propagation of rifting along the arabia somalia plate boundary into afar it is generally accepted that the aden ridge has propagated westward from 58 e to the western tip of the gulf of aden tadjoura at the edge of afar here we use new tectonic and geochronological data to examine the geometry and kinematics of deformation related to the penetration of that ridge on dry land in the republic of djibouti we show that it veers northward forming a narrow zone of dense faulting along the northeastern edge of the afar depression the zone includes two volcanic rifts asal ghoubbet and manda inakir connected to one another and to the submarine part of the ridge by transfer zones both rifts are composite divided into two or three disconnected parallel nw se striking subrifts all of which appear to have propagated northwestward in asal ghoubbet as in manda inakir the subrifts appear to have formed in succession through north directed jumps from subrifts more farther south at present the northernmost subrifts manda and dirko koma of the manda inakir rift form the current tip of the northward propagating arabia somalia plate boundary in afar we account for most observations by a mechanical model similar to that previously inferred for the gulf of aden in which propagation is governed by the intensity and direction of the minimum horizontal principal stress 3 we interpret the northward propagation on land almost orthogonal to that in the gulf to be related to necking of the central afar lithosphere where it is thinnest such necking may be a consequence of differential magmatic thickening greater in the center of the afar depression where the ethiopian hot spot enhanced profuse basaltic effusion and underplating than along the edges of the depression the model explains why the aden ridge foregoes its wsw propagation direction constant from 58 e to asal ghoubbet at a smaller scale individual rifts and subrifts keep opening perpendicular to the arabia somalia or danakil somalia motion vector and propagate northwestward concurrently such lithospheric cracks are forced to jump northward such that the plate boundary remains inside the regional n s necking zone changes of obliquity between the directions of overall and local propagation may account for different segmentation patterns a small angle promoting long en echelon subrifts and a high angle smaller nested subrifts within subrifts the propagation mechanism is thus similar whether in oceanic or continental lithosphere the principal change being the overall propagation path here governed by thickness changes rather than by the geometry in map view as previously inferred for the rest of the aden ridge finally because the same mechanism has led rifting along the red sea to propagate southward and jump to the western edge of afar the arabia somalia and arabia nubia plate boundaries tips have missed each other and keep overlapping further leading to strain transfer by large scale bookshelf faulting

block models of crustal motion in southern california constrained by gps measurements 1 we estimate slip rates on major active faults in southern california using a block model constrained by global positioning system measurements of interseismic deformation the block model includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle our estimates of the right lateral strike slip rate on the san andreas fault vary by at least a factor of 5 from a high of 35 9 0 5 mm yr in the carrizo plain to a low of 5 1 1 5 mm yr through the san bernadino segment shortening across the puente hills thrust and left lateral slip on the raymond hill fault are consistent with both thickening and escape tectonics in the los angeles basin discrepancies between geodetic and geologic slip rate estimates along the san andreas and san jacinto faults as well as in the eastern california shear zone may be explained by a temporal change in fault system behavior we find no substantial evidence for long term postseismic relaxation and infer that the viscosity of the lower crust upper mantle may be relatively high 1019 pa s

self similarity of the largest scale segmentation of the faults implications for earthquake behavior article i nfo article history earthquakes are sensitive to the along strike segmentation of the faults they break especially in their initiation propagation and arrest we examine that segmentation and search whether it shows any specific properties we focus on the largest scale fault segmentation which controls the largest earthquakes it is well established that major segments within faults markedly shape their surface cumulative slip length profiles segments appear as large slip bumps separated by narrow pronounced slip troughs inter segments we use that property to examine the distribution location number length of the major segments in 927 active normal faults in afar east africa of various lengths 0 3 65 km cumulative slips 1 1300 m slip rates 0 5 5 mm yr and ages 10 4 10 6 yr this is the largest fault population ever analyzed to identify the major bumps in the slip profiles and determine their number location and length we analyze the profiles using both the classical fourier transform and a space frequency representation of the profiles the s transform which is well adapted for characterizing local spectral properties our work reveals the fol lowing results irrespective of their length 70 of the slip profiles have a triangular envelope shape in conflict with the elastic crack concept irrespective of their length the majority of the faults at least 50 70 have a limited number of major segments between 2 and 5 and more commonly equal to 3 5 the largest scale segmentation of the faults is thus self similar and likely to be controlled by the fault mechanics the slip deficits at the major inter segment slip troughs tend to smooth as the faults accumulate more slip resulting in increased connection of the major segments the faults having accumulated more slip therefore generally appear as un segmented 10 30 our observations therefore show that whatever the fault on which they initiate large earthquakes face the same number of major segments to potentially break the number of segments that they eventually break seems to depend on the slip history structural maturity of the fault

the role of solid bitumen in the development of porosity in shale oil reservoir rocks of the upper cretaceous in colombia abstract the la luna formation turonian santonian age has been traditionally considered as one of the main hydrocarbon source rocks in the middle magdalena valley basin mmv in colombia at present this formation is also considered as an organic matter rich reservoir of shale oil type unconventional petroleum system of interest due to its significant resources of recoverable oil given the interest in this formation and the need to increase the knowledge of its physico chemical characteristics a series of petrographic geochemical toc content and rock eval pyrolysis and textural analyses picnometry and mercury intrusion porosimetry mip were carried out to investigate two of its members galembo and salada that were sampled from a core well perforated at the center of the basin the organic fraction of both members galembo and salada is made up mainly of a kerogen of type ii typical of a marine paleoenvironment solid bitumen and hydrocarbons the content in organic matter of terrestrial origin is very scarce to null these rocks have a degree of maturity that corresponds to the oil window and their high hydrogen content in combination with a relatively high carbon content makes them excellent source rocks the uneven distribution of the various types of organic matter along the galembo and salada members particularly of the solid bitumen that is concentrated at the lower levels of both members has resulted in large variations in porosity pore size distribution and modal pore throat characteristics even with small variations centimetric in depth the sedimentary levels in which kerogen is the predominant type of organic matter have a pore size distribution in the range of mesopores and macropores of small size whereas the solid bitumen rich levels show a predominance of pores of small pore size with a modal pore throat diameter below 10 nm the preliminary adsorption data obtained for all these samples to be published in a study that will follow this indicate that they contain some micropores which is significant in the case of levels with a high content in solid bitumen

impact of riser reconstructions on estimation of secular variation in rates of strike slip faulting revisiting the cherchen river site along the altyn tagh fault nw china abstract slip rates are heavily contested for many of the first order strike slip faults within the indo asian collision zone rates determined geodetically are generally lower than those reported using reconstructions of offset landforms and it is unclear if this discrepancy reflects true secular variation in slip history systematic errors in interpretation or both here i examine the methods used to derive slip rates from reconstructions of displaced fluvial risers and show that such rates are subject to potentially important uncertainties that have largely been overlooked review of published data demonstrates that the slip rate can vary by a factor of 1 2 to 5 for the same site depending on whether the reconstruction uses the age of the upper or lower terrace for the initiation of riser offset to reduce this epistemic uncertainty i have developed six geomorphic indices that can be used to identify the most accurate end member reconstruction 1 comparison of riser offset with inset channel width 2 similarity of riser and tread displacements 3 morphological analysis of the scarp profile 4 riser deflection in plan view 5 diachroneity of terrace abandonment and 6 whether riser crests or bases yield the slip vector without the use of these geomorphic observations the epistemic uncertainty associated with current methods for determining slip rate from offset fluvial risers is likely to be so large that there is no resolvable discrepancy between the gps and geologic rates within the indo asian collision zone application of three of these indices to new field mapping of the cherchen he river site 86 4 e along the central altyn tagh fault yields a revised slip rate of 9 4 2 3 mm yr equivalent within error to the rates previously derived from gps and paleoseismic studies although reinterpretation of published data from the sulamu tagh site 87 4 is consistent with this revised rate additional work is needed to reconcile this result with some of the rates reported near aksay 94 e

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

geochemistry mineralogy and technological properties of the main stephanian carboniferous coal seams from the puertollano basin spain this study is focused on the occurrence and distribution of mineral matter and major and trace elements in the high volatile bituminous coal from puertollano south central spain the relationship between ash behaviour and inorganic composition as well as the possible formation of fouling and slagging deposits in boilers during the conversion process were investigated the puertollano coals do not exhibit plastic properties despite their rank probably because of their high ash and inertinite contents the puertollano coal has medium to low total s content 0 48 to 1 63 db with a mean of 1 0 db and is characterised by relatively high contents of si pb sb and cs some elements such as as cd co cr cu ge li mn ni w and zn are also present in relatively high contents the enrichment in a number of heavy metals could be attributed to the common sulphide ores occurring near the puertollano coal deposit the following trace elements affinities are deduced a sulphide affinity as co cd cu ni sb tl and zn b aluminum silicate affinity k ti b co cr cs cu ga hf li nb rb sn ta th v zr and lree c carbonate affinity ca mg mn and b d organic affinity b the very high si levels and the anomalous enrichment in cs ge pb sb and zn shown by the puertollano coals account for the high contents of these elements in the puertollano fly ash when compared with the other spanish coal fly ashes the chemical composition of the high temperature ash hta is consistent with the trend shown by the ash fusion temperatures aft and also with the predictive indices related to slagging and fouling propensities thus the ash fusion temperatures increase with high values of al2o3 as well as with the decrease in fe2o3 cao and mgo

prospects for larger or more frequent earthquakes in the los angeles metropolitan region far too few moderate earthquakes have occurred within the los angeles california metropolitan region during the 200 year long historic period to account for observed strain accumulation indicating that the historic era represents either a lull between clusters of moderate earthquakes or part of a centuries long interseismic period between much larger moment magnitude m w 7 2 to 7 6 events geologic slip rates and relations between moment magnitude average coseismic slip and rupture area show that either of these hypotheses is possible but that the latter is the more plausible of the two the average time between m w 7 2 to 7 6 earthquakes from a combination of six fault systems within the metropolitan area was estimated to be about 140 years

variation in the chemistry of macerals in coals of the mist mountain formation elk valley coalfield british columbia canada abstract variations in elemental and molecular chemistry of macerals with vitrinite semifusinite and sporinite in particular are discussed for the coal seams of the mist mountain formation in the elk valley coalfield in western canada in the south elk valley coalfield carbon content of vitrinite oscillates around 85 and oxygen content increases gradually up section from seam a to c in the north elk valley coalfield carbon content in vitrinite shows marked variations from 70 to 85 between the samples and is lower than in the south elk valley coalfield which is consistent with a higher maturation level of south elk valley coalfield samples sulphur content is below 1 in both coalfields semifusinite in general has higher carbon and lower oxygen content than vitrinite whereas cutinite has higher carbon content than vitrinite and slightly higher or comparable to that of semifusinite functional group distributions show large variations between the seams and these variations are attributed mainly to differences in a primary depositional environment and only occasionally to later weathering and oxidation processes the results presented in this paper provide also information on the length and branching of aliphatic chains which for liptinite macerals is valuable from the oil generation viewpoint whereas for semifusinite it may help to understand reactive versus non reactive behaviour during coking

highly variable coastal deformation in the 2016 mw7 8 kaikōura earthquake reflects rupture complexity along a transpressional plate boundary abstract coseismic coastal deformation is often used to understand slip on offshore faults in large earthquakes but in the 2016 m w 7 8 kaik ura earthquake multiple faults ruptured across and sub parallel to the coastline along 110 km of coastline a rich dataset of coastal deformation comprising airborne lidar differencing field surveying and satellite geodesy reveals highly variable vertical displacements ranging from 2 5 to 6 5 m these inform a refined slip model for the kaik ura earthquake which incorporates changes to the slip on offshore faults and inclusion of an offshore reverse crustal fault that accounts for broad low amplitude uplift centered on kaik ura peninsula the exceptional detail afforded by differential lidar and the high variability in coastal deformation combine to form the highest resolution and most complex record of coseismic coastal deformation yet documented this should prompt reassessment of coastal paleoseismic records that may not have considered multi fault ruptures and high complexity deformation fields

coal facies studies in spain this work is a synthesis of the distribution of the main coal basins and sub basins in spain as well as the research carried out on their coal facies the coal fields are distributed through the paleozoic mainly pennsylvanian mesozoic cretaceous and cenozoic times peats also exist in the southeast spain granada area although these types of deposits are not included in this review spanish coal basins are both of a paralic and intramontane type and the coal rank is highly variable from lignite in the case of the younger coal seams to anthracite for those of carboniferous age

some aspects of the internal tide in knight inlet british columbia abstract the interaction of the tides with the sill of knight inlet a fjord located on the coast of british columbia is investigated the seasonal variation in the stratification of the inlet causes a large seasonal variation in the power withdrawn from the barotropic tide usually most of the withdrawn tidal power can be accounted for by a simple model of the internal tide obviously the model composition of the internal tide in an inlet is a function both of the inlet topography and the stratification in particular when there is a thin but distinct surface layer caused possibly by river runoff both first and second modes can transport significant amounts of energy away from the sill when this is the case the surface layer as well as the underlying stratification must be taken into account when calculating the amount of energy being transported by the internal tide

landscape form and millennial erosion rates in the san gabriel mountains ca abstract it has been long hypothesized that topography as well as climate and rock strength exert first order controls on erosion rates here we use detrital cosmogenic 10 be from 50 basins ranging in size from 1 to 150 km 2 to measure millennial erosion rates across the san gabriel mountains in southern california where a strong e w gradient in relief compared to weak variation in precipitation and lithology allow us to isolate the relationship between topographic form and erosion rate our erosion rates range from 35 to 1100 m ma and generally agree with both decadal sediment fluxes and long term exhumation rates inferred from low temperature thermochronometry catchment mean hillslope angle increases with erosion rate until 300 m ma at which point slopes become invariant with erosion rate although this sort of relation has been offered as support for non linear models of soil transport we use 1 d analytical hillslope profiles derived from existing soil transport laws to show that a model with soil flux linear in slope but including a slope stability threshold is indistinguishable from a non linear law within the scatter of our data catchment mean normalized channel steepness index increases monotonically though non linearly with erosion rate throughout the san gabriel mountains even where catchment mean hillslope angles have reached a threshold this non linearity can be mostly accounted for by a stochastic threshold incision model though additional factors likely contribute to the observed relationship between channel steepness and erosion rate these findings substantiate the claim that the normalized channel steepness index is an important topographic metric in active ranges

tidal energy dissipation at the sill of sechelt inlet british columbia abstract the energy budget of a tidally active shallow silled fjord is discussed constriction of the flow over the shallow sill causes a reduction in tidal amplitude and a phase lag across the sill a generalized expression for the total power extracted from the barotropic tide by dissipation at the sill is derived as a function of the tidal amplitude difference and phase lag of the tidal elevation using tide gauge data from both sides of the sill at the entrance to sechelt inlet british columbia this generalized expression yields estimates for the energy flux of the barotropic tide which approach 100 mw during spring tides from direct measurements of the currents the estimated frictional dissipation is equal to the flux out of the barotropic tide within experimental error a small amount of the energy flux 5 is estimated to go into the generation of a tidal jet which dissipates within a few kilometers of the sill and contributes to the formation of a mid water layer

geometric relations of dip slip to a faulted ground surface new nomograms for estimating components of fault displacement abstract the throw heave and dip slip components of displacement on a fault scarp can be estimated from two easily collected field measurements when fault dip is known or assumed the vertical separation and slope angle of the original ground surface displaced across the fault nomograms allow graphical determination of slip components for cases where fault dip is in the same or in an opposite direction as the slope of the ground surface the technique has several advantages over a previous method that requires three field measurements those of scarp height scarp slope angle and the slope of the original ground surface the geometric relations of a fault scarp illustrate that although differences between throw and vertical separation of the ground surface are small in the cases of steep fault dips or flat ground surfaces these differences can be greater than commonly assumed

the genesis of coal from the viewpoint of coal petrology abstract the genesis of the microscopic constituents of coal macerals and of maceral associations microlithotypes representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats peat microscopy especially promoted the understanding of humification and biological gelification both of which are decisive for the genesis of huminites vitrinites in brown coals and hard coals respectively microbial activity during peatification has been documented by chemists microbiologists and petrologists and recently by electron microscopical observations in coals this activity leads to the incorporation of lipid substances into the humic matter and later influences the chemical physical and technological properties of vitrinites geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal in this process the hydrogel brown coal is transformed to the bitumogel bituminous coal coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration the formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the coalification jumps of the macerals especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite bitumen and micrinite dead carbon bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals bituminite fluorinite and exsudatinite and suggests a higher proportion of algal material in coals than was thought earlier the genesis of various types of inertinite macerals will probably become an increasingly important subject of research especially with regard to rank inertinites that seem to attain their high inertinitic reflectance initially during coalification besides the origin of macerals the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu the peat forming vegetation palaeoclimate water and nutrient supply acidity marine and calcareous influence and fire with examples from euramerican carboniferous coals gondwana coals and tertiary brown coals vegetation water and oxygen supply eh conditions are most important for the generation of coal facies vegetation has been reconstructed with the help of palaeobotany including palynology cuticular analysis and wood anatomy in brown coals and with the study of petrified permineralized peats preserved in coal balls the microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative however the results of palynological and cuticular analyses should be evaluated with caution considering the varying resistance of palynomorphs and cuticles and in the case of palynomorphs their possible extrapaludal origin microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies especially in brown coals the much disputed origin of brown coal lithotypes is considered in detail for hard coals there seems to be agreement that coal layers rich in vitrites and liptinite poor clarite were deposited in wet forest swamps that microlayered liptinite rich clarites are sub aquatic humic muds and that inertinite rich durites represent oxidized peats the origin of liptinite rich durites is controversial either subaquatic muds or oxidized peats the latter perhaps from raised bogs a recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous oligotrophic conditions although raised bogs with a dense arborescent vegetation are known from borneo it seems not probable that most seams which were deposited in foredeeps or steadily sinking graben zones are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams but as in modern peats striking changes of coal facies are commonly caused by hydrological events e g inundations as a consequences of crevasses or of fires that burned the peat the origin of the inertinite rich gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub arctic peats is recommended coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite as well as by hydrogen rich vitrinites with a relatively low reflectance and high fluorescence all due to a strong bacterial activity in peats of low acidity proposals for further research are made in the conclusions

preliminary results of extraction experiments in an oil shale abstract soxhlet versus ultrasonic extraction efficiency on the immature puertollano oil shale has been tested the yields from the two methods are compared the extracts were compared by gas chromatography and geochemical parameters such as cpi and pristine phytane ratio calculated the ultrasonic extraction procedure is an effective quick and easy method which does not change the biomarker ratios of the bitumen minor efficiency differences can be observed among the solvents allowing a choice on the basis of handling properties carbon disulfide and chloroform are easiest to eliminate from the extract

internal tides observed by an acoustic doppler current profiler abstract previous studies of knight inlet british columbia revealed the presence of a strong internal m2 tide most of the energy was found to be in either the first or second dynamic modes due to difficulties in sampling of the surface layer objective estimates of the distribution of tidal energy and reflection coefficients until now have been impossible to obtain during june and july 1989 an intense acoustic doppler current profiler adcp sampling of the inlet was conducted these results are used to show the existence of a strong semidiurnal flow in the baroclinic field the authors propose that the horizontal phase information inherent in the spatial sampling by the adcp can be used to resolve the distribution of energy between dynamic modes through a least squares fit of the data to a simple free wave propagation model of the inlet the authors arrive at objective estimates of the distribution of m2 internal tide energy the fitting procedure is found to be sensitive to fluctuations in the

co seismic ruptures of the 12 may 2008 ms 8 0 wenchuan earthquake sichuan east west crustal shortening on oblique parallel thrusts along the eastern edge of tibet abstract the m s 8 0 wenchuan earthquake which devastated the mountainous western rim of the sichuan basin in central china produced a surface rupture over 200 km long with oblique thrust dextral slip and maximum scarp heights of 10 m it thus ranks as one of the world s largest continental mega thrust events in the last 150 yrs field investigation shows clear surface breaks along two of the main branches of the ne trending longmen shan thrust fault system the principal rupture on the nw dipping beichuan fault displays nearly equal amounts of thrust and right lateral slip basin ward of this rupture another continuous surface break is observed for over 70 km on the parallel more shallowly nw dipping pengguan fault slip on this latter fault was pure thrusting with a maximum scarp height of 3 5 m this is one of the very few reported instances of crustal scale co seismic slip partitioning on parallel thrusts this out of sequence event with distributed surface breaks on crustal mega thrusts highlights regional ew directed present day crustal shortening oblique to the longmen shan margin of tibet the long rupture and large offsets with strong horizontal shortening that characterize the wenchuan earthquake herald a re evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau and require a re assessment of seismic hazard along potentially under rated active faults across the densely populated western sichuan basin and mountains

late quaternary slip rate of the central sierra madre fault southern california implications for slip partitioning and earthquake hazard abstract the sierra madre fault system accommodates contraction within a large restraining bend area of the san andreas fault along the northern margin of the los angeles metropolitan area in southern california reverse slip along this fault system during earthquakes controls growth of the san gabriel mountains and poses a significant seismic hazard to the region here we measure the late quaternary slip rate of the central sierra madre fault csmf using analysis of high resolution topography combined with cosmogenic 10be surface exposure dating and post ir irsl geochronology we mapped terrace and fan surfaces from three drainages that cross the csmf and correlate them based on deposit character and geomorphic position cosmogenic nuclide and luminescence ages are consistent amongst the three prominent surfaces offset 5 to 28 m across the fault zone age estimates for these surfaces are 53 21 15 ka 35 9 ka and 12 5 ka based on data from two dating methods at three locations refined by inset age relationships estimated slip for these geomorphic markers is more uncertain than the measured vertical separation due to uncertainties in fault dip and ranges from 7 5 5 4 3 1 m to 58 5 46 3 14 4 m incremental dip slip rate estimates from different age surfaces and locations overlap within uncertainty with median values ranging from 0 6 to 1 1 mm yr the average slip rate for all three generations of markers is 1 1 1 1 0 4 mm yr this late quaternary slip rate for the csmf is slower than estimates based on interseismic geodetic data and emphasizes the importance of contraction distributed across multiple structures south of the sierra madre fault when assessed against the geodetic shortening budget despite being the central portion of the broader sierra madre fault system the csmf has a slip rate similar to or lower than neighboring sections suggesting that slip transfer onto other nearby faults control the along strike pattern of deformation rate paleoseismic evidence indicates that the last earthquake on the csmf was in the early holocene and the slip rate we estimate suggests that the accumulated elastic strain could produce many meters of slip in future earthquakes

coseismic fold scarps and their kinematic behavior in the 1999 chi chi earthquake taiwan 1 discrete scarps that are created or reactivated during large earthquakes are a locus of concentrated hazard a number of the coseismic scarps activated in the 1999 chi chi earthquake are actually fold scarps which display several types of ground deformation characterized by localized folding and are distinct from classic fault scarps which form by a fault cutting the surface this paper documents and analyzes fold scarps that formed or reactivated in the 1999 chi chi taiwan earthquake our results show the chi chi fold scarps can be generally divided into two types 1 those associated with folding ahead of the tip of a blind thrust fault at shallow depths and 2 those associated with folding by kink band migration above fault bends at substantial depths ranging from 0 8 to 5 km the previously published trishear model can be applied to model the former type while a new curved hinge kink band migration model is provided to describe the behavior of the latter type a key feature of fold scarps of the second type is that hinge zones are typically wide 25 100 m relative to the displacement in a single earthquake 1 10 m which exerts a significant control on fold scarp morphology and evolution because the coseismic strains of both types of fold scarps display relatively wide deformation zones 10 100 m relative to fault scarps wider set back zones might be appropriate from a public policy point of view to alleviate the risk to structural damage and collapse resulting from permanent ground deformation

influence of fault geometry on the spatial distribution of long term slip with implications for determining representative fault slip rates determining representative slip rates of active faults is essential to seismic hazard assessment and tectonic analysis here we take a two pronged approach to determine how spatially variable slip over many earthquake cycles impacts the sliprate record at potential sites of geologic investigation near releasing stepovers first we use 2d parametric models to estimate the probability that a point measurement is representative of the average slip rate for continuous strike slip faults and those with a range of releasing stepover geometries and friction values all models result in skewed distributions for which a randomly selected site has a higher probability of sampling a slip rate that exceeds the mean for most configurations individual point measurements are unlikely p 0 5 to yield a slip rate within 1 mm yr of the mean the probability can be notably improved 15 300 by summing slip rates of overlapping segments second we use 3d mechanical models of a well studied releasing stepover along the san jacinto fault to investigate the impact of specific fault geometries on slip rate distribution and the implications for existing slip rate estimates the model calculated dextral slip rates are consistent with the abundant geologic slip rate data available for this system although summing the slip rates at geologic sites across the stepover may produce a nonrepresentative slip rate the summed slip rates from the model are compatible with the representative slip rate thus the complete along trace slip rate distribution produced from the geologically consistent models provides a way to select sites for determining slip rates or interpreting isolated geologic slip rate data the site specific models also illustrate how to assess the uncertainty of slip rate data due to the spatial variability of slip rates in geometrically complex fault systems

uncertainties in slip rate estimates for the mission creek strand of the southern san andreas fault at biskra palms oasis southern california this study focuses on uncertainties in estimates of the geologic slip rate along the mission creek strand of the southern san andreas fault where it offsets an alluvial fan t2 at biskra palms oasis in southern california we provide new estimates of the amount of fault offset of the t2 fan based on trench excavations and new cosmogenic 10be age determinations from the tops of 12 boulders on the fan surface we present three alternative fan offset models a minimum a maximum and a preferred offset of 660 m 980 m and 770 m respectively we assign an age of between 45 and 54 ka to the t2 fan from the 10be data which is significantly older than previously reported but is consistent with both the degree of soil development associated with this surface and with ages from u series geochronology on pedogenic carbonate from t2 described in a companion paper by fletcher et al this volume these new constraints suggest a range of slip rates between 12 and 22 mm yr with a preferred estimate of 14 17 mm yr for the mission creek strand of the southern san andreas fault previous studies suggested that the geologic and geodetic slip rate estimates at biskra palms differed we find however that considerable uncertainty affects both the geologic and geodetic slip rate estimates such that if a real discrepancy between these rates exists for the southern san andreas fault at biskra palms it cannot be demonstrated with available data

fault interactions and large complex earthquakes in the los angeles area faults in complex tectonic environments interact in various ways including triggered rupture of one fault by another that may increase seismic hazard in the surrounding region we model static and dynamic fault interactions between the strike slip and thrust fault systems in southern california we find that rupture of the sierra madre cucamonga thrust fault system is unlikely to trigger rupture of the san andreas or san jacinto strike slip faults however a large northern san jacinto fault earthquake could trigger a cascading rupture of the sierra madre cucamonga system potentially causing a moment magnitude 7 5 to 7 8 earthquake on the edge of the los angeles metropolitan region

seismic and geodetic evidence for extensive long lived fault damage zones during earthquakes slip is often localized on preexisting faults but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics growing evidence suggests that the crust along active faults undergoes anomalous strain and damage during large earthquakes seismic and geodetic data from the calico fault in the eastern california shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli using seismic traveltimes trapped waves and interferometric synthetic aperture radar observations we document seismic velocities reduced by 40 50 and shear moduli reduced by 65 compared to wall rock in a 1 5 km wide zone along the calico fault observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures no large earthquake has broken the calico fault in historic time implying that fault damage persists for hundreds or perhaps thousands of years these fi ndings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces and throughout much of the seismogenic zone a result with implications for the amount of energy expended during rupture to drive cracking and yielding of rock and development of fault systems

distribution of sulfur in coals of the teruel mining district spain abstract the total pyritic sulfate and organic sulfur contents of the albian coals of the teruel coal mining district were determined the results have enabled us to describe the distributive characteristics of the sulfur in the study area in terms of coal seam stratigraphic series and sedimentary basin the accepted influences of the marine depositional environment and the diagenetic evolution of the coal seams on the sulfur content are reflected in this distribution moreover it is demonstrated that this distribution is modified by the massive leaching of sulfates from continental sourcelands towards the sedimentary basin owing to this the coal seams from proximal series without marine influence have a higher sulfur content than the coal seams from the series with a clear marine influence which is contrary to what has normally been reported

study of physical and chemical properties of vitrinites inferences on depositional and coalification controls abstract a detailed study of petrological geochemical textural and coking properties was carried out on vitrains from the puertollano blanzy montceau asturias and teruel the objective was to determine in depth the physical and chemical properties of a series of natural and pure vitrinites of different rank and the influence that the sedimentary and post sedimentary conditions had on them it is demonstrated that although vitrains are almost entirely made up of the huminite vitrinite maceral group they have a different composition thermal behaviour and physical properties thus geochemical and textural properties of blanzy montceau vitrains can be considered to be representative of the telinite the major component in both samples 75 vol at the beginning of the bituminization stage subbituminous high volatile c bituminous coals the characteristics of the puertollano vitrains described here can also be attributed to the telocollinite 80 vol for the high volatile c bituminous coal variations in physico chemical properties between puertollano and blanzy montceau vitrains are due to the differences in the initial composition of organic matter slight differences i e bed moisture content or porosity between vitrains from the two coal seams in the same basin can be attributed to their stratigraphic position several parameters such as s 2 hi oil and extraction yield and fluorescent properties suggest that the puertollano and blanzy montceau vitrains have a lower hydrocarbon potential the relationships between geochemical and textural properties make it possible to distinguish between normal and perhydrous vitrains the two different hydrogen enrichment processes that occur in vitrains from the teruel and asturias basins can be distinguished from the extraction yield data

on and off fault deformation associated with the september 2013 mw 7 7 balochistan earthquake implications for geologic slip rate measurements abstract the 24 september 2013 mw7 7 balochistan pakistan earthquake ruptured a 200 km long stretch of the hoshab fault in southern pakistan and produced the second largest lateral surface displacement observed for a continental strike slip earthquake we remotely measured surface deformation associated with this event using high resolution 0 5 m pre and post event satellite optical imagery we document left lateral near field on fault offsets 10 m from fault using 309 laterally offset piercing points such as streams terrace risers and roads peak near field displacement is 13 6 2 5 3 4 m we characterize off fault deformation by measuring medium 350 m from fault displacement using manual 259 measurements and automated image cross correlation methods respectively off fault peak lateral displacement values are 15 m and exceed on fault displacement magnitudes for 85 of the rupture length our observations suggest that for this rupture coseismic surface displacement typically increases with distance away from the surface trace of the fault however nearly 100 of total surface displacement occurs within a few hundred meters of the primary fault trace furthermore off fault displacement accounts for on average 28 of the total displacement but exhibits a highly heterogeneous along strike pattern the best agreement between near field and far field displacements generally corresponds to the narrowest fault zone widths our analysis demonstrates significant and heterogeneous mismatches between on and off fault coseismic deformation and we conclude that this phenomenon should be considered in hazard models based on geologically determined on fault slip rates

a regionally evolving transpressional duplex along the northern margin of the altyn tagh fault new kinematic and timing constraints from the sanweishan and nanjieshan china

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

paleoseismological evidence for non characteristic behavior of surface rupture associated with the 2004 mid niigata prefecture earthquake central japan abstract the 2004 mid niigata prefecture earthquake sequence mainshock magnitude mjma 6 8 which occurred in an active fold and thrust belt in northern central japan generated a small thrust surface rupture

a geochemical study of macerals from a miocene lignite and an eocene bituminous coal indonesia optical and chemical studies of maceral concentrates from a miocene lignite and an eocene high volatile bituminous c coal from southeastern kalimantan indonesia were undertaken using pyrolysis optical electron microprobe and ftir techniques pyrolysis products of vitrinite from bituminous coal were dominated by straight chain aliphatics and phenols the huminite of the miocene lignite produced mostly phenolic compounds upon pyrolysis differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences an undefined aliphatic source and or bacterial biomass were the likely contributors of n alkyl moieties to the vitrinite the resinite fraction in the lignite yielded dammar derived pyrolysis products as well as aliphatics and phenols as the products of admixed huminite and other liptinites the optically defined resinite rich fraction of the bituminous coal from kalimantan produced abundant n aliphatic moieties upon pyrolysis but only two major resin markers cadalene and 1 6 dimethylnaphthalene this phenomenon is likely due to the fact that eocene resins were not dammar related data from the electron microprobe and fourier transform infrared spectrometry strongly support the results obtained by py gc ms and microscopy

cosmogenic dating of fluvial terraces fremont river utah absolute dating of river terraces can yield long term incision rates clarify the role of climate in setting times of aggradation and incision and establish the rates of pedogenic processes while surface exposure dating using cosmogenic 10be and 26al would seem to be an ideal dating method the surfaces are composed of individual clasts each with its own complex history of exposure and burial the stochastic nature of burial depth and hence in nuclide production in these clasts during exhumation and fluvial transport and during post depositional stirring results in great variability in clast nuclide concentrations we present a method for dealing with the problem of pre depositional inheritance of cosmogenic nuclides we generate samples by amalgamating many individual clasts in order to average over their widely different exposure histories depth profiles of such amalgamated samples allow us to constrain the mean inheritance to test for the possible importance of stirring and to estimate the age of the surface working with samples from terraces of the fremont river we demonstrate that samples amalgamated from 30 clasts represent well the mean concentration depth profiles show the expected shifted exponential concentration profile that we attribute to the sum of uniform mean inheritance and depth dependent post depositional nuclide production that the depth dependent parts of the profiles are exponential argues against significant post depositional displacement of clasts within the deposit our technique yields 10be age estimates of 60 9 102 16 and 151 24 ka for the three highest terraces corresponding to isotope stages 4 5d and 6 respectively the mean inheritance is similar from terrace to terrace and would correspond to an error of 30 40 ka if not taken into account the inheritance likely reflects primarily the mean exhumation rates in the headwaters of order 30 m ma

the relationship between aromaticity vitrinite reflectance and maceral composition of coals implications for the use of vitrinite reflectance as a maturation parameter abstract previous studies on the aromaticity f a of coals have either limited themselves to the effects of rank or to differences between the macerals and generally conclude that f a and rank increase simultaneously although not necessarily linearly this study contains 13 c cp mas nmr analysis data of more than 70 coals obtained from different coal basins these are combined with published data to produce a data base with more than 130 analyses the aim is to determine the influence of rank and maceral composition on the measured f a of coals a plot of f a vs r o vitrinite reflectance shows a non linear relationship that can be described by a polynomial equation the shape of the curve produced by this equation is determined by the processes that occur during maturation only approx 50 of the coals in the data base have f a values that are accurately predicted by the vitrinite reflectance this is an indication of the large spread of values observed in the plot of f a vs r o as a result of the processes that occur during maturation the influence of the maceral composition on the f a was restricted to coals with r omax values 0 70 r o the equation generated shows that more than 80 of the coals tested with this level of rank have f a values that can be accurately predicted by an equation containing the r omax value the total vitrinite content and the contents of fusinite semifusinite and macrinite in the coals comparison of the f a values obtained from vitrinitic type iii kerogen with the f a values obtained from liptinitic sporinites and type ii kerogens reveals a pattern which illustrates the structural changes that occur during maturation both vintrinites and liptinites show a change in the slope in an f a vs r o plot although the reflectance level at which the change in slope occurs differs between the two kerogen types the changes in molecular structure that occur within the two kerogen types during maturation are discussed the implications of the f a r o relationship of vitrinites on the use of vitrinite reflectance as a maturation parameter are also discussed

surface rupture and slip distribution of the 1940 imperial valley earthquake imperial fault southern california implications for rupture segmentation and dynamics we analyzed high resolution aerial photography taken soon after the 1940 imperial valley earthquake to provide a higher resolution distribution of displacement with which to test variation in lateral slip to compare the difference in making slip measurements parallel to local or regional fault strike and to compare to the seismo logical properties of the 1940 earthquake we performed 648 new measurements of displacement along the 15 km section of rupture for which imagery exists nearly 7 m of maximum displacement occurred within 2 km of the border which was higher than previous estimates with an average slip of about 5 5 m for this section there is considerable variation along the strike on the order of 1 m of variability across hundreds of meters of lateral distance in the section of high slip areas of larger offset tend to have greater variations in displacement from these observations we conclude that lateral variability of displacement typically varies by as much as 30 along a rupture section the difference in measured displacement at a specific point along the fault varied considerably when using local fault strikes versus that of regional or average fault however the overall average difference between measurements for different azimuths at a specific point is only 0 01 0 19 m indicating that this is not a major issue if one is consistent finally abrupt changes in displacement along a strike are apparently related to segmentation and the rupture process and mimic the subevents as documented through seismological methods the largest moment pulse corresponds to the section south of the border whereas the greatest displacements occurred north of the border where the average moment release is inferred to be less we explain this by inferring a strong shallow as perity in the border region consistent with 1979 rupture event beneath it online material high resolution imagery of the 1940 rupture with locations of offset measurements and tabulated offset values

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

the time dependent hydraulic flow and dissipation over the still of observatory inlet abstract the time dependent hydraulic flow over the sill of a tidally energetic fjord observatory inlet british columbia is studied acoustic observations of streamlines and velocity were made near the sill crest during the summer of 1982 a time when freshwater runoff into the inlet had created a distinct surface layer while the tide is accelerating a simple three layer hydraulic model accurately simulates the flow near the sill crest however once the tide begins decelerating the observed flow undergoes a transition which the three layer model cannot explain it is estimated that during the period of observation the hydraulic flow utilized only about 5 of all the energy removed from the barotropic tide this suggests that other processes such as the internal tide are removing most of the energy from the barotropic tide

a numerical model of stratified circulation in indian arm british columbia a laterally integrated numerical model has been developed for the study of stratified circulation in inlets the model is time dependent and includes advective terms horizontal and vertical turbulent diffusion of momentum and salt and variations in width and depth initial and boundary conditions based on winter measurements in burrard inlet and indian arm were used to study the inlet s response to tidal forcing the friction term was tuned to match calculated and observed dissipation rates evidence for a standing wave pattern in the response of the m2 and k1 tidal constituents is discussed a comparison of model results with cyclesonde current meter time series at two locations in indian arm is consistent with resonance a modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes with the former dominating near the sill and the latter dominating in the deep basin second mode energy was significant for the k1 at some locations

surface faulting accompanying the borah peak earthquake and segmentation of the lost river fault central idaho on the morning of 28 october 1983 the ms 7 3 borah peak earthquake struck central idaho and formed a y shaped zone of surface faults that is divided into a southern a western and a northern section the total length of the surface faults is 36 4 3 1 km and the maximum net throw is 2 5 to 2 7 m the near surface net slip direction determined from the rakes of striations in colluvium averaged 0 17 m of sinistral slip for 1 00 m of dip slip the 20 8 km long southern section is the main zone of surface faulting and coincides with the thousand springs segment of the lost river fault it has the largest amount of net throw most complex rupture patterns and best evidence of sinistral slip the surface faults include zones of ground breakage as much as 140 m wide en echelon scarps with synthetic and antithetic displacements and individual scarps that are nearly 5 m high the 14 2 km long western section diverges away from the lost river fault near the northern end of the southern section the net throw on this section is generally less than 0 5 m but locally is as much as 1 6 m the new ruptures are poorly developed across the crest and north flank of the willow creek hills they are mostly downhill facing arcuate scars perhaps incipient landslides that may overlie a deeper zone of tectonic movement the northern section at least 7 9 km long is on the warm spring segment of the lost river fault and has a maximum net throw of about 1 m the pattern of surface faulting on this section is simple compared to the other sections a 4 7 km long gap in 1983 surface faults separates the northern and southern sections but contains an older scarp of late pleistocene age geologic seismologic and geodetic data from the earthquake suggest that barriers confined the primary coseismic rupture to the thousand springs segment of the fault the rupture propagated unilaterally to the northwest from a hypocenter near the southeastern end of the segment the southeastern boundary of the segment is marked by an abrupt bend in the range front a 4 km long gap in late quaternary scarps and transverse faults of eocene age that intersect the lost river fault the northwestern boundary of the thousand springs segment is at the junction of the willow creek hills and the lost river fault here the southern and western sections of surface faults diverge and there is a gap in the 1983 scarps during the first few weeks after the main shock the large magnitude and large stress drop aftershocks clustered near this barrier later aftershocks were mainly northwest of the barrier on the warm spring and challis segments and showed that strain adjustments eventually affected the entire northern part of the lost river fault fault scarp morphology and the bedrock geology suggest that the boundary between the thousand springs and warm spring segments has probably ruptured less frequently and had less net slip during much of the late cenozoic than the interior of the adjacent segments the 1983 faulting shows that although segment boundaries can stop or deflect primary ruptures secondary surface faulting can occur on adjacent segments of the main fault a late pleistocene scarp in the 1983 gap suggests that infrequent earthquakes perhaps larger than the 1983 event might break through a segment boundary and thus release strain on two adjacent segments

pore structure evolution of low rank coal in china abstract in china low rank coalbed methane cbm resources are in the early stage of exploration the evolution of pore structure for these coals around the first coalification jump is incomplete here systematic experiments were conducted to analyze the reservoir of low rank coal lignite and subbituminous coal from china s major low rank basins thus revealing the pore structure evolution of low rank coal in china scanning electron microscopy sem demonstrates that there are obvious differences in the pore types of different rank coals well developed cell lumina provides a large amount of macropore space in coals with ro

the petroleum potential of some tertiary lignites from northern greece as determined using pyrolysis and organic petrological techniques abstract oil condensate and gas have recently been discovered in the thermaikos gulf area of northern greece the source of these hydrocarbons is not known although there is a possibility that more mature equivalents of certain tertiary brown coals and lignites may be responsible a contribution from tertiary terrestrial organic matter to the epanomi oil is supported by its biomarker distributions especially the predominance of triterpenoid compounds other than hopanes in the m z 191 mass fragmentogram in this study the hydrocarbon potential of a suite of greek tertiary lignites is first examined using rock eval analysis three samples are then further investigated using organic petrography and gas chromatography gc and gas chromatography mass spectrometry gc ms of the extracted hydrocarbon fractions as well as by hydrous pyrolysis an intermontane lignite 6og 5 contains fluorescing huminite together with resinite on extraction this resinite is found to be of predominantly diterpenoid origin rock eval and hydrous pyrolysis support previous proposals that diterpenoid resinite needs a lower activation energy to generate hydrocarbons than most other types of organic matter a sample of a lignite deposited in a deltaic environment mm 3 contains a more diverse collection of liptinite macerals with resinite again predominating the resinite appears to be mostly of triterpenoid and sesterterpenoid origin the best hydrocarbon potential is shown by a sample deposited in a lagoonal environment kas 3 little discrete resinite is observed in this sample but it does contain abundant fluorescing huminite although it has a low s 1 s 1 s 2 ratio it gives a high yield on solvent extraction during which a significant fraction of the s2 is removed the fluorescence of the huminite after extraction is greatly reduced the hydrocarbons of the extract are believed to be predominantly derived from triterpenoid resinite unlike the pyrolysates of the other two lignites but in common with the epanomi oil the triterpenoids in the kas 3 pyrolysate are dominated by resin derived compounds rather than hopanes this and other similarities between the composition of the pyrolysates of kas 3 and the oil support the possibility that a more mature equivalent of this lignite could be the source of the epanomi oil

estimating surface rupture length and magnitude of paleoearthquakes from point measurements of rupture displacement we present a method to estimate paleomagnitude and rupture extent from measurements of displacement at a single point on a fault the variability of historic ruptures is summarized in a histogram of normalized slip then scaled to give the probability of finding a given displacement within a rupture for any magnitude considered the histogram can be inverted assuming any magnitude earthquake is as likely as another yielding probability density functions of magnitude and rupture length for any given displacement measurement to improve these distributions we include a term to account for the probability that the earthquake would cause ground rupture and two alternative distributions of earthquake magnitude the gutenberg richter magnitude distribution predicts shorter rupture lengths and smaller magnitudes than does a uniform distribution where any magnitude earthquake is considered equally likely longer ruptures and larger magnitudes than the uniform model are predicted by an alternative magnitude distribution designed to return site average displacement this model is a generalization of the characteristic earthquake model and reasonably describes paleoseismic findings on the southern san andreas fault where slip is accommodated by average displacements of a few meters and earthquake recurrence times of 100 250 years our results should increase the value of paleoseismic displacement measurements for hazard assessment in particular they quantify probability estimates of earthquake magnitude and rupture length where point observations of rupture displacement are available and so can contribute to probabilistic seismic hazard analyses online material rupture profiles used to sample rupture variability

the internal tide and resonance in indian arm british columbia the nature of the internal tide in indian arm is discussed in the winter of 1983 1984 this internal tide was observed to change from a predominantly m2 internal response to a predominantly k1 one this change in the response is explained as a partial resonance response of the system during the 1983 1984 winter the resonance period steadily increased from 14 hours at the start to 22 hours at the end it is suggested that the enhanced internal response at the k1 frequency late in the winter is due to resonance the fitting of normal modes was done to look at the energy flux in indian arm about 20 30 of the energy flux is found to return from the head of the inlet a finding supporting the resonance hypothesis which requires energy to be reflected from the head

a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault we mapped and analyzed two vertical exposures exposed on the walls of a 3 to 5 m deep 70 m long excavation and a smaller 3 m deep 10 m long excavation across the 1999 rupture of the chelungpu fault the primary exposure revealed a broad anticlinal fold with a 2 5 m high west facing principal thrust scarp contained in fluvial cobbly gravel beds and overlying fine grained overbank deposits sequential restoration of the principal rupture requires initial failure on the basal east dipping thrust plane followed by wedge thrusting and pop up of an overlying symmetrical anticline between two opposing secondary thrust faults net vertical offset is about 2 2 m across the principal fault zone from line length changes we estimate about 3 3 m of horizontal shortening normal to fault strike the ratio of these values yields a total slip of 4 0 m and an estimate of about 34 for the dip of the fault plane below the excavation this value is nearly the same as the 35 average dip of the fault plane from the surface to the hypocenter restoration of the exposed gravelly strata and adjacent overbank sediments deposited prior to the 1999 event around the principal rupture suggests the possible existence of a prior event a buried 30 m wide anticlinal warp beneath the uplifted crest of the 1999 event is associated with three buried reverse faults that we interpret as evidence for an earlier episode of folding and faulting in the site the prior event is also recorded in the smaller excavation which is located 40 m south and is oriented parallel to the larger excavation radiocarbon dating of samples within the exposed section did not place tight constraints on the date of the previous event available data are interpreted as indicating that the previous event occurred before the deposition of the less than 200 14 c yr b p overbank sands and after the deposition of the much older fluvial gravels we interpret the previous event as the penultimate event relative to the 1999 chi chi earthquake we estimated the long term slip rate of the chelungpu fault to be 10 15 mm yr during the last 1 ma based on previously published retrodeformable cross sections this rate is however significantly higher than geodetic rates of shortening across the chelungpu thrust where two pairs of permanent global positioning system stations suggest 7 10 mm yr of shortening across the fault given the 4 m of average slip the long term slip rate yields an interseismic interval of between 267 and 400 yr for the chelungpu fault

rates and processes of soil development on quaternary terraces in cajon pass california field and laboratory analyses of soils on 11 well dated fluvial terraces spanning the past 0 5 m y demonstrate that a threshold governs changes in several morphological and chemical characteristics of increasingly older soils correlations with respect to time among iron species soil morphology and soil silt and clay demonstrate that the chronosequence at cajon pass reflects primarily an evolutionary largely time dependent trend and does not reflect differences in external factors such as climate most of the soil development on holocene terraces of the cajon pass area is due to physical incorporation of eolian dust and organic material into initially very permeable gravels this process decreases soil permeability and is conducive for an increase in the magnitude of chemical weathering latest pleistocene and older pleistocene soils have developed clay and authigenic iron oxide rich b horizons at the expense of organic matter rich a horizons and color b horizons as the extent of chemical weathering has increased this conversion of the soil from a noncolloidal system to a much more colloidal system takes place over a relatively short period of time 4 000 yr and is herein defined as a type of pedologic threshold in the cajon pass area the attainment of the threshold and subsequent development of the argillic b horizon of soils on latest pleistocene terraces occurred during the holocene thus the absence of argillic horizons in soils on holocene terraces is attributable to simply their younger age rather than to the pleistocene to holocene climatic change the threshold is a function of several variables including influx rate of eolian dust and initial soil permeability therefore the time required to attain the threshold will vary in chronose quences characterized by geomorphic or geographic settings that are different from conditions found in cajon pass

co seismic thrusting rupture and slip distribution produced by the 2008 mw 7 9 wenchuan earthquake china field investigations reveal that the mw 7 9 wenchuan china earthquake of 12 may 2008 produced a 285 km long surface rupture zone with dominantly thrusting slip accompanied by a right lateral component along the central northern segments of the zone and left lateral component along the southern segment along the longmen shan thrust belt eastern margin of the tibetan plateau the co seismic ruptures mainly occurred along the pre existing yingxiu beichuan guanxian anxian and qingchuan faults which are the main faults of the longmen shan thrust belt the displacements measured in the field are approximately 0 5 6 5 m in the vertical typically 1 3 m accompanied by an average left lateral component of 2 m along the 50 km long southernmost segment of the rupture zone and an average right lateral component of 1 m along the 150 km long central northern segments the maximum thrust slip amount is estimated to be 10 m accompanied by 9 m of shortening across the rupture zone this finding is consistent with estimates based on seismic data the rupture length and maximum vertical displacement are the largest among all intracontinental thrust type earthquakes reported to date our findings demonstrate that i the wenchuan earthquake occurred upon pre existing active faults of the longmen shan thrust belt thereby controlling the spatial distribution of co seismic surface rupture and displacement and the rupture processes of the earthquake ii the long rupture length and large thrusting slip resulted from compressive stress associated with eastward extrusion of the tibet plateau as it accommodates the ongoing penetration of the indian plate into the eurasian plate and iii present day shortening strain upon the eastern margin of the tibetan plateau is mostly released by seismic slip along thrust faults within the longmen shan thrust belt

variability of displacement at a point implications for earthquake size distribution and rupture hazard on faults abstract to investigate the nature of earthquake magnitude distributions on faults we compare the interevent variability of surface displacement at a point on a fault from a composite global data set of paleoseismic observations with the variability expected from two prevailing magnitude frequency distributions the truncated exponential model and the characteristic earthquake model we use forward modeling to predict the coefficient of variation cv for the alternative earthquake distributions incorporating factors that would effect observations of displacement at a site the characteristic earthquake model with a characteristic magnitude range of 0 25 produces cv values consistent with the data cv 0 5 only if the variability for a given earthquake magnitude is small this condition implies that rupture patterns on a fault are stable in keeping with the concept behind the model this constraint also bears upon fault rupture hazard analysis which for lack of point specific information has used global scaling relations to infer variability in average displacement for a given size earthquake exponential distributions of earthquakes from m 5 to the maximum magnitude give rise to cv values that are significantly larger than the empirical constraint a version of the model truncated at m 7 however yields values consistent with a larger cv 0 6 determined for small displacement sites although this result allows for a difference in the magnitude distribution of smaller surface rupturing earthquakes it may reflect in part less stability in the displacement profile of smaller ruptures and or the tails of larger ruptures online material global surface displacement data and identified sources of uncertainty

application of two turbulence closure schemes in the modelling of tidal currents and salinity in the hooghly estuary abstract this paper has two purposes the first is to study the circulation and salinity in hooghly estuary along the east coast of india and the second is to compare the performance of two turbulence closure schemes by modelling it a breadth averaged numerical model using a sigma co ordinate system in the vertical is briefly described vertical diffusion of momentum and salt are parameterized by a simple first order turbulent closure or by a one equation model for turbulent kinetic energy tke which uses a specified mixing length the results are compared with the available neap and spring tide observations along the estuary for both low and high discharge periods the computed elevations and currents are in reasonable agreement with the observations showing no major differences in vertical current profiles by both the turbulent schemes however there is a slight under prediction of bottom currents the salinity profiles predicted by tke model show better matching with observations statistical tests are also conducted to study the comparative performance of the turbulent closure schemes the maintenance of two layer structure in residual currents and salt variability are also studied by using the model

paleoseismologic evidence for a 8 ka age of the most recent surface rupture on the eastern sierra madre fault northern los angeles metropolitan region california paleoseismologic data from the sierra madre fault a major north dipping reverse fault that extends for 75 km across the northern edge of the los angeles metropolitan region indicate that the most recent surface rupture on the eastern part of the fault occurred more than 8000 years ago coupled with evidence for a minimum reverse slip rate of 0 6 0 9 mm yr on the strand that we trenched the long elapsed interval since the most recent event suggests that the sierra madre fault breaks during very infrequent large magnitude m w 7 earthquakes events of such large magnitude are much larger than the largest earthquakes that have occurred on any of the los angeles area urban faults during the 200 year long historic period e g the 1971 m w 6 7 san fernando and 1994 m w 6 7 northridge earthquakes and must be considered in future seismic hazard analyses for southern california although more paleoseismologic data are needed to determine whether or not the sierra madre fault ruptures together with adjacent faults available data already show that the raymond fault a west southwest trending left lateral strike slip fault that intersects the central sierra madre fault has ruptured to the surface at least once and possibly several times since the most recent surface rupture on the eastern sierra madre fault moreover if the san andreas fault saf and the sierra madre fault ever rupture together then such events must be exceedingly rare with at least 50 100 saf m w 8 so called big ones occurring between every possible combined saf sierra madre fault event

paleoenvironmental conditions of puertollano coals spain petrological and geochemical study abstract in the present work petrographic geochemical and mineralogical data have been combined with results from prior paleobotanical studies in order to determine the sedimentary and postsedimentary diagenetic factors responsible for the physicochemical properties of coal seams and associated sediments from the puertollano stephanian coal basin although the coal seams 4 originated under similar lacustrine conditions the highest coal seams 1 and 1 bis show higher production preservation of structured tissues telinite and collotelinite than the lowest coal seams 2 and 3 where destruction of the cell tissues collodetrinite is predominant differences in degree of preservation as a result of changes in the environmental sedimentary conditions in the water table ph redox may explain the different maceral distribution this feature may also be due to the increase in degree of humification from the highest seams 1 and 1 bis to the lowest seams 2 and 3 however the gentle thermal maturation undergone by these stephanian coals only produced a slight modification in the physicochemical properties of the organic matter in general alkaline synsedimentary conditions could be deduced from the dominance of organic sulphur with respect to pyritic sulphur reducing conditions for seam 1 1 bis and 2 and more oxidant conditions for seam 3 can be deduced from maceral sulphur and carbonate distribution other diagenetic processes involved organic and inorganic sediments for example a kaolinitisation process with a different intensity for the early diagenetic stages suggests the occurrence of leaching processes which affected both organic and inorganic sediments

fault segmentation new concepts from the wasatch fault zone utah usa the question of whether structural segment boundaries along multisegment normal faults such as the wasatch fault zone wfz act as persistent barriers to rupture is critical to seismic hazard analyses we synthesized late holocene paleoseismic data from 20 trench sites along the central wfz to evaluate earthquake rupture length and fault segmentation for the youngest 3 ka and best constrained earthquakes differences in earthquake timing across prominent primary segment boundaries especially for the most recent earthquakes on the north central wfz are consistent with segment controlled ruptures however broadly constrained earthquake times dissimilar event times along the segments the presence of smaller scale subsegment boundaries and areas of complex faulting permit partial segment and multisegment e g spillover ruptures that are shorter 20 40 km or longer 60 100 km than the primary segment lengths 35 59 km we report a segmented wfz model that includes 24 earthquakes since 7 ka and yields mean estimates of recurrence 1 1 1 3 kyr and vertical slip rate 1 3 2 0 mm yr for the segments however additional rupture scenarios that include segment boundary spatial uncertainties floating earthquakes and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length we compare the central wfz to paleoseismic and historical surface ruptures in the basin and range province and central italian apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures our comparison also suggests that the probabilities of shorter and longer ruptures on the wfz need to be investigated

how well do surface slip measurements track slip at depth in large strike slip earthquakes the importance of fault structural maturity in controlling on fault slip versus off fault surface deformation abstract comparisons of observed surface displacements with geodetically inferred slip at depth in six large m w 7 1 strike slip earthquakes reveal a correlation between the structural maturity of the fault and the ratio of deep slip to surface slip that occurs on localized zones of surface rupture specifically structurally immature faults 25 km of total displacement manifest only 50 60 of total slip on narrow fault surface traces versus 85 95 for structurally mature faults 85 km total slip the same pattern holds when structurally simple parts of a surface rupture are analyzed separately from parts that exhibit obvious structural complexity e g discontinuous or multiple traces or significant dip slip these results imply that geologic measurements of surface slip along structurally immature faults are likely to significantly underestimate the true slip at depth in large earthquakes this observation has implications for a number of important problems including determination of fault slip rates which are based on surface offsets earthquake probability assessments which are based on geologic fault slip rates comparisons of geologic and geodetic rate data in the search for strain transients the structural evolution of fault zones estimation of paleo earthquake magnitudes based on geomorphic offsets analyses of the relative importance of faulting vs distributed deformation in accommodating relative plate motions in continental crust the design and construction of infrastructure built near active faults and possibly for the prediction of strong ground motions which may at least partially depend on the degree of slip localization to the surface

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

comparison of morphological dating models for cumulative reverse fault scarps 1 degradation morphology of scarps can be used to estimate the age of an episode of uplift linear diffusion models for slope degradation provide analytical solutions relying on simplified geometry and kinematics in this paper we evaluate to what extent such models can be applied to date cumulative reverse fault scarps by comparing their predicted degradation coefficients with those of a more realistic numerical model two analytical models with increasing complexity have been considered the cu and iu models represent the morphological evolution of a single vertical fault at a constant rate of uplift and that of a vertical fault shifting incrementally respectively synthetic data are generated by a numerical model accounting for reverse faulting linear diffusion and gravity controlled collapse we show that for cumulative reverse faulting without folding approximated models neglecting fault dip and gravitational collapse lead to valid estimates of the degradation coefficient in a lot of cases because gravitational collapse and reverse faulting are competitive geomorphic processes we provide estimates of the shifts expected on the degradation coefficient according to neglected processes

deep water renewal in the upper basin of loch sunart a scottish fjord abstract recording current meters were deployed near the surface and bottom in the upper basin of loch sunart during the summers of 1987 1989 and 1990 the measurements revealed frequent though irregular deep water renewal events when the basin water was replaced by density driven intrusions the data suggested that these events were induced by wind enhanced estuarine circulation during periods of low fresh water runoff a semi implicit laterally integrated estuarine model was modified to allow variable vertical grid spacing and to permit the sea surface to move vertically through the grid both modifications being necessary in order to apply the model to the sea loch environment a turbulence closure scheme was also incorporated the model can simulate the evolution of the salinity field over periods of several weeks and was used to examine the mechanisms that induce deep water renewal model results suggested that very weak stratification in the basin is required for renewal to occur and indicated

molecular characterisation of vitrinite in relation to natural hydrogen enrichment and depositional environment the py gc ms results of the study carried out on two groups of vitrinites perhydrous and non perhydrous of diaerent age and properties and on a trimaceralic coal associated with one of the perhydrous group are discussed such a study provides information about the eaect of natural hydrogen enrichment on vitrinite structure at the molecular level moreover the influence of the diaerent conditions in the sedimentary environment on the chemical structure of the vitrinite is also discussed this influence is inferred through diaerences in the distribution and relative amount of phenolic compounds found in the pyrolysates from two samples of two diaerent coal beds in the same basin but formed under diaerent paleoenvironmental conditions for vitrinites with a high h c atomic ratio despite having a strong perhydrous character their pyrolysates exhibit the highly phenolic signature typical of lignin derived material with only minor aliphatic compounds thus the major chemical structural elements in these vitrinites are simple phenols with a high contribution of para alkyl substituted derivatives however there is no parallel relationship between the evolution of the oxygenated functionalities and the reflectance values from the results obtained a coalification pathway where hydrogenation processes predominate over thermal ones is proposed the presence of resin like substances and or oils which are two of the causes of natural hydrogen enrichment in the molecular structure of vitrinites have therefore aaected the normal evolution of the lignin and contributed to the special properties of this type of materials 2000 elsevier science ltd all rights reserved

particulate matter exchange across a rjord sill abstract recent studies have indicated the existence of a considerably higher planktonic biomass in the deep waters of the saguenay fjord as compared to corresponding depths in the adjacent st lawrence estuary on the other side of a shallow sill the hypothesis that has been put forward to explain this phenomenon is related to the advection of near surface estuarine waters at times very rich in particulate matter over the entrance sill into the deeper waters of the fjord mixing processes associated with the development of a density flow the presence of a hydraulic jump or other mechanisms are assumed to be responsible for the common occurrence of lower density subsurface water within the basin as compared to that penetrating over the sill the exchange processes between the estuary and the fjord are described and an estimate made of the estuarine water volume that penetrates into the lower layer of the fjord over a semidiurnal tide cycle from these calculations the replacement time for the outer basin was estimated to range between one and four days the biological characteristics of this water were used to establish a budget for particulate matter exchange which showed in early august a typical net input of 188 t of particulate organic carbon into the deep waters of the fjord over one tide cycle

physics based scenario of earthquake cycles on the ventura thrust system california the effect of variable friction and fault geometry the ventura thrust system in california is capable of producing large magnitude earthquakes geological studies suggest that the fault geometry is complex composed of multiple segments at different dips thrust ramps dipping 30 50 linked with bed parallel decollements dipping 10 these latter types of gently dipping faults form due to preexisting weaknesses in the crust and therefore have different frictional parameters from thrust ramps the faults also experience different stresses because of how stresses are resolved onto the fault planes here we use a two dimensional fault model to assess how geometry and frictional properties of the ramp decollement system should affect the seismic cycle we test velocity strengthening velocity weakening and conditionally stable decollements and in addition explore how the dip angle of the decollement changes the earthquake behavior a velocity strengthening decollement cannot replicate the through going earthquake ruptures that have been inferred for the ventura fault system we therefore suggest that this and other decollements may be better represented using a velocity weakening or conditionally stable response our results show that minor variations in fault geometry produce slip amounts and recurrence intervals that differ only by 10 20 but do not fundamentally alter the types of earthquakes and interseismic slip we conclude that geological constraints on fault geometry are typically sufficient to produce modeled earthquake sequences that are statistically consistent with paleoseismic records however both frictional parameters along the fault and effective normal stress influence earthquake rupture patterns significantly more research is needed to adequately constrain these quantities in order for earthquake rupture models to work as effective predictors of fault behavior

the energetics and tidally induced reverse renewal in a two silled fjord a laterally integrated two dimensional numerical model is used to examine the influence of the m2 tide on the circulation in the saguenay fjord a two silled fjord with a large inner and a small outer basin located on the north shore of the st lawrence estuary it is found that the m2 tide is more vigorous in the outer than in the inner basin and that more vertical mixing occurs in the outer basin therefore the density at depth in the outer basin decreases faster than it does in the inner basin and the resulting horizontal pressure gradient causes a bottom flow of water from the inner to the outer basin across the inner sill this reverse renewal is evident in both the available observations and the simulation according to the model much of the m2 energy withdrawn from the surface tide is fed into the internal tide significant tidal energy is also advected by the mean flow velocity approximately 25 of the net energy flux into the fjord is dissipated within 2 km of the outer sill because of the baroclinic pressure i e the total pressure but with the influence of the surface displacement removed the subtidal circulation is associated with very large energy fluxes within the fjord these fluxes are much larger than the net rate at which tidal energy enters the fjord and they are greater than the subtidal advective energy flux they represent a large redistribution of energy within the fjord and their horizontal divergence along the fjord is almost in balance with the time rate of change of potential energy when a flux richardson number is calculated for the inner basin below sill depth a value of 0 075 is obtained which is close to values found for other fjords

a numerical model of the circulation in knight inlet british columbia canada abstract during spring 1988 a period of low freshwater runoff and summer 1989 a period of high freshwater runoff month long observations of velocity temperature and salinity were made throughout the water column in knight inlet both up inlet and down inlet of the sill measurements were made at depths of 2 4 6 9 and 12 m using s4 current meters at depths down to about 200 m using profiling current meters and at depths deeper than 200 m using aanderaa current meters anemometers were deployed at two locations along the inlet a laterally integrated two dimensional numerical model of the inlet that uses the mellor and yamada level 2 5 turbulence closure scheme and that accounts for the combined influence of the winds tides and freshwater runoff has been used to produce 30 day simulations of the velocity and density field in the inlet the vertical coordinate is transformed in the model so that very fine vertical resolution can be attained near the surface even though the tidal range is larg

partition of energy loss from the barotropic tide in fjords abstract as the barotropic tide propagates into and out of a fjord it loses energy to friction internal tides and high frequency internal waves estimates of these losses for three british columbia fjords using current meter data indicate that friction is negligible in two but important in one inlet the length and depth of the sill determines the importance of friction when friction is not important most of the energy lost goes into the internal tide but less than half of this energy propagates away from the sill simple models of the internal tide predict the correct energy transfer to satisfy an energy budget but do not agree with observations of the internal tidal energy flux away from the sill energy loss from the internal tide in or near the generation zone would account for the discrepancy the energy flux of the high frequency internal wave field is relatively small about 2 of the energy lost

surface slip gradients of large earthquakes for earthquakes that are large enough to break the earth s surface slip can be measured directly providing model independent information of spatially vary ing behavior in earthquakes here new techniques are developed and applied to extract robust measures of surface slip in particular i examine how differences in slip scale with differences in separation examining slip distributions of seven large earthquakes in a digital database i find that the curves collapse into a common behavior over kilometer to tens of kilometer length scales distributions of differences of slip are found to be reasonably well fit by normal distributions with the variance of the dis tributions scaling with separation distance in particular average slip differences are seen to be increasing linearly out to length scales of the seismogenic crust but with a nonzero intercept when extrapolated back to a zero separation of around 1 m offset the variability of slip extrapolated to zero separation the mean offset of around 1 m 96 15 m is a remarkable feature of the observations holding for all seven of the large earthquakes analyzed leaving aside the offset and looking at the increase as a function of separation the slope or lateral strain has a value consistent with large scale average strains thus behavior consistent with constant stress drop is seen at length scales smaller than the event size revealing a further invariant of earthquake dy namics finally taking into account the noisy environment by looking for coherent structures unlikely to be noise related i find structures which have moderate values of lateral strains on the order of a factor of 10 times mean values with values appearing to be independent of length scale and magnitude

channel dynamics sediment transport and the slope of alluvial fans experimental study a b s t ra c t we present the results of an experimental study of alluvial fan sedimentation under conditions of constant inflow water discharge qw sediment supply qso and median grain size d the study was designed to complement and test a recently formulated model of alluvial fan sedimentation and to emphasize the interactions between and controls on flow channelization and equilibrium fan slope flow channelization and fan sedimentation were studied under conditions of nearly steady uniform aggradation steady conditions were achieved by imposing a steadily rising base level just in balance with the average sediment aggradation rate experimental inflows covered a wide range of conditions allowing examination of the effects of variations in qw q so and d in both bedload and suspension dominated environments experimental results were most consistent with an expanding flow channel model key experimental findings successfully and quantitatively predicted by the expanding flow theory include 1 straight to slightly concave radial profiles of bedload dominated fans 2 distinctly convexo concave profiles of suspension dominated fans 3 a strong inverse relationship between qw and fan slope 4 a strong but secondary relationship between q so and fan slope and 5 near independence of d and fan slope so long as transport stage is high and bedload transport dominant however potential scale effects in the experiments arose from reduced flow reynolds numbers and incorrect geometric scaling of channel widths no confident conclusions regarding the debate over the relative importance of sheetfloods and braided channel flows can be drawn from the experimental data extrapolation to field scale is best accomplished through appropriate application of the theoretical model herein confirmed against experimental data

the importance of thermal behaviour and petrographic composition for understanding the characteristics of a portuguese perhydrous jurassic coal abstract the perhydrous batalha coal portugal is found in the cabacos and montejunto formation of the oxfordian kimeridgian upper jurassic age from the macroscopic point of view its appearance is similar to other perhydrous coals microscopically the maceral group of huminite is the main organic component 96 ulminite being the most important petrographic component followed by textinite with resinite 4 lumina filled the huminite random reflectance is 0 33 this coal is characterized by high h c atomic ratio and anomalous physical and chemical properties that are characteristic of perhydrous coals such as i the absence of any correlation between reflectance and the chemical rank parameters ii a lower real density than that of non perhydrous coals iii a high hydrogen content and iv suppressed reflectance using its calorific value moist ash free basis as rank parameter batalha coal must be considered a subbituminous a coal hydrogen enrichment due to the presence of resinite has influenced the technological properties of this coal namely i reduction of the thermostability and decrease in the temperature of initial thermal decomposition due to among other reasons the existence of aliphatic structures with low dissociation energy bonds resulting from the presence of resinite ii from the dtg profile the volatile matter combustion and char combustion is not evident iii development of chars made up of isotropic particles with angular edges which is typical of a low rank coal iv the evolution trend of gaseous compounds co co 2 and ch 4 during pyrolysis and v an increase in its calorific value due to its hydrogen content the study of this coal which is interbedded in jurassic formations in the lusitanian basin of portugal is a new contribution to the assessment of the evolution of organic matter in this area

long range and long term fault interactions in southern california paleoseismological data suggest the occurrence of four bursts of seismic moment release in the los angeles region during the past 12 000 yr the historic period appears to be part of an ongoing lull that has persisted for about the past 1000 yr these periods of rapid seismic displacement in the los angeles region have occurred during the lulls between similar bursts of activity observed on the eastern california shear zone in the mojave desert which is now seismically active a kinematic model in which the faults of the greater san andreas system suppress activity on faults in the eastern california shear zone and vice versa can explain the apparent switching of activity between the two fault networks combined with the observation that short term geodetic and longer term geologic rates co vary on major southern california fault systems this suggests that either 1 a temporal cluster of seismic displacements on upper crustal faults increases ductile deformation on their downward extensions or 2 rapid ductile slip in the lower crust beneath faults loads the upper crust driving a seismic cluster we suggest that alternating periods of rapid seismic displacement may be the expected mode of seismicity when two fault systems accommodate the same plate boundary motion and slip on one system suppresses slip on the other

microfacies and petroleum properties of coals as revealed by a study of north sea jurassic coals abstract the influence of the composition and microstructural aspects of coal microfacies on petroleum properties were investigated in light of petrographic and geochemical studies the first study concerns a collection of north sea jurassic coals of various maceral compositions the second study is a pyrolysis gas chromatography study on pure microlithotypes from a similar french jurassic coal the results show that hydrocarbon potential is logically increased by a high content in liptinite but more often in hydrogen rich vitrinite in the same way the hydrocarbon potential is reduced by a high inertinite content mainly due to pre sedimentary oxidation of the original biomass but also due to early diagenetic processes that lead especially to the formation of micrinite or to post sedimentary alterations these trends indicate that total hydrocarbon potential is increased by an autochthonous origin of the organic matter that was deposited in a relatively closed paleoenvironment and thus protected from detrital and organo detrital inputs finally the oil potential of humic coals as determined by open pyrolysis gas chromatographic studies as related to the weight of rock is similar to classical source rocks the structural aspects of the coal microfacies which probably play a role in the release of oil from coal seams in natural conditions are also discussed

organic matter maturity and hydrocarbon potential of the lower oligocene menilite facies in the eastern flysch carpathians tarcău and vrancea nappes romania abstract bulk organic geochemical and molecular composition data have been used to analyse the hydrocarbon potential and organic matter maturity of the lower oligocene menilite facies from two adjacent tectonic units of the eastern flysch carpathians tarc u and vrancea nappes romania due to the importance of these source rocks in hydrocarbon exploration in entire paratethys realm the data show strong variability in organic matter quantity and quality organic carbon content reaches peak values in the siliceous facies of the lower menilite member up to 8 6 wt toc which contains type ii kerogen with increasing contribution of flysch sedimentation mixed type ii iii kerogen gains importance the biomarker distribution reveals strong variation in the supplied organic matter common for flysch influenced sedimentary environments terrigenous input is marked by epicuticular wax imprint in n alkane distribution and occurrence of conifer biomarkers while marine organic matter origin is expressed by the occurrence of short chain n alkanes and hopanes especially in the siliceous facies thus these source rocks can be classified as oil prone and subordinately mixed oil gas prone the maturity in the outer tectonic unit vrancea is low t max 425 c r o 0 4 but increases towards the inner tarc u nappe t max 430 c r o 0 5 reaching onset of hydrocarbon generation the studied rocks have good petroleum potential but hydrocarbons were generated only in more mature tarc u nappe where solid bitumen veins were observed bitumen impregnation of numerous vitrinite grains possibly suppressed vitrinite reflectance thus leading to more accurate maturity assessment based on molecular proxies biomarker maturity indices the observed difference in maturity levels between the nappes results from the more inner position of the sampled tarc u nappe succession within the orogen relative to the vrancea unit this is related to different burial histories as well as variation in subsequent erosion and exhumation levels the actual hydrocarbon potential in the studied area varies due to local interplay of these critical factors

tidal asymmetry in an estuarine pycnocline 2 transport flood currents in shallow estuaries are driven by an along channel barotropic and baroclinic pressure gradient that increases monotonically toward the bottom while friction retards near bottom currents therefore in many estuaries there is a middepth maximum in flood currents we explore this phenomenon using a simple three layer model in which each layer has vertically uniform currents and constant density in this model the middle layer is of intermediate density and grows by shear induced entrainment from the other two layers this very simple model produces a middepth maximum in flood currents and simulates observed currents in the columbia river entrance channel within about 10 there is good qualitative agreement between model salinity transport and observed transport the model pycnocline rises and falls tidally in phase with the observed pycnocline although pycnocline depth and thickness are better simulated using results from a two layer model cudaback and jay 2000

a model study of density intrusions into and circulation within a deep silled estuary puget sound a laterally averaged hydrodynamical model is used to investigate episodic intrusions of denser more oceanic water across the shallow double silled entrance of puget sound and the resulting circulation within the interior deep basin tidal freshwater discharge and wind effects are also encompassed in model results model simulations were made of the 4 month period from december 1983 through march 1984 during that period hourly measurements of currents and salinity were made at the estuary entrance and on four moorings in the interior basin the first 60 days of salinity data were used with the model to choose rates of vertical turbulent mixing and the lag times between fresh water appearance at river gauges and its arrival in the main basin of the sound comparison of model results with the full 120 days of salinity and velocity data shows that the model incorporates the important circulation features of this estuary the model was then used to study intrusions and mixing in the sill region the model identifies these factors as controls on the occurrence and strength of intrusions the trans sill salinity gradient the intensity of tidal stirring and mixing over the sills the supply of fresher surface water resulting from river runoff and the winds time series of salinities in the interior basin show local maxima following local maxima in the trans sill salinity difference vertical transport in the sill region at both tidal and subtidal time scales is dominated by advection rather than diffusion though much of the vertical exchange occurs over the shallower sill a depth depression between the two entrance sills appears to be the site of significant overturning downwelling of surface water occurs on the landward side of both sills substantial freshening of the interior basin occurs during the winter months because river discharges are large and are stirred downward in the sill region to be entrained into landward bottom flows extraordinarily large river discharges can suppress the effect of large trans sill salinity differences with the effect of weakening potential intrusions winds can indirectly influence intrusions by longitudinally positioning fresher river influenced surface water in the sill region winds can directly influence intrusions via bottom compensation flows in admiralty inlet with northward winds encouraging intrusions and by changing salinities at the entrance to the sound and thus the trans sill salinity gradient

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

recent advances in coalification studies and their application to geology abstract recent advances in coalification studies since 1970 are reported concerning microscopic methods causes of coalification the coalification process as such and application to geology the degree of coalification rank is mostly determined on the basis of vitrinite reflectance measured on finely dispersed material in rocks for rocks bare of vitrinite other microscopic methods are used such as fluorescence properties of liptinites and graptolite reflectance under incident light or coloration of microfossils like palynomorphs and conodonts in transmitted light the validity of the various methods is discussed maximum rock temperature and its duration are the main causes of chemical coalification reactions heating rates during subsidence influence the attainment of rank equilibrium contact metamorphic coals and natural cokes formed from bituminous coals are characterized by a relatively high reflectance and anisotropy strong frictional heat may cause local increase of rank adjacent to thrust planes graphitization is thermodynamically not possible in nature without pressure and shearing confining pressure retards the chemical coalification reactions tectonic stress especially shearing promotes the increase of maximum reflectance and of anisotropy it commonly leads to bi axial optical properties instead of the more typical uni axial negative geometry of vitrinite in undisturbed coal seams bi axial optical properties are common for vitrinite inclusions in clastic rocks on the basis of combined fluorescence microscopical and geochemical studies bituminization has been recognized as the characteristic part of coalification in the range between sub bituminous and bituminous coal it is characterized by the generation of petroleum like substances which enable the coal to soften and to agglomerate during carbonization hydrogenation properties are favoured by the bituminization process the different liptinite macerals behave differently during coalification and pass coalification jumps at different rank stages a considerable part of total inertinites is formed during early coalification brown coal to sub bituminous coal stage as rank inertinite this new knowledge appears to become important in relation to hydrocarbon exploration diagenetic methane some examples for the application of coalification studies to geology refer to vitrinite reflectance as an indicator of rock diagenesis and metamorphism palaeogeographical and structural history palaeogeothermics and hydrocarbon exploration large scale areal coalification studies in foredeeps and backdeeps of ancient and recent orogens suggest estimations of crustal thicknesses and relations to plate tectonics

constraining the kinematics of metropolitan los angeles faults with a slip partitioning model due to the limited resolution at depth of geodetic and other geophysical data the geometry and the loading rate of the ramp decollement faults below the metropolitan los angeles are poorly understood here we complement these data by assuming conservation of motion across the big bend of the san andreas fault using a bayesian approach we constrain the geometry of the ramp decollement system from the mojave block to los angeles and propose a partitioning of the convergence with 25 5 0 5 mm yr and 3 1 0 6 mm yr of strike slip motion along the san andreas fault and the whittier fault with 2 7 0 9 mm yr and 2 5 1 0 mm yr of updip movement along the sierra madre and the puente hills thrusts incorporating conservation of motion in geodetic models of strain accumulation reduces the number of free parameters and constitutes a useful methodology to estimate the tectonic loading and seismic potential of buried fault networks