investigation of the sand sea with the tallest dunes on earth china s badain jaran sand sea abstract china s badain jaran sand sea features the tallest dunes on earth and a unique mega dune lake landscape it had been explored little until the 1990s though early scientific explorations surrounding the sand sea had begun by the early 20th century heated debates now focus on the desert environment and particularly how the mega dunes and desert lakes develop and evolve this paper reviews the status of these debates and summarizes the supporting evidences the environmental research mainly concerns formation and evolution of the sand sea and its relationship with climate change the proposed formation time ranges from the early pleistocene to the holocene opinions vary about climate change on different time scales the reconstructed climate change history is shorter than the sand sea s history with the longest record extending to the late pleistocene the mega dune research focuses on sediments dune morphology and formation processes it remains unclear whether the mega dunes result primarily from wind action control by the underlying topography or groundwater maintenance the sources of lake water are also debated but there are four main hypotheses atmospheric precipitation groundwater from nearby areas precipitation and snowmelt in remote areas such as the qilian mountains and the qinghai tibetan plateau or paleowater that formed during past periods of wet climate we believe that the sand sea deserves further study in terms of its dune geomorphology evolution and hydrology and their responses to climate change meteorological and hydrological observations and monitoring in the sand sea are particularly necessary

geomorphology and age of the marocche di dro rock avalanches trentino italy abstract the marocche di dro deposits in the lower sarca valley are some of the most distinctive rock avalanche deposits of the alps we use geomorphology and cosmogenic 36 cl exposure dating of boulders to divide the marocche di dro deposits into two rock avalanche bodies the marocca principale to the north and the kas to the south the deposits were previously undated and had been mapped as up to five different events the largest event marocca principale which comprises an estimated 1000 10 6 m 3 of predominantly rotzo formation limestones occurred 5300 860 yr ago the release area is located mainly in the alcove between mt casale and mt granzoline but likely extends all the way to mt brento the kas event took place 1080 160 yr ago with detachment below mt brento the kas debris with an estimated volume of 300 10 6 m 3 buried the southern third of the marocca principale deposit kas presents a barren stark landscape dominated by house sized tovel member rotzo formation boulders bearing distinctive chert lenses both the extreme relief of the rock wall more than 1300 m and the tectonic setting predispose the range front to massive failure for the two events initially translational movement likely quickly evolved into complex failure and massive collapse run out across the valley of several kilometers and run up on the opposite slope of hundreds of meters followed a summary of all dated and large historical landslides in the alps underlines the periods of enhanced slope activity discussed in the literature 10 9 kyr 5 3 kyr and 2 1 kyr the latter especially for the southern alps no deposits of the first temporal cluster are found at marocche di dro the age of marocca principale at 5300 860 yr suggests occurrence during the second period failure may have been related to the shift to wetter colder climate at the transition from the middle to the late holocene nevertheless a seismic trigger cannot be ruled out for the kas rock avalanche at 1080 160 yr ago we implicate the middle adige valley 1046 ce earthquake as trigger its epicentral distance is much closer to the sarca valley in comparison to that of the verona earthquake 1117 ce

landslides and climate change in the italian dolomites since the late glacial abstract the paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the italian dolomites since the late glacial after an introduction on the state of the art with particular reference to the alpine region the results of recent investigations in the two study sites are illustrated at cortina d ampezzo several landslides were dated mainly by the radiocarbon method the most ancient landslide event there involved large rock slides which affected the dolomitic slopes following the withdrawal of glaciers after the last glacial maximum lgm and also slides and flows mainly occurring in pelitic materials of the valley floors from 13 000 to 10 000 cal bp a later series of flows occurred between 5500 and 2500 cal bp in the upper badia valley alta badia the most ancient events go back to 10 000 and 9000 cal bp and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m more recent earth flows involving more modest amounts of material took place between 6500 and 2300 cal bp by analysing the dates from the two study areas it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the late glacial and the holocene and between the atlantic and the subboreal and to compare the results with those derived from other european regions the types and causes of landslides taking place in these two periods were substantially different reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered finally notwithstanding the importance of non climatic causes such as geological structural factors and possible human influences it is concluded that many of the dated landslides can be considered as indicators of climatic change

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

equilibrium versus disequilibrium of barchan dunes abstract barchans are crescentic dunes which occur in mainly mono directional winds shape aspect ratios and velocities of these dunes have been studied as if they were in equilibrium however following a study of the shape and migration of 11 barchans of different sizes for 18 months in the field on moroccan atlantic sahara we show that they only appear to be in a stationary state if studied over a long timeframe at the scale of the year or several years but are never in equilibrium at the scale of weeks or months rather they are always trying to reach a possible equilibrium state but never have enough time to accomplish this this may be the main reason for the large variation observed in previous measurements and justifies some caution in what can be deduced from them

an extensive region of off ridge normal faulting earthquakes in the southern indian ocean an unusually large number of off ridge earthquakes have occurred within a broad region astride the southeast indian ridge the source mechanisms of nine of these earthquakes in lithosphere from 4 to 27 m y old have been determined with a formal inversion technique based on matching observed and synthetic p and sh waves all events occur in the oceanic mantle from 8 to 22 km below the seafloor the seismic moment and duration of faulting obtained from the inversion constrain the stress drop to lie between a few tens of bars and a few hundred bars for most of the events all of the off ridge earthquakes are characterized by normal faulting mechanisms with the t axes nearly parallel to the nearby ridge axis in sharp contrast to typical mid ocean ridge or intraplate earthquakes a variety of possible tectonic processes which might produce normal faulting in young oceanic lithosphere are considered as possible causes including bending stresses thermal stresses of various origins differential subsidence at a fracture zone off ridge volcanism latitudinal plate motions on a nonspherical earth basal shear stress from small scale convection and plate wide perturbations of the stress field due to the continental collision between india and asia no single mechanism is adequate to explain all the observed off ridge normal faulting earthquakes an apparent asymmetry in the observed seismicity with respect to the ridge suggests that the earthquakes on the antarctic and indian plates are caused by different processes the antarctic plate events can be satisfactorily attributed to the release of thermal and bending stresses associated with a residual depth anomaly between the kerguelen plateau and the southeast indian ridge a region which has been suggested as the site of a horizontal pipe for flow in the asthenosphere from the kerguelen hot spot to the vicinity of amsterdam and st paul islands on the southeast indian ridge the off ridge earthquakes in the indian plate are speculatively attributed to part of the plate wide response of the lithosphere to the ongoing continental collision

rock slope failure in the british mountains abstract in this first full review of extant quaternary rock slope failure rsf in the british mountains we provide a near complete inventory of 1082 sites 40 being rock slope deformations 40 arrested rockslides and 20 rock avalanches current rsf activity is negligible and this relict population is predominantly paraglacial with a parafluvial minority its spatial distribution is perplexing with rsf density varying greatly both regionally and locally in the scottish highlands eight main clusters account for 76 of rsf area in 15 of the montane area local concentrations occur in all the british ranges across high and low relief in core and peripheral locations and on varied geological and glaciological domains as conversely do extensive areas of sparsity even in similar lithologies generic interpretations are thus precluded geology is only a secondary control an association with concentrated erosion of bedrock ceb is proposed as a driver of intensified slope stresses ceb is most evident at those glacial breaches of main divides where the most vigorous recent incision is inferred and also in some trough heads a clear association between rsfs and these late developing breaches is demonstrated in the highlands in 42 localities with sparsity away from them it is also seen in seven lake district localities glaciological models identify ice sheet volatility capable of driving breach ramification high magnitude paleoseismic events are generally unlikely to have provoked rsf clusters a few candidates are considered rsf has been underrated as an agent of mountain landscape evolution in britain its spatio temporal incidence may assist in calibrating regional ice sheet models and in assessing climate change impacts we argue that the ceb rsf association has global relevance in identifying primary drivers of mass movement in bedrock

investigation of reddening patterns of dune sands the megabarchans of al ghord lahmar khnifiss national park south west of morocco abstract the present paper aims to investigate the geological and environmental parameters controlling the redness of sand at the megabarchans located nearby khnifiss lagoon sw of morocco mineralogical investigation either by laboratory or remotely sensed data showed the abundance of a mixed composition of quartz carbonates and mafic minerals with a dominance of hematite quartz coated grains also grain size analysis revealed the heterogeneity of the megabarchans sand and the dominance of fine and well to very well sorted sand with a mean grains size of 0 2 mm mineralogical species were adequately distributed according to their size and density we noted the dominance of iron bearing minerals including magnetite hematite ilmenite ulvospinel and pyroxenes in the very fine fraction 63 m knew a dominance of hematite coated quartz carbonates and feldspars these both fractions are carried by wind with almost the same threshold motion which meant that the size could compensate the density that explains their deposition in the same environment the megabarchans migrated over the past 325 years with a rate of 2 m year thus grains may undergo many turnover cycles until they can be reactivated by wind climatic parameters such as precipitations with 164 mm year the frequent stormy events that bring a flash flooding in addition to the high humidity and important fog and dew provide a source of moisture that make the megabarchans a moistened environment encouraging the iron oxidation thus the abundance of a source of iron and a source of moisture in addition to the stability of the megabarchans and their water holding capacity remained the effective factors that led to the megabarchans redness

observation and inversion of surface wave group velocities across central india abstract surface wave group velocities across central india are measured from computer plots of frequency time analysis using multiple filter technique periods range from 5 to 56 sec for fundamental mode rayleigh wave 5 to 16 sec for first higher mode rayleigh wave and 5 to 49 sec for fundamental mode love wave the wave paths from koyna earthquakes to bokaro cross purely through the peninsular plateau the group velocities for these paths are found to be similar to those of surface waves recorded at poona from earthquake which lie to the northeast of bokaro in sub himalayan regions from this it is concluded that the shield structure of the peninsula extends to the sub himalayan regions to northeast of the peninsular plateu with a negligible part of sedimentary layer group velocities of fundamental mode rayleigh and love waves are also obtained for the paths from koyna earthquakes to shillong and are found to be similar to the above mentioned group velocities except at very low periods where group velocities are affected by the small part of each path through thick sedimentary layer of bengal basin northern limit of this basin sedimentary layer has been identified mean and standard deviation of observed group velocity at each period are obtained for each of rayleigh fundamental rayleigh first higher and love fundamental modes the group velocities closely agree with those obtained earlier for the path between new delhi and kodaikanal and are also found to be similar to those observed in some shield regions monte carlo inversion method is applied and crust and upper mantle structure of the indian shield across central india is obtained crustal structure obtained shows a marked resemblance to the results obtained earlier through body wave study

rainfall patterns and critical values associated with landslides in povoacao county sao miguel island azores relationships with the north atlantic oscillation sao miguel island azores has been affected by hundreds of destructive landslide episodes in the last five centuries triggered either by earthquakes volcanic eruptions or rainfall episodes which were responsible for many deaths and very important economic losses among the instability causes meteorological factors are of primary importance on povoacao county namely the high recurrence rate of calamitous rainfall triggering landslides the most recent catastrophic episode took place on the 31st october 1997 when almost 1000 soil slips and debris flows were triggered and 29 people died in the ribeira quente village the role of rainfall on regional landslide activity was analysed applying cumulative rainfall methods the method comprises the reconstruction of both absolute and calibrated antecedent rainfalls associated with each major landslide event the critical rainfall combination amount duration responsible for each landslide event was assessed and a rainfall critical threshold for landslide occurrence was calculated rainfall triggered landslides in the study area are ruled by the function i 144 06 d 0 5551 and they are related both to short duration precipitation events 1 3 days with high average intensity between 78 and 144 mm day and long lasting rainfall episodes 1 5 months with a lower intensity between 9 and 22 mm day the impact of the north atlantic oscillation nao on the regional precipitation regime was evaluated it is shown that the monthly precipitation of sao miguel is largely modulated by the nao mode presenting a significant negative correlation with the nao index this result arises from the nao control on the travelling latitude of most storm tracks that cross the northern atlantic ocean copyright 2007 john wiley sons ltd

a spatio temporal landslide inventory for the nw of spain bapa database abstract a landslide database has been created for the principality of asturias nw spain the bapa base de datos de argayos del principado de asturias principality of asturias landslide database data collection is mainly performed through searching local newspaper archives moreover a bapa app and a bapa website http geol uniovi es bapa have been developed to obtain additional information from citizens and institutions presently the dataset covers the period 1980 2015 recording 2063 individual landslides the use of free cartographic servers such as google maps google street view and iberpix government of spain combined with the spatial descriptions and pictures contained in the press news makes it possible to assess different levels of spatial accuracy in the database 59 of the records show an exact spatial location and 51 of the records provided accurate dates showing the usefulness of press archives as temporal records thus 32 of the landslides show the highest spatial and temporal accuracy levels the database also gathers information about the type and characteristics of the landslides the triggering factors and the damage and costs caused field work was conducted to validate the methodology used in assessing the spatial location temporal occurrence and characteristics of the landslides

mineralogical and gemorphological characterization of sand dunes in the eastern part of united arab emirates using orbital remote sensing integrated with field investigations abstract in this study landsat 7 etm data sets were used to study the geomorphology and mineralogy of different dune types in the eastern part of abu dhabi in united arab emirates the extraction and mapping of the dominant mineral phase of the investigated sand dunes were carried out using image processing integrated with field techniques band ratios 6 4 and 5 7 were very useful for mineralogical distinction of i high mafic content areas ratio 5 7 and ii carbonate and quartz content ratio 6 4 the results of the present study show that these dunes are classified into several main classes based on composition the first class is low dunes composed of a mixture of quartz and carbonate the second class is carbonate rich the third quartz rich and the fourth mafic mineral rich morphologically the dunes in the investigated area belong to two main types the first is linear and is trending ne sw this type shows transitional change in mineralogy from carbonate rich components to iron oxide rich components this mineral gradient was observed on landsat images as spectral variations and color tones and was confirmed from ground truth data the second type is star dunes and appears in images as radially symmetrical to mound shape that characterize multidirectional wind systems the results of this study show that multispectral data can be used to differentiate between different dune types and their associated mineralogy and to reveal information on the dynamic processes shaping dunes such as prevailing wind directions

investigation of the controls on dune colour in the namib sand sea using mineral magnetic analyses abstract the geological and environmental controls upon the pattern of increasing dune redness inland in the namib sand sea are investigated using mineral magnetic measurements satellite imagery and dithionite extractable iron results suggest whole grains or inclusions within grains dominate the iron oxide assemblage but the sediment colour is more strongly influenced by a second component which consists of haematite within the grain coatings the magnetic data suggest that source materials exert at least a partial control on dune colour in this field setting evidence for the influence of other factors e g age and climatic gradient is also present

q structure beneath the tibetan plateau from the inversion of love and rayleigh wave attenuation data abstract the fundamental mode love and rayleigh waves generated by ten earthquakes and recorded across the tibet plateau at que lah ndi nil kbl shl chg sng and hkg are analysed love and rayleigh wave attenuation coefficients are obtained at time periods of 5 120 s using the spectral amplitudes of these waves for 23 different paths love wave attenuation coefficient varies from 0 0021 km 1 at a period of 10 s to 0 0002 km 1 at a period of 90 s attaining two maxima at time periods of 10 and 115 s and two minima at time periods of 25 and 90 s the rayleigh wave attenuation coefficient also shows a similar trend the very low value for the dissipation factor q obtained in this study suggests high dissipation across the tibetan paths backus gilbert inversion theory is applied to these surface wave attenuation data to obtain average q 1 models for the crust and uppermost mantle beneath the tibetan plateau independent inversion of love and rayleigh wave attenuation data shows very high attenuation at a depth of 50 120 km q 10 the simultaneous inversion of the love and rayleigh wave data yields a model which includes alternating regions of high and low q 1 values this model also shows a zone of high attenuating material at a depth of 40 120 km the very high inferred attenuation at a depth of 40 120 km supports the hypothesis that the tibetan plateau was formed by horizontal compression and that thickening occurred after the collision of the indian and eurasian plates

dust production and the release of iron oxides resulting from the aeolian abrasion of natural dune sands global dust trajectories indicate that significant quantities of aeolian transported iron oxides originate in contemporary dryland areas one potential source is the iron rich clay coatings that characterize many sand sized particles in desert dunefields this paper uses laboratory experiments to determine the rate at which these coatings can be removed from dune sands by aeolian abrasion the coatings impart a red colour to the grains to which previous researchers have assigned variable geomorphological significance the quantities or iron removed during a 120 hour abrasion experiment are small 99 mg kg 1 and difficult to detect by eye however high resolution spectroscopy clearly indicates that ferric oxides are released during abrasion and the reflectance of the particles alters one of the products of aeolian abrasion is fine particles 10 mum diameter with the potential for long distance transport copyright c 2004 john wiley sons ltd

recent glacier retreat exceeds internal variability glacier fluctuations exclusively due to internal variations in the climate system are simulated using downscaled integrations of the echam4 opyc coupled general circulation model gcm a process based modeling approach using a mass balance model of intermediate complexity and a dynamic ice flow model considering simple shearing flow and sliding are applied multimillennia records of glacier length fluctuations for nigardsbreen norway and rhonegletscher switzerland are simulated using autoregressive processes determined by statistically downscaled gcm experiments return periods and probabilities of specific glacier length changes using gcm integrations excluding external forcings such as solar irradiation changes volcanic or anthropogenic effects are analyzed and compared to historical glacier length records preindustrial fluctuations of the glaciers as far as observed or reconstructed including their advance during the little ice age can be explained by internal variability in the climate system as represented by a gcm however fluctuations comparable to the present day glacier retreat exceed any variation simulated by the gcm control experiments and must be caused by external forcing with anthropogenic forcing being a likely candidate

thermal effects of thrust faulting abstract calculations based on simple models of overthrust sheets in crystalline basement rocks show that significant thermal effects may result from their movements if rates are sufficiently high e g plate tectonic rates the thrust sheets sufficiently thick 5 10 and 15 km are modelled here the distances moved sufficiently large and for reasonable values of the coefficient of friction along the thrust plane overthrusting can cause metamorphic mineral zonations and heat flow anomalies observable in the field regions where large scale overthrusting has occurred should be characterized by a decrease with depth of grade of metamorphic mineral assemblages and anomalously low heat flow the theoretical effects are presented as a series of maximum temperature vs depth and heat flow vs time plots

quasi continental oceanic structure beneath the arabian fan sediments from observed surface wave dispersion studies the fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at seismographic stations along the western margins of india and pakistan trivandrum kodaikanal goa bombay poona new delhi nillore and quetta are used to estimate the crustal structure beneath the arabian fan sediments the sedimentary thickness is determined from the observed higher mode data the observed dispersion data suggest an increase in crustal thickness northward from an approximately 16 km crustal thickness at the southern tip of india trivandrum to an approximately 28 km crustal thickness at the regions of 20 n and above latitude with an overlying 6 km sedimentary thickness this gradual increase in crustal thickness in the northward direction and the attaining of quasi continental oceanic transition from continent to ocean structure beneath the arabian fan sediments suggest that the mohorovicic discontinuity may have resulted from a change in crystal structure due to increase of pressure and not a phase change the same material exists beneath the moho and it does not represent the boundary between two different materials the transition has given rise to crustal thickening in the northward direction another possible explanation is that the increase in hydrostatic pressure due to the load exerted by a large sedimentary column together with horizontal pressure caused by the collision of indian and eurasian plates has given rise to an increase in temperature near the moho because of the thermal blanketing effect of this large sedimentary column an inferred rise in temperature may have either changed the upper mantle into material with crustal like velocity or may have given rise to metamorphism of earlier existing sedimentary rocks an inferred high temperature near the moho depth beneath the arabian fan sediments is in close agreement with the high attenuating zone at the shallow depth 30 to 45 km as determined by singh 1987

spectral signs of aeolian activity around a sand dune belt in northern algeria abstract dune color has been used to investigate the provenance stabilization and age of the sand here we look for signs of aeolian activity in the colors of a sand dune belt in northern algeria on the one hand visible and near infrared spectral analyses of satellite images and laboratory samples showed reddish yellowish and whitish sands depending on the amount of gypsum particles and fe oxides coating quartz grains specifically the dithionite extractable fe content was related to a redness index calculated from remote sensing data and the abundance of hematite estimated in the second derivative of the kubelka munk function paralleled the cielab hue angle of sand samples on the other hand a spatiotemporal analysis showed that the reddish sand had undergone a continuous remobilization and dispersion throughout the area reaching two large salt flats sabkhas with seasonal water yellowish and whitish sands appeared as patches on the periphery of these sabkhas and along the dune belt exhibiting percussion marks and dissolution pits on the surface of quartz grains taken together the results suggest that the reddish sand partially loses its fe oxide coatings by mechanical abrasion in the entrainment and reductive dissolution in the sabkhas during waterlogging becoming yellowish the periodic reactivation by wind of reddish and yellowish grains together with whitish gypsum particles formed by evaporation as the sabkhas dry up may explain the sorting of grains according to their mineralogy and size along the sand dune belt resulting in striking color changes accordingly color reflects sand movements and chemical processes taking place in this dune system

remote sensing based assessment of hazards from glacier lake outbursts a case study in the swiss alps glacier lakes are a common phenomenon in high mountain areas outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure in several high mountain ranges around the world a grave uncertainty about the hazard potential of glacier lakes still exists especially with respect to the effects of accelerating rates of glacier retreat as a consequence of atmospheric warming area wide detection and modeling of glacier lake hazard potentials is therefore a major challenge in this study an approach integrating three scale levels allows for the progressive focus on critical glacier lakes remote sensing methods for application in glacier lake hazard assessment are presented and include channel indexing data fusion and change detection each method matches the requirements of a certain scale level for estimating potential disaster amplitudes assessments must be made of maximum discharge and runout distance of outbursts floods and debris flows existing empirical relations are evaluated and complementary ones as derived from available data are proposed tests with observations from a recent outburst event from a moraine dammed lake in the swiss alps show the basic applicability of the proposed techniques and the usefulness of empirical relations for first hazard assessments in particular the observed runout distance of the debris flow resulting from the outburst does not exceed the empirically estimated maximum runout distance a list of decision criteria and related remote sensing techniques are discussed in conclusion such a list is an essential tool for evaluating the hazard potential of a lake a systematic application of remote sensing based methods for glacier lake hazard assessment is recommended

a deterministic seismic hazard map of india and adjacent areas a seismic hazard map of the territory of india and adjacent areas has been prepared using a deterministic approach based on the computation of synthetic seismograms complete with all main phases the input data set consists of structural models seismogenic zones focal mechanisms and earthquake catalogues there are few probabilistic hazard maps available for the indian subcontinent however this is the first study aimed at producing a deterministic seismic hazard map for the indian region using realistic strong ground motion modelling with the knowledge of the physical process of earthquake generation the level of seismicity and wave propagation in anelastic media synthetic seismograms at a frequency of 1 hz have been generated at a regular grid of 0 2 x 0 2 by the modal summation technique the seismic hazard expressed in terms of maximum displacement d m a x maximum velocity v m a x and design ground acceleration dga has been extracted from the synthetic signals and mapped on a regular grid over the studied territory the estimated values of the peak ground acceleration are compared with the observed data available for the himalayan region and are found to be in agreement many parts of the himalayan region have dga values exceeding 0 6 g the epicentral areas of the great assam earthquakes of 1897 and 1950 in northeast india represent the maximum hazard with dga values reaching 1 2 1 3 g the peak velocity and displacement in the same region is estimated as 120 177 cm s 1 and 60 90 cm respectively

barchan dune corridors field characterization and investigation of control parameters 1 the structure of the barchan field located between tarfaya and laayoune atlantic sahara morocco is quantitatively investigated and compared to that in la pampa de la joya arequipa peru on the basis of field measurements we show how the volume the velocity and the output sand flux of a dune can be computed from the value of its body and horn widths the dune size distribution is obtained from the analysis of aerial photographs it shows that these fields are in a statistically homogeneous state along the wind direction and present a corridor structure in the transverse direction in which the dunes have a rather well selected size investigating the possible external parameters controlling these corridors we demonstrate that none among topography granulometry wind and sand flux is relevant we finally discuss the dynamical processes at work in these fields collisions and wind fluctuations and investigate the way they could regulate the size of the dunes furthermore we show that the overall sand flux transported by a dune field is smaller than the maximum transport that could be reached in the absence of dunes i e in saltation over the solid ground

mapping the distribution of weathered pleistocene wadi deposits in southern jordan using aster spot 5 data and laboratory spectroscopic analysis abstract in the arid regions of the levant ancient wadi fills act as a terrestrial sedimentary archive with a high potential for preserving archaeological findings this current study combines remote sensing with laboratory vis spectroscopy to investigate the spatial distribution of alluvial wadi fills in a small catchment in southern jordan due to its homogeneous sandstone geology the composition of the alluvial sediments is highly influenced by the local bedrock whilst fluvial relocation and surface weathering processes initiated a secondary alteration of dominant iron oxides fe 3 the differences in mineralogical composition of the sediments enable the detection and mapping of wadi deposits by remote sensing using different spectral combinations of aster and spot 5 satellite images additionally laboratory measurements of reflectance spectra were applied on selected surface samples and soil sections from the study area in order to verify the information derived from remote sensing and to quantify the degree of surface weathering and pedogenic processes the results show that an initial transformation from hematite to goethite is the dominant process related to the recent arid conditions in the study area furthermore it is possible to predict potential new archaeological finding areas using remote sensing techniques

crust and upper mantle velocity structure beneath the northern and central indian ocean from the phase and group velocity of rayleigh and love waves abstract fundamental mode rayleigh and love waves generated by nine earthquakes which occurred in the central indian ocean with epicentres extending to 40 s and recorded at seven wwssn stations of central asia have been used to determine the phase and group velocity along various paths across the northern and central indian ocean the dispersion characteristics of rayleigh and love waves show a thick crust of 23 km thickness this anomalous crustal thickening having quasi continental oceanic structure may be explained by assuming the gradual transformation of top mantle material into material having either crustal like velocity or slightly lower than moho velocity p wave velocity 7 72 km s 1 s wave velocity 4 45 km s 1 the velocity structure down to a depth of 200 km has been obtained across the northern and central indian ocean a low velocity zone of 90 km with p wave velocity of 7 85 km s 1 and s wave velocity of 4 37 km s 1 is estimated to be centred at a depth of 78 km from the water surface this low shear velocity in the mantle may be caused by the partial melting and elevated temperature there the observed dispersion data for rayleigh and love waves also exhibit a strong anisotropy along different paths in the crust and upper mantle the observed dispersion data for rayleigh and love waves that cross the ninety east ridge are characterized by lower phase and group velocities as compared to waves having paths in a more western direction than this ridge axis however the phase velocities for rayleigh and love waves are characterized by lower values across the ninety east ridge as compared to the normal oceanic structure

a new insight into seismic attenuation characteristics of northwest himalaya and its surrounding region implications to structural heterogeneities and earthquake hazards abstract the frequency dependent attenuation characteristics of p waves q s waves q and coda waves qc in north west nw himalaya and its surrounding region have been estimated using 515 micro to moderate earthquakes 2 5 mw 5 0 recorded from january 2008 to november 2015 for a central frequency range fc varying from 1 5 to 12 hz average attenuation relationships of qc q and q found as qc 126 94 37 9 f 1 122 0 06 q 65 127 5 7 f 1 1261 0 03 and q 93 855 3 05 f 1 1145 0 01 for the region it is found that the nature and extent of seismic attenuation are different for different seismotectonic belts consisted of various kinds of fault systems distributed into the indo gangetic plain igp the sub himalaya sh the lesser himalaya lh and the higher himalaya hh geotectonic segments beneath nw himalaya and its surrounding region material property heterogeneity beneath the subsurface earth is playing an important role in influencing the degree of release of seismic energy in nw himalaya and its surrounding region because of varying attenuative property in different geotectonic segments q 1 c hh q 1 c igp q 1 c sh q 1 c lh this study may help in better understanding of structural heterogeneities that control the nature and extent of seismogenesis which in turn may help in assessing seismic hazards through estimates of strong ground motion by computing earthquake source parameters our schematic model for nw himalaya and its surrounding region shed an important light on attenuative characteristics of different tectonic blocks associated with both local and regional fault systems that dictate the source characteristics and potential of earthquake hazards of the region

the rock avalanche of february 1995 at claix french alps abstract the sedimentology of a rock avalanche involving ca 7 10 3 m 3 that happened on february 1995 at claix the french alps is analysed here the talus shows a proximal depression due to the impact of the debris then a grooved area with few mainly sandy silt deposits and a downslope accumulation of coarse debris that reaches up to 3 m in thickness the material underwent mass movement as demonstrated by the steep distal front the strong fabric strength and the thrust planes the greatest part of the deposits consists of a clast supported to partially openwork debris with angular clasts over a sheared matrix supported basal layer the largest blocks often more than 1 m in length are concentrated at the surface and the front the overall sedimentological characteristics are similar to those of the small dry grain flows that occur usually on rockfall talus except for the abundance of fine grained particles that results from intense cataclasis during flow it is suggested that the deposits of such medium scale rock avalanches probably not uncommon in seismic regions may have been confused in previous studies with other slope mechanisms such as debris flow and rockfall

earthquake source mechanisms from body waveform inversion and intraplate tectonics in the northern indian ocean double couple point source parameters for 11 of the largest intraplate earthquakes in the northern indian ocean during the last 20 y were determined from a formal inversion of long period p and sh waveforms nine of the events have centroid depths at least 17 km below the seafloor well into the upper mantle two have centroid depths as great as 39 km using the source mechanisms of these earthquakes we distinguish two major intraplate tectonic provinces in the northern indian ocean to the west of the ninetyeast ridge in the southern bay of bengal intraplate earthquakes have thrust faulting mechanisms with p axes oriented n s the centroid depths of these earthquakes range from 27 to 39 km below the seafloor lithospheric shortening in this region is thus accomplished by thrust faulting in the strong core of the oceanic upper mantle while other geophysical evidence suggests that shallow sedimentary and crustal layers apparently deform predominantly by folding in the immediate vicinity of the ninetyeast ridge earthquakes display strike slip mechanisms with left lateral motion on planes parallel to the ridge this type of faulting occurs from at least 10 s to the northern end of the ninetyeast ridge near 10 n where the ridge meets the sunda arc seismic activity diminishes to the east of the ninetyeast ridge but is also characterized by strike slip faulting despite these variations in deformational style the inferred orientation of greatest compressive stress in the northern indian ocean displays a consistent long wavelength pattern over a large portion of the indian plate varying smoothly from nearly n s in the bay of bengal to nw se in the northeastern indian ocean this plate wide stress pattern and the high level of intraplate seismicity in the northern indian ocean are likely the results of substantial resistance along the himalayan continental collision zone to the continued northward motion of the western portion of the indian plate oceanic intraplate earthquakes in other regions where the level of deviatoric stress associated with the long wavelength part of the stress field is likely to be smaller need not be comparably reliable indicators of the plate wide stress field

anelasticity of the crust and upper mantle beneath the pacific ocean from the inversion of observed surface wave attenuation summary backus gilbert inversion theory is applied to a new set of surface wave attenuation data to obtain average q 1 models for the crust and upper mantle beneath the pacific ocean the favoured model is obtained from the inversion of rayleigh wave data alone it includes an increase in q 1 or decrease in q at depths corresponding to the thickness of the litho sphere as determined from surface wave velocity studies a thick zone of high q 1 or low q in the upper mantle and decreasing q 1 deeper in the mantle the mean q 1 values for the lithosphere are lower than those previously determined for the lower crust beneath continents simultaneous inversions of the love and rayleigh wave data yield models which include thin alternating regions of high and low q 1 values independent inversions of the love and rayleigh wave data yield models which differ in their anelastic properties at depths between 20 and 120km these latter two types of models probably reflect systematic errors in the love wave data due to higher mode interference or complexities along the propagation path

super mobility of hot indian lithosphere negi j g pandey o p and agrawal p k 1986 super mobility of hot indian lithosphere tectonoph vsics 131 147 156 the great mobility of the indian subcontinent during the last 180 million years 9000 km of south north motion with an anticlockwise rotation of about 60 o has long been a major puzzle for theorists of plate tectonics a relative analysis of the available heat flow data the estimated temperature depth regime of india and the gravity anomalies reveals that the indian lithosphere does not have the characteristics of a typical shield zone and that it has higher radioactivity smaller viscous drag decidedly low viscosity of 10 p lower density and a well defined low velocity zone as compared to other shield areas of the world these factors appear to contribute significantly to the faster northward movement of the thin indian lithosphere as compared to the almost immobile african plate

quatre cas d avalanches rocheuses dans les alpes francaises l exceptionnelle mobilite de certaines avalanches rocheuses a amene les chercheurs a s interesser davantage au comportement des ecroulements granulaires les recentes conferences scientifiques internationales ont mis en lumiere la necessite d investiguer les aspects physiques et mecaniques de ce type d ecroulement granulaire c est dans cette optique qu une premiere phase d etude a conduit a la reconnaissance de quatre sites d ecroulements rocheux dans les alpes francaises nos observations portent sur les mecanismes de rupture l influence de la morphologie sur le transport et la mise en place des debris presence de l eau et son role dans ces materiaux enfin les quatre ecroulements rocheux suivent la relation denivele distance de parcours versus volume et ce malgre les faibles volumes impliques dans au moins deux de ces cas

deciphering the effect of climate change on landslide activity a review abstract increased landslide activity is commonly listed as an expected impact of human induced climate change this paper examines the theoretical and empirical bases for this assertion it identifies the mechanisms by which climate can induce landsliding and examines the manner in which these mechanisms may respond to changes in a range of climatic parameters it is argued that inherent limiting stability factors which vary with different terrain conditions and landslide types ultimately govern the nature of response to changing climate several modelling approaches are evaluated on the basis of their potential to predict landslide response to climate projections given reliable input data of appropriate form and resolution the existing slope stability hydrological and statistical models are for the most part capable of yielding useful prognoses on occurrence reactivation magnitude and frequency of landsliding while there is a strong theoretical basis for increased landslide activity as a result of predicted climate change there remains a high level of uncertainty resulting from the margins of error inherent in scenario driven global climate predictions and the lack of sufficient spatial resolution of currently available downscaled projections examples from new zealand are used to illustrate the extent to which changes resulting from human activity have affected slope stability changes resulting from human activity are seen as a factor of equal if not greater importance than climate change in affecting the temporal and spatial occurrence of landslides

constraints on plate motions in southern pakistan and the northern arabian sea from the focal mechanisms of small earthquakes the focal mechanism and depth were determined for nine small earthquakes m0 1025 dyn cm m 5 5 that occurred in southern pakistan and the northern arabian sea from an analysis of the vertical component of rayleigh waves in combination with limited first motion data focal parameters were determined from the rayleigh waves by using an event pair method of analysis for earthquakes that are located very close to each other 50 km the event pair method is able to remove a significant proportion of propagation effects at all periods in the range of interest 20 50 s for events separated by more than 100 km the propagation effects are reduced for only the longer periods 40 50 s the earthquakes that were studied provide evidence for a model of plate interactions in the vicinity of the southern pakistan triple junction the owen fracture zone is a transform fault that accommodates right lateral motion between the indian and arabian plates the plate boundary in the vicinity of the murray ridge is also partially made up of transform segments that strike subparallel to the owen fracture zone spreading centers may also exist in the vicinity of the murray ridge but were not documented by seismic or other evidence the slip azimuths for earthquakes along this boundary are significantly more northerly than those predicted by various regional and worldwide models of plate motion the arabian plate is being subducted beneath the eurasian plate along the southern coast of pakistan slip vectors for earthquakes along this boundary trend northnortheasterly in general agreement with predicted directions left lateral motion is documented along the boundary between the indian and eurasian plates in southern pakistan the predicted direction of relative motion between these plates is not significantly different from that observed two of the earthquakes studied appear to be intraplate in nature the depth and focal mechanism of one intraplate event which may have occurred within the accretionary prism along the makran coast however are based on limited data the other intraplate earthquake occurred within the sedimentary deposits along the western edge of the indian subcontinent near the indian eurasian plate boundary appendix is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b83 009 2 50 payment must accompany order

mineralogical characterization and transport pathways of dune sand using landsat tm data wahiba sand sea sultanate of oman sand samples and landsat imagery were used to characterize the spatial distribution of sand mineralogy and to evaluate potential sources and transport pathways of sediment in the wahiba sand sea in the sultanate of oman landsat tm data were useful in the geomorphic interpretation of a desert aeolian environment to distinguish the mineralogies found in the wahiba area and in extending the identification of sand mineralogy beyond the point specific grid produced from field sampling the wahiba sand sea has been previously divided into upper north and higher in elevation and lower south and lower in elevation portions based on dune morphology large scale spatial distributions of mineral composition follow a similar pattern to that of the geomorphic regions within the dune field field and landsat tm data suggests the upper wahiba is comprised of well mixed carbonate and quartz sand with some areas of significant mafic content surface sand in the eastern and western margins of the upper wahiba originate from the lower wahiba and from local wadis sand in the lower wahiba was likely derived from southern sabkhas and the coastal area and is quartz rich with isolated locations of carbonate rich sand we suggest that these carbonate rich patches in the lower wahiba were derived from reworked aeolianites lithofied sand dunes which underlie most of the sand sea and not directly from the coast as previously reported

seventeen years of the la clapiere landslide evolution analysed from ortho rectified aerial photographs we present a new method of digital elevation model dem calculation from aerial photographs and apply this method to the la clapiere landslide in the mercantour massif in eastern france the method uses new techniques of image correlation and of restitution of camera parameters the calculated dems are used to ortho rectify three aerial photographs acquired between 1983 and 1999 measurements made from these ortho rectified images show that the average velocity of the landslide was of 1 7 cm day with the rate of the headscarp retreat of 4 1 cm day and the toe of the landslide advancing at 1 7 cm day between 1983 and 1999 within the landslide the velocity field is are relatively homogeneous although their directions are locally heterogeneous scree slopes and scarps develop in an heterogeneous way within the landslide because the headscarp moves faster than the front of the landslide material spreads laterally at the scree slopes and or is eroded at the front of the landslide by the river and or is accumulated within the landslide on a low slope area located above a competent bar called igliere bar d 2002 elsevier science b v all rights reserved

shear wave velocity structure over the eastern indian subcontinent abstract fundamental mode surface wave generated by twelve earthquakes which occurred in northeastern india and nearby regions and were recorded at the shillong shl and chiengmai chg seismic stations are used to determine the shear wave velocity structure beneath these regions the frequency time analysis method is used to determine the group velocities for periods ranging from 4 to 50 s for fundamental mode rayleigh and love waves a high shear wave velocity 4 2 4 7 km s 1 is estimated in the lower 30 34 km of the crust crustal thickness is found to vary from 36 to 56 km with an overlying 2 4 km sedimentary thickness of shear wave velocity of 2 55 2 75 km s 1 the shear wave velocity in the upper 10 km of crust is 3 5 3 7 km s 1 below the sedimentary layer the inferred high shear velocity for the lower crust beneath these regions suggests an oceanic affinity and they are different from the indian shield structure the lower crust must have an oceanic origin as derived from the reminiscent of a certain oceanic lithosphere the available data do not permit us to estimate the upper mantle structure precisely however it shows a higher upper mantle shear velocity of 5 1 5 3 km s 1 this may be indicative of active tectonism beneath these regions in the uppermost mantle the moho boundary is not sharply defined here the increase in crustal thickness may be due to the collision of the indian and eurasian plates in the north and subduction of the indian plate beneath the burmese arc in the east

estimation of crustal qβ in the ganga basin using teleseismic broad band sh waveforms for the 1988 nepal india border earthquake abstract the average value of the intrinsic shear wave quality factor q has been estimated for the upper 55 km of the earth 47 km of crustal and upper 8 km of the upper mantle thickness in the border region between the ganga basin and himalaya in bihar we have used the teleseismic broad band sh and s sh waveforms of the 1988 nepal india border earthquake 6 4 m b for this purpose the frequency independent average value of q estimated in the range of 0 2 1 5 hz is found to be 1250 158

lithospheric mantle deformation beneath the indian cratons abstract the nature of deformation of the deep continental roots beneath the archean early proterozoic terrains opens the question whether these ancient terrains have had stable roots since the precambrian or whether recent plate motions have deformed them in view of this we make an attempt to study the thermal structure beneath the cratonic regions of the indian shield which vary in lithospheric thickness from 65 km in the singhbhum craton to 148 km in the archean dharwars the average depth of 104 km to the top of the underlying asthenosphere is consistent with other termination methods and is in fact less than half the 200 400 km depth found in other stable areas of the earth similarly the average reduced heat flow of about 35 mw m2 and moho temperature of about 550 c range 400 730 c for the indian cratons are also much higher than their counterparts elsewhere our study indicates a large scale deformation of the cratonic mantle lithosphere beneath the indian shield since the mesoproterozoic c

rayleigh wave attenuation and its variation across the atlantic ocean summary fundamental mode rayleigh walies generated by several earthquakes situated on great circle paths traversing pairs of seismograph stations in american and european coastal regions and on atlantic islands have been analysed to obtain anelastic attenuation coefficients group and phase velocities and specific quality factors at periods between 15 and 100s inversions of the dispersion and attenuation data have yielded shear velocity and shear wave internal friction qj models of the upper mantle for regions of varying age in the atlantic ocean the attenuation coefficients and internal friction values can be related to the age of the atlantic ocean floor older regions being characterized by lower internal friction or higher q values a lowq zone is prominent in the upper mantle of all regions less than 65 myr in age but is poorly developed in older regions in contrast to the attenuation results no systematic variations of rayleigh or shear velocities with age can be resolved using the dispersion data of this study a comparison of internal friction models beneath the atlantic with those beneath the pacific indicates that for regions of similar age internal friction is smaller or q larger beneath the atlantic than beneath the pacific especially in the younger regions immediately contiguous with the ridges in particular the upper mantle low velocity low q zone is less prominent beneath the atlantic the fact that spreading rates of the lithospheric plates are also smaller in the atlantic suggests that internal friction and the rate of long term creep in the mantle are closely related

crustal structure from deep seismic soundings along the koyna ii kelsi loni profile in the deccan trap area india abstract the crustal depth section obtained from deep seismic soundings along the koyna ii kelsi loni profile which lies near latitude 18 n roughly in the east west direction in that part of the deccan trap maharashtra state india shows a number of reflection segments below the deccan traps down to the moho discontinuity a deep fault below the deccan traps 13 km east of mahad divides the entire cross section including the moho boundary into two crustal blocks the reflection segments show updip towards the west coast in the western block the moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast reaching a depth of 31 5 km at the west coast the eastern block is thrown up by 1 5 km with respect to the western block along the deep fault a structural contour map of the moho discontinuity for the koyna reservoir area has been prepared from the present results and the crustal information obtained along the koyna i profile kaila et al 1979a shows that the deep fault in the koyna area is aligned in the nnw sse direction refraction seismic data analysis by the wave front method reveals that the thickness of the deccan trap increases towards the west coast the deccan trap is 600 700 m thick in the eastern region between nira sp 130 and loni sp 200 and attains a thickness of 1500 m at 10 km east of the west coast the longitudinal wave velocity in the deccan traps along the profile varies from 4 8 to 5 0 km sec and in the crystalline basement from 6 0 to 6 15 km sec a tentative isopach contour map of the deccan traps and a tentative structural contour map of the pre deccan trap contact have been prepared for the koyna reservoir area from the results along the koyna ii and koyna i profiles a flexure aligned in a nnw sse direction in the pre deccan trap contact which is an expression of the deep fault into the basement has been clearly brought out the flexure coincides in general with the orientation of the deccan volcanic scarp in this area

shear velocity structure of the crust and upper mantle beneath the tibetan plateau and southeastern china this paper addresses the velocity structure of the crust and upper mantle beneath southern china with special emphasis on the tibet region waveform data from 48 earthquakes as recorded on the wwssn and gdsn are used in this detailed forward modelling study constraints on the upper crustal section are derived from modelling local love waves in the time domain applying the mode sum modelling technique lower crustal constraints are derived by modelling the p nl wavetrain with the reflectivity method an average crustal thickness of 70 km is obtained beneath the tibetan plateau with a modest increase of velocity with depth the lithospheric and upper mantle structure is deduced from modelling s and ss triplication waveform data and relative traveltimes by applying a combination of wkbj and generalized ray methods s ss seismograms chosen with bounce points directly under tibet allow remote sensing of this inaccessible region the resulting model is an averaged 1 d model where corrections for lateral variation have been applied we conclude that the upper mantle structure in the entire region is basically shield like below 200 km sna however the velocity of the lithosphere is abnormally slow roughly 5 per cent beneath tibet the model for tibet derived does not have a distinct lid and has a positive velocity gradient in the crust suggesting crustal shortening a preliminary velocity model for southeastern china is also suggested

megaripples at wau an namus libya a new analog for similar features on mars abstract transverse aeolian ridges tars are curious aeolian megaripples on mars but there are few sites identified thus far to study as terrestrial analogs a new terrestrial analog site for tars has been found in and around an isolated volcano caldera in the sahara desert of libya the wau an namus volcano is potentially active and recognizable from space because of its strong albedo contrast wau an namus has large dark aeolian megaripple bedforms with the same horizontal length scales and overall planform patterns as observed for tars on mars some new patterns for these tar like features also have been found at wau an namus such as stripe like and clustered patterns which may shed new light on the formation of these features on both planets other aeolian features such as sand dunes and dust devil tracks are also evident in this region this is the first terrestrial analog site with dark megaripple features similar to some tars on mars the dark halo around wau an namus visible from space represents a unique site to study the formation and evolution of these mysterious features and thereby further our understanding of the probable recent history of the wind regime on mars

three dimensional physical modeling of deep seated landslides new technique and first results 1 a new technique for physical experimental modeling of landsliding and the first results are presented the technique is based on the use of new elasto brittle plastic analogue materials and an original vertical accelerator device enabling an increase in the gravity acceleration this technique allows slope stability to be addressed in a full three dimensional large strain formulation involving brittle and ductile rupture of the material three sets of experiments on the scale of a mountain 1 km high are presented the first one was designed to define the conditions and the mode of instability deformation in a homogeneous unfractured model instability occurs when the effective compressive strength c of the mountain is as small as 107 pa i e about 1 order of magnitude lower than the typical strength of small rock samples the deformation and rupture involve the whole mountain and correspond to well known deep seated gravitational slope deformation in the second set of experiments we introduced inherited tectonic faults which considerably reduce mountain stability with deformation again developing at the mountain scale the introduction of the local small scale fractures and weak zones in the last set of experiments resulted in smaller scale shallow landslides

vertical electric profile at choutuppal hyderabad in peninsular india abstract natural electromagnetic e m field data form choutuppal hyderabad in the frequency range 2 10 1 1 10 4 hz are processed and resistivities in the principal directions determined a 1 d inversion of the resulting yx curve reveals the existence of three conductive layers 1 depth to the top 16 km thickness 9 km resistivity 35 m 2 depth to the top 90 km thickness 15 km resistivity 15 m and 3 depth to the top 340 km thickness 10 km resistivity 3 m whereas the mid crustal conductor has been visualized as a low velocity layer corresponding to the conrad discontinuity the second conductor has been ascribed to the uplifted asthenosphere as a result of the thinning of the lithosphere and the third has been related to the global conductivity zone arising from olivine to spinel phase transition

anelasticity of the crust and upper mantle beneath north and central india from the inversion of observed love and rayleigh wave attenuation data the fundamental mode love and rayleigh waves generated by earthquakes occurring in kashmir nepal himalaya northeast india and burma and recorded at hyderabad new delhi and kodaikanal seismic stations are analysed love and rayleigh wave attenuation coefficients are obtained at time periods of 15 100 seconds using the spectral amplitude of these waves for 23 different paths along northern across burma to new delhi and central across kashmir nepal himalaya and northeast india to hyderabad and kodaikanal india love wave attenuation coefficients are found to vary from 0 0003 to 0 0022 km 1 for northern india and 0 00003 km 1 to 0 00016 km 1 for central india similarly rayleigh wave attenuation coefficients vary from 0 0002 km 1 to 0 0016 km 1 for northern india and 0 00001 km 1 to 0 0009 km 1 for central india backus and gilbert inversion theory is applied to these surface wave attenuation data to obtainq 1 models for the crust and uppermost mantle beneath northern and central india inversion of love and rayleigh wave attenuation data shows a highly attenuating zone centred at a depth of 20 80 km with lowq for northern india similarly inversion of love and rayleigh wave attenuation data shows a high attenuation zone below a depth of 100 km the inferred lowq value at mid crustal depth high attenuating zone in the model for northern india can be by underthrusting of the indian plate beneath the eurasian plate which has caused a low velocity zone at this shallow depth the gradual increase ofq 1 from shallow to deeper depth shows that the lithosphere asthenosphere boundary is not sharply defined beneath central india but rather it represents a gradual transformation which starts beneath the uppermost mantle the lithospheric thickness is 100 km beneath central india and below that the asthenosphere shows higher attenuation a factor of about two greater than that in the lithosphere the very lowq can be explained by changes in the chemical constitution taking place in the uppermost mantle

continental collision tectonics evidence from the himalaya and the neighbouring regions abstract the evolution of the himalaya and the tectonics of neighbouring regions are generally believed to be due to continent to continent collision of the eurasian and the indian plates during the last decade many new data have been obtained and examined and a suite of models has been developed to explain the evolution of the himalaya and the neighbouring regions these models could broadly be classified into three categories the subdivision of the himalaya into five main structural units is now well accepted a tectogenetic diagram of the himalaya is briefly discussed ophiolites are reported to occur all along the indus tsangpo suture zone results of geochemical analysis of an ophiolite sequence from dras in kashmir himalaya are presented surface wave dispersion and attenuation investigations have revealed the crustal and upper mantle structure below the himalaya and tibet plateau the finding of low velocity layers is consistent with the concept that horizontal compression has been responsible for creating these weak zones and the inferred elevated temperatures in the vicinity of the moho discontinuity below tibet earthquake focal mechanism solutions and interpretation of landsat imagery indicate that convergence of the indian plate with eurasia continues and is accommodated partly by crustal shortening and partly by lateral mass movement at the northwest and the northeast margins of the indian plate palaeomagnetic data from the himalaya belt and central asia can be interpreted in support of molnar and tapponnier s model of continental collision

shear velocity structure of the laterally heterogeneous crust and uppermost mantle beneath the indian region abstract the shear velocity structure of the indian lithosphere is mapped by inverting regionalized rayleigh wave group velocities in time periods of 15 60 s the regionalized maps are used to subdivide the indian plate into several geologic units and determine the variation of velocity with depth in each unit the hedgehog monte carlo technique is used to obtain the shear wave velocity structure for each geologic unit revealing distinct velocity variations in the lower crust and uppermost mantle the indian shield has a high velocity 4 4 4 6 km s upper mantle which however is slower than other shields in the world the central indian platform comprised of proterozoic basins and cratons is marked by a distinct low velocity 4 0 4 2 km s upper mantle lower crustal velocities in the indian lithosphere generally range between 3 8 and 4 0 km s with the oceanic segments and the sedimentary basins marked by marginally higher and lower velocities respectively a remarkable contrast is observed in upper mantle velocities between the northern and eastern convergence fronts of the indian plate the south bruma region along the eastern subduction front of the indian oceanic lithosphere shows significant velocity enhancement in the lower crust and upper mantle high velocities 4 8 km s are also observed in the upper mantle beneath the ninetyeast ridge in the northeastern indian ocean

anelasticity of the crust and upper mantle beneath the eurasian continent and the nearby regions from the inversion of love and rayleigh wave attenuation data summary the fundamental mode love and rayleigh waves generated by five earthquakes which occurred in central asia and were recorded at 20 35 wwssn stations throughout the world are analysed the love and rayleigh wave attenuations are determined at the time period of 10 120s for the continental and oceanic paths across eurasia and nearby regions using the spectral amplitudes of these waves the large standard deviation observed in the attenuation coefficients of surface waves may be due to the regional variation of the attenuative properties of the crust and upper mantle beneath eurasia the continental rayleigh wave attenuation coefficients are smaller by a factor of up to 2 compared to oceanic paths the continental rayleigh wave attenuation coefficient attains two minima of 0 1 5 x and 0 1 1 x 10 3km 1 at the time periods of 35 and 80 s respectively and two maxima of 0 58 and 0 3 x 10 3km at time periods of 10 and 100s respectively a similar trend is observed for the oceanic paths as well backus and gilbert inversion theory is applied to these love and rayleigh waves attenuation data to obtain qj models for the crust and upper mantle beneath eurasia and the nearby regions independent inversion of continental love and rayleigh waves attenuation data yields the thickness of the lithosphere to be 90 km for the oceanic paths the thickness of the lithosphere is estimated to be 110 km the base of the lithosphere is identified as the depth at which qf increases sharply qj in the asthenosphere is greater to a minimum of a factor of 2 as compared to the lithosphere

differential single frequency gps monitoring of the la valette landslide french alps abstract recently global positioning system gps surveying techniques have been increasingly employed to monitor landslide movement here we present an application of gps to monitor the la valette landslide located in the ubaye valley in the southern french alps this complex landslide is composed by an upper rotational part a central part with generally translational movement and a lower part which occasionally transforms into mud flows during intense rainfall events displacement rates average a few centimeters per month with velocity peaks of some centimeters per day during periods of strong activity gps data presented in this study were acquired with two single frequency gps receivers magellan connected to multipath resistant antennas the data were processed with the magellan software mstar nine points have been set in the studied area seven of them in the moving area one in a stable area near the landslide and one on the facing slope which is used as reference point for each observation one gps receiver is placed on the reference point for the whole day and the second one is placed on each monitored point for 1 h sessions the distance between the base and monitored point ranges from 480 to 1660 m eight survey campaigns were made between october 2000 and october 2002 to follow the evolution of the surface displacements the maximum cumulative 3 d displacement observed in the area was about 21 m during the period in the center part of the landslide corresponding to an average rate of movement of about 3 cm day the accuracy achieved during the gps measurements has been evaluated to be about 2 4 cm in e w direction about 11 cm in n s direction and about 7 4 cm in elevation in the worst case the gps results have been compared with traditional surveying techniques edm carried out on the same site by rtm service restauration des terrains en montagne the velocities obtained by the two methods are similar the advantage of the gps technique is the collection of data for the three spatial coordinates x y z of each point which allow to calculate the 3 d displacement vector these measurements have been combined with sar interferometric data in order to analyse the temporal evolution of the different landslide sectors

landslides as a geomorphological proxy for climate change a record from the dolomites northern italy abstract this study investigates the relationships between climate changes and hillslope evolution in the dolomites eastern alps italy during the late quaternary with particular attention paid to landslide processes the basic premise is that modifications in landslide frequency may be interpreted as changes in the hydrological conditions of slopes which are in turn controlled by climate after the statistical analysis of a data set composed of 73 conventional radiocarbon ages obtained from 24 landslides four periods of enhanced landsliding have been identified i from 10 700 to 8400 cal bp between younger dryas and the preboreal ii from 8200 to 6900 cal bp during the older atlantic iii from 5800 to 4500 cal bp between atlantic and subboreal and iv from 4000 to 2100 cal bp between subboreal and subatlantic these periods have been compared with different lateglacial and holocene paleoclimatic records to check the correspondence between periods of enhanced landslide activity and cold and humid spells recognized at different spatial scales as the records show in the study areas slope instability processes can be considered geomorphological indicators of climatic changes and to a certain extent reliable proxies of environmental evolution

seismic heterogeneities in the indian lithosphere abstract rayleigh wave group velocity distributions over the indian region were obtained by the backus gilbert method for time periods 15 25 40 50 and 60 s the observed velocity variations reveal sharp lithospheric heterogeneities in this region southern peninsular india is marked by high velocities in contrast to the northern indo gangetic plain and the himalaya highest surface wave velocities are observed over the southern part of the deccan traps and the dharwar craton whereas the metamorphic terrains and rift zones exhibit anomalous low velocities the nepal himalaya and indo burmese collision zones are characterised by contrasting velocities which reflect their diverse orogenesis the bay of bengal is marked by an anomalous 6 12 higher velocity as compared with the indian continental region for the periods 25 50 s

coda wave seismic structure beneath the indian ocean region and its implications to seismotectonics and structural heterogeneity abstract the indian ocean region is one of the challenging areas for seismological research because of its complex seismotectonic settings and intricate structural heterogeneity prevails beneath the indian ocean region in order to address the problem we attempted to determine the attenuation structure for the indian ocean region using coda wave generation by single backscattering model in this study the central frequency of interest has been considered between 1 5 and 12 0 hz with lapse time window ltw of 20 30 40 50 and 60 s measured from the origin time of the earthquake we obtained the attenuation relation for different seismotectonic zones associated with varying estimate of attenuation parameters spreading zone qc spz 171f1 10 subduction zone qc sz 220f0 961 triple point junction qc tpj 156f1 15 prominent faults of indian ocean region qc pfioz 197f0 99 and volcanic and hotspot qc vz hs 209f0 97 we estimated average frequency dependent attenuation parameters of q0 that varies as 156 32 q0 220 33 with corresponding variability in frequency parameter as 0 96 0 05 1 15 0 09 at 40 s ltw for the entire indian ocean region suggesting that the entire indian ocean is seismo tectonically highly active and is attributed to the nature and extent of attenuation due to varying amount of structural heterogeneity in different tectonic zones characterized by the occurrence of earthquakes of varying strengths in the seismically active tectonic zones of the region we found that the triple junction rtj is associated with low qc and high attenuation because of deposition of a variety of sediments at the rtj which is in unison to the geological mapping of the region we observed that our estimated attenuation model is comparable that of the aleutian islands the adak seismic zone at low frequency 5 hz and to the philippine sea subduction zone petukhin at higher frequency range 5 hz which is very much correlative to seismo tectonic settings we infer that our assimilated attenuation model has potential to provide information on intricate seismotectonics and seismogenesis for computing earthquake source parameters and earthquake hazards that may be useful for assimilating detailed seismic velocity structure beneath the indian ocean region

interactions between rock avalanches and glaciers in the mont blanc massif during the late holocene rock avalanches are common in the mont blanc massif which is bordered by valleys with large resident and tourist populations and important highways this paper combines historical data with detailed geomorphological mapping stratigraphic observation and absolute and relative dating to interpret several deposits resulting from rock avalanching onto glaciers nineteen rock falls and rock avalanches are described ranging in volume from 10 000 m3 to 10 106 m3 they occurred between 2500 bp and ad 2007 at six sites the events at three sites miage and drus glaciers and tour des grandes jorasses are characterised by short travel distances those at brenva triolet and frebouge glaciers exhibit excessive travel distances interactions between rock avalanches and glaciers are of four types i rock avalanche triggering where glacial and paraglacial controls include debuttressing of rockwalls due to glacier thinning and retreat oversteepening of rock slopes by glacial erosion and effects of glaciers on permafrost ii rock avalanche mobility in which mobility and travel distance are modified by channelling of rock avalanche debris by moraines and valleys incorporation of ice and snow often 50 for large events and irregularities on the glacier surface iii deposit sedimentology where melting of incorporated ice transforms the final deposit by reducing its thickness typically to 5 m and debris of variable thicknesses is juxtaposed in a hummocky deposit with chaotic piles of angular rock debris and iv glacier dynamics where insulating debris deposited upon a glacier produces a debris covered glacier of different dynamics and high elevated scars can favour the formation of small glaciers

landslide inventories for climate impacts research in the european alps landslides present a geomorphological hazard in alpine regions threatening life infrastructure and property here we present the development of a new regional landslide inventory ri for the european alps this database provides a substantial temporal and spatial picture of landsliding in the alps with particular focus on the swiss and french alps we use segmented models to evaluate recording bias in the temporal record we use scaling relationships to calculate landslide area based on a given volume for similar types of landslide with the result of this being that 9 5 of the landslides recorded in the ri now have area data recorded these landslide area data are then used to examine the log linear trend which exists between landslide area and frequency in inventories we show that this relationship is present for this historical dataset however none of the individual databases nor a unification of these contain a complete record with the small and larger landslides being recorded more consistently the use of segmented models on the temporal distribution of landslides in the ri shows that the post 1970 portion of the database is more reliable highlighted through an improved power law relationship although the frequency of medium sized landslides is still underestimated we show that creating a unified database ri can increase the reliability of datasets and consistency in recording for the use by researchers for attribution and detection studies

permafrost thaw and destabilization of alpine rock walls in the hot summer of 2003 1 exceptional rockfall occurred throughout the alps during the unusually hot summer of 2003 it is likely related to the fast thermal reaction of the subsurface of steep rock slopes and a corresponding destabilization of ice filled discontinuities this suggests that rockfall may be a direct and unexpectedly fast impact of climate change based upon our measurements in alpine rock faces we present model simulations illustrating the distribution and degradation of permafrost where the summer of 2003 has resulted in extreme thaw we argue that hotter summers predicted by climate models for the coming decades will result in reduced stability of many alpine rock walls

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

electrical structure across the indus tsangpo suture and shyok suture zones in nw himalaya using magnetotelluric studies 1 magnetotelluric studies in the nw himalayan region have shown anomalously high conductance of about 20 000 siemens in the crust beneath the indus tsangpo suture its and the adjoining tso morari dome in the depth range of 1 20 km high heat flow and high attenuation of the seismic waves in the himalayan crust together with the observed high conductance indicate presence of wide spread partial melt generated from the subducted indian crust the ladakh batholith appears as a resistive block to the north of its a moderately conductive zone demarcates the ladakh batholith from karakoram batholith to the north the similarity in the resistive structure with the results reported from the tibetan region by wei et al 2001 about 1500 km to the east is rather significant indicative of a two dimensional nature of the himalayan collision belt at least to the first order

application of geophysical methods for the investigation of the large gravitational mass movement of sechilienne france several geophysical techniques electromagnetic profiling electrical tomography seismic refraction tomogra phy and spontaneous potential and seismic noise measurement were applied in the investigation of the large gravita tional mass movement of sechilienne france the aim of this study was to test the ability of these methods to characterize and delineate the rock mass affected by this complex movement in mica schists whose lateral and vertical limits are still uncertain a major observation of this study is that all the zones strongly deformed previously and at present by the movement are characterized by high electrical resistivity values 3 k m in contrast to the undis turbed mass which exhibits resistivity values between a few hundred and 1 k m as shown by the surface observa tions and the seismic results this resistivity increase is due to a high degree of fracturing associated with the creation of air filled voids inside the mass other geophysical techniques were tested along a horizontal transect through the movement and an outstanding coherency appeared between the geophysical anomalies and the displacement rate curve these preliminary results illustrate the benefits of combined geophysical techniques for characterizing the rock mass in volved in the movement results also suggest that monitoring the evolution of the rock mass movement with time lapse geophysical surveys could be beneficial resume plusieurs techniques geophysiques profil electromagnetique tomographie electrique tomographie sismique et potentiel spontane et bruit de fond sismique ont ete appliquees pour la reconnaissance du grand mouvement de ter rain de sechilienne france situe dans des micaschistes l objectif de cette etude etait de tester ces methodes geophy siques afin de caracteriser et de delimiter la masse de roche affectee par ce mouvement complexe dont la limite laterale reste incertaine l etude a montre que toutes les zones tres deformees encore actuellement et dans le passe par le mouvement sont caracterisees par de fortes valeurs de resistivite electrique superieur ea3k m tandis que dans la zone non perturbee les valeurs de resistivite sont de quelques centaines de m a1k m comme le montrent les observations de surface et les profils de tomographie sismique cette augmentation de resistivite est due a une frac turation importante associee a la creation de vides remplis d air au sein du massif les techniques electromagnetiques ps et de mesure de bruit ont ete testees le long d un profil transversal recoupant le mouvement une correlation remar quable est obtenue entre les anomalies geophysiques et le taux de deplacement ces resultats preliminaires soulignent l interet de combiner les methodes geophysiques pour caracteriser la masse de roche impliquee dans le mouvement et pour determiner l evolution du mouvement par un suivi temporel des parametres geophysiques mots cles mouvement gravitaire methodes geophysiques sechilienne meric et al 1115

continent like crustal thickness beneath the bay of bengal sediments observed dispersion of fundamental mode rayleigh and love waves across the bay of bengal to wwssn and indian seismograph stations suggests increasing crustal thickness northward from an approximate 15 km thick oceanic crust south of the latitude of the southern tip of india to a more continent like thickness of approximately 25 km at 20 n and over 35 km at the northernmost part of the bengal fan the dispersion data are not consistent with models which simply add the increasing sedimentary thickness on top of a normal oceanic crust the sediment thicknesses and crust velocities are controlled by extensive seismic refraction results and are in agreement with clearly observed sedimentary higher mode waves recorded at the indian seismograph stations madras and vishakapatnam several hypotheses might explain this surprising result 1 1 the blanketing effect of the sediments with consequent temperature rise has brought about differentiation of basalt to increase the crustal thickness r n singh personal communication 2 2 the change in moho depth represents dynamic isostatic adjustment such as a phase change boundary which is lowered because of temperature or pressure perturbations from the sedimentary blanket or from pressure perturbations of plate collision 3 3 the collision has underthrust a wedge of low velocity material beneath the oceanic crust 4 4 the northern bay of bengal is actually fortuitiously continental or continent like possibly as a result of the influence of the 90 ridge especially in the northern part if the explanation is 1 2 or 3 the result is important to our understanding of crust and upper mantle dynamics it is suggested that further controlled studies be performed to verify the result

crust and upper mantle velocity structure beneath north and central india from the phase and group velocity of rayleigh and love waves abstract crust and upper mantle velocity structure is determined using the fundamental mode rayleigh and love waves for 23 different paths across north and central india the earthquakes occurring in kashmir nepal himalaya burma and nearby regions and recorded at hyderabad new delhi and kodaikanal seismic stations are used for dispersion studies frequency time analysis ftan using the multiple filter technique is done for the fundamental mode surface waves to estimate group velocities from the time periods of 13 71 s the single station technique is used to estimate rayleigh and love wave phase velocities at time periods of 15 75 s velocity structure down to a depth of 120 km is determined using both rayleigh and love wave phase and group velocities the crustal thickness is found to be 50 km with 4 km sedimentary thickness for the northern india across burma to new delhi path and 44 km for the central india across kashmir nepal himalaya and northeast india to hyderabad and kodaikanal path a low velocity zone v p 8 4 km s v s 4 15 km s is found from 100 km below the surface velocity structure shows that the shield structure of the peninsula extends up to northernmost india below sub himalayan regions with an overlying sedimentary thickness of 4 km the lower value of observed group velocity and higher phase velocity across northern and central india may be caused by the presence of varying sedimentary thickness in the northernmost part of india the indo gangetic plain below the sub himalayan region the observed lower value of rayleigh wave group velocities below 40 s time periods can be explained by assuming a thin layer of a high contrast material with a p wave velocity of 4 6 km s an s wave velocity of 2 5 km s a density of 3 24 g cm3 and a thickness of 3 km centred above the moho

landslide erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

landslide databases for climate change detection and attribution abstract a systematic inventory of landslide events over regional spatial scales and through time is required for investigating changes in landslide frequency along side changes in landslide triggers this paper describes the methods used to compile a european wide landslide inventory and some of the methodological and practical obstacles that inhibit better use and development of such inventories we argue that these methods can be used more widely to provide a comprehensive picture of landslide populations and to further enrich our understanding of the impact of climate change and other drivers on landslide frequency and magnitude

dune whitening and inter dune freshwater ponds in ne brazil the changes in color of sand dunes from white to yellow or red is often interpreted to signify their age or their source materials in this study we demonstrate the effect seasonal inter dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create by combining spectral measurements of field samples of dune sand together with the analysis of satellite images covering three dune fields in ne brazil lencois maranhenses jericoacoara and canoa quebrada we demonstrate its existence in the field in areas where ponds cover 41 of the dune field as in lencois maranhenses an almost total bleaching in the color of the sand occurs after which the dunes remain white with no relation to distance from the coastline in areas with less ponds e g jericoacoara or canoa quebrada dune whitening is less active and there are areas where dune rubification occurs as this process may have occurred in other dune fields during past climate conditions that may have been different from current ones interpretations of dunes age based on their color should be handled with care

power law correlations of landslide areas in central italy abstract we have studied the frequency area statistics of landslides in central italy we consider two data sets data set a contains 16 809 landslide areas in the umbria marche area of central italy they represent a reconnaissance inventory of very old old and recent modern landslides the noncumulative frequency area distribution of these landslides correlates well with a power law relation exponent 2 5 over the range 0 03 km 2 a l 2 data set b contains 4233 landslides that were triggered by a sudden change in temperature on 1 january 1997 resulting in extensive melting of snow cover an inventory of these snow melt triggered landslides was obtained from aerial photographs taken 3 months after the event these landslides also correlate well with a power law relation with exponent 2 5 over the range 0 001 km 2 a l 2 we show that the correlation of data set b is essentially identical to the correlation of 11 000 landslides triggered by the 17 january 1994 northridge california earthquake we attribute a rollover for small landslides in data set a to incompleteness of the record due to erosion and other processes and to limitations in the reconnaissance mapping technique used to complete the inventory on the other hand we conclude that rollovers for small landslides in data set b and the california earthquake data are real and are associated with the surface morphology we conclude that the power law distribution is valid over a wide range of landslide areas and discuss possible reasons we also discuss the contribution of the snow melt and earthquake triggered landslide events to the total landslide inventory

structural trends in the cuddapah basin from deep seismic soundings dss and their tectonic implications abstract structural trends in the upper proterozoic cuddapah basin at the basement level and at the moho level have been discussed based on deep seismic sounding dss studies results of dss studies along the alampur koniki profile profile 2 of fig 1 crossing the northern part of the cuddapah basin have been discussed in detail these results combined with the results of the kavali paranpalle section of the kavali udipi dss profile profile 1 of fig 1 kaila et al 1979 crossing the basin on its southern flank along with geological data and earthquake epicentral locations are used to explain the structural trends of the area it has been shown that the cuddapah basin was first created in its western part by downfaulting of the crustal block between faults 7 and 14 towards the west and fault 6 in the east fig 1 subsequently the eastern part was downfaulted against fault 6 before the commencement of upper cuddapah sedimentation further downfaulting towards the north along fault 5 created the srisailam block minor scale downfaulting between faults 7 and 13 in the west and fault 6 in the east and fault 8 in the north gave rise to the kurnool sub basin at a later stage similar downfaulting east of fault 9 and north of fault 5 gave rise to the palnad sub basin both these sub basins received kurnool sediments after the close of kurnool sedimentation the blocks between faults 4 and 6 along profile ii and between 11 and 6 along profile i were uplifted at the basement level thus giving rise to the nallamalai hills and iswarakuppam dome fig 1 the low angle thrust fault 3 on the eastern margin of the cuddapah basin might be a post cuddapah phenomenon the low angle thrust fault 2 probably occurred in the post dharwar period faults 1 17 and 10 near the east coast of india seem to be comparatively younger probably of mesozoic time along which the coastal block is downfaulted giving rise to the sedimentary basins

strain deformation in the northern indian ocean abstract seismicity focal mechanisms and moment tensors are used to estimate the strain deformation for earthquakes which occurred during the last 80 yrs in the northern indian ocean up to 38 s the shear strain deformation values are 0 47 10 8 near the owen s fracture zone 0 26 10 8 in the north carlsberg ridge 0 51 10 8 in the south carlsberg ridge 4 92 10 8 in the chagos laccadive ridge 0 21 10 8 in the rodriguez fracture zone 0 9 10 8 in the southwest mid indian ocean ridge 0 16 10 8 in the southeast mid indian ocean ridge 0 15 10 8 in the ninety east ridge and 2 11 10 8 in the sunda arc the high shear strain obtained in the area 6 s 10 s and 65 e 72 e suggests that the earthquakes here are characterized by high creep strength 20 kbars of material in the vicinity of the earthquake epicentral regions the slip rates obtained from the seismic moment are found to vary from 0 30 to 9 85 mm yr in different parts in the northern indian ocean the maximum slip rate is obtained for the chagos laccadive ridge moment tensor values obtained in different parts of the northern indian ocean suggest that the e w extension and the n s compression are predominant vertical compression crustal thinning is observed in the western areas whereas vertical extension crustal thickening occurs in eastern parts of the northern indian ocean the tension and compression strain deformation values estimated in different parts of the northern indian ocean support the hypothesis of ocean floor spreading and continental collision of the indian and eurasian plates the principal stress directions obtained from the moment tensor of earthquakes show that the compressive stress field is acting approximately in the alignment of the ridge and that the extensional stress is perpendicular to the ridge axis vertical compressions are more prominent near the owen s fracture zone in the chagos laccadive ridge and in the southwest mid indian ocean ridge whereas vertical extension is prominent in the sunda arc and the ninety east ridge

shear velocities qβ and the frequency dependence of qβ in stable and tectonically active regions from surface wave observations summary velocities and attenuation coefficient values of rayleigh waves within the south american continent and indian subcontinent have been determined in order to study velocity structure and qp structure as well as their lateral variation in those regions single station and two station data are combined to yield dispersion and attenuation data from periods of a few seconds to periods between 60 s and 100 s for each region both types of data are inverted using differential inversion schemes this inversion process is found to sometimes allow the location of velocity discontinuities in the models directly from the dispersion data qp models obtained from the inversion process are not constrained to have high values at large depths a problem with earlier methods used to invert surface wave attenuation data the shear velocity models for the indian shield and eastern south america are similar to one another and have somewhat slower velocities than those reported for shield regions of north america the shear velocity models for the himalaya and andes are similar to one another in crustal thickness but the velocities in the andes are lower than those in the himalayas in the uppermost mantle a low velocity zone can marginally be resolved in the upper mantle beneath the himalaya but not beneath the other regions in this study qp models obtained for the stable regions of eastern north america and eastern south america exhibit similar qp values at mantle depths the indian shield however has much lower qp values in both the crust and upper mantle a result which may be related to the unusually high heat flow observed for that stable region for the tectonically active regions of western north america western south america and the himalaya is considerably lower than qp for the stable regions throughout most of the crust and upper mantle minimum mantle values appear to be about 120 for stable regions and 40 or less for tectonically active regions thus qp values in the upper mantle appear to vary regionally by a factor of 3 or more whereas shear velocities in the same regions vary by no more than 13 per cent

summer temperature variations in the european alps a d 755 2004 abstract annually resolved summer temperatures for the european alps are described the reconstruction covers the a d 755 2004 period and is based on 180 recent and historic larch larix decidua mill density series the regional curve standardization method was applied to preserve interannual to multicentennial variations in this high elevation proxy dataset instrumental measurements from high low elevation grid boxes back to 1818 1760 reveal strongest growth response to current year june september mean temperatures the reconstruction correlates at 0 7 with high elevation temperatures back to 1818 with a greater signal in the higher frequency domain r 0 8 low elevation instrumental data back to 1760 agree with the reconstruction s interannual variation although a decoupling between warmer instrumental and cooler proxy data before 1840 is noted this offset is larger than during any period of overlap with more recent high elevation instrumental data even though the proxy time series

evidence of a changing size frequency distribution of landslides in the kyrgyz tien shan central asia there is a strong possibility that environmental change whether climate or land use will be manifest as changes in the size frequency distribution of landslides here evidence is presented for this from western kyrgyzstan central asia remote sensing and spatial analysis have been applied to map mass movements in the central part of the maily say valley and to detect recent landslide activations the evolution of landslide activity over the past 50 years has been analysed on the basis of pre existing landslide maps and new analyses of aerial photographs as well as quickbird images five inventories were produced for the years 1962 based on the existing map of 1962 and aerial photographs of 1962 1984 based on the existing map of 1977 and aerial photographs of 1984 1996 based on aerial photographs of 1996 2002 based on the existing map of 2003 and quickbird imagery of 2002 and 2007 based on quickbird imagery of 2007 the geomorphologic features contained in the catalogues represent the landslide bodies observed from remote imagery of the corresponding year mapped landslides are generally considered as the result of a series of slope failure events size frequency analyses applied to the five landslide inventories show that both the number and size of unstable slopes increased from 1962 162 objects to 2007 208 objects and the power law exponent decreased over time this changing power law exponent may indicate that landslide related hazards are increasing this tendency is documented in more detail for two active landslide zones one in the main valley and one located to the west of it landslide detection methods were used to assist the evolution of slope instabilities choosing appropriate thresholds the image subtraction method based on normalized difference vegetation index ndvi allowed accurate detection of new sliding activation in these two zones this confirmed the results of the more extensive survey that there is a systematic shift in power law exponents and size frequency distributions for central asian landslides copyright 2011 john wiley sons ltd

crustal q structure in the united states from multi mode surface waves determination of q structures are made using a new method which matches observed surface wave spectra with theoretical spectra computed for earthquakes with known fault plane solutions the importance of the method lies in its ability to utilize relatively short paths between a single source and receiver both of which are preferably located within a single geological province the method has been applied to study the regions of the eastern united states the colorado plateau and the basin and range province q models have been obtained through trial and error procedures and with an inversion scheme developed for that purpose models for each region obtained from these two procedures are in good agreement q values in the upper crust as obtained from inversions are 275 for the eastern united states 160 for the colorado plateau and 85 for the basin and range province q values in the lower crust although not well determined must be much higher than upper crustal values in all three regions the conclusions are consistent with those of previous work in which q values in the upper crust of a broad region of the western united states are lower than those of the eastern united states these new results show that substantial variations of q occur in different regions of the western united states the upper crustal q values show an inverse relationship to heat flow values

q structure beneath the north and central indian ocean from the inversion of observed love and rayleigh wave attenuation data abstract the fundamental mode love and rayleigh waves generated by 57 earthquakes which occurred in the north and central indian ocean extending to 40 s and recorded at indian seismograph and other wwssn stations such as how shl vis mdr hyb kod chg trd poo bom goa ndi nil and que are analysed love and rayleigh wave attenuation coefficients are estimated at periods of 15 100 s using the spectral amplitude of these waves for 98 different paths across the bay of bengal fan the arabian fan and the north and central indian ocean the large standard deviations observed in the surface wave attenuation coefficients may be a result of regional variation of the attenuative properties of the crust and upper mantle beneath these regions love wave attenuation coefficients are found to vary from 0 000 03 to 0 000 45 km 1 for the bay of bengal fan from 0 000 03 to 0 000 85 km 1 for the arabian fan and from 0 000 03 to 0 000 35 km 1 for the north and central indian ocean similarly rayleigh wave attenuation coefficients vary from 0 000 03 to 0 0004 km 1 for the bay of bengal fan from 0 000 06 to 0 0007 km 1 for the arabian fan and from 0 000 03 to 0 0007 km 1 for the north and central indian ocean backus and gilbert inversion theory is applied to these surface wave attenuation data to obtain average q 1 models for the crust and upper mantle beneath the bay of bengal the arabian fan and the north and central indian ocean inversion of love and rayleigh wave attenuation data shows a high attenuation zone centred at a depth of 120 km q 125 for the bay of bengal fan similarly a high attenuation zone q 40 70 occurs at a depth of 60 160 km for the arabian fan at 100 160 km q 115 for the indian ocean off ninetyeast ridge and at 80 160 km q 80 for the indian ocean across the ninetyeast ridge the q 1 models show a lithosphere thickness of 120 km beneath the bay of bengal fan similarly lithosphere thickness of 70 100 and 80 km is estimated beneath the arabian fan and the indian ocean off ninetyeast ridge and across ninetyeast ridge respectively the base of the lithosphere is identified as the depth at which there is a significant increase in the q 1 value which attains its maximum value in the asthenosphere the thinning of indian lithosphere beneath the arabian fan suggests high temperature below moho depth 60 km from surface which has caused a high attenuation zone at this shallow depth

transitional continental oceanic structure beneath the norwegian sea from inversion of surface wave group velocity data summary we have analysed the fundamental mode of love and rayleigh waves generated by 12 earthquakes located in the mid atlantic ridge and jan mayen fracture zone using the multiple filter analysis technique we isolated the rayleigh and love wave group velocities for periods between 10 and 50 s the surface wave propagation paths were divided into five groups and average group velocities calculated for each group the average group velocities were inverted and produced shear wave velocity models that correspond to a quasi continental oceanic structure in the greenland norwegian sea region although resolution is poor at shallow depth we obtained crustal thickness values of about 18 km in the norwegian sea area and 9 km in the region between svalbard and iceland the abnormally thick crust in the norwegian sea area is ascribed to magmatic underplating and the thermal blanketing evect of sedimentary layers maximum crustal shear velocities vary between 3 5 and 3 9 km s 1 for most paths an average lithospheric thickness of 60 km was observed which is lower than expected for oceanic type structure of similar age we also observed low shear wave velocities in the lower crust and upper mantle we suggest that high heat flow extending to depths of about 30 km beneath the surface can account for the thin lithosphere and observed low velocities anisotropy coeycients of 1 5 per cent in the shallow layers and 7 per cent in the upper mantle point to the existence of polarization anisotropy in the region

field evidence for surface wave induced instability of sand dunes barchans are crescent shaped dunes that move faster over desert surfaces than most other dune types a three year field study shows how they do it collisions and changes in wind direction destabilize the dunes generating surface waves that form new smaller barchans this prevents the formation of a single giant dune so plays a fundamental role in the development of dune patterns field studies of barchans crescent shaped dunes that propagate over solid ground under conditions of unidirectional wind1 have long focused on the investigation of an equilibrium between sand transport by wind and the control of air flow by dune topography2 3 4 which are thought to control dune morphology and kinematics5 6 7 because of the long timescale involved however the underlying dynamic processes responsible for the evolution of dune fields remain poorly understood8 here we combine data from a three year field study in the moroccan sahara with a model study to show that barchans are fundamentally unstable and do not necessarily behave like stable solitary waves as suggested previously9 10 11 12 we find that dune collisions and changes in wind direction destabilize the dunes and generate surface waves on the barchans because the resulting surface waves propagate at a higher speed than the dunes themselves they can produce a series of new barchans of elementary size by breaking the horns of large dunes the creation of these new dunes provides a mechanism for sand loss that prevents dune fields from merging into a single giant dune and therefore plays a fundamental role in the control of size selection and the development of dune patterns

mean sediment residence time in barchan dunes when a barchan dune migrates the sediment trapped on its lee side is later mobilized when exposed on the stoss side then sand grains may undergo many dune turnover cycles before their ejection along the horns but the amount of time a sand grain contributes to the dune morphodynamics remains unknown to estimate such a residence time we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3 d cellular automaton dune model the overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape the net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope the combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans then for different flow strengths and dune sizes we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux we infer that this central slice contains most of the relevant information about barchan morphodynamics finally we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique