on the nature and rate of resurfacing of venus crater production and obliteration are modeled for the plains of venus using 1 the observed distribution of venus crossing asteroids and comets 2 viscous relaxation of crater topography and 3 erosion and burial by atmospheric volcanic and tectonic processes crater lifetimes are assumed to be proportional to crater depths for both classes of obliterative processes although the individual criteria vary an average crater retention age between 0 4 to 2 0 ga is estimated for plains under the assumption that craters are produced and not removed the range is driven by uncertainty in identifying degraded impact as opposed to volcanic craters on the other hand crater retention ages greater than about 1 6 ga are unlikely if viscous relaxation operates without loading of crater floors by burial our preferred model has plains subject to crater production and obliteration processes that vary over both space and time in some areas radar bright crater ejecta haloes are preserved for long periods of time because volcanism tectonism and weathering occurs at rates 1 km ga viscous relaxation has probably generated numerous shallow craters in these relatively quiescent regions in other areas volcanism and tectonism have resurfaced the terrain at rates greater than several km ga the global coverage and high resolution sar and altimetry data expected from magellan will allow testing of this model based on detailed crater observations diameter depth distributions morphologic criteria surface scattering properties and their association with volcanic and tectonic features

application of numerical wave propagation techniques to study local soil effects the case of benevento italy many of the numerical techniques used for seismic zonation studies treat one dimensional structural models and or the incidence of plane polarized body waves these techniques are often not adequate for laterally heterogeneous structures and for sources that are not located beneath the site of interest in such cases a more rigorous treatment of the combined effects of the source the path and the site response is needed this can be accomplished with a hybrid approach combining modal summation and the finite difference technique to demonstrate the differences between these techniques the ground motion in the city of benevento italy is modelled we first compare the results obtained with one and two dimensional structural models for vertical incidence of plane polarized body waves these results are then compared with those obtained with the hybrid approach for two dimensional structural models

site specific modeling of sh and p sv waves for microzonation study of kolkata metropolitan city india kolkata one of the oldest cities of india is situated over the thick alluvium of the bengal basin where it lies at the boundary of the zone iii and zone iv of the seismic zonation map of india an example of the study of site effects of the metropolitan kolkata is presented based on theoretical modeling full synthetic strong motion waveforms have been computed using a hybrid method that combines the modal summation and finite difference techniques the 1964 calcutta earthquake which was located at the southern part of kolkata is taken as the source region with the focal mechanism parameters of dip 32 strike 232 and rake 56 four profiles are considered for the computation of the synthetic seismograms from which the maximum ground acceleration a max is obtained response spectra ratios rsr are then computed using a bedrock reference model to estimate local amplifications effects the a max varies from 0 05 to 0 17 g and the comparison of the a max with the different intensity scales mm msk rf and mcs shows that the expected intensity is in the range from vii to x mcs for an earthquake of magnitude 6 5 at an epicentral distance of about 100 km this theoretical result matches with the empirical historical and recent intensity observations in kolkata the rsr as a function of frequency reaches the largest values largest amplification in the frequency range from 1 0 to 2 0 hz the largest site amplification is observed at the top of loose soil

first order seismic microzonation of haldia bengal basin india using a gis platform the seismic microzonation of the bengal basin haldia region india is carried out using the analytical hierarchy process ahp on the geographic information system gis three themes are used for the seismic microzonation namely peak ground acceleration pga predominant frequency and elevation map an analysis of the maximum magnitude mmax and the b value is carried out after preparing the earthquake catalogue from various sources on the basis of the tectonic set up and seismicity of the region five seismic zones are delineated which can be a threat to haldia they are broadly classified as zone 1 arakan yoma zone ayz zone 2 himalayan zone hz zone 3 shillong plateau zone spz zone 4 bay of bengal zone bbz and zone 5 shield zone sz the mmax for zones 1 2 3 4 and 5 are 8 30 0 51 9 09 0 58 9 20 0 51 6 62 0 43 and 6 61 0 43 respectively the pga value is computed for haldia following the attenuation relationship taking the mmax of each source zone the expected pga at haldia varies from 0 09 0 19 g the predominant frequency of haldia is also calculated using the h v ratio with a frequency ranging from 0 1 3 0 hz the elevation map of haldia is also generated using the shuttle radar topography mission strm data a first order seismic microzonation map of haldia is prepared in which four zones of hazard have been broadly classified for haldia as very high seismic hazard zone high seismic hazard zone moderate seismic hazard zone and less seismic hazard zone the very high seismic hazard zone is observed along the southern part of haldia where there are major industrial and port facilities the pga for the four hazard zones are 0 09 0 13 g for low hazard zone 0 13 0 15 g for moderate hazard zone 0 15 0 16 g for high hazard zone and 0 16 0 19 g for very high hazard zone

impact craters and venus resurfacing history venusian impact crater size frequency distributions locations and preservation states were analyzed to reconstruct the history of resurfacing by tectonism and volcanism an atmospheric transit model for meteoroids demonstrates that for craters larger than about 30 km the size frequency distribution is close to the atmosphere free case with this result and assuming that the surface records a crater production population a catastrophic resurfacing model crm an age of cessation of rapid resurfacing of 500 ma is obtained crater locations are widely dispersed across venus and the hypothesis that they are completely spatially random csr cannot be rejected however craters that show embayment by plains materials or modification by throughgoing faults i e tectonized are preferentially found in areas with relatively few craters overall the primary region where these modified craters are found is the aphrodite volcanotectonic zone extending from ovda regio on the west to the region east of atla regio these results together with the appearance of plains material on most crater floors and evidence for complex volcanic stratigraphy imply that a range of surface ages are recorded by the impact crater population e g the aphrodite zone is relatively young an end member model equilibrium resurfacing model erm was developed to quantify resurfacing scenarios in the erm venus has been resurfacing at an average rate of approximately 1 km2 yr 1 however the crm and erm are idealized end member representations of possible resurfacing histories for both models the resurfacing rate can be expressed as the product of resurfacing patch area a normalized by planetary surface area and the frequency of resurfacing events numerical simulations of resurfacing showed that there are two solution branches that satisfy the csr constraint a 0 1 74 diameter circle the former range corresponds to resurfacing diameters smaller than the average intercrater distance whereas the latter is associated with large infrequent events resurfacing 10 of the planet every 50 ma to 100 every 500 ma the observed fraction of embayed and tectonized craters further constrains values of a and only values near 0 0003 are admissible the resurfacing model that best fits all of the statistical and geological constraints has resurfacing with small patches that occurs in any given geological episode in only a limited number of regions on the planet

the main features of the local geological conditions can explain the macroseismic intensity caused in xiji langfu beijing by the ms 7 7 tangshan 1976 earthquake the special geological conditions in the xiji langfu area are the main reason for the anomalous high macroseismic intensity caused by the tangshan 1976 earthquake the area is formed by deep deposits mainly alluvium sands and clays poorly consolidated and with high water content that have been trapped by the xiadian fault from simulated ground motion we have computed quantities commonly used for engineering purposes like the acceleration maximum amplitude amax and the total energy of ground motion w which is related to the arias intensity the thick low velocity deposits are responsible for the large increment of the values of amax and w inside the basin on the two sides of the xiadian fault amax and w can vary by 200 and 700 respectively and these variations are quite stable with varying thickness of the sedimentary deposit used in the models with the existing relationships between acceleration amax and macroseismic intensity i our results can explain the large values of i observed in the xiji langfu area in connection with the tangshan earthquake

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

hot spot evolution and the global tectonics of venus the global tectonics of venus may be dominated by plumes rising from the mantle and impinging on the lithosphere giving rise to hot spots global sea floor spreading does not take place but direct convective coupling of mantle flow fields to the lithosphere leads to regional scale deformation and may allow lithospheric transport on a limited scale a hot spot evolutionary sequence comprises i a broad domal uplift resulting from a rising mantle plume ii massive partial melting in the plume head and generation of a thickened crust or crustal plateau iii collapse of dynamic topography and iv creep spreading of the crustal plateau crust on venus is produced by gradual vertical differentiation with little recycling rather than by the rapid horizontal creation and consumption characteristic of terrestrial sea floor spreading

an overview of venus geology the magellan spacecraft is producing comprehensive image and altimetry data for the planet venus initial geologic mapping of the planet reveals a surface dominated by volcanic plains and characterized by extensive volcanism and tectonic deformation geologic and geomorphologic units include plains terrains tectonic terrains and surficial material units understanding the origin of these units and the relation between them is an ongoing task of the magellan team

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

a hybrid method for the estimation of ground motion in sedimentary basins quantitative modeling for mexico city to estimate the ground motion in two dimensional 2d laterally heterogeneous anelastic media a hybrid technique has been developed that combines modal summation and the finite difference method in the calculation of the local wave field owing to a seismic event both for small and large epicentral distances it is possible to take into account the source path and local soil effects as a practical application we have simulated the ground motion in mexico city caused by the michoacan earthquake of september 19 1985 by studying the one dimensional 1d response of the two sedimentary layers present in mexico city it is possible to explain the difference in amplitudes observed between records for receivers inside and outside the lake bed zone these simple models show that the sedimentary cover produces the concentration of high frequency waves 0 2 to 0 5 hz on the horizontal components of motion the large amplitude coda of ground motion observed inside the lake bed zone and the spectral ratios between signals observed inside and outside the lake bed zone can only be explained by 2d models of the sedimentary basin in such models the ground motion is mainly controlled by the response of the uppermost clay layer the synthetic signals explain the major characteristics relative amplitudes spectral ratios and frequency content of the observed ground motion the large amplitude coda of the ground motion observed in the lake bed zone can be explained as resonance effects and the excitation of local surface waves in the laterally heterogeneous clay layer also for the 1985 michoacan event the energy contributions of the three subevents are important to explain the observed durations

initial results for the north pole of the moon from mini sar chandrayaan 1 mission 1 we present new polarimetric radar data for the surface of the north pole of the moon acquired with the mini sar experiment onboard india s chandrayaan 1 spacecraft between mid february and mid april 2009 mini sar mapped more than 95 of the areas polewards of 80 latitude at a resolution of 150 meters the north polar region displays backscatter properties typical for the moon with circular polarization ratio cpr values in the range of 0 1 0 3 increasing to over 1 0 for young primary impact craters these higher cpr values likely reflect surface roughness associated with these fresh features in contrast some craters in this region show elevated cpr in their interiors but not exterior to their rims almost all of these features are in permanent sun shadow and correlate with proposed locations of polar ice modeled on the basis of lunar prospector neutron data these relations are consistent with deposits of water ice in these craters

fundamental issues in the geology and geophysics of venus a number of important and currently unresolved issues in the global geology and geophysics of venus will be addressable with the radar imaging altimetry and gravity measurements now forthcoming from the magellan mission among these are the global volcanic flux and the rate of formation of new crust the global heat flux and its regional variations the relative importance of localized hot spots and linear centers of crustal spreading to crustal formation and tectonics and the planform of mantle convection on venus and the nature of the interactions among interior convective flow near surface deformation and magmatism

modelling of seismic ground motion in santiago de cuba city from earthquakes in oriente fault seismic zone we present the results of complete p sv and sh waves modelling up to a maximum frequency of 1 hz along two profiles in santiago de cuba city the seismic sources are located in the depth range from 10 to 40 km on the oriente fault zone at distances of several tens of kilometres from the city the calculation has been made by a hybrid method modal summation in the regional anelastic model one dimensional where the source is buried and finite differences in the local sedimentary anelastic models two dimensional the analysis of the influence of the depth and of the distance of the source on the site effects shows that standard traditional methods based on the deconvolution analysis of the rock outcrop motion can lead to erroneous results

long period ground motion at bedrock level in delhi city from himalayan earthquake scenarios delhi the capital of india is prone to severe seismic hazards not only from local events but also from himalayan earthquakes at distances of 250 300 km standard techniques are not sufficiently reliable to completely characterize the seismic hazards in this case due to the difficulty of predicting the occurrence of earthquakes frequency magnitude relations and of properly treating the propagation of their effects attenuation laws especially their long period components in order to give a sound description of the seismic ground motion due to an earthquake in such a given range of distances and magnitudes we use modelling techniques developed from physics of the seismic source generation and propagation processes such models take into account the directivity effect of rupture propagation and the attenuation of long period ground motions the generated ground motion scenarios permit us to build a very important knowledge base to be fruitfully used by civil engineers since long period ground motions especially if amplified by deep sedimentary basins can represent a severe threat for large scale structures e g lifelines and bridges and tall buildings which are widespread in fast growing megacities in this study we simulate the ground motion at bedrock level in delhi city for an earthquake scenario corresponding to a source of mw 8 0 located in the central seismic gap of himalayas at an epicentral distance of about 300 km from delhi city by means of several parametric studies we simulate the time histories using size scaled point source space and time scaled point source and extended source models together with the complete time histories displacements velocities and accelerations from which the peak amplitudes have been extracted we have also used the displacement response spectrum to characterize the seismic input at delhi not only is the displacement response spectrum of great significance to modern displacement based design engineering approaches but it is probably the best parameter by which to characterize the destructiveness potential of earthquakes located at such great distances from the target sites of the order of 300 km since the energy of the seismic input is mainly concentrated at long periods in general greater than 1 s and it cannot be determined by straightforward integration of velocity or acceleration response spectra

direct measurement of hydroxyl in the lunar regolith and the origin of lunar surface water remote sensing discoveries of hydroxyl and water on the lunar surface have reshaped our view of the distribution of water and related compounds on airless bodies such as the moon the origin of this surface water is unclear but it has been suggested that hydroxyl in the lunar regolith can result from the implantation of hydrogen ions by the solar wind here we present fourier transform infrared spectroscopy and secondary ion mass spectrometry analyses of apollo samples that reveal the presence of significant amounts of hydroxyl in glasses formed in the lunar regolith by micrometeorite impacts hydrogen isotope compositions of these glasses suggest that some of the observed hydroxyl is derived from solar wind sources our findings imply that ice in polar cold traps could contain hydrogen atoms ultimately derived from the solar wind as predicted by early theoretical models of water stability on the lunar surface we suggest that a similar mechanism may contribute to hydroxyl on the surfaces of other airless terrestrial bodies where the solar wind directly interacts with the surface such as mercury and the asteroid 4 vesta

lunar magma ocean crystallization revisited bulk composition early cumulate mineralogy and the source regions of the highlands mg suite abstract crystallization of the lunar magma ocean lmo has been numerically modeled and its products inferred from sample observations but it has never been fully tested experimentally this study is a reexamination of the lmo hypothesis by means of the first experimental simulation of lunar differentiation two end member bulk moon compositions are considered one enriched in refractory lithophile elements relative to earth and one with no such enrichment a two stage model of magma ocean crystallization based on geophysical constraints is simulated and features early crystal suspension and equilibrium crystallization followed by fractional crystallization of the residual magma ocean an initially entirely molten moon is assumed part 1 of this study presented here focuses on stage 1 of this model and considers the early cumulates formed by equilibrium crystallization differences in mantle mineralogy resulting from different bulk moon compositions and implications for the source regions of the highlands mg suite refractory element enriched bulk moon compositions produce a deep mantle that contains garnet and trace cr spinel in addition to low ca pyroxene and olivine in contrast compositions without refractory element enrichment produce a deep dunitic mantle with low ca pyroxene but without an aluminous phase the differences in bulk composition are magnified in the residual melt the residual lmo from the refractory element enriched composition will likely produce plagioclase and ilmenite earlier and in greater quantities both compositions produce mg rich early cumulate piles that extend from the core mantle boundary to 355 km depth if 50 equilibrium crystallization and whole moon melting are assumed these early lmo cumulates provide good fits for the source regions for a component of the high mg ni and co poor parental magmas of the mg suite cumulates if certain conditions are called upon the olivine in early lmo cumulates produced by either bulk moon composition is far too rich in cr to be reasonable for the source regions of the mg suite meaning either core formation in the presence of s and or c must be invoked to deplete the lmo and the crystallizing olivine in cr or that current estimates of the bulk lunar cr content are too high we infer that melts meeting the criteria of the mg suite parents could be produced from early lmo cumulates by solid state kreep and plagioclase hybridization near the base of the crust and subsequent partial melting additionally we propose a revised model for mg suite petrogenesis

impact craters of venus analysis of venera 15 and 16 data from description of impact craters on venus and crater size and depth distributions models are developed that analyze the size distribution curve and radar bright haloes around fresh craters the dense venusian atmosphere has a strong influence on cratering the estimated age of the surface of the area under study is from 0 5 to 1 0 109 years the estimated rate of resurfacing during this time interval is about 0 04 to 0 8 cm 106 years the lithosphere of venus seems to be sufficiently rigid to sustain craters of 100 140 km diameter and 0 8 2 5 km depth for about 108 years

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

limits on modes of lithospheric heat transport on venus from impact crater density we present a formalism by which the size frequency distribution of impact craters on venus may be used to estimate upper bounds on the mean global rates of volcanic resurfacing and lithospheric recycling on that planet over the past several hundred million years the principal assumptions are that an upper bound on the rate of crater production on venus may be estimated and that craters are volcanically obliterated only when flows completely cover their rims the impact crater density reported from venera 15 16 observations if valid for the entire venus surface then indicates a mean volcanic flux no greater than 2 km y corresponding to a maximum average rate of resurfacing of about 4 km b y the fraction of global heat loss due to such a rate of volcanic resurfacing is negligible for the lowest estimated crater retention age of the surface imaged by venera 15 16 if globally representative the rate of lithospheric recycling on venus does not exceed 1 5 km y corresponding to 25 of the global heat loss more likely estimates of the mean surface age limit the contribution to global heat loss of any lithospheric recycling to be less than 10 these results support the hypothesis that simple conduction dominates heat transport at lithospheric levels in the venus interior

impact craters of venus a continuation of the analysis of data from the venera 15 and 16 spacecraft additional studies of venusian impact craters have been made based on an analysis of venera 15 16 radar imagery and altimetry the crater population on venus has been subdivided into groups representing different morphological classes and types the craters display the size dependent variations in morphology which are well known from other planets assuming a crater production rate based on estimates by hartmann et al 1981 their areal density indicates an age for the total population of approximately 1 b y alternative estimates based on the assumption that the recent cratering rates on the earth and venus were similar would give a significantly lower age the areal and size frequency distribution of a number of circular features of unclear origin have also been analyzed and it is proposed that some of these features may be highly degraded and modified impact craters corresponding to a population approximately 3 b y in age a suggested model of the effect of the atmosphere on the crater diameter frequency curve indicates that cometary impacts played only a minor role in forming the contemporary venus environment a comparative study of craters in the area where the arecibo earth based radar and venera 15 16 images overlap indicates that the radar dark inner zones of the craters in the high incidence angle arecibo images correspond to the flat bottoms of the craters seen in the venera images

possible mantle origin of olivine around lunar impact basins detected by selene the composition structure and evolution of the moon s mantle is poorly constrained a global survey of the moon s surface using the spectral profiler onboard the lunar explorer selene kaguya identifies a number of exposures of olivine in concentric regions around lunar craters with a possible mantle origin

detection of hydroxyl bearing exposures of possible magmatic origin on the central peak of crater theophilus using chandrayaan 1 moon mineralogy mapper m3 data abstract high resolution spectral and spatial data analyses of crater theophilus revealed the presence of hydroxyl bearing exposures of possible magmatic origin on its central peak in association with olivine spinel and crystalline plagioclase bearing lithologies hydroxyl bearing lithologies at theophilus central peak are characterized primarily by a prominent absorption feature near 2800 nm the strength of which varies from 2 to 6 in some localized zones within the central peak the strong and sharp 2800 nm hydroxyl feature having localized occurrences on the central peak of crater theophilus is inconsistent with a surficial origin we suggest that the observed hydration at theophilus central peak could possibly be associated with a sub crustal magmatic source that was subsequently tapped and exposed by theophilus impact event

magellan initial analysis of venus surface modification initial magellan observations reveal a planet with high dielectric constant materials exposed preferentially in elevated regions with high slopes ejecta deposits extending up to 1000 kilometers to the west of several impact craters windblown deposits and features in areas where there are both obstacles and a source of particulate material and evidence for slow steady degradation by atmosphere surface interactions and mass movements

quantifying seismic vulnerability dynamical shear strain and liquefaction of the quaternary deposits in the doon valley near the main boundary thrust in the northwest himalaya india abstract erosion and deposition are two conjugate surface dynamical processes that affect differently to the soft soil site characteristics of quaternary deposits in the doon valley and at its northern topographic transition zone near the main boundary thrust mbt during an impending large magnitude earthquake what would be the seismic vulnerability and liquefaction susceptibility of the soft soil at both the regions we quantified seismic vulnerability index effective dynamical shear strain and the expected ground deformation in the valley soft soil through h v site characteristics using seismic ambient noise data at the in accessible topographic transition zone near the mbt site effects were studied using moderate and light magnitude earthquakes recorded by three broad band seismographs bbs results show unique dual peak mean resonant frequencies 1 11 and 1 38 hz and amplification factors 1 69 and 1 51 at the topographic transition zone which highlights a bimodal distribution of site effects where the top soil formation is influenced by erosion and deposition due to topographic slope instability apart from fluvial re working here relatively compact oldest doon gravel is present in the foothill terraces with the re worked fluvial deposition of the youngest doon gravel however in the valley and its terraces the soft soil formed under fluvial environ is relatively thick 10 to 2 and mean resonant frequency of 1 1 hz the spot resonant frequencies increases from 1 hz to more than 6 hz from the hft region to the mbt while the amplification factor decreases from 14 to 1 in general the valley soft soil is susceptible for liquefaction because the estimated dynamical shear strain is 15 25 millistrains under medium 2 2 m s 2 225 years and long 4 6 m s 2 2500 years term strong motion conditions which is much higher than the soil plasticity limit of ten millistrains that lead to liquefaction dynamical shear strain distribution with depth at eight boreholes in the valley indicate 20 m is the liquefaction potential depth where the pore pressure induced peak shear strain exceeds the threshold shear strain of 0 01 during the passage of seismic waves isolated locations in the valley like that at dharmawala h1 where all site parameters are very high and would be hazardously vulnerable to liquefaction however near the mbt the liquefaction possibility of soft soil is less but would experience ground deformation of more than 50 cm

great earthquakes seismicity gaps and potential for earthquake disaster along the himalaya plate boundary abstract analysis of the space time patterns of seismicity in the himalaya plate boundary has established the existence of three seismic gaps 1 1 the kashmir gap lying west of the 1905 kangra earthquake 2 2 the central gap situated between the 1905 kangra and the 1934 bihar earthquakes 3 3 the assam gap between the 1897 and 1950 assam earthquakes this study has shown that the above great earthquakes were preceded as well as followed by long periods 19 years of decreased levels of seismic activity in the epicentral regions remarkable decrease in the seismicity following the year 1970 has been observed in the western half of the central gap as well as in the assam gap local seismic investigation in the assam gap confirms this feature and the seismicity suggests the existence there of an asperity the local seismic investigations in garhwal himalaya have shown that the small earthquakes are confined to the upper 6 8 km of the crust and may have strike slip motions these earthquakes occur in a region where teleseismically recorded events were few

impact craters on venus initial analysis from magellan magellan radar images of 15 percent of the planet show 135 craters of probable impact origin craters more than 15 km across tend to contain central peaks multiple central peaks and peak rings many craters smaller than 15 km exhibit multiple floors or appear in clusters these phenomena are attributed to atmospheric breakup of incoming meteoroids additionally the atmosphere appears to have prevented the formation of primary impact craters smaller than about 3 km and produced a deficiency in the number of craters smaller than about 25 km across ejecta is found at greater distances than that predicted by simple ballistic emplacement and the distal ends of some ejecta deposits are lobate these characteristics may represent surface flows of material initially entrained in the atmosphere many craters are surrounded by zones of low radar albedo whose origin may have been deformation of the surface by the shock or pressure wave associated with the incoming meteoroid craters are absent from several large areas such as a 5 million square kilometer region around sappho patera where the most likely explanation for the dearth of craters is volcanic resurfacing there is apparently a spectrum of surface ages on venus ranging approximately from 0 to 800 million years and therefore venus must be a geologically active planet

the influence of mantle water and heterogeneity on the viscous relaxation of venus impact craters empirical flow laws for peridotite and diabase were used to model the viscous relaxation of large impact craters on venus the models were then compared to the depths of the three largest impact craters 60 km diameter measured by venera 15 16 radar altimetry the maximum crater retention times predicted by models that assumed 0 03 wt water in the upper mantle were inconsistent with the observed depths of these craters and a mean minimum age of 0 5 ga models that assumed an upper mantle water content of 0 003 wt were consistent with the observations and a maximum crater retention time of 1 0 ga this result was insensitive to up to 60 by volume diabase mixed into the upper mantle as inclusions at the several kilometer scale and to the presence of a basalt eclogite or melting transition at a depth of 100 km

apatites in lunar kreep basalts the missing link to understanding the h isotope systematics of the moon recent re analyses of lunar samples have undoubtedly measured indigenous water challenging the paradigm of a dry moon and arguing that some portions of the lunar interior are as wet as some regions of the earth s mantle and that water in both planetary bodies likely share a common origin mare basalts indirectly sample the lunar mantle and are affected by petrogenetic processes such as crystallization and degassing that can modify characteristics of indigenous water in primary mantle melts analyses of apatite in phosphorus rich kreep k ree rare earth elements p basalts may provide more reliable estimates for the water content of lunar magmas as some apatites likely crystallized before substantial degassing occurred in lunar kreep basalt sample 15386 apatite h 2 o content and h isotopic composition suggest that degassing occurred during apatite crystallization the lowest d value of 90 100 representing an upper limit for the isotopic composition of water in the parental magma interpretation of the data for kreep basalt 15386 suggests that this basalt is characterized by relatively elevated h 2 o contents and ci chondrite type d values similar to those proposed for other mare basalts and pyroclastic glasses on the other hand most of the apatites in lunar kreep basalt 72275 and lunar meteorite nwa 773 crystallized before degassing and h isotope fractionation and their d h ratios thus directly refl ect those of their source regions these apatites have an average d value of 130 50 suggesting the presence of a water reservoir in the moon characterized by moderate h 2 o contents and h isotopic composition similar to that of earth s interior these fi ndings imply that signifi cant amounts of water in the moon were inherited from the proto earth surviving the purported moon forming impact event

styles of volcanism on venus new arecibo high resolution radar data arecibo high resolution 1 5 to 2 km radar data of venus for the area extending from beta regio to western eisila regio provide strong evidence that the mountains in beta and eisila regiones and plains in and adjacent to guinevere planitia are of volcanic origin recognized styles of volcanism include large volcanic edifices on the beta and eisila rises related to regional structural trends plains with multiple source vents and a mottled appearance due to the ponding of volcanic flows and plains with bright features surrounded by extensive quasi circular radar dark halos the high density of volcanic vents in the plains suggests that heat loss by abundant and widely distributed plains volcanism may be more significant than previously recognized the low density of impact craters greater than 15 km in diameter in this region compared to the average density for the higher northern latitudes suggests that the plains have a younger age

mineralogy of the lunar crust results from clementine received 1997 december 5 accepted in revised form 1998 september 15 abstract the central peaks of 109 impact craters across the moon are examined with clementine ultraviolet visible uvvis camera multispectral data the craters range in diameter from 40 to 180 km and are believed to have exhumed material from 5 30 km beneath the surface to form the peaks including both upper and lower crustal rocks depending on whether craters have impacted into highlands or basins representative five color spectra from spectrally and spatially distinct areas within the peaks are classified using spectral parameters including key ratio which is related to mafic mineral abundance and spectral curvature linked to absorption band shape which distinguishes between low and high ca pyroxene and olivine the spectral parameters are correlated to mineralogical abundances related in turn to highland plutonic rock compositions the derived rock compositions for the various central peaks are presented in a global map from these results it is evident that the lunar crust is compositionally diverse both globally and at local 100 m scales found within individual sets of central peaks although the central peaks compositions imply a crust that is generally consistent with previous models of crustal structure they also indicate a more anorthositic crust than generally assumed with a bulk plagioclase content of 8 1 evolving from pure anorthosite near the surface towards more mafic low ca pyroxene rich compositions with depth comparable to anorthositic norite evidence for mafic plutons occurs in both highlands and basins and represent all mafic highland rock types however the lower crust is more compositionally diverse than the highlands with both a greater range of rock types and more diversity within individual sets of central peaks

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

measuring moonlight an overview of the spatial properties lunar coverage selenolocation and related level 1b products of the moon mineralogy mapper 1 the moon mineralogy mapper m3 a high resolution high precision imaging spectrometer flew on board india s chandrayaan 1 mission from october 2008 through august 2009 this paper describes some of the spatial sampling aspects of the instrument the planned mission and the mission as flown we also outline the content and context of the resulting level 1b spatial products that form part of the m3 archive while designed and planned to operate for 2 years in a 100 km lunar orbit m3 was able to meet its lunar coverage requirements despite the shortened mission an increase of the orbit altitude to 200 km and several relevant problems with spacecraft attitude timing and ephemeris the unexpected spacecraft issues required us to invent a novel two step approach for selenolocation leveraging newly available lunar reconnaissance orbiter lunar orbiter laser altimeter lola topography and an improved spacecraft ephemeris we have created a method that permits us to bootstrap spacecraft attitude estimates from the image data themselves this process performs a nonlinear optimization to honor a set of data derived image to image tie points and image to lola control points error analysis of the final results suggests we have converged to a selenolocation result that has image to image root mean square rms errors less than 200 m and image to lola rms errors less than 450 m despite using data derived spacecraft attitude results the level 1b products include the lunar coordinates resulting from this inversion process and 10 relevant observational geometry parameters that fully characterize the ray tracing geometry on a pixel by pixel basis

remote detection of magmatic water in bullialdus crater on the moon the remote detection of surface water indigenous to the moon has proved difficult because of alternative sources such as the solar wind spectroscopic observations of hydroxyl bearing materials in bullialdus crater by the chandrayaan 1 spacecraft are consistent with indigenous magmatic water that was excavated by impact from the lunar interior

site specific microzonation study in delhi metropolitan city by 2 d modelling of sh and p sv waves delhi the capital of india lies on a severe earthquake hazard threat not only from local earthquakes but also from himalayan events just 200 250 km apart the seismic ground motion in a part of delhi city is computed with a hybrid technique based on the modal summation and the finite difference scheme for site specific strong ground motion modelling complete realistic sh and e5 e5 sv wave seismograms are computed along two geological cross sections 1 north south from inter state bus terminal isbt to sewanagar and 2 east west from tilak bridge to punjabi bagh two real earthquake sources of july 15 1720 mmi ix m 7 4 and august 27 1960 m 6 0 have been used in modelling the response spectra ratio rsr i e the response spectra computed from the signals synthesized along the laterally varying section and normalized by the response spectra computed from the corresponding signals synthesized for the bedrock reference regional model have been determined as expected the sedimentary cover causes an increase of the signal amplitude particularly in the radial and transverse components to further check the site effects we reversed the source location to the other side of the cross section and recomputed the site amplifications there are only a few sites where a large amplification is invariant with respect to the two source locations considered the rsr ranges between 5 to 10 in the frequency range from 2 8 to 3 7 hz for the radial and transverse components of motion along the ns cross section along the ew cross section rsr varies between 3 5 to 7 5 in the frequency range from 3 5 to 4 1 hz the amplification of the vertical component is considerable at high frequency 4 hz whereas it is negligible in lower frequency range

the evolution of the lunar nectaris multiring basin abstract nectaris is an 820 km diameter multiring impact basin located on the near side of the moon the transient cavity is estimated to have been less than 90 km in depth and materials were excavated from a depth of less than 30 km about 2 km thickness of impact melt is believed to line the cavity center the impact event probably took place at about 3 98 0 03 109 years ago nectaris ejecta forms a substantial proportion of the surface materials at the apollo 16 site inter ring plains deposits were deposited after the formation of the nectaris basin the most persuasive origin for the smooth plains is one of extrusives overlain by a thin veneer of ejecta basaltic fragments within apollo 16 samples are believed to have been largely derived from nectaris a titanium rich apollo 16 mare basalt fragment has an age of 3 79 0 05 109 years but although some relatively titanium enriched basalts occur in southern nectaris titanium rich basalts are nowhere seen at the surface of the mare the earliest recognized eruptives appear to be low titanium perhaps vlt basalts found as pyroclastic materials on daguerre and in the gaudibert region the majority of the surface basalts are of intermediate composition possibly similar to apollo 12 basalts and have an age of approximately 3 6 109 years the basalt fill is estimated to have a minimum thickness of 3 km flood style eruptions appear to have been the main form of extrusion mare ridges exhibit a strong north south preferential alignment and appear to postdate basalt emplacement the lack of basin related graben in nectaris is consistent with a thick lithosphere the basin ring structure is best preserved in the southwest and least preserved in the northeast this is believed to result from horizontal variations in the crust and lithosphere thicknesses and from the influence of the preexisting fecunditatis and tranquillitatis basins the ring structure is best preserved where the lithosphere was thickest floor fractured craters within nectaris are intimately associated with the basalt fill both in terms of age and location theophilus ejecta small craters and tycho rays combined with subsidence and mare ridge development were the only modifying influences on nectaris since the termination of basalt eruptions

compositional diversity at theophilus crater understanding the geological context of mg spinel bearing central peaks 1 analysis of high resolution moon mineralogy mapper m3 data reveals the presence of a prominent mg spinel rich lithology in the central peaks of theophilus crater on the lunar nearside other peak associated lithologies are comprised of plagioclase olivine and pyroxene bearing materials a consistent spatial association of mg spinel with mafic free anorthosite is recognized documentation of theophilus central peaks brings the global inventory of mg spinel rich lithology to two widely separated occurrences namely theophilus on the lunar nearside and moscoviense basin on the farside the theophilus crater target region lies on one of the inner rings of the nectaris basin indicating that the mg spinel bearing lithology source was deep in the lunar crust

geology and distribution of impact craters on venus what are they telling us magellan has revealed an ensemble of impact craters on venus that is unique in many important ways we have compiled a data base describing the 842 craters on 89 of venus surface mapped through orbit 2578 the craters range in diameter from 1 5 to 280 km we have studied the distribution size density morphology geology and associated surface properties of these craters both in the aggregate and for some craters in greater detail we find that 1 the spatial distribution of craters is highly uniform 2 the size density distribution of large craters diameters 35 km is similar to the young crater populations on other terrestrial planets but at a much lower density that indicates an average age of only about 0 5 ga based on the estimated population of venus crossing asteroids 3 unlike the case on other planets the density of small craters diameters 35 km declines rapidly with decreasing diameters because of atmospheric filtering 4 the spectrum of crater modification differs greatly from that on other planets 62 of all craters are pristine only 4 are embayed by lavas and the remainder are affected by tectonism but none are severely and progressively depleted as extrapolated from the size density distribution of larger craters 5 large craters have a progression of morphologies generally similar to those on other planets but small craters are typically irregular or multiple rather than bowl shaped 6 diffuse radar bright or dark features surround some craters and 367 similar diffuse splotches with no central crater are observed and 7 other crater features unique to venus include radar bright or dark parabolic arcs opening westward and extensive outflows originating in crater ejecta the first three of these observations are entirely unexpected we interpret them as indicating that the planet s cratering record was erased by a global resurfacing event or events the latest ending about 0 5 ga after which volcanic activity declined but did not cease entirely since the last resurfacing event a maximum of 10 of the planet has been resurfaced and only about 4 of the craters have been obliterated convective thermal evolution models support this interpretation arkani hamed and toksoz 1984 observations 3 7 confirm quantitatively the expectation that the dense atmosphere of venus has strongly affected the production of craters large impactors have been relatively unaffected intermediate sized ones have been fragmented and have produced overlapping or multiple craters a narrow size range has produced shock induced splotches but no craters and the smallest bodies have had no observable effect on the surface the number of craters eliminated by the atmospheric filter is enormous about 98 of the craters between 2 and 35 km in diameter that magellan might have observed on a hypothetical airless venus unique crater related features such as parabolas and outflow deposits demonstrate the roles of venus high atmospheric density and temperature in modifying the crater formation process finally heavily fractured craters and lava embayed craters are found to have higher than average densities along the major fracture belts and rifted uplands connecting aphrodite terra and atla beta themis and phoebe regiones these craters thus provide physical evidence for recent volcanic and tectonic activity at a low level

estimation of site effects in bucharest caused by the may 30 31 1990 vrancea seismic events the vrancea region seismicity characterized by focal depths larger than 60 km and major events with magnitudes m w 6 9 is responsible for the most destructive effects experienced in the romanian territory and may seriously affect high risk construction located on a wide area from central to eastern europe this seismogenic volume must be taken into account both for seismic hazard analysis at the regional level southeastern europe and national level romania and bulgaria as well as for microzonation studies of the highly populated cities located in the range of influence of this source since about four destructive earthquakes occur every century in vrancea the microzonation of bucharest the main city exposed to the potential damages due to these strong intermediate depth shocks represents an essential step towards the mitigation of the local seismic risk two main approaches can be considered for the evaluation of the local seismic hazard a collection and extended use for engineering purposes of the recorded strong motion data and b advanced modelling techniques that allow us the computation of a realistic seismic input which can compensate for the lack of strong motion records actually available only for a few events that occurred in the last 20 30 years

viscous relaxation of impact crater relief on venus constraints on crustal thickness and thermal gradient because of the high surface temperature on venus and the strong temperature dependence of strain rate in silicates solid state creep may be an important mechanism for the reduction of topographic relief on that planet venera 15 16 radar altimetric profiles of impact craters 30 140 km in diameter however indicate crater depths of several hundred meters suggesting that substantial relaxation has not occurred for these features on the basis of models for the viscous relaxation of impact crater topography we derive constraints on the thickness of the crust and the mean lithospheric thermal gradient beneath the craters from the mean and variance of observed crater depth as a function of crater diameter on venus and from estimates of the initial depths of fresh impact craters on venus obtained by scaling from lunar observations we formulate a statistical test for the maximum amount of viscous relaxation that is consistent with the observations at a specified confidence level we develop a general formulation for gravity driven flow in a linearly viscous fluid incorporating the densities and temperature dependent effective viscosities of distinct crust and mantle layers the statistical comparison of predicted and observed depths yields linked upper limits to crustal thickness h and thermal gradient dt dz since dt dz can be estimated from global heat loss arguments or thermal models an upper bound to h may be derived the preserved relief of the largest craters constrain h to be less than or equal to 10 20 km because the craters with measured depths appear to be representative of a larger population of impact structures in terms of regional elevation geological unit and degree of preservation of morphological detail extrapolation of this result to lowlands and rolling plains regions on a global basis is not unreasonable such an extrapolation together with isostatic considerations yields an upper limit to the crustal volume of venus of 1010 km3 this value is an order of magnitude less than the time integrated volume of crust produced on earth and implies either that the average rate of crustal generation has been much smaller on venus than on earth or that some form of crustal recycling has occurred on venus

water in lunar anorthosites and evidence for a wet early moon water has been detected on the lunar surface and attributed to delivery by impacts and the solar wind to a dry early moon spectroscopic detections of water in lunar anorthosites from the apollo collection suggest that a significant amount of water is indigenous to the moon

accumulation of sedimentary debris in the south polar region of mars and implications for climate history abstract stratigraphic units of the south polar region of mars were mapped relative chronology determined and detailed modeling of the observed crater populations was used to set absolute constraints on the age of emplacement of materials significant secular variation in the net debris accumulation rate over history is evident an episode of enhanced crater obliteration at about 3 7 ga ago lasting a few hundred ma is inferred for south polar cratered terrains a similar peak in low latitude obliteration rates suggests that the event may have been global in scale whether the debris is volcanic or aeolian in origin the event suggests a possible enhancement in atmospheric density at the time modeling results imply that cratered terrains poleward of 65 south latitude have subsequently experienced steady state net accumulation of material at a rate of about 0 1 km ga while equatorial cratered terrains have been retained in relatively pristine form fifteen craters of impact origin were discovered on the south polar layered terrain formerly thought to be almost devoid of craters their presence implies that the surface is at least a few 100 ma old and that the net accumulation rate is no more than 10 km ga if layer formation is modulated by periodic climatic effects either the period of oscillation is a few ma or longer or the layer deposition mechanism ceased operating at least several 100 ma ago

computation of ground motion amplification scenario in nct delhi for earthquake engineering purposes and seismic microzonation this paper presents a scenario for the spatial variation of the fundamental frequency of the sediment deposits above the basement and the corresponding amplification as well as the average spectral amplification in different frequency bandwidths for the national capital territory delhi the capital of india the exposed central quartzite ridge and the yamuna river channel are responsible for very large spatial variations of the fundamental frequency in the eastern part of the national capital territory delhi at 20 of the considered sites a good match is obtained between the fundamental frequency computed numerically using available s wave velocities to a certain depth and their extrapolation and that obtained experimentally the computed fundamental and dominant frequencies reveal that both medium rise 5 10 storey and high rise 10 storey buildings in the western part and medium rise buildings lying in the localities east of or very near to the yamuna river may suffer heavy to very heavy damage due to the occurrence of the double resonance phenomenon furthermore 1 2 storey buildings lying on the weathered exposed quartzite rock may also suffer heavy damage during local earthquakes because of the occurrence of double resonance the possible reasons behind the lack of earthquake damage to the qutab minar the tallest brick masonry minaret in the world over the last 800 years may be the nonoccurrence of double resonance and almost no amplification in the low frequency range there are two localities in the western part of the national capital territory delhi namely kanganheri chhawla and buradi wherein all sorts of buildings are highly vulnerable to earthquake damage for the closed chhatarpur basin and a semiclosed basin to its northeast formed due to exposed quartzite rock three dimensional 3d simulations are required to predict the characteristics of basin generated surface waves and their focusing effects in the chhatarpur basin the average spectral amplification map developed for the 0 10 hz bandwidth depicts a range of 2 25 4 82 in the national capital territory delhi and may be directly used to transfer the estimated seismic hazard at basement to the free surface

cordierite spinel troctolite a new magnesium rich lithology from the lunar highlands a clast of spinel troctolite containing 8 percent cordierite mg2al4si5o18 has been identified among the constituents of apollo 15 regolith breccia 15295 the cordierite and associated anorthite forsteritic olivine and pleonaste spinel represent a new mg rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate the cordierite forsterite pair in the assemblage is stable at a maximum pressure of 2 5 kilobars equivalent to a depth of 50 kilometers or 10 kilometers above the lunar crust mantle boundary the occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized the rarity of cordierite spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events such as the one that formed the adjacent imbrium basin

composition of the lunar highland crust from near infrared spectroscopy near infrared reflectance spectra of the lunar highlands are synthesized to obtain global information about the composition of the lunar near side crust immature exposed surfaces from small fresh craters mountains and massifs and large craters with central peaks are included in a survey of rock types across the lunar near side compositions recognized in these data include anorthosite noritic gabbric and troctolitic mineral assemblages three quarters of the areas studied that represent samples from the upper 1 2 km of lunar crust exhibit noritic compositions with different amounts of pyroxene and or brecciation alteration norites are ubiquitous across the near side and show no spatial clustering associated with any of the major basins in contrast to this noritic megaregolith of the upper crust material representing stratigraphically deeper zones 5 15 km of the lunar crust is dominated by gabbros anorthosites and troctolites with less than a quarter of the areas studied exhibiting a noritic composition the origin of the noritic megaregolith and its relation to deeper crustal material is thus somewhat of an enigma the current limited statistics for areas identified as anorthosites and troctolites are insufficient to derive global spatial distributions gabbroic areas however are notably concentrated in the western hemisphere although incomplete for a global assessment of crustal materials these data demonstrate that the lunar near side crust is clearly mineralogically heterogeneous both laterally and vertically and not well mixed below 1 2 km

himalayan seismic hazard the devastating earthquake in bhuj on 26 january 2001 highlighted the high earthquake risk in the indian region of gujarat in their perspective bilham et al warn that major earthquakes may be expected in another part of india the himalayan arc an analysis of historic earthquakes suggests that several major earthquakes are overdue in this region but that recent low activity has focused attention away from the himalayan arc projections from earlier earthquakes suggest that just one of the possibly overdue himalayan earthquakes may lead to 200 000 predictable fatalities

compositional diversity and geologic insights of the aristarchus crater from moon mineralogy mapper data 1 the moon mineralogy mapper m3 acquired high spatial and spectral resolution data of the aristarchus plateau with 140 m pixel in 85 spectral bands from 0 43 to 3 0 m the data were collected as radiance and converted to reflectance using the observational constraints and a solar spectrum scaled to the moon sun distance summary spectral parameters for the area of mafic silicate 1 and 2 m bands were calculated from the m3 data and used to map the distribution of key units that were then analyzed in detail with the spectral data this analysis focuses on five key compositional units in the region 1 the central peaks are shown to be strongly enriched in feldspar and are likely from the upper plagioclase rich crust of the moon 2 the impact melt is compositionally diverse with clear signatures of feldspathic crust olivine and glass 3 the crater walls and ejecta show a high degree of spatial heterogeneity and evidence for massive breccia blocks 4 olivine strongly concentrated on the rim wall and exterior of the southeastern quadrant of the crater is commonly associated the impact melt 5 there are at least two types of glass deposits observed pyroclastic glass and impact glass

an overview on the seismic zonation and microzonation studies in india abstract the present study presents a review on the progressive development of the seismic zonation map of india both from official agencies and also from independent individual studies the zonation map have been modified and updated regularly with the occurrence of major destructive earthquakes over the years in the indian subcontinent with the addition of new data this study discusses the criteria chosen for the progressive zonation and the major earthquakes that were responsible for retrospection of the earlier published maps the seismic zonation maps of india have also been prepared by various independent workers by adopting different approaches to achieve the purpose of the zonation despite the endeavors from various sources to provide a solution for the problem of earthquake hazards in india there were many limitations on the zonation map as it gives the picture at a regional scale mostly on the bedrock level without addressing the local site conditions but nevertheless the seismic zonation map gives basic guidelines for any region to know the hazard scenario and if any city or urban population is under threat from seismic point of view further site specific seismic microzonation may be carried out in the international scenario the global seismic hazard assessment program gshap in 1999 prepared a hazard map for world in terms of peak ground acceleration pga with a 10 probability of exceedance in 50 years but it turned out to be an underestimation of the hazard parameter when compared with the observed pga to tackle the problem of seismic hazards there was a need to have a detail study on the local site conditions in terms of its geological geophysical and geotechnical properties with the advent of better instrumentation and knowledge on the mechanics of earthquakes it was possible to identify zones of hazards at a local level and this gives rise to the study of seismic microzonation seismic microzonation work has been carried out in india in some of the strategic important mega cities and industrial build up that has the potential of being damaged from future earthquakes as has been shown in the past though the microzonation map is not the final output map as it can still be updated at later stage with more input data it does provide a more realistic picture on the site specific seismic hazard