aftsolve a program for multi kinetic modeling of apatite fission track data aftsolve is a computer program for deriving thermal history information from apatite fission track data it implements a new fission track annealing model that takes into account the known kinetic variability among different apatite species to fully utilize this model a fission track worker must obtain data that can be used to infer the kinetic characteristics of each apatite grain from which a measurement was taken such data can consist of etch figure lengths or chemical composition the benefit of this overall approach is that it allows useful information to be derived from previously unusable analyses extends the practical range of geological temperatures constrained by fission track analyses and increases overall confidence in model predictions aftsolve also incorporates the effects of fission track orientation relative to the apatite crystallographic c axis variation in initial track length and the biasing effect of 2 5 2 cf irradiation for enhancing confined horizontal track length detection aftsolve is written for windows operating systems and has a graphical interface that allows interactive input of thermal histories and real time generation of estimates for fission track length distributions and ages for up to six simultaneously modeled kinetic populations it also includes procedures for estimating the range of time temperature histories that are statistically consistent with a data set and constraints entered by the user

heat flow study of the emeishan large igneous province region implications for the geodynamics of the emeishan mantle plume abstract the emeishan large igneous province elip is widely considered to be a consequence of a mantle plume the supporting evidence includes rapid emplacement voluminous flood basalt eruptions and high mantle potential temperature estimates several studies have suggested that there was surface uplift prior to the eruption of the emeishan flood basalts additionally the plume s lateral extent is hard to constrain and has been variously estimated to be 800 1400 km in diameter in this study we analyzed present day heat flow data and reconstructed the permian paleo heat flow using vitrinite reflectance and zircon u th he thermochronology data in the elip region and discussed implications for the geodynamics of the emeishan mantle plume the present day heat flow is higher in the inner and intermediate zones than in the outer zone with a decrease of average heat flow from 76 mw m2 to 51 mw m2 thermal history modeling results show that an abnormal high paleo heat flow of 90 110 mw m2 was caused by the emeishan mantle plume activity based on the present day heat flow data we can calculate that there is lithospheric thinning in the central elip region which may be due to the destruction of the lithosphere by mantle plume upwelling and magmatic underplating the permian paleo heat flow anomaly implies that there was a temperature anomaly in the mantle the ascending high temperature mantle plume and the thinned lithosphere may have induced the large scale uplift in the elip region according to the range of the surface heat flow anomaly it can be estimated that the diameter of the flattened head of the emeishan mantle plume could have reached 1600 1800 km our research provides new insights into the geodynamics of the emeishan mantle plume through study of heat flow

applicability of insar to tropical volcanoes insights from central america measuring volcano deformation is key to understanding the behaviour of erupting vol canoes and detecting those in periods of unrest satellite techniques provide the opportunity to do so on a global scale but with some notable exceptions the deformation of volcanoes in the tropics has been understudied relative to those at higher latitudes largely due to technical difficulties in applying interferometric synthetic aperture radar insar we perform a systematic survey of the central american volcanic arc to investigate the appli cability of interferometric synthetic aperture radar insar to volcanoes in the tropics volcano characteristics that may prevent insar measurement include 1 dense vegetation cover 2 per sistent activity and 3 steep slopes measurements of deformation are further inhibited by atmos pheric artefacts associated with 4 large changes in topographical relief we present a systematic method for distinguishing between water vapour artefacts and true deformation our data show a linear relationship c 2 cm km between the magnitudes of water vapour artefacts and volcano edifice height for high relief volcanoes e g fuego guatemala 3763 m a s l above sea level errors are of the order of 4 5 cm across the volcano s edifice but are less than 2 cm for lower relief e g masaya nicaragua 635 m a s l examples such as arenal atitlan and fuego illustrate that satellite acquisition strategies incorporating ascending and descending tracks are particularly important for studying steep sided volcanoes poor coherence is primarily associated with temporal decorrelation which is typically more rapid in southern central america where evergreen broadleaf vegetation dominates land use classification is a better predictorof decorrelation rate thanvegetationindex comparisonof coher ence for different radar wavelengths match expectations high resolution x band radar is best suited to local studies where high resolution digital elevation models dems exist while l bandwavelengths are necessary for regional surveys however this is the first time that relation ships between phase coherence and time perpendicular baseline radar wavelength and land use have been quantified on the scale of a whole volcanic arc

a diode laser system for heating minerals for u th he chronometry we have developed a diode laser 25 w 808 nm system for he extraction from minerals for u th he chronometry the laser beam is delivered via a 600 m fiber cable and focused using a binocular microscope temperatures necessary for he release from apatite 500 600 c and zircon 1100 1300 c encapsulated in pt foil tubes are attained by heating to 0 5 w for 30 s and 1 25 2 5 w for 20 min respectively using a defocused beam heating at these powers does not result in measurable u and or th loss from apatite as noted by the preservation of the distinct th u in multiple splits of two different durango apatite crystals analyses of durango and the california institute of technology internal standard apatite 97mr22 yield u th he ages of 32 8 1 8 ma 1 n 11 and 4 6 0 5 1 n 5 respectively well within accepted ages the u th he age and th u of five fish canyon tuff zircon aliquots yield 29 3 2 2 ma 1 and 0 6 0 03 respectively and are indistinguishable from ages produced by resistance furnace he extraction heating of unencapsulated minerals shows that the diode laser couples well with optically opaque minerals e g hornblende biotite muscovite garnet and basalt groundmass suggesting that diode lasers offer a cheap small low maintenance alternative to nd yag and ar ion lasers for 40ar 39ar cosmogenic noble gas and stable isotope studies

heat flow on the hawaiian swell and lithospheric reheating most oceanic volcanic centres caused by hotspot activity are surrounded by sea floor that is unusually shallow for its age1 2 there is increasing evidence that swells found on older sea floor like the hawaiian swell have formed from a broad scale reheating and thinning of the lithosphere as it passes over a mantle hotspot3 4 if the formation and subsequent disappearance of these swells are controlled by thermal processes they should have an above normal heat flux we present here the results from 95 new heat flow measurements on the hawaiian swell along the older part of the swell the heat flow is 20 25 higher than the normal heat flow for crust of this age this anomaly is consistent with the observed swell uplift the shape and amplitude of the heat flow anomaly require that the reheating be largely confined to the lower half of the lithosphere

the effect of hot spots on the oceanic age depth relation hot spots located both midplate and on midocean ridges can bias the empirical age depth relation ocean floor bathymetry for seafloor greater than 80 m y b p in age has been previously used to determine if the oceanic lithosphere behaves as a cooling half space or as a cooling plate however large areas of the ocean basins do not fit a simple age depth relation anomalously shallow swells approximately 1000 km wide and 1 km high surround hot spots such as iceland the azores and the cape verde islands by sorting seafloor depth data by distance to the nearest hot spot track we show that the along isochron variation in depth in the north atlantic correlates with distance from a hot spot track due to the absence in the north atlantic of seafloor both old and far from hot spots we compare depth versus age at constant distance and do not observe flattening of the age depth relation in any distance range the age depth relation depth meters 2700 295 t m y 1 2 derived for seafloor 1200 to 1800 km from a hot spot track represents our best estimate of the age depth relation appropriate to seafloor unaffected by a hot spot track in the north atlantic the previously inferred flattening of the age depth relation appears to be caused by the inclusion of hot spot swells this implies that hot spots may be the primary means of heat transfer from the deeper mantle to the base of the lithosphere

crustal processes at spreading centers recent discoveries and research on mid ocean ridges mor s in the last four years have greatly increased our knowledge of this fundamental type of plate boundary the last iugg review of mor research was in 1975 aumento et al 1975 and its omission as a topic in 1978 may have reflected a feeling that spreading centers were reasonably well understood since that time however there has been a surfeit of important new observations and exciting research and there is now a turmoil of innovative ideas about the processes which create and leave their imprint on two thirds of the earth s crust new seismic measurements have been made and interpreted as evidence for the existence of shallow axial magma chambers amc beneath intermediate total opening rate 5 9 cm yr and fast 9 18 cm yr spreading centers fig 1 yet there is controversy as to whether they are steady state whether they persist beneath slow ridges as well in the steady state what the dimensions and shape of the chamber are its relation to oceanic crustal stratigraphy and its relation to observations in ophiolites black smoker hydrothermal vents have been discovered in the pacific spewing forth 350 c fluids blackened by polymetallic sulfide precipitates this discovery is embroiled in debate as to how long the vents last whether they occur at slow spreading rates as well whether the enormous heat flux of the vents freeze the magma chamber even at fast spreading rates their influence on geochemical balances in the ocean and the value of the sulfide deposits commercially it has been found that our initial view of mor s as two dimensional linear structures has served us well as an initial working model but must be significantly modified to account for variations in tectonic volcanic and hydrothermal activity along strike as well as for episodicity of these processes deep sea drilling project dsdp samples have raised fundamental questions about formation of the magnetic source layer hydrothermal circulation and fault mechanisms along the mor spreading centers which penetrate existing lithosphere along strike as propagating rifts have modified our views of how plate boundaries reorient themselves and how v shaped magnetic and topographic trends are formed we have also found that transform faults may modify spreading center processes for some distance away from their intersections with mor s and that rigid plate transform faults may fail to develop at fast spreading centers under certain conditions resulting in en echelon overlapping of spreading centers this review will focus on these developments and several others only example references to these topics will be given in the text and many important topics will not be discussed directly e g petrology and geochemistry mantle convection research on lithosphere older than 1 m y however i have tried to compile and have included an extensive bibliography for u s research on a broader range of mor topics for mid 1978 to mid 1982 which is the main purpose of this report pre 1978 references are occasionally included where appropriate abstracts are not included

geomorphic development of the escarpment of the eritrean margin southern red sea from combined apatite fission track and u th he thermochronometry apatite u th he and fission track thermochronometers are combined to constrain models of denudation and escarpment development of the high elevation eritrean margin along the southern red sea u th he ages have been determined for apatites from two coast perpendicular transects that were previously used for apatite fission track analysis e abbate m l balestrieri g bigazzi morphostructural development of the eritrean rift flank southern red sea inferred from apatite fission track analysis j geophys res 107 b11 doi 10 1029 2001jb001009 2002 in central eritrea near asmara he ages increase from c 7 ma at the coast to 152 ma on the plateau along a transect further south he ages from the margin border to the base of the escarpment span a narrower range 7 to 12 ma one sample from the top of a marginal high 2950 m yields older ages 22 43 ma forward modeling suggests that the he age distribution across the margin should allow scarp retreat and downwearing mechanisms to be distinguished in the case of a margin formed in the last twenty million years the distribution of he ages suggests that the escarpment evolved by downwearing and that post break up erosion of the escarpment was facilitated by in situ excavation rather than parallel retreat this implies the existence of an inland drainage divide located seaward of the present day escarpment rim we envisage that the inland divide formed during or immediately after continent break up and that the eastern marginal belt represents a remnant of the apex structure the short distance between the eastern marginal belt and the rim c 10 km represents the total retreat of the escarpment comparison of the measured he ages from the coastal plain with those predicted from forward modelling indicates that the main phase of post break up erosion started at about 15 ma closer to the initiation of seafloor spreading in the red sea than was thought previously

lithospheric heating by mantle plumes summary a broad topographic swell is associated with the hawaiian hotspot a kinematic model is developed assuming that downstream of the hotspot this swell is produced by lithospheric heating by a mantle plume material from the model plume flows radially in the asthenosphere and eventually heats the lower lithosphere upstream from the hotspot the model swell owes its existence mainly to hot material at asthenospheric depths the model predicts extensive lithospheric heating downstream from the hotspot interpreted data to tell if the lower lithosphere behaves in this way are lacking

late pleistocene to holocene temporal succession and magnitudes of highly explosive volcanic eruptions in west central nicaragua the stratigraphic succession of widespread tephra layers in west central nicaragua was emplaced by highly explosive eruptions from mainly three volcanoes the chiltepe volcanic complex and the masaya and apoyo calderas stratigraphic correlations are based on distinct compositions of tephras the total tephras combine to a total on shore volume of about 37 km3 produced during the last 60 ka the total erupted magma mass including also distal volumes of 184 gt dre distributes to 84 into 9 dacitic to rhyolitic eruptions and to 16 into 4 basaltic to basaltic andesitic eruptions the widely dispersed tephra sheets have up to five times the mass of their parental volcanic edifices and thus represent a significant albeit less obvious component of the arc volcanism eruption magnitudes m log10 m 7 with m the mass in kg range from m 4 1 to m 6 3 most of the eruptions were dominantly plinian with eruption columns reaching variably high into the stratosphere but minor phreatomagmatic phases were also involved two phreatomagmatic eruptions one dacitic and one basaltic andesitic produced mostly pyroclastic surges but also fallout from high eruption columns comparison of fallout tephra dispersal patterns with present day seasonally changing height dependant wind directions suggests that 8 eruptions occurred during the rainy season while 5 took place during the dry season the tephra succession documents two major phases of erosion the first phase 17 ka ago appears to be related to tectonic activity whereas the second phase may have been caused by wet climatic conditions between 2 to 6 ka ago the apoyo caldera had two large plinian caldera forming eruptions in rapid succession about 24 ka ago and should be considered a silicic volcano with long repose times three highly explosive basaltic eruptions were generated at the masaya caldera within the last 6 ka since then frequent but small eruptions and lava effusion were largely limited to the caldera interior the dacitic chiltepe volcanic complex experienced six plinian eruptions during the last 17 ka and seems to be an accelerating system in which eruption magnitude increased while the degree of differentiation of erupted magma decreased at the same time we speculate that the chiltepe system might produce the next large magnitude silicic eruption in west central nicaragua

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

unraveling multiple thermotectonic events accommodated by crustal scale faults in northern iberia spain insights from k ar dating of clay gouges

variations in oceanic layer 2 elastic velocities near hawaii and their correlation to lithospheric flexure analysis of the travel times and amplitude range distributions of both compressional and shear wave arrivals on 15 closely spaced refraction profiles reveals a significant systematic and symmetric dependence of average layer 2 velocities on their distance to the north and south of the hawaiian ridge beyond the flexural arch surrounding the ridge the velocity depth solutions indicate a normal layer 2 within the arch approximately 155 km from the ridge the average elastic velocities in layer 2 are lowered by 0 8 0 9 0 2 km s within 75 km of the ridge the average velocities are again normal elastic and elastic plastic flexural models for the regional compensation of the hawaiian islands predict tensional stress drops of 0 8 kbar in the upper lithosphere for the region having lowered velocities in layer 2 which are similar in magnitude with laboratory measurements of the confining pressure drop necessary to reduce velocities in porous basalts by 0 5 km s a significant inverse relationship correlation coefficient of 0 818 exists between the average elastic velocities in the upper 1 0 km of the igneous crust and the strain in the upper crust calculated from these flexural models the correlation between lowered average velocities in layer 2 and increased tensional stresses and strains suggest that crack opening in the upper crust accompanies the flexure these observations are the first reported for a midplate load and corroborate previous suggestions from seismic and flexural data at subduction zones

accurate measurements of tropospheric effects in volcanic areas from sar interferometry data application to sakurajima volcano japan abstract the accuracy of surface deformation maps derived from dinsar differential interferomery synthetic aperture radar in volcanic areas is limited by temporal variations of the vertical refractivity profile in the troposphere between the radar data acquisitions due to their dependence on altitude such variations may produce topography related fringes in the computed interferograms the variations should be carefully estimated in a given area so that they can be discriminated with real ground deformation signals in this paper we present a clear example of tropospheric induced fringes reaching up to 2 9 fringes over 1200 m evidenced on sakurajima volcano japan from ers 1 and ers 2 data the analysis of phase altitude correlations based on network adjustments of the interferometric dataset leads to a simple linear model of the tropospheric excess path delay with an rms accuracy of 0 4 cm that might be used for further corrections a more detailed investigation of these phase variations providing accurate measurements of linear and non linear contributions of tropospheric effects is also presented and shows that tropospheric phase delays can be better modeled on sakurajima with a non linear model

assessment of the capabilities of the temporal and spatiotemporal ica method for geophysical signal separation in grace data we investigate the potential of two independent component analysis ica methods i e the temporal and spatiotemporal ica for separating geophysical signals in gravity recovery and climate experiment grace data these methods are based on the assumption of the statistical independence of the signals and thus separate the grace observed mass changes into maximal independent signals these two ica methods are compared to the conventional principal component analysis pca method we test the three methods with respect to their ability to separate a periodic hydrological signal from a trend signal originating in the solid earth or the cryosphere with simulated and center for space research grace mass changes for the time period of january 2003 to december 2010 in addition we investigate whether the methods are capable of separating hydrological annual and semiannual mass variations it is shown that both ica methods are superior to pca when non gaussian mass variations are analyzed furthermore the spatiotemporal ica resolves successfully the lack of full temporal and spatial independence of the geophysical signals observed by grace both in global and regional simulation scenarios although the temporal and spatiotemporal ica are nearly equivalent both superior to pca in the global grace analysis the spatiotemporal ica proves to be more efficient in regional applications by recover more reliably the postglacial rebound trend in north america and the bimodal total water storage variability in africa

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

exhumation of the sierra de cameros iberian range spain constraints from low temperature thermochronology we present new fission track and u th he data from apatite and zircon in order to reconstruct the exhumation of the sierra de cameros in the northwestern part of iberian range spain zircon fission track ages from samples from the depocentre of the basin were reset during the metamorphic peak at approximately 100 ma detrital apatites from the uppermost sediments retain fission track age information that is older than the sediment deposition age indicating that these rocks have not exceeded 110 c apatites from deeper in the stratigraphic sequence of the central part of the basin have fission track ages of around 40 ma significantly younger than the stratigraphic age recording the time of cooling after peak metamorphic conditions apatite u th he ages in samples from these sediments are 31 40 ma and record the last period of cooling during alpine compression the modelled thermal history derived from the uppermost sediments indicates that the thermal pulse associated with peak metamorphism was rapid and that the region has cooled continuously to the present the estimated palaeogeothermal gradient is around 86 c km 1 and supports a tectonic model with a thick sedimentary fill c 8 km and explains the origin of the low grade metamorphism observed in the oldest sediments

unraveling the mesozoic and cenozoic tectonothermal evolution of the eastern basque cantabrian zone western pyrenees by low temperature thermochronology this is a contribution of the geotec group idi 2018 000216 and projects misterios cgl2013 48601 c2 2 r consolider ingenio 2010 topo iberia csd2006 00041 and esf topoeurope project pyrtec sv pa 10 03 ip2 pyrtec we thank additional financial support by the university of oviedo banco santander the government of the principality of asturias through the science technology and innovation plan pcti the european union through feder funds and the spanish ministry of education culture and sport through the training programme for academic staff fpu grant for idf

thermal origin of the hawaiian swell heat flow evidence and thermal models the lithospheric reheating hypothesis for the origin of the hawaiian swell has been tested by heat flow measurements along the swell between hawaii and midway ninety five measurements at eight carefully selected sites show that the heat flux on the swell increases systematically from near normal values 52 2 mw m 2 near hawaii to values near midway 59 2 mw m 2 about 20 25 higher than normal for lithosphere of that age 110 m y this heat flow pattern is qualitatively consistent with a deep seated thermal anomaly created in a lithospheric plate moving across a fixed heat source modeling of the heat flow and bathymetry data on the hawaiian swell strongly suggest that the swell is caused by a rapid heating within 40 to 50 km depth of normal 90 m y old lithosphere over a relatively broad 500 1000 km region near hawaii this model is also consistent with gravity and geoid anomalies associated with the swell which require a low density region in the lower lithosphere and with flexure studies of seamounts in the hawaiian chain which indicate that the rigidity of the lithosphere is not significantly reduced by the reheating appendices a c are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j82 005 1 00 payment must accompany order

geoid anomalies and dynamic topography from convection in cylindrical geometry applications to mantle plumes on earth and venus summary a variety of evidence suggests that at least some hotspots are formed by quasi cylindrical mantle plumes upwelling from deep in the mantle we model such plumes in cylindrical axisymmetric geometry with depth dependent newtonian viscosity cylindrical and sheet like cartesian upwellings have significantly different geoid and topography signatures however rayleigh number nusselt number systematics in the two geometries are quite similar the geoid anomaly and topographic uplift over a plume are insensitive to the viscosity of the surface layer provided that it is at least 1000 times the interior viscosity increasing the rayleigh number or including a low viscosity asthenosphere decreases the geoid anomaly and the topographic uplift associated with an upwelling plume increasing the aspect ratio increases both the geoid anomaly and the topographic uplift of a plume the nusselt number is a weak function of the aspect ratio with its maximum value occurring at an aspect ratio of slightly less than 1

effect of lithostatic pressure and tectonic deformation on the magnetic fabric anisotropy of magnetic susceptibility in low grade metamorphic rocks the role of lithostatic pressure and strain in low grade metamorphic cover rocks is analyzed through the anisotropy of magnetic susceptibility ams of jurassic and cretaceous siltstones and limestones from the cameros basin north spain for rocks initially characterized by precleavage magnetic fabric the main change in the magnetic fabric produced by the increase of lithostatic pressure is the increment in the degree of anisotropy pj in rocks affected by syncleavage deformation the magnetic fabric depends on the mechanism of internal deformation involved in fabric development in siltstones where cleavage is correlated with synkinematic recrystallization of phyllosilicates and rigid body rotation of grains the magnetic fabric is coherent with the internal deformation determined by strain analysis on deformed nodules on the contrary in limestones we observe a complete reorganization of the magnetic fabric probably due to the discontinuous character of the cleavage formation mechanism detailed analysis of the parameter angle between the bedding pole and the minimum susceptibility axis parallel to the cleavage pole indicates that for rocks characterized by syncleavage magnetic fabric the different variation pattern of tj and pj parameters is closely related to the deformation mechanisms responsible for the fabric development

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

thermal isostasy response of a moving lithosphere to a distributed heat source spreading ridges and hot spot swells are identified by their high surface heat flow shallow seafloor and high geopotential to understand these and other thermotectonic features the oceanic lithosphere is modeled as a thermomechanical boundary layer moving through a three dimensional time independent heat source the heat source mimics the heat advection associated with a spreading ridge or hot spot without introducing the nonlinearities of these flow processes the fourier transforms of three green s functions response functions which relate the three observable fields to their common heat source are determined analytically each of these reponse functions is highly anisotropic because the lithosphere is moving with respect to the source however the ratio of the gravity response function to the topography response function i e gravity topography transfer function is nearly isotropic and has a maximum lying between the flexural wavelength and 2 times the thickness of the thermal boundary layer the response functions are most useful for determining the surface heat flow seafloor topography and geopotential for complex lithospheric thermal structures in practice these three observables are calculated by multiplying the fourier transform of the heat source by the appropriate response function and inverse transforming the products almost any time independent thermotectonic feature can be modeled using this technique included in this report are examples of spreading ridges and thermal swells although more complex geometries such as ridges offset by transform faults and rrr type triple junctions can also be modeled because forward modeling is both linear and computationally simple the inverse of this technique could be used to infer some basic characteristics of the heat source directly from the observed fields

comment on gonzalez acebron et al criteria for the recognition of localization and timing of multiple events of hydrothermal alteration in sandstones illustrated by petrographic fluid inclusion and isotopic analysis of the tera group northern spain int j earth sciences 2011 100 1811 1826 the paper by gonzalez acebron et al 2011 deals with both regional and methodological problems about the timing of thermal events in one of the best known and controversial basins in the iberian microplate the late jurassic early cretaceous cameros basin the aforementioned paper contains invaluable data about the thermal evolution of the basin and it is an important contribution to the understanding of the post sedimentary pre inversion processes in this strongly subsiding basin it will undoubtedly add new evidence to the knowledge of hydrothermal processes in general and particularly to the paleothermal evolution of the basin however in our opinion there are some problems involving important matters within the paper namely 1 the interpretation of the data obtained which are too constrained within a univocal line of thinking without considering other simpler and more viable options that in the discussed paper are aprioristically rejected 2 the second problem deals with referencing to previous papers and acknowledgement of previous works by other authors we must say that this aspect does not refer to this paper alone but it is recently becoming a commonplace for many scientific papers in this field on the side of the references to previous works it must be stated that

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

annealing kinetics of fission tracks in zircon an experimental study a series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350 750 c for 10 1 103 hr i e 4 5 min 40 days variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from nisatai dacite the fading contours of normalized mean track length r on the arrhenius diagram showed as sets of straight lines we performed a series of model fittings called the parallel and fanning models in order to describe the decrease in r with increasing temperature or heating time the lowest temperature limit of the zircon partial annealing zone zpaz was defined as r 0 95 and the highest as r 0 4 which approximately corresponded to the total fading of surface tracks extrapolation of the results of the laboratory experiments to the geological timescale gives for a heating duration of 106 yr estimated values of the zpaz of 210 320 c 60 c 2 with the parallel model 190 350 c 50 c 2 with the fanning model critical temperature t0 and 170 390 c 50 c 2 with the fanning model t0 the temperatures of the zpaz decrease by 20 c for an annealing duration that is an order of magnitude longer because the estimated closure temperature of zircon fission track analysis approximately corresponds to the middle of the zpaz these results support the previously estimated closure temperature of 240 c by varying the etching time it was revealed that significant removal of radiation damage occurs at r 0 93

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

timing of diagenesis and very low grade metamorphism in the eastern sector of the sierra de cameros iberian range spain a u pb shrimp study on monazite the sierra de cameros is an intracontinental orogen and represents the north western part of the iberian range in northern spain it comprises a thick sequence of syn rift continental sediments mainly sandstones and carbonates deposited during lower cretaceous times a unique characteristic of the sierra de cameros in relation to the rest of the iberian range is the presence of low grade metamorphism in certain parts of the basin an event that predates basin inversion this paper describes the presence textural relationships and geochemical aspects of authigenic and or metamorphic monazite within different lithologies from the deepest parts of the basin sensitive high resolution ion microprobe shrimp u pb dating of monazite records the presence of two age populations the first with 206 pb 238 u ages ranging from 122 to 116 ma which is considered as diagenetic in origin whilst the second is dated at 99 2 ma and postdates the metamorphic climax

lithospheric flexure and thermal anomalies plots of effective elastic thickness te of the oceanic lithosphere as a function of age when elastically deformed show a general increase in te with the square root of age although there is much scatter some of the scatter can be eliminated by correcting for the effect of finite yield strength in rocks which makes te for more sharply bent plates underestimate the true depth tm to the rheological boundary at the base of the high strength mechanical lithosphere after converting effective values te to true thicknesses tm it appears that the mechanical lithosphere is always thinner beneath islands and seamounts compared to lithosphere of similar age flexed at subduction zones from several other lines of evidence such as depth anomalies seamount subsidence and heat flow data it has been suggested that the thermal structure in plates subjected to hot spot type volcanism is reset to values appropriate for much younger lithosphere the reduction in mechanical plate thickness beneath hot spot volcanoes is also consistent with this concept of thermal rejuvenation since the strength of rocks decreases exponentially with rising temperature this dependence implies that variations in mechanical plate thickness can be used to map temperature anomalies in the lithosphere since the mechanical plate thickness depends principally upon the temperature at one depth specifically the depth at which the temperature reaches 550 600 c depending on strain rate flexural data are particularly sensitive indicators of the vertical structure of lithospheric reheating compared to quantities dependent on depth integrals of temperature such as swell height and subsidence the thermal rejuvenation hypothesis predicts that the flexural profile should mimic viscoelastic relaxation in the first 10 ma after loading if initially reheating is confined to depths close to and below the 550 c isotherm the flexural data combined with depth anomaly information for hawaii point to extremely rapid reheating localized in the lower lithosphere rejuvenation in the society islands on the other hand is compatible with slower methods of heat injection involving the entire lithospheric column

heat flow and the thermal origin of hot spot swells the hawaiian swell revisited we present 150 new heat flow measurements obtained at eight sites along a 1230 km long profile across the hawaiian swell about 700 km ese of midway island most of the measurements include in situ thermal conductivity determinations which helped to reduce the statistical uncertainties 95 confidence at all sites to 59 mw m 2 about 20 higher than the predicted heat flow for 100 ma seafloor based on simple lithospheric cooling models thus even though there is a small increase in heat flow with age along the swell when compared with the off swell heat flux the anomalous heat flow associated with the hawaiian swell is probably of the order of 5 10 mw m 2 and arguably may not exist at all a previous investigation von herzen et al 1982 may have overestimated the magnitude of the heat flow anomaly associated with the hawaiian swell by comparing heat flux measurements on the swell with values expected for simple lithospheric cooling models the heat flow anomalies associated with the bermuda rise and the cape verde rise may also be smaller than previously estimated given the uncertainties in the heat flux on the normal seafloor surrounding these swells the lack of a significant heat flow anomaly associated with the bathymetric expression of the hawaiian swell is inconsistent with simple models of lithospheric reheating dynamic support accompanied by modest temperature increases 80 ma oceanic lithosphere

extensional subsidence contractional folding and thrust inversion of the eastern cameros basin northern spain tectonic analysis of the cameros massif northern spain demonstrates the need to integrate detailed structural analysis with stratigraphic studies in order to understand the development of inverted basins the cameros massif underwent three major tectonic events each characterized by different mechanisms of deformation the first event tithonian early albian manifested as continental rifting and formation of the cameros basin and was attended by normal faulting and related folding of pre and syn rift sedimentary sequences up to 9 km thick it corresponded to the beginning of rifting and opening of the bay of biscay to the north of the massif the second event occurred at the end of the early cretaceous the basin underwent contraction manifested as gentle folds containing axial plane cleavage this contraction was due to the migration of the center of rifting away from the basin and toward the northeast and correlates with the onset of oceanic spreading in the bay of biscay deformation happened during a low grade metamorphism period that reached its thermal peak after folding and cleavage formation 90 100 ma the final stage of deformation eocene miocene following a structurally quiescent period of approximately 40 ma occurred during the convergence collision between iberia and europe it formed contractional folds related to large e w striking overthrusts the mesozoic basin was inverted and transported 25 km toward the north during this stage both unfolding and tightening of the former folds occurred as determined from analysis of cleavage orientation associated with the previous shortening