amphibole as an archivist of magmatic crystallization conditions problems potential and implications for inferring magma storage prior to the paroxysmal 2010 eruption of mount merapi indonesia amphibole is widely employed to calculate crystallization temperature and pressure although its potential as a geobarometer has always been debated recently ridolfi et al contrib mineral petrol 160 45 66 2010 and ridolfi and renzulli contrib mineral petrol 163 877 895 2012 have presented calibrations for calculating temperature pressure fo2 melt h2o and melt major and minor oxide composition from amphibole with a large compositional range using their calibrations we have i calculated crystallization conditions for amphibole from eleven published experimental studies to examine the problems and the potential of the new calibrations and ii calculated crystallization conditions for amphibole from basaltic andesitic pyroclasts erupted during the paroxysmal 2010 eruption of mount merapi in java indonesia to infer pre eruptive conditions our comparison of experimental and calculated values shows that calculated crystallization temperatures are reasonable estimates calculated fo2 and melt sio2 content yields potentially useful estimates at moderately reduced to moderately oxidized conditions and intermediate to felsic melt compositions however calculated crystallization pressure and melt h2o content are untenable estimates that largely reflect compositional variation in the crystallizing magmas and crystallization temperature and not the calculated parameters amphibole from merapi s pyroclasts yields calculated conditions of 200 800 mpa 900 1 050 c nno 0 3 nno 1 1 3 7 7 2 wt melt h2o and 58 71 wt melt sio2 we interpret the variations in calculated temperature fo2 and melt sio2 content as reasonable estimates but conclude that the large calculated pressure variation for amphibole from merapi and many other arc volcanoes is evidence for thorough mixing of mafic to felsic magmas and not necessarily evidence for crystallization over a large depth range in contrast bimodal pressure estimates obtained for other arc magmas reflect amphibole crystallization from mafic and more evolved magmas respectively and should not necessarily be taken as evidence for crystallization in two reservoirs at variable depth

laboratory measurements of electrical conductivity of hydrous and dry silicic melts under pressure an interpretation of the electrical signature of molten rocks within the earth s interior in terms of nature and temperature conditions of magma requires additional laboratory data on the electrical conductivity of silicate melts this paper describes an experimental setup and presents measurements of the electrical impedance of dry and hydrous 1 3 wt h2o metaluminous obsidians determined in an internally heated pressure vessel in the range of 50 400 mpa and 350 1325 c it is shown that the temperature and pressure dependences of electrical conductivity of both hydrous and dry obsidian can be fitted by an arrhenius law applying in the melt and the glass regions this suggests that a similar transport mechanism operates in both melt and glass the determined activation energies are 70 kj mol for the dry obsidian and 65 and 61 kj mol for the 1 and 3 wt h2o melts respectively the activation volume is 20 cm3 mol combination of tracer diffusion and electrical conductivity reveals that sodium is the dominant charge carrier in the hydrous and dry obsidians the temperature and pressure effects on conductivity are therefore interpreted in terms of activation energy and activation volume for na mobility in dry and hydrous rhyolites an increase in conductivity associated with addition of water was observed and is shown to reflect the effect of water incorporation in melts on the mobility of sodium as a prospective it is anticipated that both the mobility and content of sodium could control the electrical conductivity of most terrestrial silicate melts magma under differentiation becomes more conductive due to sodium and water enrichment associated with fractional crystallization therefore its electrical signature must reveal its nature and maturity

a modified archie s law for two conducting phases abstract many types of mixing model are used widely within the earth sciences to determine the electrical properties of porous media consisting of solid and fluid phases of known conductivities volume fractions and distributions i e phase connectivities most models are valid for two or more conducting phases however of the simple models only archie s law includes a variable term the archie cementation exponent m that describes the connectivity of the phases unfortunately archie s law is only valid for one conducting phase distributed within a non conducting phase which makes it inapplicable in instances where the rock matrix has a significant conductivity such as for clay rich rocks and in calculations involving partial melting more complex models exist which account for multiple conducting phases and control over phase conductivity we have adapted the conventional archie s law to produce a simple modified archie s law that can be used with two conducting phases of any conductivity and any volume fraction while retaining the ability to model variable connectivities within those phases that result from variations in their distribution the modified model has two exponents m and p that describe the connectivity of each of the two phases the exponents are related through an equation that depends also on the volume fractions of the two phases the modified and the conventional versions of archie s law have been tested on a granular analogue porous medium with a conducting matrix and a pore space saturated with a range of saline fluids with different salinities and conductivities the new model describes the experimentally determined electrical behaviour of the system extremely well improving greatly on the conventional archie s law

impact of the gravity field and steady state ocean circulation explorer goce mission on ocean circulation estimates 2 volume and heat fluxes across hydrographic sections of unequally spaced stations 1 accurate geoids are expected to improve our knowledge of the dynamic sea surface height ssh as a mirror of the dynamic state of the oceans the dedicated gravity field and steady state ocean circulation explorer goce mission will lead to a highly accurate geoid model with a resolution of degree and order 200 we examine the impact of this mission on the assessment of large scale oceanic mass and heat transports via its expected error characteristics we do so applying a linear box inverse model and a nonlinear section inverse model to hydrographic data and to synthetic ssh data the results are compared to those obtained when substituting the error estimates of the gravity recovery and climate experiment grace mission and the present day earth gravitational model 1996 for the box inverse model we find an average reduction in transport uncertainties of about 9 for grace geoid error covariances and about 17 for goce over the hydrography only solution in both grace and goce these average percentage improvements are significantly increased when model error is excluded summarizing our results and those of the companion parts of this study we conclude that the grace mission reduces the marine geoid uncertainties such that altimetry may become useful for the study of the steady state ocean circulation the goce mission will improve the accuracy of the circulation estimates significantly on the large scales and introduce higher accuracy on shorter wavelengths as well furthermore it will enable us to study individual ocean currents

geochemistry and tectonic development of cenozoic magmatism in the carpathian pannonian region this review considers the magmatic processes in the carpathian pannonian region cpr from early miocene to recent times as well as the contemporaneous magmatism at its southern boundary in the dinaride and balkans regions this geodynamic system was controlled by the cretaceous to neogene subduction and collision of africa with eurasia especially by adria that generated the alps to the north the dinaride hellenide belt to the east and caused extrusion collision and inversion tectonics in the cpr this long lived subduction system supplied the mantle lithosphere with various subduction components the cpr contains magmatic rocks of highly diverse compositions calc alkaline k alkalic ultrapotassic and na alkalic all generated in response to complex post collisional tectonic processes these processes formed extensional basins in response to an interplay of compression and extension within two microplates alcapa and tisza dacia competition between the different tectonic processes at both local and regional scales caused variations in the associated magmatism mainly as a result of extension and differences in the rheological properties and composition of the lithosphere extension led to disintegration of the microplates that finally developed into two basin systems the pannonian and transylvanian basins the southern border of the cpr is edged by the adria microplate via sava and vardar zones that acted as regional transcurrent tectonic areas during miocene recent times major trace element and isotopic data of post early miocene magmatic rocks from the cpr suggest that subduction components were preserved in the lithospheric mantle after the cretaceous miocene subduction and were reactivated especially by extensional tectonic processes that allowed uprise of the asthenosphere changes in the composition of the mantle through time support geodynamic scenarios of post collision and extension processes linked to the evolution of the main blocks and their boundary relations weak lithospheric blocks i e alcapa and western tisza generated the pannonian basin and the adjacent styrian transdanubian and z rand basins which show high rates of vertical movement accompanied by a range of magmatic compositions strong lithospheric blocks i e dacia were only marginally deformed where strike slip faulting was associated with magmatism and extension at the boundary of adria and tisza dacia strike slip tectonics and core complex extension were associated with small volume miocene magmatism in narrow extensional sedimentary basins or granitoids in core complex detachment systems along older suture zones sava and vardar accommodating the extension in the pannonian basin and afterward pliocene quaternary inversion magmas of various compositions appear to have acted as lubricants in a range of tectonic processes

quantum magmatism magmatic compositional gaps generated by melt crystal dynamics compositional gaps are common in volcanic series worldwide the pervasive generation of compositional gaps influences the mechanical and thermal properties of the crust and holds clues on how our planet differentiates we have explored potential mechanisms to generate these gaps using numerical simulations coupling crystallization kinetics and multiphase fluid dynamics of magma reservoirs we show that gaps are inherent to crystal fractionation for all compositions as crystal liquid separation takes place most efficiently within a crystallinity window of 50 70 vol crystals the probability of melt extraction from a crystal residue in a cooling magma chamber is highest in this crystallinity window due to 1 enhanced melt segregation in the absence of chamber wide convection 2 buffering by latent heat of crystallization and 3 diminished chamber wall thermal gradients this mechanical control of igneous distillation is likely to have played a dominant role in the formation of the compositionally layered earth9s crust by allowing multiple and overlapping intrusive episodes of relatively discrete or quantized composition that become more silicic upward

calcic amphibole growth and compositions in calc alkaline magmas evidence from the motru dike swarm southern carpathians romania a late pan african calc alkaline dike swarm basalt andesite dacite rhyolite has been investigated in a region of over 2000 km 2 in the alpine danubian window south carpathians romania amphibole phenocrysts and microphenocrysts have been investigated by wavelength dispersive microprobe analysis and bse imaging the ca amphibole population represented in all the lithologies displays a large compositional range interpreted as the result of two processes 1 magmatic evolution kaersutite ti pargasite pargasite ti magnesiohastingsite magnesiohastingsite edenite tschermakite magnesiohornblende linked to magmatic differentiation from andesitic basalt to rhyolite and 2 deuteritic alteration of the primary amphibole related to late emplacement hydrothermal activity yielding numerous varieties comprising those cited above in all rock types amphibole phenocrysts equilibrated at a nearly constant pressure of about 0 6 0 1 gpa but their temperatures of crystallization ranged from 1000 900 c for basaltic andesites to 700 600 c for dacites in rhyolites edenite to magnesiohornblende crystals res ect a continuous range of p t conditions from 700 c 0 6 gpa to 600 c 0 1 gpa in agreement with their change of habit from euhedral to subhedral complex zonations in pargasite magnesiohastingsite including resorption are interpreted in term of self organization of

the yellowstone magmatic system from the mantle plume to the upper crust the yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world an understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk using a joint local and teleseismic earthquake p wave seismic inversion we revealed a basaltic lower crustal magma body that provides a magmatic link between the yellowstone mantle plume and the previously imaged upper crustal magma reservoir this lower crustal magma body has a volume of 46 000 cubic kilometers 4 5 times that of the upper crustal magma reservoir and contains a melt fraction of 2 these estimates are critical to understanding the evolution of bimodal basaltic rhyolitic volcanism explaining the magnitude of co2 discharge and constraining dynamic models of the magmatic system for volcanic 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

new seismic and tomography data in the southern part of the harghita mountains romania southeastern carpathians connection with recent volcanic activity the southern part of the southeastern carpathians represents the site of the most recent volcanic eruptions of the entire carpathian pannonian region the products of these eruptions range from 42 to 10 ka radiocarbon ages in the south harghita mountains high k calc alkaline rocks with adakite like features and at 1 2 0 6 ma k ar ages in the persani mountains alkali basalts they were emplaced in a post collisional regime ciomadul volcano is located at the southernmost part of the nw se oriented c limani gurghiu harghita range crossing the inner part of the southeastern carpathians and in the rough proximity of the vrancea seismic zone at ca 60 km toward nw its magma generation is attributed to geodynamic events closely related to the seismogenic area a number of particular geophysical and geochemical features located in the study region including 1 the abrupt attenuation of the seismic waves originating from the vrancea intermediate depth foci 2 the most intense heat flow anomaly in romania 3 the most prominent 3he 4he anomaly measured in natural postvolcanic gas emanations are all in favor of the hypothesis of a still existing hot local magma chamber data acquired during recent seismic monitoring of the vrancea zone and its neighborhoods suggest an enhancement of the local seismicity beneath the southern edge of the south harghita mts both at crustal and subcrustal levels at the same time recent tomography images obtained using local earthquake data correlate well with the presence of a vertically extended low velocity zone coming from the upper mantle to the assumed magmatic chambers located in the crust the present data supporting the presence of an active crustal magma chamber beneath ciomadul allow us to consider that future volcanic activity at this volcano cannot be discarded

electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition 1 the electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350 1018 c large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure the samples were analyzed by electron microprobe the relative proportions of the phases as a function of temperature were determined depending on temperature the phase assemblies included quenched silicate liquid plagioclase pyroxene fe ti oxides the crystal content varied from 0 to 80 wt in response to partial crystallization the residual liquid changed composition from basalt to andesite to dacite liquid the electrical conductivity of the partially crystallized basaltic samples was measured in addition above liquidus conductivity measurements were conducted on compositions matching the residual liquid at different temperature these supplemental electrical measurements allowed us to discriminate the effect of crystal content from the effect of changing liquid composition associated with partial crystallization combining with the modified archie s law a set of constraints describing the conductivity of the residual liquid versus chemical composition and temperature we propose an equation to calculate changes in conductivity associated with partial magma crystallization we showed how the composition of the residual liquid is critical on the electrical behavior of crystal liquid system the model overcomes the previous difficulties in finding a robust model for describing the electrical behavior of crystal liquid systems the effect of liquid composition on the electrical conductivity is related to diffusion mechanisms and transport properties in molten silicate combining known constraints on na tracer diffusion and our conductivity results confirms the statements that sodium is the dominant charge carrier silicate liquids from basalt to rhyolite these findings revealed that we need a comprehensive model that can predict the conductivity of molten silicate as a function of chemical composition

amphibole perspective to unravel pre eruptive processes and conditions in volcanic plumbing systems beneath intermediate arc volcanoes a case study from ciomadul volcano se carpathians ciomadul is the youngest volcano in the carpathian pannonian region produced crystal rich high k dacites that contain abundant amphibole phenocrysts the amphiboles in the studied dacites are characterized by large variety of zoning patterns textures and a wide range of compositions e g 6 4 15 wt al2o3 79 821 ppm sr often in thin section scale and even in single crystals two amphibole populations were observed in the dacite low al hornblendes represent a cold 900 c mafic magma amphibole thermobarometry suggests that the silicic crystal mush was stored in an upper crustal storage 8 12 km this was also the place where the erupted dacitic magma was formed during the remobilization of upper crustal silicic crystal mush body by hot mafic magma indicated by simple zoned and composite amphiboles this includes reheating by 200 c and partial remelting of different parts of the crystal mush followed by intensive crystallization of the second mineral population including pargasites breakdown textures of amphiboles imply that they were formed by reheating in case of hornblendes suggesting that pre eruptive heating and mixing could take place within days or weeks before the eruption the decompression rim of pargasites suggests around 12 days of magma ascent in the conduit several arc volcanoes produce mixed intermediate magmas with similar bimodal amphibole cargo as the ciomadul but in our dacite the two amphibole population can be found even in a single crystal composite amphiboles our study indicates that high al pargasites form as a second generation in these magmas after the mafic replenishment into a silicic capture zone thus they cannot unambiguously indicate a deeper mafic storage zone beneath these volcanoes the simple zoned and composite amphiboles provide direct evidence that significant compositional variations of amphiboles do not necessarily mean variation in the pressure of crystallization even if the al tschermak substitution can be recognized suggesting that amphibole barometers that consider only amphibole composition may often yield unrealistic pressure variation

limestone assimilation and the origin of co2 emissions at the alban hills central italy constraints from experimental petrology abstract the alban hills volcanic region 20 km south of rome in the roman province emitted a large volume of potassic magmas 280 km 3 during the quaternary chemical interactions between ascending magmas and the 7000 8000 m thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys in this paper we characterize the effect of carbonate assimilation on phase relationships at 200 mpa and 1150 1050 c by experimental petrology calcite and dolomite addition promotes the crystallization of ca rich pyroxene and mg rich olivine respectively and addition of both carbonates results in the desilication of the melt furthermore carbonate assimilation liberates a large quantity of co 2 rich fluid a comparison of experimental versus natural mineral glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different alban hills eruptions a maximum of 15 wt assimilation is suggested by some melt inclusion and clinopyroxene compositions however most of the natural data indicate assimilation of between 3 and 12 wt carbonate current high co 2 emissions in this area most likely indicate that such an assimilation process still occurs at depth we calculate that a magma intruding into the carbonate basement with a rate of 1 2 10 6 m 3 year estimated by geophysical studies and assimilating 3 12 wt of host rocks would release an amount of co 2 matching the current yearly emissions at the alban hills our results strongly suggest that current co 2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate hosted reservoir at 5 6 km depth with important consequences for the present day volcanic hazard evaluation in this densely populated and historical area

rapid remobilization of magmatic crystals kept in cold storage we lack thermal histories for magma reservoirs but here the magma under mount hood oregon usa is shown to have been too cold to mobilize for most of the time it has been stored which implies that magma mobilizes at which point it can be imaged geophysically very quickly prior to eruption this paper presents a novel approach to constraining the thermal history of the subsurface magma bodies that feed eruptions by combining temporal information from a variety of sources kari cooper and adam kent combine timescales derived from uranium series disequilibria textural information and trace element zoning in crystals they show that at mount hood oregon only a small fraction of the total storage duration has been spent at temperatures above the critical crystallinity the point at which magma is easily mobilized they conclude that largely liquid bodies that could be imaged geophysically will be ephemeral features and therefore their detection could indicate imminent eruption the processes involved in the formation and storage of magma within the earth s upper crust are of fundamental importance to volcanology many volcanic eruptions including some of the largest result from the eruption of components stored for tens to hundreds of thousands of years before eruption1 2 3 although the physical conditions of magma storage and remobilization are of paramount importance for understanding volcanic processes they remain relatively poorly known4 5 eruptions of crystal rich magma are often suggested to require the mobilization of magma stored at near solidus conditions6 7 8 however accumulation of significant eruptible magma volumes has also been argued to require extended storage of magma at higher temperatures7 8 9 what has been lacking in this debate is clear observational evidence linking the thermal and therefore physical conditions within a magma reservoir to timescales of storage that is thermal histories here we present a method of constraining such thermal histories by combining timescales derived from uranium series disequilibria crystal sizes and trace element zoning in crystals at mount hood oregon usa only a small fraction of the total magma storage duration at most 12 per cent and probably much less than 1 per cent has been spent at temperatures above the critical crystallinity 40 50 per cent at which magma is easily mobilized partial data sets for other volcanoes also suggest that similar conditions of magma storage are widespread and therefore that rapid mobilization of magmas stored at near solidus temperatures is common magma storage at low temperatures indicates that although thermobarometry calculations based on mineral compositions may record the conditions of crystallization they are unlikely to reflect the conditions of most of the time that the magma is stored our results also suggest that largely liquid magma bodies that can be imaged geophysically will be ephemeral features and therefore their detection could indicate imminent eruption

fractional crystallization of primitive hydrous arc magmas an experimental study at 0 7 gpa differentiation of mantle derived hydrous basaltic magmas is a fundamental process to produce evolved intermediate to sio2 rich magmas that form the bulk of the middle to shallow continental and island arc crust this study reports the results of fractional crystallization experiments conducted in a piston cylinder apparatus at 0 7 gpa for hydrous calc alkaline to arc tholeiitic magmas fractional crystallization was approached by synthesis of starting materials representing the liquid composition of the previous higher temperature experiment temperatures ranged from near liquidus at 1 170 c to near solidus conditions at 700 c h2o contents varied from 3 0 to more than 10 wt the liquid line of descent covers the entire compositional range from olivine tholeiite 1 170 c to high silica rhyolite 700 c and evolves from metaluminous to peraluminous compositions the following crystallization sequence has been established olivine clinopyroxene plagioclase spinel orthopyroxene amphibole titanomagnetite apatite quartz biotite anorthite rich plagioclase and spinel are responsible for a marked increase in sio2 content from 51 to 53 wt at 1 040 c at lower temperatures fractionation of amphibole plagioclase and fe ti oxide over a temperature interval of 280 c drives the sio2 content continuously from 53 to 78 wt largest crystallization steps were recorded around 1 040 c and at 700 c about 40 of ultramafic plutonic rocks have to crystallize to generate basaltic andesitic liquids and an additional 40 of amphibole gabbroic cumulate to produce granitic melts andesitic liquids with a liquidus temperature of 1 010 c only crystallize 50 over an 280 c wide range to 730 c implying that such liquids form mobile crystal mushes 50 crystals in long lived magmatic systems in the middle crust allowing for extensive fractionation assimilation and hybridization with periodic replenishment of more mafic magmas from deeper magma reservoirs

biot number and thermos bottle effect implications for magma chamber convection thermal boundary conditions model the coupling between a convecting magmatic body and its host such conditions need to be considered in models of igneous systems that involve thermal histories crystallization and fractionation of melt formation of aureoles by contact metamorphism and any other processes in which transport of heat plays a role usually investigations of magmatic systems have tended to emphasize modeling the interior convective regime relative to treatment of the thermal coupling yet it is found that the thermal nature of an intrusion is likely to be influenced more by coupling to its host than by the details of internal convective flows evaluation of a parameter having the form of a biot number bi provides a basis for estimating which boundary conditions are most appropriate it is found that bi 0 1 constant heat flux limit for models of several caldera systems for such values of the biot number the host regime behaves somewhat like a thermos bottle by limiting the flow of heat through the magma host system so that convective stirring of magma has little effect on the cooling rate of the intrusion because of this insulating effect boundary temperatures assumed in convection models should approach magmatic values even if an active hydrothermal system is present however high boundary temperatures do not imply that melting and assimilation of host rock by magma must occur despite the thermos bottle effect magmatic convection can still be quite vigorous

coseismic deformations of the 2015 mw 7 8 gorkha earthquake and interseismic strain accumulation in the himalayan tectonic belt and tibetan plateau abstract the principal strain rate derived from gps velocities from the tibetan plateau and the india plate shows that the himalayan tectonic belt exhibits compression deformation in a ne ns ne direction from the west to the east the gps velocity profiles reflect that the distribution of strain accumulation is uneven there is a 17 1 mm yr compressive deformation distributed over 400 km along 85 e longitude a 20 9 22 2 mm yr compressive deformation dispersed across 400 500 km along 79 e longitude and a 15 3 16 9 mm yr compressive deformation spread across 500 600 km along 91 e longitude the mw 7 8 gorkha earthquake occurred at the edge of an intense compression deformation zone of about 6 0 10 8 yr in a north south direction and an about 90 compressive strain is absorbed in the 300 km region near the main frontal thrust mft coseismic displacements larger than three standard deviations 3sd are mainly concentrated within 360 km from the epicenter the nodal plane of the main shock divides the areas where tensile strain release in an exponential attenuation pattern is dominant to the north and where compressive strain with upward movement is dominant to the south the results inversed by the sdm program reveal that the maximal slip of the gorkha earthquake is 5 33 m and its moment magnitude is mw 7 85 and the largest stress drop is 4 21 mpa slips larger than 0 5 m are mainly distributed in a region approximately 135 km 105 km which show that the rupture of the gorkha earthquake does not reach the surface finally we estimate that the recurrence period of this earthquake is about 166 20 years according to the strain accumulation before the earthquake and the coseismic release feature

evidence for a persistent magma reservoir with large melt content beneath an apparently extinct volcano abstract most active volcanoes display eruption frequencies of 10 1000s years but a class of volcanic systems has extremely long repose time 10 s kyr and are deemed as extinct yet some reawaken posing a particular threat because little is known about the way they endure and stir back to life reawakening primarily depends on the nature of the subvolcanic magma reservoir especially the presence and distribution of melt here we integrate petrology thermobarometry thermomechanical models geophysics and in situ electrical conductivity measurements to show that the magma storage beneath ciomadul a seemingly inactive volcano in eastern central europe that last erupted 30 ka may still hold 20 to 58 km3 of water rich silicic melt constituting up to 20 58 in parts of the upper crustal crystal mush body such a melt volume exceeds the volume of erupted lava over the entire history of the volcano this illustrates the important longevity of a magmatic reservoir at temperature above the solidus which implies that there is still a potential for rapid mush rejuvenation that a seemingly dead volcano like ciomadul is actually capable of erupting in the future calls for renewed attention to inactive volcanoes worldwide and perhaps for a redefinition of their activity inactivity status

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

seismic crustal structure between the transylvanian basin and the black sea romania abstract in order to study the lithospheric structure in romania a 450 km long wnw ese trending seismic refraction project was carried out in august september 2001 it runs from the transylvanian basin across the east carpathian orogen and the vrancea seismic region to the foreland areas with the very deep neogene focsani basin and the north dobrogea orogen on the black sea a total of ten shots with charge sizes 300 1500 kg were recorded by over 700 geophones the data quality of the experiment was variable depending primarily on charge size but also on local geological conditions the data interpretation indicates a multi layered structure with variable thicknesses and velocities the sedimentary stack comprises up to 7 layers with seismic velocities of 2 0 5 9 km s it reaches a maximum thickness of about 22 km within the focsani basin area the sedimentary succession is composed of 1 the carpathian nappe pile 2 the post collisional neogene transylvanian basin which covers the local late cretaceous to paleogene tarnava basin 3 the neogene focsani basin in the foredeep area which covers autochthonous mesozoic and palaeozoic sedimentary rocks as well as a probably permo triassic graben structure of the moesian platform and 4 the palaeozoic and mesozoic rocks of the north dobrogea orogen the underlying crystalline crust shows considerable thickness variations in total as well as in its individual subdivisions which correlate well with the tisza dacia moesian and north dobrogea crustal blocks the lateral velocity structure of these blocks along the seismic line remains constant with about 6 0 km s along the basement top and 7 0 km s above the moho the tisza dacia block is about 33 to 37 km thick and shows low velocity zones in its uppermost 15 km which are presumably due to basement thrusts imbricated with sedimentary successions related to the carpathian orogen the crystalline crust of moesia does not exceed 25 km and is covered by up to 22 km of sedimentary rocks the north dobrogea crust reaches a thickness of about 44 km and is probably composed of thick eastern european crust overthrusted by a thin 1 2 km thick wedge of the north dobrogea orogen