeastern carpathians vrancea and tectonic stress induced by a high velocity body lithospheric slab descending into the mantle beneath the region to analyze processes of stress generation and localization in and around the descending slab we develop a three dimensional 3d numerical model of contemporary mantle flow and stress beneath the vrancea region the input data of the model consist of i temperatures derived from seismic p wave velocity anomalies and surface heat flow ii crustal and uppermost mantle densities converted from p wave velocities obtained from seismic refraction studies iii geometry of the vrancea crust and slab from tomography and refraction seismic data and iv the estimated strain rate in the slab as a result of earthquakes to constrain the model viscosity we find that major crustal uplifts predicted by the model coincide with the east carpathian orogen and surround the transylvanian basin and that predicted areas of subsidence are associated with the moesian and east european platforms we show a correlation between the location of intermediate depth earthquakes and the predicted localization of maximum shear stress modeled tectonic stresses predict large horizontal compression at depths of about 70 220 km beneath the vrancea region which coincides with the stress regime defined from fault plane solutions for the intermediate depth earthquakes this implies that buoyancy driven descent of the lithospheric slab beneath the vrancea region is directly linked to intermediate depth seismicity 2004 elsevier b v all rights reserved

high resolution teleseismic body wave tomography beneath se romania i implications for three dimensional versus one dimensional crustal correction strategies with a new crustal velocity model summary the calixto carpathian arc lithosphere x tomography experiment offers a dense high quality data set to study the lithospheric asthenospheric system underneath se romania an earthquake prone region in se europe to increase the image resolution of structures in the uppermost mantle the application of crustal traveltime corrections by a priori information before the teleseismic traveltime inversion has become a well accepted procedure for such a correction we present a regional 3 d crustal seismic velocity model that serves as the basis for a high resolution teleseismic tomography forthcoming paper by martin et al our 3 d crustal model is based on recent research in the region we collect new results from two long range seismic refraction lines 3 d refraction tomography and teleseismic ps conversions adding previously published models of the sediment distribution conrad and moho depths as well as crustal seismic p wave velocities we compile a 3 d crustal model for se romania this 3 d model does not contain shallow small scale heterogeneities 10 km but it reflects the large scale structures such as variations in sediment thickness average seismic velocities and 3 d moho depth it is well suited for the correction of teleseismic traveltime residuals a prerequisite for a high resolution teleseismic tomography study for example traveltime delays of up to 1 3 s are caused by the almost 20 km thick layer of sediments in the focsani basin such delays are comparable to or larger in size than the expected upper mantle traveltime residuals we study the significance of 3 d crustal traveltime corrections relative to 1 d station corrections and show that the complex basin structures in se romania require a 3 d approach to reduce the smearing of crustal anomalies into the mantle by modelling synthetic mantle structures with a slab as it is expected for se romania we also investigate how to adapt the inversion strategy if crustal corrections are applied significant improvements are found by including the already corrected crustal layers in the inversion procedure thereby enabling the inversion algorithm to project still remaining uncertainties in the less resolved upper crustal layers however the fixing of the upper layers during the inversion due to the a priori knowledge of the crustal velocity anomalies clearly leads to smearing of uncorrected anomalies that are possibly located close to the crust mantle boundary

microzonation of bucharest state of the art the 1940 mw 7 7 and 1977 m w 7 4 vrancea earthquakes romania inflicted heavy damage and casualties in bucharest and the statistics indicate a recurrence interval of 25 years for m w 7 0 events under these circumstances the seismic microzonation represents important information for detailed urban planning that establishes an appropriate level of preparedness to the earthquake threat this paper reviews the main studies concerning the seismicity of the vrancea region the site conditions of the city the characterization of the building stock and the codes of practice that regulate the antiseismic design the first order microzonation of bucharest was performed starting from the existing database of structural and geotechnical parameters new insights originating from direct instrumental observation and interpretation of the local effects as well as realistic numerical modeling that update and improve the input data necessary for a detailed microzoning map of the city are also discussed

on the recurrence time of earthquakes insight from vrancea romania intermediate depth events summary the statistics of earthquake inter occurrence times in broad areas have been reported to obey universal scaling laws e g by bak et al and corral we investigate the recurrence times of intermediate depth vrancea earthquakes depth 60km taking advantage of the scarcity of aftershocks for deeper events we use a complete earthquake catalogue m 2 8 spanning from 1974 to 2002 the analysis of the probability density distribution of the recurrence times for the entire catalogue reveals a power law regime at small scales in order better to understand this scaling we also analyse declustered catalogues from which the distinct aftershock sequences following the 1977 1986 and 1990 major earthquakes have been removed and a time period without large events for these data sets the recurrence times follow an exponential distribution at all scales this observation suggests that deviations from the exponential model characteristic of the scaling laws recently proposed result primarily from short term aftershock clustering

near vertical seismic reflection image using a novel acquisition technique across the vrancea zone and foscani basin south eastern carpathians romania the dacia plan danube and carpathian integrated action on process in the lithosphere and neotectonics deep seismic sounding survey was performed in august september 2001 in south eastern romania at the same time as the regional deep refraction seismic survey vrancea 2001 the main goal of the experiment was to obtain new information on the deep structure of the external carpathians nappes and the architecture of tertiary quaternary basins developed within and adjacent to the seismically active vrancea zone including the focsani basin the seismic reflection line had a wnw ese orientation running from internal east carpathians units across the mountainous south eastern carpathians and the foreland focsani basin towards the danube delta there were 131 shot points along the profile with about 1 km spacing and data were recorded with stand alone reftek 125s also known as btexansq supplied by the university texas at el paso and the passcal institute the entire line was recorded in three deployments using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments the resulting deep seismic reflection stacks processed to 20 s along the entire profile and to 10 s in the eastern focsani basin are presented here the regional architecture of the latter interpreted in the context of abundant independent constraint from exploration seismic and subsurface data is well imaged image quality within and beneath the thrust belt is of much poorer quality nevertheless there is good evidence to suggest that a thick 10 km sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the focsani basin in the depth range 10 25 km most of the crustal depth seismicity observed in the vrancea zone as opposed to the more intense upper mantle seismicity appears to be associated with this sedimentary basin the sedimentary successions within this basin and other horizons visible further to the west beneath the carpathian nappes suggest that the geometry of the neogene and recent uplift observed in the vrancea zone likely coupled with contemporaneous rapid subsidence in the foreland is detached from deeper levels of the crust at about 10 km depth the moho lies at a depth of about 40 km along the profile its poor expression in the reflection stack being strengthened by independent estimates from the refraction data given the apparent thickness of the meta sedimentary supracrustal units the crystalline crust beneath this area is quite thin b20 km supporting the hypothesis that

seismic controls on contemporary sediment export in the siret river catchment romania abstract while differences in catchment sediment yield sy t km 2 y 1 are generally attributed to topography lithology climate and land use recent studies have highlighted that also seismic activity may have an important impact on sy nonetheless relatively little is known about the importance of this factor and the processes and mechanisms explaining its influence therefore this study explores the role of seismic activity in explaining spatial and temporal variation in sediment export within the siret basin romania 45 000 km 2 a catchment with a large variability in seismic activity based on previously unpublished long term 30 years sy measurements for 38 subcatchments of the siret we analyze the correlation between average sy seismic activity and various other catchment characteristics our results showed that spatial variation in average sy was indeed strongly correlated with the degree of seismic activity in each catchment r 2 0 74 also catchment lithology explained an important part of the differences in sy r 2 0 67 the combination of these two factors accounted for about 80 of the observed variation in sy while other factors e g topography land use climate and runoff did not significantly contribute to the explained variance in average sy to explore the impact of a specific earthquake event on sediment export we analyzed daily variations in suspended sediment concentrations of 10 subcatchments five years before and after an earthquake of mw 7 4 that affected the vrancea region in 1977 and triggered a substantial number of landslides only one catchment showed a clear 3 fold increase in sediment concentrations at unit discharge for the other nine catchments no consistent increase could be observed this indicates that the impact of seismic activity on average sy is mainly indirect and not associated with sudden pulses of sediments caused by earthquake triggered landslides potential mechanisms that could explain such indirect responses are discussed

rheology predictions across the western carpathians bohemian massif and the pannonian basin implications for tectonic scenarios on the basis of extrapolation of failure criteria lithology and temperature models we predict the rheology of the lithosphere for several sections through the carpathians and surrounding regions our models show significant lateral variations in rheology for the different tectonic units with important implications for the tectonic evolution the theologically strong lithosphere of the polish platform area contrasts with the weak lithosphere of the pannonian basin indicating that the arcuate shape of the carpathian orogen is primarily caused by an inherited curvature of an ancient embayment in the foreland with the pannonian units passively filling the space the polish platform and the moesian platform exhibit a similar rheological anisotropy caused by nw se trending weakness zones paralleling the tornquist teisseyre zone this anisotropy was the main controlling factor on the behavior of the lithosphere in this area since cadomian times as documented by the geological evolution of the sudety mountains and the mesozoic polish trough including the late cretaceous alpine inversion and the neogene development of the carpathian foreland this rheological anisotropy appears to have a major controlling impact on the development of at least the eastern part of the european lithosphere rheology predictions for the bohemian massif support the idea that the rigid lithosphere of the bohemian massif governed the bending of the alpine carpathian transition zone expressed in the large scale wrench movements opening the vienna basin in the foreland area detachment levels are predicted for upper and lower crustal levels leading to a decoupling of crustal and subcrustal flexure in most areas comparison with basin formation models indicates that our predictions for effective elastic thickness eet are similar to those derived from flexural models for the foreland area also eet predictions from extensional basin models in the pannonian region yield values close to our findings

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

large scale deformation in a locked collisional boundary interplay between subsidence and uplift intraplate stress and inherited lithospheric structure in the late stage of the se carpathians evolution 1 the interplay between slab dynamics and intraplate stresses in postcollisional times creates large near surface deformation particularly in highly bent orogens with significant lateral variations in mechanical properties this deformation is expressed through abnormal foredeep geometries and contrasting patterns of vertical movements intraplate folding is often the controlling mechanism particularly when the orogenic belt is locked the study of these tectonic processes in the se carpathians indicates a generalized subsidence period during latest miocene pliocene times driven by the slab pull and an intraplate folding due to an overall quaternary inversion the latter accommodates 5 km ese ward movement of this area with respect to the neighboring units which creates complicated three dimensional deformation patterns potentially driven at a larger scale by the interaction between the adriatic indentor and the entire carpathians system the lithospheric anisotropy inherited from the subduction times concentrates strain and induces large scale deformation far away from the active plate margins this anisotropy is dynamic because of deep mantle processes related to the subducted slab during postcollisional times such as thermal reequilibration or increase in slab dip

from nappe stacking to out of sequence postcollisional deformations cretaceous to quaternary exhumation history of the se carpathians assessed by low temperature thermochronology 1 apatite fission track aft and u th he ahe thermochronology have been combined to constrain the exhumation history of the se carpathians cooling ages generally decrease from cretaceous for the internal basement nappes aft ages to miocene quaternary aft and ahe respectively for the external sedimentary wedge the aft and ahe data show a paleogene age cluster which confirms a suspected but never demonstrated tectonic event the new data furthermore suggest that the se carpathians have been affected by a middle miocene exhumation phase related to continental collision which occurred at rates of 0 8 mm yr similar to the one previously inferred for the east carpathians the se carpathian tectonic evolution however is overprinted by two younger exhumation events in the pliocene pleistocene the first exhumation phase latest miocene early pliocene occurred at high exhumation rates 1 7 mm yr and is interpreted as a tectonic event and or associated with a sea level drop in the paratethys basins during the messinian low stand the youngest recorded tectonic phase suggests rapid pleistocene exhumation 1 6 mm yr and is interpreted to represent crustal scale shortening different in mechanics from collisional processes the data suggest that the se carpathians did not develop as a typical double vergent orogenic wedge instead exhumation was related to a foreland vergent sequence of nappe stacking during collision and was subsequently followed by a large out of sequence shortening event truncating the already locked collisional boundary

subduction in eastern indonesia how many slabs abstract seismicity associated with arc continent collision in eastern indonesia testifies to past north directed subduction of indian ocean lithosphere beneath the banda sea the complex patterns of deep seismicity have been cited as evidence for simultaneous south directed subduction at the northern margin of the sea but this interpretation has not been universally accepted recently available recomputations of hypocentre locations have provided increased resolution of eastern indonesian wadati benioff zones wbzs shallow to intermediate depth seismic activity around the banda arc appears to support models involving subduction of two separate and distinct lithospheric slabs but between 150 and 500 km the wbz has a continuous shoehorn shape this shape confirms the presence of subducted lithosphere beneath seram in the north as well as beneath timor in the south is incompatible with independent subduction of two unconnected plates and implies rapid eastwards retreat of the subduction trace across a now vanished northern spur of the indian ocean this roll back is unlikely to have been driven by local gravitational forces alone and may have been sustained by injection behind the banda slab of asthenospheric material escaping from the molucca sea arc arc collision

lithospheric gravitational instability beneath the southeast carpathians abstract the southeast corner of the carpathians known as the vrancea region is characterised by a cluster of strong seismicity to depths of about 200 km the peculiar features of this seismicity make it a region of high geophysical interest in this study we calculate the seismic strain rate tensors for the period 1967 2007 and describe the variation of strain rate with depth the observed results are compared with strain rates predicted by numerical experiments we explore a new dynamical model for this region based on the idea of viscous flow of the lithospheric mantle permitting the development of local continental mantle downwelling beneath vrancea due to a rayleigh taylor instability that has developed since the cessation of subduction at 11 ma the model simulations use a lagrangean frame 3d finite element algorithm solving the equations of conservation of mass and momentum for a spatially varying viscous creeping flow the finite deformation calculations of the gravitational instability of the continental lithosphere demonstrate that the rayleigh taylor mechanism can explain the present distribution of deformation within the downwelling lithosphere both in terms of stress localisation and amplitude of strain rates the spatial extent of the high stress zone that corresponds to the seismically active zone is realistically represented when we assume that viscosity decreases by at least an order of magnitude across the lithosphere the mantle downwelling is balanced by lithospheric thinning in an adjacent area which would correspond to the transylvanian basin crustal thickening is predicted above the downwelling structure and thinning beneath the basin

change in tropical cyclone activity during the break of the western north pacific summer monsoon in early august abstractthe modulation of tropical cyclone tc activity by the western north pacific wnp monsoon break is investigated by analyzing the subseasonal evolution of tcs and corresponding circulations based on 65 years of data from 1950 to 2014 the monsoon break has been identified as occurring over the wnp in early august the present results show that tc occurrence decreases increases remarkably to the east of the mariana islands southeast of japan during the monsoon break which is closely related to local anomalous midtropospheric downward upward motion and lower tropospheric anticyclonic cyclonic circulation in comparison with the previous and subsequent convective periods in late july and mid august these changes of tc activity and the corresponding circulation during the monsoon break are more significant in typical monsoon break years when the monsoon break phenomenon is predominant the reverse changes of tc activity to the east of the mariana islands and to the southeast of japan durin

source spectra and site response from s waves of intermediate depth vrancea romania earthquakes abstract seismograms from 55 intermediate depth vrancea earthquakes m 4 0 7 1 recorded at 43 stations of an accelerometric network in romania are used to derive source spectra and site amplification functions from s waves in the frequency range 0 5 20 hz with the generalized inversion technique git castro et al 1990 attenuation is taken into account using the nonparametric attenuation functions derived by oth et al 2008 from the same dataset and the attenuation corrected data are then split into source and site contributions the source spectra follow the 2 model brune 1970 1971 with high corner frequencies and a related brune stress drop of the order of 100 mpa the site amplification functions are separately determined for both horizontal and vertical components contrary to widespread expectation the vertical component shows significant amplification effects at high frequencies the h z ratios determined from the git results compare well with h v ratios computed directly from the s wave window of the accelerograms lermo and chavez garcia 1993 the basic assumption for the determination of site effects from h v ratios is that the vertical component is not or only little affected by site effects for vrancea earthquakes this assumption is incorrect consequently site effects should not be estimated from h v ratios the reason for this peculiar fact is the geometry of intermediate depth seismicity that leads to almost vertical ray paths beneath the stations

green ampt infiltration model for sloping surfaces 1 this work quantifies and explains the direct physical effects of slope angle on infiltration and runoff generation by extending the green ampt equation onto sloping surfaces a new extended solution using identical precipitation hydrographs was compared to the original formulation and then used to calculate the infiltration and runoff generation for different slope angles but for identical horizontal projection lengths homogeneous and isotropic soil is assumed and two different boundary conditions for vertical rainfall are studied ponded infiltration and infiltration under steady rainfall infiltration under unsteady rainfall was found to be similar to cases with steady rainfall both theoretical and numerical results show that infiltration increases with increasing slope angle for cases with ponded infiltration the slope effect was generally not significant for mild to moderate slopes but the slope effect became more important for low intensity and short duration rainfall events especially as it delayed the time for ponding it was also found that the cumulative vertical infiltration depth ihp at ponding or the initial loss increases with increasing slope angle the model was compared to richards equation on horizontal and sloping surfaces and found to perform well the model s applicability for nonuniform slopes was discussed and it was found that the model is generally applicable for isotropic and mildly anisotropic soils except for some small scale topographic elements finally the occurrence of nonvertical rainfall could increase runoff with increasing slope angle when rainfall deflects a large angle to upslope

seismic attenuation in the carpathian bend zone and surroundings we use measurements of crustal and upper mantle seismic attenuation in the southeastern carpathian arc and surroundings to test mantle responses to tethys closure in this region active seismicity at the carpathians vrancea bend zone can delimit lithosphere and asthenosphere distributions through attenuation observations at overlying seismic stations we measure frequency independent attenuation via an iterative spectral ratio method which compares p and s spectra for evolving time windows of both arrivals yielding 400 individual estimates of apparent differential qs and one composite measurement based on a normalized sum of the spectral ratios determined for the individual q estimates the procedure allows exclusion of subtle multipathed phases with attenuation different from that of the direct arrivals and yields a robust estimate of the measurement uncertainty measurements are retained for interpretation if the mean of the 400 individual q estimates and the composite spectra q estimate fall within the standard deviation of the 400 measurements results for 65 earthquakes recorded at the german romanian k2 accelerometer network during 1999 fall into clear groups attenuation is low high qs at stations east and north of the vrancea zone on the east european platform the scythian platform and in the eastern portion of the moesian platform inconsistent results at stations west of the intramoesian fault including those in and around bucharest probably reflect strong site effects at several locales attenuation at stations above and near the vrancea zone and at stations in the transylvanian basin is high low qs most likely due to the presence of hot shallow asthenosphere in these areas the technique we developed may ultimately yield a strong test of slab detachment and continental lithosphere delamination hypotheses put forth to explain the unusual seismicity and volcanism of the carpathian arc d 2005 elsevier b v all rights reserved

constraints from moho geometry and crustal thickness on the geodynamic origin of the vrancea seismogenic zone romania abstract reprocessing of industry deep seismic reflection data ramnicu sarat and braila profiles from the se carpathian foreland of romania provides important new constraints on geodynamic models for the origin of the intermediate depth vrancea seismogenic zone vsz mantle 70 200 km earthquakes of the vsz are characterized by high magnitudes greater than 6 5 frequent occurrence rates approximately 25 years and confinement in a very narrow 30 70 200 km 3 near vertical zone atypical for a wadati benioff plane located in front of the orogen these two deep 20 s seismic reflection profiles 70 km length across the foreland reveal 1 a high amplitude gently east dipping reflection across most of the section from what we interpret to be the moho at 15 s 40 42 km on the ramnicu sarat line to 16 s 47 48 km on the braila line 2 a thick sedimentary cover increasing in thickness from east 1 s 800 m to west 7 5 s 14 km 3 an eastward increase in crustal thickness from 38 km near vsz to 45 km 4 seismic and topographic evidence for a newly imaged possibly seismically active basement fault with a surface offset of 30 m observed on the ramnicu sarat line 5 a lack of notable west dipping structures in the crust and across the moho and 6 variable displacements on peceneaga camena fault of 5 km at moho and 200 m at the basement sedimentary cover contact these observations appear to argue against recent models for west dipping subduction of oceanic lithosphere at or in the vicinity of the vrancea seismogenic zone given the lack of west dipping fabrics in the lower crust and across the crust mantle boundary consequently one possible explanation for the geodynamic origin of vsz could be partial delamination of the continental lithosphere in an intra plate setting along a sub horizontal lithospheric interface in the carpathian hinterland that likely involves remnant lithospheric coupling between the crust and uppermost mantle in the foreland

improving depth resolution of teleseismic tomography by simultaneous inversion of teleseismic and global p wave traveltime data application to the vrancea region in southeastern europe summary over the years teleseismic tomography has developed to be a sophisticated method to study the earth s upper mantle on a regional scale using data from tomographic experiments with temporary station networks one faces some inherent problems which include limited resolution at depth and artefacts due to a plane wave approximation at the bottom of the model volume simultaneous inversion of dense regionally recorded teleseismic and global p wave traveltime data provides an opportunity to overcome these specific problems the calculation of the entire ray path using a 3 d ray tracing algorithm and a non linear iterative inversion scheme allow to localize heterogeneities in the earth s mantle and to improve resolution at depth application of a variable parametrization scheme provides not only a regional high resolution model but additionally allows to include a priori constrained structures such as a crustal model derived from independent studies we investigated the effect of different inversion strategies for a priori constrained model parameters and found that for upper mantle studies one must allow further perturbation of the known velocity structure during inversion to avoid artefacts down to the mantle transition zone we apply this approach to the romanian vrancea region in southeastern europe the results show a near vertical narrow high velocity body underneath that region extending down to 280 km depth approximately outlining the narrowly spaced seismogenic volume and a deeper differently oriented positive anomaly coupled to the shallower segment at the latter s southwestern edge at north northwest and west of the vrancea region we find an extended region of decreased seismic p wave velocity down to 200 km depth being interpreted as a shallow lithosphere asthenosphere boundary and asthenospheric mantle flow due to lateral migration of the high velocity body from synthetic reconstruction tests we found that inversion of the combined data set of regionally recorded teleseismic and global traveltime data enhances resolution up to depths greater than could be resolved by the teleseismic data alone

geodynamics and intermediate depth seismicity in vrancea the south eastern carpathians current state of the art abstract the vrancea region of the south eastern carpathians is a remarkable site of intra continental intermediate depth seismicity a large set of geological geophysical and geodetic observations has been accumulated for the last few decades and utilised to improve our knowledge of the shallow and deep structures beneath vrancea the crustal and mantle dynamics and the linkage between deep and surface processes in the region in this article we review geology and tectonics of the vrancea region including post collisional to recent deformations syn to post collisional magmatism and orogenic exhumation along the east and south carpathians the regional seismicity is analysed and the recent seismic studies including reflection refraction body and surface wave tomography are reviewed we discuss new geodetic measurements of horizontal and vertical movements in the region geoelectric studies density gravity and thermal modelling qualitative and quantitative including retrospective geodynamic models developed for vrancea are analysed the knowledge of regional tectonics geodynamics seismicity lithospheric deformation and stress regime in the vrancea earthquake prone region assists in an assessment of strong ground motion seismic hazard and risk the earthquake simulation seismic hazard and earthquake forecasting models have also been reviewed providing a link between deep geodynamic processes and their manifestation on the surface finally we discuss unresolved problems in vrancea in order to improve our understanding of the regional evolution present tectonics mantle dynamics intermediate depth seismicity and surface manifestations of the lithosphere dynamics and to enhance our ability to forecast strong earthquakes in the vrancea region the problems to be solved include i the origin of the high velocity body revealed by seismic tomography studies oceanic versus continental ii the lithospheric scale mechanism driving the miocene subsidence of the transylvania basin iii sub crustal structure between 40 and 70 km iv contemporary regional horizontal and vertical movements and v a comprehensive seismic hazard assessment in the region

can earth s rotation and tidal despinning drive plate tectonics abstract we re evaluate the possibility that earth s rotation contributes to plate tectonics on the basis of the following observations 1 plates move along a westerly polarized flow that forms an angle relative to the equator close to the revolution plane of the moon 2 plate boundaries are asymmetric being their geographic polarity the first order controlling parameter unlike recent analysis the slab dip is confirmed to be steeper along w directed subduction zones 3 the global seismicity depends on latitude and correlates with the decadal oscillations of the excess length of day lod 4 the earth s deceleration supplies energy to plate tectonics comparable to the computed budget dissipated by the deformation processes 5 the gutenberg richter law supports that the whole lithosphere is a self organized system in critical state i e a force is acting contemporaneously on all the plates and distributes the energy over the whole lithospheric shell a condition that can be satisfied by a force acting at the astronomical scale assuming an ultra low viscosity layer in the upper asthenosphere the horizontal component of the tidal oscillation and torque would be able to slowly shift the lithosphere relative to the mantle

the syn and post collisional evolution of the romanian carpathian foredeep new constraints from anisotropy of magnetic susceptibility and paleostress analyses abstract the first results of anisotropy of the magnetic susceptibility ams data from the romanian carpathian foredeep reveal compression directions generally perpendicular to the highly bended carpathian orogenic arc the distribution of the present day stress field in the pannonian carpathian region reflects pre imposed plate boundaries that were established during late miocene collision analysis of the ams along the eastern and southern carpathian foredeep at the contacts of the orogenic nappe pile the lower plate and the overlying sedimentary rocks indicates that two factors are critical for the distribution of the stress field during and after collision i e 1 the inherited highly bended plate geometry and 2 the quaternary deformation that lead to differential vertical and horizontal movements in the se carpathians the ams analysis was successfully used in the weakly deformed mio pliocene sedimentary rocks from the carpathian foredeep revealing information about the deformation history of the soft non competent rocks where the poor preservation of traditional kinematic indicators e g faults and folds is difficult

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

retrieval of reflections from ambient noise recorded in the mizil area romania we applied seismic interferometry si by crosscorrelation to ambient noise panels recorded in the mizil area romania aiming to retrieve body wave reflections to achieve this goal surface waves in the noise panels input to si should be suppressed we did this by selecting for input to si only noise panels that are not dominated by surface waves the selection was either after visual inspection in the time domain or after automatic slowness evaluation on crosscorrelated panels the latter used the slowness of arrivals passing through the virtual source position at time 0 s we discovered that the automatic slowness evaluation method allows better retrieval of reflections from the retrieved reflection gathers we obtained stacked images of the subsurface comparing the si images to a stacked image from active source data we concluded that some retrieved events correspond to reflectors in the active seismic section including known geologic markers in a previous application of si to ambient noise the retrieved reflections exhibited frequency content lower than that of active data in our results the frequency content of the si retrieved data was comparable to the one of the active data