regional variation of the ω upper bound magnitude of giii distribution in hindukush pamir himalaya and the adjacent regions a perspective on earthquake hazard the upper bound magnitude or maximum magnitude in 28 seismogenic source zones in the hindukush pamir himalaya and the adjacent regions have been computed with the help of a complete and homogeneous earthquake catalogue during the period 1900 2010 to estimate the earthquake hazards in the region the gumbel s third asymptotic distribution giii of extreme value method is used to estimate this parameter in this study a comparison of maximum magnitude obtained by giii distribution is carried out with kijko sellevoll method it is observed that the maximum earthquake magnitudes estimated by kijko sellevoll and giii methods are comparable to each other and the average of differences of their values is only 0 13 the results also estimate the most probable earthquake magnitude that can be expected in next 100 years m100 in all 28 seismogenic source zones an effort is made to make regression relations between and maximum magnitude estimated by kijko sellevoll method mmax ks and and maximum observed magnitude mmaxobs the estimated values exceeded the value of 7 00 in 15 and 8 00 in 5 of the 28 seismogenic source zones the geographical distribution of and m100 in 28 seismogenic source zones of the study region is visualized to analyze the localized seismicity parameters it is observed that earthquake hazard level varies spatially from one zone to another which suggests that examined region have high crustal heterogeneity and seismotectonic complexity

observations of time dependent bedform transformation in combined wave current flows although combined wave current flows in the nearshore coastal zone are common there are few observations of bedform response and inherent geometric scaling in combined flows our effort presents observations of bedform dynamics that were strongly influenced by waves currents and combined wave current flow at two sampling locations separated by 60 m in the cross shore observations were collected in 2014 at the sand engine mega nourishment on the delfland coast of the netherlands the bedforms had wavelengths ranging from 14 cm to over 2 m and transformed shape and orientation within at times as little as 20 min and up to 6 hr the dynamic set of observations was used to evaluate a fully unsteady description of changes in the bedform growth with the sediment transport continuity equation exner equation relating changes in bedform volume to bedload sediment transport analysis shows that bedform volume was a function of the integrated transport rate over the bedform development time period the bedform development time period time lag of bedform growth adjustment is important for estimating changes in bedform volume results show that this continuity principle held for wave current and combined wave current generated bedforms

assessment of earthquake hazard in the tokyo area japan abstract the probability of occurrence of an inland earthquake originating beneath the tokyo area is evaluated for a 10 year period from 1991 on the basis of an earthquake catalogue containing some 40 earthquakes which caused some damage to edo now tokyo over a period of 400 years the parameters of the weibull and lognormal probability distributions applied to recurrence interval statistics are estimated with these parameters it is concluded that an earthquake directly beneath the capital the magnitude of which is equal to or greater than 6 0 occurs with a probability of 0 40 for the period in question when the magnitude threshold is assumed as 6 4 and 7 0 the probabilities become 0 17 and 0 049 respectively these probability evaluations are extended to those for the seismic intensity at typical sites in the area although no accurate evaluation is possible because the exact focal depths of historical earthquakes are not known on the assumption that these earthquakes occur near the upper surface of the down going philippine sea plate however a typical depth of 30 km or so is suggested should an earthquake having a mean magnitude of 6 4 say and at a mean location of past earthquakes occur the probability of seismic intensity at typical sites in the capital area exceeding 5 on the japan meteorological agency jma scale would amount to 0 17 the possibility of having a highly damaging earthquake of intensity 6 on the jma scale also cannot be ruled out judging from earthquake disasters in the past although the probability does become lower to summarize it may be said that the probability of japan s capital area being hit by a damaging earthquake in the foreseeable future is not particularly low

a probabilistic assessment of earthquake hazard parameters in nw himalaya and the adjoining regions the maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of nw himalaya and the adjoining regions for this purpose we have prepared a reliable homogeneous and complete earthquake catalogue during the period 1500 2010 the technique used here allows the data to contain either historical or instrumental era or even a combination of the both in this study the earthquake hazard parameters which include maximum regional magnitude mmax mean seismic activity rate the parameter b or b log e of gutenberg richter g r frequency magnitude relationship the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900 2010 the uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters the earthquake hazard in the whole nw himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level tectonics and focal mechanism the annual probability of exceedance of earthquake activity rate of certain magnitude is also calculated for all seismogenic source zones the obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters it is observed that seismic hazard level is high in quetta kirthar sulaiman region in pakistan hindukush pamir himalaya region and uttarkashi chamoli region in himalayan frontal thrust belt the source zones that are expected to have maximum regional magnitude mmax of more than 8 0 are quetta southern pamir caucasus and kashmir himanchal pradesh which have experienced such magnitude of earthquakes in the past it is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity

seismicity patterns in the himalayan plate boundary and identification of the areas of high seismic potential abstract space time distribution of earthquakes along the himalayan plate boundary has been investigated with a view to discerning fluctuations in seismicity rates associated with great earthquakes the possibilities of epicentre migration and gaps in seismic activity data from 1800 to 1976 were considered this study shows that all great earthquakes m 8 0 were preceded by seismically quiescent periods of at least 19 years furthermore earthquake quiescence has also been recognised to follow the great earthquakes three possible trends of migration of epicentres of great earthquakes have been recognised 1 1 the first trend starts from the 1905 kangra earthquake the epicentres of subsequent earthquakes migrating eastwards along the plate boundary 2 2 the second trend of migration starts from the great nepal earthquake of 1833 associated with eastward migration 3 3 the third trend commences from the great assam earthquake of 1897 and shows a westward migration of earthquake epicentres the middle section of the himalayan convergent plate boundary 80 e to 90 e in general displays a relatively low level of seismicity as compared to the adjacent sections a remarkable decrease in seismicity following the year 1970 has been observed along a section of the himalaya which lies to the east of the rupture zone of the great 1905 kangra earthquake since 1970 the seismicity rate has also dropped in the region lying in between the rupture zones of the great assam earthquakes of 1897 and 1950 as has earlier been reported by khattri and wyss 1978 such decreases in the level of seismicity along active plate boundaries have been demonstrated to be indicative of building up of stresses leading to future great earthquakes mogi 1969 mccann et al 1979

probabilistic assessment of earthquake hazards in the north east indian peninsula and hindukush regions the himalayan region is one of the most seismic prone areas of the world the north east ne indian peninsula and the hindukush regions mark the zone of collision of the indian and eurasian plates the probability of the occurrence of great earthquakes with magnitude greater than 7 0 during a specified interval of time has been estimated on the basis of four probabilistic models namely weibull gamma lognormal and exponential for the ne indian peninsula and hindukush regions the model parameters have been estimated by the method of maximum likelihood estimates mle and the method of moments mom the cumulative probability is estimated for a period of 40 years from 1964 and is ranging between 0 881 to 0 995 by the year 1995 using all four models for the ne indian peninsula the conditional probability is also estimated and it is concluded that the ne indian peninsula would expect a great earthquake at any time in the remaining years of the present century for the hindukush region the cumulative probability has already crossed its highest value but no earthquake of magnitude greater than 7 0 has occurred after 1974 in this area it may attribute to the occurrence of frequent shocks of moderate size as seventeen earthquakes of magnitude greater than 6 0 including four greater than 6 4 have been reported until 1994 from this region

probabilistic assessment of tsunami recurrence in the indian ocean the indian ocean is one of the most tsunamigenic regions of the world and recently experienced a mega tsunami in the sumatra region on 26 december 2004 m w 9 2 earthquake with tsunami intensity i soloviev imamura intensity scale equal to 4 5 causing heavy destruction of lives and property in the indian ocean rim countries in this study probabilities of occurrences of large tsunamis with tsunami intensities i 2 0 and i 3 0 average wave heights h 2 83 m and h 5 66 m respectively during a specified time interval were calculated using three stochastic models namely weibull gamma and lognormal tsunami recurrence was calculated for the whole indian ocean and the special case of the andaman sumatra java asj region excluding the 1945 makran event from the main data set for this purpose a reliable homogeneous and complete tsunami catalogue with i 2 0 during the period 1797 2006 was used the tsunami hazard parameters were estimated using the method of maximum likelihood the logarithm of likelihood function ln l was estimated and used to test the suitability of models in the examined region the weibull model was observed to be the most suitable model to estimate tsunami recurrence in the region the sample mean intervals of occurrences of tsunamis with intensity i 2 0 and i 3 0 were calculated for the observed data as well as for the weibull gamma and lognormal models the estimated cumulative and conditional probabilities in the whole indian ocean region show recurrence periods of about 27 30 years 2033 2036 and 35 36 years 2039 2040 for tsunami intensities i 2 0 and i 3 0 respectively while it is about 31 35 years 2037 2041 and 41 42 years 2045 2046 for a tsunami of intensity i 2 0 and i 3 0 respectively in the asj region a high probability 0 9 of occurrence of large tsunamis with i 2 0 in the next 30 40 years in the indian ocean region was revealed

initiation of bed forms on a flat sand bed the results of a series of 47 bed development experiments are combined with appropriate experimental results of other authors the generation of initial bed waves termed sand wavelets on a plane sand bed is found to be instigated by the occurrence of a random pileup of sediment this pileup subsequently growing as further sediment is trapped by the pileup when the height of the pileup approaches the bed roughness height further pileups are generated at preferred spacings downstream the wavelength l of the sand wavelets so generated is relatively insensitive to the applied bed shear stress and primarily a function of the size d g of the sediment this wavelength can be described by the empirical formula l dg r c0 2 10 2 5 from a theoretical viewpoint this wavelength is approximately described by a reassessment of the flow system instability analyses of richards both ripples and dunes are found to develop from the sand wavelets

solar noble gases in the unique chondritic breccia allan hills 85085 the chemical composition of the chondritic breccia allan hills 85085 does not match that of any known group of chondrites in addition this meteorite contains extremely fine grained fragments and small chondrule like inclusions we investigated the noble gas isotopic abundances in bulk samples in a fine grained silicate fraction and in a coarse grained fraction containing the metal phase solar gases are present in the fine grained silicates and indicate processing of the alh85085 material in an asteroidal regolith he and ne are enriched in a 40 m grain size fraction indicating surface implantation of solar particles the solar noble gas component is characterized by an elemental abundance pattern and isotopic ratios typical for lunar and asteroidal regolith material 4he 36ar 469 20ne 36ar 4 2 4he 3he 2300 600 20ne 22ne 12 5 0 4 the major noble gas component in the bulk and coarse grained fractions are planetary type trapped gases abundances and isotopic composition are similar to those in type 2 and 3 chondrites in some respects alh85085 resembles another unique chondrite kakangari but it differs in its feni content that is almost twice as high as in kakangari and in other characteristics both the cosmic ray exposure age and the k 40ar gas retention age are relatively low the travel time of alh85085 as a small object in space was 1 7 0 8ma and a fraction of40ar was lost as indicated by the40k 40ar retention age of 2900 300ma

alh85085 a unique volatile poor carbonaceous chondrite with possible implications for nebular fractionation processes abstract allan hills 85085 is a unique chondrite with affinities to the al rais renazzo clan of carbonaceous chondrites its constituents are less than 50 m in mean size chondrules and microchondrules of all textures are present nonporphyritic chondrules are unusually abundant the mean compositions of porphyritic nonporphyritic and barred olivine chondrules resemble those in ordinary chondrites except that they are depleted in volatile elements ca al rich inclusions are abundant and largely free of nebular alteration they comprise types similar to those in cm and co chondrites as well as unique types calcium dialuminate occurs in several inclusions metal silicate and sulfide compositions are close to those in cm co chondrites and al rais and renazzo c1 chondrite clasts and metal rich reduced clasts are present but opaque matrix is absent siderophile abundances in alh85085 are extremely high e g fe si 1 7 solar and volatiles are depleted e g na si 0 25 solar s si 0 03 solar nonvolatile lithophile abundances are similar to those in al rais renazzo and cm and co chondrites alh85085 agglomerated when temperatures in the nebula were near 1000 k in the same region where renazzo al rais and the ci chondrites formed agglomeration of high temperature material may thus be a mechanism by which the fractionation of refractory lithophiles occurred in the nebula chondrule formation must have occurred at high temperatures when clumps of precursors were small after agglomeration alh85085 was annealed and lightly shocked c1 and other clasts were subsequently incorporated during late stage brecciation

a new ground motion prediction model for northeastern india nei crustal earthquakes in this study a stochastic point source model is used to develop a ground motion prediction model for northeastern india nei crustal earthquakes calibrated using region specific source path and site parameters the nei strong ground motion database is too limited to derive an empirical ground motion prediction model valid for all magnitudes and distances in the present study we simulated 30 000 ground motions to develop the horizontal ground motion prediction model for nei these simulations are for 1000 earthquakes of moment magnitudes m w 4 8 5 and epicentral distances of 1 300 km in simulating ground motions quality factor stress drop and kappa derived from available nei strong motion records have been used the model has been validated by comparing it with the available but sparse database of recorded events the best fit between the model and observed strong ground motion records indicate that the new model is consistent with the available data and can be used in seismic hazard analyses until more data are collected and the model is improved

temporal and spatial evolution of wave induced ripple geometry regular versus irregular ripples concurrent observations of inner shelf near bed hydrodynamics and acoustic imagery of the seabed are used to relate wave induced ripple geometry wavelength and orientation to near bed directional wave velocities the observations were collected on the continental shelf of the south atlantic bight at water depths of 9 5 and 30 m off the coasts of south carolina median size 177 m and georgia 388 m respectively 2 d spectral analysis techniques are performed on the imagery to automate detection of ripple wavelength orientation and irregularity our analysis shows that ripple irregularity is a time dependent process dependent on magnitude direction and duration of wave forcing during energetic events ripple geometry changes rapidly and the ripples align with the main wave direction during periods of low energy close to the critical conditions for initiation of sediment motion ripple evolution occurs at a much slower rate often leading to irregularities such as terminations and bifurcations along the ripple crest under constantly changing wave direction the rippled bed becomes highly disorganized six types of ripples are defined based on newly developed irregularity parameters linear bifurcating linear linear bifurcating bifurcating and cross irregular and disorganized beds ripple irregularity depends on the time history of the bed ripples remain irregular until their wavelength and orientation attain a nearly equilibrium geometry the observations collected provide significant information on the response of the seabed to wave forcing and identify processes that should be reproduced by any time dependent ripple prediction model ripple irregularity can only be predicted using such time dependent models

probabilistic models for forecasting earthquakes in the northeast region of india northeast india and its adjoining areas are characterized by very high seismic activity according to the indian seismic code the region falls under seismic zone v which represents the highest seismic hazard level in the country this region has experienced a number of great earthquakes such as the assam 1950 and shillong 1897 earthquakes that caused huge devastation in the entire northeast and adjacent areas by flooding landslides liquefaction and damage to roads and buildings in this study an attempt has been made to find the probability of occurrence of a major earthquake m w 6 in this region using an updated earthquake catalog collected from different sources thereafter dividing the catalog into six different seismic regions based on different tectonic features and seismogenic factors the probability of occurrences was estimated using three models the lognormal weibull and gamma distributions we calculated the logarithmic probability of the likelihood function ln l for all six regions and the entire northeast for all three stochastic models a higher value of ln l suggests a better model and a lower value shows a worse model the results show different model suits for different seismic zones but the majority follows lognormal which is better for forecasting magnitude size according to the results weibull shows the highest conditional probabilities among the three models for small as well as large elapsed time t and time intervals t whereas the lognormal model shows the lowest and the gamma model shows intermediate probabilities only for elapsed time t 0 the lognormal model shows the highest conditional probabilities among the three models at a smaller time interval t 3 15 yrs the opposite result is observed at larger time intervals t 15 25 yrs which show the highest probabilities for the weibull model however based on this study the indoburma range and eastern himalaya show a high probability of occurrence in the 5 yr period 2012 2017 with 90 probability

a finite depth wind wave model part i model description abstract a parametric windsea model for arbitrary water depths is presented the model is derived from a conservation of energy flux formulation and includes shoaling refraction dissipation by bottom friction as well as finite depth modifications of the atmospheric input and nonlinear wave wave interaction source terms the importance of dissipation due to a rough ocean floor on the migration of the spectral peak frequency is discussed and compared with that caused by nonlinear energy transfer numerical simulations are used to systematically examine wave growth and the development of the spectral peak in a depth limited ocean two idealized situations of wave growth and propagation are considered to further understand the influence of bottom friction on the spectral dynamics the first case studies the characteristics of fetch limited wave growth in a steady uniform wind as function of depth and bottom roughness the second case examines the role of bottom dissipation on a fully developed deep water

geometry prediction for wave generated bedforms published data on wave generated bedform geometry from field and laboratory measurements are re evaluated in terms of relative fluid orbit diameter at the bed and a wave period parameter d 8t2 laboratory bedform data shows a strong dependence on these parameters however for very small values of the period parameter typically field data there is evidence that bedform length depends only on sediment grain size the disappearance of sediment bedforms at high fluid velocities apparently occurs through a decrease in bedform height improved methods for the prediction of bedform geometry under waves are provided in graphical form and computer code

seismic characteristics and seismic hazard assessment source region of the 2015 nepal earthquake mw 7 8 in central himalaya seismicity and seismic characteristics like b value fractal dimension energy release and recurrence period are assessed for the region 80 e 89 e and 26 n 31 n which includes the 2015 large nepal earthquake mw 7 8 in central himalaya the international seismological centre isc catalogue of earthquakes with mb 3 8 for the period august 1964 january 2013 are used the b values are estimated using the maximum likelihood and least square methods the fractal dimension is estimated using the correlation integral method the events are also used for estimating radiated energy in the region the probability of occurrence of moderate earthquakes mb 5 0 using isc data and mw 6 0 using usgs data for the period 1964 2015 during a specified interval of time is estimated on the basis of three probabilistic models namely weibull gamma and lognormal the model parameters are estimated by the maximum likelihood estimates it is found that there is a 99 probability for occurrence of at least one earthquake mb 5 0 in this region in a time window of 2 3 years from the year 2013 and in 20 30 years for an earthquake mw 6 0 from the year 2015 the b value maps identified variable stressed zones and the fractal dimension maps fractal characteristics of the active fault zones the energy release map identified the zones of higher and lower energy release the percent probability maps prepared using the poisson distribution identify the zones of higher and lower probability earthquakes and thus indicate the areas of future probable earthquakes

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

paired renazzo type cr carbonaceous chondrites from the sahara ten chondrites with chemical and mineralogical similarities to the carbonaceous chondrite renazzo were recovered at two locations of the sahara acfer 059 087 097 114 139 186 187 209 270 and el djouf 001 although the el djouf location is more than 500 km away from the acfer location all samples appear to result from a single fall based on chemical and petrographic similarities and supported by light element stable isotope geochemistry noble gas record and similar 26al contents the acfer el djouf meteorite is classified as a cr renazzo type carbonaceous chondrite this group presently comprises three non antarctic members al rais renazzo acfer el djouf and five antarctic meteorites the major lithological components of the acfer el djouf meteorite are large chondrules up to 1 cm in size mean diameter 1 0 0 6 mm chondrule and mineral fragments ca al rich inclusions feni metal about 8 10 vol and dark inclusions embedded in a fine grained fragment bearing groundmass mineral compositions of the ten acfer el djouf samples are similar to those of other cr chondrites most of the ca al rich inclusions are below 300 m in size and rich in melilite and spinel in some cais the rare phase caal4o7 is dominant fo rich cr bearing olivine fa0 4 and enstatite fs0 4 are the major phases of the chondrite the meteorite is mildly shocked with a shock stage of s2 indicating a peak shock pressure of 5 10 gpa for the bulk meteorite the oxygen isotopic compositions and carbon and nitrogen stable isotope geochemistry of the acfer el djouf samples are very similar to those of the other cr type chondrites the major element composition of the acfer el djouf meteorite is indistinguishable from cr chondrites when compared to renazzo the acfer el djouf samples however have systematically lower contents of the moderately volatile elements zn ga as au sb and se and the highly volatile elements br c and n this is thought to reflect primary differences between renazzo and the acfer el djouf meteorite

the nature and origin of type b1 and b2 caal rich inclusions in the allende meteorite abstract the type b ca al rich inclusions in the allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned b1 subtype to the unzoned b2 subtype these subtypes differ in i structure texture grain size and shape ii mineralogical proportions and compositions iii accessory mineralogy iv relative abundance of spinel framboids v rim layering vi major element chemistry and vii degree of secondary alteration these differences together with observations on the crystallization of synthetic melts suggest that the b1 inclusions crystallised relatively rapidly from molten parental material while b2 types crystallised relatively slowly close to the solidus from material that had not been completely melted the same data are used to construct an evaporative residue model for the origin of the parental type b materials in the model dust in the protosolar nebula was heated with removal of more volatile elements leaving completely melted type b1 residues at the highest temperatures and incompletely melted less highly evaporated type b2 residues at lower temperatures

chemical compositions of refractory inclusions in the murchison c2 chondrite abstract samples from ten refractory inclusions in murchison some of which are splits of inclusions whose mineralogical and petrographic characteristics are known have been analysed for thirty six elements by neutron activation six inclusions have group ii or group iii patterns or variants of such patterns two inclusions bb 5 and much 1 have large negative yb anomalies unaccompanied by correspondingly large negative eu anomalies it is possible that the latter condensed originally with group iii patterns and preferentially took up eu in later exchange processes under reducing conditions one inclusion sh 2 has heavy ree enrichment factors that increase with the refractoriness of the ree indicating the presence of an extremely high temperature or ultrarefractory ree condensate but it also has a heavy ree light ree ratio that indicates mixing of that component with a lower temperature ree condensate the frequency of highly fractionated ree patterns and absence of group i patterns suggest that refractory inclusions in murchison stopped equilibrating with the nebular gas at higher temperatures than most allende coarse grained inclusions the lower ir os and ru re ratios of some murchison inclusions compared to those of allende coarse grained inclusions indicate that condensate alloys that contributed noble metals to the former also stopped equilibrating with the nebular gas at higher temperatures than those that contributed noble metals to the latter murchison inclusions tend to be lower in non refractory elements than allende coarse grained inclusions suggesting that on average the former underwent less severe secondary alteration than the latter

correlated morphological chemical and isotopic characteristics of hibonites from the murchison carbonaceous chondrite twenty four hibonite dominated refractory grains from the murchison carbonaceous chondrite have been identified from polished grain mounts of density separates and have been morphologically and chemically divided into three groups 1 14 colourless platy crystal fragments placs with less than 2 7 tio2 2 3 pleochroic blue aggregates bags which are composed of crystal plates and fragments and have tio2 concentrations between 5 1 and 6 5 3 six spinel hibonite spherules and crystal aggregates shibs often with spinel fe silicate and clinopyroxene rims the maximum tio2 concentrations of hibonite in the shibs ranges from 3 5 to 7 6 but the tio2 concentration in one grain was heterogeneous and ranged from 0 5 to 5 0 hibonite in all types is stoichiometric with ti and mg predominantly in a coupled substitution of mg2 and ti4 for 2al3 one grain with a rounded hibonite core does not clearly fit into the three designated groups the hibonites have been analysed by ion microprobe mass spectrometry for their mg and ti isotopic compositions twelve of the placs have 26al27al 0 ratios less than 1 10 5 but the other two placs have 26al27al 0 of 5 5 10 5 and 7 7 10 5 the excess 26mg may reflect initial mg isotopic heterogeneities in the source region of the placs or be the result of in situ26al decay in which case the distribution of 26al was heterogeneous three bags show substantial positive mass fractionation of mg one grain has excess 26mg while the other two have 26mg depletions the 26mg depletions indicate the preservation of mg isotopic anomalies in the bags but the excess 26mg in one grain could be due to in situ26al decay the six shibs have excess 26mg that is correlated with 27al24mg the mg isotopic systematics of the shibs are consistent with the in situ decay of 26al with 26al27al 0 of ca 5 10 5 the unclassified hibonite has a clearly resolved deficit in 26mg titanium isotopic anomalies are common in the hibonites measured here the largest anomalies are in 50ti with variations in 50ti48ti ranging from 50 to 16 relative to terrestrial smaller anomalies are present in 49ti and 47ti the ti isotopic compositions are not directly correlated with morphological type but the placs show the largest variations in isotopic composition whereas the shibs are generally close to terrestrial the presence of hibonite populations with distinct morphological chemical and mg isotopic systematics suggests that there were several hibonite formation episodes within the early solar system the hibonites probably formed by the melting of refractory dust aggregates during local transient thermal events

the occurrence of grossite caal4o7 in chondrites the mineral grossite caal4o7 ca dialuminate also termed ca2 is a rare phase in terrestrial and extraterrestrial rocks in meteorites grossite was found in ca al rich inclusions cais from allende cv3 vigarano cv3 leoville cv3 efremovka cv3 colony co3 murchison cm2 alh 85085 ch acfer 182 ch acfer 059 e1 djouf 001 cr2 and the anomalous c chondrite adelaide in ca al rich inclusions from most of these meteorites grossite is an accessory phase however in many cais from alh 85085 acfer 182 and acfer 059 e1 djouf 001 it is a major phase in this paper we summarize the results of literature reports on grossite bearing inclusions and focus in detail on the occurrence mineralogy and chemistry of caal4o7 containing ca al rich inclusions in acfer 182 and acfer 059 e1 djouf 001 in these carbonaceous chondrites abundant cais with high modal abundances of grossite 30 vol often 60 vol were discovered to classify ca al rich inclusions with such high modal abundances of caal4o7 we suggest to introduce a new type of ca al rich inclusion grossite rich inclusions in acfer 059 e1 djouf 001 and acfer 182 grossite containing inclusions occur with different petrographic characteristics the most common type consists of a core of grossite rimmed by melilite ca pyroxene spinel hibonite in an other type anhedral polycrystalline grossite complexes of irregular shape are enclosed in melilite in some spherical ca2 inclusions abundant euhedral to subhedral grossite and or hibonite crystals are embedded in melilite in two inclusions a core of hibonite is mantled by grossite additionally some grossite bearing inclusions with unique texture and or mineralogy were found one of these inclusions is rich in zr y rich perovskite and contains phases rich in the ultrarefractory elements sc and or zr almost all of the grossite containing inclusions are rich in al2o3 50 wt even if grossite is only a minor phase based on textural appearance and or on ree contents in some inclusions core minerals with group ii patterns a condensation history for most inclusions is suggested a single inclusion rich in perovskite and other phases containing high concentrations of ultrarefractory elements appears to have formed as an early condensate from the solar nebula

probabilistic appraisal of earthquake hazard parameters deduced from a bayesian approach in the northwest frontier of the himalayas a straightforward bayesian statistic is applied in five broad seismogenic source zones of the northwest frontier of the himalayas to estimate the earthquake hazard parameters maximum regional magnitude mmax value of g r relationship and seismic activity rate or intensity for this purpose a reliable earthquake catalogue which is homogeneous for mw 5 0 and complete during the period 1900 to 2010 is compiled the hindukush pamir himalaya zone has been further divided into two seismic zones of shallow h 70 km and intermediate depth h 70 km according to the variation of seismicity with depth in the subduction zone the estimated earthquake hazard parameters by bayesian approach are more stable and reliable with low standard deviations than other approaches but the technique is more time consuming in this study quantiles of functions of distributions of true and apparent magnitudes for future time intervals of 5 10 20 50 and 100 years are calculated with confidence limits for probability levels of 50 70 and 90 in all seismogenic source zones the zones of estimated mmax greater than 8 0 are related to the sulaiman kirthar ranges hindukush pamir himalaya and himalayan frontal thrusts belt suggesting more seismically hazardous regions in the examined area the lowest value of mmax 6 44 has been calculated in northern pakistan and hazara syntaxis zone which have estimated lowest activity rate 0 0023 events day as compared to other zones the himalayan frontal thrusts belt exhibits higher earthquake magnitude 8 01 in next 100 years with 90 probability level as compared to other zones which reveals that this zone is more vulnerable to occurrence of a great earthquake the obtained results in this study are directly useful for the probabilistic seismic hazard assessment in the examined region of himalaya

wind waves and moveable bed bottom friction abstract effects of moveable bed bottom friction for wave observations and wave modeling are investigated using a state of the art bottom friction model this model combines the hydrodynamic friction model of madsen et al with a moveable bed roughness model based on grant and madsen analyzing the present model for idealized swell cases it is shown that swell might result in wave generated sand ripples the large change of roughness corresponding to initial ripple formation results in a preferred wave height for swell related to bathymetric scales as generally occur in shelf seas away from the coast the corresponding wave generated bottom roughness is not defined by the local wave conditions but is related to the overall energy balance of the wave field sediment data thus is imperative for the interpretation of observed decay rates and friction factors for swell for idealized depth limited wind seas near bottom wave motion is expected to generate partially washed out ripples and moderate sheet flo

relaxation time effects of wave ripples on tidal beaches 1 seabed roughness due to wave ripples is a key factor in controlling sediment transport processes in the nearshore zone roughness is commonly considered a function of the ripple geometry which in turn can be predicted from sediment and hydrodynamic parameters existing ripple predictors consider the bed morphology to be in equilibrium with the hydrodynamics whereas recent laboratory measurements show that the time scale for ripple development is of the order of tens of minutes to hours here we show that wave ripples on tidal beaches are significantly affected by relaxation time effects with ripple height and length progressively increasing during the rising tide and remaining constant during the falling tide moreover we examine the ripples in the context of existing empirical models and suggest how the temporal evolution over a tidal cycle may be predicted

ion microprobe studies of efremovka cais i magnesium isotope composition five coarse grained ca al rich refractory inclusions cais from the efremovka cv3 chondrite are analysed for their magnesium isotopic composition using an ion microprobe the analysed inclusions represent the three common cai types a b1 and b2 data for magnesium isotopic composition of the major mineral phases melilite spinel fassaite and anorthite in these inclusions are used to determine intrinsic magnesium isotopic fractionations and to identify nonlinear effect in 26mg due to the decay of extinct 26al the magnesium isotopic mass fractionation f mg generally favours the heavier isotopes as is expected in the case of coarse grained cais the f mg data for two of the inclusions however show contrasting trends sympathetic behaviour found in both isotopic and petrographic data in one type b1 inclusion suggests that the parent melt of this inclusion experienced a short duration volatilization event prior to crystallization the isotopic data also suggest possible presence of relict spinel in this inclusion that constrains the cooling rate of the parent melt to 70 c h during crystallization hot and dense nebular settings that allow for such fast cooling can only be localized in nature the pristine nature of the efremovka cais as evident from the lack of secondary alteration products in them is well supported by the isotopic data three of the five inclusions yield well behaved mg al isochrons with 26al27al 0 close to the canonical value of 5 10 5 the anorthite data for another inclusion suggest minor disturbance in the isotopic systematics and yield a nearly well behaved isochron with a slightly lower value of 26al27al 0 data for melilite and anorthite in the fifth inclusion define apparent isochrons that suggest partial re equilibration and exchange of magnesium isotopes between these two phases the efremovka data are suggestive of a relatively homogeneous distribution of 26al in the solar nebula

the abundance and relative volatility of refractory trace elements in allende ca al rich inclusions implications for chemical and physical processes in the solar nebula abstract we have determined the relative volatility of lithophile refractory trace elements lrte in the solar nebula by first calculating 50 condensation temperatures for 26 lrte oxides assuming ideal solid solution in perovskite and where appropriate in hibonite and melilite the measured abundances of 25 lrte and six siderophile refractory trace elements in 97 group i 11 111 and v allende ca al rich inclusions cai s and in ultra refractory inclusions then are used to empirically modify lrte and refractory siderophile volatility sequences that are based on condensation temperatures alone sc is significantly less depleted in group ii allende cai s than are other lrte e g zr hf y that also have very high oxide condensation temperatures ba sr and eu three moderately volatile lrte are significantly more enriched in ca rich group ii and group iii allende cai s than they are in spinel rich varieties of these inclusions we explain these observations and several others by invoking dust fractionation s and crystal chemical and diffusion effects during the formation of allende cai s that overprinted volatility based on solid gas reactions alone for example we show that hibonite probably was not the carrier of the super refractory lithophile component that is missing from group ii allende inclusions anomalous hf depletions relative to zr and y that are common in group i iii and v allende cai s can be partly explained if anders and ebihara 38 overestimated the cosmic abundance of hf by approximately 10

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

influence of defects on sorted bedform dynamics 1 bedforms with plan view patterns consisting of long crests interrupted by defects occur ubiquitously in subaqueous and subaerial environments where they strongly influence flows and sediment transport we explore how such patterns adjust to changes in the external forcing we utilize a numerical model of a wide spread large scale seabed pattern sorted bedforms examining their response to changes in wave forcing numerical experiments show that the pattern adjustment progresses through two stages characterized by defect propagation and defect creation respectively and that the rates of the initial stage and therefore overall pattern adjustment are determined by the initial defect density all characteristics of the sorted bedforms are similarly influenced by the presence of defects although the processes of growth are likely to be different for other types of bedforms it is reasonable to expect they will be similarly influenced by defects in pre existing patterns

probabilistic assessment of earthquake hazards in the indian subcontinent the indian subcontinent is one of the most seismic prone areas of the world the himalayan mountains in the north mid oceanic ridges in the south and earthquake belts surrounding the indian plate all show that the subcontinent has undergone extensive geological and tectonic processes in the past the probability of the occurrence of earthquakes with magnitude 6 m b 7 during a specified interval of time has been estimated on the basis of four probabilistic models namely lognormal weibull gamma and exponential distribution for the indian subcontinent the seismicity map has been prepared using the earthquake catalogue from the period 1963 1994 and six different zones have been identified on the basis of clustering of events the model parameters have been estimated by the method of maximum likelihood estimates mle and method of moments mom a computer program package has been developed for all four models which represents the distributions of time intervals fairly well the logarithmic of likelihood ln l is estimated for testing the models and different models have been found to be plausible the probability of different magnitude thresholds has been evaluated using the gutenberg richter formula log n a bm for magnitude distribution the constants a and b have been computed for each region and found to be varying between 5 46 8 53 and 0 87 1 34 respectively

wave formed sediment ripples transient analysis of ripple spectral development 1 a new method has been developed that models the changes a wave formed rippled sediment bed undergoes as it is actively evolving between two given equilibrium states due to a change in surface wave conditions the transient analysis of rippled beds has received very little attention within the literature dynamic changes within ripple parameters have implications for the estimation of flow dissipation and sediment transport by changing the bottom roughness height the method uses the spectral density function of the rippled bed and is based on a series of ripple growth and ripple transition experimental tests the ripple evolution model was developed from the well known logistic growth law fitting the general solution of the logistic nonlinear differential equation to the experimental data enabled the evolution rate of the bed to be determined for each experimental test it was concluded that there was no difference between the evolution rate determined from the ripple growth tests and the ripple transition tests this indicated that the two types of growth are special cases of the same evolution processes which is adequately modeled by the logistic growth equation a functional dependence was established between the ripple evolution rate and the shields parameter this allows the evolution rate to be estimated from flow and sediment properties the estimation of the rate at which rippled sediment beds evolve under a variable sea state has the potential to lead to significant improvements to the way ripple transition and hence bottom roughness is approximated in coastal wave models

geometric bed roughness and the bed state storm cycle 1 temporal variation in the geometric roughness of the mobile sandy seabed during wave forcing events is investigated as a function of bed state the bed states include irregular ripples cross ripples linear transition ripples and flat bed each appearing repeatedly within a different range of wave energies as part of the bed state storm cycle ripple wavelengths determined from ensemble averaged roughness spectra indicate that irregular and cross ripples are suborbital whereas linear transition ripples are anorbital the observed ripple steepnesses indicate that irregular and linear transition ripples fall slightly below nielsen s 1981 field data relation whereas cross ripple steepnesses are anomalously low in comparison time series of geometric roughness are coherent across spatial frequency abrupt changes in geometric roughness occurred on timescales of 3 h on average during both the onset and the waning stages of storm events i e for both decreasing and increasing roughness respectively predicted response times based on ripple volume and bed load transport rate are in agreement with the observations when the best fit form of the meyer peter and muller 1948 type bed load relation obtained by ribberink 1998 is used in contrast the more standard form of this relation and the associated parameters yield predicted response times much shorter than those observed

a probabilistic estimate of the most perceptible earthquake magnitudes in the nw himalaya and adjoining regions nw himalaya and its neighboring region 25 40 n and 65 85 e is one of the most seismically hazardous regions in the indian subcontinent a region that has historically experienced large to great damaging earthquakes in the present study the most perceptible earthquake magnitudes mp are estimated for intensity i vii horizontal peak ground acceleration a 300 cm s2 and horizontal peak ground velocity v 10 cm s in 28 seismogenic zones using the two earthquake recurrence models of kijko and sellevoll bulletin of the seismological society of america 82 1 120 134 1992 and gumbel s third asymptotic distribution of extremes giii both methods deal with maximum magnitudes the earthquake perceptibility is calculated by combining earthquake recurrence models with ground motion attenuation relations at a particular level of intensity acceleration and velocity the estimated results reveal that the values of mp for velocity v 10 cm s show higher estimates than corresponding values for intensity i vii and acceleration a 300 cm s2 it is also observed that differences in perceptible magnitudes calculated by the kijko sellevoll method and giii statistics show significantly high values up to 0 7 0 6 and 1 7 for intensity acceleration and velocity respectively revealing the importance of earthquake recurrence model selection the estimated most perceptible earthquake magnitudes mp in the present study vary from mw 5 1 to 7 7 in the entire zone of the study area results of perceptible magnitudes are also represented in the form of spatial maps in 28 seismogenic zones for the aforementioned threshold levels of intensity acceleration and velocity estimated from two recurrence models the spatial maps show that the quetta of pakistan the hindukush pamir himalaya the caucasus mountain belt and the himalayan frontal thrust belt kashmir kangra uttarkashi chamoli regions exhibit higher values of the most perceptible earthquake magnitudes mw 6 0 these spatially distributed values indicate good agreement with high seismic hazard zones in previously published hazard maps based on seismicity maximum expected earthquake magnitudes during specific time intervals and maximum expected acceleration these maps have useful implications in preparing earthquake selection criteria for the anti seismic design of non critical structures in the study region

fluffy type a ca al rich inclusions in the allende meteorite abstract allende fluffy type a s fta s are a distinct sub group of ca al rich inclusions whose primary mineral assemblage consists of al rich melilite ak 0 33 spinel that is commonly very v rich perovskite and frequently hibonite some contain relatively coarse grained melilite up to 1 5 mm that is intensely kink banded and commonly reversely zoned hibonite and v rich spinel others contain much finer grained and strain free melilite 50 m and have not been found to contain hibonite or v rich spinel some fta s contain both coarser and finer grained melilite and textural relationships indicate that the latter is replacing the former fta s are characterized by extremely irregular shapes and 60 75 volume per cent of fine grained secondary alteration products many are aggregates of innumerable nodules each of which is surrounded by a wark lovering type rim sequence these nodules are frequently separated from one another by matrix like clastic rim material other fta s do not have nodular structure structural and mineralogical characteristics of their wark lovering rims suggest that fta s did not achieve their shapes by deformation of a liquid or a hot plastic solid in contrast to those in type b inclusions formation of reverse zoning in the coarser grained melilite crystals in fta s cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure further evidence against a liquid origin is the wide range of spinel compositions within individual coarser grained fta s the fact that the reversely zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues fta s are aggregates in some of which are preserved vapor solid condensate grains that formed at high temperature in the solar nebula

modeling earthquake recurrence in the himalayan seismic belt using time dependent stochastic models implications for future seismic hazards interest in and pertinent studies related to the seismic hazard in the himalayan region have increased significantly since the instrumental era and each damaging earthquake encourages its reestimation in the work presented herein the non poissonian probabilities of exceedance of magnitudes in a specified time in the future were investigated for different elapsed times based on the recurrence time intervals of past earthquakes in the himalaya using the weibull log normal gamma and inverse gaussian stochastic models the whole himalayan arc is divided into four seismogenic source zones viz the northwestern himalayas zone 1 the central seismic gap region zone 2 the eastern nepal and sikkim zone 3 and the eastern himalayas zone 4 by considering approximately 380 years of seismological data the suitability of each stochastic model for each zone was estimated using the kolmogorov smirnov k s test to describe the different physical processes responsible for earthquake occurrence the results show that the gamma inverse gaussian log normal and inverse gaussian models were most suitable for zones 1 4 respectively for m 6 0 the cumulative probability of recurrence intervals reaches up to 90 in 30 years for zones 1 and 2 49 years for zone 3 and 41 years for zone 4 the estimated conditional probability reaches 90 in 30 years in zone 1 35 years in zone 2 and 50 years in zones 3 and 4 the most suitable models for m 7 0 were found to be the log normal for zones 1 2 and 3 and gamma for zone 4 the cumulative probability for m 7 0 reaches 90 in 85 years in zone 1 86 years in zone 2 93 years in zone 3 and 148 years in zone 4 the estimated conditional probabilities reach 90 in 80 years in zone 1 90 years in both zone 2 and 3 and 150 years in zone 4 it is strongly recommended that model suitability be evaluated in complex regions such as the himalaya before proceeding with seismic hazard assessments the heterogeneous and complex tectonics of the himalayas differentiated plate motions different stress release patterns spatially and temporally and locking unlocking of faults thrusts are some of the reasons responsible for the different probabilistic models describing the earthquake occurrence phenomena in these four zones

calculating bottom orbital velocity beneath waves abstract methods are presented for calculating directly from a known wave height period and water depth the orbital velocity produced at the sea bed by surface waves two curves are sufficient to allow the root mean square bottom orbital velocity to be calculated for wave spectra having any one of the jonswap pierson moskowitz bretschneider issc or ittc forms a third curve covers the monochromatic case other curves allow the ratio of the peak periods of bottom orbital velocity and surface elevation to be calculated for the above five spectral forms values are deduced for the height and period of the monochromatic wave which most closely matches the bottom orbital velocity obtained from a full spectral representation optimised over water depths ranging from deep water to breaking

subgrid modeling of moveable bed bottom friction in wind wave models a subgrid moveable bed bottom friction model is developed for use in large scale wind wave models this model defines a representative bottom roughness based on the local application of a discontinuous roughness model and a statistical description of depth sediment and wave parameters for a finite area within the model i e a grid box the model reproduces the discontinuous attenuation behavior of swell in conditions of initial ripple formation as predicted by a small scale model it furthermore suppresses non physical oscillations of swell energy and unrealistically strong dependencies of depth limited wave heights on sediment parameters an alternative interpretation of the model explains the continuous transition between the no ripple and ripple regimes as sometimes observed in nature

probabilistic assessment of earthquake hazard in gujarat and adjoining region of india the gujarat and adjoining region falls under all four seismic zones v iv iii and ii of the seismic zoning map of india and is one of the most seismically prone intracontinental regions of the world it has experienced two large earthquakes of magnitude m w 7 8 and 7 7 in 1819 and 2001 respectively and several moderate earthquakes during the past two centuries in the present study the probability of occurrence of earthquakes of m 5 0 has been estimated during a specified time interval for different elapsed times on the basis of observed time intervals between earthquakes using three stochastic models namely weibull gamma and lognormal a complete earthquake catalogue has been used covering the time interval of 1819 to 2006 the whole region has been divided into three major seismic regions saurashtra mainland gujarat and kachchh on the basis of seismotectonics and geomorphology of the region the earthquake hazard parameters have been estimated using the method of maximum likelihood the logarithmic of likelihood function ln l is estimated and used to test the suitability of models in three different regions it was found that the weibull model fits well with the actual data in saurashtra and kachchh regions whereas lognormal model fits well in mainland gujarat the mean intervals of occurrence of earthquakes are estimated as 40 455 20 249 and 13 338 years in the saurashtra mainland gujarat and kachchh region respectively the estimated cumulative probability probability that the next earthquake will occur at a time later than some specific time from the last earthquake for the earthquakes of m 5 0 reaches 0 9 after about 64 years from the last earthquake 1993 in saurashtra about 49 years from the last earthquake 1969 in mainland gujarat and about 29 years from the last earthquake 2006 in the kachchh region the conditional probability probability that the next earthquake will occur during some specific time interval after a certain elapsed time from last earthquake is also estimated and it reaches about 0 8 to 0 9 during the time interval of about 57 to 66 years from the last earthquake 1993 in saurashtra region 31 to 51 years from the last earthquake 1969 in mainland gujarat and about 21 to 28 years from the last earthquake 2006 in kachchh region

probabilistic assessment of earthquake recurrence in northeast india and adjoining regions northeast india and adjoining regions 20 32 n and 87 100 e are highly vulnerable to earthquake hazard in the indian sub continent which fall under seismic zones v iv and iii in the seismic zoning map of india with magnitudes m exceeding 8 7 and 6 respectively it has experienced two devastating earthquakes namely the shillong plateau earthquake of june 12 1897 mw 8 1 and the assam earthquake of august 15 1950 mw 8 5 that caused huge loss of lives and property in the indian sub continent in the present study the probabilities of the occurrences of earthquakes with magnitude m 7 0 during a specified interval of time has been estimated on the basis of three probabilistic models namely weibull gamma and lognormal with the help of the earthquake catalogue spanning the period 1846 to 1995 the method of maximum likelihood has been used to estimate the earthquake hazard parameters the logarithmic probability of likelihood function ln l is estimated and used to compare the suitability of models and it was found that the gamma model fits best with the actual data the sample mean interval of occurrence of such earthquakes is estimated as 7 82 years in the northeast india region and the expected mean values for weibull gamma and lognormal distributions are estimated as 7 837 7 820 and 8 269 years respectively the estimated cumulative probability for an earthquake m 7 0 reaches 0 8 after about 15 16 2010 2011 years and 0 9 after about 18 20 2013 2015 years from the occurrence of the last earthquake 1995 in the region the estimated conditional probability also reaches 0 8 to 0 9 after about 13 17 2008 2012 years in the considered region for an earthquake m 7 0 when the elapsed time is zero years however the conditional probability reaches 0 8 to 0 9 after about 9 13 2018 2022 years for earthquake m 7 0 when the elapsed time is 14 years i e 2009

spatio temporal characteristics of small scale wave current ripples on the ameland ebb tidal delta ebb tidal deltas are highly dynamic environments affected by both waves and currents that approach the coast under various angles among other bedforms of various scales these hydrodynamics create small scale bedforms ripples which increase the bed roughness and will therefore affect hydrodynamics and sediment transport in morphodynamic models sediment transport predictions depend on the roughness height but the accuracy of these predictors has not been tested for field conditions with strongly mixed wave current dominated forcing in this study small scale bedforms were observed in the field with a 3d profiling sonar at five locations on the ameland ebb tidal delta the netherlands hydrodynamic conditions ranged from wave dominated to current dominated but were mixed most of the time small scale ripples were found on all studied parts of the delta superimposed on megaripples even though a large range of hydrodynamic conditions was encountered the spatio temporal variations in small scale ripple dimensions were relatively small height n 0 015 m length 0 11 m also the ripples were always highly three dimensional these small dimensions are probably caused by the fact that the bed consists of relatively fine sediment five bedform height predictors were tested but they all overestimated the ripple heights partly because they were not created for small grain sizes furthermore the predictors all have a strong dependence on wave and current related velocities whereas the ripple heights measured here were only related to the near bed orbital velocity therefore ripple heights and lengths in wave current dominated fine grained coastal areas d50 0 25 mm may be best estimated by constant values rather than values dependent on the hydrodynamics in the case of the ameland ebb tidal delta these values were found to be n 0 015 m and 0 11 m

origin of spinel rich chondrules and inclusions in carbonaceous and ordinary chondrites our evaluation of three models of the origin of spinel rich chondrules and inclusions includes new calculations of the major element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval our condensation calculations show that spinel rich chondrules did not crystallize from metastable liquid condensates and that spinel rich inclusions are not aggregates of refractory nebular condensates we propose that spinel rich objects are fractionated distillation residues of small aggregates of primitive dust that lost ca si rich partial melts by evaporation ablation or splashing during collisions this model also explains why spinel rich chondrules and inclusions 1 are usually smaller than melilite rich chondrules and inclusions 2 often have highly fractionated trace element compositions and 3 usually do not contain pt metal nuggets even when they are more enriched in the pt group metals than nugget bearing melilite rich objects

spatial mapping of earthquake hazard parameters in the hindukush pamir himalaya and adjacent regions implication for future seismic hazard abstract the study deals spatial mapping of earthquake hazard parameters like annual and 100 years mode along with their 90 probability of not being exceeded nbe in the hindukush pamir himalaya and adjoining regions for this purpose we applied a straightforward and most robust method known as gumbel s third asymptotic distribution of extreme values giii a homogeneous and complete earthquake catalogue during the period 1900 2010 with magnitude mw 4 0 is utilized to estimate these earthquake hazard parameters an equal grid point mesh of 1 longitude x 1 latitude is chosen to produce detailed earthquake hazard maps this performance allows analysis of the localized seismicity parameters and representation of their regional variations as contour maps the estimated result of annual mode with 90 probability of nbe is expected to exceed the values of mw 6 0 in the sulaiman kirthar ranges of pakistan and northwestern part of the nepal and surroundings in the examined region the 100 years mode with 90 probability of nbe is expected to exceed the value of mw 8 0 in the hindukush pamir himalaya with caucasus mountain belt the sulaiman kirthar ranges of pakistan northwestern part of the nepal and surroundings the kangra himanchal pradesh and kashmir of india the estimated high values of earthquake hazard parameters are mostly correlated with the main tectonic regimes of the examined region the spatial variations of earthquake hazard parameters reveal that the examined region exhibits more complexity and has high crustal heterogeneity the spatial maps provide a brief atlas of the earthquake hazard in the region

mineral chemistry and origin of spinel rich inclusions in the allende cv3 chondrite the mineral chemistry of 20 spinel rich inclusions and spinel rich nodules in 16 olivine rich inclusions in allende was studied by electron probe microanalysis variations in the chemistry of hibonite are explained by a coupled substitution among al ti mg si fe and v two types of perovskite occur 1 1 a variety enriched in the super refractory trace elements zr and y 2 2 zr y poor perovskite spinel typically contains a significant amount of fe 5 wt feo and small amounts of cr v zn ca and ti there are positive crfe and znfe correlations in fe rich spinel mg rich clinopyroxenes that rim spinel generally contain 11 wt a12o3 3 wt tio2 and 2 wt feo the chemistry of many accessory minerals in the inclusions was also studied the mineralogy of spinel rich allende inclusions is similar to the mineralogy of fine grained ca al rich inclusions cai s in alh 77003 and rims on coarse grained cai s in allende spinel rich inclusions in mokoia kaba and murchison differ in that they contain fe poor spinel and lack feldspathoid rims the mineralogy mineral chemistry and bulk chemistry of spinel rich allende inclusions indicate that they are not primitive aggregates of crystalline nebular condensates the inclusions are aggregates of tiny concentric objects each of which we interpret to be a fractionated distillation residue that lost ca si rich partial melt we believe that the mineral chemistry of spinel rich allende inclusions rims on coarse grained cai s and olivine rich allende inclusions and chondrules was largely established in the solar nebula at high temperatures under moderately oxidizing conditions and later modified to some degree by mild thermal metamorphism in the allende parent body we suggest that interstellar dust aggregates were melted or distilled into allende inclusions by aerodynamic drag heating in regions of the nebula where the dust gas ratio was so enhanced that the local oxygen fugacity was raised by several orders of magnitude and liquids became thermodynamically stable

occurrence and orientation of anorbital ripples in near shore sands dimensional and of the anorbital type l0 d50 524 to 535 d0 d50 4300 to 25 000 with 7 6 cm mean wavelength in 150 mm median diameter sand the ripple crests were typically aligned perpendicular to the incident sea and swell direction specifically about 60 of the normals to the crests differ from wave direction by less than 5 and more than 90 by less than 10 during rapid changes in wave direction however ripple orientation adjustment lagged the wave direction by o 1 h ripple reorientation occurred piecewise along the crests with new crest segments sometimes bridging two or more old segments the 1 h reorientation time scale is longer by several orders of magnitude than the adjustment time based on theoretical bed load transport rate and the ripple volume as a possible explanation we suggest that a significant fraction of the transport more than 90 bypasses the ripples during orientation adjustment through large angles

petrology of alh85085 a chondrite with unique characteristics abstract alh85085 has several characteristics which set it apart from any known chondritic group its chondrules are smaller 25 75 m the majority are cryptocrystalline and all are volatile na k s depleted feni metal is more abundant 40 9 wt than in any other chondrite and sulfide abundance is low 1 1 matrix material does not surround the chondrules and fragments but occurs as lithic clasts lumps up to 300 m across the bulk composition of alh85085 is lower in na si and s si and higher in ni si fe si and mg si than in other chondritic groups the ca si al si and mg si ratios are closest to those of the renazzo chondrite grouplet cr matrix lumps are most similar to cr and murchison group cm chondrite matrices survival of this fragile matrix material as lithic clasts indicates that they were added just prior to the agglomeration of the chondrite all components chondrules fragments matrix lumps fall within a narrow size range which may be the result of aerodynamic sorting if so the sorting must have occurred after chondrule solidification and following a period of chondrule breakage since fragments from larger chondrules are present the ni vs co trend in the feni metal overlaps that of metal in cr chondrites and bencubbin these trends are similar to those of calculated nebular condensation paths indicating a nebular origin the cryptocrystalline texture and volatile depletion of the chondrules indicate that most chondrules were heated to temperatures above the liquidus although alh85085 cannot now be assigned to any known chondrite group it shares many similarities with cr chondrites and the bencubbin metal silicate chondritic assemblage and may be part of a chondritic group closely related to these meteorites

comparison of measurements and models of bed stress bedforms and suspended sediments under combined currents and waves abstract this study presents an analysis of data collected in an embayment off a sandy beach protected by shore parallel breakwaters observations were carried out over a forty day period including spring and neap tidal cycles and low and high wave activity measurements were collected on the waves currents bedforms and suspended sediments and these were used to derive estimates of the bed shear stresses ripple dimensions reference concentrations and suspended sediment profiles the aim of the present study was to use the measurements to assess commonly employed empirical formulations applied to sediment modelling in the coastal marine environment assessments are made of four ripple predictors two formulations of reference concentration and power law and exponential suspended sediment shape functions in some cases predicted parameters are well represented during low wave conditions whilst other parameters are better predicted under high wave events the outcome from the work is an evaluation of the predictive capability of the selected empirical formulae at the sandy location and discussions on the comparison between the observations and predictions

geometry migration and evolution of wave orbital ripples at leo 15 observations of the temporal evolution of the geometric properties and migration of wave formed ripples are analyzed in terms of measured suspended sand profiles and water velocity measurements six weeks of bedform observations were taken at the sandy medium to coarse sized sand leo 15 site located on beach haven ridge during the late summer of 1995 with an autonomous rotary sidescan sonar during this period six tropical storms several of hurricane strength passed to the east of the study site ripples with wavelengths of up to 100 cm and with 15 cm amplitudes were observed the predominant ripples were found to be wave orbital scale ripples with ripple wavelengths equal to 3 4 of the wave orbital diameter although orbital diameters become larger than 130 cm during the maximum wave event it is unclear if a transition to non orbital scaling is occurring ripple migration is found to be directed primarily onshore at rates of up to 80 cm day suspended transport due to wave motions calculated by multiplying acoustic backscatter measurements of suspended sand concentrations by flow velocity measurements are unable to account for a sufficient amount of sand transport to force ripple migration and are in the opposite direction to ripple migration thus it is hypothesized that the onshore ripple migration is due to unobserved bedload transport or near bottom suspended transport bedload model calculations forced with measured wave velocities are able to predict the magnitude and direction of transport consistent with observed ripple migration rates sequences of ripple pattern temporal evolution are examined showing mechanisms for ripple directional change in response to changing wave direction as well as ripple wavelength adjustment and erosion due to changing wave orbital diameter and relative wave to current velocities

an ultra refractory inclusion from the ornans carbonaceous chondrite a small refractory inclusion 1 g was found in the ornans carbonaceous chondrite the inclusion is extremely enriched in the most refractory ree lu er ho the more volatile light ree having more than two orders of magnitude lower concentrations refractory metals are fractionated in a similar way high abundances of the most refractory metals os re low content of more volatile metals such as ru and pt gas solid equilibrium at high temperatures can easily account for the observed relative abundances of refractory elements independent temperature estimates from ree abundances and refractory metal contents suggest an equilibrium temperature of about 1670 k at 10 3 atm the trace element pattern of the inclusion is complementary to the pattern of fine grained allende inclusions the inclusion may either represent a first condensate from a cooling gas of approximately solar composition or the very last residue from an evaporation process only the low contents of w and mo do not fit the pattern of refractory elements predicted from condensation calculations both elements however readily form volatile oxides therefore this depletion could be taken as indication of an evaporative origin of the inclusion the metal phase consists of small os rich grains in a comparatively os poor matrix grains and matrix appear to be a mechanical mixture this textural evidence cannot be easily reconciled with an evaporative origin a condensation origin of the inclusion would require that w and mo were lost at a later time in a more oxidising environment without affecting the metallic ta found in some of the metal grains

response of sand ripples to change in oscillatory flow ripples take time to evolve to a new equilibrium state in response to a change in wave generated oscillatory flow the paper presents results from flow tunnel experiments designed to examine oscillatory flow transient ripple processes under controlled full scale laboratory conditions the experiments include study of the growth of ripples from flat bed and the evolution of existing ripples to new equilibrium ripples in response to a step change in the flow in general ripples evolve through a combination of two main processes i from a flat bed or from a bed consisting of ripples that are smaller than the equilibrium ripples through a combination of slide and merge ii from a bed consisting of ripples that are larger than the equilibrium ripples through a combination of split and merge the experimental results show that equilibrium ripple geometry is independent of initial bed morphology while the time to reach equilibrium is largely independent of the initial bed and the equilibrium ripple size the time to reach equilibrium depends strongly on the mobility number and a new empirical equation relating mobility number and the number of flow cycles to equilibrium is proposed this equation is combined with a simple exponential function for ripple height growth or decay to produce a new empirical model for ripple height evolution which gives a reasonably good overall agreement with the measurements the model is based on experiments involving one sediment size only and further work is needed to develop the model for other sand sizes

bed forms created by simulated waves and currents in a large flume 1 the morphology and evolution of bed forms created by combinations of waves and currents were investigated using an oscillating plate in a 4 m wide flume current speed ranged from 0 to 30 cm s maximum oscillatory velocity ranged from 20 to 48 cm s oscillation period was 8 s except for one run with 12 s period and the median grain size was 0 27 mm the angle between oscillations and current was 90 60 or 45 at the end of each run the sand bed was photographed and ripple dimensions were measured ripple wavelength was also determined from sonar images collected throughout the runs increasing the ratio of current to wave i e oscillatory velocity decreased ripple height and wavelength in part because of the increased fluid excursion during the wave period increasing the ratio of current to waves or decreasing the angle between current and waves increased the three dimensionality of bed forms during the runs ripple wavelength increased by a factor of about 2 the average number of wave periods for evolution of ripple wavelength to 90 of its final value was 184 for two dimensional ripples starting from a flat bed bed form orientations at the end of each run were compared to four potential controlling factors the directions of waves current maximum instantaneous bed shear stress and maximum gross bed form normal transport mgbnt the directions of waves and of mgbnt were equally good predictors of bed form orientations and were significantly better than the other two factors

sand ripples generated by regular oscillatory flow abstract the prediction of ripple geometry is a necessary precursor to the prediction of sand transport under waves for ripple regime conditions the paper begins with a comparison of four existing methods for predicting the geometry of sand ripples generated by oscillatory flow the comparison points to substantial differences between ripple dimensions predicted by the methods especially for field scale conditions ripple geometry experiments carried out in a large oscillatory flow tunnel are then described the experiments involved a range of sand sizes and sinusoidal and asymmetric flows with periods and velocities typical of field conditions comparison of measured and predicted ripple geometries leads to the recommendation that the method of mogridge davies and willis be used to predict ripple geometry for field scale oscillatory flows the nielsen method yields good predictions of ripple length but the rapid fall off in ripple steepness predicted by the nielsen method at high mobility number is not supported by the measurements the lengths and heights of symmetric ripples produced by sinusoidal flows are found to be similar to the lengths and heights of asymmetric ripples produced by equivalent asymmetric flows three dimensional ripples occur with fine sand in long period flows typical of field conditions the dimensions of these ripples cannot be predicted using methods developed for two dimensional ripples previously suggested criteria for predicting the occurrence of three dimensional ripples fail when tested against a wide range of flow and sand conditions the occurrence of three dimensional ripples and the effects of ripple and flow history on ripple geometry require further research

movable bed roughness in unsteady oscillatory flow a model to predict the roughness in unsteady oscillatory flows over movable noncohesive beds is presented the roughness over movable beds is shown to be a function of the boundary shear stress rather than a fixed geometrical scale as is the case for fully rough turbulent boundary shear flows over immobile beds the model partitions the roughness into two distinct contributions these two contributions are due to the form drag around individual bed forms and to the near bed sediment transport the form drag over the bed forms is treated explicitly as a function of the boundary geometry and shear stress the ripples are predicted as a function of the local skin friction and a semiempirical expression is derived using standard law of the wall arguments which gives the ripple or form roughness as a function of the boundary geometry the ripple roughness is found to be proportional to the product of the ripple steepness and height favorable comparison of the form drag model with the results of bagnold s 1946 fixed ripple study is found the value of z0 associated with intense sediment transport in oscillatory flow over a flat bed is determined from carstens et al s 1969 experiments this value is found to be 7 or 8 grain diameters an expression is derived for the roughness associated with the maximum thickness of a near bottom sediment transporting layer consistent with owen s 1964 roughness hypothesis for saltation of uniform grains in air at large values of the boundary shear stress relative to the critical value for initial sediment motion the derived expression is similar to the results of smith and mclean s 1977 unidirectional flow approach modified for oscillatory flow the total roughness model is found to compare favorably with carstens et al s 1969 data in contrast to smith and mclean s 1977 steady flow findings the results here show that when ripples are present they account for a significant portion of the boundary roughness

observations of wave orbital scale ripples and a nonequilibrium time dependent model 1 measurements of seafloor ripples under wave dominated conditions from the leo15 site and the martha s vineyard coastal observatory were used to develop a time dependent model for ripple geometry the measurements consisted of backscatter imagery from rotary side scan sonars centimeter resolution bathymetric maps from a two axis rotary pencil beam sonar and forcing hydrodynamics during moderate energy conditions the ripple wavelength typically scaled with wave orbital diameter in more energetic conditions the ripples reached a maximum wavelength of 0 8 to 1 2 m and did not continue to increase in wavelength or decrease in height the observations showed that the relict ripples left after storms typically had wavelengths close to the maximum wavelength the time dependent model is based on an equilibrium model that allows the ripples to maintain wavelength proportional to wave orbital diameter until a suspension threshold determined by wave velocity and grain size is reached the time dependent model allows the ripple spectra to follow the equilibrium solution with a temporal delay that is based on the ratio of the ripple cross sectional area to the sediment transport rate the data was compared to the equilibrium model a simplified version of the time dependent model where the ripples were assumed to follow the equilibrium model only when the bed stress was sufficient to move sediment and the complete time dependent model it was found that only the complete time dependent model was able to correctly predict the long wavelength relict ripples and that the other approaches underpredicted relict ripple wavelengths

refractory inclusions in the murchison meteorite mineralogical and petrographic studies of a wide variety of refractory objects from the murchison c2 chondrite have revealed for the first time melilite rich and feldspathoid bearing inclusions in this meteorite but none of these is identical to any inclusion yet found in allende blue spinel hibonite spherules have textures indicating that they were once molten and thus their sio2 poor bulk composition requires that they were exposed to higher temperatures 1550 c than those deduced so far from any allende inclusion melilite rich inclusions are similar to allende compact type a s but are more al ti rich one inclusion much 1 consists of a delicate radial aggregate of hibonite crystals surrounded by alteration products and probably originated by direct condensation of hibonite from the solar nebular vapor the sinuous nodular and layered structures of another group of inclusions spinel pyroxene aggregates suggest that these also originated by direct condensation from the solar nebular gas each type of inclusion is characterized by a different suite of alteration products and or rim layers from all the other types indicating modification of the inclusions in a wide range of different physico chemical environments after their primary crystallization all of these inclusions contain some iron free rim phases these could not have formed by reaction of the inclusions with fluids in the murchison parent body because the latter would presumably have been very rich in oxidized iron other rim phases and alteration products could have formed at relatively low temperatures in the parent body but some inclusions were not in the locations in which they were discovered when this took place some of these inclusions are too fragile to have been transported from one region to another in the parent body indicating that low temperature alteration of these may have occurred in the solar nebula