response of tide dominated mangrove shorelines in northern australia to anticipated sea level rise the exact response of mangrove shorelines to anticipated sea level rise will depend upon the balance between sedimentation and sea level change within the top end of the northern territory of australia there are extensive relatively unmodified tide dominated mangrove forests where tidal processes redistribute sediment harbours such as darwin harbour and tidal rivers such as the south alligator river with its associated coastal and estuarine plains represent opposite extremes in terms of holocene sedimentary infill and will respond differently to sea level rise in darwin harbour mangrove assemblages can be recognized in geomorphologically defined habitats similar topography within and between creeks implies morphodynamic equilibrium with tidal processes tidal reworking of sediment may maintain an equilibrial profile under gradually rising sea level with resuspension of lower intertidal and subtidal muds and their redeposition within upper intertidal mangrove habitats in contrast the plains along the coast and tidal rivers draining into van diemen gulf developed during the post glacial marine transgression and since sea level stabilized around 6000 years ago coastal plains have prograded these broad plains are presently not extensively influenced by salt water but are often at elevations close to or even below modern high tide levels they may therefore revert to saline conditions particularly rapidly if the sea rises the pattern of change may not be directly analogous to marine incursion experienced in the early holocene because broad plains have been able to prograde during the last 6000 years of relatively stable sea level

temporal changes of shallow seismic velocity around the karadere duzce branch of the north anatolian fault and strong ground motion we analyze temporal variations of seismic velocity along the karadere duzce branch of the north anatolian fault using seismograms generated by repeating earthquake clusters in the aftershock zones of the 1999 mw7 4 izmit and mw7 1 duzce earthquakes the analysis employs 36 sets of highly repeating earthquakes each containing 4 18 events the events in each cluster are relocated by detailed multi step analysis and are likely to rupture approximately the same fault patch at different times the decay rates of the repeating events in individual clusters are compatible with the omori s law for the decay rate of regional aftershocks a sliding window waveform cross correlation technique is used to measure travel time differences and evolving decorrelation in waveforms generated by each set of the repeating events we find clear step like delays in the direct s and early s coda waves sharp seismic velocity reduction immediately after the duzce main shock followed by gradual logarithmic type recoveries a gradual increase of seismic velocities is also observed before the duzce main shock probably reflecting post seismic recovery from the earlier izmit main shock the temporal behavior is similar at each station for clusters at various source locations indicating that the temporal changes of material properties occur in the top most portion of the crust the effects are most prominent at stations situated in the immediate vicinity of the recently ruptured fault zones and generally decrease with normal distance from the fault a strong correlation between the co seismic delays and intensities of the strong ground motion generated by the duzce main shock implies that the radiated seismic waves produced the velocity reductions in the shallow material

the evolution of tidal creek networks mary river northern australia tidal creek networks have in 50 years extended over 30 km inland across the coastal plains of the mary river in northern australia invading freshwater wetlands and destroying the associated vegetation the networks have grown at an exponential rate through a combination of main channel extension and tributary development with concomitant widening of the creeks a large tidal range very small elevational differences over the plains and the availability of preexisting channel lines notably in the form of palaeochannels have been major factors contributing to the rapid rate of expansion close parallels exist between these networks and terrestrial networks as regards modes of growth and planimetric properties a channel is initiated when the diffuse flow of a seepage zone becomes concentrated through localized scour subsequent development is characterized by the rapid extension of long first order channels with most tributary addition occurring later model tests suggest that branching was more likely on exterior links in the early stages but that exterior and interior link branching became more equally likely through time although the headward limits of the main creeks seem to have been reached tributary infilling will continue to progress upstream only in the most downstream parts is a stable drainage density being approached the networks not only satisfy the laws of drainage network composition and the basic postulates of the random model but also depart from topologic randomness in similar ways to terrestrial networks both topologic and length properties have changed during evolution but largely at the link rather than network scale the close correspondence with terrestrial networks may be due to the low relief and the relatively unconstrained nature of growth in which availability of space was the main determining factor

temporal changes of subsurface velocities during strong shaking as seen from seismic interferometry 1 we apply a deconvolution method to a strong motion data set recorded at the surface and in boreholes in northeast honshu japan we try to characterize the nonlinear effects of the subsurface soil during strong shaking and show the change of the subsurface velocity structure during the shaking the deconvolved waveforms reflect the subsurface velocity structure and their horizontal and vertical components correspond to s and p wave respectively traveling from the borehole to the ground surface the strong motion records with smaller values of peak acceleration do not include significant nonlinear effects so the deconvolved waveforms of the observed accelerations can be well simulated by the program shake91 for high acceleration motions during the shaking of two separate earthquakes large reductions of near surface velocities are seen in results for the 2008 iwate miyagi nairiku earthquake the large high frequency ground motions over 4g at one near source station caused a nonlinear response of the soil and the reduction of the average shear wave velocity reached 24 this corresponds to a stiffness change of over 75 the soil properties and the stiffness coefficient which changed during the shaking did not fully recover after the shaking leaving a static change

geomorphic change of saltmarsh tidal creek networks in the dyfi estuary wales abstract planimetric changes of saltmarsh tidal creek networks in the dyfi estuary wales have been mapped from aerial photographs dating from 1966 to 1989 rates of these changes have been evaluated with reference to creek length and creek density creek densities have been increasing during their development ranging from 8 up to 11 km km 2 these changes are mainly attributable to the instability of the main dyfi tidal channel flood and storm surges saltmarsh vegetation development elevational differences of the estuarine intertidal zone and sea level fluctuations dissipation of tide and wave energies associated with storm surges is chiefly responsible for the morphological development of the dyfi tidal creeks the discontinuous stage prism asymmetry hydrodynamic model is applicable to explaining the dyfi estuarine tidal creek development a form process feedback between the vertical growth of the dyfi saltmarsh surface and the hydrodynamics of its network is also important in governing the dyfi tidal creek network development the rapid development of the dyfi tidal creek networks could result in the loss of the dyfi estuarine wetland

seismic velocity reduction and accelerated recovery due to earthquakes on the longmenshan fault various studies report on temporal changes of seismic velocities in the crust and attempt to relate the observations to changes of stress and material properties around faults although there are growing numbers of observations on coseismic velocity reductions generally there is a lack of detailed observations of the healing phases here we report on a pronounced coseismic reduction of velocities around two locked sections asperities of the longmenshan fault with a large slip during the 2008 mw 7 9 wenchuan earthquake and subsequent healing of the velocities the healing phase accelerated significantly at the southern asperity right after the nearby 2013 mw 6 6 lushan earthquake the results were obtained by joint inversions of travel time data at four different periods across the wenchuan and lushan earthquakes the rapid acceleration of healing in response to the lushan earthquake provides unique evidence for the high sensitivity of seismic velocities to stress changes we suggest that stress redistribution plays an important role in rebuilding fault strength after a fault ruptures the recovery of its strength may be accelerated by earthquakes that redistribute stress according to an analysis of temporal variation in crustal seismic velocity on the longmenshan fault in china

channel networks a geomorphological perspective the study of channel networks has been dominated since 1966 by the random model however recent work has shown 1 that although the topological properties of small networks conform to the random model more closely than those of large ones even small networks exhibit systematic deviations from topological randomness and 2 that the topological and length properties of channel networks are controlled to a large degree by the spatial requirements of subbasins and the need for these subbasins to fit together in space by the size sinuosity and migration rate of valley bends and by the length and steepness of valley sides the factors that control the density properties of channel networks vary with the scale of the investigation and the geomorphic processes governing channel initiation although progress has been made toward a satisfactory stream junction angle model further work is needed the evolution of channel networks has been investigated by a variety of methods including the development of conceptual and simulation models the monitoring of small scale badland and experimental drainage basins and the substitution of space for time the morphology of most channel networks is largely inherited from the past or strongly influenced by inherited forms inasmuch as there is no way of ever knowing the origin or complex history of such networks the use of stochastic models in their study seems unavoidable

surface deformation related to the 2008 wenchuan earthquake and mountain building of the longmen shan eastern tibetan plateau abstract the 12 may 2008 ms 8 0 wenchuan earthquake china was one of largest continental thrusting events worldwide based on interpretations of post earthquake high resolution remote sensing images and field surveys we investigated the geometry geomorphology and kinematics of co seismic surface ruptures as well as seismic and geologic hazards along the longmen shan fold and thrust belt our results indicate that the wenchuan earthquake occurred along the ne sw trending yingxiu beichuan and guanxian anxian faults in the longmen shan fold and thrust belt the main surface rupture zones along the yingxiu beichuan and guanxian anxian fault zones are approximately 235 and 72 km in length respectively these sub parallel ruptures may merge at depth the yingxiu donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step overs or bends in map view surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around beichuan county earthquake related disasters e g landslides are linearly distributed along the surface rupture zones and associated river valleys the wenchuan earthquake provides new insights into the nature of mountain building within the longmen shan eastern tibetan plateau the total crustal shortening accommodated by this great earthquake was as much as 8 5 m with a maximum vertical uplift of approximately 10 m the present results suggest that ongoing mountain building of the longmen shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 wenchuan earthquake furthermore rapid erosion within the longmen shan fold and thrust belt occurs along deep valleys and rupture zones following the occurrence of large scale landslides triggered by earthquakes consequently we suggest that crustal shortening related to repeated great seismic events together with isostatic rebound induced by rapid erosion related unloading is a key component of the geodynamics that drive ongoing mountain building on the eastern tibetan plateau

effect of regional slope on drainage networks drainage networks that develop under conditions of no structural control and homogeneous lithology are generally dendritic depending upon the shape and inclination of the surface on which they form an experimental study was designed to investigate the effect of an increase of slope on the evolution and development of dendritic drainage patterns as slope steepens the pattern changes from dendritic at 1 slope to subdendritic at 2 to subparallel at 3 to parallel at 5 and higher the change from a dendritic type pattern to a parallel type pattern occurs at a low slope between 2 and 3 and primary channel junction angles decrease abruptly from about 60 to 43

time lapse changes of seismic velocity in the shallow ground caused by strong ground motion shock of the 2000 western tottori earthquake japan as revealed from coda deconvolution analysis abstract a large earthquake shock often drops the seismic velocity of the shallow ground however it is not clear whether the dropped velocity recovers shortly after the earthquake shock or not the purpose of this article is to report the time lapse changes of seismic velocity in the shallow ground after the 2000 western tottori earthquake japan we deconvolve the coda record of small earthquakes registered on the ground surface by that registered at the 100 m depth in a borehole at a station that experienced a strong shock from the mainshock because coda waves are mostly composed of randomly scattered s waves deconvolution of the two coda records enables us to obtain a robust image of the ground structure assuming that the shear modulus was reduced at the depth of 0 11 m we estimate the shear modulus change in each time period after the mainshock by fitting synthetic coda deconvolution to the observed one from 1 to 16 hz as a result the shear modulus dropped to 52 of the value obtained before the mainshock a few minutes after the strong earthquake shock this caused a decrease in the s wave velocity of 30 and an increase in s wave travel time of 17 msec the shear modulus continued to recover for over 1 yr following the logarithm of the lapse time it recovered to 69 83 87 and 97 of the value obtained before the mainshock in the periods of 0 to 1 week 1 week to 1 month 1 month to 1 yr and 1 to 4 yr after the mainshock respectively

fault interaction and stress triggering of twentieth century earthquakes in mongolia 1 a cluster of exceptionally large earthquakes in the interior of asia occurred from 1905 to 1967 the 1905 m7 9 tsetserleg and m8 4 bolnai earthquakes the 1931 m8 0 fu yun earthquake the 1957 m8 1 gobi altai earthquake and the 1967 m7 1 mogod earthquake sequence each of the larger m 8 earthquakes involved strike slip faulting averaging more than 5 m and rupture lengths of several hundred kilometers available geologic data indicate that recurrence intervals on the major source faults are several thousands of years and distances of about 400 km separate the respective rupture areas we propose that the occurrences of these and many smaller earthquakes are related and controlled to a large extent by stress changes generated by the compounded static deformation of the preceding earthquakes and subsequent viscoelastic relaxation of the lower crust and upper mantle beneath mongolia we employ a spherically layered viscoelastic model constrained by the 1994 2002 gps velocity field in western mongolia vergnolle et al 2003 using the succession of twentieth century earthquakes as sources of deformation we then analyze the time dependent change in coulomb failure stress f at remote interaction distances static f values are small however modeled postseismic stress changes typically accumulate to several tenths of a bar over time intervals of decades almost all significant twentieth century regional earthquakes m 6 with well constrained fault geometry lie in positive f lobes of magnitude about 0 5 bar our results suggest that significant stress transfer is possible among continental faults separated by hundreds of kilometers and on timescales of decades

volcanology and sedimentology of the host succession to the hellyer and que river volcanic hosted massive sulfide deposits northwestern tasmania the hellyer and que river high grade polymetallic volcanic hosted massive sulfide deposits of western tasmania are hosted by a sequence of late middle cambrian subaqueous mafic to felsic volcanics and volcaniclastics known as the que hellyer volcanics these volcanics occur toward the top of a thicker sequence of mainly felsic volcanics also hosting mineralization known as the mount read volcanics the base of the footwall sequence within the que hellyer volcanics is marked by massive to pillowed basaltic lavas and volcaniclastics of variable thickness these are conformably overlain by a thick sequence of andesitic basaltic and minor dacitic lavas and associated volcaniclastics eruption of these footwall sequences was rapid with breaks in volcanism represented only by thin discontinuous epiclastic horizons a hiatus in volcanism followed the emplacement of the footwall sequences this hiatus is represented by the deposition of locally derived coarse grained mass flows the distribution and geometry of these epiclastics suggest that they accumulated in local syndepositional depressions sedimentation was also accompanied by syngenetic zn pb cu ag au rich mineralization in the central or axial area of these depressions rapid burial by further mass flows assisted in the preservation of mineralization shallow intrusive to extrusive dacitic lava flows and domes in the host horizon were emplaced during and immediately after mineralization autoelastic material from these dacitic domes was then resedimented and incorporated in the epiclastic horizons overlying the orebodies eruption of massive to pillowed basaltic and minor andesitic lavas of the hellyer basalt occurred soon after mineralization and was the final phase of volcanism in the que hellyer volcanics the basalts were emplaced as extrusions and as shallow intrusions into wet fine grained sediments which began to accumulate above the coarse grained epiclastic horizons these basalts buried the remaining parts of the sulfide mound not covered by epiclastics immediately after the cessation of volcanic activity in the area a 100 m thick sequence of black shales and minor sandstones known as the que river shale was deposited the general lack of products of explosive volcanism within the que hellyer volcanics is most likely a function of the composition of the lavas combined with their emplacement in deep water under high confining pressures although the absence of such products does not rule out the possibility of emplacement in shallow water depths the absence of abundant large scale tractional sedimentary structures the presence of the overlying black anoxic que river shale and the mass flow characteristics of elastic units favor a relatively deep water setting for mineralization in the que hellyer volcanics

delayed triggering of the 1999 hector mine earthquake by viscoelastic stress transfer stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases1 2 3 4 5 the 1999 hector mine earthquake in southern california magnitude 7 1 occurred only 20 km from and 7 years after the 1992 landers earthquake magnitude 7 3 this suggests that the hector mine earthquake was triggered in some fashion by the earlier event but uncertainties in the slip distribution and rock friction properties associated with the landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the hector mine hypocentre with estimates varying from 1 4 bar ref 6 to 0 5 bar ref 7 more importantly coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events here we present the results of a three dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the landers earthquake using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the landers earthquake our calculations suggest that lower crustal or upper mantle flow can lead to postseismic stress increases of up to 1 2 bar at the location of the hector mine hypocentre during this time period contributing to the eventual occurrence of the 1999 hector mine earthquake these results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard8 9 10 11

coseismic velocity change in the rupture zone of the 2008 mw 7 9 wenchuan earthquake observed from ambient seismic noise we investigated seismic velocity and structural changes along the long men shan fault associated with the 2008 mw 7 9 wenchuan earthquake using ambient seismic noise data recorded by the regional seismic network of the china earthquake administration we computed cross correlograms of continuous records of station pairs from which we obtained clear rayleigh wave signals at periods of 10 to 25 s we measured the travel speeds of these rayleigh waves from ambient noise data recorded before and after the earthquake and obtained a total of 77 estimates of group velocity along paths running across the rupture zone of the earthquake most of the ray paths showed increasing travel times of rayleigh waves right after the earth quake we inverted the measured differential travel times along different ray paths to constrain regions with significant changes in seismic velocity our 2d tomographic image showed a distinct region with an 0 4 velocity decrease the strike and extension of this region match remarkably well with the deep rupture area of the earth quake because the rayleigh waves that we used in this study travel as deep as 25 km below the surface it is difficult to explain the observed velocity changes solely with shallow damages 100 m resulting from strong shaking numerous laboratory studies have shown that the speed at which seismic waves travel through rocks changes with the level of stress the velocity decrease observed here thus may be caused by a large stress drop associated with the earthquake assuming a stress drop of 3 mpa we obtained a stress sensitivity of 1 3 10 9 pa 1 consistent with both laboratory and field observations our results suggest that time lapse seismic imaging with ambient noise data provides a promising probe for monitoring temporal structural changes at seismogenic depths

deformation at depth associated with the 12 may 2008 mw 7 9 wenchuan earthquake from seismic ambient noise monitoring 1 we track the temporal evolution of seismic wave speed to detect changes in material properties at depth driven by deformation associated with the 2008 mw 7 9 wenchuan earthquake we analyze ambient noise correlation functions to monitor seismic wave speed variations the data were continuously recorded during 2 years by 114 broadband stations in a region that covers the southern two thirds of the ruptured fault we perform the analysis in the 12 to 20 s period band by comparison with measurements in the band 1 to 3 s we show that the seismic velocity changes cannot be explained by a shallow perturbation but are related to deformation at depth in the crust the spatial and temporal characteristics of these variations can thus be viewed as reflecting the middle crust behavior in particular the results suggest that the deformation in the middle crust is different beneath tibet and the sichuan basin

migration of seismic scatterers associated with the 1993 parkfield aseismic transient event the time varying deformation field within a fault zone particularly at depths where earthquakes occur is important for understanding fault behaviour and its relation to earthquake occurrence1 2 3 but detection of this temporal variation has been extremely difficult although laboratory studies have long suggested that certain structural changes such as the properties of crustal fractures should be seismically detectable4 here we present evidence that such structural changes are indeed observable in particular we find a systematic temporal variation in the seismograms of repeat microearthquakes that occurred on the parkfield segment of the san andreas fault over the decade 1987 97 our analysis reveals a change of the order of 10 m in the location of scatterers which plausibly lie within the fault zone at a depth of 3 km the motion of the scatterers is coincident in space and time with the onset of a well documented aseismic transient deformation event we speculate that this structural change is the result of a stress induced redistribution of fluids in fluid filled fractures caused by the transient event

depositional model of a macrotidal estuary and floodplain south alligator river northern australia the south alligator river northern territory of australia has a macrotidal estuary tidal influence spring tidal range 5 6 m at the mouth extends 105 km up the channel it is dominated by freshwater in the wet season december april with a salt wedge near the mouth but is well mixed and becomes saline throughout the dry season the tidal channel can be divided into four different channel types an estuarine funnel a sinuous meandering segment a cuspate meandering segment in which the inside of bends are pointed and an upstream tidal channel the distribution of morphologically defined land classes and morphological units within each land class on the floodplain flanking the estuary differs from one channel type to another several stratigraphic and morphostratigraphic units have been recognized from drill holes on the coastal and deltaic estuarine plains and a model of development is proposed on the basis of extensive radiocarbon chronology and palynology the coastal plain has prograded with most rapid sedimentation between 5000 and 3000 yr bp a similar pattern of progradation is identified in the estuarine funnel in the sinuous segment of the estuary the channel has migrated laterally across the floodplain previous channel positions are indicated by palaeochannels and the meander tract is occupied by laminated channel sediments within the cuspate segment there are numerous sinuous palaeochannels on the plains in the upstream segment the channel and palaeochannels have long straight reaches with irregular bends and discontinuous levees and channel avulsion is indicated mangrove mud is a widespread stratigraphic unit throughout the plains the initial phase of development is a transgressive phase 8000 6800 yr bp when mangrove forests extended landwards into a pre existing valley as sea level rose as sea level stabilized the transgressive phase was followed by a widespread mangrove phase termed the big swamp 6800 5300 yr bp the mangrove forests disappeared from most of the plains as vertical accretion continued and were replaced by grass and sedge covered floodplains during the sinuous phase about 5300 2500 yr bp the channel migrated laterally and eroded the deltaicestuarine plain and deposited lateral accretion deposits laminated channel sediments part of the channel of the south alligator river has then progressed from sinuous to cuspate in form and erosion of river banks has occurred transgressive and big swamp phases occurred under rising and stabilizing sea level respectively later morphodynamic channel adjustments occurred under conditions of stable sea level the depositional model has direct application to other estuaries in northern australia and may be applied to other areas where sea level change has been similar

coseismic and postseismic velocity changes measured by repeating earthquakes 1 repeating earthquakes that rupture approximately the same fault patch and have nearly identical waveforms are a useful tool for measuring temporal changes in wave propagation in the earth s crust since source and path effects are common to all earthquakes in a repeating earthquake sequence multiplet differences in their waveforms can be attributed to changes in the characteristics of the medium we have identified over 20 multiplets containing between 5 and 40 repeating events in the aftershock zones of the 1989 loma prieta and 1984 morgan hill california earthquakes postmain shock events reveal delays of phases in the early s wave coda of as much as 0 2 s relative to premain shock events the delay amounts to a path averaged coseismic velocity decrease of about 1 5 for p waves and 3 5 for s waves since most of the multiplets are aftershocks and follow omori s law we have excellent temporal sampling in the immediate postmain shock period we find that the amplitude of the velocity decrease decays logarithmically in time following the main shock in some cases it returns to the premain shock values while in others it does not similar results are obtained for the morgan hill main shock because the fractional change in s wave velocity is greater than the fractional change in p wave velocity it suggests that the opening or connection of fluid filled fractures is the underlying cause the magnitude of the velocity change implies that low effective pressures are present in the source region of the velocity change our results suggest that the changes are predominantly near the stations and shallow but we cannot exclude the possibility that changes occur at greater depth as well if the variations are shallow we may be detecting the lingering effects of nonlinearity during main shock strong ground motion if the variations are deep it suggests that pore pressures at seismogenic depths are high which would likely play a key role in the earthquake process

rapid human induced siltation of the macro tidal ord river estuary western australia field studies on the sediment dynamics of the two arms of cambridge gulf tropical western australia were undertaken the system is macro tidal with 8 m tides the west arm is the estuary of the durack and pentecost rivers which are largely untouched by human activities the east arm is the estuary of the ord river affected by land clearing which started 100 years ago and by two river dams constructed 30 years ago prior to damming of the ord river the natural flow in all rivers was highly seasonal characterized by small at times negligible flow during the dry season which lasts eight months and occasional river floods during the wet season which lasts four months the river flow has been regulated in the east arm as a result of damming this resulted in suppressing large river floods the salinity intrusion length has decreased by about 50 in the east arm following river damming the east arm has silted measurably over the last 30 years with the stream cross sectional area decreasing by about 50 field and numerical studies suggest that this is due to the dam induced suppression of large river floods which has in turn allowed a greater amount of tidal pumping of sediment into the east arm from cambridge gulf since tidal pumping is increasing as the system is silting the east arm appears to now be geomorphologically unstable as a result of human activities numerical studies suggest it may take as little as 100 years for the ord river to reach a new equilibrium modelling suggests that this equilibrium may be characterized by a salinity intrusion length half that before damming a channel width and depth reduced by 70 and a much stronger tidal asymmetry characterized by an increasing size of the tidal bore the west arm appears to be at equilibrium since there has been no net loss or gain of sediment for the last 111 years tidal dynamics and river floods appear responsible for self scouring this channel

coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements 1 we infer co seismic fault slip during the 2008 mw 7 9 wenchuan earthquake from interferometric synthetic aperture radar insar and gps observations of ground deformation we use alos palsar data from ascending orbits on six tracks and we do not use data that are strongly affected by ionospheric perturbations we use a fault model composed of three planar fault segments of the beichuan fault and one planar segment representing the parallel pengguan fault maximum thrust slip is up to 6 7 m near the surface and occurs in two locations near yingxiu in the south and beichuan in the center of the rupture maximum strike slip is over 4 m and occurs near pingtong and nanba along the northern end of the rupture we find that the ratio of coseismic thrust to strike slip on the beichuan fault decreases from 1 5 to 0 7 from the sw to the ne citation feng g e a hetland x ding z li and l zhang 2010 coseismic fault slip of the 2008 mw 7 9 wenchuan earthquake estimated from insar and gps measurements geophys res lett 37 l01302 doi 10 1029 2009gl041213

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

seismic noise correlations to image structural and mechanical changes associated with the mw 7 9 2008 wenchuan earthquake we locate temporal changes of seismic wave speed and scattering properties of the crust associated with the 2008 mw7 9 wenchuan earthquake to that end we analyze ambient seismic noise records from 2007 until the end of 2008 in the 1 3 s period band and in the 12 20 s period band measured in a region that covers the southern two thirds of the fault activated during the earthquake to locate the changes we use a refined imaging procedure based on the sensitivity of scattered waves to weak perturbations this inverse method uses the radiative transfer approximation to describe the intensity of the noise correlation coda our results show that the largest structural changes are observed northeast of the wenchuan epicenter around the fault zone where aftershocks are distributed the spatial and temporal characteristics of the behavior of the crust at depth around the wenchuan earthquake suggest a postseismic and geology dependent signature of the middle crust we also observe a clear seasonal signature within the sichuan basin at depth that we relate to the heavy rainfalls during the monsoon season this seasonality can also be observed at the surface in form of a waveform decoherence our study highlights that seismic velocity changes and waveform decoherence are independent measurements that are sensitive to different parameters and can thus give complementary information in our study we also point out the value of studying the evolution of the changes at different times in the coda

damage to the shallow landers fault from the nearby hector mine earthquake crustal faults have long been identified as sites where localized sliding motion occurs during earthquakes which allows for the relative motion between adjacent crustal blocks although there is a growing awareness that we must understand the evolution of fault systems on many timescales to relate present day crustal stresses and fault motions to geological structures formed in the past fault zone damage and healing have been documented quantitatively in only a few cases we have been monitoring the healing of damage on the shallow johnson valley fault after its rupture in the 1992 magnitude 7 3 landers earthquake and here we report that this healing was interrupted in 1999 by the magnitude 7 1 hector mine earthquake rupture which occurred 20 30 km away the hector mine earthquake both strongly shook and permanently strained the johnson valley fault adding damage discernible as a temporary reversal of the healing process the fault has since resumed the trend of strength recovery that it showed after the landers earthquake these observations lead us to speculate that fault damage caused by strong seismic waves may help to explain earthquake clustering and seismicity triggering by shaking and may be involved in friction reduction during faulting

use of airborne lidar to investigate mangrove accommodation space in macrotidal estuaries of northern australia abstract extensive mangroves in the northern territory of australia reflect the large tidal range along that coast airborne lidar enables interpretation of ground elevation along transects through mangroves and across coastal and estuarine plains supplementing past levelling surveys of elevation range of the principal mangrove taxa mangrove distribution in the upper intertidal varies geographically in response to tidal variations in the well mapped darwin and bynoe harbours sonneratia alba grows at elevations below mean sea level whereas rhizophora occupies a prominent zone that is inundated by neap tides ceriops is generally found at higher elevations often showing a canopy height gradation a number of mangroves including avicennia occur at the upper bound of the mangrove forest adjacent to the hinterland which occurs at 2 8 m above australian height datum ahd on the open coast and at 3 6 m ahd reflecting tidal amplification in the embayments along the less known macrotidal estuaries of the alligator rivers accommodation space and species distribution varies with distance from the open coast on the coastal plain that has formed along the southern margin of van diemen gulf lidar reveals that landwardmost mangroves also occur up to an elevation of 2 8 m ahd amplification of tides in the cuspate meandering middle sections of the south and east alligator rivers enables mangroves to occur up to 3 5 3 6 m ahd in contrast to the less infilled west alligator river the lidar reveals substrate topography and vegetation structure the rhizophora zone is particularly distinct and its steeper gradient implies rapid sediment accretion rhizophora has played a disproportionately large role in the sequestration of blue carbon low lying parts of these estuarine plains particularly former channels are already experiencing tidal creek extension and saline intrusion and topography of the landscape behind the mangroves will mean many areas will be vulnerable to future salinization in response to rising sea level

link between seismic velocity structure and the 2010 ms 7 1 yushu earthquake qinghai china evidence from aftershock tomography a high resolution 2d horizontal seismic velocity model is presented for the upper crust around the epicenter of the 14 april 2010 m s 7 1 yushu earthquake from aftershock tomography the velocity model is obtained using a simple pn like tomography method including both station and event depth corrections the most striking result is a fast velocity anomaly at the epicenter on the yushu garze fault ygf the main rupture originated within this fast velocity anomaly and propagated southeastward into a slow velocity anomaly at yushu the second largest aftershock on 29 may 2010 on a nearby fault also occurred within this fast velocity anomaly these results demonstrate a clear example that lateral variation in seismic velocity structures of the upper crust controlled the origination stress accumulation and rupture propagation of the 2010 yushu earthquake and distribution of aftershocks as well the simple 2d pg wave travel time tomography method presented here introduces a new approach utilizing abundant aftershocks data for investigating the rupturing process of a major earthquake

nonvolcanic tremors deep beneath the san andreas fault we have discovered nonvolcanic tremor activity i e long duration seismic signals with no clear p or s waves within a transform plate boundary zone along the san andreas fault near cholame california the inferred epicentral region of the 1857 fort tejon earthquake moment magnitude 7 8 the tremors occur between 20 to 40 kilometers depth below the seismogenic zone the upper 15 kilometers of earth s crust where earthquakes occur and their activity rates may correlate with variations in local earthquake activity

long term observation of in situ seismic velocity and attenuation 1 we conducted 1 year continuous measurements of in situ compressional wave velocity and attenuation across a distance of 12 m in a vault at the coast of miura bay japan using a piezoelectric transducer as the ultrasonic wave source we detected for the first time periodic variations in both velocity and attenuation with amplitudes of 0 3 and of 4 respectively corresponding to the diurnal and semidiurnal lunar and solar tides these variations correlate well with the in situ areal strain change due to tidal ocean loading estimated from the strain records about 100 m away from the observational site relative minimum velocity and relative maximum attenuation occur at every time of relative maximum areal strain expansion suggesting that opening closure of pores or cracks of in situ rocks is responsible for these periodic variations the velocity variation shows a remarkable 14 day periodicity corresponding to the spring and neap tides arising from a nonlinear response of the velocity change to tidal strain change such that the velocity change depends on how slowly the tidal dilatation departs from its peak value

remote triggering of fault strength changes on the san andreas fault at parkfield a 20 year seismological record of from the parkfield area of the san andreas fault has been used to identify two occasions when long term changes in fault strength seem to have been induced remotely by large seismic events the 2004 sumatra andaman and the 1992 landers earthquakes in both cases two changes occurred that are consistent with variations in fault strength variation in the properties of seismic scatterers with time reflecting stress induced migration of fluids and systematic variation in the characteristics of repeating earthquake sequences these findings suggest that the largest earthquakes have a global influence on the strength of the earth s fault systems in support of that hypothesis an unusually large number of m 8 earthquakes occurred in the three years following the 2004 sumatra andaman earthquake changes in fault strength over time can increase or decrease the likelihood of failure and the ultimate triggering of seismic events observation of the parkfield area at the san andreas fault over the years 1987 2008 now reveals two occasions the 2004 sumatra andaman earthquake and the 1992 landers earthquake where long term changes in fault strength have probably been induced remotely by large seismic events fault strength is a fundamental property of seismogenic zones and its temporal changes can increase or decrease the likelihood of failure and the ultimate triggering of seismic events although changes in fault strength have been suggested to explain various phenomena such as the remote triggering of seismicity1 there has been no means of actually monitoring this important property in situ here we argue that 20 years of observation 1987 2008 of the parkfield area at the san andreas fault have revealed a means of monitoring fault strength we have identified two occasions where long term changes in fault strength have been most probably induced remotely by large seismic events namely the 2004 magnitude m 9 1 sumatra andaman earthquake and the earlier 1992 m 7 3 landers earthquake in both cases the change possessed two manifestations temporal variations in the properties of seismic scatterers probably reflecting the stress induced migration of fluids and systematic temporal variations in the characteristics of repeating earthquake sequences that are most consistent with changes in fault strength in the case of the 1992 landers earthquake a period of reduced strength probably triggered the 1993 parkfield aseismic transient2 3 4 5 as well as the accompanying cluster of four m 4 earthquakes at parkfield the fault strength changes produced by the distant 2004 sumatra andaman earthquake are especially important as they suggest that the very largest earthquakes may have a global influence on the strength of the earth s fault systems as such a perturbation would bring many fault zones closer to failure it should lead to temporal clustering of global seismicity this hypothesis seems to be supported by the unusually high number of m 8 earthquakes occurring in the few years following the 2004 sumatra andaman earthquake

holocene development of the lower mary river plains northern territory australia extensive coastal and estuarine plains associated with several large seasonal rivers characterize the southern shore of van diemen gulf northern territory australia the mary river is unique among these rivers in that despite a catchment of 7700 km 2 it fails to reach the sea as a discrete channel but breaks up into a series of terminating multiple channels leaving much of the freshwater discharge to evaporate from the plains the extent and morphology of these plains have changed markedly during the holocene drilling radiocarbon dating and pollen analysis indicate a transgressive phase that began about 7000 years ago as the rising seas flooded the prior valley this was followed by a big swamp phase as sea level stabilized around 6000 years ago during which widespread mangrove forest development occurred rapid progradation of the coast occurred between 6000 and 4000 years bp the shoreline has prograded little since that time but has been modified by episodic chenier ridge deposition and palaeochannel abandonment infill and reoccupation the lower mary river differs from adjacent systems in that several former estuarine channels across the plains appear to have become completely blocked with sediment leaving low lying billabongs and palaeochannels which have been preferentially reinvaded by later channels several alternative explanations are examined but it remains unclear what has driven major variations in palaeochannel activity and sedimentation during the mid holocene and why these have decreased so markedly in the last 2000 years

late flandrian holocene tidal palaeochannels gwent levels severn estuary sw britain character evolution and relation to shore abstract the exceptionally well exposed flandrian sediments on the welsh shores of the severn estuary reveal tidal palaeochannel networks uniquely tied to vertically stacked peat silt couplets field relationships show that channels multiplied and were enlarged as each peat organogenic marsh was rapidly transgressed replaced by and buried beneath silt mineralogenic marsh the networks infilled and shrank as the silt marsh later gave way regressively to the next peat marsh simulation and hydraulic models show that this cycle depended on an increase followed by a decrease in the tidal prism imposed on the marsh during a sea level fluctuation coupled patterns of channel width downstream orientation and coarseness of fill suggest that the many networks tied to the final flandrian peat silt couplet cycle iii ranged inland from a marsh edge lying of the order of 2 km seaward from the modern coast

estuarine infill and coastal progradation southern van diemen gulf northern australia abstract there are several estuaries associated with the pronouncedly seasonal rivers which drain northwards from the middle proterozoic sandstone arnhem land plateau and the tertiary koolpinyah land surface into the macrotidal van diemen gulf in the northern territory of australia the holocene development of these investigated in greatest detail for the south alligator river with an upland catchment of 10 000 km2 through drilling palynology and radiocarbon dating comprises both estuarine infill and coastal progradation three phases of estuarine infill can be recognised i a transgressive phase 8000 6800 years b p of marine incursion ii a big swamp phase 6800 5300 years b p of widespread mangrove forest development and iii a sinuous cuspate phase of floodplain development since 5300 years b p during which the tidal river has meandered and reworked earlier estuarine sediments since 6000 years b p the south alligator coastal plain has prograded at a decelerating rate with two phases of chenier ridge formation a similar pattern of estuarine infill and decelerating coastal plain progradation is demonstrated for the adelaide and mary rivers both with catchments of 6000 km2 the southern shore of van diemem gulf appears to have changed its overall position little during the last 2000 years the major source for the clay silt and fine sands which have infilled the estuary and coastal plain has been from seaward dispite the similarity of development coastal sediment build up has had different effects on the morphology of each tidal river the adelaide has undergone a major diversion and no longer flows directly into van diemen gulf but occupies a former fluvial course and the mary has been blocked entirely and its former estuarine palaeochannels have been infilled with tide transported sediment

near surface weakening in japan after the 2011 tohoku oki earthquake 1 the magnitude mw 9 0 tohoku oki earthquake on 11 march 2011 was one of the largest in recent history ground motion caused by the seismicity around the time of the main shock was recorded by kik net the strong motion network that covers most of japan by deconvolving waveforms generated by earthquakes that are recorded at the surface and in a borehole at kik net station fksh18 we detect a reduction of shear wave velocity in the upper 100 m of about 10 and a subsequent healing that varies logarithmically with time using all available borehole and surface records of more than 300 earthquakes that occurred between 1 january 2011 and 26 may 2011 we observe a reduction in the shear wave velocity of about 5 in the upper few hundred meters after the tohoku oki earthquake throughout northeastern japan the area of the velocity reduction is about 1 200 km wide which is much wider than earlier studies reporting velocity reductions following other larger earthquakes the reduction of the shear wave velocity is an indication that the shear modulus and hence the shear strength is reduced over a large part of japan

australia an unstable platform for tide gauge measurements of changing sea levels a reply twenty five tide gauge records non uniformly distributed along the coast of australia were used to evaluate the stability of australia as a platform from which to measure changes in sea levels the spatial and temporal variabilities of relative sea levels were defined using a multivariate analytical tool eigenanalysis on 13 of these stations low frequency period 20 years and greater relative sea levels are believed to reflect the combined effects of subsistence due to sediment and water loading subsidence due to thermal cooling of oceanic crust and emergence along a convergent plate boundary global eustatic sea level rise cannot be identified unambiguously from these data but clearly it is not responsible for the observed patterns of relative sea level the straight average rate of rise of relative sea level around australia is 1 3 mm yr submergence with general submergence in the south at an average rate of 1 8 mm yr and emergence in the north 0 5 mm yr the latter an average of two sta

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

spatiotemporal evolution of a transient slip event on the san andreas fault near parkfield california 1 in 1993 several baselines of the two color electronic distance meter edm network at parkfield california deviated from their long term rates coincident with anomalous observations from nearby strain meters and a creep meter as well as an increase in microseismicity between october 1992 and december 1994 three m 4 5 earthquakes occurred beneath middle mountain near the hypocenter of the 1934 and 1966 parkfield m6 events we analyzed the two color edm data using a kalman filtering based technique to image the spatiotemporal evolution of slip on the fault at parkfield between the mid 1980s and 2003 this method accounts for localized random walk motion of the geodetic monuments and a prominent seasonal signal that affects many baselines we find that a slip rate increase occurred between january 1993 and july 1996 on the upper 8 km of the fault near middle mountain the peak estimated slip rate during this time was 49 mm yr which exceeds the long term geologic rate of 35 mm yr the slip rate evolution appears episodic with an initial modest increase after the m4 3 earthquake and a much larger jump following the shallower m4 7 event in december 1994 this temporal correlation between inferred slip and seismicity suggests that the moderate earthquakes triggered the aseismic fault slip the edm data cannot resolve whether transient slip propagated across the nucleation zone of the 1934 and 1966 m6 parkfield earthquakes however transient slip and its associated stress release in the hypocentral area of previous parkfield events is consistent with the nucleation of the 2004 m6 parkfield earthquake elsewhere on the fault