evidence from precise earthquake hypocenters for segmentation of the san andreas fault in san gorgonio pass we use precise hypocenter patterns and focal mechanisms to investigate the presence or absence of a continuous strike slip fault at depth connecting the san bernardino strand of the san andreas fault with the coachella valley segment of the banning fault we inverted 560 000 arrival times from 23 000 earthquakes 1981 1993 for high quality hypocenters and three dimensional p wave velocity structure in a 1 by 2 area centered on the san gorgonio pass cross sectional plots of relocated earthquakes reveal an abrupt 5 to 7 km high step in the maximum depth of hypocenters the step riser defines a near vertical locally curved surface that extends westerly more than 60 km from the coachella valley segment of the san andreas fault to the san jacinto fault a hypothetical continuous vertical san andreas fault through san gorgonio pass would cross the step at an oblique angle we suggest that the step is the expression of the contact between different basement rock types juxtaposed by large scale right slip motion on the ancestral san andreas fault south of the step in peninsular ranges type basement intrusives brittle failure occurs down to about 20 km depth while north of the step in san bernardino type basement pelona schist brittle failure occurs to only about 13 km depth the step provides a piercing plane that should be offset about 3 km right laterally by an active continuous vertical san andreas fault within the resolution of our mapping the step is not offset in this manner implying either that there has not been a throughgoing vertical fault at depth that a throughgoing fault has not experienced enough slip to offset the step or that a throughgoing fault is not vertical and dips north over the top of the step hypocentral patterns and focal mechanisms indicate distributed deformation thrust normal and strike slip faulting over a large volume in the san gorgonio pass region there is no evidence of hypocenter or slip vector alignments that would indicate a throughgoing continuous near vertical san andreas fault in summary we find no evidence indicating a continuous fault at seismogenic depth connecting the san bernardino strand and coachella valley segment of the san andreas fault zone we speculate that this is because the 3 km of right slip on the san bernardino stand of the san andreas fault and coachella valley segment of the banning fault has not been sufficient to form a single new structure through the 15 to 20 km gap between the two previously unconnected segments this implies that large earthquake rupture on the san andreas fault may be inhibited from propagating through san gorgonio pass thus limiting the maximum magnitudes on the southern san andreas fault

a sensitivity analysis of meteoric infrasound 1 we perform a multicomponent sensitivity analysis of how the physical and dynamical parameters that characterize a meteor in fall affect the ground overpressure and period of a plausible emitted n wave signal the nonlinear propagation model used throughout is based upon whitham s nonlinearization method which is modified to take into account a stratified atmosphere we use sensitivity indices derived using a fourier amplitude sensitivity test to measure how the meteor parameters uncertainties affect the uncertainty in the overpressure and period of an emitted n wave the investigated parameters include the azimuth entry angle diameter drag coefficient density and initial velocity of the meteor as well as the atmosphere the method is used to re examine the crater forming meteorite fall near carancas peru 2007 we obtain good agreement between the simulated signals and observed waveforms it is shown that ground overpressure uncertainty depends on the atmospheric uncertainties that are strongly correlated with the unknown trajectory whereas the period is governed by the diameter uncertainties finally we consider new waveform parameters that help characterize the meteor

effects of aridity and vegetation on plant wax δd in modern lake sediments we analyzed the deuterium composition of individual plant waxes in lake sediments from 28 watersheds that span a range of precipitation d h vegetation types and climates the apparent isotopic fractionation ea between plant wax n alkanes and precipitation differs with watershed ecosystem type and structure and decreases with increasing regional aridity as measured by enrichment of 2 h and 18 o associated with evaporation of lake waters the most negative ea values represent signatures least affected by aridity these values were 125 5 for tropical evergreen and dry forests 130 for a temperate broadleaf

the 2013 russian fireball largest ever detected by ctbto infrasound sensors 1 on 15 february 2013 a large earth impacting fireball disintegrated over the ural mountains this extraordinary event is together with the 1908 tunguska fireball among the most energetic events ever instrumentally recorded it generated infrasound returns after circling the globe at distances up to 85 000 km and was detected at 20 infrasonic stations of the global international monitoring system ims for the first time since the establishment of the ims infrasound network multiple arrivals involving waves that traveled twice round the globe have been clearly identified a preliminary estimate of the explosive energy using empirical period yield scaling relations gives a value of 460 kt of tnt equivalent in the context of the future verification of the comprehensive nuclear test ban treaty this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost 3 days as well as for calibrating the performance of the ims network

aliphatic hydrocarbons and triterpenes of the congo deep sea fan abstract hydrocarbons were analyzed in sediments from the congo river deep sea fan from the congo river and in sinking particles collected by sediment traps 40 m above the sediment studied sites encompassed three lobes of decreasing age of formation along the canyon sites a f and c and a another lobe system disconnected from the active channel since 4 ka site e terrestrial long chain odd n alkanes were dominant in all sediments of the lobe system unsaturated terpenoids sourced by higher plants such as gammacerene lupene ursene and oleanene were also detected at site c characterized by high accumulation rates 10 20 cm yr 1 the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations 10 17 g g oc 1 evidenced recent terrestrial and phytoplanktonic remains reworked in anaerobic conditions in these sediments organic carbon normalized concentrations of terrestrial alkanes and terpenoids were several fold higher than in the lobe sediments with lower accumulation rates sites a and f arguing for a more rapid degradation of terrestrial hydrocarbons than bulk organic carbon in the first steps of pre diagenesis ample variations in the contributions of biomarkers from higher plants ferns bacteria and angiosperms indicate an heterogeneous contribution of the soil and vegetation detritus delivered to the congo lobe sediments lower concentrations in terrestrial hydrocarbons at site e 45 km away from the active canyon indicated that river particles are still admixed to the dominant marine organic matter diploptene and hop 7 21 ene have a dual origin from terrestrial and marine microorganisms scatter in their relationship to gammacerene argues for a contribution of marine microorganisms in addition to soils sourced microorganisms the close distribution patterns of diploptene hop 21 ene hop 7 21 ene and neohop 13 18 ene is in line with the hypothesis of sequential clay catalyzed isomerisation of bacterial hopenes terrestrial biomarker accumulation fluxes at site c are one order of magnitude higher than vertical pelagic flux demonstrating the magnitude of the inputs delivered through turbiditic transport in the submarine canyon crude oil contamination was evidenced at the disconnected site e ucm c 21 to c 26 tricyclic diterpanes cpi and in smaller amounts in some sediments from sites a and c it may be related to marine crude oil extraction and transport a short chain mode of alkanes with an even predominance is evidenced in sediments of the lobe complex and likely sources crude oil microorganisms and ferns are discussed

response of the amazon rainforest to late pleistocene climate variability abstract variations in amazonian hydrology and forest cover have major consequences for the global carbon and hydrological cycles as well as for biodiversity yet the climate and vegetation history of the lowland amazon basin and its effect on biogeography remain debated due to the scarcity of suitable high resolution paleoclimate records here we use the isotopic composition d and 13 c of plant waxes from a high resolution marine sediment core collected offshore the amazon river to reconstruct the climate and vegetation history of the integrated lowland amazon basin for the period from 50 000 to 12 800 yr before present our results show that d values from the last glacial maximum were more enriched than those from marine isotope stage mis 3 and the present day we interpret this trend to reflect long term changes in precipitation and atmospheric circulation with overall drier conditions during the last glacial maximum our results thus suggest a dominant glacial forcing of the climate in lowland amazonia in addition to previously suggested thermodynamic mechanisms of precipitation change which are directly related to temperature we conclude that changes in atmospheric circulation are crucial to explain the temporal evolution of amazonian rainfall variations as demonstrated in climate model experiments our vegetation reconstruction based on 13 c values shows that the amazon rainforest was affected by intrusions of savannah or more open vegetation types in its northern sector during heinrich stadials while it was resilient to glacial drying this suggests that biogeographic patterns in tropical south america were affected by heinrich stadials in addition to glacial interglacial climate variability

the moravka meteorite fall 2 interpretation of infrasonic and seismic data the sound production from the mora vka fireball has been examined in detail making use of infrasound and seismic data a detailed analysis of the production and propagation of sonic waves during the atmospheric entry of the mora vka meteoroid demonstrates that the acoustic energy was produced both by the hypersonic flight of the meteoroid producing a cylindrical blast wave and by individual fragmentation events of the meteoroid which acted as small explosions producing quasi spherical shock waves the deviation of the ray normals for the fragmentation events was found to be as much as 30 beyond that expected from a purely cylindrical line source blast the main fragmentation of the bolide was confined to heights above 30 km with a possible maximum in acoustic energy production near 38 km seismic stations recorded both the direct arrival of the airwaves the strongest signal as well as air coupled p waves and rayleigh waves earlier signals in addition deep underground stations detected the seismic signature of the fireball the seismic data alone permit reconstruction of the fireball trajectory to a precision on the order of a few degrees the velocity of the meteoroid is much less well determined by these seismic data the more distant infrasonic station detected 3 distinct signals from the fireball identified as a thermospheric return a stratospheric return and an unusual mode propagating through the stratosphere horizontally and then leaking to the receiver

holocene provenance shift of suspended particulate matter in the amazon river basin abstract the strontium sr neodymium nd and lead pb isotope signatures of suspended particulate matter spm in rivers reflect the radiogenic isotope signatures of the rivers drainage basin these signatures are not significantly affected by weathering transport or depositional cycles but document the sedimentary contributions of the respective sources we report new sr nd and pb isotope ratios and element concentrations of modern spm from the brazilian amazon river basin and document the past evolution of the basin by analyzing radiogenic isotopes of a marine sediment core from the slope off french guiana archiving the last 40 kyr of amazon river spm and the holocene section of sediment cores raised between the amazon river mouth and the slope off french guiana the composition of modern spm confirms two main source areas the andes and the cratonic shield in the marine sediment core notable changes occurred during the second phase of heinrich stadial 1 i e increased proportion of shield rivers spm and during the last deglaciation i e increased proportion of madeira river spm together with elsewhere constant source contributions furthermore we report a prominent offset in sr and nd isotopic composition between the average core value end 11 7 0 9 2sd 87sr 86sr 0 7229 0 0016 2sd and the average modern amazon river spm signal end 10 5 0 5 2sd 87sr 86sr 0 7213 0 0036 2sd we suggest that a permanent change in the amazon river basin sediment supply during the late holocene to a more andean dominated spm was responsible for the offset

grain size control of river suspended sediment geochemistry clues from amazon river depth profiles residual solid products of erosion display a wide range of size density shape mineralogy and chemical composition and are hydrodynamically sorted in large river channels during their transport we characterize the chemical and isotopic variability of river sediments of the amazon basin collected at different water depths as a function of grain size absolute chemical concentrations and sr and nd isotopic ratios greatly varies along channel depth the al si ratio tightly linked to grain size distribution systematically decreases with depth mostly reflecting dilution by quartz minerals a double normalization diagram is proposed to correct from dilution effects elements define fan shaped patterns and can be classified in three different groups with respect to hydrodynamic sorting during transport in the amazon 1 poorly sorted insoluble elements like al fe th and rees 2 well sorted insoluble elements like zr and ti mainly carried by heavy minerals and 3 alkali na to cs and alkali earth elements mg to ba for which a large variety of patterns is observed related for alkali to their variable affinity for phyllosilicates sr isotopes show that the amazon river at the mouth is stratified the madeira and solimoes derived sediments being preferentially transported near the channel surface and at depth respectively the comparison between the solimoes and madeira rivers shows how the interplay between grain sorting weathering and crustal composition controls the composition of the suspended river sediments

the moravka meteorite fall 1 description of the events and determination of the fireball trajectory and orbit from video records the moravka czech republic meteorite fall occurred on may 6 2000 11 52 ut during the daytime six h56 ordinary chondrites with a total mass of 1 4 kg were recovered the corresponding fireball was witnessed by thousands of people and also videotaped by 3 casual witnesses sonic booms were recorded by 16 seismic stations in the czech republic and poland and by one infrasonic station in germany a total of 2 5 of the fireball eyewitnesses reported electrophonic sounds satellites in earth orbit detected part of the fireball light curve in this first paper from a series of 4 papers devoted to the morvka meteorite fall we describe the circumstances of the fall and determine the fireball trajectory and orbit from calibrated video records moravka becomes one of only 6 meteorites with a known orbit the slope of the trajectory was 20 4 to the horizontal the initial velocity was 22 5 km s and the terminal height of the fireball was 21 km the semimajor axis of the orbit was 1 85 au the perihelion distance was 0 982 au and the inclination was 32 2 the fireball reached an absolute visual magnitude of 20 at a height of 33 km

comparison of seismic waveform inversion results for the rupture history of a finite fault application to the 1986 north palm springs california earthquake the july 8 1986 north palm springs earthquake is used as a basis for comparison of several different approaches to the solution for the rupture history of a finite fault the inversion of different waveform data is considered both teleseismic p waveforms and local strong ground motion records linear parametrizations for slip amplitude are compared with nonlinear parametrizations for both slip amplitude and rupture time inversions using both synthetic and empirical green s functions are considered in general accurate green s functions are more readily calculable for the teleseismic problem where simple ray theory and flat layered velocity structures are usually sufficient however uncertainties in the variation in t with frequency most limit the resolution of teleseismic inversions a set of empirical green s functions that are well recorded at teleseismic distances could avoid the uncertainties in attenuation in the inversion of strong motion data the accurate calculation of propagation path effects other than attenuation effects is the limiting factor in the resolution of source parameters the assumption of a laterally homogeneous velocity structure is usually not a good one and the use of empirical green s functions is desirable considering the parametrization of the problem any degree of fault rupture complexity can be described in terms of a linear parametrization for slip amplitudes however a nonlinear parametrization for rupture times and slip amplitudes can have a distinct advantage over a simple linear one by limiting the number of unknown parameters regardless of the choice of data or the type of parametrization the model or solution will be affected by the choice of minimization norm and the type of stabilization used

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

a north to south transect of holocene southeast atlantic continental margin sediments relationship between aerosol transport and compound specific δ13c land plant biomarker and pollen records 1 we examined near surface late holocene deep sea sediments at nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s along the southwest african continental margin contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 are indicators of land plant vegetation of different biosynthetic types which can be correlated with concentrations and distributions of pollen taxa in the same sediments calculated clusters of wind trajectories and satellite aerosol index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites this multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent dust and smoke aerosols are mainly derived from the western and central south african hinterland dominated by deserts semi deserts and savannah regions rich in c4 and cam plants the northern sites congo fan area and northern angola basin which get most of their terrestrial material from the congo basin and the angolan highlands may also receive some material from the chad region very little aerosol from the african continent is transported to the most southerly sites in the cape basin as can be expected from the present position of the phytogeographic zones the carbon isotopic signatures of the n alkanes and n alkanols both become isotopically more enriched in 13c from north to south the results of the study suggest that this combination of pollen data and compound specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments

n alkane parameters from a deep sea sediment transect off southwest africa reflect continental vegetation and climate conditions abstract an isobathic transect of marine surface sediments from 1 n to 28 s off southwest africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n alkanes as proxies for continental vegetation and climate conditions we found a strong increase in the n c 29 33 weighted mean average 13 c values from 33 near the equator to around 26 further south additionally c 25 35 n alkanes reveal a southward trend of increasing average chain length from 30 0 to 30 5 the data reflect the changing contribution of plants employing different photosynthetic pathways c 3 and c 4 and or being differently influenced by the environmental conditions of their habitat the c 4 plant proportions calculated from the data ca 20 for rivers draining the rainforest to ca 70 at higher latitude correspond to the c 4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows furthermore the c 4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas suggesting that the c 4 plant fraction in marine sediments can be used to assess these environmental parameters

origin of increased terrigenous supply to the ne south american continental margin during heinrich stadial 1 and the younger dryas we investigate the redistribution of terrigenous materials in the northeastern ne south american continental margin during slowdown events of the atlantic meridional overturning circulation amoc the compilation of stratigraphic data from 108 marine sediment cores collected across the western tropical atlantic shows an extreme rise in sedimentation rates off the parnaiba river mouth about 2 s during heinrich stadial 1 hs1 18 15 ka sediment core geob16206 1 raised offshore the parnaiba river mouth documents relatively constant 143nd 144nd values expressed as end 0 throughout the last 30 ka whereas the homogeneous end 0 data support the input of fluvial sediments by the parnaiba river from the same source area directly onshore the increases in fe ca al si and rb sr during hs1 indicate a marked intensification of fluvial erosion in the parnaiba river drainage basin in contrast the end 0 values from sediment core geob16224 1 collected off french guiana about 7 n suggest amazon sourced materials within the last 30 ka we attribute the extremely high volume of terrigenous sediments deposited offshore the parnaiba river mouth during hs1 to i an enhanced precipitation in the catchment region and ii a reduced north brazil current which are both associated with a weakened amoc

d h variation in terrestrial lipids from santa barbara basin over the past 1400 years a preliminary assessment of paleoclimatic relevance we analyzed d h ratios of common terrestrial leaf wax lipids in a 1400 year sediment core from the santa barbara basin sbb to test whether they accurately record terrestrial climate in southern california the d h ratios of long chain n alkanes vary substantially with depth but are poorly correlated with other terrestrial climate proxies interference from fossil hydrocarbons may be at least partly responsible long chain n alkanoic acids exhibit nearly constant downcore d h ratio values this constancy in the face of known climatic shifts presumably reflects a substantial residence time for leaf wax compounds in terrestrial soil and or on the basin flanks alternatively the isotopic composition of meteoric waters in southern california may not covary with climate particularly aridity however the d values of n c22 and n c24 fatty acids commonly attributed to terrestrial aquatic sources are partially correlated with southern california winter palmer drought severity index a tree ring based climatic proxy r 2 0 25 p 0 01 on multi centennial scales with an inferred ca 215 year time lag the improved correlation of these biomarkers can be explained by the fact that they are not stored in terrestrial soil nor are subject to interference from fossil hydrocarbons our study indicates that the sbb is unlikely to preserve high resolution leaf wax d h records that can serve as quantitative paleoclimate proxies though some qualitative information may be retained more generally the sources of lipids in marginal marine basins need to be carefully evaluated prior to attempting paleoclimate reconstruction based on the leaf wax d h proxy

evidence for a meteoritic origin of the september 15 2007 carancas crater on september 15th 2007 around 11 45 local time in peru near the bolivian border the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations soon after a crater was discovered south of lake titicaca these events have been detected by the bolivian seismic network and two infrasound arrays operating for the comprehensive nuclear test ban treaty organization situated at about 80 and 1620 km from the crater the localization and origin time computed with the seismic records are consistent with the reported impact the entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and backazimuths from the crater diameter and the airwave amplitudes the kinetic energy mass and explosive energy are calculated using the estimated velocity of the meteoroid and similarity criteria between orbital elements an association with possible parent asteroids is attempted the favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded

alberta bolide of june 1 1982 interpretation of photographic and seismic records passage of a bright bolide northeast of edmonton near midnight on the evening of june 1 1982 was recorded both photographically by three cameras of the meteorite observation and recovery project of the national research council of canada and by seismic recording stations at edmonton and cold lake the photographic data indicate a path towards the northwest at an average height of about 80 km and an average speed of 28 km s the cold lake data make possible the determination of direction and velocity of approach of the sound wave as well as wave front curvature in the horizontal plane the data indicate an essentially zero curvature and a speed across the array of 337 8 m s for the sound arrival wave front curvature indicates a line source being the nearly cylindrical shock wave from the hypervelocity bolide directions of approach at both cold lake and edmonton however seem to indicate a direction more consistent with the end of the brightest segment of the meteor photograph the discrepancy is not re

a joint seismic and acoustic study of the washington state bolide observations and modeling 1 on 3 june 2004 a bolide was observed over british columbia washington oregon and idaho in addition to eyewitness accounts the event was recorded on videotape and at 100 seismometers located in washington state and southern british columbia seismic records are consistent with a terminal burst rather than the hypersonic shock of the meteors passage through the atmosphere arrival times from seismic waveform data are used to obtain an accurate source location for this terminal burst the source location can effectively be considered to be ground truth for assessing current atmospheric models and infrasound propagation algorithms we observe clear infrasonic signals associated with the terminal burst of the fireball at infrasound stations i56us and i57us in washington state and california respectively at i56us we observe at least four distinct acoustic arrivals for which we are able to model three using a state of the art atmospheric model the ground to space g2s model and both ray tracing and parabolic equation propagation algorithms to our knowledge this is the first study in which a complex sequence of arrival packets at an individual station has been successfully modeled by range dependent ducting and specular reflection off terrain gradients at i57us a single coherent acoustic signal was observed which we are unable to satisfactorily model this could be due to errors in the specification of the background atmosphere incorrect assumptions and approximations inherent to the acoustic propagation algorithms and the greater range of propagation which amplifies the effect of errors in source location and the atmospheric specifications

an entry model for the tagish lake fireball using seismic satellite and infrasound records we present instrumental observations of the tagish lake fireball and interpret the observed characteristics in the context of two different models of ablation from these models we estimate the pre atmospheric mass of the tagish lake meteoroid to be 56 tonnes and its porosity to be between 37 and 58 with the lowest part of this range most probable these models further suggest that some 1300 kg of gram sized or larger tagish lake material survived ablation to reach the earth s surface representing an ablation loss of 97 for the fireball satellite recordings of the tagish lake fireball indicate that 1 1 1012 j of optical energy were emitted by the fireball during the last 4 s of its flight the fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16 infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1 66 0 70 kt tnt equivalent energy the fraction of this total energy converted to acoustic signal energy is found to be between 0 10 and 0 23 examination of the seismic recordings of the airwave from tagish lake have established that the acoustic energy near the sub terminal point is converted to seismic body waves in the upper most portion of the earth s crust the acoustic energy to seismic energy coupling efficiency is found to be near 10 6 for the tagish lake fireball the resulting energy estimate is near 1 7 kt corresponding to a meteoroid 4 m in diameter the seismic record indicates extensive nearly continuous fragmentation of the body over the height intervals from 50 to 32 km seismic and infrasound energy estimates are in close agreement with the pre atmospheric mass of 56 tonnes established from the modeling the observed flight characteristics of the tagish lake fireball indicate that the bulk compressive strength of the pre atmospheric tagish lake meteoroid was near 0 25 mpa while the material compressive strength most appropriate to the recovered meteorites was closer to 0 7 mpa these are much lower than values found for fireballs of ordinary chondritic composition the behavior of the tagish lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids the bulk density and porosity results for the tagish lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble pile assemblages

complexities of the san andreas fault near san gorgonio pass implications for large earthquakes 1 geologic relationships and patterns of crustal seismicity constrain the three dimensional geometry of the active portions of san andreas fault zone near san gorgonio pass southern california within a 20 km wide contractional stepover between two segments of the fault zone the san bernardino and coachella valley segments folds and dextral reverse and dextral normal faults form an east west belt of active structures the dominant active structure within the stepover is the san gorgonio pass garnet hill faults a dextral reverse fault system that dips moderately northward within the hanging wall block of the san gorgonio pass garnet hill fault system are subsidiary active dextral and dextral normal faults these faults relate in complex but understandable ways to the strike slip faults that bound the stepover the pattern of crustal seismicity beneath these structures includes a 5 8 km high east west striking step in the base of crustal seismicity which corresponds to the downdip limit of rupture of the 1986 north palm springs earthquake we infer that this step has been produced by slip on the linked san gorgonio pass garnet hill coachella valley banning sgp gh cvb fault this association enables us to construct a structure contour map of the fault plane the large step in the base of seismicity downdip from the sgp gh cvb fault system probably reflects a several kilometers offset of the midcrustal brittle plastic transition u th he thermochronometry supports our interpretation that this south under north thickening of the crust has created the region s 3 km of topographic relief we conclude that future large earthquakes generated along the san andreas fault in this region will have a multiplicity of mostly specifiable sources having dimensions of 1 20 km two tasks in seismic hazard evaluation may now be attempted with greater confidence first the construction of synthetic seismograms that make useful predictions of ground shaking and second theoretical investigations of the role of this complexity in retarding the propagation of future seismic ruptures

the moravka meteorite fall 3 meteoroid initial size history structure and composition the properties and history of the parent meteoroid of the mora vka h5 6 ordinary chondrites have been studied by a combination of various methods the pre atmospheric mass of the meteoroid was computed from fireball radiation infrasound seismic signal and the content of noble gases in the meteorites all methods gave consistent results the best estimate of the pre atmospheric mass is 1500 500 kg the fireball integral bolometric luminous efficiency was 9 and the acoustic efficiency was 0 14 the meteoroid cosmic ray exposure age was determined to be 6 7 1 0 10 6 yr the meteorite shows a clear deficit of helium both 3 he and 4 he this deficit can be explained by solar heating numerical backward integration of the meteoroid orbit determined in a previous paper from video records of the fireball shows that the perihelion distance was probably lower than 0 5 au and possibly as low as 0 1 au 5 ma ago the collision which excavated mora vka probably occurred while the parent body was on a near earth orbit as opposed to being confined entirely to the main asteroid belt an overview of meteorite macroscopic properties petrology mineralogy and chemical composition is given the meteorites show all mineralogical features of h chondrites the shock level is s2 minor deviations from other h chondrites in abundances of trace elements la ce cs and rb were found the ablation crust is enriched with siderophile elements

surface water dynamics in the amazon basin application of satellite radar altimetry 1 satellite radar altimetry has the ability to monitor variations in surface water height stage for large wetlands rivers and associated floodplains a clear advantage is the provision of data where traditional gauges are absent as part of an international program a complete altimetric analysis of the amazon basin is being undertaken here an updated and more rigorous evaluation of the topex poseidon t p data set is presented for the first 7 5 years of the mission with an initial study group of 230 targets height variability at many ungauged locations can be observed for 30 50 the range reflecting the clarity of the variations in lieu of instrument limitations an assessment of the instrument performance confirms that the minimum river width attainable is 1 km in the presence of some inundated floodplain this constraint does allow observation of the main stem solimoes amazon and the larger tributaries but rugged terrain in the vicinity of the target additionally places severe limitations on data retrieval first order validation exercises with the deduced 1992 1999 time series of stage fluctuations reveal accuracies ranging from tens of centimeters to several meters mean 1 1 m rms altimetric water levels in the solimoes and amazon are particularly well defined with amplitudes 13 m and variations in peak level timing from may to july the water surface gradient of the main stem is found to vary both spatially and temporally with values ranging from 1 5 cm km downstream to 4 0 cm km for more upstream reaches in agreement with ground based estimates the seasonal variability of the gradients reveals that the hysteresis characteristic of the flood wave varies along the main stem and the derived altimetric velocity of this flood wave is estimated to be 0 35 m s overall the altimetric results demonstrate that the t p mission is successfully monitoring the transient flood waves of this continental scale river basin

slip complexity in earthquake fault models we summarize studies of earthquake fault models that give rise to slip complexities like those in natural earthquakes for models of smooth faults between elastically deformable continua it is critical that the friction laws involve a characteristic distance for slip weakening or evolution of surface state that results in a finite nucleation size or coherent slip patch size h models of smooth faults using numerical cell size properly small compared to h show periodic response or complex and apparently chaotic histories of large events but have not been found to show small event complexity like the self similar power law gutenberg richter frequency size statistics this conclusion is supported in the present paper by fully inertial elastodynamic modeling of earthquake sequences in contrast some models of locally heterogeneous faults with quasi independent fault segments represented approximately by simulations with cell size larger than h so that the model becomes inherently discrete do show small event complexity of the gutenberg richter type models based on classical friction laws without a weakening length scale or for which the numerical procedure imposes an abrupt strength drop at the onset of slip have h 0 and hence always fall into the inherently discrete class we suggest that the small event complexity that some such models show will not survive regularization of the constitutive description by inclusion of an appropriate length scale leading to a finite h and a corresponding reduction of numerical grid size

diagenesis of free and bound lipids in terrestrial detritus deposited in a lacustrine sediment recent sediments from an oligotrophic lake loch clair having uniform organic input for 2000 yr show changes in lipid abundance and composition with increasing depth attributed to diagenesis stability of free lipids decreases in the order n alkanes alkan 2 ones sterols n alkanoic acids n alkanols n alkenoic acids diagenetic loss of shorter chain homologues is complete within 400 yr stabilisation of bound relative to free lipids increases the proportion of the former with sediment age and reduces loss of shorter chain bound homologues in an eutrophic lake cross mere shorter chain free and bound sedimentary lipids show increased abundance compared with loch clair the relative importance of higher input of shorter chain lipids derived from aquatic detritus and slower initial diagenesis due to the anoxic hypolimnion as causative factors for this difference between lake types cannot yet be assessed

geodetic estimate of coseismic slip during the 1989 loma prieta california earthquake offsets in the relative positions of geodetic stations resulting from the loma prieta earthquake can be explained with a dislocation model that includes buried oblique slip on a rupture surface extending 37 km along the strike of the san andreas fault dipping 70 degree to the sw and extending from a depth of about 5 to 17 5 km assuming uniform slip on a rectangular surface the mean values for a range of reasonable fault geometries are 1 6 plus minus 0 3 m right lateral strike slip and 1 2 plus minus 0 3 m reverse slip slip on an adjacent extension of the rupture to the southeast recorded in the aftershock sequence is not well constrained by the geodetic data the geodetic data clearly preclude rupture extending near the surface

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

distribution of fluid muds on the amazon continental shelf abstract a comprehensive study of suspended sediment transport on the amazon shelf was conducted as part of the amasseds project a multidisciplinary amazon shelf sediment study to understand the link between physical processes and the fate of amazon river sediment a small instrumented tripod was used to measure the fluid flow and suspended sediment characteristics throughout the water column on varying time scales e g semidiurnal fortnightly seasonal dense nearbed suspensions or fluid muds suspended sediment concentration 10 g l on the order of a few meters in thickness were found on the inner and middle shelf covering an area ranging from 5 700 km2 during falling and low river discharge to 10 000 km2 during rising and high discharge fluid muds generally observed in the region of bottom salinity fronts extend across the topset beds to the foreset beds during rising and high discharge salinity and temperature anomalies frequently observed in fluid muds imply that often the muds do not result from erosion and resuspension from the seabed but from trapping processes at the bottom salinity front and transport across the shelf the vertical structure of fluid mud varies in space and tune variability close to the river mouth is predominantly fortnightly related to the location and structure of the bottom salinity front on the open shelf the variability appears to be related to seasonal differences in river and sediment discharge and the location of the bottom salinity front the total suspended sediment inventory on the shelf during the season of high discharge is approximately equal to the annual sediment discharge from the river 1 2 109 tons yr and 90 of that inventory is within fluid mud suspended sediment transport on the shelf is dominated by fluid mud

seismic observations of meteors coupling theory and observations to date coupling of acoustic waves directly with the earth s surface represents the bulk of the observed meteor related seismic signals while precursory and impact related seismic waves remain an observational rarity with proliferation of infrasound and seismic monitoring systems new opportunities exist to explore the relationship between earth s atmosphere andsurface continued studyofmeteorseismologywillleadto new methods to constrain energies sizes and fluxes for moderately cm to m sized meteoroids on earth and potentially on mars

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

a 60 000 year record of hydrologic variability in the central andes from the hydrogen isotopic composition of leaf waxes in lake titicaca sediments abstract a record of the hydrogen isotopic composition of terrestrial leaf waxes d wax in sediment cores from lake titicaca provides new insight into the precipitation history of the central andes and controls of south american summer monsoon sasm variability since the last glacial period comparison of the d wax record with a 19 kyr d record from the nearby illimani ice core supports the interpretation that precipitation d is the primary control on d wax with a lesser but significant role for local evapotranspiration and other secondary influences on d wax the titicaca d wax record confirms overall wetter conditions in the central andes during the last glacial period relative to a drier holocene during the last deglaciation abrupt d wax shifts correspond to millennial scale events observed in the high latitude north atlantic with dry conditions corresponding to the bolling allerod and early holocene periods and wetter conditions during late glacial and younger dryas intervals we observe a trend of increasing monsoonal precipitation from the early to the late holocene consistent with summer insolation forcing of the sasm but similar hydrologic variability on precessional timescales is not apparent during the last glacial period overall this study demonstrates the relative importance of high latitude versus tropical forcing as a dominant control on glacial sasm precipitation variability

hydrogen isotope ratios of lacustrine sedimentary n alkanes as proxies of tropical african hydrology insights from a calibration transect across cameroon abstract hydrogen isotope values d of sedimentary aquatic and terrestrial lipid biomarkers originating from algae bacteria and leaf wax have been used to record isotopic properties of ancient source water i e precipitation and or lake water in several mid and high latitude lacustrine environments in the tropics however where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes calibration studies for this proxy are not yet available to close this gap of knowledge we sampled surface sediments from 11 lakes in cameroon to identify those hydro climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers here we present a robust framework for the application of compound specific hydrogen isotopes in tropical africa our results show that the d values of the aquatic lipid biomarker n c17 alkane were not correlated with the d values of lake water carbon isotope measurements indicate that the n c17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis we demonstrate that the d values of the n c29 alkane were correlated with the d values of surface water i e river water and groundwater which on large spatial scales reflect the isotopic composition of mean annual precipitation such a relationship has been observed at higher latitudes supporting the robustness of the leaf wax lipid d proxy on a hemispheric spatial scale in contrast the d values of the n c31 alkane did not show such a relationship but instead were correlated with the evaporative lake water d values this result suggests distinct water sources for both leaf wax lipids most likely originating from two different groups of plants these new findings have important implications for the interpretation of long chain n alkane d records from ancient lake sediments in particular a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and or growth form of organisms and therefore the source of hydrogen used during lipid biosynthesis

the hill of six lakes revisited new data and re evaluation of a key pleistocene amazon site the new analyses of a sedimentary record of lake pata in the hill of six lakes in nw amazon and its correlation with other quaternary proxy records in the region provide new insights regarding the vegetation and climate of the lowland forest during the last glacial despite what has been reported previously in the literature the sedimentary and pollen records are not continuous the hill remained forested however clear signals of structural change are seen in the record which indicate that the area experienced a significantly drier climate during the last glacial maximum lgm the herbs and taxa that are known to be more dominant in seasonally dry forests were all more abundant during the glacial part of the record and the cool adapted elements were mixed with warm lowland elements which indicates a temperature depression a comparison of the palaeoecological data with other regional geoenvironmental records of the upper negro river basin and other areas of the amazon provides additional support for a cooler and more seasonal environment during the middle pleniglacial which then became drier during the lgm a wet lgm is strongly refuted therefore the palaeoclimatic and ecological models that used the previous proxy data from six lakes to sustain wet conditions and a continuous forest record during the lgm to reconstruct the palaeoenvironmental conditions in the amazon should be reviewed

origin transport and deposition of leaf wax biomarkers in the amazon basin and the adjacent atlantic paleoenvironmental studies based on terrigenous biomarker proxies from sediment cores collected close to the mouth of large river systems rely on a proper understanding of the processes controlling origin transport and deposition of biomarkers here we contribute to the understanding of these processes by analyzing long chain n alkanes from the amazon river system we use the dd composition of long chain n alkanes from river bed sediments from the amazon river and its major tributaries as well as marine core top samples collected off northeastern south america as tracers for different source areas the d13c composition of the same compounds is used to differentiate between long chain n alkanes from modern forest vegetation and petrogenic organic matter our d13c results show depleted d13c values 33 to 36 in most samples indicating a modern forest source for most of the samples enriched values 31 to 33 are only found in a few samples poor in organic carbon indicating minor contributions from a fossil petrogenic source long chain n alkane dd analyses show more depleted values for the western tributaries the madeira and solimoes rivers 152 to 168 while n alkanes from the lowland tributaries the negro xingu and tocantins rivers 142 to 154 yield more enriched values the n alkane dd values thus reflect the mean annual isotopic composition of precipitation which is most deuterium depleted in the western amazon basin and more enriched in the eastern sector of the basin samples from the amazon estuary show a mixed long chain n alkane dd signal from both eastern lowland and western tributaries marine core top samples underlying the amazon freshwater plume yield dd values similar to those from the amazon estuary while core top samples from outside the plume showed more enriched values although the variability in the river bed data precludes quantitative assessment of relative contributions our results indicate that long chain n alkanes from the amazon estuary and plume represent an integrated signal of different regions of the onshore basin our results also imply that n alkanes are not extensively remineralized during transport and that the signal at the amazon estuary and plume includes refractory compounds derived from the western sector of the basin these findings will aid in the interpretation of plant wax based records of marine sediment cores collected from the adjacent ocean

oblique slip slip partitioning spatial and temporal changes in the regional stress field and the relative strength of active faults in the basin and range western united states when viewed with stress transformation laws and an idealized physical model observations of oblique slip and slip partitioning in the basin and range western united states are interpreted to show that 1 separate regions with the same net extension direction are not necessarily characterized by the same regional stress field 2 fault systems exhibiting partitioning where one of the faults is near vertical generally do not require temporal changes in the stress field to explain the disparate slip vectors on the adjacent faults and 3 the relative strengths of active fault zones may vary by more than an order of magnitude

evolution of the santa cruz mountains california through tectonic growth and geomorphic decay i describe a strategy for modeling a specific large scale topographic feature that recognizes the discrepancy between tectonic and geomorphic scales and allows for important feedbacks between these processes in the geomorphic model the largest channel in each 4 4 km cell is explicitly treated the channel incision being driven by a stream power rule hillslopes internal to each cell respond rapidly to incision of the local channel prompting their treatment in the model as steady state forms i present analytic expressions for the local relief which is controlled by the local channel incision rate and rate constants associated with the dominant hillslope process either diffusive or landsliding initial conditions include any preexisting topography and a lightly etched a channel network the model is illustrated using the santa cruz mountains california i show that an earlier hypothesis that the santa cruz mountains are due to advection of topography past an uplift source related to a restraining bend in the san andreas fault remains viable when more specific geomorphic processes are considered the local tectonics are represented by crustal thickening necessitated by conservation of mass in the bend right lateral translation of crust with respect to the bend and flexural response to the distributed load the model produces reasonable geographic and statistical distributions of topography using rates of tectonic and geomorphic processes that are within the range of those measured locally this argues that this restraining bend is a long lived feature of the san andreas fault the slightly higher crest and shorter length of the southern santa cruz mountains may potentially be explained by slightly faster slip of the crust west of the fault with respect to the bend than of that to the east deflection is minimal beneath these relatively small mountains disallowing the interesting feedback of erosionally driven uplift the predicted pattern of exhumation could be used to guide the search for fission track sites that could aid in the testing of the model

the provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the ganges brahmaputra rivers organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere in order to use sedimentary records to reconstruct past environmental conditions on the continents such as vegetation cover and type or precipitation intensity we need to understand the provenance of the organic signatures and how they are transferred and potentially modified by fluvial transport to the sedimentary reservoir in particular we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern day ganges and brahmaputra river complex one of the largest fluvial systems on earth the distribution of n alkanes and n alkanoic acids in ganges brahmaputra river sediments suggests that vascular plant inputs are consistently a significant component of the organic carbon pool molecular 13c measurements reveal that c3 vegetation inputs delivered by the himalayan rivers are partly degraded and replaced by mixed c3 c4 vegetation input in the floodplain the hydrogen isotopic composition of long chain c24 n alkanoic acids in combination with their stable c isotopic composition provides constraints on the isotopic composition of the environmental water used by higher plants within the drainage basin calculated compositions compare well with the depleted d isotopic ratios of the river water during the summer monsoon suggesting that h isotopic compositions of long chain alkanoic acids are a valuable proxy for the composition of summer monsoon moisture in the ganges brahmaputra basin detailed studies of the isotopic anatomy of modern river systems are critical for informed interpretation of marine sedimentary records in river influenced continental margins

tilt and northward offset of cordilleran batholiths resolved using igneous barometry considerable controversy surrounds the suggestion based on palaeomagnetic evidence that large segments of the north american cordillera travelled long distances parallel to the coast during the latest cretaceous and early tertiary periods well after the amalgamation of exotic terranes discordant palaeomagnetic data from mid cretaceous plutonic rocks of the peninsular ranges batholith of coastal southern california and baja and the mount stuart batholith of the cascade range in washington play a pivotal role in the controversy the discordant data were originally interpreted to reflect northward transport of 1 000 km relative to cratonal north america after the batholiths cooled through their magnetic blocking temperatures1 5 more recently it has been argued that the discordances arise from local tilting of batholiths rather than northward offset6 7 here we present and implement new methods based on hornblende barometry8 for determining the palaeohorizontal in granitic batholiths and correcting palaeomagnetic data for tilting our results indicate that the peninsular ranges and mount stuart batholiths have undergone northward offsets of 1 000 450 and 2 900 700 km respectively and also significant tilting

calibrating infrasonic to seismic coupling using the stardust sample return capsule shockwave implications for seismic observations of meteors 1 shock waves produced by meteoroids are detectable by seismograph networks but a lack of calibration has limited quantitative analysis of signal amplitudes we report colocated seismic and infrasound observations from reentry of nasa s stardust sample return capsule ssrc on 15 january 2006 the velocity of the ssrc initially 12 5 km s was the highest ever for an artificial object lying near the low end of the 11 2 72 km s range typical of meteoroids our infrasonic seismic recordings contain an initial n wave produced by the hypersonic shock front followed 10 s later by an enigmatic series of weak secondary pulses the seismic signals also include an intervening dispersed wave train with the characteristics of an air coupled rayleigh wave we determine an acoustic seismic coupling coefficient of 7 3 0 2 m ms 1 pa this represents an energy admittance of 2 13 0 15 several orders of magnitude larger than previous estimates derived from earthquake or explosive analogs theoretical seismic response was computed using in situ vp and vs measurements together with laboratory density measurements from samples of the clay rich playa treatment of the air ground interface as an idealized air solid contact correctly predicts the initial pulse shape but underestimates its seismic amplitude by a factor of 2 full wave synthetic seismograms simulate the air coupled rayleigh wave and suggest that the secondary arrivals are higher order airy phases part of the infrasound signal appears to arise from coupling of ground motion into the air much like earthquake induced sounds

the spitak armenia earthquake of 7 december 1988 field observations seismology and tectonics the epicentre of the destructive earthquake that devastated northern armenia the strongest in the region since historical times is located within the lesser caucasus a mountain country subjected to north south compression by the push of the arabian plate a french soviet field expedition studied surface breaks and aftershock activity the fault scarp could be followed for 13 kilometres and showed a reverse dislocation of 1 6 metres aftershocks are shallower than 13 kilometres and delimit a ruptured surface of about 300km2

the m2 tide on the amazon shelf as part of a multidisciplinary amazon shelf sediment study amasseds moored and shipboard current measurements made over the amazon shelf during 1990 1991 have been analyzed to determine the dominant semidiurnal tidal constituent the m2 these results have been combined with coastal sea level data from within the amazon and para rivers the adjacent shelf and with satellite derived tidal elevation data from off the shelf to provide a more complete description of the m2 tide in this complex river shelf system near the amazon river mouth the m2 tide propagates across the shelf and through the mouth as a damped progressive wave with its amplitude decreasing and phase increasing upriver over the adjacent shelf north of cabo norte the m2 tide approaches a damped standing wave with large amplitudes greater than 1 5 m near the coast due to near resonance within the coastal embayment formed by the cabo norte shoal to the south and cabo cassipore to the north the observed m2 tidal currents are nearly rectilinear and oriented primarily across the local isobaths comparisons between tidal observations in both the north channel and the cabo norte cabo cassipore embayment and a simple variable width channel tidal model indicate that 1 most of the m2 tidal energy dissipation occurs over the mid and inner shelf in water depths less than 20 m and 2 fluid muds found there cause a significant reduction of order 50 in the effective bottom friction felt by the m2 tide the approximate resonant period of the cabo norte cabo cassipore embayment is 11 9 hours and at resonance the average energy dissipation per forcing period is roughly 2 2 times the average mechanical energy in the embayment this damping rate is large enough that the tidal amplification is rather insensitive to forcing frequency so that the response of the embayment to forcing over the semidiurnal band should be essentially the same the vertical structure of the m2 tidal current is examined at one outer shelf site located in 65 m water depth the observed semimajor axis increases logarithmically with height above bottom within the lowest 1 2 m and reaches a maximum in excess of 0 5 m s at approximately 11 m above bottom the mean ellipticity is small less than 0 1 and positive indicating clockwise rotation of a nearly rectilinear current and the semimajor axis is oriented within 10 of the local cross isobath direction the m2 phase increases with height above bottom with flood at the bottom leading flood at the surface by about 1 hour a simple local homogeneous tidal model with time and space dependent eddy viscosity simulates the observed near bottom velocity reasonably well however the model suggests that stratification above the lowest few meters may significantly affect the tidal boundary layer structure at this site the m2 energy flux onto the amazon shelf and into the amazon and para rivers has been estimated using current and surface elevation data and the best fit variable width channel model results the net m2 energy flux into the mouths of the amazon and para rivers is 0 47 1010w and 0 19 1010w respectively a net m2 energy flux of about 3 3 1010w occurs onto the shelf between the north channel of the amazon river and cabo cassipore this stretch of the amazon shelf accounts for about 1 3 of the global dissipation of the m2 tide

carbon sedimentation at lago grande de curuai a floodplain lake in the low amazon region insights into sedimentation rates we studied recent organic carbon sedimentation in an amazonian floodplain using sediment trap samples and one core sediment traps were placed in several lakes of the lago grande de curuai floodplain during different water level phases the end of the period of water level reduction falling water and the start of the period of water level increase rising water vertical seasonal fluxes of settling particles sp are very difficult to estimate and interpret especially during falling water periods when the concentration of suspended matter in the water column is greater than during rising water periods probably due to resuspension processes vertical fluxes of settling particles sp varied between ca 4 and 2000 g m 2 day 1 fluxes of organic carbon ranged between 5 50 g c m 2 day 1 during the falling water and between 0 041 4 g c m 2 day 1 during the rising water the core is characterised by two laminated sedimentological units sediments in the upper unit which generally coarsens upwards are interpreted as a progradation sequence of the sand and silt flat at the entrance of an inflow channel where the core was collected this unit is composed of three sub units a superficial layer reworked by bioturbation a lower sub unit characterised by horizontal and sub horizontal laminations of fine sands and silts and a basal sub unit composed of horizontal laminations of fine silts and clays the lower unit is characterised by horizontal and sub horizontal laminations of fine sands and silts and corresponds to the top of an older accumulating sequence these changes show that the sedimentary environment is very dynamic at the centennial scale sedimentation rates generally ranged between 0 42 and 1 34 cm year 1 and were estimated to range from 0 56 to 1 35 cm year 1 after normalisation for clay sized particles 4 m floodplain sediment accumulation generally varies between 0 42 1 16 and 1 10 g m 2 year 1 within the first second and third sub units respectively in the second unit the non supported 210pb date is close to the detection limit carbon content is relatively low around 1 sediment weight through the core although mean carbon accumulation rates are very high generally 100 g m 2 year 1 and peaking at 250 g m 2 year 1 these results suggest that amazon floodplain lakes may constitute an important sink for organic carbon

sources and distributions of branched and isoprenoid tetraether lipids on the amazon shelf and fan implications for the use of gdgt based proxies in marine sediments branched glycerol dialkyl glycerol tetraethers brgdgts in river fan sediments have been used successfully to reconstruct mean annual air temperature maat and soil ph of the congo river drainage basin however in a previous study of amazon deep sea fan sediments the reconstructed maats were ca 10 c colder than the actual maat of the amazon basin in this study we investigated this apparent offset by comparing the concentrations and distributions of brgdgts in amazon river suspended particulate matter spm and sediments to those in marine spm and surface sediments the riverine brgdgt input was evident from the elevated brgdgt concentrations in marine spm and surface sediments close to the river mouth the distributions of brgdgts in marine spm and sediments varied widely but generally showed a higher relative abundance of methylated and cyclic brgdgts than those in the river since this difference in brgdgt distribution was also found in intact polar lipid ipl derived brgdgts which were more recently produced the change in the marine brgdgt distribution was most likely due to marine in situ production consequently the maats calculated based on the methylation of branched tetraethers mbt and the cyclisation of branched tetraethers cbt were lower and the cbt derived ph values were higher than those of the amazon basin however spm and sediments from stations close to the river mouth still showed mbt cbt values that were similar to those of the river therefore we recommend caution when applying the mbt cbt proxy it should only be used in sediment cores that were under high river influence the influence of riverine derived isoprenoid gdgt isogdgt on the isogdgt based tex86 temperature proxy was also examined in marine spm and sediments an input of riverine isogdgts from the amazon river was apparent but its influence on the marine tex86 was minor since the tex86 of spm in the amazon river was similar to that in the marine spm and sediments

leaf wax biomarkers in transit record river catchment composition rivers carry organic molecules derived from terrestrial vegetation to sedimentary deposits in lakes and oceans storing information about past climate and erosion as well as representing a component of the carbon cycle it is anticipated that sourcing of organic matter may not be uniform across catchments with substantial environmental variability in topography vegetation zones and climate here we analyze plant leaf wax biomarkers in transit in the madre de dios river peru which drains a forested catchment across 4 5 km of elevation from the tropical montane forests of the andes down into the rainforests of amazonia we find that the hydrogen isotopic composition of leaf wax molecules specifically the c28 n alkanoic acid carried by this tropical mountain river largely records the elevation gradient defined by the isotopic composition of precipitation and this supports the general interpretation of these biomarkers as proxy recorders of catchment conditions however we also find that leaf wax isotopic composition varies with river flow regime over storm and seasonal timescales which could in some cases be quantitatively significant relative to changes in the isotopic composition of precipitation in the past our results inform on the sourcing and transport of material by a major tributary of the amazon river and contribute to the spatial interpretation of sedimentary records of past climate using the leaf wax proxy

exchanges of sediment between the flood plain and channel of the amazon river in brazil sediment transport through the brazilian sector of the amazon river valley a distance of 2010 km involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at obidos 1200 mt yr 1 the exchanges occur through bank erosion bar deposition settling from diffuse overbank flow and sedimentation in flood plain channels we estimated the magnitude of these exchanges for each of 10 reaches of the valley and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel the annual supply of sediment entering the channel from bank erosion was estimated to average 1570 mt yr 1 1 3 the obidos flux and the amount transferred from channel transport to the bars 380 mt yr 1 and the flood plain 460 mt yr 1 in channelized flow 1230 mt yr 1 in diffuse overbank flow totaled 2070 mt yr 1 1 7 the obidos flux thus deposition on the bars and flood plain exceeded bank erosion by 500 mt yr 1 over a 10 16 yr period sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 mt yr 1 over 16 yr crudely validating the process based calculations of the sediment budget which in turn illuminate the physical controls on each exchange process another 300 400 mt yr 1 are deposited in a delta plain downstream of obidos the components of the sediment budget reflect hydrologic characteristics of the valley floor and geomorphic characteristics of the channel and flood plain which in turn are influenced by tectonic features of the amazon structural trough

supracenter locating fireball terminal bursts in the atmosphere using seismic arrivals terminal bursts and fragmentations of meteoritic fireballs in the atmosphere may now be accurately located in four dimensions three spatial temporal using seismic arrival times of their acoustic waves recorded by seismometer camera microphone and or infrasound stations on the ground a computer program supracenter calculates travel times by ray tracing through realistic atmospheres that include winds and locates source positions by minimization of travel time residuals this is analogous to earthquake hypocenter location in the solid earth but is done through a variably moving medium inclusion of realistic atmospheric ray tracing has removed the need for the simplifying assumption of an isotropic atmosphere or an approximation to account for wind drift this drift is on the order of several km when strong unidirectional winds are present in the atmosphere at the time of a fireballs occurrence supracenter derived locations of three seismically recorded fireballs 1 the october 9 1997 el paso superbolide 2 the january 25 1989 mt adams fireball and 3 the may 6 2000 moravka fireball with its associated meteorite fall are consistent with and probably an improvement upon the locations derived from eyewitness photographic and video observations from the respective individual events if direct acoustic seismic arrivals can be quickly identified for a fireball event terminal burst locations and potentially trajectory geometry and velocity information can be quickly derived aiding any meteorite recovery efforts during the early days after the fall potentially seismic records may yield enough trajectory information to assist in the derivation of orbits for entering projectiles

northern hemisphere controls on tropical southeast african climate during the past 60 000 years the processes that control climate in the tropics are poorly understood we applied compound specific hydrogen isotopes d and the tex86 tetraether index of 86 carbon atoms temperature proxy to sediment cores from lake tanganyika to independently reconstruct precipitation and temperature variations during the past 60 000 years tanganyika temperatures follow northern hemisphere insolation and indicate that warming in tropical southeast africa during the last glacial termination began to increase 3000 years before atmospheric carbon dioxide concentrations d data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial scale events recorded in northern hemisphere monsoonal climate records this implies that precipitation in tropical southeast africa is more strongly controlled by changes in indian ocean sea surface temperatures and the winter indian monsoon than by migration of the intertropical convergence zone

seismic analysis for the lanzhou fireball in this paper we convert the lanzhou fireball s trajectory using seismic data according to the analytical method presented in pujol et al 2005 2006 taking the same assumptions as pujol et al the position of the fireball burst at its terminal has been converted using a relative simple independent method both the trajectory and the position of burst are roughly coincident

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

the pan amazonian ucayali peneplain late neogene sedimentation in amazonia and the birth of the modern amazon river system abstract we review the neogene geologic history of lowland amazonia in an attempt to focus attention on areas of agreement as well as areas in dispute in this research arena we reinterpret pre existing hypotheses present new data and discuss new insights intended to support a unified synthesis of the amazon basin as a single sedimentary basin albeit on a vast scale during the late miocene to middle late pliocene we document the ucayali peneplain as an isochronous pan amazonian geologic feature that formed following the early to mid miocene quechua i orogenic phase of andean tectonism peneplanation began possibly as early as 15 ma and terminated abruptly near the beginning of the late miocene quechua ii orogenic event at 9 5 9 0 ma subsequently a thin cover of sediments comprising the madre de dios formation began blanketing most of lowland amazonia excepting only the eastern subandean fold and thrust belt and isolated highlands within the basin the buried peneplain is readily observed in river cutbanks throughout amazonia as the marked often angular ucayali unconformity that separates eroded older often folded faulted and weathered moderately to well consolidated tertiary formations from unconsolidated near horizontal upper neogene deposits the dates of formation of major unconformities and subsequent depositional events at widely separated areas within the andes of bolivia ecuador and peru are coincident with that of the ucayali unconformity and deposition of the madre de dios formation and suggest that the events are linked to a common cause which is interpreted to be the still on going collision between the south american and nazca tectonic plates the madre de dios formation has three members the oldest of which documents a short lived high energy depositional environment followed by a moderate energy depositional environment both occurring at a time when drainage from the basin was unobstructed the upper two members record fluctuations between moderate and low energy continental depositional environments during a period when drainage from the basin was obstructed disorganized and took place over long distances with extremely low gradients the sedimentology of the madre de dios formation particularly the thick massive beds of clay and the widespread presence of paleodeltas and associated geomorphic features on the amazonian planato are consistent with the hypothesis that much of the upper two members formed as lacustrine and deltaic deposits within a gigantic lake lago amazonas or more probably within a complex series of interconnected mega lakes that occasionally united to cover most or all of lowland amazonia to a shallow depth from the latest miocene until 2 5 ma the presence of the ucayali unconformity and the relatively uniform lithostratigraphy basin wide of the fluvial fluviolacustrine and lacustrine sediments of the upper neogene madre de dios formation are consistent with the hypothesis that the amazon basin acted as a single undivided sedimentary basin in the late neogene the biostratigraphic correlation across important modern drainage divides of both micro and macro sized late miocene fossil vertebrates recovered from basal conglomerates of the madre de dios formation and the absence therefrom of fossil vertebrates of any other age is also consistent with this hypothesis two 40ar 39ar dates on ash deposits within the madre de dios formation corroborate the upper miocene age of the basal horizons of that formation indicated by fossil vertebrates and support an upper pliocene age for the youngest sediments of the formation the modern amazon river drainage system was established in the late pliocene at 2 5 ma by the breaching of the eastern rim of the sedimentary basin as a result of the basin being overfilled or by headward erosion of the lower amazon river or both data on cenozoic mass accumulation rates and the chemistry of terrigenous sediments in the atlantic ocean obtained by ocean drilling project leg 154 ceara rise support the postulated timing of the establishment of the modern amazon river drainage system at 2 5 ma rather than the long held view that this event occurred in the late miocene we discuss the important role of ocean currents and sea level fluctuations on terrigenous mass accumulation rates on the ceara rise the postulated time of formation of the modern amazon river is nearly coincident with the onset of the plio pleistocene glacial climatic regime and the lowest sea level stands since the latest middle miocene this analysis indicates that modern amazonia is a product of terrain development within an erosional regime since 2 5 ma

multi element chemistry of some amazonian waters and soils abstract the rivers flowing through the amazon basin are both physically and chemically heterogeneous through detailed geochemical analyses variability is shown to be primarily controlled by both substrate lithology in the source region and soil geochemistry in the erosional regime the solute rich waters of the rio solimoes reflect the drainage from the andes mountains and the fertility of the varzea in contrast the solute deficient waters of the rio negro reflect the infertility of the lateritic and podsolitic terrains of the central amazon rivers flowing through the precambrian shield have an intermediate composition such observations suggest that it is possible to classify the chemical composition of amazonian rivers according to the soil types in their catchment regions and vice versa these findings have profound implications for using water chemistry as an indicator of the agricultural and mineral potential of a region results from this study also confirm that precipitation is a significant source of major cations and trace metals to solute deficient river systems such as the rio negro

listening to sounds from an exploding meteor and oceanic waves low frequency sound infrasound measurements have been selected within the comprehensive nuclear test ban treaty ctbt as a technique to detect and identify possible nuclear explosions the seismology division of the royal netherlands meteorological institute knmi operates since 1999 an experimental infrasound array of 16 micro barometers here we show the rare detection and identification of an exploding meteor above northern germany on november 8th 1999 with data from the deelen infrasound array dia at the same time sound was radiated from the atlantic ocean south of iceland due to the atmospheric coupling of standing ocean waves called microbaroms occurring with only 0 04 hz difference in dominant frequency dia proved to be able to discriminate between the physically different sources of infrasound through its unique lay out and instruments the explosive power of the meteor being 1 5 kt tnt is in the range of nuclear explosions and therefore relevant to the ctbt

a 100 year average recurrence interval for the san andreas fault at wrightwood california evidence for five large earthquakes during the past five centuries along the san andreas fault zone 70 kilometers northeast of los angeles california indicates that the average recurrence interval and the temporal variability are significantly smaller than previously thought rapid sedimentation during the past 5000 years in a 150 meter wide structural depression has produced a greater than 21 meter thick sequence of debris flow and stream deposits interbedded with more than 50 datable peat layers fault scarps colluvial wedges fissure infills upward termination of ruptures and tilted and folded deposits above listric faults provide evidence for large earthquakes that occurred in a d 1857 1812 and about 1700 1610 and 1470

thermal response of the western tropical atlantic to slowdown of the atlantic meridional overturning circulation abstract the western tropical atlantic plays an important role in the interhemispheric redistribution of heat during millennial scale changes in the strength of the atlantic meridional overturning circulation amoc the proper evaluation of this role depends on a clear understanding of sea surface temperature sst variations during amoc slowdown periods like heinrich stadials hs in the western tropical atlantic however published sst records from the western tropical atlantic between ca 4 s and 7 n show inconsistencies that are apparently related to the employed temperature proxy i e mg ca versus alkenone unsaturation index u 37 k in general while mg ca values indicate warming during heinrich stadials u 37 k values show cooling to assess this issue we sampled core geob16224 1 retrieved off french guiana i e 6 39 38 n and reconstructed water temperatures at high resolution using mg ca on the foraminifera species globigerinoides ruber u 37 k tex86 and modern analogue technique mat transfer functions using planktonic foraminifera assemblages calibrated for 50 m water depth our results show that mg ca and tex86 values recorded an increase in sst related to amoc slowdown conversely u 37 k and mat values registered a decrease in temperatures during hs3 and hs1 our u 37 k and mg ca results thus confirm the previously reported inconsistency for the period between 48 13 cal ka bp we suggest that several non thermal physiological effects probably imparted a negative temperature bias on the u 37 k temperatures during heinrich stadials however mat based temperatures show similar variability with u 37 k based temperatures hence we also suggest that during severe slowdown periods of the amoc a steeper meridional temperature gradient together with a southward shift of the intertropical convergent zone produced not only an increase in sst but also a stronger upper water column stratification and a shoaling of the thermocline decreasing subsurface temperatures our new high resolution temperature records allow a better characterization of the thermal response of the upper water column in the tropical western atlantic to slowdown events of the amoc reconciling previously discrepant records

slip along the san andreas fault associated with the great 1857 earthquake historical records indicate that several meters of lateral slip along the san andreas fault accompanied the great 1857 earthquake in central and southern california these records together with dendrochronological evidence suggest that the rupture occurred along 360 to 400 km of the fault including several tens of kilometers of the currently creeping reach in central california geomorphic expressions of late holocene right lateral offsets are abundant along the 1857 rupture along 300 kilometers of the 1857 rupture between cholame and wrightwood the youngest discernible offset ranges from 3 to 9 1 2 meters dormancy of the fault since 1857 almost certainly indicates that this latest offset was created in 1857 fault slip apparently associated with the 1857 earthquake varies in a broadly systematic way along the trace of the fault it is relatively uniform along each of several long segments but changes rather abruptly in value between these segments this nonuniform displacement pattern may imply that some segments of the fault rupture more frequently or experience a slower long term slip rate than others the 1857 offsets indicate a seismic moment m o between 5 3 and 8 7 10 27 dyne cm assuming a 10 to 15 km depth of rupture and relatively uniform slip as a function of depth a comparison with the rupture length average slip value and tectonic setting of the california earthquake of 1906 m s 8 1 4 indicates a value of m 8 1 4 for the 1857 event

terrestrial vegetation change inferred from n alkane σ13c analysis in the marine environment abstract we report gas chromatography isotope ratio monitoring mass spectrometry gc irm ms measurements of the 13c values of individual biomarker compounds n alkanes extracted from a 3 m marine sediment core taken near the mouth of the johnstone river north queensland australia the technique allows a purely terrestrial isotope signal to be discerned despite mixing of terrestrial and marine derived carbon the results indicate that there has been a 2 increase in the 13c values of terrestrially derived n alkanes c29 c33 since clearing of the forested johnstone river drainage basin for sugarcane and pasture began in the late 19th century a much slower 1 increase in 13c values after 6 000 years bp and prior to european settlement may be related to a decrease in rainfall in the basin or to an increase in the abundance of c4 plants as a result of increased aboriginal burning the results from the sediment core are consistent with data obtained for modern river sediments from forested and cleared subcatchments within the basin and demonstrate that the 13c values of terrestrially derived n alkanes in the marine environment can be used to assess basin wide vegetation changes in adjacent river catchments on geological timescales

thunder induced ground motions 1 observations 1 acoustic pressure from thunder and its induced ground motions were investigated using a small array consisting of five three component short period surface seismometers a three component borehole seismometer and five infrasound microphones we used the array to constrain wave parameters of the incident acoustic and seismic waves the incident slowness differences between acoustic pressure and ground motions suggest that ground reverberations were first initiated somewhat away from the array using slowness inferred from ground motions is preferable to obtain the seismic source parameters we propose a source equalization procedure for acoustic seismic deconvolution to generate the time domain transfer function a procedure similar to that of obtaining teleseismic earthquake receiver functions the time domain transfer function removes the incident pressure time history from the seismogram an additional vertical to radial ground motion transfer function was used to identify the rayleigh wave propagation mode of induced seismic waves complementing that found using the particle motions and amplitude variations in the borehole the initial motions obtained by the time domain transfer functions suggest a low poisson s ratio for the near surface layer the acoustic to seismic transfer functions show a consistent reverberation series at frequencies near 5 hz this gives an empirical measure of site resonance that depends on the ratio of the layer velocity to layer thickness for earthquake p and s waves the time domain transfer function approach by transferring a spectral division into the time domain provides an alternative method for studying acoustic to seismic coupling

modern pollen signatures of amazonian rivers and new insights for environmental reconstructions abstract paleoenvironmental reconstructions based on amazonian fluvial and marine pollen data are often hindered due to the scarcity of modern calibration data in amazonia rivers are the main pathways for pollen from upland and flooded forests to continental and marine sediment sinks linking pollen assemblages transported by rivers to watershed vegetation is crucial to interpret palynological archives in order to constrain the interpretation of palynological archives we analysed the pollen content of 36 riverbed sediment samples distributed from the mouth of the ica river ca 68ow to the amazon estuary ca 49ow with support of grain size and major element analyses of the inorganic sedimentary content the palynological analysis shows a strong imprint of the lowland floodplain vegetation as the main source of the riverborne pollen the upper reaches of the amazon river present abundant cecropia reflecting early successional stages induced by intense floodplain disturbance the middle and lower reaches of the amazon river exhibit a progressive increase in herbs mainly represented by poaceae and cyperaceae related to wider floodplains covered by seasonally inundated vegetation floodplain forests of whitewater rivers varzeas are palynologically characterized by iriartea mauritia ilex pseudobombax acalypha and luehea laetia with high frequency of cecropia or herbs and montane taxa at the black and clearwater rivers the igapo floodplain forests provide high percentages of symmeria myrtaceae and alchornea and can be distinguished by sapium sebastiana piranhea amanoa pouteria ferdinandusa genipa attalea astrocaryum and eschweilera which suggest conditions of higher stability and mature forests contribution from the non flooded uplands andean mountains and savannas cerrado occur but their signals are blurred by the high pollen production of the lowland floodplains our data provide a calibration set for environmental reconstructions of river influenced deposits across the amazon including offshore areas of the most iconic riverine dominated landscape in the world

tectonic geomorphology of the san andreas fault zone in the southern indio hills coachella valley california geomorphic investigation of the san andreas fault zone in the indio hills indicates many tectonically produced landforms including beheaded streams right lateral deflected and offset streams sags shutter ridges pressure ridges and fault scarps near biskra palms an alluvial fan pediment complex has an apparent cumulative offset of about 0 7 km along the mission creek fault zone north branch san andreas fault many of the tectonic landforms as well as the fracture pattern that has developed during the pleistocene are explainable by simple shear or uplift associated with a small left bend in the main trace of the mission creek fault the ratio of vertical to horizontal displacement in the vicinity of the bend is about 0 04 exposed in pushawalla canyon 5 km northwest of the alluvial fan pediment complex are 1 a sequence of stream terraces 2 folded plio pleistocene fanglomerates and 3 an example of stream capture following a right lateral deflection or offset of several hundred metres a left step of the mission creek fault in pushawalla canyon is a probably cause of folds and sporadic uplift that produced the stream terraces possible cause of recent stream capture are 1 juxtaposition of pushawalla canyon with a relict canyon moving northwestward along the mission creek fault or 2 right lateral deflection or offset of pushawalla canyon along the fault with simultaneous headward erosion of a shorter steep stream flowing toward the coachella valley estimation of a slip rate and identification of paleoseismicity for the san andreas fault in the indio hills is difficult however degree of topographic dissection formation and preservation of desert pavement and relative soil profile development suggest that the age of the offset fan may be as old as 70 000 yr but that most likely it is on the order of 20 000 to 30 000 yr these age estimates for the offset fan indicate a minimum slip rate for the san andreas fault of 10 to 35 mm yr with about 23 to 35 mm yr the most likely the pattern of observed offset drainages is complex but suggests that during the past few thousand years creep events or moderately large earthquakes have periodically produced several metres of right lateral displacement

new views on old carbon in the amazon river insight from the source of organic carbon eroded from the peruvian andes 1 mountain rivers play a key role in the delivery of particulate organic carbon poc to large river systems and the ocean due to the extent of its drainage area and runoff the amazon river is one of earth s most important biogeochemical systems however the source of poc eroded from the humid region of the eastern andes and the input of fossil poc from sedimentary rocks pocfossil remains poorly constrained here we collected suspended sediments from the kosnipata river during flood events to better characterize andean poc measuring the nitrogen to organic carbon ratio n c stable carbon isotopes 13corg and radiocarbon 14corg 14corg values ranged from 711 to 15 and significant linear trends between 14corg n c and 13corg suggested that this reflects the mixing of pocfossil with very young organic matter 14corg 50 from the terrestrial biosphere pocnon fossil using n c and 14corg in an end member mixing analysis we quantify the fraction of pocfossil to within 0 1 and find that it contributes a constant proportion of the suspended sediment mass 0 37 0 03 and up to 80 of total poc in contrast the relative contribution of pocnon fossil was variable being most important during the rising limb and peak discharges of flood events the new data shed light on published measurements of old poc low 14corg in andean fed tributaries of the amazon river with their 14corg and 13corg values consistent with variable addition of pocfossil the findings suggest a greater persistence of andean poc in the lowland amazon than previously recognized

seismicity and fault kinematics through the eastern transverse ranges california block rotation strike slip faulting and low angle thrusts hypocentral locations and first motion data from the southern california seismic network are used to infer the present pattern of deformation along the southern san andreas fault the study area lies between the san jacinto fault and desert hot springs and includes the san bernardino mountains and san gorgonio pass this region has some of the deepest earthquakes observed anywhere along the entire san andreas system exhibits a complex surface geology characterized by both right and left lateral faults has high topographic relief as a result of recent uplift and is a potential site for the nucleation of a great earthquake although this area is unusually seismogenic little activity can be directly associated with major throughgoing faults seismicity is also generally absent in the upper 5 km the predominant style of faulting above 10 12 km is oblique slip with a large reverse component the spatial distribution of relocated hypocenters and first motion data suggests the presence of a system of left slip faults striking northeast this pattern of faulting in conjunction with an unusual set of normal and reverse focal mechanisms is interpreted as the clockwise rotation of a small set of crustal blocks subject to regional right lateral shear at depths greater than about 10 km seismicity defines a wedge shaped volume undergoing pervasive internal deformation on a combination of strike slip and low angle thrust faults velocity structures determined from earthquake arrival times suggest a low velocity zone at about 10 km below the san bernardino mountains but not below the san jacinto mountains this is nearly the same depth as the transition between the two layers of different kinematic behavior seen south of the mill creek mission creek branch of the san andreas fault and the maximum depth of seismicity seen north of that fault the low velocity zone and the transition between block rotations and the deeper deformation may thus correspond to a detachment under much of this region and would imply that the overthrust san bernardino mountains are allochthonous the present pattern of seismic deformation in shocks of small to moderate size may only characterize the interval between large earthquakes and may change systematically as the region prepares to accommodate large right lateral displacements

relationships between mineral surfaces and organic carbon concentrations in soils and sediments abstract relationships between mineral specific surface area and organic carbon oc concentration are examined for sediments and soil a horizons from throughout the world i found published elsewhere that continental shelf sediments from many different regions exhibit downcore loss of oc to a refractory background level which shows a consistent relationship with mineral surface area slope 0 86 mg m 2 oc this trend is equivalent to a monolayer of organic matter over all surfaces and is termed the monolayer equivalent me level sediments and soils from other environments are compared to this empirically derived relationship several continental slope areas show extension of this relationship to considerable depth marked excesses of oc above this trend which persist downcore were found in sediments with high carbonate mineral content or slope sediments with low dissolved oxygen concentrations in the overlying water column about half of the soils examined also adhered to this relationship while soils with high carbonate content low ph or poor drainage showed oc concentrations higher than the me level oc concentrations below the me level are found in deltaic regions and areas with low organic matter delivery such as the deep sea or arid soils the nature of mineral surfaces was examined using n2 adsorption desorption isotherms and most surface area was found to be present as pores with

meteoroid sonic shock wave generated seismic signals observed at a seismic array at approximately 04 20 local time 10 20 ut on 19 september 1986 a local resident observed a meteor in the sky above yellow knife north west territory canada we subsequently found seismic signals recorded at the yellowknife seismic array in northwest territory canada that coincided with the visual observation of the meteor in the sky overhead the signals cannot be explained by any earthquake explosion or impact generating mechanism they are shown to be consistent with their having been generated by the shock wave created by the associated meteoroid as it passed through the atmosphere overhead the meteoroid s trajectory and velocity as inferred from the array records is consistent both with the observed direction of travel of the meteoroid and independent seismic observations recorded at two single stations in the northern canadian seismic network