a barotropic inverse tidal model for the arctic ocean 1 we describe high resolution 5 km grid linear dynamics and inverse models of arctic ocean barotropic tides obtained with the osu tidal inversion software otis package the 8 constituent dynamics based model uses the latest ibcao bathymetry and open boundary forcing from the recent tpxo 6 2 global barotropic tidal solution this model performs significantly better than the present benchmark arctic tidal model 14 km grid by z kowalik and a proshutinsky as judged by comparisons with 300 coastal tide gauges the greatest improvements are found in the canadian arctic archipelago nares strait and the baffin bay and labrador sea and can be explained by the higher resolution of the new model in these topographically complex regions the new arctic inverse model assimilates coastal and benthic tide gauges and topex poseidon and ers altimetry for further improvements of the 4 dominant constituents m2 s2 k1 and o1

seismicity and tectonics of the south shetland islands and bransfield strait from a regional broadband seismograph deployment 1 we investigate the tectonics of the south shetland trench and bransfield strait by performing a detailed study of local seismicity during 1997 1999 we deployed seven land seismometers and 14 ocean bottom seismometers in the south shetland island region the data we obtained indicate a high level of local seismicity mb 2 5 and we accurately located 150 earthquakes many of the earthquakes occur at locations and depths indicative of ongoing subduction in the south shetland trench a focal mechanism for the largest event in the forearc indicates shallow angle thrusting the maximum depth of seismicity is 65 km but the majority of the events are shallower than 30 km these seismic results are consistent with recent magnetic gps and multichannel seismic reflection data that suggest continued subduction at a very slow rate the south shetland trench thus represents an extreme end member of hot subduction resulting from slow convergence of young lithosphere and the absence of intermediate depth earthquakes is consistent with thermal assimilation of the slab at shallow depths we have located many earthquakes associated with volcanism and rifting in bransfield strait a swarm of events near a submarine volcano suggests current magmatic activity a normal faulting focal mechanism in the northeastern part of the strait gives evidence of extension earthquakes associated with rifting in the northeastern portion of the strait are clustered along well established rifts but the seismicity is much more diffuse to the southwest this observation is consistent with other evidence that extension has propagated from northeast to southwest

tectonics of the scotia antarctica plate boundary constrained from seismic and seismological data abstract the plate boundary between the scotia and antarctic plates runs along the broadly e w trending south scotia ridge it is a mainly transcurrent margin that juxtaposes thinned continental and transitional crust elements with restricted oceanic basins and deep troughs seismic profiles and regional scale seismological constraints are used to define the peculiarities of the crustal structures in and around the southern scotia sea and focal solutions from recent earthquakes help to understand the present day geodynamic setting the northern edge of the western south scotia ridge is marked by a sub vertical left lateral master fault locally a narrow wedge of accreted sediments is present at the base of the slope this segment represents the boundary between the scotia plate and the independent south shetland continental block along the northern margin of the south orkney microcontinent the largest fragment of the south scotia ridge an accretionary prism is present at the base of the slope which was possibly created by the eastward drift of the south orkney microcontinent and the consequent subduction of the transitional crust present to the north east of the south orkney microcontinent the physiography and structure of the plate boundary are less constrained here the tectonic regime exhibits mainly strike slip behavior with some grade of extensional component and the plate boundary is segmented by a series of nnw sse trending release zones which favored the fragmentation and dispersion of the crustal blocks seismic data have also identified along the north western edge of the south scotia ridge an elevated region the ona platform which can be considered along with the terror rise as the conjugate margin of the tierra del fuego before the drake passage opening we propose here an evolutionary sketch for the plate boundary from the late oligocene to the present encompassing the segment from the elephant island platform to the herdman bank

surface wave tomography and seismic source studies at campi flegrei italy abstract we analyse a set of events recorded in march 1984 during a period of intense seismicity of the last bradyseismic crisis to determine shallow velocity models and seismic source moment tensors in the campi flegrei region the velocity models of the crust are obtained by surface wave tomography two inland negative anomalies of group velocity resulting in our tomographic maps well agree with previous independent measurements whereas a third anomaly located in the pozzuoli gulf and not evidenced by previous studies is in correspondence with the caldera position the inversion of the dispersion curves allows us to extend the already available velocity models within the uppermost 2 km of the crust the obtained models are employed to study seismic source features by the moment tensor analysis preliminary synthetic tests are performed in order to minimise artefacts in the moment tensor solutions possibly due to numerical noise to station distribution or to the structural modelling approximation most of the investigated earthquakes are deviatoric mechanisms and the increase of the isotropic component is observed in connection with the change of the seismicity rate in the investigated temporal window

tectonic development of the bransfield basin and its prolongation to the south scotia ridge northern antarctic peninsula abstract the bransfield basin is located off the northern tip of the antarctic peninsula the analysis of multichannel seismic reflection profiles allows the shallow structure of the bransfield basin and its eastwards prolongation through the scotia sea to be imaged the bransfield basin is asymmetrical with most of the sediment input coming from the passive antarctic peninsula margin which is deformed by normal faults generally dipping less than 45 northwestwards much less sediment comes from the conjugate south shetland islands margin which is dominated by high angle normal faults generally dipping between 45 and 60 constituting the inner boundary of the south shetland block tectonic horst the detachment and moving apart of the south shetland block from the antarctic peninsula led to the opening of the bransfield basin where incipient oceanic spreading has been reported previously the south shetland block outer boundary to the northwest is made of the south shetland trench which to the east passes into the sinistral transpressive scotia antarctic plate boundary marked by the prominent south scotia ridge following cessation of spreading in the phoenix antarctic ridge northwest of the south shetland block during middle pliocene roll back played a major role in the development of the bransfield basin with maximum extension in the central subbasin in addition the eastern bransfield basin accommodates most of the sinistral transtensional deformation along the south scotia ridge normal and reverse faults were simultaneously active along the inner and outer boundaries respectively of the continental crust fragment constituting the south shetland block the development of the bransfield basin offers a good example of the tectonic processes involved in continental fragmentation associated with backarc basin development

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

continental fragmentation along the south scotia ridge transcurrent plate boundary ne antarctic peninsula abstract the study of the south scotia ridge on the basis of swath bathymetry multichannel seismic and magnetometry profiles obtained during the hesant92 93 cruise and complemented with satellite gravimetry and seismicity data illustrates the tectonics of the region the thinned continental crust fragments of the ridge are bounded by oceanic crust of the scotia sea to the north and powell basin to the south the northern boundary represents the contact between the scotia and antarctic plates this boundary is a sinistral transpressional fault with transtensional segments and moderate recent tectonic activity another fault located at the southern boundary appears inactive and does not reveal any features that would enable the kinematics to be determined both faults have associated steep scarps since they separate oceanic and continental crust types the most significant active deformation lies in the axial depression of the ridge within a band delineated by fault systems with wsw ene and sw ne strikes these faults develop pull apart basins which separate the northern and southern blocks of the ridge the northern block is being fragmented from the antarctic plate by a zone of transtensive faults and is probably a crustal element independent of the antarctic plate the axial depression which crosses the ridge slightly obliquely is characterized by deep basins locally more than 5000 m deep and associated high seismicity the fault geometry and earthquake focal mechanisms indicate an active sinistral transtensive regime for the fault system although it may locally have transpressive regimes depending on the fault plane and the stress field orientations the internal basins are characterized by an asymmetric development showing itself as depositional wedges generally thickening northward deposits onlap the southern margins and are affected by normal faults in the northern margins the seismicity around the scotia plate shows that the present stresses are compressive along the northern boundary with the south american plate 1 sw ne and subhorizontal and along the western boundary with the antarctic plate 1 wnw ese and subhorizontal for the south scotia ridge however 1 is steeply inclined and 3 is subhorizontal with a nw se trend the stress distribution in bransfield strait is similar to the ridge and the recent extension could be partially explained by the westward continuation of the active fault system of the central south scotia ridge the fragmentation of continental crustal blocks due to the tectonic activity along the transcurrent plate boundaries is a mechanism that contributes to the deformation of the northeastern end of the antarctic peninsula this area appears appropriate for the analysis of continental plate fragmentation processes

the dynamics of the 2001 etna eruption as seen by full moment tensor analysis summary the mt etna eruption of july 2001 was announced by severe seismic activity and by the opening of a 7 km long zone of densely distributed fractures the large amount of data collected gave a unique opportunity to study the magma migration process and to infer the position and geometry of the uprising dyke results from multidisciplinary approaches suggest that the observed phenomenology was the result of the rapid intrusion of a vertical dyke oriented roughly n s and located a few km south of the summit region to add new constraints to the dynamics of the eruption process in this study we determine the full seismic moment tensors of 61 earthquakes selected among those occurring between july 12 and july 18 md 2 2 located in a depth ranging from 1 km above sea level a s l to 3 km below sea level b s l at the beginning of the seismic swarm the dominant component of the seismic source tensor is double couple percentage around 65 per cent on average statistical significant at 95 per cent confidence level and in the following hours the non double couple components increase at the expenses of the double couple such observations are related well with the system of fractures formed just before the eruption whereas the increasing non double couple components can be explained as the response of the confining rocks to the rising magma and degassing processes the type of focal mechanisms retrieved are predominantly of normal fault type 44 per cent strike slip 30 per cent and thrust mechanisms 9 per cent and outline a scenario that concurs with the stress regime induced by a dyke injection the space time analysis of seismic source locations and source moment tensors 1 confirms the evidence of a vertical dyke emplacement that fed the 2001 lateral eruption and 2 adds new insights to support the hypothesis of the injection of a second aborted dyke 2 km se from the fractures zone

full moment tensor retrieval from waveform inversion in the larderello geothermal area the area is characterized by numerous events with small magnitude the duration magnitude m d of the events which occurred from 1977 to 1994 varies from 0 5 to 3 5 the algorithm developed by and allows us to retrieve the full source moment tensor from waveform inversion the factorization of the moment tensor rate functions into a source mechanism and a source time function and the further decomposition into a double couple a compensated linear vector dipole and a volumetric component allows us to determine if there are phenomena in the source that can be related to the circulation of fluids a quite common event in geothermal areas

phase altimetry with dual polarization gnss r over sea ice this paper evaluates the potential use of reflected signals from global navigation satellite systems as a source of opportunity for the retrieval of absolute ellipsoidal heights over sea ice accurate estimation of the surface level would be helpful for the determination of the ice thickness a key parameter for classification and characterization of sea ice masses our analysis is based on altimetric estimations from the coherent differential phase between direct and both cross and co polar reflected signals for this purpose gps waveforms have been collected from a fixed platform in greenland monitoring the complete process of sea ice formation and melting during a 7 month period the variability of coherent phase samples and polarimetric measurements are compared with in situ observations to make a realistic rough characterization of the ice cover the retrieved sea ice surface height estimates are then evaluated against an arctic tide model ice surface temperature from moderate resolution imaging spectroradiometer and the laser altimetry product from icesat

forearc tectonic evolution of the south shetland margin antarctic peninsula the main provinces of the south shetland margin antarctic peninsula characterized on the basis of multichannel seismic long range side scan sonar and swath bathymetry data include from northwest to southeast 1 the oceanic crust of the former phoenix plate flexed down toward the margin and affected by normal faulting in the upper crust 2 a narrow trench with a horizontally layered sediment fill which onlaps the thin sedimentary cover on the oceanic crust and shows incipient deformation near its landward edge 3 an accretionary prism with a complex internal structure the toe of which is overthrust above the youngest trench deposits 4 a midslope forearc basin with an asymmetric synformal structure and 5 the continental shelf which includes two distinct tectonic provinces calculations of the late cenozoic convergence history at the trench indicate a rapid decrease in convergence rate after 6 7 ma from about 60 mm yr resulting from the slowing and eventual cessation of spreading on the antarctic phoenix ridge once spreading had completely ceased 3 5 2 4 ma the convergence rate at the trench equalled the rate of extension in bransfield strait which was probably less than 10 mm yr at first but may have increased since 1 3 ma and this in turn would imply a corresponding increase in convergence rate above the basal detachment the toe of the accretionary prism is composed of a stack of thrust fault bounded wedges laterally and vertically segmented by normal faults most of the trench fill sediments are overthrust by the toe of the accretionary prism and subducted beneath it for as far as they can be traced on the seismic profiles this suggests that there may be tectonic erosion of the forearc since a large part of the trench sediment appears to be derived from erosion on the forearc slope the forearc basin records a long history of subsidence during which the depocenter migrated landward paralleling retrogradational erosion of the distal margin of the basin subduction of the hero fracture zone at approximately the same location since 10 ma may have enhanced tectonic erosion of the accretionary prism in the forearc basin a synform is coincident with a bathymetric reentrant but its axis is oblique to the trends of both the basin and the fracture zone the origin of this synform and the final phase of uplift of the blueschist facies terrane on which smith island stands are probably related to their position above the subducting fracture zone ridge the present elevation of smith island is thought to result from uplift which followed a ridge crest trench collision directly southwest of the hero fracture zone at 5 5 ma the northwestern edge of the mesozoic to early cenozoic arc batholith trending northeast southwest on the shelf is proposed to have acted as a backstop to the accretionary prism during cenozoic subduction

detection of arctic ocean tides using interferometric gnss r signals 1 this paper evaluates the usage of reflected gps signals for earth observations to study changes of sea level and sea ice in remote sensing in a coastal setup 670 m above disko bay greenland signals with different carriers l1 and l2 were recorded a method is presented that analyses the interferometric phase between the reflected and the direct signals and derives the height of the reflecting surface the analysis includes a ray tracing and an estimation of signal coherence it is shown that coherent reflections are related to sea ice coverage absolute heights are derived with a time interval of 30 min the altimetric results show semidiurnal tides that are validated using the aodtm 5 tide model the residual height has a mean of 9 7 cm for l1 and 22 9 cm for l2 the dispersion is not significant but a significant tropospheric bias is detected with an error of up to 20 cm

seismotectonics and relative plate motions in the scotia sea region source parameter inversion of p and sh waveforms and amplitudes for 20 shallow earthquakes using a singular value decomposition technique provides important constraints on the tectonics and relative plate motions of the scotia sea region the derived focal mechanisms show both thrust and strike slip faulting along the north scotia ridge and normal and strike slip faulting along the south scotia ridge two thrust faulting mechanisms south of tierra del fuego indicate diffuse convergence of the antarctic plate along the western margin of the scotia plate earthquakes are consistent with active subduction and back arc spreading along the south shetland trench and bransfield strait the depths of two earthquakes 35 km and 55 km and one shallow thrust faulting event suggest continued subduction along the south shetland trench but the underthrusting is largely aseismic due to the young plate age and slow subduction rate the magnitude and depth of normal faulting earthquakes along bransfield strait and the south scotia ridge are suggestive of diffuse extension rather than typical organized mid ocean spreading which is generally associated with smaller and shallower earthquakes eight strike slip and thrust faulting events provide well constrained slip vectors showing scotia plate motion relative to the surrounding larger plates using a four plate model scotia sc south sandwich ss antarctica an and south america sa and a fixed sa an euler vector we inverted these data together with published centroid moment tensor slip vectors along the south sandwich trench and published marine magnetic data from the ss back arc spreading center to derive the first quantitative plate motion model for the scotia region the sc sa euler pole is located in the south atlantic and shows large latitudinal uncertainties the sc an pole is better constrained and located in the weddell sea these results predict left lateral strike slip motion with a component of compression along the north scotia ridge left lateral strike slip with a component of extension along the south scotia ridge and east west compression in drake passage although no rate data have been published connecting the scotia plate with the global plate system euler vector magnitudes are obtained through closure the results though poorly constrained suggest relative motion rates of 0 5 cm yr along the north scotia ridge and 1 0 cm yr along the south scotia ridge and in drake passage

waveform inversion for point source moment tensor retrieval with variable hypocentral depth and structural model summary in the inversion scheme of high frequency seismograms recorded by a local network we have developed the unconstrained moment tensor description to study weak events which are believed to reflect small scale complexities of the tectonic structure in order to allow the source mechanism to change with time each moment tensor component has its own time history in the inversion the measure of the similarity between the synthetic seismograms and the observed records is obtained by minimizing the norm l2 of their difference the initial synthetic seismograms are constructed by summing a set of time dependent functions named base functions these base functions are computed by normal mode summation for a discrete set of source depths and for two structural models considered to represent acceptable extremes for the region under study in the course of the inversion using a linear interpolation new base functions are computed for intermediate values of the starting depths and structures thereafter new synthetic seismograms are computed and compared with the observed records until the convergence is reached within some pre assigned threshold for the norm l2 the method has been tested by treating as observed records synthetic seismograms both displacement and velocity generated for instantaneous and finite duration sources the observed records have been computed for two structures one belonging to the structural range within which the base functions were computed the other lying outside this range random noise has been superimposed on the records when inverting synthetic records computed for a structure contained within the range of interpolation for the base functions the full moment tensor is retrieved satisfactorily provided that the noise level does not exceed about 20 per cent for records computed for a structure lying outside this range a spurious volumetric part of the moment tensor appears however if the volumetric part of the moment tensor is removed the source time function can be reconstructed satisfactorily and the source mechanism can be determined from the deviatoric part of the moment tensor the procedure has been applied to vertical component seismograms recorded in the friuli ne italy area for the ml 2 9 event of 1987 december 27 the retrieved source mechanism is in agreement with the distribution of the few first arrival polarities available and the source time function indicates a possible multiple rupture process

intermediate focus earthquakes under south shetland islands antarctica this study is based on data from five field surveys 1992 1996 of seismic monitoring on deception island south shetland islands antarctica in the 1994 95 and 1995 96 surveys earthquakes were recorded by a seismic array in previous surveys data were collected by a high dynamic range short period station the analysis of the events shows evidence of intermediate focus seismicity 50 h 100 km related to the underplating zone of the south shetland plate because of poor station coverage we had to use unconventional techniques to locate the events such as zero lag cross correlation method that provide information about apparent velocity and back azimuth ray tracing procedure and particle motion patterns these criteria allowed us to identify 15 earthquakes that could be considered as intermediate focus events for which some focal parameters were estimated we conclude that the subduction zone between the drake plate and south shetland microplate has a moderate level of intermediate depth microseismicity

global mapping functions for the atmosphere delay at radio wavelengths i have developed expressions for calculating the ratios mapping functions of the line of sight hydrostatic and wet atmospheric path delays to their corresponding zenith delays at radio wavelengths for elevation angles down to 3 the coefficients of the continued fraction representation of the hydrostatic mapping function depend on the latitude and height above sea level of the observing site and on the day of the year the dependence of the wet mapping function is only on the site latitude by comparing with mapping functions calculated from radiosonde profiles for sites at latitudes between 43 s and 75 n the hydrostatic mapping function is seen to be more accurate than and of comparable precision to mapping functions currently in use which are parameterized in terms of local surface meteorology when the new mapping functions are used in the analysis of geodetic very long baseline interferometry vlbi data the estimated lengths of baselines up to 10 400 km long change by less than 5 mm as the minimum elevation of included data is reduced from 12 to 3 the independence of the new mapping functions from surface meteorology while having comparable accuracy and precision to those that require such input makes them particularly valuable for those situations where surface meteorology data are not available

determination of the seismic moment tensor for local events in the south shetland islands and bransfield strait we present the results of the analysis for a set of earthquakes recorded in the bransfield strait and the south shetland islands in the period 1997 1998 to determine focal mechanisms and source time functions events with magnitudes between 3 and 5 6 have been analysed and the source parameters have been retrieved using a robust methodology inpar that allows the reliable inversion of a limited number of noisy records this methodology is particularly important in oceanic environments where the presence of seismic noise and the small number of stations makes it difficult to analyse small magnitude events

2 cm gps altimetry over crater lake dierences in electromagnetic path delay be tween direct global positioning system gps signals and those reflected from the surface of crater lake have led to lake surface height estimates with 2 cm precision in 1 sec ond this is the rst high precision altimetric demonstra tion with gps from sucient altitude 480 m to probe fundamental experimental errors which bear on future air and spaceborne passive gps altimetry it also serves as the rst demonstration of a new approach to altimetric remote sensing in the coastal region an area that is poorly mea sured by conventional radar altimetry time series analy sessuggest thattroposphericandthermalnoisefluctuations dominate the altimetric error in this experiment estimat ing the dierential delay from several simultaneously visi ble satellites may enable tropospheric error estimation and correction thermal noise on the reflected signal will be reduced with fully polarimetric observations and larger an tenna apertures

searchlight precipitation advection tracking using multiplatform low earth orbiting satellite data this paper presents a new algorithm searchlight capable of tracking precipitation advection through the complex spatiotemporal sampling pattern of multiplatform low earth orbiting leo passive and active microwave satellite data sets the algorithm is based on the concept of shining a searchlight forward in time along proposed advection velocity vectors from a given leo overpass the searchlight beam links precipitation patterns in the current satellite overpass to corresponding patterns in multiple future overpasses a global optimization determines an advection model by maximizing mutual information between linked precipitation measurements the algorithm has been validated against surface radar over a region covering the central and eastern u s

group velocity tomography in the subantarctic scotia sea region more than 150 events recently recorded by seven seismic broadband stations ogs iaa iris gsett3 idc have been collected and processed to obtain an overview of the crust and upper mantle shear wave velocities group velocities of the fundamental mode rayleigh and love waves in the period range from 15 s to 50 s are used to obtain tomographic maps of the scotia sea region the tip of antarctic peninsula and the tip of south america errors in the measurements estimated on clusters are larger for love waves than for rayleigh waves and their averages are 0 060 0 080 km s and 0 030 0 040 km s respectively from the regionalisation of the dispersion measurements we obtain smoothed local dispersion curves in correspondence with the main geological and tectonic features and from their nonlinear inversion the shear wave velocity versus depth profiles the correlation length of the heterogeneity which can be resolved by rayleigh waves varies between 200 and 400 km in most parts of the studied area but becomes greater near the periphery of the maps the spatial resolution of love waves 400 600 km is poorer than that of rayleigh waves due to the deteriorated path coverage and to the larger errors in the group velocity measurements models of the shear wave velocity in the crust and upper mantle for the tip of south america the falkland plateau the scotia sea the south sandwich oceanic spreading ridge the south sandwich trench the south scotia ridge the tip of antarctic peninsula the bransfield strait and the drake passage are presented our regional models and the existing large scale models e g crust5 1 help to define a 3 d velocity model of the scotia sea region to be further investigated by waveform inversion