use of psinsar data to infer active tectonics clues on the differential uplift across the giudicarie belt central eastern alps italy abstract the permanent scatterers synthetic aperture radar interferometry psinsar methodology provides high resolution assessment of surface deformations precision ranging from 0 8 to 0 1 mm year over long periods of observation hence it is particularly suitable to analyze surface motion over wide regions associated to a weak tectonic activity for this reason we have adopted the psinsar technique to study regional movement across the giudicarie belt a nne trending trust belt oblique to the southern alpine chain and presently characterized by a low to moderate seismicity over 11 000 ps velocities along the satellite line of sight los were calculated using images acquired in descending orbit during the 1992 1996 time span the psinsar data show a differential uplift of around 1 4 1 7 mm year across the most external wnw dipping thrusts of the giudicarie belt mt baldo mt stivo and mt grattacul thrusts alignment this corresponds to a horizontal contraction across the external part of the giudicarie belt of about 1 3 1 5 mm year

rupture parameters of the 2003 zemmouri mw 6 8 algeria earthquake from joint inversion of interferometric synthetic aperture radar coastal uplift and gps 1 we study the surface deformation associated with the 21 may 2003 mw 6 8 zemmouri algeria earthquake the strongest seismic event felt in the algiers region since 1716 the thrust earthquake mechanism and related surface deformation revealed an average 0 50 m coastal uplift along 55 km long coastline we obtain coseismic interferograms using envisat advanced synthetic aperture radar asar is2 and radarsat standard beam st4 data from both the ascending and descending orbits of envisat satellite whereas the radarsat data proved useful only in the descending mode while the two radarsat interferograms cover the earthquake area envisat data cover only the western half of the rupture zone although the interferometric synthetic aperture radar insar coherence in the epicenter area is poor deformation fringes are observed along the coast in different patches in the boumerdes area the maximum coseismic deformation is indicated by the high gradient of fringes visible in all interferograms in agreement with field measurements tape differential gps leveling and gps to constrain the earthquake rupture parameters we model the interferograms and uplift measurements using elastic dislocations on triangular fault patches in an elastic and homogeneous half space we invert the coseismic slip using first a planar surface and second a curved fault both constructed from triangular elements using poly3dinv program that uses a damped least square minimization the best fit of insar coastal uplift and gps data corresponds to a 65 km long fault rupture dipping 40 to 50 se located at 8 to 13 km offshore with a change in strike west of boumerdes from n60 65 to n95 105 the inferred rupture geometry at depth correlates well with the seismological results and may have critical implications for the seismic hazard assessment of the algiers region

ice front variations and speed changes of calving glaciers in the southern patagonia icefield from 1984 to 2011 patagonian icefields are losing volume and their loss is due partly to rapid changes in their outlet glaciers that terminate in lakes or the ocean despite this key influence from outlet glaciers relatively few of these calving glaciers have had high frequency measurements on their frontal variations and ice speed changes we describe here recent frontal variations and ice speed changes of all 28 major calving glaciers in the southern patagonia icefield spi including ice speed maps covering approximately half of the entire icefield the analysis is based on satellite data from 1984 to 2011 over this period only the two termini of glaciar pio xi advanced of the remaining glacial fronts 12 changed less than 0 5 km but 17 retreated at least 0 5 km in the latter group three glacial fronts glaciar jorge montt hps12 and upsala retreated over 6 km averaged over all 31 glacial fronts of the calving glaciers the front positions retreated 1 56 km median is 0 71 km along the flowline within 20 km of the front the ice speeds up to 5900 200 m a 1 except for regions showing large acceleration or deceleration the mean speed over the measured area decreased by 30 m a 1 from 1984 to 2011 the three most rapidly retreating glaciers showed much larger acceleration near the calving front suggesting that ice dynamics drive their rapid retreat thus we see retreat as a long term trend for the calving glaciers in the spi with behavior that implies a dynamically controlled rapid recession that may explain the recently reported volume change of the spi

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

ice elevation changes of glaciar chico southern patagonia using aster dems aerial photographs and gps data hielo patagonico sur hps southern patagonia icefield is the largest temperate ice mass at mid latitudes in the southern hemisphere with few exceptions the glaciers in this region have been retreating during the last 50 years based on field data vertical aerial photographs and satellite images ice elevation changes since 1975 on glaciar chico one of the main tongues of hps are presented a maximum ice thinning of 5 4 0 55 m a 1 was observed at the glacier front between 1975 and 1997 global positioning system gps data were used in the accumulation area of the glacier to infer a thinning rate of 1 9 0 14 m a 1 between 1998 and 2001 this thinning rate is three times higher than the snow accumulation rate estimated for that part of the glacier a mean net glacier mass balance of 0 29 0 097 km 3 w e a 1 was estimated between 1975 and 2001 climate data suggest an increase in temperature and a reduction in precipitation during most of the 20th century in the vicinity of hps although these climate changes are the primary explanation for the observed ice elevation changes of the glacier ice dynamics effects are also believed to play an important role

imaging the growth of recent faults the case of 2016 2017 seismic sequence sea bottom deformation in the alboran sea western mediterranean

rapid retreat acceleration and thinning of glaciar upsala southern patagonia icefield initiated in 2008 the patagonia icefields are characterized by a large number of outlet glaciers calving into lakes and the ocean in contrast to the recent intensive research activities on tidewater glaciers in other regions very few observations have been made on calving glaciers in patagonia we analysed satellite images of glaciar upsala the third largest freshwater calving glacier in the southern patagonia icefield to investigate changes in its front position ice velocity and surface elevation from 2000 to 2011 our analyses revealed a clear transition from a relatively stable phase to a rapidly retreating and fast flowing condition in 2008 the glacier front receded by 2 9 km and the ice velocity increased by 20 50 over the 2008 11 period we also found that the ice surface lowered at a rate of up to 39 m a 1 from 2006 to 2010 this magnitude and the rate of changes in the glacier front position ice velocity and surface elevation are greater than previously reported for glaciar upsala and comparable to recent observations of large tidewater glaciers in greenland our data illustrate details of a rapidly retreating calving glacier in patagonia that have been scarcely reported despite their importance to the mass budget of the patagonia icefields

buoyancy driven lacustrine calving glaciar nef chilean patagonia glaciar nef a 164 km 2 eastern outlet of hielo patagonico norte the northern patagonia icefield terminates in a proglacial lake that has formed in conjunction with 20th century glacier retreat the terminus is inferred to be transiently afloat a hinge calving mechanism is proposed in which buoyant forces impose a torque on the glacier tongue resulting in the release of coherent sections of the glacier tongue as tabular icebergs a simple model shows how torque and tensile stress reach a maximum at the up glacier limit of the buoyant zone and that glacier thinning causes this point to migrate up glacier empirical evidence supporting this model includes elevated thermo erosional notches 6 5 m above lake level and the ubiquitous presence since 1975 of tabular icebergs with surface areas 0 3 km 2 flow speeds of 1 2 1 3 m d 1 were measured near the terminus in february 1998 extrapolations from these short term data yield a calving rate of 785 835 m a 1 and a calving flux of 232 10 6 m 3 a 1 or 0 2 km 3 a 1 the calculated mean water depth at the terminus is 190 m this calving rate is higher than at grounded temperate glaciers calving in fresh water but is nevertheless almost an order of magnitude less than calving rates at both grounded and floating tidewater glaciers

ice volumetric changes on active volcanoes in southern chile most of the glaciers in southern chile have been retreating and shrinking during recent decades in response to atmospheric warming and decrease in precipitation however some glacier fluctuations are directly associated with the effusive and geothermal activity of ice covered active volcanoes widely distributed in the region the aim of this paper is to study the ice volumetric changes by comparing several topographic datasets a maximum mean ice thinning rate of 0 81 0 45 m a 1 was observed on the ash debris covered ablation area of volcan villarrica between 1961 and 2004 whilst on volcan mocho the signal to noise ratio was too small to yield any conclusion an area reduction of 0 036 0 019 km 2 a 1 since 1976 was obtained on glaciar mocho while on volcan villarrica the area change was 0 090 0 034 km 2 a 1 between 1976 and 2005 glaciers on active volcanoes are therefore shrinking mainly in response to climatic driving factors however volcanic activity is affecting glaciers in two opposite ways ash debris advection is helping to reduce surface ablation at lower reaches by insulating the ice from solar radiation while geothermal activity is probably enhancing melting and water production at the bedrock resulting in negative ice elevation changes

the al hoceima earthquake sequence of 1994 2004 and 2016 stress transfer and poroelasticity in the rif and alboran sea region

lithologic and climatologic controls of river chemistry abstract the chemistries of rivers draining a variety of lithologic and climatic regions have been surveyed for the purpose of quantifying the fluxes of bicarbonate and silica from rivers with respect to bedrock lithology and runoff in all 101 different rivers each draining a primary lithology were examined across the united states puerto rico and iceland to minimize seasonal effects only rivers with at least two years of data were used basaltic catchments were examined in the greatest detail in a survey of hawaiian island watersheds the average river chemistries could be related to the distribution of soil associations within each catchment an analysis of cation activity relationships among rivers draining basaltic catchments shows that the river compositions define slopes which are consistent with an equilibrium ion exchange control on cation ratios among different lithologies unique weathering rate relationships were developed with yields at typical present day runoff rates 1 100 cm y increasing in the order sandstones granites basalts shales and carbonates the bicarbonate and silica fluxes for each of these lithologies have been quantified for use in global studies of chemical denudation our study confirms that the dissolved yield of a given drainage basin is determined by a balance between physical and chemical weathering thus a warm wet climate or the presence of abundant vegetation cannot guarantee high rates of chemical denudation unless accompanied by high rates of physical removal

goringe alboran tell tectonic zone a transpression system along the africa eurasia plate boundary neotectonic structures distributed from the goringe bank to the tell atlas mountains show that the africa eurasia plate boundary in the western mediterranean corresponds to an east west trending deforming zone goringe alboran tell main pliocene and quaternary tectonic structures of the northern atlas mountains are northeast southwest striking fault related folds similar to that of el asnam and are related to north south to northwest southeast compressional movements active tectonics in agreement with the main seismicity distribution and focal mechanisms also support an oblique plate convergence and the existence of a 50 100 km wide transpression zone from goringe across alboran to the tell atlas mountains a kinematic model shows the interaction between dextral transcurrent faults and left lateral faults with block rotations and no lateral extension pinned model shortening and lateral movement rates during the quaternary are estimated to be 1 0 2 3 mm yr and block rotation rate is estimated as 2 5 3 9 m y the plate boundary may correspond to a transpression zone active thrust faults being controlled by deep seated dextral transcurrent faults

short term variations in flow velocity of glaciar soler patagonia chile short term variations in ice flow velocity were obtained at intervals of a few hours and a few days in the ablation area of glaciar soler patagonia chile in november 1985 a maximum flow rate was measured at about four times the minimum value a good correlation with a time lag of 7 5 h was found between the ice flow velocity in the lower reaches and the amount of water discharge from the glacier terminus it was concluded therefore that the velocity variations should have resulted from the variations in basal sliding velocity which is strongly controlled by the subglacial water pressure

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

contrasting glacier variations of glaciar perito moreno and glaciar ameghino southern patagonia icefield glaciar perito moreno gpm and glaciar ameghino ga southern patagonia icefield are in contact in the accumulation area but have shown contrasting frontal variations in the past few decades to investigate recent changes of the two glaciers and processes controlling the different responses to similar climate conditions we measured surface elevation change from 2000 to 2008 and terminus positions from 1999 to 2012 using several types of satellite data gpm shows no significant changes in terminus position and 0 4 0 3ma 1 thickening over the period whereas ga retreated 55 2ma 1 and thinned 2 6 0 3ma 1 mass balance measurements over the period 1999 2000 show that accumulation at gpm was ten times greater than that at ga but ablation was only three times greater the mass balance altitude profile is similar for the two glaciers differences in the mass balance distribution are caused by differences in the accumulation area ratio aar our results suggest that the aar and the calving flux exert strong control on the evolution of glaciers in the region

microearthquake seismicity and fault plane solutions around the nekor strike slip fault morocco abstract three hundred and twenty eight earthquakes recorded in the course of 5 weeks in 1989 in the central rif of northern morocco provided no evidence for activity on the nekor fault the principal geological structure in the region itself most of the seismicity is located northwest of the nekor fault most of the 41 fault plane solutions show mainly strike slip motion left lateral on n s striking planes with p axes trending n145 this deformation is consistent with the n s trending normal faults caused by the e w quaternary extension and with the present relative nw se convergence between africa and europe the active deformation around the eastern rif is better represented by a distributed shear zone than by a strike slip fault

multifaulting in a tectonic syntaxis revealed by insar the case of the ziarat earthquake sequence pakistan on 28 29 october 2008 within 12 h two similar mw 6 4 strike slip earthquakes struck baluchistan pakistan as part of a complex seismic sequence interferometric synthetic aperture radar insar data reveal that the peak of surface displacement is near the ziarat anticline a large active fold affected by quaternary strike slip faulting all coseismic interferograms integrate the deformation due to both earthquakes as their causative faults ruptured close to each other the individual signals cannot be separated according to their focal mechanisms each earthquake may have activated a ne sw sinistral or a nw se dextral fault segment which leads to four possible scenarios of fault orientations a nonlinear inversion of the insar data set allows rejecting two scenarios the best slip distributions on the two fault segments for the two remaining scenarios are determined by linear inversion stress change modeling favors a scenario involving two abutting conjugate strike slip faults two other fault segments accommodated left lateral strike slip during the seismic sequence the activated fault system includes multiple fault segments with different orientations and little surface expression this may highlight at a smaller scale the distributed possibly transient character of deformation within a broader right lateral shear zone it suggests that the activated faults delineate a small tectonic block extruding and subtly rotating within the shear zone it occurs in the vicinity of the local tectonic syntaxis where orogenic structures sharply turn around a vertical axis these mechanisms could participate in the long term migration of active tectonic structures within this kinematically unstable tectonic syntaxis

chemical weathering in glacial environments do glaciers enhance or inhibit chemical weathering rates relative to other environments the importance of glaciers in the global carbon cycle and climate change hinges on the answer we show that catchments occupied by active alpine glaciers yield cation denudation rates greater than the global mean rate but do not exceed rates in nonglacial catchments with similar water discharge silica denudation rates are distinctly lower in glacier covered catchments than in their nonglacial counterparts because sediment yields are high from glaciers this suggests that water flux rather than physical erosion exerts the primary control on chemical erosion by glaciers potassium and calcium concentrations are high relative to other cations in glacial water probably due to dissolution of soluble trace phases such as carbonates exposed by comminution and cation leaching from biotite preferential weathering of biotite may result in higher 87 sr 86 sr in glacial runoff than expected from whole rock compositions thus although glaciers do not influence total chemical denudation rates at a given runoff they may yield compositionally distinctive chemical fluxes to the oceans disruption of mineral lattices by grinding increases dissolution rates this and high surface area should make glacial sediments exceptionally weatherable weathering of glacial erosion products in environments beyond the glacier margin deserves attention because it may figure prominently in global chemical cycles

fast tidewater glaciers some iceberg calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets no temperate tidewater glaciers are known to have floating termini but many polar and subpolar tidewater glaciers do the fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed which may approach zero and the longitudinal back stress on the terminus the terminus boundary condition the calving relation is imperfectly known yet is vital to the dynamics of these glaciers calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested the calving relations for floating termini are virtually unknown this together with the imperfect understanding of basal sliding inhibits confidence in our understanding of the stability of these glaciers columbia glacier alaska is an instructive example because observations have been made on the major changes in its geometry calving rate and dynamics that have occurred in less than 10 years the calving flux has increased more rapidly than the glacier flux causing thinning and retreat as a result the ice velocity has increased markedly the short term velocity changes relate to changes in back pressure ice recession tidal changes and the flux of water injected to the bed these results have relevance to the mechanisms of basal sliding glacier surges and the stability of marine ice streams

are the seismological and geological observations of the al hoceima morocco rif 2004 earthquake m 6 3 contradictory abstract seismic hazard is associated with recent and present fault activity in mountain ranges in the betic rif alpine mountain chain tectonic activity started in the cretaceous and topographic uplift continues since tortonian times as a consequence of the nw se oblique convergence between africa and eurasia the deformation is active and produces seismicity that sometimes has catastrophic consequences the al hoceima earthquake february 24 2004 considered one of the largest earthquakes ever recorded instrumentally in the westernmost mediterranean m 6 3 caused great damage in the region seismological studies agree that the main shock was situated on land at the limit between the external and internal zones of the rif at a depth of 10 14 km the focal mechanism points to a strike slip solution with a nw se oriented p axis quite similar to those of the significant 1994 earthquake swarm located to the north the epicenter aftershocks distribution would signal the presence of a n s oriented sinistral fault activated by the nw se regional compression associated to plate boundary convergence in this setting the seismogenic fault ruptures related to these seismic events are expected to have reached the earth s surface however detailed field work carried out 1 month after the earthquake does not evidence any n s strike slip coseismic fault in the epicentral area the main observed effects were landslides damages to constructions and locally open cracks indicating an unexpected nw se extension scarce n s faults are normal the main ones being located several kilometers away from the epicentral area to explain this apparent contradiction between geological and seismological observations we propose a decoupled tectonic model with crustal detachments that separate a deep brittle crust from an upper crust undergoing uplift and the development of large folds and normal faults this geological setting common to internal zones of cordilleras may need to be taken into account in future paleoseismicity studies and in the assessment of seismic hazard

seismicity and active tectonics in the alboran sea western mediterranean constraints from an offshore onshore seismological network and swath bathymetry data seismicity and tectonic structure of the alboran sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in spain and morocco an area where the convergence between the african and eurasian plates causes distributed deformation crustal structure derived from local earthquake data suggests that the alboran sea is underlain by thinned continental crust with a mean thickness of about 20 km during the 5 months of offshore network operation a total of 229 local earthquakes were located within the alboran sea and neighboring areas earthquakes were generally crustal events and in the offshore domain most of them occurred at crustal levels of 2 to 15 km depth earthquakes in the alboran sea are poorly related to large scale tectonic features and form a 20 to 40 km wide nne ssw trending belt of seismicity between adra spain and al hoceima morocco supporting the case for a major left lateral shear zone across the alboran sea such a shear zone is in accord with high resolution bathymetric data and seismic reflection imaging indicating a number of small active fault zones some of which offset the seafloor rather than supporting a well defined discrete plate boundary fault moreover a number of large faults known to be active as evidenced from bathymetry seismic reflection and paleoseismic data such as the yusuf and carboneras faults were seismically inactive earthquakes below the western alboran basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere

new paleomagnetic data from oligocene upper miocene sediments in the rif chain northern morocco insights on the neogene tectonic evolution of the gibraltar arc 1 in this paper we present new paleomagnetic data from tertiary sedimentary sequences of the rif chain paleomagnetic results show that the rif chain underwent different patterns of vertical axis rotations depending on the tectonic location of the sampled sites whereas no paleomagnetic rotations have been measured either in the upper miocene postnappe basins located along the mediterranean coast or in the upper miocene fes taza foreland basins upper miocene thrust top sequences from the external rif show a significant amount 20 13 in average of counterclockwise rotations the spatial distribution of paleomagnetic rotations shows that tectonic rotations as observed in other arcs of the mediterranean region are confined to the orogenic wedge and do not extend to the foreland domain paleomagnetic results from this study contribute to better constrain the age of paleomagnetic rotations in the rif chain showing that counterclockwise rotations previously measured only in mesozoic units extended into upper miocene deposits these results together with recent published data from the betics suggest that the bending of the gibraltar arc was not completely achieved by the late tortonian messinian enhancing the role of vertical axis rotations in the late miocene to recent tectonic evolution of the gibraltar arc

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

flow of glaciar moreno argentina from repeat pass shuttle imaging radar images comparison of the phase correlation method with radar interferometry high resolution radar images of glaciar moreno argentina acquired by the shuttle imaging radar c sir c on 9 and 10 october 1994 at 24 cm wavelength l band are utilized to map the glacier velocity both interferometrically and using the phase correlation method the precision of the interferometric ice velocities is 1 8 cm d 1 6 m a 1 1 the phase correlation method measures ice velocity with a precision of 14 cm d 1 50 m a 1 with image data at a 6 m sample spacing acquired 1 day apart averaged strain rates are measured with a precision of 10 4 d 1 at a 240 m sample spacing with the phase correlation method and 10 5 d 1 with radar interferometry the phase correlation method is less precise than radar interferometry but it performs better in areas of rapid flow is more robust to temporal changes in glacier scattering and measures the glacier velocity in two dimensions with only one image pair using this technique we find that glaciar moreno flows at 400 m a 1 in the terminal valley and 800 m a 1 at the calving front in agreement with velocities recorded a decade ago assuming steady state flow conditions the vertical strain rates measured by sir c are combined with prior data on mass ablation to estimate the glacier thickness and ice discharge the calculated discharge is 0 6 0 2 km3 ice a 1 at 300 m elevation and 1 1 0 2 km3 ice a 1 at the equilibrium line elevation 1150 m which yields a balance accumulation of 6 1m ice a 1

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

models of active glacial isostasy roofing warm subduction case of the south patagonian ice field 1 modern geodetic techniques such as precise global positioning system gps and high resolution space gravity mapping gravity recovery and climate experiment grace make it possible to measure the present day rate of viscoelastic gravitational earth response to present and past glacier mass changes the andes of patagonia contain glacial environments of dramatic mass change these mass load changes occur near a tectonically active boundary between the antarctic and south american plates the mechanical strength of the continental side of this boundary is influenced by neogene ridge subduction and by the subduction of a youthful oceanic slab a ridge of young volcanos parallels the pacific coastline release of volatiles such as water at depth along this ridge creates a unique rheological environment to assess the influence of this rheological ridge structure on the observational land uplift rate we apply a two dimensional viscoelastic earth model a numerical study is presented which examines the sensitivity of the glacial loading unloading response to the complex structure at depth related to the subducting slab the viscous wedge between slab and continental lithosphere and the increase of elastic thickness from oceanic to continental lithosphere a key feature revealed by our numerical experiments is a continuum flow wherein the slab subdues the material transport toward oceanic mantle and crust the restricted flow is sensitive to the details of slab mechanical strength and penetration into the upper mantle the reduced viscosity within the mantle wedge however enhances the load induced material transport everywhere within the asthenosphere

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

synthetic aperture radar interferometry observations of the m 6 0 orta earthquake of 6 june 2000 nw turkey reactivation of a listric fault we study the coseismic surface displacement field due to the orta earthquake of 6 june 2000 a moderate sized mw 6 0 oblique slip event that took place on a previously unknown fault located about 70 km north of the capital ankara turkey and about 35 km south of the north anatolian fault we use european space agency ers synthetic aperture radar sar data to generate high resolution maps of the surface displacements by a two pass differential sar interferometry method the surface displacement field reaching up to 15 cm line of sight subsidence is captured in several coseismic interferograms from descending orbits and is inverted to determine the source parameters of the earthquake using elastic dislocations on rectangular fault surfaces with a nonlinear minimization procedure based on simulating annealing algorithm modeling of the coseismic interferograms indicates that the earthquake was associated with a shallow 6 km left lateral oblique normal displacement that occurred on a north south striking eastward dipping listric fault trending at a high angle to the plate boundary right lateral strike slip north anatolian fault careful analyses of multiple interferograms together with the field observations allow us to infer the rupture geometry in fine detail modeling shows that coseismic slip occurs nearly only on the lower portion of the listric fault at a centroid depth of about 5 km but partially reaches to the surface along the surface trace of the dodurga fault in agreement with the field observations we show that in the absence of field observations additional measurements or multiple interferograms that capture the surface deformation from different look angles sar interferometry alone may not be sufficient to constrain earthquake rupture geometry if there is no clear surface faulting the results suggest that the dodurga fault developed most probably as a result of a restraining bend along the north anatolian fault and its left lateral kinematics is consistent with the stress regime that favors the right lateral north anatolian fault

a model for atmospheric co 2 over phanerozoic time a new model has been constructed for calculating the level of atmospheric co sub 2 over phanerozoic time which is much simpler mathematically than the blag model but more complex geologically and biologically results suggest that there has been a notable pattern of varying atmospheric co sub 2 level over the past 570 my with high levels during the mesozoic and early paleozoic and low levels during the permo carboniferous and late cenozoic sensitivity analysis shows that within reasonable limits of the principal governing parameters this qualitative trend of varying co sub 2 is relatively insensitive to the actual values chosen for these parameters causes of the co sub 2 variation are multiple and no single geological or biological process can be called upon to explain all co sub 2 variation for all time the calculated trend of co sub 2 over time agrees well with independent estimations of paleoclimates thus the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

erosional and climatic effects on long term chemical weathering rates in granitic landscapes spanning diverse climate regimes abstract we used cosmogenic nuclide and geochemical mass balance methods to measure long term rates of chemical weathering and total denudation in granitic landscapes in diverse climatic regimes our 42 study sites encompass widely varying climatic and erosional regimes with mean annual temperatures ranging from 2 to 25 c average precipitation ranging from 22 to 420 cm year 1 and denudation rates ranging from 23 to 755 t km 2 year 1 long term chemical weathering rates range from 0 to 173 t km 2 year 1 in several cases exceeding the highest granitic weathering rates on record from previous work chemical weathering rates are highest at the sites with rapid denudation rates consistent with strong coupling between rates of chemical weathering and mineral supply from breakdown of rock a simple empirical relationship based on temperature precipitation and long term denudation rates explains 89 95 of the variation in long term weathering rates across our network of sites our analysis shows that for a given precipitation and temperature chemical weathering rates increase proportionally with fresh material supply rates we refer to this as supply limited weathering in which fresh material is chemically depleted to roughly the same degree regardless of its rate of supply from breakdown of rock the temperature sensitivity of chemical weathering rates is two to four times smaller than what one would expect from laboratory measurements of activation energies for feldspar weathering and previous inter comparisons of catchment mass balance data from the field our results suggest that climate change feedbacks between temperature and silicate weathering rates may be weaker than previously thought at least in actively eroding unglaciated terrain similar to our study sites to the extent that chemical weathering rates are supply limited in mountainous landscapes factors that regulate rates of mineral supply from erosion such as tectonic uplift may lead to significant fluctuations in global climate over the long term

the fluvial geochemistry of the rivers of eastern siberia i tributaries of the lena river draining the sedimentary platform of the siberian craton abstract the response of continental weathering rates to changing climate and atmospheric pco 2 is of considerable importance both to the interpretation of the geological sedimentary record and to predictions of the effects of future anthropogenic influences while comprehensive work on the controlling mechanisms of contemporary chemical and mechanical weathering has been carried out in the tropics and to a lesser extent in the strongly perturbed northern temperate latitudes very little is known about the peri glacial environments in the subarctic and arctic thus the effects of climate essentially temperature and runoff on the rates of atmospheric co 2 consumption by weathering are not well quantified at this climatic extreme to remedy this lack a comprehensive survey has been carried out of the geochemistry of the large rivers of eastern siberia the lena yana indigirka kolyma anadyr and numerous lesser streams which drain a pristine high latitude region that has not experienced the pervasive effects of glaciation and subsequent anthropogenic impacts common to western eurasia and north america the scale of the terrain sampled in terms of area is comparable to that of the continental united states or the amazon orinoco and includes a similarly diverse range of geologic and climatic environments in this paper the chemical fluxes from the western region the very large ancient and geologically stable sedimentary basin precambrian to quaternary of the siberian platform will be presented and compared to published results from analogous terrains in the tropical basins of china while the range in the chemical signatures of the various tributaries included here 60 sampled is large this mainly reflects lithology rather than the weathering environment the areal chemical fluxes are comparable to those of the chinese rivers being dominated by the dissolution of carbonates and evaporites the net consumption of atmospheric co 2 by aluminosilicate weathering is minor as it is in the tropical basins it is much smaller than in active orogenic belts in similar latitudes e g the fraser and yukon but comparable to those of the mackenzie tributaries that drain the eastern slope of the rockies lithology exerts the dominant influence in determining the weathering yield from sedimentary terrains and for a largely carbonate evaporite terrain climate does not have a direct effect

effects of temperature on silicate weathering solute fluxes and chemical weathering in a temperate rain forest watershed jamieson creek british columbia article i nfo article history accepted 7 september 2009 chemical weathering of silicate minerals has long been known as a sink for atmospheric co2 and feedbacks between weathering and climate are believed to affect global climate while warmer temperatures are believed to increase rates of weathering weathering in cool climates can be accelerated by increased mineral exposure due to mechanical weathering by ice in this study chemical weathering of silicate minerals is investigated in a small temperate watershed the jamieson creek watershed is covered by mature coniferous forest and receives high annual precipitation 4000 mm mostly in the form of rainfall and is underlain by quartz diorite bedrock and glacial till analysis of pore water concentration gradients indicates that weathering in hydraulically unsaturated ablation till is dominated by dissolution of plagioclase and hornblende however a watershed scale solute mass balance indicates high relative fluxes of k and ca indicating preferential leaching of these solutes possibly from the relatively unweathered lodgement till weathering rates for plagioclase and hornblende calculated from a watershed scale solute mass balance are similar in magnitude to rates determined using pore water concentration gradients when compared to the rio icacos basin in puerto rico a pristine tropical watershed with similar annual precipitation and bedrock but with dissimilar regolith properties fluxes of weathering products in stream discharge from the warmer site are 1 8 to 16 2 fold higher respectively and regolith profile averaged plagioclase weathering rates are 3 8 to 9 0 fold higher this suggests that the arrhenius effect which predicts a 3 5 to 9 fold increase in the dissolution rate of plagioclase as temperature is increased from 3 4 to 22 c may explain the greater weathering fluxes and rates at the rio icacos site however more modest differences in k and ca fluxes between the two sites are attributed to accelerated leaching of those solutes from glacial till at jamieson creek our findings suggest that under conditions of high rainfall and favorable topography weathering rates of silicate minerals in warm tropical systems will tend to be higher than in cool temperate systems even if the temperate system is has been perturbed by an episode of glaciation that deposits regolith high in fresh mineral surface area

integrating high precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 kozani grevena earthquake greece 1 we integrate high precision aftershock locations with geodetic inverse modeling to create a more complete kinematic model for the kozani grevena earthquake sequence using the double difference algorithm we have improved relative hypocentral locations by a factor of 7 and thus imaged the details of the fault network associated with the seismic sequence the interpreted fault network consists of multiple segments including 1 a master normal fault that strikes nearly due west and dips toward the north at 43 extending from 6 to 15 km depth 2 an upper segment that connects the top of the seismicity to the observed surface ruptures and dips 70 3 hanging wall antithetic faults 4 a more steeply dipping southwest striking linking structure at the southwest end of the rupture and 5 a separate south dipping segment at the southwestern end of the aftershock cluster the imaged fault segment dimensions orientations and geometric relationships are consistent with regional fault patterns using slip inversion on triangular dislocation patches we calculate variable slip on the imaged three dimensional fault network that best fits the surface displacements observed by satellite interferometric synthetic aperture radar insar in our preferred model we find that the majority of slip occurred at depth on the west and southwest striking segments by comparing these results to a planar fault model derived solely from the insar data using nonlinear inversion methods we demonstrate that the three dimensional model improves the fit to the geodetic data while incorporating the observations of surface rupturing and aftershock distributions

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

relationship between tidewater glacier calving velocity and water depth at the calving front an analysis of the relationship between iceberg calving rates and water depth has been completed for 22 tidewater glaciers a linear relationship provides reasonable accuracy with a correlation coefficient of 0 85 for all tidewater glaciers examined whether they be polar or temperate the polar glaciers have a slightly lower calving rate for a given water depth this relationship indicates a lower calving rate for water depths over 50 m than determined by brown and others 1982 it is based only on glaciers or ice streams and cannot be applied to ice shelves

integrating high precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 kozani grevena earthquake greece kinematic model of the kozani earthquake

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

earthquake potential along the northern hayward fault california the hayward fault slips in large earthquakes and by aseismic creep observed along its surface trace dislocation models of the surface deformation adjacent to the hayward fault measured with the global positioning system and interferometric synthetic aperture radar favor creep at 7 millimeters per year to the bottom of the seismogenic zone along a 20 kilometer long northern fault segment microearthquakes with the same waveform repeatedly occur at 4 to 10 kilometer depths and indicate deep creep at 5 to 7 millimeters per year the difference between current creep rates and the long term slip rate of 10 millimeters per year can be reconciled in a mechanical model of a freely slipping northern hayward fault adjacent to the locked 1868 earthquake rupture which broke the southern 40 to 50 kilometers of the fault the potential for a major independent earthquake of the northern hayward fault might be less than previously thought

dynamic behavior of glaciar perito moreno southern patagonia frontal oscillations since the beginning of the 20th century are known at glaciar perito moreno an eastward outlet glacier of hielo patagonico sur southern patagonia ice field in 1900 the calving front was located about 1 km from the opposite bank from 1935 to 1988 ruptures of ice dams occurred at intervals of 1 5 years although this glacier has thus oscillated it can be regarded as having been in a rather stable condition during the last half century ice thickness in the ablation area has also remained unchanged from 1990 to 1996 the near steady behavior of glaciar perito moreno may be attributed to a regulating effect of the calving rate namely a decrease in the ablation amount due to calving with a retreat of the glacier using 12 m long ablation poles ice flow velocities at the ablation area were measured several times in 1993 and 1994 the velocity in the early summer november was found to be slightly larger than the annual mean it is concluded that basal sliding is significant throughout the year at this temperate glacier with large fluctuations within a short period

source analysis of the mw 6 3 2004 al hoceima earthquake morocco using regional apparent source time functions 1 we use small and moderate aftershocks of the 24 february 2004 al hoceima earthquake as empirical greens functions egfs to retrieve the rupture history of the main event the magnitude depth and geometry of faulting were estimated for the main shock and 20 small and moderate aftershocks mw between 3 9 and 5 2 computing moment tensor solutions for the main shock we obtain a moment magnitude of mw 6 3 and a nearly pure double couple source 4 compensated linear vector dipole with predominately strike slip faulting the preferred fault plane has a strike of n11 e a dip of 72 and a rake of 17 fourteen aftershocks having depths 4 km and faulting geometries 11 for the strike of the preferred plane similar to the ones found for the main event were used as egfs apparent source time functions astfs of the al hoceima event were retrieved at twelve regional stations using an iterative time domain deconvolution on the p waveforms at each station time functions are enhanced by stacking of the deconvolved waveforms for different egfs astfs show total durations of 5 to 6 s two consecutive subevents separated by about 3 s and only a weak effect of directivity we further investigate the source history by inverting the set of astfs for the distribution of fault slip and rupture propagation two different source models were selected for presentation one involving one single fault plane and the other involving two parallel fault planes the two fault model fits more accurately the observations and leads to a more plausible slip distribution we estimate rupture dimensions of about 10 10 km2 and 8 8 km2 and moment magnitudes of mw 6 2 and 6 0 for the first and second subevent respectively

inverting for slip on three dimensional fault surfaces using angular dislocations the increasing quality of geodetic data synthetic aperture radar interferometry insar dense global positioning system gps arrays now available to geophysicists and geologists are not fully exploited in slip inversion procedures most common methods of inversion use rectangular dislocation segments to model fault ruptures and therefore oversimplify fault geometries these geometric simplifications can lead to inconsistencies when inverting for slip on earthquake faults and they preclude a more complete understanding of the role of fault geometry in the earthquake process we have developed a new three dimensional slip inversion method based on the analytical solution for an angular dislocation in a linear elastic homogeneous isotropic half space the approach uses the boundary element code poly3d that employs a set of planar triangular elements of constant displacement discontinuity to model fault surfaces the use of triangulated surfaces as discontinuities permits one to construct fault models that better approximate curved three dimensional surfaces bounded by curved tiplines shapes that commonly are imaged by three dimensional reflection seismic data and inferred from relocated aftershock data we demonstrate the method s ability to model three dimensional rupture geometries by inverting for slip associated with the 1999 hector mine earthquake the resulting model avoids displacement anomalies associated with the overlapping rectangular dislocations used in previous models improving the fit to the geodetic data by 32 and honors the observed surface ruptures thereby allowing more direct comparisons between geologic and geodetic data on slip distributions online material hector mine input files and file format description

the role of disseminated calcite in the chemical weathering of granitoid rocks accessory calcite present at concentrations between 300 and 3000 mg kg 1 occurs in fresh granitoid rocks sampled from the merced watershed in yosemite national park ca usa loch vale in rocky mountain national park co usa the panola watershed ga usa and the rio icacos puerto rico calcite occurs as fillings in microfractures as disseminated grains within the silicate matrix and as replacement of calcic cores in plagioclase flow through column experiments using de ionized water saturated with 0 05 atm co2 produced effluents from the fresh granitoid rocks that were dominated by ca and bicarbonate and thermodynamically saturated with calcite during reactions up to 1 7 yr calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates principally biotite mass balance calculations indicate that most calcite had been removed during this time and accounted for 57 98 of the total ca released from these rocks experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution the lack of excess ca and alkalinity indicated that calcite had been previously removed by natural weathering the extent of ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks high ca na ratios relative to plagioclase stoichiometries indicate excess ca in the yosemite loch vale and other alpine watersheds in the sierra nevada and rocky mountains of the western united states this ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains in contrast ca na flux ratios are comparable to or less than the ca na ratios for plagioclase in the subtropical panola and tropical rio icacos watersheds in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport limited weathering these results indicate that the weathering of accessory calcite may strongly influence ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces

oblique plate motion and continental tectonics three dimensional deformation is necessarily associated with oblique plate convergence and commonly results in partitioning of deformation between contractional and transcurrent components along plate margins kinematic models of strike slip partitioning for transpression and transtension allow the exact relation among three critical parameters plate motion instantaneous strain axes and degree of strike slip partitioning to be calculated application to two end member tectonic environments characterized by a low south island new zealand and high central california degree of strike slip partitioning demonstrates a remarkable consistency among the three parameters suggesting that strike slip partitioned transpression is a valid model for deformation in these regions the extreme degree of strike slip partitioning in wrench dominated systems such as central california is tentatively associated with a fundamental misorientation of finite and instantaneous strain axes

chemical weathering in a tropical watershed luquillo mountains puerto rico i long term versus short term weathering fluxes abstract the pristine rio icacos watershed in the luquillo mountains in eastern puerto rico has the fastest documented weathering rate of silicate rocks on the earth s surface a regolith propagation rate of 58 m ma 1 calculated from iso volumetric saprolite formation from quartz diorite is comparable to the estimated denudation rate 25 50 ma 1 but is an order of magnitude faster than the global average weathering rate 6 ma 1 weathering occurs in two distinct environments plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith these environments produce distinctly different water chemistries with k mg and si increasing linearly with depth in saprolite porewaters and with stream waters dominated by ca na and si such differences are atypical of less intense weathering in temperate watersheds porewater chemistry in the shallow regolith is controlled by closed system recycling of inorganic nutrients such as k long term elemental fluxes through the regolith e g si 1 7 10 8 moles m 2 s 1 are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface 200 ma mass losses attributed to solute fluxes are determined using a step wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water pressure heads decrease with depth in the shallow regolith 2 03 m h2o m 1 indicating that both increasing capillary tension and graviometric potential control porewater infiltration interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr 1 at average field moisture saturation which is comparable with libr tracer tests and with base discharge from the watershed short term weathering fluxes calculated from solute chemistries and infiltration rates e g si 1 4 10 8 moles m 2 s 1 are compared to watershed flux rates e g si 2 7 10 8 moles m 2 s 1 consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation temperature and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the luquillo mountains of puerto rico this has important ramifications for tropical environments and global climate change

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

extensional tectonics graben development and fault terminations in the eastern rif bokoya ras afraou area abstract westward motion of the alboran domain between the eurasian and african plate boundaries determined crustal thickening along the southern border of the gibraltar arc forming the rif cordillera this process developed major sinistral ne sw to ene wsw faults such as the nekor fault inactive since the late miocene however the neogene quaternary boudinar and nekor basins underwent very intense recent tectonic and seismic activity related to n s faults kinematics of this fault set changes with depth while at 10 km faults have a sinistral strike slip kinematics they become normal to normal oblique at surface sfeha trougout and boudinar faults their different kinematics could be explained by the existence of a crustal detachment separating two differently pre structured domains shallow transtensive n s faults trend orthogonal to the coastline decreasing their slip southwards until disappearing paleostress analysis shows a progressive change from e w extension near the coastline up to radial extension in southern areas of major fault terminations the behavior of each fault bounded block is conditioned by its inherited rheological features the sequence of horsts bokoya ras tarf ras afraou corresponds mainly to resistant rocks volcanics or limestones whereas the grabens nekor and boudinar basins are generally floored by weak metapelites and flysch the presence of liquefaction structures interpreted as seismites underlines the continued recent seismic activity of the region the recent structures deforming the two alboran sea margins come to support the continuity at present of orogenic processes undergone by the eastern internal regions of the gibraltar arc involving regional e w extension in the framework of nw se to n s eurasian african convergence

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

correlation migration using gaussian beams of scattered teleseismic body waves correlation migration for structural imaging using gaussian beams is described for the inversion of passively recorded teleseismic waves gaussian beam migration is based on an overcomplete frame based representation of the seismic wave field and uses localized slant stack windows of the data paraxial gaussian beams are then utilized for the backpropagation of the seismic waves into the me dium the method can provide stable imaging of seismic data in smoothly varying background media where caustics and triplicated arrivals exist we develop gaussian beam migration for structural imaging which allows for incident teleseismic waves from beneath the structure using directly scattered or surface reflected phases the method is applied to synthetic data computed for a collisional zone model and the inversions show that the gaussian beam migration can image structure using passive teleseismic data the method is next applied to synthetic data that have been con volved with an observed pulse from the 1993 cascadia experiment the autocorre lation is computed and the autocorrelated data are migrated by using gausian beams for direct p to s scattered waves and surface reflected waves although the migra tions of the autocorrelation data with the source pulse included have more noise than the migrations of the impulsive source data the subduction zone structure can still be clearly identified in the migrated results without removal of the source pulses

high resolution imagery of active faulting offshore al hoceima northern morocco abstract two recent destructive earthquakes in 1994 and 2004 near al hoceima highlight that the northern moroccan margin is one of the most seismically active regions of the western mediterranean area despite onshore geodetic seismological and tectonic field studies the onshore offshore location and extent of the main active faults remain poorly constrained offshore al hoceima high resolution seismic reflection and swath bathymetry have been recently acquired during the marlboro 2 cruise these data at shallow water depth close to the coast allow us to describe the location continuity and geometry of three active faults bounding the offshore nekor basin the well expressed normal left lateral onshore trougout fault can be followed offshore during several kilometers with a n171 e 3 trend westward the bousekkour aghbal normal left lateral onshore fault is expressed offshore with a n020 e 4 trending fault the n030 e 2 bokkoya fault corresponds to the western boundary of the plio quaternary offshore nekor basin in the al hoceima bay and seems to define an en echelon tectonic pattern with the bousekkour aghbal fault we propose that these three faults are part of the complex transtensional system between the nekor fault and the al idrissi fault zone our characterization of the offshore expression of active faulting in the al hoceima region is consistent with the geometry and nature of the active fault planes deduced from onshore geomorphological and morphotectonic analyses as well as seismological geodetic and geodynamic data

temperature dependence of silicate weathering in nature how strong a negative feedback on long term accumulation of atmospheric co2 and global greenhouse warming estimation of the temperature dependence of natural feldspar weathering in two catchments at different elevations yields an apparent arrhenius activation energy of 18 4 kcal mol 77 0 kj mol much higher than most laboratory values this finding supports recent suggestions that hydrolytic weathering of silicate minerals may consume carbonic acid and thereby remove atmospheric carbon dioxide more rapidly with increasing temperature than previously thought this result provides a stronger negative feedback on long term greenhouse warming than has been assumed in most models of global carbon cycling the present estimate was determined from the ratio of feldspar weathering rates determined by geochemical mass balance in the southern blue ridge mountains of north carolina united states temperature a function of elevation is the only factor that differs between the two catchments parent rock type aspect hillslope hydrology and vegetation type and successional stage are the same in both

present day state of stress in northern morocco from focal mechanism analysis abstract the use of focal mechanisms of micro earthquakes and moderate teleseisms in the al hoceima area northern morocco enables the determination of the state of stress in the southern part of the gibraltar arc two different states of stress were determined 1 a ene wsw extension in the imzouren area probably with similar magnitudes of 2 and 1 which may be controlled by pre existing structures and 2 a strike slip regime in beni boucetta tamassint and beni abdallah areas 1 nnw sse 3 ene wsw in the two first areas and 1 ne sw 3 nw se in the latter contrary to recently proposed ideas the mean state of stress determined with the help of moderate teleseisms corresponds to a strike slip regime with a nnw sse oriented main compressional axis and a ene wsw horizontal extension similar to the stress field determined from neotectonic studies and somewhat different from that determined from the el asnam aftershock sequence of 1980

source parameters of the 1992 melilla spain mw 4 8 1994 alhoceima morocco mw 5 8 and 1994 mascara algeria mw 5 7 earthquakes and seismotectonic implications source mechanisms of the melilla alhoceima and mascara earthquakes including fault plane solutions waveform modeling and spectral analysis are presented strike slip solutions have been obtained for the melilla and alhoceima earthquakes and reverse faulting for mascara teleseismic p wave inversion using broadband data show a complex mechanism for the alhoceima earthquake formed by two subevents at very shallow depth 7 and 8 km and scalar seismic moments of 1 1 10e 17 n m and 4 8 10e 17 n m the mascara earthquake was a single event with a shallow depth 4 5 km and a scalar seismic moment of 3 3 10e 17 n m results of the alhoceima melilla and mascara earthquakes together with 53 focal mechanisms in the region show a regional stress regime that corresponds to horizontal compression in a nw se direction associated with the convergence between eurasia and africa a change of the stress regime in the plate boundary of the ibero maghrebian region has been found

retreat of glaciar tyndall patagonia over the last half century we report measurements of ice surface elevation ice thickness and surface area for glaciar tyndall patagonia made in 1999 2002 the measurements together with previously published observations show acceleration over the last few decades of the rates of thinning and retreat of the main calving front the acceleration of shrinkage appears to be driven by a combination of climate and feedback processes the dominant feedback being increased melting associated with lowering of the glacier surface elevation feedback the melting capacity in the main terminus lake is now too small to be a major factor accelerating the retreat the glacier bed has low slope and remains below the elevation of the lake spillway for 14 km upstream from the 2000 calving front indicating the potential for extensive retreat under the influence of strong elevation feedback and increasing interaction with the lake as it enlarges

an integrated geophysical investigation of recent seismicity in the al hoceima region of north morocco abstract data produced by the moroccan national seismological network and marine seismic reflection profiles are used to investigate the most seismically active region in morocco located on the mediterranean coast at the intersection of the rif mountain belt and the submarine alboran ridge this region in the vicinity of the city of al hoceima marks an east west transition in the marine and land deformation styles of the distributed plate boundary between africa and iberia and was the site of an m w 6 0 earthquake on 26 may 1994 the epicenter of the al hoceima earthquake is relocated onshore refining the initial submarine location close to the alboran ridge the spatial distribution of foreshocks and aftershocks shows a ne sw trend that continues partly offshore and is subparallel to the earlier yet still prominent miocene geologic structural trend the predominantly strike slip focal mechanism for the al hoceima event is characteristic of earthquakes in the region marine seismic reflection profiles that intersect the offshore region of seismicity image active high angle faults with possible strike slip components the seismicity trend is not directly related to the submarine alboran ridge or the geomorphologically prominent nekor fault deformation appears to be occurring on a number of subsidiary strike slip faults that together compose a ne sw zone of distributed shear the distributed strike slip and documented normal faulting taking place in the eastern rif mountains although characteristic of the rif region are in contrast to the thrusting style of deformation that occurs farther to the east in the algerian tell atlas this may be related to the reported lateral variations and evolution of the convergent plate boundary in these regions during the neogene and quaternary times

calving rates in fresh water new data from southern patagonia data relating to calving dynamics in fresh water are scarce especially for deep water sites a linear dependence of calving velocity vc onwater depth hw is commonly accepted for both tidewater and fresh water calving glaciers herewe use recent data from temperate patagonian glaciers to propose a revised relationship for calving in fresh water the new ratio is derived from glaciers calving rapidly into deep water documented using sequential satellite images and depth soundings the main data source is a detailed remotely sensed dataset of the rapidly retreating glaciarupsala complementedwith global positioning system field surveys and precise ice proximal bathymetric surveys the areaintegrated mean water depth between glacier positions in 1996 and 2000 is 490m with a maximum recorded depth of4700m in the same period image analysis reveals surface area loss of 1 37 km a 4 8 km and an average calving rate of 1880ma the resulting vc hw ratio is of a similar order of magnitude to that recently derived for nearby glaciar moreno but is well above the range of values commonly reported for lacustrine calving

onset of neoglaciation in the southern hemisphere a review of evidence documenting an early neoglacial mid holocene advance of mountain glaciers in south america and new zealand reveals that of 16 glaciers for which radiocarbon age control exists only two have associated dates that may approximate the culmination of an advance advances of the remaining glaciers are controlled only by minimum or maximum limiting ages additional dates for several new zealand glaciers are based on weathering rind measurements having large potential errors twelve of the glaciers now terminate or have terminated in lakes or in tidewater and are subject to instabilities associated with calving termini an extensive debris cover in the ablation zone of nearly half of the glaciers makes their moraine succession potentially suspect as a record of detailed climatic variation the two glaciers with seemingly reliable age control are located in valleys where large rock avalanches could affect glacier mass balance and lead to random advances or where rock avalanche deposits might easily be mistaken for moraines and tills the early neoglacial interval has been defined primarily based on this set of data the ages taken at face value suggest that the early neoglacial advance culminated between ca 5400 and 4900 cal yr ago ca 4600 4400 14c yr bp this chronology however should remain provisional until improved age control is obtained for a large population of glaciers based on closely bracketing radiocarbon dates and or an adequate number of cosmogenic isotope ages data from calving glaciers and those subject to rock avalanche activity should be avoided or assessed critically copyright 2000 john wiley sons ltd

mass fluxes and dynamics of moreno glacier southern patagonia icefield accumulation ablation calving and flow dynamics of moreno glacier one of the main outlet glaciers of the southern patagonia icefield were studied based on field campaigns and on spaceborne radar imagery acquired by sir c x sar ice velocities and ablation were measured through two summers and one winter the ice depth was sounded seismically at a transect 8 km above the calving front showing a maximum depth of 720 m the velocity field of the terminus was derived from sir c x sar data by means of interferometry and amplitude correlation the average specific annual net accumulation is 5540 500 mm water equivalent the bottom topography of the lake and the high ratio of calving flux to net accumulation explain the remarkable stability of moreno glacier throughout this century which is in contrast to the retreat of other glaciers in this region

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

global compilation of interferometric synthetic aperture radar earthquake source models 1 comparisons with seismic catalogs 1 while many earthquakes have now been studied using interferometric synthetic aperture radar insar data a full assessment of the quality and additional value of insar source parameters compared to seismological techniques is still lacking we compile a catalog of source models obtained using insar and estimate the corresponding centroid moment tensor cmt parameters we refer to this compilation as the icmt archive we compare source parameters from over 70 insar studies of 57 global earthquakes with those in the global cmt gcmt international seismological centre isc and engdahl hilst buland ehb seismic catalogs we find an overall good agreement between fault strike dip and rake values in the gcmt and icmt archives likewise the differences in seismic moment between these two archives are relatively small and we do not find support for previously suggested trends of insar leading to larger moments than seismic data however epicentral locations show substantial discrepancies which are larger for the gcmt median differences of 21 km than for the ehb and isc catalogs median differences of 10 km since insar data have a high spatial resolution and thus should map epicentral locations accurately this allows us to obtain a first independent estimate of epicentral location errors in the seismic catalogs earthquake depths from insar are systematically shallower than those in the ehb catalog with a median of differences of 5 km while this trend may be partly due to unmodeled crustal complexity it is also compatible with the observation that the rupture of crustal earthquakes tends to propagate upward in the seismogenic layer

the al hoceima morocco earthquake of 24 february 2004 analysis and interpretation of data from envisat asar and spot5 validated by ground based observations abstract the magnitude mw 6 3 earthquake in al hoceima morocco of 24 february 2004 occurred in the active plate boundary accommodating the oblique convergence between africa and eurasia three different sets of estimates of its source parameters have already been published we try to resolve the discrepancies between them by using additional data including two remote sensing satellite systems envisat and spot5 using a model with a dislocation in an elastic half space we constrain the source parameters the hypothesis of two subevents on distinct faults as inferred from seismological inversions is confirmed here by adopting a cross fault mechanism the rupture began on a left lateral strike slip fault striking at n10 azimuth with 90 cm of horizontal slip and then transferred to a right lateral strike slip fault striking at n312 azimuth with 85 cm of horizontal slip the first fault is at 500 m depth from the free surface and the second fault is at 3 km depth this model is consistent with ground based observations including gps seismology and mapped surface fissures the pair of faults activated in 2004 appears to constitute part of a complex seismogenic structure striking nne ssw that separates the rif tectonic blocks

the 1994 2004 al hoceima morocco earthquake sequence conjugate fault ruptures deduced from insar abstract we study the may 26 1994 mw 6 0 and february 24 2004 mw 6 4 earthquakes that affected the al hoceima region of northern morocco these events are the two strongest earthquakes recorded in this region yet the exact location kinematics and relationships between these earthquakes are poorly known since neither of them produced surface ruptures using synthetic aperture radar interferometry insar we mapped the surface displacement field of the two earthquakes to characterize their seismic source parameters analysis of the interferograms constructed from ascending and descending orbits for both earthquakes and subsequent elastic modeling using slip inversions on triangular fault patches suggest that the two mainshocks occurred on blind conjugate strike slip faults the 1994 earthquake being associated with n23 e trending left lateral fault and the 2004 earthquake with n45 w trending right lateral fault this result contradicts previous inferences on the kinematics location and rupture geometry of the earthquakes deduced from conventional analyses of seismic waveforms and aftershocks distribution the insar analysis reveals the fragmentation of the rif mountain throughout a complex network of conjugate blind faults consistent with the transpression tectonics along the plate boundary in north africa although the two earthquakes took place in the rif thrust and fold belt the late quaternary deformation indicates e w extension in agreement with the nw se and ne sw trending conjugate strike slip faulting

postseismic rebound in fault step overs caused by pore fluid flow near field strain induced by large crustal earthquakes results in changes in pore fluid pressure that dissipate with time and produce surface deformation synthetic aperture radar sar interferometry revealed several centimeters of postseismic uplift in pull apart structures and subsidence in a compressive jog along the landers california 1992 earthquake surface rupture with a relaxation time of 270 45 days such a postseismic rebound may be explained by the transition of the poisson s ratio of the deformed volumes of rock from undrained to drained conditions as pore fluid flow allows pore pressure to return to hydrostatic equilibrium

simple models for late holocene and present day patagonian glacier fluctuations and predictions of a geodetically detectable isostatic response summary the late holocene glacial moraine chronology in the southernmost south american andes includes four 14c dated neoglacial advances and retreats these are used as proxy information to characterize mass fluctuation of the patagonian icefields during the last 5000 years modelled ice loads force a phase lagged viscoelastic gravitational deformation of the solid earth the ancient glacier fluctuations may therefore drive present day crustal motion even in the absence of present day ice mass imbalance numerical models show that such rates of present day uplift and subsidence are larger than those driven by the viscous memory of late pleistocene deglaciation both spherical and flat earth models are employed the latter being used to study exhaustively the evects of glacial load history on the predicted vertical crustal velocity recent assessment of net mass balance from 1944 to 1985 indicates that the southern patagonian icefield has significantly deteriorated due to snout retreat and thinning volume loss rates are estimated at about 3 4 9 3 km3 yr 1 the predicted vertical isostatic response to this recession and to the modelled holocene neoglaciations is at a marginally detectable level 1m m yr 1 if the mantle asthenosphere beneath patagonia has a viscosity of about 1021 pa s however for reduced mantle viscosities the younger holocene glacial load histories predict larger signatures in fact if the viscosity is about 2 1020 pa s or lower then geodetically detectable vertical motion may be driven by a regional little ice age lia 1400 1750 ad glacier advance and subsequent 20th century retreat although this value for mantle viscosity is lower than thought typical of continental shield mantle 1021 pa s it is consistent with inversions for post seismic relaxation time constants in island arc environments and in regions with significant neogene continental tectonism in the viscosity regime of 5 1018 2 1019 pa s the predicted rates of vertical crustal motion are similar to those presently occurring in fennoscandia and hudson bay 5 10 mm yr 1 geodetic data may be sensitive to the time integrated growth and subsequent retreat of patagonian glacier ice mass over the last 600 years

the ubiquitous nature of accessory calcite in granitoid rocks implications for weathering solute evolution and petrogenesis calcite is frequently cited as a source of excess ca sr and alkalinity in solutes discharging from silicate terrains yet no previous effort has been made to assess systematically the overall abundance composition and petrogenesis of accessory calcite in granitoid rocks this study addresses this issue by analyzing a worldwide distribution of more than 100 granitoid rocks calcite is found to be universally present in a concentration range between 0 028 to 18 8 g kg 1 mean 2 52 g kg 1 calcite occurrences include small to large isolated anhedral grains fracture and cavity infillings and sericitized cores of plagioclase no correlation exists between the amount of calcite present and major rock oxide compositions including cao ion microprobe analyses of in situ calcite grains indicate relatively low sr 120 to 660 ppm negligible rb and 87sr 86sr ratios equal to or higher than those of coexisting plagioclase solutes including ca and alkalinity produced by batch leaching of the granitoid rocks 5 co2 in di water for 75 d at 25 c are dominated by the dissolution of calcite relative to silicate minerals the correlation of these parameters with higher calcite concentrations decreases as leachates approach thermodynamic saturation in longer term column experiments 1 5 yr reactive calcite becomes exhausted solute ca and sr become controlled by feldspar dissolution and 87sr 86sr by biotite oxidation some accessory calcite in granitoid rocks is related to intrusion into carbonate wall rock or produced by later hydrothermal alteration however the ubiquitous occurrence of calcite also suggests formation during late stage subsolidus magmatic processes this conclusion is supported by petrographic observations and 87sr 86sr analyses a review of thermodynamic data indicates that at moderate pressures and reasonable co2 fugacities calcite is a stable phase at temperatures of 400 to 700 c

surface deformation associated with the mw 6 4 24 february 2004 al hoceima morocco earthquake deduced from insar implications for the active tectonics along north africa we study the surface deformation associated with the 24 february 2004 al hoceima earthquake mw 6 4 that recently affected the rif mountains of mo rocco the coseismic displacement field is mapped using synthetic aperture radar interferometry insar with the envisat esa satellite data acquired in the ascend ing and descending modes our analysis and modeling of insar data suggest that the earthquake is associated with a northwest southeast trending right lateral ap parently blind strike slip fault with a seismic moment reaching 6 8 10 18 n m this result is in contrast with the north northeast south southwest left lateral fault mech anism inferred from the modeling of seismic waves thrust and fold structures of the rif mountains developed during the tertiary period but the recent significant seismic events and late quaternary deformation indicate east west extension accom modated by north south trending normal and northwest southeast and northeast southwest trending conjugate strike slip faults the active deformation illustrates the fragmentation of the rif mountain range due to the africa iberia collision and west southwestward escape tectonics

direct effects of co2 and temperature on silicate weathering possible implications for climate control a critical uncertainty in models of the global carbon cycle and climate is the combined effect of organic activity temperature and atmospheric co2 on silicate weathering here we present new dissolution rates of anorthite and augite which indicate that silicate weathering in organic rich solutions is not directly affected by soil co2 but is very sensitive to temperature apparently co2 accelerates silicate weathering indirectly by fertilizing organic activity and the production of corrosive organic acids the weathering dependencies highlight the ability of silicate weathering to act as a global thermostat and damp out climate change when used as input in steady state carbon cycle and climate models

the dahuiyeh zarand earthquake of 2005 february 22 in central iran reactivation of an intramountain reverse fault we used seismic body waves radar interferometry and field investigation to examine the source processes of the destructive earthquake of 2005 february 22 near zarand in south central iran the earthquake ruptured an intramountain reverse fault striking e w and dipping north at 60 to a depth of about 10 km it produced a series of coseismic scarps with up to 1 m vertical displacement over a total distance of 13 km continuous for 7 km the line of the coseismic ruptures followed a known geological fault of unknown but probably pre late cenozoic age and involved bedding plane slip where the scarps were continuous at the surface however any signs of earlier coseismic ruptures along this fault had been obliterated by the time of the 2005 earthquake probably by land sliding and weathering so that the fault could not reasonably have been identified as active beforehand the 2005 fault is at an oblique angle to the range bounding kuh banan strike slip fault and may represent a splay from that fault related to its southern termination other intramountain reverse faulting earthquakes have occurred in iran but this is the first to have produced a clear mapped surface rupture and to have been studied with insar faults of this type represent a serious seismic hazard in iran and are difficult to assess because their geomorphological expression is much less clear than the range bounding reverse faults which are more common and have been better studied

creeping along the ismetpasa section of the north anatolian fault western turkey rate and extent from insar creeping along the north anatolian fault naf at ismetpasa turkey was discovered some thirty years ago about a decade after the first observations of the phenomenon along the san andreas fault in california however little is known about its lateral extent and rate in order to study its three dimensional nature and rupture characteristics we use synthetic aperture radar interferometry insar and elastic dislocation models compared also with field observations interferograms with temporal baselines ranging between 1 25 and 5 years show that the creeping section starts at the western termination of the 1943 m 7 6 earthquake rupture it continues about 70 km to the west overlapping with the eastern part of the 1944 m 7 3 earthquake rupture offsets along strike indicate a maximum creep rate of 11f3 mm year near the mid point of the creeping section decreasing gradually towards the edges near ismetpasa insar data yield 8f3 mm year of creep rate consistent with recent instrumental triangulation and creepmeter measurements modeling of the insar and gps data suggests that the faultcreep occurs most probably at a shallow depth 0 7 km our analysis combined with previous studies suggests that creeping might have commenced following the 1944 earthquake and thus may be a long lasting but transient slip episode d 2005 elsevier b v all rights reserved

geochemical evidence supporting t c chamberlin s theory of glaciation in 1899 t c chamberlin proposed that the co sub 2 content of the atomsphere decreased during times of enhanced continental erosion ultimately resulting in glacial epochs he ascribed the increase in the rate of chemical weathering relative to the rate of supply of co sub 2 from earth s interior to increased orogenic activity and globally higher average elevations which promoted rapid chemical erosion of silicates the oceanic record of strontium isotopes preserved in marine sediment supports his suggestion that glacial climates during the phanerozoic are in part linked to increases in the rate of global chemical erosion relative to outgassing from earth s interior further the close correspondence of the major tectonic episodes of the late cenozoic to times of increased continental erosion and glaciation suggests that chamberlin s hypothesis of the cause of glacial periods should be revived

strong tectonic and weak climatic control of long term chemical weathering rates the relationships among climate physical erosion and chemical weathering have remained uncertain because long term chemical weathering rates have been difficult to measure here we show that long term chemical weathering rates can be measured by combining physical erosion rates inferred from cosmogenic nuclides with dissolution losses inferred from the rock to soil enrichment of insoluble elements we used this method to measure chemical weathering rates across 22 mountainous granitic catchments that span a wide range of erosion rates and climates chemical weathering rates correlate strongly with physical erosion rates but only weakly with climate implying that by regulating erosion rates tectonic uplift may significantly accelerate chemical weathering rates in granitic landscapes

geochemical and palaeohydrological controls on the composition of shallow groundwater in the netherlands with the exception of the south of the country the netherlands has a strong bipartite hydrogeology the holocene part with a coastal dune belt and confining top layer of clay and peat further inland and the pleistocene where thick phreatic aquifers dominate this research aimed to ascertain the geochemical and palaeohydrological controls on the composition of shallow groundwater in 27 regions close to 6000 groundwater analyses were grouped and interpreted in terms of 1 salinity 2 redox status 3 acid base and carbonate status and 4 natural nutrients nh4 and po4 the a priori classification into geographical regions and geological formations revealed many statistically significant differences in medians even for geologically or geographically related data groups the compound specific interpretation indicates that there are geogenically controlled systematic differences in groundwater composition at the regional scale the imprint of the geological sediments on the groundwater composition decreases in the order marine estuarine via limnological fluvial to aeolian the imprints with respect to ph and carbonate status natural nutrients and redox status are not necessarily interrelated the vertical stratification in groundwater composition turns out to be often limited at the regional scale due to mutual occurrence of infiltrating and exfiltrating groundwater in regions and either the presence of a highly reactive holocene confining top layer or temporal changes in contamination in the holocene part the salinity is controlled by the palaeoenvironmental conditions during the holocene and by the recharge origin the average cl concentration decreases from estuarine via lagoonal to the former zuider sea which was a bay the most reduced states and also the highest nutrient concentrations and highest co2 pressure are related to the presence of holocene marine sediments in the confining top layer degradation of marine derived organic matter as a nutrient source is likely more intense in the holocene deposits than that of peat and sedimentary remnants of terrestrial plants a broad range in ph carbonate status and redox status is encountered in the pleistocene part here the palaeohydrological evolution in terms of carbonate leaching together with the geological controls on the calcareous nature of the shallow sedimentary deposits cause regional differences in ph calcite saturation and silicate weathering one region with late pleistocene limnological deposits has deviating groundwater characteristics and appears more similar to the holocene part of the netherlands furthermore reactive fe is not abundant in all pleistocene fluvial sediments nor is it maximally mobilised as not all anoxic groundwater in these sediments is siderite saturated this leads to considerable intra and inter region variability 2013 elsevier ltd

a potential high elevation ice core site at hielo patagonico sur the patagonia icefields constitute a unique location in the southern hemisphere for obtaining non polar paleo records from ice cores south of 458 s nevertheless no ice core record with meaningful paleoclimate information has yet been obtained from patagonia this deficiency is due to extremely harsh field conditions and to the fact that the main plateaus of both hielo patagonico norte hpn northern patagonia icefield and hielo patagonico sur hps southern patagonia icefield are strongly affected by meltwater percolation in order to explore the suitability of high elevation glacier sites at hps as paleoclimate archives three shallow firn cores were retrieved covering the altitude range 1543 2300 m a s l the glaciochemical records from the two lower sites confirm the presence of superimposed ice a clear sign of meltwater formation and percolation in the core from 2300 m the glaciochemical signature appears to be preserved indicating that no significant melting occurred although there might be problems associated with wind erosion and extreme melt events there is good potential for well preserved paleo records within glaciers in the patagonia icefields located higher than 2300 m

interferometric synthetic aperture radar observations of the 1994 double spring flat nevada earthquake m5 9 main shock accompanied by triggered slip on a conjugate fault 1 the 1994 double spring flat dsf earthquake m5 9 was the largest earthquake to strike nevada in more than 30 years it occurred in the sierra nevada basin and range transition zone within a step over region between two major normal faults descending and ascending ers interferograms show a maximum range change of 8 5 cm which is the coseismic ground displacement associated with this normal oblique slip moderatesized earthquake elastic inverse modeling and surface displacements across coseismic ground cracks suggest that two different event sources could account for the observed deformation the first source was the main shock with right oblique slip on the northnorthwest striking dsf fault the second source was normal faulting on a shallow northnortheast striking elongated plane conjugate to the dsf fault these two sources are consistent with the pattern of postevent seismicity and we suggest that the second source represents seismic and aseismic slip triggered by the main shock calculations of changes in coulomb failure stress show that the main shock encouraged normal slip on this plane index terms 1206 geodesy and gravity crustal movements interplate 8155 1241 geodesy and gravity satellite orbits 1242 geodesy and gravity seismic deformations 7205 1299 geodesy and gravity general or miscellaneous 7212 seismology earthquake ground motions and engineering

investigation of in situ weathering of quartz diorite bedrock in the rio icacos basin luquillo experimental forest puerto rico abstract the rio icacos basin in puerto rico is the site of the highest measured chemical solute fluxes for a catchment on granodiorite this is partly attributable to high annual rainfall 4300 mm high average temperature 23 c and moderate relief the bulk of these fluxes is contributed by dissolution of plagioclase and amphiboles in zones of partially weathered rock 0 5 1 5 m thick underlying saprolite these zones are characterized by systems of onion skin rindlets each 3 10 cm thick in which porosity development is dominated by weathering of plagioclase to kaolinite fe bearing aluminosilicate minerals hornblende augite and biotite persist in the weathered rock after plagioclase has weathered to completion but hornblende and augite disappear between the porous rindlet systems and saprolite a new watershed scale solute mass balance corroborates earlier studies and yields an overall reaction stoichiometry that closely resembles complete weathering of the rock except quartz and biotite to kaolinite and fe3 oxides our findings indicate that steady state assumptions are reasonable and useful in studying weathering at this site estimated steady state sediment yields based on net solute fluxes and average bedrock composition of 3 24 10 9 to 3 60 10 9 kg m 2 s 1 are smaller than measured values indicating that sediment generation is currently accelerated with respect to steady state however sediment generation has recently been closer to steady state since weathering within the rindlet systems occurs on multiple fronts moving upward and downward two new steady state conceptual models are developed to account for 1 multiple parallel weathering fronts and 2 differential rates of advance of weathering fronts due to porosity development based on these models in situ weathering rates for plagioclase at two sample locations of 2 7 10 15 and 5 0 10 15 mol na g 1 s 1 are calculated values comparable to bet surface area normalized rates of 2 7 10 16 to 5 0 10 15 mol na m 2 s 1

the 2016 south alboran earthquake m w 6 4 a reactivation of the ibero maghrebian region abstract on 25 january 2016 an earthquake of magnitude m w 6 4 occurred at the southern part of the alboran sea between southern spain and northern morocco this shock was preceded by a foreshock m w 5 1 and followed by a long aftershock sequence focal mechanism of main shock has been estimated from slip inversion of body waves at teleseismic distances solution corresponds to left lateral strike slip motion showing a complex bilateral rupture formed by two sub events with most energy propagating along a plane oriented n30 e plane dipping to the nw relocation of larger events of the aftershock series show two alignments of epicentres in ne sw and nne ssw direction that intersect at the epicentre of the main shock we have estimated the focal mechanisms of the largest aftershocks from moment tensor inversion at regional distances we have obtained two families of focal mechanisms corresponding to strike slip for the nne ssw alignment and thrusting motion for the ne sw alignment among the faults present in the area the al idrisi fault or fault zone may be a good candidate for the source of this earthquake the study of coulomb failure stress shows that it is possible that the 2016 earthquake was triggered by the previous nearby earthquakes of 1994 m w 5 8 and 2004 m w 6 3 the possible seismic reactivation of the central part of the ibero maghrebian region is an open question but it is clear that the occurrence of the 2016 earthquake confirms that from 1994 the seismicity of central part of imr is increasing and that focal mechanism of largest earthquakes in this central part correspond to complex ruptures or zone of fault