surface wave mapping of the crust and upper mantle in the arctic region pure path rayleigh wave group velocities for 24 regional grids inside the arctic have been obtained from 74 mixed path measurements the vertical shear wave velocity structures under these 24 grids were then determined according to their pure path group velocity dispersion data this result indicates that the crustal shear wave velocity in the arctic region is generally lower than the worldwide average in addition a typical mid ocean ridge structure was clearly shown under the nansen ridge we also found an abnormally high upper mantle shear wave velocity under the alpha ridge and makarov basin and low velocity beneath the canadian arctic islands in general our inversion result agrees with the known tectonics in the arctic region to further check the validity of our result we have computed synthetic rayleigh waves and a comparison with our observations shows very good agreement

a field based model of permafrost controlled rockslide deformation in northern norway abstract knowledge about the detailed processes linked to the existence of permafrost in rockslide fractures is sparse large parts of the jettan rockslide are located right below the discontinuous permafrost limit in the arctic part of the alpine landscape of northern norway combining four years of meteorological and rockslide deformation data with temperature measurements from different parts of open fractures shallow bedrock boreholes and air as well as daily snow cover observations allows a detailed identification of the key processes involved these field data are the basis for the development of a permafrost controlled rockslide model seasonally the deformation has a very distinctive pattern with high deformation starting abruptly right after snowmelt in may and lasting until snow isolation in winter then there is a gradual transition to medium deformation as the ground is cooled further for another 1 2 months finally the winter period when maximum snow occurs in the fractures is characterized by limited or almost no deformation the primary controlling deformation process is meltwater percolation into fractures in summer with significant refreezing ice formation and temperature increase in the lower part of the fractures from 1 c to 0 c sporadic permafrost exists below the discontinuous permafrost limit and may extend into open fractures and sliding planes another primary process is the significant cold air accumulation in fractures in early winter due to the balch effect which significantly cools the fracture and surrounding rock promoting permafrost development finally the cold air effect is stopped by snow isolation once enough snow has accumulated in the fracture by late winter the deformation itself is thought to be controlled by changing shear strength of the brecciated sliding planes due to either changing ice temperatures and or variations in water infiltration to the unsaturated sliding zones the overall system is very locally controlled driving itself and the effect of a future climate change can thus be of minor importance

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

surface wave profiling of the lithosphere beneath the mojave desert using terrascope data we have applied surface wave analysis to the mojave desert in southern california to extract the regional lithosphere velocity structure seismograms from teleseismic sources recorded by the terrascope stations a recently established network of broadband instruments were used to determine the phase velocity dispersion data of rayleigh waves for wave paths crossing the mojave desert an inversion analysis on the dispersion data for each path gave the shear wave velocity structure beneath the path inversion results show that there is a low velocity layer at the middle and lower crust which is particularly pronounced for paths traversing the western part of the mojave desert this low velocity layer at the midcrust may reflect the existence of a transition zone from the brittle to the ductile regimes where there is an absence of earthquake occurrence

lateral velocity variations in southern california i results for the upper crust from pg waves the plate boundary and major crustal blocks in southern california are imaged by a tomographic backprojection of the pg first arrivals recorded by the southern california array the method formulated specifically for local earthquake arrival times is a fast iterative alternative to direct least squares techniques with it we solve the combined problem of determining refractor velocity perturbations and source and station delays resolution and variance are found empirically by using synthetic examples a map showing lateral velocity variations at a depth of approximately 10 km is presented the results show a strong correlation with surface tectonic features clear velocity contrasts exist across the san andreas the san jacinto and the garlock faults the mojave region has the slowest velocities while the peninsula ranges have the highest the san jacinto block has velocities intermediate between mojave and peninsula range velocities and also has early station delays this may indicate that the san jacinto block has overridden mojave material on a shallow detachment surface no velocity variations are found associated with the transverse ranges which we interpret to mean that the surface batholithic rocks in this area do not extend to pg depths

the deep crustal structure of the mojave desert california from cocorp seismic reflection data cocorp seismic reflection profiling in the western and northern mojave desert of southern california has revealed the presence of numerous major low angle reflecting horizons within the crust these complex though laterally continuous horizons are interpreted to represent major southwesterly dipping crustal fault zones and as such they place important constraints on the tectonic evolution of the region the upper most horizon is interpreted to be the rand thrust which where exposed places precambrian and late cretaceous crystalline rocks over possibly younger pelona rand orocopia schist this reflecting horizon extends for 25 km southwest of the rand mountains where it appears to be truncated at a depth of about 7 4 km by another horizon which may be a later low angle normal fault the other reflecting horizons are not traceable to the surface and so greater ambiguity remains in their interpretation the most prominent of these horizons occurs at midcrustal depths 15 6 km exhibits a ramp and flat geometry and extends over the northern area of the mojave survey into the basin and range province a lower horizon at depths of 20 30 km in the northern part of the survey area is antiformal and appears to terminate above a flat and relatively continuous moho depth horizon the crustmantle transition appears to be represented by a continuous series of reflections which occur at about 10 s 33 km in the north of the survey and at about 8 9 s 26 29 km in the south these reflections are offset in the vicinity of the town of mojave the deep intracrustal fault zones inferred from the cocorp survey may represent 1 the deep crustal continuation of the system of mesozoic thrusts which crops out in southern nevada and southeastern california 2 late cretaceous to early cenozoic northeast vergent thrusts related to the uplift of the pelona orocopia rand schist or 3 low angle normal faults related to early miocene northeast southwest directed crustal extension the cocorp survey also traversed the major strike slip faults that bound the mojave block the san andreas fault zone appears to truncate reflectors at depths of 6 8 and 20 km within the mojave basement suggesting that it is a major vertical feature which extends to at least 20 km depth conversely the garlock fault does not offset an underlying reflecting horizon which occurs at 9 km depth and therefore appears to be a relatively shallow crustal feature

seismic reflection constraints on the structure of the crust beneath the san bernardino mountains transverse ranges southern california a 30 km long n s seismic reflection line was shot by california consortium for crust studies calcrust across the southern mojave desert and onto the northern flank of the san bernardino mountains in southern california on the northern end of the seismic section the reflectivity increases markedly in the midcrust at a depth corresponding to a two way travel time of 4 to 5 s 12 15 km suggesting a transition between nonreflecting brittle upper crust and reflecting ductile lower crust the high reflectivity disappears at about 8 s 24 km and may be correlated with a change in seismic velocity in the lower crust from 6 3 km s to 6 8 km s a band of reflectivity between 9 5 and 10 s 27 30 km is believed to represent the moho the midcrustal relectivity transition and moho both deflect downward toward the san bernardino mountains uplift over the entire length of the profile the deflection of the midcrustal transition 12 appears greater than that of the moho 6 resulting in a thinning of the lower crust to the south beneath the uplift in addition the midcrustal transition coincides with the base of the seismogenic zone brittle ductile transition which is also dipping southward beneath the san bernardino mountains while the moho deflection is consistent with elastic flexure resulting from edge loading by the san bernardino mountains which have been thrust over the mojave block it is suggested that the thinning of the lower crust beneath the san bernardino mountains is a result of north directed ductile flow in response to loading by the over thickened upper crust since a portion of the load is transmitted through the lower crust to the moho the time constant for flow equilibrium must be of the order of or greater than that for the time of uplift 2 m y

three dimensional crust and upper mantle structure of the eurasian continent group velocities of fundamental mode rayleigh waves of 109 wave paths within eurasia have been measured by an improved frequency time analysis technique stochastic inversion theory is applied to the mixed path measurements to extract pure path group velocities of 10 10 grid elements that form the subdivisions of eurasia then a three dimensional crust and upper mantle structure of the eurasian continent to a depth of 300 km is constructed the average crustal thickness of eurasia is found to be about 40 km abnormally thick crust from 50 to 65 km is obtained in areas of tien shan the altai mountains afghanistan pamir tibet and burma among them tibet has the least dense crust and highest elevation this implies that at least part of the elevation of tibet is due to isostatic compensation the upper mantle seismic velocity of the tectonically active regions of asia is considerably lower than that of the european and siberian cratons if high velocity implies high rigidity this explains that large scale tectonic deformations of eurasia occur in regions with weak upper mantle that deforms more plastically regions with stronger upper mantle remain relatively undeformed this is especially evident for the tertiary tectonic deformation as a consequence of the collision of india with eurasia

rock glacier surface motion in beacon valley antarctica from synthetic aperture radar interferometry 1 we present radar interferograms of rock glaciers in the beacon valley sector of the mcmurdo dry valleys in east antarctica as part of a comprehensive study of surface processes in the area due to the relative absence of net precipitation snow in this region and the stability of the surface the rock glaciers maintain excellent coherence of the radar returns over several years as a result we obtain a spatially continuous surface velocity field with a precision of fractions of a millimeter per year on distinct rock glaciers entering beacon valley we find coherent velocity patterns with peak velocities approaching 40 mm per year the ice supply from these rock glaciers nourishes the central portion of beacon valley where velocities are found to be vanishingly small and partly compensates for mass losses induced by sublimation this analysis is consistent with the tantalizing notion that beacon valley ice is the oldest on earth

combined observations of rock mass movements using satellite sar interferometry differential gps airborne digital photogrammetry and airborne photography interpretation 1 recent global warming through the related retreat of mountain glaciers causes a growing number of different slope instabilities requiring accurate and cost effective monitoring we investigate the potential of combined remote sensing observations from satellite and airborne microwave and optical sensors for an efficient survey of mountainous ground displacements the evolution of a paraglacial deep seated rock mass movement due to glacier retreat in the swiss alps has been observed between 1976 and 2008 with satellite synthetic aperture radar sar interferometry differential gps and airborne digital photogrammetry analysis of differential sar interferograms revealed an acceleration of the landslide from 4 cm yr in the slope parallel direction during the mid 1990s to more than 30 cm yr in the summer of 2008 differential gps surveys performed between the summers of 2007 and 2008 indicate seasonal variations of the landslide activity the photogrammetric analysis revealed no significant movement i e 1 cm yr between 1976 and 1995 and provides an overview of the total displacement between 1995 and 2006 with high spatial resolution in situ and airborne photography interpretation suggests that the landslide was activated at earliest by the end of the last glaciation but without any significant long lasting activity during the holocene and that the exponentially increasing reactivation since the 1990s is the result of ongoing debutressing of the valley flank due to the glacier retreat in combination with strong precipitation and snowmelt events we conclude that the employed remote sensing techniques complement each other well within a landslide hazard assessment procedure

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

transient strain accumulation and fault interaction in the eastern california shear zone satellite synthetic aperture radar interferometry reveals transient strain accumulation along the blackwater little lake fault system within the eastern california shear zone the surface strain map obtained by averaging eight years 1992 2000 of earth resource satellite ers radar data shows a 120 km long 20 kmwide zone of concentrated shear between the southern end of the 1872 owens valley earthquake surface break and the northern end of the 1992 landers earthquake surface break the observed shear zone is continuous through the garlock fault which does not show any evidence of left lateral slip during the same time period a dislocation model of the observed shear indicates right lateral slip at 7 6 3 mm yr on a vertical fault below 5 km depth a rate that is two to three times greater than the geologic rates estimated on northwest trending faults in the eastern mojave area this transient slip rate and the absence of resolvable slip on the garlock fault may be the manifestation of an oscillatory strain pattern between interacting conjugate fault systems

a surface wave study of the pacific ocean basin summary group velocity dispersion data from rayleigh waves is used to map the crustal and upper mantle structure beneath the pacific ocean basin data from the global digital seismic network gdsn provides dispersion information of a broad period range 15 300 s necessary to achieve adequate resolution down to the upper mantle no a priori assumption on regionalization is made a stochastic grid inversion method is used instead that allows the extraction of pure path dispersion data from mixed path measurements the pure path grid size is 10 10 and the entire pacific ocean basin is divided into more than 100 grids the large number of wave paths used permits sufficient resolution in the process of pure path decomposition a second generalized inversion is applied to the pure path dispersion data for each individual grid element resulting in shear velocity as a function of depth the combined output of the velocity depth functions of all grid elements gives a three dimensional crustal and upper mantle structure of the pacific ocean basin this enables cross sections and depth slicings of the region to be made down to a depth of 300 km results show a detailed picture on the lateral heterogeneity of the crustal and upper mantle the average thickness of the oceanic crust is less than 10 km a few regions in the ocean basin are identified as having a continent like crust a pronounced low velocity zone with shear velocity below 4 3 km s 1 exists nearly everywhere in the depth range from 70 to 200 km the depth and thickness of this low velocity layer vary over the pacific ocean basin but are in general conformance with the known surface tectonic picture the lateral heterogeneity and the regional distribution of velocity variations provide good baseline data for quantitative discussions of an upper mantle flow pattern and the associated dynamic process

observations of soil freezing and frost heave at inuvik northwest territories canada field observations of soil temperature moisture regime and frost heave in silty clay hummocks at inuvik northwest territories over the fall and early winter reveal that a significant amount of moisture migration and frost heave occurs within frozen soil at temperatures down to 2 4 c the field data are analysed using thermodynamic considerations and the apparent hydraulic conductivity is determined as a function of negative temperature the conductivity falls from near 7 10 9 m s 1 above 0 c to about 3 5 10 12 m s 1 at 1 c then remains fairly constant down to 2 4 c the observed decrease in heave with time is explained in terms of a diminishing water supply at the base of the active layer

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

the geomorphic significance of rock glaciers estimates of rock glacier debris volumes and headwall recession rates in west greenland to obtain knowledge on rockwall retreat rates at sites with rock glaciers an inventory of about 400 individual rock glacier sites in west greenland was carried out by means of field studies and using aerial photographs and topographic maps a number of sites with ice cored moraines beyond normal glaciers were included in the analysis for comparative purposes the estimated debris volume was compared with the size of the source headwall the result of the inventory suggests that the presence of rock glaciers indicates extraordinary high retreat rates for rock free faces above especially headwalls above glacier derived rock glaciers are exposed to high weathering rates and thereby presumably delimit critical ranges regarding altitude for headwall retreat rates the relation of such a critical altitudinal range to other regional concepts such as glaciation level gl and glacier equilibrium line is discussed from this comments are also made on the relation between various permafrost zones and the typical regional climate within the maximum headwall weathering altitude at sites with active rock glaciers finally the potential importance of this range of maximum weathering for understanding the long term evolution of high relief cold climate landscapes is emphasised

comparison of geomorphological field mapping and 2d insar mapping of periglacial landscape activity at nordnesfjellet northern norway

rayleigh wave phase velocities small scale convection and azimuthal anisotropy beneath southern california 1 we use rayleigh waves to invert for shear velocities in the upper mantle beneath southern california a one dimensional shear velocity model reveals a pronounced low velocity zone lvz from 90 to 210 km the pattern of velocity anomalies indicates that there is active small scale convection in the asthenosphere and that the dominant form of convection is three dimensional 3 d lithospheric drips and asthenospheric upwellings rather than 2 d sheets or slabs several of the features that we observe have been previously detected by body wave tomography these anomalies have been interpreted as delaminated lithosphere and consequent upwelling of the asthenosphere beneath the eastern edge of the southern sierra nevada and walker lane region sinking lithosphere beneath the southern central valley upwelling beneath the salton trough and downwelling beneath the transverse ranges our new observations provide better constraints on the lateral and vertical extent of these anomalies in addition we detect two previously undetected features a high velocity anomaly beneath the northern peninsular range and a low velocity anomaly beneath the northeastern mojave block we also estimate the azimuthal anisotropy from rayleigh wave data the strength is 1 7 at periods shorter than 100 s and decreases to below 1 at longer periods the fast direction is nearly e w the anisotropic layer is more than 300 km thick the e w fast directions in the lithosphere and sublithosphere mantle may be caused by distinct deformation mechanisms pure shear in the lithosphere due to n s tectonic shortening and simple shear in sublithosphere mantle due to mantle flow

upper mantle shear velocities beneath southern california determined from long period surface waves we used long period surface waves from teleseismic earthquakes recorded by the terrascope network to determine phase velocity dispersion of rayleigh waves up to periods of about 170 sec and of love waves up to about 150 sec this enabled us to investigate the upper mantle velocity structure beneath southern california to a depth of about 250 km ten and five earthquakes were used for rayleigh and love waves respectively the observed surface wave dispersion shows a clear love rayleigh wave discrepancy that cannot be accounted for by a simple isotropic velocity model with smooth variations of velocity with depth separate isotropic inversions for love and rayleigh wave data yield velocity models that show up to 10 anisotropy transverse isotropy however tests with synthetic love waves suggest that the relatively high love wave phase velocity could be at least partly due to interference of higher mode love waves with the fundamental mode even after this interference effect is removed about 4 anisotropy remains in the top 250 km of the mantle this anisotropy could be due to intrinsic anisotropy of olivine crystals or due to a laminated structure with alternating high and low velocity layers other possibilities include the following upper mantle heterogeneity in southern california such as the transverse range anomaly may affect love and rayleigh wave velocities differently so that it yields the apparent anisotropy higher mode love wave interference has a stronger effect than suggested by our numerical experiments using model 1066a if the high love wave velocity is due to causes other than anisotropy the rayleigh wave velocity model would represent the southern california upper mantle velocity structure the shear velocity in the upper mantle moho to 250 km of this structure is on average 3 to 4 slower than that of the tna model determined for western north america

physical properties of deep crustal reflectors in southern california from multioffset amplitude analysis analysis of reflection waveforms before stack can constrain the physical properties of reflectors in the deep crust to simplify this analysis recorded amplitudes are assumed to be reflections from weak elastic heterogeneities with these assumptions trends in reflection amplitudes with offset may indicate whether the signs of a reflector s density and rigidity contrast agree with or oppose the sign of its lame s parameter contrast the slope of the trend indicates the degree of poisson s ratio contrast no attempt is made to invert for the individual modulus or density contrasts by examining only gross amplitude versus offset avo trends deep reflections constrain some crustal properties two seismic reflection surveys in the mojave desert recorded deep reflections that show amplitude changes with offset both the 1985 calcrust ward valley survey in the eastern mojave and the 87 km cocorp mojave line 3 in the western mojave incorporate long offsets of 10 km or more prestack traces are equalized usi

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

inventorying slope movements in an alpine environment using dinsar differential sar interferometry dinsar is a technique that can be used to detect and characterize slope movements it is investigated here as a tool for establishing a detailed overview of complex slope movements at a regional scale in an alpine context this paper gives specific recommendations to use and to understand dinsar signals in mountainous areas located above the tree line excluding glaciated areas it proposes a systematic procedure based on accurate interpretations of interferometric signals from a large dinsar dataset to locate and estimate the displacement rate of moving zones the methodology was successfully applied in the western swiss alps where about 1500 moving objects were detected above the tree line using a large dataset of ers and jers interferograms dating from the 1990s the dinsar detected movements had a displacement rate ranging from a few centimeters to several meters per year and were attributed to various types of mass wasting phenomena rock glaciers landslides etc this kind of inventory derived from dinsar can be used as a preliminary tool for natural hazard management and process understanding in mountain areas as automatic data archiving and systematic acquisition of sar data are ensured worldwide for most sar sensors a similar methodology can basically be applied in many other parts of the globe also by using data from current sar sensors as long as a high resolution dem is available copyright 2014 john wiley sons ltd

monitoring surface deformation over permafrost with an improved sbas insar algorithm with emphasis on climatic factors modeling abstract changes of permafrost not only affect regional and global water circulation carbon deposit and climate warming but also influence ground ecological geophysical and biogeochemical processes in cold region monitoring surface deformation over permafrost will help to understand the dynamics of these processes assess climate changes and prevent potential damages to engineering structures underlain by permafrost this article employs an improved small baseline subset interferometric synthetic aperture radar sbas insar technique to monitor the surface deformation over the danxiong yangbajing area in the southern qinghai tibet plateau qtp with emphasis on climatic factors modeling a new deformation model considering both the external mainly climatic and internal factors such as tectonic activities and thermal character of frozen soil is constructed and introduced into the sbas insar to estimate the surface deformation over permafrost the results show that the peak to peak annual deformation over natural surface is 3 6 5 0 cm while that along the qinghai tibet highway qth and the qinghai tibet railway qtr is 2 8 3 7 cm we also find that the surface deformation over frozen soil is negatively correlated to air temperature and precipitation with the correlation being 0 80 to 0 45 and 0 95 to 0 75 respectively the root mean squares rmss of the residual un modeled deformation got by the proposed method are much smaller than that by the existing methods we also successfully examine a time lag of about 60 days between the retrieved maximal subsidence and the highest air temperature in warm seasons from may to september after compensating for this time lag the rmss of the residual deformation reduce significantly and the correlation between the deformation and the temperature rises considerably varying from 0 95 to 0 65 the method presented in this paper is more suitable to model and analyze the surface deformation in permafrost areas

post wildfire surface deformation near batagay eastern siberia detected by l band and c band insar thawing of ice rich permafrost and subsequent ground subsidence can form characteristic landforms and the resulting topography they create are collectively called thermokarst the impact of wild

shear wave velocity structure of upper mantle under taiwan from the array analysis of surface waves 1 a one dimensional shear wave velocity structure in the top 200 km of upper mantle under the central range cr of taiwan was proposed from inversion of fundamental mode rayleigh wave phase velocity which is determined from array analysis crust under cr has relatively low velocities with the thickness of 40 50 km when comparing with other regions in taiwan this might imply the existence of a mountain root upper mantle low velocity zone with s wave velocities of about 4 25 4 4 km sec is also derived the thin lid 30 km with a relatively high velocity of 4 90 km sec reveals the probable connection with the lithosphere of the eurasian plate the overall thickness of lithosphere under cr is about 80 km which is approximate to those under the adjacent sea areas of china in other words the upper mantle beneath cr is a part of the eurasian plate

thermal hydro mechanical analysis of frost heave and thaw settlement abstractfrost heave and thaw settlement are the cause of substantial damage to infrastructure in regions of seasonal freezing as well as seasonal thawing permafrost while frost heaving of soils has been researched for decades less attention has been paid to quantitative estimates of settlement and loss of strength of soils due to thawing a constitutive model is developed capable of simulating freezing and thawing of soils and associated changes in the soil strength while the porosity growth parameters describing frost heaving have been calibrated and validated for a specific soil the description of the thawing phase has not been validated due to a lack of experimental data the yielding of the frozen soil is described using the critical state concept with the pore ice content being an important parameter affecting the yield function the model was calibrated using available laboratory test data and used in the simulation of a freezing thawing cycle in the soil with embedded footing

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

seasonal dynamics of a permafrost landscape adventdalen svalbard investigated by insar abstract nordenskiold land in central spitsbergen svalbard is characterized as a high latitude high relief periglacial landscape with permafrost occurring both in mountains and lowlands freezing and thawing of the active layer causes seasonal frost heave and thaw subsidence while permafrost related mass wasting processes induce downslope ground displacements on valley sides displacement rate varies spatially and temporally depending on environmental factors in our study we apply satellite synthetic aperture radar interferometry insar to investigate the magnitude spatial distribution and timing of seasonal ground displacements in and around adventdalen using terrasar x stripmap mode 2009 2017 and sentinel 1 interferometric wide swath mode 2015 2017 sar images first we show that insar results from both sensors highlight consistent patterns and provide a comprehensive overview of the distribution of displacement rates secondly two dimensional 2d terrasar x insar results from combined ascending and descending geometries document the spatial variability of the vertical and east west horizontal displacement rates for an average of nine thawing seasons the remote sensing results are compared to a simplified geomorphological map enabling the identification of specific magnitudes and orientations of displacements for 14 selected geomorphological units finally june to december 2017 6 day sampling interval sentinel 1 time series was retrieved and compared to active layer ground temperatures from two boreholes the timing of the subsidence and heave detected by insar matches the thawing and freeze back periods measured by in situ sensors our results highlight the value of insar to obtain landscape scale knowledge about the seasonal dynamics of complex periglacial environments

the accuracy of seismic estimates of dynamic strains an evaluation using strainmeter and seismometer data from pinon flat observatory california abstract the dynamic strains associated with seismic waves may play a significant role in earthquake triggering hydrological and magmatic changes earthquake damage and ground failure we determine how accurately dynamic strains may be estimated from seismometer data and elastic wave theory by comparing such estimated strains with strains measured on a three component long base strainmeter system at pinon flat california we quantify the uncertainties and errors through cross spectral analysis of data from three regional earthquakes the m 0 4 10 17 n m st george utah m 0 4 10 17 n m little skull mountain nevada and m 0 1 10 19 n m northridge california events at distances of 470 345 and 206 km respectively our analysis indicates that in most cases the phase of the estimated strain matches that of the observed strain quite well to within the uncertainties which are about 0 1 to 0 2 cycles however the amplitudes are often systematically off at levels exceeding the uncertainties about 20 in one case the predicted strain amplitudes are nearly twice those observed we also observe significant strains tangential direction which should be zero theoretically in the worst case the rms strain exceeds the other nonzero components these nonzero strains cannot be caused by deviations of the surface wave propagation paths from the expected azimuth or by departures from the plane wave approximation we believe that distortion of the strain field by topography or material heterogeneities give rise to these complexities

stress triggering of the 1999 hector mine earthquake by transient deformation following the 1992 landers earthquake the m 7 3 june 28 1992 landers and m 7 1 october 16 1999 hector mine earthquakes california both right lateral strike slip events on nnw trending subvertical faults occurred in close proximity in space and time in a region where recurrence times for surface rupturing earthquakes are thousands of years this sug gests a causal role for the landers earthquake in triggering the hector mine earth quake previous modeling of the static stress change associated with the landers earthquake shows that the area of peak hector mine slip lies where the coulomb failure stress promoting right lateral strike slip failure was high but the nucleation point of the hector mine rupture was neutrally to weakly promoted depending on the assumed coefficient of friction possible explanations that could account for the 7 year delay between the two ruptures include background tectonic stressing dissi pation of fluid pressure gradients rate and state dependent friction effects and post landers viscoelastic relaxation of the lower crust and upper mantle by employing a viscoelastic model calibrated by geodetic data collected during the time period between the landers and hector mine events we calculate that postseismic relaxa tion produced a transient increase in coulomb failure stress of about 0 7 bars on the impending hector mine rupture surface the increase is greatest over the broad surface that includes the 1999 nucleation point and the site of peak slip further north since stress changes of magnitude greater than or equal to 0 1 bar are associated with documented causal fault interactions elsewhere viscoelastic relaxation likely con tributed to the triggering of the hector mine earthquake this interpretation relies on the assumption that the faults occupying the central mojave desert i e both the landers and hector mine rupturing faults were critically stressed just prior to the landers earthquake

estimating 1992 2000 average active layer thickness on the alaskan north slope from remotely sensed surface subsidence 1 the measurement of temporal changes in active layer thickness alt is crucial to monitoring permafrost degradation in the arctic we develop a retrieval algorithm to estimate long term average alt using thaw season surface subsidence derived from spaceborne interferometric synthetic aperture radar insar measurements our algorithm uses a model of vertical distribution of water content within the active layer accounting for soil texture organic matter and moisture we determine the 1992 2000 average alt for an 80 100 km study area of continuous permafrost on the north slope of alaska near prudhoe bay we obtain an alt of 30 50 cm over moist tundra areas and a larger alt of 50 80 cm over wet tundra areas our estimated alt values match in situ measurements at circumpolar active layer monitoring calm sites within uncertainties our results demonstrate that insar can provide alt estimates over large areas at high spatial resolution

long period ground motions and dynamic strain field of los angeles basin during large earthquakes abstract during a big earthquake along the san andreas fault in southern california high excitation and low attenuation of long period 3 to 10 sec strong ground motions will cause wave motions to propagate efficiently far from the epicentral area these ground motions could potentially be destructive to large dimension structures in the los angeles basin we performed calculations using the surface wave gaussian beam method for a 3d southern california crustal structure displacement field as well as the associated dynamic strain field produced by large propagating ruptures along the san andreas fault are evaluated results indicate that in the presence of lateral heterogeneity focusing and multipathing interference contribute significantly to a complex pattern of the displacement field and the associated dynamic strain field for a big event on the san andreas fault with a seismic moment of 1 8 10 28 dyne cm long period displacement in the los angeles basin could reach a maximum amplitude of meters in places since this calculation is fast we have evaluated the displacement field for a dense grid of points a differentiation gives the corresponding effective horizontal dynamic strain field at times the maximum effective dynamic strains may reach mid 10 3 to even 10 3 high enough to be of engineering concern this computational result probably gives the upper bound values due to the large source assumed for events of smaller seismic moment release along less extensive ruptures these results can easily be scaled down proportionally different scenarios are considered in this study with different slip distributions it is found that with a given seismic moment a more evenly distributed fault slip over the rupture surface will result in lower peak values on both displacements and dynamic strains our displacement results give similar values to those obtained by kanamori using empirical green9s functions but substantially higher than bouchon and aki9s results

receiver structure beneath the southern mojave block california an inversion of a receiver function recorded at lawrence livermore national laboratory nevada test site network station lac reveals a range of 1 d velocity structures that are consistent the observed waveform the shear velocity structure southeast of lac is relatively simple consisting of an approximately 30 to 34 km thick crust all models contain relatively sharp crust mantle boundaries with a change in velocity from about 3 5 km sec to approximately 4 6 km sec over a depth range of 4 to 6 kilometers the range of models can be roughly divided into two groups that differ mostly in the mid to lower crust the first model of the earth structure contains a large low velocity zone in the middle and lower crust shear wave velocities as low as 2 8 km sec the second model contains nearly constant velocities approximately 3 5 km sec through the middle to lower crust in contrast with the simplicity of the southeast receiver function the receiver functions corresponding to the northwest and southwest show the influence of lateral velocity heterogeneity and can at best be discussed qualitatively

stress strain changes and triggered seismicity following the mw 7 3 landers california earthquake calculations of dynamic stresses and strains constrained by broadband seismograms are used to investigate their role in generating the remotely triggered seismicity that followed the june 28 1992 mw7 3 landers california earthquake i compare straingrams and dynamic coulomb failure functions calculated for the landers earthquake at sites that did experience triggered seismicity with those at sites that did not bounds on triggering thresholds are obtained from analysis of dynamic strain spectra calculated for the landers and mw6 1 joshua tree california earthquakes at various sites combined with results of static strain investigations by others i interpret three principal results of this study with those of a companion study by gomberg and davis this issue first the dynamic elastic stress changes themselves cannot explain the spatial distribution of triggered seismicity particularly the lack of triggered activity along the san andreas fault system in addition to the requirement to exceed a coulomb failure stress level this result implies the need to invoke and satisfy the requirements of appropriate slip instability theory second results of this study are consistent with the existence of frequency or rate dependent stress strain triggering thresholds inferred from the companion study and interpreted in terms of earthquake initiation involving a competition of processes one promoting failure and the other inhibiting it such competition is also part of relevant instability theories third the triggering threshold must vary from site to site suggesting that the potential for triggering strongly depends on site characteristics and response the lack of triggering along the san andreas fault system may be correlated with the advanced maturity of its fault gouge zone the strains from the landers earthquake were either insufficient to exceed its larger critical slip distance or some other critical failure parameter or the faults failed stably as aseismic creep events variations in the triggering threshold at sites of triggered seismicity may be attributed to variations in gouge zone development and properties finally these interpretations provide ready explanations for the time delays between the landers earthquake and the triggered events

differential frost heave and sorted patterned ground field measurements and a laboratory experiment abstract small scale sorted stripes and circles dominate over the alpine regions in the upper engadin swiss alps most of these features are spaced at less than 30 cm intervals by coarse margins shallower than 5 cm monitoring of sorted stripes indicates that shallow diurnal freezing often induces differences in amount and timing of frost heave by needle ice growth between fine and coarse stripes while deeper diurnal freezing and seasonal freezing rarely differentiate heave amounts of the two materials a laboratory simulation is designed to explore the contribution of differential frost heave to the sorting process at the monitoring site the device consists of a fine part loam and a coarse part a granule layer mounted on loam freeze thaw tests with a granule mantle of 0 5 2 5 and 5 cm thick demonstrate that the heave amount on the coarse part is greatly reduced by the 5 cm thick mantle and that the coarse part always heaves later but subsides earlier than the fine as a result of this time lag in frost heaving lateral soil movement towards the coarse part is generated within the surficial soil differential heave associated with diurnal freeze thaw cycles is capable of sorting of the top 5 cm of soil

mitigation of atmospheric phase delays in insar data with application to the eastern california shear zone we present a method for estimating radar phase delays due to propagation through the troposphere and the ionosphere based on the averaging of redundant interferograms that share a common scene estimated atmospheric contributions can then be subtracted from the radar interferograms to improve measurements of surface deformation inversions using synthetic data demonstrate that this procedure can considerably reduce scatter in the time series of the line of sight displacements we demonstrate the feasibility of this method by comparing the interferometric synthetic aperture radar insar time series derived from ers 1 2 and envisat data to continuous global positioning system data from eastern california we also present results from several sites in the eastern california shear zone where anomalous deformation has been reported by previous studies including the blackwater fault the hunter mountain fault and the coso geothermal plant

reactivation of temporarily stabilized ice cored moraines in front of polythermal glaciers gravitational mass movements as the most important geomorphological agents for the redistribution of sediments a case study from ebbabreen and ragnarbreen svalbard abstract ice cored moraine complexes are prominent landforms characteristic of many polythermal glacial landsystems on svalbard usually marking their maximum little ice age extent despite being often stable over a period ranging from several years to 50 60 years the abundance of dead ice makes them potentially unstable in the future this study aims to 1 recognize the different processes that contribute to ice cored moraine degradation 2 document the spatial distribution of mass wasting sites within ice cored moraine complexes of ebbabreen and ragnarbreen svalbard 3 investigate the relationship between the distribution of mass movement sites and the topographic properties of the landscape 4 develop a model of mass wasting mechanism in a proglacial area we performed field based geomorphological mapping combined with the interpretation of aerial photographs 1960 1990 2009 high resolution satellite imagery 2013 uav based images 2014 terrestrial photographs 2011 2014 hillshade models and digital elevation models in 2013 frontal and lateral ice cored landforms occupied 3 33 km2 of the forelands of ebbabreen and ragnarbreen the total area with an unstable ice cored moraine condition was 0 57 km2 127 sites debris falls slides rolls and flows were the most important processes contributing to the reworking of glacigenic sediments and altering of their properties four different morphological site types were identified 1 near vertical ice cliffs covered with debris transformed mainly by dead ice backwasting as well as debris falls and slides 2 steep debris slopes with exposed ice cores dominated by debris slides 3 gentle sediment mantled slopes transformed by debris flows and 4 non active debris mantled areas transformed by dead ice downwasting alone the spatial and temporal activation of moraines reworking was for the most part related to local geomorphic conditions e g slope gradient occurrence of streams and meltwater channels gravitational mass movements were responsible for the redistribution of debris within the moraine complex whereas fluvial transport by meltwater exported sediments outside the little ice age moraines

forward and inverse three dimensional p wave velocity models of the southern california crust we construct a three dimensional p wave velocity model of the southern california crust by combining existing one dimensional models each describing a region defined by surface geology and calibrate the model with travel times from three explosions the model is expressed as blocks each of a given slowness the variance of the p wave travel time residuals of 1000 earthquakes relocated in and near the los angeles basin where the model is most detailed is half that of the catalog locations in the standard one dimensional model for southern california starting from the forward model we invert 21 000 p wave arrivals from earthquakes for hypocenters and block slownesses using the technique of roecker 1981 the variance of these p wave travel time residuals decreases 47 during the inversion many of the blocks representing the upper crust and midcrust are well sampled and well resolved the resulting model is useful both for locating earthquakes and for comparing the geologies of the different regions for example the velocity structure of the los angeles basin represents seismically slow sediments on top of basement rocks having velocities similar to the granitic rocks under the peninsular ranges moho is between 26 and 32 km depth in contrast the ventura basin has mostly slower sediments above a deeper higher velocity basement compared to catalog locations relocations in the final three dimensional model of 98 ml 4 earthquakes throughout southern california tend to deepen below sediment filled valleys and basins shallow in regions without sedimentary cover and have a 44 lower p wave travel time residual variance

ground motion measurement in the lake mead area nevada by differential synthetic aperture radar interferometry time series analysis probing the lithosphere rheological structure 1 we measure ground motion around the lake mead nevada using synthetic aperture radar interferometry the lake water level has fluctuated through time since impoundment in 1935 to quantify the deformation due to water level variations over the past decade and to constrain the crust and mantle rheological parameters in the lake area we analyze 241 interferograms based on 43 ers images acquired between 1992 and 2002 all interferograms have a high coherence due to arid conditions most of them show strong atmospheric artefacts tropospheric phase delays are estimated and corrected for each interferogram by analyzing the phase elevation correlation corrections are validated using data from the era40 global atmospheric reanalysis corrected interferograms are inverted pixel by pixel to solve for the time series of ground motion in the lake area temporal smoothing is added to reduce random atmospheric artefacts the observed deformation is nonlinear in time and spreads over a 50 50 km2 area we observe a 16 mm subsidence between 1995 and 1998 due to an 11 m water level increase followed by an uplift due to the water level drop after 2000 we model the deformation taking into account the loading history of the lake since 1935 a simple elastic model with parameters constrained by seismic wave velocities does not explain the amplitude of the observed motion the two layer viscoelastic model proposed by kaufmann and amelung 2000 with a mantle viscosity of 1018 pa s adjusts well the data amplitude and its spatiotemporal shape

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

solifluction rates processes and landforms a global review abstract field data on the rates of solifluction and associated parameters are compiled from the literature in an attempt to evaluate factors controlling the spatial variability in solifluction processes and landforms with special attention on the climate solifluction relationship the analyzed data originate from 46 sites over a wide range of periglacial environments from antarctic nunataks to tropical high mountains solifluction broadly defined as slow mass wasting resulting from freeze thaw action in fine textured soils involves several components needle ice creep and diurnal frost creep originating from diurnal freeze thaw action annual frost creep gelifluction and plug like flow originating from annual freeze thaw action and retrograde movement caused by soil cohesion the depth and thickness of ice lenses and freeze thaw frequency are the major controls on the spatial variation in solifluction processes near the warm margin of the solifluction affected environment diurnal freeze thaw action induces shallow but relatively rapid movement of a superficial layer 5 10 cm thick on average often creating the thin stone banked lobes typically seen on tropical high mountains in addition to diurnal movement annual frost creep and gelifluction may occur on slopes with soil climates of seasonal frost to warm permafrost dislocating a soil layer shallower than 60 cm at a rate of centimeters per year and eventually producing medium size solifluction lobes in high arctic cold permafrost regions two sided freezing can induce plug like flow of a soil mass 60 cm or thicker the correlation between process and landform suggests that the riser height of lobes is indicative of the maximum depth of movement and prevailing freeze thaw type climate change may result in new different ground freezing conditions thereby influencing the surface velocity and maximum depth of soil movement soil moisture and topography also control solifluction high moisture availability in the seasonal freezing period enhances diurnal freeze thaw action and subsequent seasonal frost heaving the latter contributes to raising the moisture content of the thawed layer and promotes gelifluction during the thawing period the slope angle defines the upper limit of the surface velocity of solifluction a diagram correlating the potential frost creep with the actual surface velocity permits an inter site comparison of the relative magnitude of solifluction components physically based modelling of periglacial slope evolution requires synthetic and more detailed field monitoring and laboratory simulations of solifluction processes

ice loss in the northeastern tibetan plateau permafrost as seen by 16 yr of esa sar missions abstract insar time series of surface deformation from 16 yr of envisat 2003 2011 and sentinel 1 2014 2019 esa satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80 000 km2 area in the permafrost of the northeastern tibetan plateau the regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography high seasonal ground movements are concentrated on shallow slopes and poor drainage areas in unconsolidated frost susceptible and fine grained sediments within glacier outwash plains braided stream plains alluvial deposits or floodplains fast subsidence due to thaw settlement takes place during june july while frost heave is intense during december january when two sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table the analysis reveals pervasive subsidence of the ground of up to 2 cm yr and increasing by a factor of 2 to 5 from 2003 to today in high relief and well drained areas the findings suggest that seasonal thaw increasingly affects ice rich layers at the permafrost table as well as high rates of widespread mass movements of non consolidated sediments the latter amplified by an increase of effects from frost heave thaw settlement

large scale insar monitoring of permafrost freeze thaw cycles on the tibetan plateau multitemporal interferometric synthetic aperture radar insar observations are used to characterize spatial variations of the permafrost active layer and its temporal evolution in northwestern tibet we develop a method to enhance insar performances for such difficult terrain conditions and construct an 8 year timeline of the surface deformation over a 60 000 km2 area the ground movement induced by the active layer s response to climate forcing is limited to cenozoic sedimentary basins and is spatially variable in both its seasonal amplitude 2 5 12 mm and multiannual trend 2 to 3 mm yr a degree day integrated model adjusted to the data indicates that subsidence occurs when the surface temperature exceeds zero may to october over areas where seasonal movements are large 8 mm the period of subsidence is delayed by 1 2 months over areas where smaller seasonal movements are observed suggesting an unsaturated soil where water occurs in the deeper part of the active layer

radarsat 2 d insar for ground displacement in permafrost terrain validation from iqaluit airport baffin island canada abstract the use of differential interferometric synthetic aperture radar d insar is rapidly gaining acceptance as a source of ground displacement information for permafrost regions the accuracy of the information however is still not well established this paper uses a stack of radarsat 2 d insar data to map seasonal ground displacement at the iqaluit airport baffin island canada the accuracy and information content of the d insar products are evaluated with a variety of ground truth data the d insar derived seasonal ground displacement patterns align well with surficial geology units and reflect the thaw settlement characteristics of the sediments they also identify localised displacement patterns in the vicinity of features such as ice wedges and frost cracks comparisons with ground settlement measurements from in situ thaw tubes indicate sub centimetre agreement in dry areas in low lying wet areas however subject to saturation and flooding the d insar stack significantly underestimates the true settlement detecting only 3 7 cm of the 8 5 cm thaw tube measurement the combination of high phase gradients and poor coherence over intermittently flooded surfaces makes it challenging to preserve reliable phase measurements in these areas information from electromagnetic surveys shows that some surface displacement is related to sub surface conditions

three dimensional s wave velocity structure in southern california 1 the three dimensional s wave velocity structure was constructed from rayleigh wave phase velocities measured using teleseismic trinet data the s wave velocity maps show some features that are much more distinct than previous tomographic results in southern california there is a clear seismic velocity contrast across the san andreas fault the north american plate side is systematically slower than the pacific plate side under the eastern california shear zone there are distinct slow velocity anomalies in the crust suggesting a close connection to lower viscosity crust previously concluded from observation of the post seismic deformation after the landers earthquake major upper mantle features include a fast velocity root under the transverse ranges which is the dominant feature in the upper mantle and a slow velocity anomaly under the salton trough our results support that the velocity contrast across the san andreas fault extends below the moho

modeling of short period surface wave propagation in southern california abstract for the 1992 landers mainshock the lateral heterogeneity of the lithosphere combined with an extended earthquake source may account for the complexity of the strong motion observations that cannot be easily interpreted by a simplified point source model in a laterally homogeneous medium both the effect of an extended source and that of lateral heterogeneity are examined using a forward modeling technique that combines distributed nonuniform slip on a fault plane in a 3d medium surface wave synthetics are constructed using surface wave gaussian beam method which allows for a mild degree of lateral heterogeneity we analyze the amplitude and waveform data of the landers strong motion recordings in southern california in order to identify the path effects and the effect of an extended source the overall source parameters of the landers earthquake are obtained by comparing synthetics with recordings at near source stations which lie within relatively homogeneous path structures this procedure yields a unilateral rupture propagating northwesterly over two distinct rupture segments with somewhat different focal mechanisms the surface wave phase velocity map is modified to fit the data recorded at larger hypocentral distances the final improved model generates a very good agreement between observations and synthetics in the presence of lateral heterogeneity the focusing defocusing and multipath interference are found to contribute significantly to the strong motion shaking in a 3d basin

teleseismic surface wave study for s wave velocity structure under an array southern california summary teleseismic surface wave data from the dense seismographic network in southern california cisn california integrated seismic network are used to construct s wave velocity maps for the region surface wave phase velocity measurements are achieved by way of a waveform matching spectral domain technique that was developed for use within the cisn array a two station phase velocity measurement technique was developed which takes advantage of the fact that for surface wave arrivals from any azimuth there are multiple pairs of cisn stations which are almost exactly on the same great circle paths to ensure the validity of this assumption particle motions were analysed for measured pairs within the network showing that the deviation between expected backazimuth from ray theory and observed backazimuths are small enough to be analysed by a simple distance correction this method was applied to 114 large earthquakes for time periods between 1999 and 2002 and led to the retrieval of phase velocity maps for rayleigh waves between 20 and 55 mhz and for love waves between 25 and 45 mhz finite frequency effect for propagating surface waves was approximately taken into consideration using a geometrical technique an ellipse determined by wavelength and great circle distance between the source and receiver can describe an influence zone for the finite frequency effect phase velocity map reconstructions using a method which incorporates this effect show minimal changes in phase velocity maps for our region but do extend solvable velocity regions inversion for s wave velocity distribution with depth shows that deep structural contrast across the san andreas extends into the upper mantle a slow velocity anomaly is evident under the southern sierras and the salton sea the latter region indicating the northward extension of tectonic activity in the gulf of california fast velocity roots that reach 60 km are found under the western part of transverse ranges and the northern peninsular ranges reconstruction of past location of the western transverse range microplate implies that these two ranges may have been adjacent to one another historically both the western transverse range fast velocity root and the peninsular range fast velocity root may be a remnant of old oceanic plate

visualizing and interpreting surface displacement patterns on unstable slopes using multi geometry satellite sar interferometry 2d insar abstract it is well known that satellite radar interferometry insar is capable of measuring surface displacement with a typical accuracy on the order of millimeters to centimeters however when the true deformation vector differs from the satellite line of sight los the sensitivity decreases and interpretation of insar deformation measurements becomes challenging by combining displacement data from extensive ascending and descending terrasar x datasets collected during the summer seasons of 2009 2014 we estimate two dimensional 2d insar surface displacement displacement data are decomposed into vertical and west east deformation dip and combined deformation vector and validated using global navigation satellite system gnss data we use the decomposed dataset to visualize variations in surface velocity and direction on unstable slopes in a periglacial environment with sporadic permafrost in northern norway by identifying areas with uplift and subsidence and detecting velocity changes downslope acceleration deceleration and related areas of extension and compression we are able to explain driving and controlling mechanisms and geomorphology in two rockslides and one area with solifluction landforms

fault creep along the southern san andreas from interferometric synthetic aperture radar permanent scatterers and stacking 1 interferometric synthetic aperture radar insar provides a practical means of mapping creep along major strike slip faults the small amplitude of the creep signal 10 mm yr combined with its short wavelength makes it difficult to extract from long time span interferograms especially in agricultural or heavily vegetated areas we utilize two approaches to extract the fault creep signal from 37 ers sar images along the southern san andreas fault first amplitude stacking is utilized to identify permanent scatterers which are then used to weight the interferogram prior to spatial filtering this weighting improves correlation and also provides a mask for poorly correlated areas second the unwrapped phase is stacked to reduce tropospheric and other short wavelength noise this combined processing enables us to recover the near field 200 m slip signal across the fault due to shallow creep displacement maps from 60 interferograms reveal a diffuse secular strain buildup punctuated by localized interseismic creep of 4 6 mm yr line of sight los 12 18 mm yr horizontal with the exception of durmid hill this entire segment of the southern san andreas experienced right lateral triggered slip of up to 10 cm during the 3 5 year period spanning the 1992 landers earthquake the deformation change following the 1999 hector mine earthquake was much smaller 1 cm and broader than for the landers event profiles across the fault during the interseismic phase show peak to trough amplitude ranging from 15 to 25 mm yr horizontal component and the minimum misfit models show a range of creeping locking depth values that fit the data

p wave image of the crust and uppermost mantle in southern california we have determined a p wave tomographic image of the crust and uppermost mantle in southern california by using 131 372 p wave arrival times from 6 437 local earthquakes recorded by the caltech usgs southern california seismic network in the past twelve years the obtained image has a spatial resolution of 25 km in the horizontal direction and 8 11 km in depth the tomographic image is found to correlate well with major surface geological features in the shallow crust sedimentary basins such as the los angeles basin ventura basin and santa maria basin are well imaged as low velocities while batholiths such as the peninsular ranges and san gabriel mountains are imaged as high velocities in the deeper crust the velocity is low beneath the mojave desert coso volcanic area and salton trough while it is high beneath the great valley continental borderland and the major basins a high velocity layer exists in the mid crust beneath the salton trough in good agreement with a previous study using seismic explosions and gravity data in the uppermost mantle the velocity is low beneath southeastern sierra nevada and the volcanic areas while it is high beneath the mojave desert and along the pacific coast