assessment of teleseismically determined source parameters for the april 25 2015 mw 7 9 gorkha nepal earthquake and the may 12 2015 mw 7 2 aftershock on april 25 2015 a major m w 7 9 thrust earthquake ruptured the deeper portion of the seismogenic plate boundary beneath nepal along which india is underthrusting eurasia an m w 7 2 aftershock on may 12 2015 extended the eastern down dip edge of the rupture these destructive events caused about 9000 fatalities and 23 000 injuries the overall rupture zone is about 170 km long and 40 80 km wide this region of the plate boundary previously experienced a large earthquake in 1833 and in 1934 a larger m s 8 0 event located to the east ruptured all the way to the surface the main himalayan thrust mht on which slip occurred in 2015 has a very low dip angle of 6 and the depth of the mainshock slip distribution is very shallow extending from 7 to 18 km the shallow dip and depth present challenges for resolving faulting characteristics using teleseismic data we analyze global teleseismic signals for the mainshock and aftershock to estimate source parameters evaluating the stability of various procedures used for remotely characterizing kinematics of such shallow faulting back projection and finite fault slip inversion are used to assess the spatio temporal rupture history and evidence for frequency dependent radiation along dip slip zone width constraints from near field geodetic observations are imposed on the preferred models to overcome some limitations of purely teleseismic methods radiated energy stress drop and moment rate functions are determined for both events

imaging the moho and the main himalayan thrust in western nepal with receiver functions the crustal structure of western nepal is studied for the first time by performing receiver function analysis on teleseismic waveforms recorded at 16 seismic stations the moho geometry is imaged as it deepens from 40 km depth beneath the foothills and the lesser himalaya to 58 km depth beneath the higher himalayan range a midcrustal low velocity zone is detected at 15 km depth along 55 km horizontal distance and is interpreted as the signature of fluids expelled from rocks descending in the footwall of the main himalayan thrust our new image allows structural comparison of the moho and of the main himalayan thrust geometry along strike of the himalayas and documents long wavelength lateral variations the general crustal architecture observed on our images resembles that of central nepal therefore western nepal is also expected to be able to host large m w 8 megathrust earthquakes as the 1505 ce event plain language summary we investigate the earth s crust in western nepal we use 16 stations to detect waves from faraway earthquakes and using these we make an image of the structure of the crust we find that the crust is getting thicker beneath the himalaya and that fluids are locally present in the upper part of the crust as this image is similar to the one we know in central nepal where major earthquakes happened it is possible that major earthquakes will also happen in western nepal in the future without knowing when

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

sbas interferometric analysis for volcanic eruption of hawaii island abstract the kilauea volcano on the hawaii island started erupting on 3rd may 2018 after an earthquake of magnitude 5 0 the initial volcano eruption and the subsequent earthquakes resulted in the opening of new volcanic fissures continuous lava flow at the lower east rift zone and the collapse of the summit caldera floor all these activities continued until the 1st week of august 2018 the small baseline subset sbas technique is an advanced form of differential interferometry dinsar which is capable of monitoring surface deformations with millimetre level accuracy sbas technique was utilised here for estimating the surface deformation on hawaii island due to the volcanic episode insar coherence technique was also utilised in this study for localised analysis at the summit and at the lower east rift zone to detect the time series deformation information and lava flow patterns 14 interferometric datasets acquired by the esa s sentinel 1 c band satellite from april 2018 to september 2018 were used in this study the data acquired by the seismometers installed at kilauea by hawaii volcano observatory the swir band of sentinel 2 and the thermal band of landsat 8 were used to correlate and verify the results obtained through the sbas and insar coherence analysis the combined interpretation of results obtained from all the sources gave insights about the underground magma conduit system surface deformations lava flow channels and the correlation between the magmatic and seismic activity happened there which are discussed in detail in this paper

the mechanism of partial rupture of a locked megathrust the role of fault morphology assessment of seismic hazard relies on estimates of how large an area of a tectonic fault could potentially rupture in a single earthquake vital information for these forecasts includes which areas of a fault are locked and how the fault is segmented much research has focused on exploring downdip limits to fault rupture from chemical and thermal boundaries and along strike barriers from subducted structural features yet we regularly see only partial rupture of fully locked fault patches that could have ruptured as a whole in a larger earthquake here we draw insight into this conundrum from the 25 april 2015 m w 7 8 gorkha nepal earthquake we invert geodetic data with a structural model of the main himalayan thrust in the region of kathmandu nepal showing that this event was generated by rupture of a decollement bounded on all sides by more steeply dipping ramps the morphological bounds explain why the event ruptured only a small piece of a large fully locked seismic gap we then use dynamic earthquake cycle modeling on the same fault geometry to reveal that such events are predicted by the physics depending on the earthquake history and the details of rupture dynamics however great earthquakes that rupture the entire seismogenic zone are also possible these insights from nepal should be applicable to understanding bounds on earthquake size on megathrusts worldwide

ductile shearing to brittle thrusting along the nepal himalaya linking miocene channel flow and critical wedge tectonics to 25th april 2015 gorkha earthquake the 25th april 2015 magnitude 7 8 gorkha earthquake in nepal ruptured the main himalayan thrust mht for 140 km east west and 50 km across strike the earthquake nucleated at a depth of 15 18 km approximating to the brittle ductile transition and propagated east along the mht but did not rupture to the surface leaving half of the fault extent still locked beneath the siwalik hills coseismic slip shows that motion is confined to the ramp flat geometry of the mht and there was no out of sequence movement along the main central thrust mct below 20 km depth the mht is a creeping aseismic ductile shear zone cumulated deformation over geological time has exhumed the deeper part of the himalayan orogen which is now exposed in the greater himalaya revealing a tectonic history quite different from presently active tectonics there early miocene structures including the mct are almost entirely ductile with deformation occurring at temperatures higher than 400 c and were active between 22 16 ma kyanite and sillimanite grade gneisses and migmatites approximately 5 20 km thick in the core of the greater himalayan sequence ghs together with leucogranite intrusions along the top of the ghs were extruded southward between 22 15 ma concomitant with ages of partial melting thermobarometric constraints show that ductile extrusion of the ghs during the miocene occurred at muscovite dehydration temperatures 650 775 c and thus brittle thrusting and critical taper models for ghs deformation are unrealistic as partial melting and channel flow ceased at 15 ma brittle thrusting and underplating associated with duplex formation occurred along the lesser himalaya passively uplifting the ghs

neoproterozoic glacial deposits from the aracuai orogen brazil age provenance and correlations with the sao francisco craton and west congo belt article i nfo glacigenic diamictite successions of the macaubas group are widespread in the western domain of the aracuai orogen east of the sao francisco craton brazil diamictites also occur on this craton and in the african counterpart of the aracuai orogen the west congo belt detrital zircon grains from the matrix of diamictites and sandstones from the macaubas group were dated by the u pb shrimp technique the geochronological study sets the maximum depositional age of the glacial diamictites at 900 ma and indicates multiple sources for the macaubas basin with ages ranging from 900 to 2800 ma sm nd tdm model ages determined on whole rock samples range from 1 8 ga to 2 5 ga and get older up section comparison of our data with those from the cratonic area suggest that these glacial deposits can be correlated to the jequitai and carrancas diamictites in the sao francisco craton and to the lower mixtite formation of the west congolian group exposed in africa the 900 1000 ma source is most probably represented by the zadinian mayumbian volcanic rocks and related granites from the west congo belt however one of the most voluminous sources with ages in the 1 1 1 3 ga interval has not been detected in the sao francisco congo craton possible sources for these grains could occur elsewhere in africa or possibly from within the brasilia belt in western central brazil

glacial sedimentation in the late precambrian bebedouro formation bahia brazil abstract the possibility that diamictites of the late precambrian bebedouro formation of northern bahia brazil are glacial in origin has been based on the areal extent diversity of the lithology of the stones and the presence of outsize dropstones in rhythmites more detailed studies on the diamictites show that some of the stones are faceted and their shapes are typical of those developed by glacial transport additionally a small abraded pavement is described and garnets found in the matrix of the diamictite have chattermark trails taken in aggregrate these observations suggest a glacial origin for the bebedouro formation in the study area the texture of the diamictites range from stone rich to siltstones containing sporadic stones the stone rich diamictites are commonly found in layers up to a metre in thickness separated by poorly laminated siltstone the formation probably was deposited in a large lake or sea and the layered diamictites are debris flows which were derived from uneven piles of glacial debris deposited on the floor of the lake or sea

sedimentation in glacial environments and the identification of tills and tillites in ancient sedimentary sequences abstract tills and tillites are defined and subdivided into primary tills comprising lodgement tills melt out tills and sublimation tills and secondary tills comprising flow tills and deformation tills they are defined on the basis of their mode of deposition which endows them with their distinctive properties another category of till that of supra till is defined on the basis of its debris source derived supraglacially from valley sides and nunataks which gives these tills a coarse grained character the processes of till deposition and of outwash sedimentation are associated in several recurrent combinations which allow the definition of three principal glacial sediment associations and land systems which define the character of the sequences within which tills tend to occur the criteria which allow tills of different genesis to be identified and to be distinguished from non till diamictons are reviewed there are several features which are uniquely characteristic of till but unfortunately these are few it has been found generally necessary to employ an array of characteristics which though not individually unique to till when taken together can be strong evidence for particular till types the recognition of several typical and repetitive facies sequences which form in the major glacial sedimentary environments can also be important indicators of till genesis

line of sight displacement from alos 2 interferometry mw 7 8 gorkha earthquake and mw 7 3 aftershock interferometric synthetic aperture radar insar is a key tool for the analysis of displacement and stress changes caused by large crustal earthquakes particularly in remote areas a challenge for traditional insar has been its limited spatial and temporal coverage especially for very large events whose dimensions exceed the typical swath width of 70 100 km this problem is addressed by the alos 2 satellite whose palsar 2 instrument operates in scansar mode enabling a repeat time of 2 weeks and a swath width of 350 km here we present insar line of sight displacement data from alos 2 palsar 2 observations covering the mw 7 8 gorkha nepal earthquake and its mw 7 3 aftershock that were acquired within 1 week of each event the data are made freely available and we encourage their use in models of the fault slip and associated stress changes the mw 7 3 aftershock not only extended the rupture area of the main shock toward the east but also left a 20 km gap where the fault has little or no coseismic slip we estimate this unslipped fault patch has the potential to generate a mw 6 9 event

chattermarked garnets in pleistocene glacial sediments an examination of the surface textures on detrital garnets shows that conchoidal fractures v shaped etch pits and other marks of unknown origin can be modified by chemical etching to produce features which resemble chattermark trails produced by slip stick motion in order to differentiate false trails from those produced by glacial grinding it is recommended that the altered surfaces of garnets be examined under a scanning electron microscope an analysis of chattermark trails on garnets from glaciogenic deposits from nova scotia denmark and south central ontario shows that there is a wide variation in the percentage of garnets with chattermark trails in different glacial environments however after local anomalies in the percentage of chattermarked garnets are averaged out by recycling and dispersion there is evident a crude correlation between the type of glaciation and the average percentage of chattermarked garnets in glacial deposits

kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data rapid near source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation adversely affecting subsequent tsunami prediction seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high rate gps and strong motion data overcome these limitations supplementing land based data with offshore wave measurements by seafloor pressure sensors and gps equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent inundation and runup we present a kinematic source model obtained from a retrospective real time analysis of a heterogeneous data set for the 2011 mw9 0 tohoku oki japan earthquake our model is consistent with conceptual models of subduction zones exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions the stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off shore data are included the kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis notably we include the horizontal advection of steeply sloping bathymetric features comparison with post event on land survey measurements demonstrates that the tsunami s inundation and runup are predicted with considerable accuracy only limited in scale by the resolution of available topography and bathymetry we conclude that it is possible to produce credible and rapid kinematic source models and tsunami predictions within minutes of earthquake onset time for near source coastal regions most susceptible to loss of life and damage to critical infrastructure regardless of earthquake magnitude

scansar to stripmap mode interferometry processing using envisat asar data interferometric synthetic aperture radar insar images of geophysical events such as preeruptive volcano deformation or interseismic strain accumulation are often limited by phase distortions from the superimposed atmospheric signature additionally the approximate monthly repeat cycle of many radar satellites cannot accurately capture rapidly time varying processes the scanning synthetic aperture radar scansar mode of the envisat asar instrument permits more frequent revisits of a given area potentially overcoming both of these limitations in particular stripmap mode to scansar images provide a denser time series of interferograms than is possible with conventional stripmap to stripmap mode insar we present images of envisat asar data acquired over hawaii in which data acquired roughly weekly in scansar mode are combined with envisat asar conventional stripmap mode data to form interferograms at a much denser temporal spacing the burst nature of scansar data requires a new processing method to form the interferograms we use traditional matched filtering for the range compression for the azimuth processing we compute the stripmap mode data on the scansar sampling grid using a variation consisting of different reference functions of lanari s modified specan algorithm that is itself an adaptation of the chirp z transform to readjust the azimuth pulse spacing the resulting interferograms faithfully reflect the phase of conventional interferograms but exhibit fewer looks and coarser resolution than those produced by fully stripmap mode data for many problems temporal density of the deformation observations is paramount and the time series analysis and temporal averaging that were made possible using scansar interferograms far outweigh the loss in looks and resolution

experimental formation and significance of etch patterns on detrital garnets the patterns found on the surfaces of etched detrilal garnets are formed by facets that resemble a series of elongated overlapping sharp edged rectangular or rhombohedral building blocks mammilla

ice thrust features and a possible intertillite pavement in the proterozoic macaubas group jequitai area minas gerais brazil in north central minas gerais large bodies of quartzite up to 25 m long are found in tillite of the proterozoic macaubas group although one body is intact others are disrupted and intermixed with sheared siltstone and tillite two tillites separated by a thin conglomerate are found in the same area striations found on the top of the lower tillite display two directions of ice movement east west and northeast southeast the orientation of the quartzite bodies shear planes in the tillite and the striations on the lower tillite combine to suggest that the ice was moving in an east to northeast direction

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

slip model of the 2015 mw 7 8 gorkha nepal earthquake from inversions of alos 2 and gps data we use surface deformation measurements including interferometric synthetic aperture radar data acquired by the alos 2 mission of the japanese aerospace exploration agency and global positioning system gps data to invert for the fault geometry and coseismic slip distribution of the 2015 mw 7 8 gorkha earthquake in nepal assuming that the ruptured fault connects to the surface trace of the main frontal thrust mft fault between 84 34 e and 86 19 e the best fitting model suggests a dip angle of 7 the moment calculated from the slip model is 6 08 1020 nm corresponding to the moment magnitude of 7 79 the rupture of the 2015 gorkha earthquake was dominated by thrust motion that was primarily concentrated in a 150 km long zone 50 to 100 km northward from the surface trace of the main frontal thrust mft with maximum slip of 5 8 m at a depth of 8 km data thus indicate that the 2015 gorkha earthquake ruptured a deep part of the seismogenic zone in contrast to the 1934 bihar nepal earthquake which had ruptured a shallow part of the adjacent fault segment to the east

measuring azimuth deformation with l band alos 2 scansar interferometry we analyze the methods for measuring azimuth deformation with the l band advanced land observing satellite 2 alos 2 scanning synthetic aperture radar scansar interferometry to implement the methods we extract focused bursts from the alos 2 full aperture product which is the only product available for scansar interferometry at present the extracted bursts are properly processed to measure azimuth deformation using interferometric phase we apply the range split spectrum method to scansar to estimate the differential ionospheric phase of the interferogram and take the azimuth derivative of the differential ionospheric phase to mitigate the relative azimuth shift caused by ionosphere for the first time azimuth deformation of a large earthquake april 25 2015 nepal earthquake is nearly completely measured by the l band scansar interferometry with moderate precision the result is validated by the azimuth deformation measured by incoherent cross correlation using a pair of high resolution radarsat 2 images in addition to the final azimuth deformation we show the possibility of processing full aperture scansar product using a burst by burst approach to form regular interferograms we also show the recent strong large scale ionospheric effects on the l band alos 2 scansar interferograms other possible applications of this paper include measuring the movement of glaciers

more major earthquakes at the nepal himalaya study on coulomb stress perspective abstract on april 2015 a major earthquake of 7 9 mw occurred in the nepal himalaya followed by 553 earthquakes of local magnitude greater than 4 0 within the first 43 days including another major event of 7 3 mw we resolve the static coulomb failure stress cfs change onto the finite fault models of 7 9 mw after elliott et al 2016 and galezka et al 2015 and its effect on associated receiver faults correlation of aftershocks with the enhanced cfs condition shows that the elliott et al 2016 model explains 60 4 and the galezka et al 2015 model explains about 47 7 of the aftershocks in high stress regions aftershocks were poorly spatially correlated with the enhanced cfs condition after the 7 9 mw main shock and can be explained by correlation with release of seismic energy from the associated secondarily stressed prominent thrust planes and transverse faults stress resolved on the associated receiver faults show increased stress on both transverse and thrust fault systems with the potential of triggering significant aftershocks or subsequent main shocks

proterozoic first order sedimentary sequences of the sao francisco craton eastern brazil abstract the sao francisco craton in eastern brazil hosts sedimentary sequences deposited between the paleoarchean 3300 ma and late neoproterozoic 580 ma proterozoic successions occurring in this region comprise five 1st order sedimentary sequences which besides episodes of global significance record major basin forming events the ca 8000 m thick minas itacolomi 1st order sequence exposed in the brazilian mining district of the quadrilatero ferrifero and containing as marker bed the lake superior type caue banded iron formation tracks the operation of a wilson cycle in the paleoproterozoic era the quartz arenite dominated espinhaco i and ii sequences record at least two major rift sag basin forming events which affected the host continent of the sao francisco craton at around 1 75 ga and 1 57 ga the macaubas sequence and its correlatives in the extracratonic domains witness the individualization of a sao francisco congo plate in synchronicity with the break up of rodinia in the cryogenian period the sao francisco congo plate together with various fragments derived from rodinia reassembled to form gondwana in the ediacaran period in the course of the gondwana amalgamation orogenic belts developed along the margins of the craton its interior converted into foreland basins received the shallow water carbonates and pelites of the bambui 1st order sequence and its correlatives

late proterozoic glaciation in central eastern brazil synthesis and model abstract in the surroundings of the middle proterozoic sao francisco craton of central eastern brazil numerous traces of an ancient glaciation can be found almost all criterua necessary to prove an ancient glaciation occur including scratched and facetted pebbles a striated surface quarrying outwash plains eskers varvites dropstones decollement structures etc poorly sorted tillites with varying pebble composition are widely distributed continental tillites and glaciomarine sequences interfinger in the east and southeast of the craton traces of ice movement suggest flow directions of the ice towards the east and the southeast of the craton at the coast the wet base glaciers passed over to floating shelf ice in the northeast glaciers also came from the serrinha craton in northeastern bahia the glaciation covered an area of at least 1300 700 km the sequences containing traces of glaciation discordantly overlie archean to middle proterozoic rocks they in turn are overlain by late proterozoic calcareous and psammopelitic sediments of the bambui group present data indicate that glaciation took place around 1000 ma ago

paleomagnetic evidence for the evolution of meso to neo proterozoic glaciogenic rocks in central eastern brazil abstract paleomagnetic studies on basic dikes in the eastern sao francisco craton which have isotopic ages of 1 0 1 1 ga define an apparent polar wander path for south america over this time interval the data indicate that the sao francisco craton was at paleolatitudes between 40 and 65 at the time of emplacement of these dikes neo proterozoic sedimentary glaciogenic rocks the macaubas group bebedouro formation ibia formation and carandai formation crop out in central eastern brazil an age of about 1 0 ga has been proposed for these glacial deposits paleogeographical reconstructions of south america show a continental movement coherent with paleoenvironmental models proposed for the macaubas group and suggest that the glacial period may have occurred between 1 01 and 1 08 ga

sedimentary structures made by shore ice in muddy tidal flat deposits st lawrence estuary quebec abstract well preserved sedimentary structures formed by shore ice are exposed in emergent muddy tidal flat deposits along the shoreline of the st lawrence estuary the sedimentary features are exposed in high marsh micro cliffs 1 to 2 m high features from two localities where they are the most abundant sainte anne de beaupre north shore and montmagny south shore are reported here two categories are distinguished first bowl shaped circular and elongated structures 30 to 100 cm across which are former scoured depressions subsequently filled by stratified mud fine sand and organic debris and second deformations folds a few decimeters to a few meters in size produced by ice block pressure pebble to boulder size dropstones are associated with these structures most features were observed in mud flat and low marsh units facies vertically exposed at these localities the age of these tidalite deposits ranges from about 200 to 600 years these ice made structures and deformations well preserved in a sequence of recent emerged tidal sediments suggest that similar features may be preserved in older rock formations consequently they can be considered as a promising tool for interpreting the former climatic conditions in which tidalites and other shallow marine and lacustrine formations may have been deposited

sedimentation patterns during the precambrian a unique record abstract although the similarities between depositional processes and products as well as the analogous controls on basin filling and evolution appear to have enjoyed great uniformity throughout the sedimentary rock record a noticeable distinction exists in the rates and intensities of a broad range of geological processes in the precambrian epoch this paper searches for distinctiveness in the precambrian sedimentary record both siliciclastic and carbonate through an extensive though not exhaustive review of the relevant literature augmented by new observations while differences in precambrian deltaic aeolian glacial and possibly also lacustrine deposits and settings appear to have been small their large scale development was controlled largely by a combination of temporal and geodynamic influences essentially of global compass in this regard the onset of the supercontinent cycle and major perturbations in palaeo atmospheric composition appear to have been significant marine environments provide a poor platform for precambrian phanerozoic comparisons of sedimentation patterns as those from the former period are preserved almost exclusively in epeiric settings an environment essentially lacking on modern earth for the shallow marine carbonates biological mediation of chemical sediment deposition changed radically from dominance by microbial biota in the precambrian to a combination of metazons protozoans and algae for the skeletal carbonates of the phanerozoic despite it being widely recognized that precambrian channel systems were braided in all environments deltaic tidal alluvial fluvial as a consequence of the lack of vegetation and poor development of soils the fluvial setting has some enigmatic aspects amongst these is evidence for ponding of muddy detritus in apparently sandstone bed load dominated braided systems with effects on local palaeoslopes which have resulted in unusual palaeohydraulic parameters for precambrian fluvial systems this is perhaps a field of research which holds greater promise when investigating sedimentation patterns prior to the phanerozoic

negatively buoyant flow in diverging channel iii onset of underflow if they are negatively buoyant denser than ambient water inflows to lakes and reservoirs sink plunge below the water surface after entering the location of the plunge line or maximum penetration into the lake or reservoir is related to the ratio of inertial to buoyant forces and lake or reservoir geometry experiments have been conducted in diverging horizontal laboratory channels and the plunging phenomenon has been reproduced for flows separating from the channel wall the relationship xp b0 0 52f04 has been found to describe the maximum horizontal penetration xp the basic form and exponent of this relation was developed from jet flow theory and the coefficient was experimentally determined f0 is the inflow densimetric froude number and b0 is the inflow channel width experimental data for xp b0 are also reported for attached flows in this case the distance to plunging can be expressed as xp b0 0 74f0 0 5 tan 1

neoproterozoic glacial dynamics revealed by provenance of diamictites of the bebedouro formation sao francisco craton central eastern brazil one of the main questions on neoproterozoic geology regards the extent and dynamics of the glacial systems that are recorded in all continents we present evidence for short transport distances and localized sediment sources for the bebedouro formation which records neoproterozoic glaciomarine sedimentation in the central eastern sao francisco craton sfc brazil new data are presented on clast composition based on point counting in thin section and shrimp dating of pebbles and detrital zircon cluster analysis of clast compositional data revealed a pronounced spatial variability of clast composition on diamictite indicating the presence of individual glaciers or ice streams feeding the basin detrital zircon ages reveal distinct populations of archean and palaeoproterozoic age the youngest detrital zircon dated at 874 9 ma constrains the maximum depositional age of these diamictites we interpret the provenance of the glacial diamictites to be restricted to sources inside the sfc suggesting deposition in an environment similar to ice streams from modern high latitude glaciers

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

coseismic slip model of the 2008 wenchuan earthquake derived from joint inversion of interferometric synthetic aperture radar gps and field data 1 we derived a coseismic slip model for the mw 7 9 2008 wenchuan earthquake on the basis of radar line of sight displacements from alos interferograms gps vectors and geological field data available interferometric synthetic aperture radar insar data provided a nearly complete coverage of the surface deformation along both ascending fine beam mode and descending orbits scansar to scansar mode the earthquake was modeled using four subfaults with variable geometry and dip to capture the simultaneous rupture of both the beichuan fault and the pengguan fault our model misfits show that the insar and gps data are highly compatible the combined inversion yields a 93 variance reduction the best fit model has fault planes that rotate from shallow dip in the south 35 to nearly vertical dip toward the north 70 our rupture model is complex with variations in both depth and rake along two major fault strands in the southern segment of the beichuan fault the slip is mostly thrust 13 m and occurred principally in the upper 10 km of the crust the rupture progressively transformed to right lateral strike slip as it propagated northeast with maximum offsets of 7 m our model suggests that most of the moment release was limited to the shallow part of the crust depth less than 10 km we did not find any shallow slip deficit in the slip depth distribution of this mixed mechanism earthquake aftershocks were primarily distributed below the section of the fault that ruptured coseismically