recurrence behavior of short term slow slip and correlated nonvolcanic tremor episodes in western shikoku southwest japan 1 from the national research institute for earth science and disaster prevention hi net tiltmeter data we determine time dependent source processes of seven repeating short term slow slip events sse in the western shikoku region southwest japan over the period from 2002 to 2007 the tiltmeters record clear signals of sses characterized by a slow rise a week long duration and a magnitude on the order of 10 2 10 1 rad we apply a time dependent slip inversion method to the tilt records for the seven sses for each sse a slip area migrates in the strike direction of the subducting slab at a rate of 10 km d 1 comparing the slow slip area with epicenters of accompanying nonvolcanic tremors in subday time resolution we find that the two phenomena are located on a smaller area than previously reported and migrate as a group a moment rate function for each sse exhibits good correlation with the temporal change in tremor activity a comparison of the slip distributions of all of the analyzed sses shows that there is a patch of slow slip area 30 km in diameter that is shared by all of the episodes in addition the location of the slip patch is in good agreement with the epicenters of tremors and very low frequency earthquakes these lines of evidence suggest that the identified slip patch is one of the main slow slip patches in the region and a recurrence of sses may be controlled by the patch and that these slow earthquakes might be different manifestations of a single slip process on the deep plate interface

the sedimentary structure of linear sand dunes linear sand dunes dunes that extend parallel to each other rather than in star like or crescentic forms are the most abundant type of desert sand dune1 but because their development and their internal structure are poorly understood they are rarely recognized in the rock record2 models of linear dune development2 3 4 5 6 have not been able to take into account the sub surface structure of existing dunes but have relied instead either on the extrapolation of short term measurements of winds and sediment transport or on observations of near surface internal sedimentary structures from such studies it has not been clear if linear dunes can migrate laterally2 7 8 here we present images produced by ground penetrating radar showing the three dimensional sedimentary structure of a linear dune in the namib sand sea where some of the world s largest linear dunes are situated these profiles show clear evidence for lateral migration in a linear dune moreover the migration of a sinuous crest line along the dune produces divergent sets of cross stratification which can become stacked as the dune height increases and large linear dunes can support superimposed dunes that produce stacked sets of trough cross stratification these clear structural signatures of linear dunes should facilitate their recognition in geological records

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

age of desert dunes near birdsville southwest queensland abstract a mild controversy has arisen concerning the age of sand ridges in the eastern simpson desert around birdsville stratigraphic evidence indicates a holocene age but thermoluminescence tl dating of two sand samples from the area gave ages of about 34 ka and almost 78 ka wollongong laboratory in an attempt to resolve the difficulty sand samples were collected and dated by optically stimulated luminescence osl from a dune east of birdsville though low the dune is fully exposed in section so that basal sand as well as sediment from the substrate below the gibber were sampled the substrate gave dates of 36 ka the basal sand about 10 ka and sand from higher levels about 9 ka no younger sand was present and the dune is construed as the clay cemented core of a dune from which loose sand has been stripped by the wind samples of uncemented sand from the crests and flanks of higher dunes and from a clayey lee side mound in the same area gave dates around 1 ka or less

elongation and migration of sand dunes two distinct processes are known to act on dynamic dunes the process of migration by erosion on the windward side and deposition on the lee side typical for transverse dunes and the process of elongation typical for linear dunes these two processes are determined by wind direction relative to the dune alignment this article reviews the assertion that linear dunes experience lateral displacement in addition to elongation fieldwork on vegetated linear dunes vlds and gis work on seif dunes indicates no lateral migration for these dunes linear dunes can shift laterally only when a slip face formed on the lee side reaches the plinth of the dune the winds from both sides of the seif dune are never symmetric usually winds from one direction are more dominant and effective the outcome is the formation of peaks and saddles along the dune the strongest winds create a slip face on the lee side of the peak segments of the dune oblique to the dune alignment which reaches the base of the dune and displaces the peak downwind along the dune alignment the internal structure of the seif dune is formed mostly by this dominant wind direction and gives the impression that the dune has shifted laterally on the other hand there are cases in which the wind directions relative to dune alignment fall between those of transverse and seif dunes in such cases both processes act on the dune which subsequently experiences migration as well as elongation

comprehensive model of short and long term slow slip events in the shikoku region of japan incorporating a realistic plate configuration 1 we numerically simulate slow slip events sses in the shikoku region of japan incorporating the configuration of the subducting plate we adopt a rate and state dependent friction law with cutoff velocities assuming a frictional parameter distribution based on observed long term sses and nonvolcanic tremors that reflects the slip of short term sses our model reproduces recurrences of long and short term sses and segments of short term sses in our simulation short term sses transition from episodic to continuous slip is reproduced this feature is consistent with tremor activity recently reported in both shikoku and cascadia in addition to the long term sses in the bungo channel our model also reproduces newly found long term sses in central shikoku and predicts that these sses recur during the interseismic period between megathrust earthquakes our model comprehensively reproduces various sses and their characteristics as reported in the shikoku region

along strike variations in short term slow slip events in the southwest japan subduction zone 1 short term slow slip events accompanied by nonvolcanic deep low frequency tremors and deep very low frequency earthquakes in southwest japan were investigated systematically by means of ground tilting studies the change in tilt usually lasts for several days by using a genetic algorithm and a least squares method we inverted the data for tilt steps that were caused by slow slip events and were detected by at least four stations situated near the source of the tremor fault parameters were estimated for 54 slow slip episodes that occurred mainly in the western shikoku northeastern kii and tokai regions from 2001 to 2008 in eastern shikoku two slow slip episodes were detected quantitatively for the first time the fault geometries of all the slow slip events were located within the belt like distribution of tremors in the transition zone between the locked and aseismic slip zones at the plate interface of the subducting philippine sea plate the spatial extent of the fault geometry corresponds roughly to the distribution of clusters of nonvolcanic tremors and very low frequency earthquakes the moment magnitudes ranged from 5 4 to 6 2 and the slip was 1 cm for each slow slip event the rate of moment release by the detected slow slip events was 40 60 of the moment accumulation expected from the relative plate motion and it showed regional differences they may reflect the along strike variations in plate convergence and or the characteristic size of the slow slip fault plane on the plate interface

flume experiments on the alignment of transverse oblique and longitudinal dunes in directionally varying flows for more than a century geologists have wondered why some bedforms are orientated roughly transverse to flow whereas others are parallel or oblique to flow this problem of bedform alignment was studied experimentally using subaqueous dunes on a 3 6 m diameter sand covered turntable on the floor of a 4 m wide flume in each experiment two flow directions relative to the bed were produced by alternating the turntable between two orientations the turntable was held in each orientation for a short time relative to the reconstitution time of the bedforms the resulting bedforms were in equilibrium with the time averaged conditions of the bimodal flows dune alignment was studied for five divergence angles the angle between the two flow directions 45 67 5 90 112 5 and 135 the flow depth during all experiments was approximately 30 cm mean velocity was approximately 50 cm s 1 and mean grain diameter was 0 6 mm each experiment continued for 30 75 min during which time the flume flow was steady and the turntable position changed every 2 min at the end of each experiment water was slowly drained from the flume and dune alignment was measured transverse dunes defined relative to the resultant transport direction were created when the divergence angle was 45 and 67 5 and longitudinal dunes were created when the divergence angle was 135 at intermediate divergence angles dunes with both orientations were produced but transverse dunes were dominant at 90 and longitudinal dunes were dominant at 112 5 one experiment was conducted with a divergence angle of 135 and with unequal amounts of transport in the two flow directions this was achieved by changing the orientation of the turntable at unequal time intervals thereby causing the amount of transport to be unequal in the two directions the dunes formed during this experiment were oblique to the resultant transport direction these experimental dunes follow the same rule of alignment as wind ripples studied in previous turntable experiments in both sets of experiments the bedforms developed with the orientation having the maximum gross bedform normal transport the orientation at which the sum of the bedform normal components of the two transport vectors reaches its maximum value in other words the bedforms develop with an orientation that is as transverse as possible to the two flows in those cases where the two flows diverge by more than 90 and transport equal amounts of sand bedforms that are as transverse as possible to the two separate flows will be parallel to the resultant of the two flow vectors although such bedforms have been defined by previous work as longitudinal bedforms they are intrinsically the same kind of bedform as transverse bedforms

lateral migration thermoluminescence chronology and colour variation of longitudinal dunes near birdsville in the simpson desert central australia the longitudinal dunes of the simpson desert in the vicinity of birdsville have been reworked largely during the holocene from dunes deposited up to 80000 years ago or earlier the widespread asymmetry of these roughly northward trending dunes with steeper eastern faces and more gentle western faces supports wind rose data showing sand transporting winds from the southwest obliquely intersecting the dunes while this suggests a change in the wind pattern since the dune field was oriented it does not indicate that the dunes are necessarily shifting leeward eastward as a consequence it is hypothesized that the direction of migration is controlled by the extent to which the dunes are vegetated relatively well vegetated dunes can accrete sand on their gentle stoss slopes and erode on their lee slopes causing them to shift westward and hence obliquely into the wind a condition that probably prevails in wetter regions and during episodes of relatively humid climate in contrast in very dry areas or during arid phases sand can move unimpeded up a sparsely vegetated stoss face and over the crest to form an avalanche or slip face on the lee side thereby causing the dunes to shift eastward despite evidence that longitudinal dune crests can shift laterally to some extent the dunes in the western part of the simpson desert have not migrated either westward or eastward more than 100m or so from their pleistocene cores aeolian transport and partial or complete removal of iron cutans from around quartz grains results in dunes of widely varying colour yet of similar age

formation and age of desert dunes in the lake eyre depocentres in central australia the sand dunes of the deserts surrounding lake eyre record the latest episode of climatic development from the warm humid conditions of the early tertiary to the hot and arid climate prevailing today the dunes are typical seif dunes which rest on a substrate of late pleistocene fluviatile and lacustrine deposits the sand ridges are thus essentially of holocene age although earlier cycles of aridity are evidenced by remnants of older dune fields the dunes are still advancing across the desert plains blocking river channels and causing tracks to be diverted the dune sands are white in the source areas but they become increasingly red downwind due to the development of a hematite coating on the sand grains the dunes derive from sand accumulations bordering the lee side of sand sources such as playas and alluvial plains large numbers of short sand ridges develop from transverse barchan like forms the incipient dunes coalesce downwind from the generating area and progressively fewer but larger dunes evolve from the many small ones variations in dune spacing both along and normal to the dune trend are related to sand supply and reinforcement mechanisms dune height is directly related to the transverse spacing internal structure and observed short term changes in dune asymmetry caused by different wind directions suggest that the dunes are depositional and that once beyond the generating zone the dunes are maintained by a bidirectional wind regime the resultant of the dominant wind directions determines the long axis of the sand ridges and the trend of migration direction several man years of field observations let us reject helicoidal flow regimes as a significant dune forming mechanism

investigating possible gravity change rates expected from long term deep crustal processes in taiwan we propose to test if gravimetry can prove useful in discriminating different models of long term deep crustal processes in the case of the taiwan mountain belt we discuss two existing tectonic models that differ in the deep processes proposed to sustain the long term growth of the orogen one model assumes underplating of the uppermost eurasian crust with subduction of the deeper part of the crust into the mantle the other one suggests the accretion of the whole eurasian crust above crustal scale ramps the lower crust being accreted into the collisional orogen we compute the temporal gravity changes caused only by long term rock mass transfers at depth for each of them we show that the underplating model implies a rate of gravity change of 6 10 2 gal yr 1 a value that increases to 2 10 2 gal yr 1 if crustal subduction is neglected if the accretion of the whole eurasian crust occurs a rate of 7 10 2 gal yr 1 is obtained the two models tested differ both in signal amplitude and spatial distribution the yearly gravity changes expected by long term deep crustal mass processes in taiwan are two orders of magnitude below the present day uncertainty of land based gravity measurements assuming that these annually averaged long term gravity changes will linearly accumulate with ongoing mountain building multidecadal time series are needed to identify comparable rates of gravity change however as gravity is sensitive to any mass redistribution effects of short term processes such as seismicity and surface mass transfers erosion sedimentation groundwater may prevent from detecting any long term deep signal this study indicates that temporal gravity is not appropriate for deciphering the long term deep crustal processes involved in the taiwan mountain belt

lateral migration of linear dunes in the strzelecki desert australia linear dunes in the strzelecki desert trend roughly south north sand transport which is toward the nne has caused the dunes to migrate eastward while they extend or migrate northward eastward lateral migration is evidenced by 1 asymmetrical shape of the dunes east facing slopes are several times as steep as west facing slopes 2 asymmetrical accumulation of loose recently transported sand relatively abundant on east facing slopes 3 asymmetrical outcropping of older semiconsolidated aeolian sand on the dune surface more abundant on west facing slopes and 4 east dipping foreset beds that underly the west facing flanks of some dunes dunes in the strzelecki desert are still active in the sense that sand is transported along and across many dune crests however the dunes are composed primarily of pleistocene strata indicating that the trend of the dunes was established before the holocene the obliquity of the dunes to the transport direction is not merely an aberration of the wind regime of the last few decades preferential accumulation of sand on east facing flanks indicates that the dunes migrated eastward several metres during the holocene moreover the west facing flanks of some dunes have experienced a minimum of tens of metres of erosion this asymmetric erosion and deposition were caused by dune obliquity and lateral migration that may have begun as early as the pleistocene dunes in the strzelecki desert and in the adjacent simpson desert display a variety of grossly different internal structures computer graphics experiments demonstrate that many of these differences in structure can be explained by different angles of climb of the dunes

longitudinal dunes can move sideways longitudinal dunes occur in all major sand areas in the world their dominant mode of migration or extension is considered to be either prevailing or resultant wind parallel the dunes extending downwind via accretion of the terminal nose in the qaidam pendi in northwest china a series of active longitudinal dunes extend downwind at 5 10 m yr 1 internal sedimentary structures examined in the dunes however display beds dipping in one direction rather than two opposed directions as is expected analysis of aerial photographs confirms that these dunes migrate laterally up to three metres per year whilst maintaining a symmetrical longitudinal dune morphology

a gis based reconstruction of late quaternary paleohydrology lake eyre arid central australia lake eyre is the terminal playa in a large closed basin which receives the majority of its moisture from the summer monsoon modern lake eyre receives intermittent floodings at times of increased monsoon intensity generally associated with the la nin a phase of the enso cycle lake eyre was a perennial lake during several phases of increased monsoon activity during the late quaternary specifically about 125 ka 80 ka 65 ka and 40 ka magee 1997 late quaternary environments and palaeohydrology of lake eyre arid central australia unpubl ph d thesis australian national university canberra these lake highstands are reflected by elevated shorelines mapped around lake eyre and to a lesser degree around the frome gregory system to the southeast of lake eyre comprehensive research in the lake eyre catchment over the last several decades has constrained the ages and elevations of these shoreline deposits which now enable us to use digital elevation models to map these paleo lakes by incrementally filling each lake meter by meter the areas and volumes of the paleo lakes are calculated and the paleohydrologic processes including the flow direction across spillovers are reconstructed at the peak 125 ka highstand lake eyre stood at 10 m australian height datum ahd and covered nearly 35 000 km 2 more than three times the area of the current playa together with the frome gregory system it held 430 km 3 of water by contrast the deepest historic filling held 30 km 3 these lake levels represent climatic conditions very different from the modern situation due to discontinuous preservation of the shoreline deposits around the lakes and due to the scale of the lake systems mapping the former levels of lake eyre and the frome gregory system has been impossible prior to the availability of a digital elevation model paramatizing the area volume relationships of water required to fill the lake to varying levels will provide data for quantification of climate and precipitation changes over time h 2003 elsevier b v all rights reserved

a second look at western sinai seif dunes and their lateral migration abstract tsoar et al tsoar h blumberg d g stoler y 2004 elongation and migration of sand dunes geomorphology 57 293 302 reported that seif dunes in the western sinai desert did not migrate laterally between 1973 and 1999 if the planform sinuosities of the dunes are removed by filtering spatial averaging or linear regression however it is evident that the dunes did in fact migrate laterally roughly 13 m during this 26 year period the measured migration distance is 1 2 orders of magnitude greater than the rms co registration error tsoar et al determined for the first and last air photos that were used to map the dunes the western sinai dunes provide another example demonstrating that linear dunes can migrate laterally and they illustrate some of the difficulties in documenting systematic lateral motion lateral migration of a dune can be important geologically or geomorphologically even where migration is too slow to detect from repeated topographic surveys this article explains the wind conditions for the lateral migration of seif dunes in western sinai and the possible wind occurrences that would not lead to such a migration

the australian desert dunefields formation and evolution in an old flat dry continent a new map the first based on interpretation of satellite imagery reveals both the complexityofaustralia sdunefieldsandtheirrelationshipswithtopography climateandsubstrate of the five main sand seas the mallee strzelecki and simpson in eastern australia cover quaternary sedimentary basins whereas the great victoria and great sandy dunefields in the west are formed by reworking of valley and piedmont sediments in a non basinal landscape of low relief ridge and valley topography these dunefields cover large areas of the arid zone and semi arid zone and small areas of dunes in sub humid areas around the margins of the continent reflecting past expansion of arid climates during glacial stages of the last several glacial cycles several areas of low relief stand out as being largely dune free the limestone nullarbor plain clay plains of the georgina basin and floodplains of rivers in the carpentaria lake eyre and murray darling drainage basins where sand is rare or not transported by diminished late quaternary rivers the yilgarn block of southwestern australia is also surprisingly free of dunes possibly as a result of long deep weathering everywhere the history of climate change is evident in dune morphology and distribution including large areas where the sand dune orientations are markedly divergent from modern sand moving wind directions

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

the age of the palaeodunefield of the northern murray basin in south australia preliminary results abstract a vast field of old desert dunes extends from northwestern eyre peninsula across yorke peninsula and the northern adelaide plains into the murray basin and northwestern victoria there are patches of parabolic forms but the sand ridges under review are of seif linear or longitudinal type they trend nw se in the west and west east in the east here we record luminescence dates for three dune sites in the waikerie district of the northwestern murray basin they range from respectively 151 25 3 ka 157 33 3 ka and a basal age of 59 6 ka with sand movement also indicated around 1906 and 1933 ce apart from the last named no unconformities are discernible in the sampled sections

slip rate and tremor genesis in cascadia at many plate boundaries conditions in the transition zone between seismogenic and stable slip produce slow earthquakes in the cascadia subduction zone these events are consistently observed as slow aseismic slip on the plate interface accompanied by persistent tectonic tremor however not all slow slip at other plate boundaries coincides spatially and temporally with tremor leaving the physics of tremor genesis poorly understood here we analyze seismic geodetic and strainmeter data in cascadia to observe for the first time a large tremor generating slow earthquake change from tremor genic to silent and back again the tremor falls silent at reduced slip speeds when the migrating slip front pauses as it loads the stronger adjacent fault segment to failure the finding suggests that rheology and slip speed regulated stressing rate control tremor genesis and the same section of fault can slip both with and without detectable tremor limiting tremor s use as a proxy for slip

the role of effective normal stress frictional properties and convergence rates in characteristics of simulated slow slip events slow slip events sses observed in subduction zones around the world exhibit a wide range of recurrence intervals durations and propagation speeds to illuminate possible mechanisms responsible for the observed variability and guide future modeling efforts we employ the earthquake simulator rsqsim to explore the effects of variations in the convergence rates frictional parameters and effective normal stress on sse characteristics both recurrence intervals and durations of sses are essentially directly proportional to the effective normal stress while along strike propagation speeds are inversely proportional effective normal stresses in the range of 3 9 mpa produce fault slip consistent with observed sses changes in rate state frictional instability b a have a moderate inverse effect on propagation speeds but much weaker effects on recurrence intervals and durations convergence rates are inversely proportional to recurrence intervals propagation speeds show a weak positive relationship and event durations appear insensitive

aeolian and fluvial evidence of changing climate and wind patterns during the past 100 ka in the western simpson desert australia abstract sediments near finke in central australia provide evidence of late quaternary evolution and the interaction of aeolian and fluvial systems in response to changing climate in the western simpson desert thermoluminescence tl dating is used to develop a chronology of aeolian and alluvial activity and to identify differences in sand provenance quaternary alluviation in the finke valley at this location occurred at or prior to c 90 ka and with no surviving evidence of subsequent activity until the holocene in contrast to rivers in the eastern part of the lake eyre basin substantial alluviation took place here in the early to mid holocene probably due to reactivation of the northern monsoon and its partial penetration into central australia the regional dunefield near finke consists of linear dunes largely reworked and aligned during the last glacial 30 12 ka as part of the great anticlockwise whorl of dunes in central australia the oldest dated source bordering dunes from the finke river are bright red in colour were deposited at c 100 ka and are now buried beneath paler source bordering dunes the latter consist of two exposed units a lower one of unknown orientation that dates at 17 9 ka and an upper unit aligned to the northwest and parallel to the prevailing winds that dates at 5 0 ka the tl signature and sediment texture of the oldest source bordering dunes show them to have probably been derived from weathered alluvial red beds of similar or greater age nearby and to have contributed abundant sand to the regional dunefield immediately north of the river in contrast sand from the younger paler source bordering dunes appears to be from a different source and to have only recently extended into the regional field the finke region would seem to be in a pivotal position for the study of palaeowind patterns that have created and modified australia s whorl of continental dunes the 30 18 ka regional linear dunes near finke are oriented almost due north their cross sectional asymmetry steeper eastern slopes suggests a response to southwesterly or westerly sand transporting winds between 18 and 10 ka these winds appear to have shifted to their present southeast orientation during the past 5 ka from dune ages alignments and asymmetry it is proposed here that there was a northward shift in the wind pattern at finke by about 100 150 km 1 1 5 of latitude during the last glacial but that through this period the regional dune pattern has remained remarkably stable

okinawa trough backarc basin early tectonic and magmatic evolution the okinawa trough lying between japan and taiwan is a backarc basin formed by extension within the continental lithosphere behind the ryukyu trench arc system stress directions associated with the two last extensional phases in the southwestern okinawa trough have been deduced from a comparison with analog modeling the direction of extension is n 150 o for the pleistocene phase of extension 2 0 1 ma and n 170 o for the late pleistocene holocene phase of extension 0 1 0 ma the present day ryukyu volcanic arc a narrow continuous feature extending from japan to taiwan is located on the eastern side of the okinawa trough 80 100 km above the wadati benioff zone the minimum depth for emplacement of arc magmatism scarce present day backarc volcanism appears in the middle and southern okinawa trough within linear en echelon bathymetric depressions a n045 o oriented seamount volcanic chain cuts across obliquely the southwestern okinawa trough and lies in the direct line of extension of the gagua ridge a n s linear volcanic feature of the philippine sea plate associated with this extension of the gagua ridge a large reentrant located at the base of the ryukyu prism the uplift of part of the nanao forearc basin and the deformation of the sedimentary arc suggest that the voluminous cross backarc volcanism could be tied to the subduction of the gagua ridge located there at a depth of 80 100 km beneath the backarc basin a second area of anomalous volcanism has been identified in the middle okinawa trough in the ene extension of the daito ridge a wnw ese 400 km long volcanic feature of the philippine sea plate we suggest that the gagua and daito ridges initially induced stress at the base of the arc which is still brittle and cracks propagated through the overlying brittle lithosphere allowing magmas with arc affinities to erupt at the seafloor this excessive magmatism reaches the seafloor through conduits which preferentially follow in their shallowest portion the crustal normal faults of the backarc rifts the okinawa trough is consequently still in an early stage of evolving from arc type to backarc activity

the simpson strzelecki and tirari deserts development and sand provenance abstract sands of the simpson strzelecki and tirari deserts central australia can be divided into two main groups on the basis of their physical and chemical characteristics colour grainsize heavy minerals quartz oxygen isotope composition zircon u pb ages the first group encompasses the strzelecki tirari and southeastern simpson deserts while the second occupies the northern and the western simpson desert the boundary between the two groups corresponds approximately to the northern most extent of the kallakoopah lakes several lines of evidence suggest derivation of the sands mainly from local bedrock with very little subsequent aeolian transport ultimate protosources for the sands in order of importance are for the southeastern simpson tirari and strzelecki deserts the tasman orogenic system new england and lachlan fold belts georgetown inlier musgrave and arunta blocks gawler and curnamona cratons and for the north and western simpson desert arunta musgrave and mount isa blocks and tennant creek inlier sediment from the tasman orogenic system includes an additional exotic component from palaeozoic sediments probably derived mainly from antarctica sediment transport from these protosources across the several hundred kilometres to the surficial sedimentary basins was dominantly by fluvial not aeolian means quaternary aeolian transport or reworking has been minimal serving only to form the dunes by vertical corrasion of underlying sedimentary rocks or residual products of local basement weathering the deserts have received some recent localised sediment input from modern fluvial systems

bedform alignment in directionally varying flows many kinds of sediment bedforms are presumed to trend either normal or parallel to the direction of sediment transport for this reason the trend of bedforms observed by remote sensing or by field observations is commonly used as an indicator of the direction of sediment transport such presumptions regarding bedform trend were tested experimentally in bidirectional flows by rotating a sand covered board in steady winds transverse oblique and longitudinal bedforms were created by changing only two parameters the angle between the two winds and the proportions of sand transported in the two directions regardless of whether the experimental bedforms were transverse oblique or longitudinal as defined by the bedform trend relative to the resultant transport direction they all had trends that yielded the maximum gross transport across the bedforms the fact that many of the experimental bedforms were neither transverse nor parallel to the resultant transport direction suggests that transport directions cannot be accurately determined by presuming such alignment

space time correlation of slip and tremor during the 2009 cascadia slow slip event 1 episodic tremor and slip ets involving transient deformations accompanied by emergent low frequency tremor occurs in subduction zones around the world ets events increase the shear stress on locked megathrusts and may potentially trigger damaging earthquakes despite the clear association of tremor and slip the physical relationship between them is unresolved tremor appears to result from slip on small asperities on the plate interface due to either creep on the surrounding fault or stress increases ahead of the propagating slow slip front previous studies of migrating slow slip events have not had sufficient spatial and temporal resolution to differentiate between these two models to address this we invert gps data from the august 2009 ets event in central cascadia for the space time evolution of fault slip rate we find a correlation in both space and time between tremor epicenters and the independently determined position of high fault slip rate this supports the first hypothesis that tremor asperities are loaded directly by slow slip rather than by stress increases ahead of the slip front and provides new insights into the mechanics of ets

real data assimilation for optimization of frictional parameters and prediction of afterslip in the 2003 tokachi oki earthquake inferred from slip velocity by an adjoint method