geomorphological evidence of holocene climatic change from northwest ellesmere island canadian high arctic proxy data from the northern coast of ellesmere island are used to reconstruct holocene palaeoclimate and appear to corroborate the ice core record from the canadian and greenland high arctic despite some regional variation geomorphological evidence indicates that deglaciation was associated with a marked climatic amelioration in the late pleistocene early holocene 10 ka bp this contrasts with glaciers on the south side of grant land mountains which started to retreat at 7 5 ka bp perhaps due to significant differences in glacioclimatic regime and the influence of the arctic ocean indicators of sea ice conditions on northern ellesmere island suggest that the early holocene was a period of considerable open water radiocarbon dates on driftwood collected from behind the north coast ice shelves suggest that the ice shelves formed during a mid holocene climatic deterioration geomorphic evidence shows that the ice shelves are presently breaking up and melting in response to recent warming glaciers hav

constraints on the preservation of diamict facies melt out tills at the margins of stagnant glaciers abstract this paper reviews the formation and preservation of diamict facies melt out till generated in situ by the downwasting of stagnant ice at the margins of continental glaciers melt out tills are commonly envisaged as being the product of the top supraglacial or bottom subglacial melt of stagnant debris rich glacier ice but such deposits are relatively uncommon in modern glacier environments where they are thin laterally discontinuous and have a low preservation potential theoretical considerations of the distribution of englacial debris in continental ice sheets show that only the glacier margin is likely to contain the necessary volumes of englacial debris for melt out to be a significant diamict forming process however the application of thaw consolidation theory to the formation of such deposits shows that substantial porewater pressures and self sediment deformations can be induced during melt out especially in matrix rich debris the classic melt out mechanism widely invoked in the literature since 1875 and involving passive in situ aggregation from thawing englacial debris can be seen to operate under restricted conditions diamict facies produced by melt out are likely to form spatially disjunct and laterally discontinuous elements within complex and ice marginal stratigraphics the melt out process is not a mechanism whereby regionally extensive diamiet ite units can be deposited across glaciated basins

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

seismic site classifications for the st louis urban area abstract regional national earthquake hazards reduction program nehrp soil class maps have become important input parameters for seismic site characterization and hazard studies the broad range of shallow shear wave velocity v s 30 the average shear wave velocity in the upper 30 m measurements in the st louis area results in significant uncertainties between the actual spot values and the averaged values used to assign nehrp soil classes for regional seismic hazard studies in the preparation of an nehrp site classification map of the st louis urban area we analyzed 92 shear wave velocity v s measurements supplemented by 1400 standard penetration test spt profiles in areas bereft of v s measurements spt blow counts correlated to v s values based on the published correlations the data were then compiled for respective surficial geologic units and bedrock type these data suggest that the reciprocal of v s 30 exhibits a fairly linear relationship with depth to bedrock likely because v s 30 is a function of the thickness of surficial materials exhibiting relatively low v s values the v s 30 values were interpolated by summing the regressed v s 30 on the depth to bedrock and kriged values of the regression residuals the resulting nehrp site classification maps predict that upland areas of the st louis area are spatially classified as soil site classes s b to s d while the low lying floodplains are consistently classified as s d to s f

structural variation within the himalayan fold and thrust belt a case study from the kohat potwar fold thrust belt of pakistan abstract the kohat and potwar fold thrust belts kp ftb in pakistan exhibit structural variations over 250 km along strike within the himalayan fold and thrust system our 3d deformation model shows that kohat surface structures evolved above an active roof thrust in eocene evaporites the ramp forming duplexes in the kohat were stacked and passively transported toward the foreland above new ramps resulting in up to 5 km of thickening between the two decollements ramps from the kohat extend into the potwar as thrust tips of fault propagation folds the basement slope changes from flat 1 below the southern part corresponding to the change in structural style and complexity of the kp ftb the kalabagh fault zone linking the two belts is interpreted as a zone of complex dextral strike slip rotational faulting salt expulsed from the hanging walls of normal faults and under synclines in the kalabagh fault zone moved toward the footwall of normal faults accumulated in the cores of anticlines and formed lobe structures at the deformation front the fundamental reasons for the variable structural styles are changes in decollement strength basement slope preexisting normal faulting presence of a secondary decollement and spatially variable salt mobility and accumulation

development of the himalayan frontal thrust zone salt range pakistan the salt range is the active frontal thrust zone of the himalaya in pakistan seismic reflection data show that a 1 km offset of the basement acted as a buttress that caused the central salt range potwar plateau thrust sheet to ramp to the surface exposing mesozoic and paleozoic strata the frontal part of the thrust sheet was folded passively as it overrode the subthrust surface on a ductile layer of eocambrian salt lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer early to middle pliocene 4 5 ma conglomerate deposition in the southern potwar plateau previously interpreted in terms of compressional deformation may instead document uplift related to basement normal faulting stratigraphic evidence paleomagnetic dating of unconformities and sediment accumulation rates suggest that the thrust sheet began to override the basement offset from 2 1 to 1 6 ma cross section balancing demonstrates at least 20 to 23 km of shortening across the ramp the rate of himalayan convergence that can be attributed to underthrusting of indian basement beneath sediments in the pakistan foreland is therefore at least 9 14 mm yr about 20 35 of the total plate convergence rate

a next generation vs30 map for california based on geology and topography abstract correlations between geologic units and shear wave velocity form the basis of a series of maps developed over the past 15 years to estimate the time averaged shear wave velocity in the upper 30 m v s 30 the wills et al 2000 site condition map for california was found to correlate with seismic amplification field 2000 and was adopted as a standard depiction for many applications of seismic shaking estimates shakemap for example wills and clahan 2006 modified that map to show simplified geologic units and corresponding v s 30 values preparation of this map raised a number of questions on how best to distinguish units within younger alluvium wills and gutierrez 2011 found that a simple system based on surface slope could be used to subdivide the younger alluvium into three classes that have distinct v s 30 ranges the classes defined by slope have approximately the same variability in v s 30 as the previously defined classes but the total number of classes is reduced and the system can be easily applied to other tectonically active areas we have now applied the system of wills and gutierrez 2011 to create a new map of california using the most detailed available geologic maps use of more detailed geologic maps from 1 250 000 scale to 1 24 000 for much of california results in a much more detailed and accurate depiction of the surficial geology and we anticipate a more detailed and accurate depiction of seismic amplification due to the near surface materials online material site condition map of california at a scale of 1 1 500 000 as well as in arcgis formats

study of weak and strong ground motion including nonlinearity from the northridge california earthquake sequence abstract this article presents a new method to estimate s wave site response relative to a regional layered crustal model the method is useful for site specific strong motion prediction because the estimated site response functions are referenced to an idealized regional layered model for which we know the ground response exactly we applied this method to the northridge earthquake sequence we determined the site amplifications from aftershocks with magnitudes 2 6 to 4 3 at 21 stations that were colocated with strong motion stations these site response functions were then used to modify synthetic seismogram calculated for the northridge mainshock in the same regional layered crustal model and thus obtain site specific ground motion estimates these site specific synthetic seismograms have higher correlation to observations in comparison to the synthetic seismograms without weak motion site correction they have similar amplitude and frequency content to the observations especially at sites with recorded peak ground accelerations below 0 3 g at sites with larger ground motions however this approach overestimates the strong motion the differences are made clear when we estimate site response functions from the strong motion records and compare them with those from weak motion records we express the differences as the average ratio of the weak to strong motion site response aws ratio when the ground motion is low the aws ratio is near unity indicating that the weak and strong motion site responses agree with each other within the uncertainty however the aws ratio increases as the ground motion amplitude increses the difference in weak and strong motion site responses becomes significant at stations where peak acceleration was above 0 3 g peak velocity was above 20 cm sec or peak strain was above 0 06 during the mainshock this result demonstrates directly from the ground motion observations the relationship between nonlinear site response and peak ground motion parameters the nonlinearity is present on soft rock sites as well as on sediment sites

direct observation of basal sliding and deformation of basal drift at sub freezing temperatures in a tunnel at the base of sub polar urumqi glacier no 1 china three new mechanisms of glacier flow at sub freezing temperatures have been observed taken individually or in combination these modes of flow can account for nearly all 60 80 of the overall glacier motion and yet they act only within the lowermost 1 2 of the effective glacier thickness these mechanisms are 1 enhanced deformation of the frozen and ice laden subglacial drift 2 motion across discrete shear planes or shear bands within the frozen drift or at the ice drift interface and 3 basal sliding at an ice rock interface at a temperature of nearly 5 c the ice laden drift has an effective viscosity of more than one hundred times less than that measured in the overlying ice thus allowing very rapid shear deformation the observed rate or basal sliding at the ice rock interface agrees favorably with that predicted by the recent work of shreve 1984 if proper account is taken of the measured surface roughness and reduced ice viscosity

the sparta fault southern greece from segmentation and tectonic geomorphology to seismic hazard mapping and time dependent probabilities the sparta fault system is a major structure approximately 64 km long that bounds the eastern flank of the taygetos mountain front 2407 m and shapes the present day sparta basin it was activated in 464 b c devastating the city of sparta this fault is examined and described in terms of its geometry segmentation drainage pattern and post glacial throw emphasising how these parameters vary along strike qualitative analysis of long profile catchments shows a significant difference in longitudinal convexity between the central and both the south and north parts of the fault system leading to the conclusion of varying uplift rate along strike catchments are sensitive in differential uplift as it is observed by the calculated differences of the steepness index ksn between the outer ksn 83 and central parts 121 ksn 138 of the sparta fault along strike the fault system based on fault throw rates and the bedrock geology a seismic hazard map has been constructed that extracts a locality specific long term earthquake recurrence record based on this map the town of sparta would experience a destructive event similar to that in 464 b c approximately every 1792 458 years since no other major earthquake m 7 0 has been generated by this system since 464 b c a future event could be imminent as a result not only time independent but also time dependent probabilities which incorporate the concept of the seismic cycle have been calculated for the town of sparta showing a considerably higher time dependent probability of 3 0 1 5 over the next 30 years compared to the time independent probability of 1 66 half of the hanging wall area of the sparta fault can experience intensities ix but belongs to the lowest category of seismic risk of the national seismic building code on view of these relatively high calculated probabilities a reassessment of the building code might be necessary

lateral structural variation along the kalabagh fault zone nw himalayan foreland fold and thrust belt pakistan abstract the nw himalayan fold and thrust belt in pakistan is of gentler regional slope and wider extent than the other parts of the convergent plate boundary between india and the rest of asia large scale structural re entrants typify the main frontal thrust mft of the nw himalayan fold and thrust belt in pakistan understanding dynamics of the formation of these structural variations has been hampered by the lack of information about the lateral structures bounding the re entrants our mapping of the kalabagh fault zone a lateral ramp linking the salt and the surghar ranges advanced spaceborne thermal emission and reflection radiometer aster data field investigations and the interpreted reprocessed 2d seismic data this integration of surface and subsurface geology provides new insights on the geometry and evolution of the kalabagh fault zone by showing that it forms an oblique ramp to the main frontal thrust and at north a lateral ramp with right lateral strike slip movement our results indicate that the presence and areal extent of the evaporates is the dominant factor controlling lateral structural variation in the nw himalayan fold and thrust belt of pakistan the kalabagh fault zone acts as a zone that accommodates differential shortening and structural variation along the orogenic trend

influence of layering and boundary conditions on fault bend and fault propagation folding the influence of heterogeneous layering and boundary conditions on the structural development of fault bend and fault propagation folds has been investigated through petrographic study of nonscaled rock models the models are deformed in a triaxial rock deformation apparatus at room temperature and a 50 mpa confining pressure the models consist of a single layer of sandstone containing a saw cut ramp that is inclined 20 to the layering and an overlying intact thinly layered unit that is composed of limestone interlayered with lead or mica analysis of the fold thrust structures generated in sequentially shortened models with different loading conditions and layer types suggests that the mode of fold thrust interaction activated upon shortening will depend on fault zone drag bending and shearing resistance of the hanging wall shear strength of layer interfaces and loading conditions for the models these parameters may be expressed as a strength ratio describing the resistance to foreland translation relative to the resistance to internal deformation of the thrust system low strength ratios favor fault bend folding high strength ratios favor internal shortening of the sheet isotropic and thick relative to ramp height units above a propagating thrust tip will shorten primarily by faulting whereas thinly layered anisotropic units will shorten by fault propagation folding during both modes of fold thrust interaction the dips of the fold limbs increase interlimb angles decrease and imbricate faults form in the hanging wall or footwall with shortening in one model suite the imbrication is associated with a transition from fault bend folding to fault propagation folding and produces a highly asymmetric ramp anticline similar to a second mode fault bend fold or to a transported fault propagation fold the model data suggest that fault propagation folding in heterogeneously layered rock occurs by the discontinuous formation growth and linkage of faults below the growing fold amplification of the fault propagation fold is affected by the amount of slip transferred out of the deforming region imbrication and buckling the changes in the mode of fold thrust interaction and modifications in the local geometry and strain distribution that occur during shortening result from slip hardening on faults or from rotation or strain induced variations in the strength of the layers

glaciohydraulic supercooling a freeze on mechanism to create stratified debris rich basal ice ii theory simple theory supports field observations lawson and others 1998 that subglacial water flow out of overdeepenings can cause accretion of layered debris bearing ice to the bases of glaciers the large meltwater flux into a temperate glacier at the onset of summer melting can cause rapid water flow through expanded basal cavities or other flow paths if that flow ascends a sufficiently steep slope out of an overdeepening the water will supercool as the pressure melting point rises and basal ice accretion will occur diurnal occasional or annual fluctuations in water discharge will cause variations in accretion rate debris content of accreted ice or subsequent diagenesis producing layers under appropriate conditions net accretion of debris bearing basal ice will allow debris fluxes that are significant in the glacier sediment budget

topographic slope as a proxy for seismic site conditions and amplification we describe a technique to derive first order site condition maps directly from topographic data for calibration we use global 30 arc sec topographic data and v s 30 measurements here v s 30 refers to the average shear velocity down to 30 m aggregated from several studies in the u s as well as in taiwan italy and australia v s 30 values are correlated against topographic slope to develop two sets of parameters for deriving v s 30 one for active tectonic regions where topographic relief is high and one for stable shields where topography is more subdued by taking the gradient of the topography and choosing ranges of slope that maximize the correlation with shallow shear velocity observations we can recover to first order many of the spatially varying features of sitecondition maps developed for california our site condition map for the low relief mississippi embayment also predicts the bulk of the v s 30 observations in that region despite rather low slope ranges we find that maps derived from the slope of the topography is often well correlated with other independently derived regional scale site condition maps but the latter maps vary in quality and continuity and subsequently also in their ability to match observed v s 30 measurements contained therein alternatively the slope based method provides a simple approach to uniform site condition mapping

a terrain based site conditions map of california with implications for the contiguous united states abstract we present an approach based on geomorphometry to predict material properties and characterize site conditions using the v s 30 parameter time averaged shear wave velocity to a depth of 30 m our framework consists of an automated terrain classification scheme based on taxonomic criteria slope gradient local convexity and surface texture that systematically identifies 16 terrain types from 1 km spatial resolution 30 arcsec shuttle radar topography mission digital elevation models srtmdems using 853 v s 30 values from california we apply a simulation based statistical method to determine the mean v s 30 for each terrain type in california we then compare the v s 30 values with models based on individual proxies such as mapped surface geology and topographic slope and show that our systematic terrain based approach consistently performs better than semiempirical estimates based on individual proxies to further evaluate our model we apply our california based estimates to terrains of the contiguous united states comparisons of our estimates with 325 v s 30 measurements outside of california as well as estimates based on the topographic slope model indicate our method to be statistically robust and more accurate our approach thus provides an objective and robust method for extending estimates of v s 30 for regions where in situ measurements are sparse or not readily available

delineation of spatial variation of shear wave velocity with high frequency rayleigh waves in anchorage alaska high frequency rayleigh waves were generated in the frequency range of about 1 100 hz by an electromagnetic vibrator in co operation with the vibration instrument company japan and the ensol corporation north carolina at 36 sites in anchorage from phase delay times between two sensors the phase velocity of the fundamental mode at each site was computed these data were inverted in terms of shear wave velocity structure by a stochastic inversion scheme of the 36 sites values of shear wave velocity as a function of depth were available at seven sites from downhole measurements at these sites the comparison of the results obtained by others between surface and downhole measurements showed reasonable agreement these results were therefore combined with those of the remaining 29 sites obtained in this study the structure of the 36 sites could be subdivided into four groups on the basis of nehrp provision and from the time averaged structures for the uppermost 30 m corresponding to the four groups it has been possible to identify the lateral extent of soil classes c and d in the anchorage area from statistical analysis of the time averaged data it is shown that the lithology of the area in soil class c is distinct from that in d the same is true for the subunits namely glaciofluvial deposits in areas of c and d moreover the areas in soil class d along the knik arm in west anchorage with relatively low values coincide with the areas of high ground failure susceptibility identified by others from observations following the prince william sound earthquake mw 9 2 of 1964

site response in southern california for probabilistic seismic hazard analysis this study determines site response factors that can be applied as cor rections to a rock attenuation relationship for use in probabilistic seismic hazard analysis the site response factors are amplitude and site class dependent these amplification factors are determined by averaging ratios between observed and pre dicted ground motions for peak ground acceleration pga and for 5 damped re sponse spectral acceleration at 0 3 1 0 and 3 0 sec oscillator periods the observa tions come from the strong motion database of the southern california earthquake center scec and the predictions are based on the sadigh 1993 rock attenuation relation when separated and averaged according to surface geology significantly different site response factors are found for quaternary and mesozoic units but a subclassification of quaternary is generally not justified by the data the low input motion amplification factors are consistent with those obtained from independent aftershock studies at the pga and 0 3 second period an observed trend of decreasing quaternary site amplification with higher input motion is consistent with nonlinear soil behavior however the trend exists for mesozoic sites as well implying that this may be an artifact of the sadigh relationship there is a correlation between larger site response factors and lower average shear wave velocity in the upper 30 m for low predicted pga input motions with an increase in the correlation with increasing period the 0 3 sec site response factors for quaternary data in southern california determined in this study are consistent with 0 3 sec nehrp site response correction factors however at 1 0 sec period some inconsistencies remain a trend is also seen with respect to sediment basin depth where deeper sites have higher average site response factors these results constitute a customized attenuation relationship for southern california the implication of these customized attenuation models with respect to probabilistic hazard analysis is examined in field and petersen 2000

ground motion parameters in shillong and mikir plateau supplemented by mapping of amplification factors in guwahati city northeastern india abstract ground motion parameters for shillong mikir plateau of northeastern india are examined empirical relations are obtained for ground motions as a function of earthquake magnitude fault type source depth velocity characterization of medium and distance correlation between ground motion parameters and characteristics of seismogenic zones are established simultaneously new empirical relations are derived for attenuation of ground motion amplitudes correlation coefficients of the attenuation relations depend on the site classifications that are identified based on average shear wave velocity and site response factors the attenuation relation estimated for logarithmic width of mikir plateau found to be a little bit higher than that of shillong plateau both for soft and hard ground which accounts for geometrical spreading and anelastic attenuation simultaneously validation are made studying the seismic microzonation process related to geomorphological geological subsurface features for thickly populated guwahati city of india under threat from scenario earthquake

vs30 empirical prediction relationships based on a new soil profile database for the beijing plain area china earthquake ground motion prediction models usually define site conditions based on the time averaged shear wave velocity in the upper 30 m v s 30 proxy based estimations of v s 30 are commonly used if velocity measurements are not available we compile a soil profile database for the beijing plain area china using data from research documents and technical reports the database contains 479 soil profiles 463 of which have depths greater than 30 m we develop regional relationships for the beijing plain area for extrapolating the time averaged shear wave velocity to a given depth less than 30 m to v s 30 and then compare the performance of available models we find that the second order polynomial model boore et al 2011 based on data from japan provides an overprediction whereas the linear model boore 2004 calibrated on data from california underestimates v s 30 we develop relationships for estimating v s 30 based on proxies such as ground slope gradients from radar derived digital elevation models dems and surface geology at different scales we find that local v s 30 data in the beijing plain are generally lower than existing 30 arcsec gradient based global models regression results show a modest correlation between v s 30 and topographic ground slope for several dem resolutions 3 15 30 and 60 arcsec geology based proxies are more effective than ground slope for v s 30 estimation in the analyzed area we propose a bilinear model based on geologic ages and depositional environments for estimating v s 30 which shows a statistically significant trend for application in the beijing plain area online material figures showing topographic ground slopes and correlations of v s 30 with topographic slope from digital elevation model dem data and a table summarizing data from the 463 boreholes

three dimensional imaging of shear wave velocity in the uppermost 30 m of the soil column in anchorage alaska summary the main aim of this paper is to obtain an overall view of the shear wave velocity structure of the anchorage metropolitan area and to analyse in detail the extent of various soils types both laterally and vertically for this purpose a stochastic scheme has been used to invert the rayleigh wave phase velocity data to obtain 1 d shear wave velocity structure in the uppermost 0 30 m at 36 sites in the anchorage basin located in south central alaska on the basis of these 1 d velocity models we have applied an imaging technique aimed at volumetric modelling and data visualization based on an interpolation algorithm involving finite differences we present a 3 d representation of the s wave velocity structure of the anchorage area obtained through spatial prediction these velocity images are shown as horizontal slices at gradually increasing depths vertical cross sections at various latitudes and longitudes and 3 d blocks as defined by characteristic velocity ranges they enable us to understand in detail the different soil classes by their characteristic shear wave velocities the images are in good agreement with the available geological information about the area

site characterization using integrated imaging analysis methods on satellite data of the islamabad pakistan region we develop an integrated digital imaging analysis approach to produce a first approximation site characterization map for islamabad pakistan based on remote sensing data we apply both pixel based and object oriented digital imaging analysis methods to characterize detailed 1 50 000 geomorphology and geology from advanced spaceborne thermal emission and reflection radiometer aster satellite imagery we use stereo correlated relative digital elevation models rdems derived from aster data as well as spectra in the visible near infrared vnir to thermal infrared tir domains the resulting geomorphic units in the study area are classified as mountain including the margala hills and the khairi murat ridge piedmont and basin terrain units the local geologic units are classified as limestone in the margala hills and the khairi murat ridge and sandstone rock types for the piedmonts and basins shear wave velocities for these units are assigned in ranges based on established correlations in california these ranges include vs30 values to be greater than 500 m sec for mountain units 200 600 m sec for piedmont units and less than 300 m sec for basin units while the resulting map provides the basis for incorporating site response in an assessment of seismic hazard for islamabad it also demonstrates the potential use of remote sensing data for site characterization in regions where only limited conventional mapping has been done

site classification for earthquake hazard and risk assessment in australia while site response phenomena are well recognized globally the influence of regolith properties on ground motion has not previously been investigated for much of australia in an effort to characterize the regolith in terms of its ability to modify earthquake ground shaking this validation study assesses the national site classification map of australia which has been developed for application in first order earthquake hazard and risk assessment in the absence of regolith thickness and fundamental period data site classes are assigned based on a method developed in california that uses the relationship between geological material and the shear wave velocity of the upper 30 m v s 30 the classification scheme is then adjusted to suit the australian geological environment including a correction for the presence of weathered in situ regolith commonly encountered in this stable tectonic setting the results are validated using geophysical and geotechnical data from a variety of quaternary sedimentary environments in the newcastle sydney and perth urban areas and from bedrock dominated environments at a range of sites across australia the results of these analyses demonstrate the utility but also highlight the limitations of applying a depth limited shear wave velocity method in site classification for seismic hazard assessment

the structural glaciology of kongsvegen svalbard and its role in landform genesis mapping of the structural glaciology of kongsvegen svalbard reveals evidence for four main deformational structures these are stratification longitudinal foliation thrusts and crevasse traces these structures are considered in terms of their contribution to debris entrainment transport and subsequent landform development stratification is associated with small amounts of supraglacial debris that has been folded with flow parallel axes longitudinal foliation in places incorporates basal glacial sediments along folds with flow parallel axes and thrusts transport basal debris to the glacier surface crevasse traces are not significant in terms of debris entrainment the entrainment of basal debris along longitudinal foliation is not a universally recognised process at kongsvegen this process is attributed to the development of a transposition foliation in combination with incorporation of debris rich basal ice or soft basal sediment in the fold complex mapping of the landforms in the proglacial area shows that debris incorporated along longitudinal foliation is released as foliation parallel ridges and that transverse ridges mark debris bearing thrusts the role of longitudinal foliation in landform development has never been documented in this manner although the preservation potential of such ridges may be limited recognition of foliation parallel ridges in the pleistocene landform record has important implications for the interpretation of the dynamics of former ire masses

shear wave velocity model of the santiago de chile basin derived from ambient noise measurements a comparison of proxies for seismic site conditions and amplification summary we determined a high resolution 3 d s wave velocity model for a 26 km 12 km area in the northern part of the basin of santiago de chile to reach this goal we used microtremor recordings at 125 sites for deriving the horizontal to vertical h v spectral ratios that we inverted to retrieve local s wave velocity profiles in the inversion procedure we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements which were found to vary substantially over short distances in the investigated area the resulting model was derived by interpolation with a kriging technique between the single s wave velocity profiles and shows locally good agreement with the few existing velocity profile data but allows the entire area as well as deeper parts of the basin to be represented in greater detail the wealth of available data allowed us to check if any correlation between the s wave velocity in the uppermost 30 m v30s and the slope of topography a new technique recently proposed by wald and allen exists on a local scale we observed that while one lithology might provide a greater scatter in the velocity values for the investigated area almost no correlation between topographic gradient and calculated v30s exists whereas a better link is found between v30s and the local geology finally we compared the v30s distribution with the msk intensities for the 1985 valparaiso event pointing out that high intensities are found where the expected v30s values are low and over a thick sedimentary cover although this evidence cannot be generalized for all possible earthquakes it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the santiago basin

site characterization of the strong motion stations and evaluation of site effects in the ankara region during the december 2007 and march 2008 moderate bala earthquakes local site conditions may significantly affect the amplitude and frequency of ground motion during earthquakes recordings of recent major earthquakes have demonstrated that soil conditions can generate prominent amplification of ground shaking and can be compared with the amplification predicted by numerical simulation this study analyzes the ground motion data from the december 2007 and march 2008 moderate bala earthquake series considering the effect of soil conditions on ground shaking in the southern part of ankara the capital city of turkey initially shear wave velocity profiles of the strong ground motion stations were evaluated to define site classifications for each station in ankara and its surroundings strong motion data collected during the bala earthquake series mw range 5 6 4 8 were used to develop event specific attenuation relationships for peak ground acceleration and spectral acceleration at various periods and different site conditions site amplification factors were derived from the regression results from the event specific attenuation relationships for the bala earthquake series the implications of these ground motion amplification factors were also discussed and compared using the current seismic design codes finally the response spectra from the recording stations were used to determine site amplification factors for different site conditions to evaluate the variability of the site response in localized regions in ankara

major end moraines of younger dryas age on wollaston peninsula victoria island canadian arctic implications for paleoclimate and for formation of hummocky moraine some of the most extensive and massive end moraines of younger dryas age 11 10 14c ka bp yet recognized in north america occur on wollaston peninsula of victoria island on the western part of the peninsula numerous closely spaced end moraines formed in the interval starting 11 100 100 radiocarbon years ago and ending about 10 500 10 200 years ago net recession was generally slow throughout and was punctuated by moraine building and at least two readvances recession is mapped with a resolution that is approximately decadal the moraines form an orderly nested succession and are consistently associated with westward shedding of meltwater which formed a sequence of marine limit deltas we lack firm independent proxy climate evidence needed to assess whether these moraines formed because of cold younger dryas climate rather than because of controls such as topographic setting and water depth but climatic control seems probable the moraines evidently retain glacier ice cores as do most similarly

the scec phase iii strong motion database as part of the southern california earthquake center scec phase iii effort to include site effects in hazard models for southern california a regional database of strong motion observations was developed the observations consist of the peak ground acceleration pga and 5 damped response spectral acceleration sa at 0 3 1 0 and 3 0 sec periods from 28 earthquakes and 281 stations a total of 449 pairs of horizontal pga and sa observations that were taken from the scec strong motion database smdb are presented here the phase iii database includes earthquakes with moment magnitudes larger than 5 0 and stations in southern california with locations between 32 and 36 north latitude observations from buildings with more than two stories and dam abutments or crests are excluded from the database observations with distances of 150 km or greater were also excluded the agencies that provided the data to smdb are the u s geological survey california strong motion instrumentation program university of southern california and the los angeles department of water and power the database also contains site classification information for each station a first general classification is based on the 1 750 000 california map of quaternary tertiary and mesozoic geologic units by jennings 1977 as modified by park and elrick 1998 a second more detailed classification is based on quaternary mapping in the los angeles region by tinsley and fumal 1985 as modified by park and elrick 1998 a third classification is based on the correlation of surface geology with shear wave velocity in the upper 30 m wills et al 2000 an arbitrary depth to basement parameter is assigned to stations that are located within the boundary of the 3d velocity model used by olsen 2000 which is based on the scec 3d velocity model version 1 this parameter is defined as the depth to the 2 5km sec velocity isosurface special parameters associated with particular attenuation relations such as different distance measures a hanging wall flag and fault type flag are also assigned to each observation these data are all presented within the tables and figures of this article and also have been made available via a downloadable file on the internet http smdb crustal ucsb edu phase3

accounting for site effects in probabilistic seismic hazard analyses of southern california overview of the scec phase iii report this article presents an overview of the southern california earthquake center scec phase iii effort to determine the extent to which probabilistic seismic hazard analysis psha can be improved by accounting for site effects the contri butions made in this endeavor are represented in the various articles that compose this special issue of bssa given the somewhat arbitrary nature of the site effect distinction it must be care fully defined in any given context with respect to psha we define the site effect as the response relative to an attenuation relationship averaged over all damaging earthquakes in the region a diligent effort has been made to identify any attributes that predispose a site to greater or lower levels of shaking the most detailed maps of quaternary geology are not found to be helpful either they are overly detailed in terms of distinguishing different amplification factors or present southern california strong motion observations are inadequate to reveal their superiority a map based on the average shear wave velocity in the upper 30 m however is found to delineate significantly different amplification factors a correlation of amplification with basin depth is also found to be significant implying up to a factor of two difference between the shallowest and deepest parts of the los angeles basin in fact for peak accel eration the basin depth correction is more influential than the 30 m shear wave ve locity questions remain however as to whether basin depth is a proxy for some other site attribute in spite of these significant and important site effects the standard deviation of an attenuation relationship the prediction error is not significantly reduced by making such corrections that is given the influence of basin edge induced waves subsur face focusing and scattering in general any model that attempts to predict ground motion with only a few parameters will have a substantial intrinsic variability our best hope for reducing such uncertainties is via waveform modeling based on first principals of physics finally questions remain with respect to the overall reliability of attenuation re lationships at large magnitudes and short distances current discrepancies between viable models produce up to a factor of 3 difference among predicted 10 in 50 yr exceedance levels part of which results from the uncertain influence of sediment nonlinearity

support for the innuitian ice sheet in the canadian high arctic during the last glacial maximum the extent of glacier ice in the canadian high arctic during the last glacial maximum lgm has been debated for decades one school proposed a regional innuitian ice sheet whereas another proposed a smaller non contiguous franklin ice complex research throughout western nares strait supports coalescent innuitian and greenland ice during the lgm based on widespread glacial and marine deposits dated by 14c and amino acid analyses this coalescence likely promoted a vigorous regional ice flow westward across ellesmere island to eureka sound post glacial emergence in eureka sound suggests a former ice thickness at least as great as that in nares strait 1 km recently independent field studies elsewhere in the high arctic also support an innuitian ice sheet during the lgm collectively these studies resolve a long standing debate and initiate new opportunities concerning the reconstruction of high latitude palaeoenvironmental and palaeoclimatic change 1998 john wiley sons ltd

bannu basin fold and thrust belt of northern pakistan subsurface imaging and its implications for hydrocarbon exploration abstract the trans indus salt range located in northern pakistan is one of the most tectonically active fold and thrust belts and comprises three main regions the potwar salt range the kohat surghar range and the bannu basin khisor range of these the bannu basin is the least studied and only a handful of publically accessible datasets and publications are available recently made public 2d seismic profiles and well data from the bannu basin indicate the presence of salt as well as evidence for a main detachment surface which is neoproterozoic in age our findings suggest that the salt range formation could be the main detachment for the entire basin interpretation also shows a miocene eocene basin wide unconformity that marks the himalayan orogenic event which separates the pre himalayan from the syn himalayan sedimentary units on the basis of seismic reflection data we conclude that the basin experienced three main tectonic settings an early stage of pre himalayan passive tectonic environment is followed by the compressional himalayan tectonics which resulted in uplifted areas sourcing the fluviatile fill of the subsided basin during this time sedimentation from the northern margin of the basin may have influenced the southward flow of salt this is followed by a more recent stage of thrusting that produced folds and thrusts deforming all of the sedimentary units structural geometries suggest that prospective traps are developed mainly in the anticlines outlining the eastern and western boundaries of the bannu basin as well as the southern zone of the basin furthermore the presence of salt diapirism and transpression zones together with numerous oil seeps in and around the basin increase the probability of hydrocarbon accumulation and indicate great potential for future exploration

a site conditions map for california based on geology and shear wave velocity one simple way of accounting for site conditions in calculating seismic hazards is to use the shear wave velocity in the shallow subsurface to classify materials the average shear wave velocity to 30 m v 30s has been used to develop site categories that can be used for modifying a calculated ground motion to account for site conditions we have prepared a site category map of california by first classifying the geologic units shown on 1 250 000 scale geologic maps our classification of geologic units is based on v 30s measured in 556 profiles and geological similarities between units for which we have v s data and the vast majority of units for which we have no data we then digitized the geologic boundaries from those maps that separated units with different site classifications v s data for california shows that several widespread geologic units have ranges of v 30s values that cross the boundaries between nehrp ubc site categories the franciscan complex has v 30s values across ubc categories b and c with a mean value near the boundary between those two categories older alluvium and late tertiary bedrock have v 30s values that range from about 300 to about 450 m sec across the boundary between categories c and d to accommodate these units we have created intermediate categories which we informally call bc and cd geologic units that have or are interpreted to have v 30s values near the boundary of the ubc categories are placed in these intermediate units in testing our map against the available v 30s measurements we have found that 74 of the measured v 30s values fall within the range assigned to the v s category where they fall on the map this ratio is quite good considering the inherent problems in plotting site specific data on a regional map and the variability of physical properties in geologic units we have also calculated the mean and distribution of v 30s for each of our map units and prepared composite profiles showing the variation of v s in the upper 100 m from the available v s data these data show that the map categories that we have defined based on geologic units have different v s properties that can be taken into account in calculating seismic hazards

developing a map of geologically defined site condition categories for california consideration of site conditions is a vital step in analyzing and predicting earthquake ground motion the importance of amplification by soil conditions has long been recognized but though many seismic instrument sites have been characterized by their geologic conditions there has been no consistent simple classification applied to all sites as classification of sites by shear wave velocity has become more common the need to go back and provide a simple uniform classification for all stations has become apparent within the pacific earthquake engineering research center s next generation attenuation equation project developers of attenuation equations recognized the need to consider site conditions and asked that the california geological survey provide site conditions information for all stations that have recorded earthquake ground motion in california to provide these estimates we sorted the available shear wave velocity data by geologic unit generalized the geologic units and prepared a map so that we could use the extent of the map units to transfer the velocity characteristics from the sites where they were measured to sites on the same or similar materials this new map is different from the california geological survey preliminary site conditions map of california in that 19 geologically defined categories are used rather than national earthquake hazards reduction program categories although this map does not yet cover all of california when completed it may provide a basis for more precise consideration of site conditions in ground motion calculations

deglaciation of the younger dryas or loch lomond stadial ice field in the northern highlands scotland when viewed from the air scottish hummocky moraine can be resolved into a series of linear ridges that resemble those found at the margins of actively retreating glaciers today recent work has supported the interpretation of these linear ridges as ice marginal landforms and the authors believe that the majority of hummocky moraine deposits can be interpreted in this way consequently the pattern of deglaciation can be established fairly precisely from the pattern of linear ridges this approach is applied to the landforms of the northern part of the loch lomond stadial ice field in order to reconstruct the regional pattern of deglaciation this leads to important inferences about the significance of topographic control during deglaciation and more importantly it provides fresh insight into the environment of the british isles during the loch lomond stadial

late quaternary deformation of the salt range of pakistan in the salt range siwalik strata as young as 400 000 yr b p are strongly deformed and overlain with angular unconformity by fanglomerates that are themselves folded and thrust faulted the south flank of the salt range appears in map view as a series of scallops convex to the south produced by a thrust fault bringing the salt range south southeast over sediments of the jhelum river plain the western edge of the range is marked by right slip faults that cut the kalabagh conglomerate which itself rests upon siwaliks with angular unconformity the kalabagh conglomerate is folded and probably cut by diapirs from the salt range formation holocene alluvium appears to be undeformed and strike slip fault lineations are more subdued than those along the historically active chaman fault suggesting that the recurrence interval of faulting may be measured in thousands of years the low historic seismicity of the salt range may be due to such weak coupling between the salt range decollement and crystalline basement that fault displacement is not accompanied by great earthquakes in contrast to the indian foredeep of the himalaya

a transect of 200 shallow shear velocity profiles across the los angeles basin this study assesses a 60 km north northeast south southwest transect along the san gabriel river for shallow shear velocities in san gabriel valley and the los angeles basin of southern california we assessed a total of 214 sites 199 along the transect at 300 m spacing during a one week field campaign with the refraction microtremor remi technique the transect9s maximum 30 m shear velocity vs30 occurs in coarse alluvium of san gabriel valley where the san gabriel river exits the san gabriel mountains at 730 m sec upper national earthquake hazards reduction program nehrp site class c much of the northeast section of the transect in san gabriel valley is also nehrp class c or near the cd class boundary the section of the transect south from whittier narrows to seal beach shows nehrp d velocities in active alluvium the transect9s lowest vs30 230 m sec at the alamitos bay estuary is also classed as nehrp d an increase toward the nehrp cd class boundary occurs at the shoreline beach outside alamitos bay confirmed by additional measurements on seal beach our measured vs30 values generally show good correlation with published site classification maps and existing borehole data sets there is no evidence in our data for an increase in velocity predicted by wills et al 2000 at their cd to bc site classification boundary at the san gabriel mountains front nor for any decrease at their d to de class boundary at alamitos bay very large vs30 variations exist in soil and geologic units sampled by our survey the vs30 variations we measured are smaller than vs30 variations of 30 or more we found between closely spaced

hydrochemical signatures of deep groundwater circulation in a part of the himalayan foreland basin groundwater samples were analyzed from 71 springs and wells as part of a larger study in a region of compressional tectonic regime the study site covers the peshawar basin and surroundings in the himalayan foreland of pakistan the northern portion is mountainous and the water table is discontinuous in different intermontane valleys with abundant springs with normal and anomalous temperatures and composition the southern part is divided into isolated basins with a number of drilled deep and dug shallow wells hydrochemical signatures of elevated strontium sr sio2 boron b and the geothermometric signatures all indicate a deep circulation of the emerging groundwater moreover for several of the sample sites water chemical compositions measured spring and water well temperatures and reservoir temperatures calculated for spring waters all point to origin from deep horizons within the basin remarkable proximity of all the thermal and hydrochemical anomalies to major faults suggests that the waters ascended along these faults from greater depths the area is a natural western extension of the himalayan geothermal belt described in earlier literature for the eastern and central himalayas

simulation of broadband ground motion including nonlinear soil effects for a magnitude 6 5 earthquake on the seattle fault seattle washington the seattle fault poses a significant seismic hazard to the city of seattle washington a hybrid low frequency high frequency method is used to calculate broadband 0 20 hz ground motion time histories for a m 6 5 earthquake on the seattle fault low frequencies 1 hz are calculated by a stochastic method that uses a fractal subevent size distribution to give an 2 displacement spectrum time histories are calculated for a grid of stations and then corrected for the local site response using a classification scheme based on the surficial geology average shear wave velocity profiles are developed for six surficial geologic units artificial fill modified land esperance sand lawton clay till and tertiary sandstone these profiles together with other soil parameters are used to compare linear equivalent linear and nonlinear predictions of ground motion in the frequency band 0 15 hz linear site response corrections are found to yield unreasonably large ground motions equivalent linear and nonlinear calculations give peak values similar to the 1994 northridge california earthquake and those predicted by regression relationships ground motion variance is estimated for 1 randomization of the velocity profiles 2 variation in source parameters and 3 choice of nonlinear model within the limits of the models tested the results are found to be most sensitive to the nonlinear model and soil parameters notably the overconsolidation ratio

metamorphism and crustal stacking in the north indian plate north pakistan abstract the northern part of the indian plate in north pakistan is composed of a number of large scale crustal nappes each of which are stratigraphically distinct and which were stacked late in the main phase of southeasterly directed thrusting associated with the himalayan event the major nappes recognised in the swat to kaghan area of north pakistan are the besham swat hazara banna lower kaghan and upper kaghan nappes metamorphism was synchronous with early stages of deformation within each nappe the metamorphic grade increases upwards an overall inversion that represents post metamorphic imbrication within individual nappes synchronous with the main phase of nappe stacking rather than a hot iron type inversion as described under the mct in nepal and india as a result of this within nappe imbrication each thrust slice within any particular nappe contains rocks of a higher metamorphic grade than those in the slice below with sharp metamorphic breaks across the imbricating thrusts as well as across the major shears that bound the crustal scale nappes uplift along these imbricating thrusts initiated cooling of the stack k ar mica and hornblende cooling ages imply that much of this uplift was completed by 30 ma or within 20 ma of the collision

stick slip advance of the kohat plateau in pakistan in the westernmost himalaya the indian plate is thought to slip beneath the potwar and kohat plateaux on a layer of viscous material in an entirely aseismic manner analysis of insar data from 1992 shows that slip occurred during a rare mw 6 0 earthquake implying that the kohat plateau is locally grounded

debris entrainment and transfer in polythermal valley glaciers hambrey mj bennett mr dowdeswell ja et al 1999 debris entrainment and transfer in polythermal valley glaciers journal of glaciology 45 149 69 86 published 1999

local site characterization and seismic zonation study by utilizing active and passive surface wave methods a case study for the northern side of ankara turkey abstract this study encompasses dynamic soil characterization and site classification zonation mapping of the plio quaternary and especially quaternary alluvial sediments based on the current seismic codes the study area is located in the cubuk district and its surrounding area that is situated towards the north of ankara the capital of turkey the project site is located in a region which has the potential of being seriously affected by probable seismic events occurring along the cubuk fault zone the cubuk fault zone is thought to be a continuation of the dodurga fault zone and a sub fault belt of the north anatolian fault system that is one of the most prominent fault systems in turkey with a significant earthquake potential sediment characteristics were determined and soil profiles were characterized by surface wave methods at different locations non invasive seismic methods were used to obtain a shear wave velocity profile at 41 sites and two measurements were taken at each site for passive and active surface wave methods the multichannel analysis of surface wave method masw and the microtremor array method mam which gave comparable results were used as active and passive surface wave methods respectively by combining these two techniques the shear wave velocity profile of the site was obtained additionally the mam survey alone was implemented at 10 of the sites especially to get information on the deeper parts of the soil profiles the geological characteristics of these sedimentary units were compared with the geological and geotechnical boring and seismic site characterization studies to classify the soil deposits therefore the average shear wave velocity results and the variable characteristics of the seismic data along the soil profiles were correlated with these boring studies this was performed to develop site categories which took site conditions into account according to the design codes of ibc international building code 2006 and tsc turkish seismic code 1998 consequently the regional site classification map of the north of the cubuk basin considering site classes was assessed based on the average shear wave velocity vs30 results in ibc 2006 and the shear wave velocity data and thickness of the surface layer based on the vs values in the tsc

regional arias intensity attenuation relationship for taiwan considering vs30 the arias intensity is a measure of earthquake intensity arrived at through the integration of a square of the acceleration time history it has been demonstrated to be an effective predictor of earthquake damage potential in relation to short period structures liquefaction and seismic slope stability and has begun to be considered as a ground motion measure suitable for use in probabilistic seismic hazard analysis psha as well as earthquake loss estimation a new empirical arias intensity attenuation relationship for shallow crustal earthquakes is developed where both fault type and a continuous site variable vs30 are considered the relationship is based on a large number of strong motion records 6570 from a wide range of earth quake magnitudes 3 9 7 6 from the taiwan strong motion instrument program tsmip network its functional form is modified from that of travasarou et al 2003 which is derived from a point source model and the coefficients are determined through nonlinear regression analyses using a mixed effects model the results show that the incorporation of vs30 can significantly reduce regression error the arias intensity value predicted in the present study is generally similar to that obtained by travasarou et al 2003 but is different in detail being more suitable for usage in psha for a tectonically young orogenic belt like that in taiwan or new zealand

contemporary tectonics of the himalayan frontal fault system folds blind thrusts and the 1905 kangra earthquake the sub himalayan fold thrust belt consists of deformed late cenozoic and older deposits south of the main boundary thrust mbt in pakistan east of the indus river the sub himalaya comprises the potwar plateau and the salt range which is thrust southward over the jhelum river floodplain along the salt range thrust although an estimated 9 14 mm a 1 shortening has been taken up on the salt range thrust during the last 2 ma the range front scarp does not show signs of recent faulting shortening may be shifting southward to the lilla overpressured anticline which rises from the jhelum floodplain as a fault propagation fold farther east shortening is partitioned among several anticlines underlain by foreland and hinterland dipping blind thrusts southeast of the main deformation zone the pabbi hills overpressured anticline is best explained as a fault propagation fold throughout the potwar plateau and salt range thrusts and folds rise from a basal decollement horizon in eocambrian evaporites the pakistani part of the decollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths in india and nepal the sub himalaya is narrower reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland the southern boundary of the sub himalaya is the himalayan front fault discontinuous because part of the shortening is expressed at the surface by folding broad alluvial synclinal valleys dun valleys are bounded on the south by rising barrier anticlines of siwalik molasse the 1905 kangra earthquake m8 produced uplift on the mohand anticline and the dehra dun valley suggesting that this earthquake occurred on a decollement horizon above basement downdip from the fold if so the kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold

instrumental intensity distribution for the hector mine california and the chi chi taiwan earthquakes comparison of two methods we compare two methods of seismic intensity estimation from ground motion records for the two recent strong earthquakes the 1999 m 7 1 hector mine california and the 1999 m 7 6 chi chi taiwan the first technique utilizes the peak ground acceleration pga and velocity pgv and it is used for rapid generation of the instrumental intensity map in california the other method is based on the revised relationships between intensity and fourier amplitude spectrum fas the results of using the methods are compared with independently observed data and between the estimations from the records for the case of the hector mine earthquake the calculated intensities in general agree with the observed values for the case of the chi chi earthquake the areas of maximum calculated intensity correspond to the areas of the greatest damage and highest number of fatalities however the fas method producees higher intensity values than those of the peak amplitude method the specific features of ground motion excitation during the large shallow thrust earthquake may be considered a reason for the discrepancy the use of pga and pgv is simple however the use of fas provides a natural consideration of site amplification by means of generalized or site specific spectral ratios because the calculation of seismic intensity maps requires rapid processing of data from a large network it is very practical to generate a first order map from the recorded peak motions then a second order map may be compiled using an amplitude spectra method on the basis of available records and numerical modeling of the site dependent spectra for the regions of sparse station spacing

glaciohydraulic supercooling a freeze on mechanism to create stratified debris rich basal ice i field evidence debris laden ice accretes to the base of matanuska glacier alaska u s a from water that supercools while flowing in a distributed drainage system up the adverse slope of an overdeepening frazil ice grows in the water column and forms aggregates while other ice grows on the glacier sole or on substrate materials sediment is trapped by this growing ice forming stratified debris laden basal ice growth rates of 0 1 m a 1 of debris rich basal ice are possible the large sediment fluxes that this mechanism allows may have implications for interpretation of the widespread deposits from ice that flowed through other overdeepenings including heinrich events and the till sheets south of the laurentian great lakes

evaluation of empirical ground motion relations in southern california regression analysis to develop empirical ground motion relations that predict ground motion characteristics as a function of magnitude and distance are an essential part of seismic design and probabilistic seismic hazard assessment several different ground motion relations have been presented based on different data and assumptions this study evaluates five that were judged likely to be appropriate for southern california we test them against the strong motion data recorded in this region between 1933 and 1994 for magnitudes between 5 0 and 7 5 and for distances up to 150 km the ground motion parameters examined are peak acceleration and response spectral acceleration sa at 0 3 1 0 and 3 0 sec periods some of the ground motion relations are more consistent than others with the limited set of southern california data but none of them stand out as either best or unacceptable residuals from all of these models indicate that as the magnitude increases the standard deviation decreases at high frequencies but increases for sa 3 0 sec among those found to be most consistent significant differences remain with respect to predicting ground motion under conditions not yet sampled by the existing observational data set e g near source shaking for large earthquakes theoretical simulations are used elsewhere in this report ni et al 2000 anderson 2000 to help resolve these ambiguities the implications with respect to probabilistic seismic hazard assessment are explored in field and petersen 2000

controlled moraines origins characteristics and palaeoglaciological implications abstract controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de icing and possess clear linearity due to the inheritance of the former pattern of debris rich folia in the parent ice linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt out as a result moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris rich ice was concentrated in frozen toe zones recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that a controlled moraine development can be ascribed to a specific process e g englacial thrusting or supercooling and b controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts e g ancient polythermal or supercooled snouts these assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris rich ice thickening mechanisms are seen to produce the same geomorphic features polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier permafrost interface end moraines lie on a process form continuum constrained by basal thermal regime the morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores but the final deposits landforms tend to consist of discontinuous transverse ridges with intervening hummocks preserving only a weak impression of the former englacial structure these are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice walled lake plains and lying down flow of streamlined landforms produced by warm based ice a variety of debris entrainment mechanisms can produce the same geomorphic signature spatial and temporal variability in process form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin

compilation of a local vs profile database and its application for inference of vs30 from geologic and terrain based proxies abstract the time averaged shear wave velocity in the upper 30 m of a site v s 30 is commonly used for ground motion prediction when measured velocities are unavailable v s 30 is estimated from proxy based relationships developed for application on global or local scales we describe the development of a local relationship for greece which begins with compilation of a profile database pdb from published sources and engineering reports the pdb contains 314 sites 238 have profile depths 30 m and 59 are within 100 m of accelerographs we find existing relations for extrapolating a time averaged velocity for depths less than 30 m to v s 30 to overpredict v s 30 we present equations for these extrapolations we then compile proxies for pdb sites including terrain type surface geology and surface gradients at 30 and 3 arcsec resolution from radar derived digital elevation models dems when checked against ground survey data we find ground elevations from 3 arcsec dems to be more accurate relative to survey data than alternative 30 9 and 1 arcsec dems drawing upon expert opinion we develop geologic categories based on age gradation and depositional environment and assign such categories to pdb sites we find an existing 30 arcsec gradient based global model to be biased relative to local v s 30 data for gradients 0 05 m m bias relative to a california model is also found for four of the eight well populated geomorphic categories and new local values are provided we find statistically significant effects of the 3 arcsec gradient on v s 30 for quaternary and tertiary materials but no gradient effect for those from the mesozoic among quaternary sediments holocene mapped quaternary age unspecified and mixed fine gradation materials exhibit consistent v s 30 gradient trends whereas pleistocene and coarse gradation sediments have faster velocities for the study region we recommend use of the modified terrain and geology based methods in combination for proxy based v s 30 estimation online material profile database spreadsheet and figures of elevation residuals

seismic ground motion hazard mapping incorporating site effects for los angeles orange and ventura counties california a geographical information system application abstract the seismic ground motion hazard with site conditions incorporated is mapped for a 10 probability of exceedance in 50 years for the three counties affected by the 1994 northridge earthquake mw 6 7 the source model of petersen et al 1996 was used to calculate peak horizontal acceleration pga and 5 damped spectral acceleration sa levels at 0 3 and 1 sec periods for alluvium soft rock and hard rock site conditions a geologic map that differentiates the three site conditions was produced using shear wave velocity maps of tinsley and fumal 1985 and extended into other areas that were not mapped by tinsley and fumal using 1 250 000 scale geologic maps ground motion maps for each site condition were overlaid with the geologic map to produce the resulting hazard maps the effect of geology on the hazard is observed only slightly in the peak ground acceleration map more in the 0 3 sec sa map and significantly more in the 1 sec sa map the uncertainties for ground motions represented on these three maps ranges from 0 1 to 0 3 g for pga and 0 2 to 1 0 for sa in general 95 confidence limits are about 50 of the mean ground motion value

mechanics of the salt range potwar plateau pakistan a fold and thrust belt underlain by evaporites the salt range and potwar plateau are part of the active foreland fold and thrust belt of the himalaya in northern pakistan in this region the distance from the main boundary thrust mbt to the front of the fold and thrust belt is very wide 100 150 km because a thick evaporite sequence forms the zone of decollement recent studies have combined seismic reflection profiles petroleum exploration wells bouguer gravity anomalies and surface geology to construct cross sections in the eastern central and western salt range potwar plateau areas in this study the sections are compared with a model that considers the mechanics of a fold and thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer chapple 1978 davis et al 1983 dahlen et al 1984 dahlen 1984 models which include the effects of evaporites at the base chapple 1978 davis and engelder 1985 suggest that these thrust belts will have 1 narrow 1 cross sectional tapers 2 larger widths than areas not underlain by evaporites 3 symmetrical structures and 4 changes in deformational style at the edge of the evaporite basin the section across the eastern potwar plateau most closely resembles this latter model having 1 a taper of 0 8 0 1 2 a width of 100 150 km 3 thrust faults that verge both to the north and south and 4 structures rotated 30 counterclockwise with respect to the salt range from the observed taper and pore fluid pressures of the eastern potwar plateau estimates of the values for the yield strength of the evaporites o and the coefficient of internal friction of the overlying wedge are calculated as o 1 33 1 50 mpa and 0 95 1 04 which are then applied to the other cross sections in the central and western sections a basement uplift the sargodha high interferes with the front of the fold and thrust belt this feature causes the ramping of the salt range thrust and produces a relatively steep basement slope 2 4 beneath the potwar plateau this dip in the presence of the weak evaporite decollement is sufficient to provide critical taper no topographic slope is necessary and the thrust wedge of the southern potwar plateau is pushed over the decollement without significant internal deformation the northern potwar plateau is strongly folded and faulted yet the topographic slope remains flat although the deformation suggests that evaporites are not present there the observed taper in the northern potwar plateau is best fitted by the model with evaporites at the decollement combining this with published paleomagnetic and geologic constraints a model for the evolution of the northern potwar plateau suggests that the area deformed as a steeply tapered 3 5 5 5 thrust wedge until approximately 2 million years ago when the southward propagating decollement encountered the evaporites between 2 ma and the present the northern potwar plateau has been pushed along the salt decollement without deformation and erosion has reduced its original steep topographic slope to a nearly level surface

rupture process and near source shaking of the 1965 seattle tacoma and 2001 nisqually intraslab earthquakes 1 we inverted teleseismic data for the 1965 seattle tacoma earthquake slip and rake the earthquake had 2 asperities of 12 and 16 km2 near the hypocenter with average slip of 2 and 2 8 m respectively mo 9 4 1025 dyne cm mw 6 6 we also inverted strong motion and teleseismic data for the 2001 nisqually earthquake this earthquake had 2 subevents with an asperity area of 45 km2 between 59 and 62 km depth with an average slip of 1 7 m mo 1 7 1026 dyne cm mw 6 8 shake maps of peak ground acceleration pga and spectral acceleration sa were generated using a time domain approach including slip model site and basin depth corrections based on california geology corrections reduced the residuals between observed and predicted pga and sa the simulated pattern of shaking from the 1965 earthquake was twice as high as in the 2001 earthquake due to the proximity of the 1965 epicenter to sedimentary basins

dynamic site characterization and correlation of shear wave velocity with standard penetration test n values for the city of agartala tripura state india seismic site characterization is the basic requirement for seismic microzonation and site response studies of an area site characterization helps to gauge the average dynamic properties of soil deposits and thus helps to evaluate the surface level response this paper presents a seismic site characterization of agartala city the capital of tripura state in the northeast of india seismically agartala city is situated in the bengal basin zone which is classified as a highly active seismic zone assigned by indian seismic code bis 1893 indian standard criteria for earthquake resistant design of structures part 1 general provisions and buildings according to the bureau of indian standards new delhi 2002 it is the highest seismic level zone v in the country the city is very close to the sylhet fault bangladesh where two major earthquakes m w 7 have occurred in the past and affected severely this city and the whole of northeast india in order to perform site response evaluation a series of geophysical tests at 27 locations were conducted using the multichannel analysis of surface waves masw technique which is an advanced method for obtaining shear wave velocity v s profiles from in situ measurements similarly standard penetration test spt n bore log data sets have been obtained from the urban development department govt of tripura in the collected data sets out of 50 bore logs 27 were selected which are close to the masw test locations and used for further study both the data sets v s profiles with depth and spt n bore log profiles have been used to calculate the average shear wave velocity v s30 and average spt n values for the upper 30 m depth of the subsurface soil profiles these were used for site classification of the study area recommended by the national earthquake hazard reduction program nehrp manual the average v s30 and spt n classified the study area as seismic site class d and e categories indicating that the city is susceptible to site effects and liquefaction further the different data set combinations between v s and spt n corrected and uncorrected values have been used to develop site specific correlation equations by statistical regression as v s is a function of spt n value corrected and uncorrected considered with or without depth however after considering the data set pairs a probabilistic approach has also been presented to develop a correlation using a quantile quantile q q plot a comparison has also been made with the well known published correlations for all soils available in the literature the present correlations closely agree with the other equations but comparatively the correlation of shear wave velocity with the variation of depth and uncorrected spt n values provides a more suitable predicting model also the q q plot agrees with all the other equations in the absence of in situ measurements the present correlations could be used to measure v s profiles of the study area for site response studies

thrust kinematics in the kohat plateau trans indus range pakistan abstract the kohat plateau consists of a heavily deformed and structurally elevated thrust sheet pop ups broad synclines and narrow fault and evaporite cored anticlines record high level translation of a large thrust mass along eocene evaporites a lower detachment level is also inferred located at the base of the mesozoic palaeozoic section this lower detachment is common to both the kohat and the adjacent potwar plateaux whereas the upper level is restricted to the kohat beneath the kohat a blind imbricate stack of pre tertiary rocks is developed above their roof thrust the foreland basin fill of kohat records greater internal deformation compared to that of the adjacent potwar plateau in contrast the potwar thrust belt displays a greater amount of overthrusting on its basal surface this displacement emerging in the salt range total shortening across the two plateaux is comparable but is accommodated in an areally smaller thrust belt with a higher structural relief in the kohat as compared to the potwar structural province the resultant geographical offset of the thrust front is denoted by the hukni kalabagh lateral ramp the differences in the thrust kinematics are tentatively suggested to be caused by the mechanical response of the orogenic wedge to different imposed geometries of the wedge laterally within the basin the kohat plateau appears to have a lower basal dip than does the western potwar and thus shows greater internal deformation

a probabilistic approach to seismic hazard in metropolitan france in this study we applied a probabilistic methodology to seismic hazard assessment in metropolitan france for that purpose we determined an attenuation law adapted to the french context this law holds for peak ground acceleration on stiff bedrock for earthquakes with local magnitudes between 2 5 and 5 6 recorded in near field at distances between 3 and 50 km geological conditions are taken into account by means of a three categories classification of lithologies based on a 1 1 000 000 geological map the seismotectonic zonation consists of areas of diffuse seismicity characterized by a frequency magnitude distribution in southeastern france active faults are considered in a test case and are assumed to follow the characteristic earthquake model we performed hazard curves for six french cities and maps of peak horizontal ground accelerations expected for return periods of 475 975 and 1975 years in the country sensitivity tests have been performed the uncertainty introduced by ground motion variability seems minor compared with that due to the choice of the attenuation law this study points to the importance of testing internal consistency of the various data and laws used in any seismic hazard analysis in particular here the type of magnitude used to predict ground motion if not some systematic bias is introduced that may result in systematic errors on peak ground acceleration determination we also show that the introduction of possibly very large and infrequent events known only from paleoseismic investigations may have a dramatic impact on the hazard especially when long periods of time are considered

real time generation of shakemaps in the southeastern alps abstract the aim of this study is the real time generation of shakemaps in the southeastern alps area the shakemap software has been adapted to the southeastern alps region and implemented to obtain a stable interface with the antelope acquisition system in order to extract the ground motion parameters from the waveforms and to generate shakemaps within 5 min of the earthquake occurrence to evaluate the influence of the station density synthetic seismograms are computed for the bovec northwest slovenia 2004 earthquake and various shakemaps are generated by varying the grid size of the simulated recording stations the results indicate that a dense and uniform spatial distribution of stations in the field is essential to produce accurate shakemaps and the present density of stations in central friuli is sufficient for a reliable estimate of the extent of the area of strongest shaking the related maps are generated in real time or quasi real time using the region specific ground motion predictive equations and empirical relations that predict the macroseismic intensity from the recorded ground motion the model is validated by comparison between observed data and shakemap results for both weak motions claut 2007 earthquake and strong motions bovec 1998 earthquake

mineral and chemical composition of karak mudstone kohat plateau pakistan implications for smectite illitization and provenance abstract the karak mudstone interbedded in an eocene evaporite sequence is dominated by r 1 ordered illite smectite with a 20 to 30 expandable component minor phases include kaolinite chlorite illite muscovite plagioclase potash feldspar quartz dolomite and pyrite the present illite smectite was probably originally smectite or highly expandable illite smectite which underwent conversion to illite smectite with a low expandable component in a comparatively low temperature ca 100 c closed system sedimentary basinal diagenetic environment at a depth of ca 5 km al 3 and k necessary for the conversion reaction were provided through the breakdown of potash feldspar burial under a 5 km thick pile of sediments produced some of the observed structures whole rock chemistry presented here suggests that the mudstone formed by severe weathering of acidic source rocks the influx of freshwater probably flushed out ba rb ca and mn from the restricted basin

development of a geotechnical and geophysical database for seismic zonation of the ankara basin turkey engineering geological and geotechnical site characteristics were assessed and seismic hazard studies performed for the upper pliocene to pleistocene fluvial and quaternary alluvial and terrace deposits for a site west of ankara turkey sediment conditions were determined and a soil profile was characterized by surface geophysical methods these studies were integrated with existing in situ characterization studies to create a seismic and geotechnical database for the site a seismic zonation map of the site was then prepared site classification systems were assigned to account for site effects in relation to seismic hazard assessments the consequences of the seismic hazards were investigated and recommendations were presented

trinet strong motion data from the m 7 1 hector mine california earthquake of 16 october 1999 the m w 7 1 hector mine earthquake of october 16 1999 was recorded by more than 300 stations of trinet which is administered cooperatively by the california division of mines and geology s california strong motion instrumentation program cdmg csmip california institute of technology and the u s geological survey usgs the earthquake occurred in a remote part of the mojave desert approximately 190 km northeast of downtown los angeles and there were no strong motion stations close to the surface rupture the nearest station hector is about 27 km north of the epicenter it recorded a peak horizontal ground acceleration of 0 33g the two next closest stations amboy and joshua tree are to the east and south both at epicentral distances of about 50 km each recorded peak ground accelerations of about 0 2g the new digital instruments installed for the trinet project recorded a large set of reliable data at epicentral distances up to 275 km these data can significantly improve empirical peak ground motion attenuation relationships which are usually developed for distances only up to 100 km boore et al 1993 1997 because adequate data have not been available at greater distances hector mine peak ground motions demonstrate reasonable agreement with empirical attenuation relationships for acceleration in contrast higher than expected ground velocities and displacements were recorded at epicentral distances of about 150 to 220 km especially in the los angeles sedimentary basin where anomalously high amplitude displacements with periods of 6 to 7 sec were recorded in los angeles long beach and other areas these long period surface or basin generated waves can have significant effects on large structures the m w 7 3 landers earthquake of 1992 similarly produced strong long period waves in the basin the peak ground motions produced by the landers earthquake were on average 1 6 times higher than for the hector mine earthquake in the los angeles area ground motion data recorded by digital instruments were uniformly processed in the frequency band 0 067 to 46 hz 0 022 15 sec the processed data set includes records from 213 ground response stations in an effort to make strong motion data available quickly to the engineering and scientific communities important records from this event were made available by file transfer protocol ftp beginning the day of the earthquake

sediments and landforms at kviarjokull southeast iceland a reappraisal of the glaciated valley landsystem abstract eyles identified kviarjokull an outlet of the icecap oraefajokull southeast iceland as an exemplar of the glaciated valley landsystem emphasising rockfall debris supply passive transport and reworking of a thick cover of supraglacial morainic till in this paper we take a fresh look at the sediments and landforms of kviarjokull focusing on clast form analysis to reconstruct primary transport pathways new data demonstrate the importance of active transport of debris derived from the glacier bed substantial portions of the supraglacial debris cover can be traced back to englacial channel fill deposits or anomalously thick exposures of basal ice these two types of sediments also make up much of kviarjokull s large neoglacial moraine rampart we attribute the abundance of these non rockfall sediments to the presence of a terminal overdeepening and the switch from predominantly subglacial to predominantly englacial drainage that this induces this hydrological switch enhances retention of debris within ice transport preventing it from being washed away and making it available to feed ice marginal moraine formation the complexity of sediment transport processes observed at kviarjokull and the contrast between it and alpine glaciers undermines any single concept of the glaciated valley landsystem accordingly we propose kviarjokull as the type example of a distinct subclass defined by its moderate relief high debris turnover and drainage behaviour characteristic of an overdeepened basin

late wisconsin landform distribution and glacier bed conditions in wisconsin abstract the late wisconsin laurentide ice sheet advanced across permafrost and reached its maximum extent in wisconsin between about 18 000 and 15 000 years ago deep permafrost persisted in southern wisconsin until about 14 000 years ago and in northern wisconsin until about 13 000 years ago we suggest that during maximum glaciation a zone about 5 km wide in the south and 20 km wide in the north along the margin of the late wisconsin glacier was frozen to its bed meltwater from farther behind the margin where the bed was at least locally thawed cut a series of closely spaced tunnel channels through the frozen bed zone these channels most likely formed episodically and they were the source for much of the meltwater stream sediment deposited in broad outwash plains beyond the ice margin frozen bed conditions near the margin also likely contributed to increased upward shearing of sediment and the accumulation of thicl supraglacial sediment in northern areas up ice from the frozen bed zone the glacier bed was at least locally thawed in a zone about 75 km wide extensive drumlin fields formed in the area of the bed that was thawed by about 13 000 years ago permafrost melted in northern wisconsin and thawed bed conditions probably extended to the ice margin throughout wisconsin and adjacent areas after about 13 000 years ago in northern wisconsin the glacier was sliding on its bed and forming drumlins out to the ice margin and thick supraglacial sediment no longer accumulated

predictions of shear wave velocities in southern california using surface geology a new model of the average shear wave velocity in the uppermost 30 m has been generated by extrapolation of discrete velocity profiles using surface geology at several scales statistical methods have been applied to create a map that is no more complicated than is supported by the velocity data several geologic units with similar responses are grouped together the resulting map is simpler than previous ones and yet fits the observed velocity profiles better than earlier more complicated maps analysis within a geographic information system will permit updates and modification of the map as new velocity data are added