the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

three dimensional splay fault geometry and implications for tsunami generation megasplay faults very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism are thought to play a role in tsunami genesis we imaged a megasplay thrust system along the nankai trough in three dimensions which allowed us to map the splay fault geometry and its lateral continuity the megasplay is continuous from the main plate interface fault upwards to the sea floor where it cuts older thrust slices of the frontal accretionary prism the thrust geometry and evidence of large scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time contrary to the usual seaward progression of accretionary thrusts the megasplay fault has progressively steepened substantially increasing the potential for vertical uplift of the sea floor with slip we conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis such as the 1944 moment magnitude 8 1 tonankai event and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis

keeping the edge a numerical method that avoids knickpoint smearing when solving the stream power law the stream power equation is commonly used to model river incision into bedrock although specific conditions allow an analytical approach finite difference methods fdms are most frequently used to solve this equation fdms inevitably suffer from numerical smearing which may affect their suitability for transient river incision modeling we propose the use of a finite volume method fvm which is total variation diminishing tvd to simulate river incision in a more accurate way the tvd fvm is designed to simulate sharp discontinuities making it very suitable to simulate river incision pulses we show that the tvd fvm is much better capable of preserving propagating knickpoints than fdms using niagara falls as an example comparison of numerical results obtained using the tvd fvm with analytical solutions shows a very good agreement furthermore the uncertainty associated with parameter calibration is dramatically reduced when the tvd fvm is applied the high accuracy of the tvd fdm allows correct simulation of transient incision waves as a consequence of older uplift pulses this implies that the tvd fvm is much more suitable than fdms to reconstruct regional uplift histories from current river profile morphology and to simulate river incision processes in general

paleotsunami research along the nankai trough and ryukyu trench subduction zones current achievements and future challenges abstract located near japan s most densely populated and industrially active region the nankai trough subduction zone has long been highlighted as a high risk area for damaging earthquakes and tsunamis in contrast less attention has been paid the adjacent ryukyu trench because historical and geological records are scarce in order to develop better quantitative estimates of the timing and size of the earthquakes and tsunamis generated along these subduction zones comprehensive studies using geological seismological and historical methods have been conducted since the 1990s studies of tsunami deposits in this region have contributed to our current understanding of the history of tsunamis over the last 6000 years following the 2011 t hoku earthquake and tsunami paleotsunami research has especially focused on guiding and enhancing tsunami disaster management and mitigation measures the last nine years have seen a rapid increase in paleotsunami data from the nankai trough and ryukyu trench coasts these recent studies reveal that there are significant differences in the size and recurrence pattern of earthquakes and tsunamis along these subduction zones for instance large earthquakes have repeatedly occurred along the nankai trough every 100 200 years on the other hand large earthquakes and tsunamis may not have occurred over the last few thousand years at the junction between these subduction zones there is also no evidence for the occurrence of large earthquakes along the northern and central ryukyu trench over this time period large earthquakes and tsunamis may have occurred every few hundred years at the southern end of the ryukyu trench nevertheless data on the occurrence of these earthquakes are still insufficient both in quantity and quality to estimate the maximum size or recurrence pattern

the discovery of emerged boring bivalves at cape omaezaki shizuoka japan evidence for the 1361 ce tokai earthquake along the nankai trough abstract this study found several in situ fossil shells of the boring bivalve penitella gabbii exposed in mudstone at an elevation of 1 05 1 35 m above mean sea level in a wave cut platform at cape omaezaki shizuoka central japan this region faces the nankai trough where great earthquakes m 8 occur with a recurrence interval of 90 200 years based on the upper limit of living p gabbii 0 8 m above mean sea level and geodetic data the total uplift of shells since the time of their active is estimated to be up to 2 5 m using 14c dates from the uplifted terrace deposits around the study area and shell fossils we propose that the emerged fossils provide new evidence for the pairing of the 1361 ce shohei koan tokai earthquake rupture of suruga trough and the eastern half of the nankai trough with the 1361 ce shohei koan nankai earthquake rupture of the western half of the nankai trough

anthropogenic influences on changes in the sediment load of the yellow river china during the holocene using data on formation of the loess plateau of central china loess palaeosol sequences pollen analysis historical geography and long term experimentation on rates of soil erosion it is demonstrated that current serious erosion on the loess plateau is mainly due to human destruction of the natural vegetation and irrational land use these two modifications greatly reduce soil infiltration capacity and resistance of the soil to erosion the increase of soil erosion began ca 5000 bp at which time a hunting and pastoral life began to change gradually to a sedentary life centred around cultivation using the volume of holocene loessic sediments on the continental shelf of the bohai yellow and east china seas it is estimated that the present sediment load of the lower yellow river is at least three times greater than it was during the holocene although human induced soil erosion in the loess plateau began earlier it was not until the tang dynasty about 1000 bp that it began to increase rapidly ac

a revised tsunami source model for the 1707 hoei earthquake and simulation of tsunami inundation of ryujin lake kyushu japan 1 based on many recent findings such as those for geodetic data from japan s geonet nationwide gps network and geological investigations of a tsunami inundated ryujin lake in kyushu we present a revised source rupture model for the great 1707 hoei earthquake that occurred in the nankai trough off southwestern japan the source rupture area of the new hoei earthquake source model extends further to the hyuga nada more than 70 km beyond the currently accepted location at the westernmost end of shikoku numerical simulation of the tsunami using a new source rupture model for the hoei earthquake explains the distribution of the very high tsunami observed along the pacific coast from western shikoku to kyushu more consistently a simulation of the tsunami runup into ryujin lake using the onshore tsunami estimated by the new model demonstrates a tsunami inundation process inflow and outflow speeds affect transport and deposition of sand in the lake and around the channel connecting it to the sea tsunamis from the 684 tenmu 1361 shokei and 1707 hoei earthquakes deposited sand in ryujin lake and around the channel connecting it to the sea but lesser tsunamis from other earthquakes were unable to reach ryujin lake this irregular behavior suggests that in addition to the regular nankai trough earthquake cycle of 100 150 years there is a hyperearthquake cycle of 300 500 years these greater earthquakes produce the largest tsunamis from western shikoku to kyushu

incised channels and gully erosion in northern iberian peninsula controls and geomorphic setting abstract gully erosion has scarcely been reported in the cantabrian cordillera northern iberian peninsula even though this phenomenon is relatively frequent in this mountain range a total of 133 permanent channels with evidences of gully erosion have been mapped in a 71 8 km2 study area on the northern slope of this mountain range the underlying ordovician unit comprises quartzite sandstone and slate which are partially mantled by different surficial deposits the relief is fairly steep with average slopes of 27 and hillsides with level drops of the order of 700 m and generally vegetated by atlantic heaths a result of the degradation suffered by the natural vegetation following forest fires the mapped channels present different morphological features shallow and deep channels some of them with associated ravines and are usually related to headcut in first and second order pre existing channels although some of them are located on unchanneled hillsides with no evidence of pre existing channels moreover lower reaches of first and second order channels are often incised into bedrock a field description and morphometric study has been carried out on channels affected by gully erosion based on their cartography digital terrain models and several layers of thematic mapping this study describes some of the relations between relief factors the type of substratum and the development of gully erosion i there are robust correlations between morphometry relief and erosion intensity and ii gullying is strongly influenced by the presence of a deep regolith the erosion forms observed and the described relations suggest that gully development is associated to landsliding processes which are ultimately controlled by ground water movement through a porous regolith regional uplift and deforestation are argued to be the most likely causes of channel incision and gullying

preparing for the future nankai trough tsunami a data assimilation and inversion analysis from various observational systems the future nankai trough tsunami is one of the imminent threats to the japanese coastal communities that could potentially cause a catastrophic event as a part of the countermeasure efforts for such an occurrence this study analyzes the efficacy of combining tsunami data assimilation da and waveform inversion wi the da is used to continuously refine a wave field model whereas the wi is used to estimate the tsunami source we consider a future scenario of the nankai trough tsunami recorded at various observational systems including ocean bottom pressure obp gauges global positioning system gps buoys and ship height positioning data since most of the obp gauges are located inside the source region the recorded tsunami signals exhibit significant offsets from surface measurements due to coseismic seafloor deformation effects such biased data are not applicable to the standard da but can be taken into account in the wi on the other hand the use of wi for the ship data may not be practical because a considerably large precomputed tsunami database is needed to cope with the spontaneous ship locations the da is more suitable for such an observational system as it can be executed sequentially in time and does not require precomputed scenarios therefore the combined approach of da and wi allows us to concurrently make use of all observational resources additionally we introduce a bias correction scheme for the obp data to improve the accuracy and an adaptive thinning of observations to determine the efficient number of observations

possible splay fault slip during the 1946 nankai earthquake this paper considers seafloor deformation associated with the 1946 nankai earthquake which occurred in the nankai trough subduction zone off the coast of southwest japan we note that recent high resolution determinations of the slip distribution assumed to be confined to the plate boundary result in a pronounced maximum in seafloor displacement midway between the coast of shikoku and the trough axis we show that this feature could be due to slip on a splay fault rather than the plate boundary such a model for the western part of the slip distribution is able to account for the main features of the tsunamigenic seafloor deformation obtained in previous studies with a maximum slip consistent with the plate convergent rate and history of earthquake recurrence at the nankai trough

the palaeolimnology of the aral sea a review abstract formerly the fourth largest inland water body in the world the volume and area of the aral sea have decreased dramatically over the past 30 yr largely as a result of human actions throughout its approximately 2 million year history the fate of this water body has been intimately linked with that of its two main in flowing rivers the amu darya and the syr darya we present a review of the hydrological palaeontological and sedimentological evidence for the evolution of the aral sea based largely on russian literature although the structure of the aral basin can be traced back to the late neogene the sea has only existed in its present form for the past 8 10 ka and the holocene history has been shaped by regional climatic variations the development of the associated drainage system and anthropogenic forces past hydrological changes in the aral basin have led to systematic shifts in the level of the aral sea which are reflected sedimentologically through the deposition of transgressive and regressive sedimentary units and geomorphologically through the development of terraces all the above data are integrated to produced a late quaternary history of this important water body

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

modelling gully erosion for a small catchment on the chinese loess plateau the rolling hills region of the chinese loess plateau is one of the areas with the highest erosion rates on earth a striking feature of this area is the occurrence of many large permanent gullies a 3 5 km2 catchment was selected to study the processes of erosion and to adapt the storm based limburg soil erosion model lisem to the conditions prevailing on the loess plateau part of this work consisted of mapping and measuring the largest gully headcuts the amount of loose soil material beneath the headcuts was also estimated observations suggest that gully headcuts are relatively stable i e do not migrate rapidly but that gullies can nevertheless produce significant amounts of sediment during overland flow events erosion of headcuts occurs mainly by soil falls in between storms the loose soil material produced by these soil falls accumulates on the gully bottom as the lisem simulates storm erosion the development of gullies over time can be ignored and only the amount of material produced by them during runoff events needs to be studied a digital elevation model dem was used to estimate the position of existing gully heads by applying an adapted form of the montgomery and dietrich science 255 1992 826 index using the assumption that headcuts are vertical it is possible to calculate headcut height from the slope angle map a simple stability model which assumes soil falls on gully headcuts to be a function of soil moisture content and headcut height was applied this daily based model can then be used to simulate the accumulation of loose soil material below the headcut the results show that while the dem is not accurate enough to allow the detection of individual headcuts this method can be used to produce a reasonable estimate of the amount of loose soil material available a map showing the amount of loose soil material accumulated can then serve as input for a storm based erosion model such as lisem

variations in sediment sources and yields in the finger lakes and catskills regions of new york the proportional contributions of stream bank and surface sources to fine sediment loads in watersheds in new york state were quantified with uncertainty analysis eroding streamside glacial drift including glaciolacustrine deposits were examined to help explain variations in the proportional contributions made by bank erosion sediment sources were quantified by comparing concentrations of the bomb derived radionuclide 137 cs in fluvial sediment with sediment from potential source areas such as agricultural soils forest soils and stream banks to compare sediment sources in streams containing abundant deposits of fine grained glacial drift with watersheds that lacked moderate or extensive streamside deposits samples were taken from 15 watersheds in the region the mean contribution of bank erosion to sediment loads in the six streams with glaciolacustrine deposits was 60 range 46 76 the proportional contribution of bank erosion was also important in one stream lacking glaciolacustrine deposits 57 but was less important in the remainder with contributions ranging from 0 to 46 data from this study on the varying contributions of bank erosion and data from past studies of sediment yield in 15 watersheds of new york state suggest that eroding streamside glacial deposits dominate sediment yield in many watersheds in other watersheds past impacts to streams such as channelization have also resulted in high levels of bank erosion copyright 2007 john wiley sons ltd

partitioning between seismogenic and aseismic slip as highlighted from slow slip events in hyuga nada japan 1 we present a numerical method to analyze the gps data and examine slow fault slips in hyuga nada a region in western japan where the philippine sea plate subducts under the eurasian plate and earthquakes of magnitude 7 class are frequent we found that after two large earthquakes in 1996 a slow fault slip expanded from the source area to the north and then triggered another slow event with a characteristic source duration of about one year the aseismic slip has increasingly highlighted a particular site where little slow fault slip takes place but where the subducting plate drags the overriding plate it is noteworthy that the highlighted area is just the site of a past large earthquake we propose that this area is a possible site for a future large earthquake

vegetation cover and topography rather than human disturbance control gully density and sediment production on the chinese loess plateau abstract the factors controlling topsoil erosion rates on the chinese loess plateau clp are currently relatively well understood and topsoil erosion rates can now be relatively accurately estimated this is however not the case for non topsoil erosion sediment production by gullying and landslides while it is well known that these processes produce significant amounts of sediment the factors controlling their intensity and spatial distribution on the clp are less well understood in this study we quantified the contribution of non topsoil erosion to total sediment production on the clp and investigated which factors control spatial and temporal variations in non topsoil erosion we estimated non topsoil erosion rates e nt by comparing the measured average sediment yields of 46 gauged catchments for the 1950 1970 period when soil conservation measures were nearly absent in the area with predicted topsoil erosion rates using a recently developed empirical model in addition gully density was estimated in each catchment using google earth data our results showed that the area weighted average catchment erosion rate e and e nt were 58 60 51 80 and 48 68 49 78 t ha 1 yr 1 respectively for the studied catchments the sediment contribution of non topsoil erosion to total sediment production ranged between ca 0 and 97 with a mean of 70 25 both e and e nt were significantly correlated to longitudinal river slope land use ndvi and gully density however gully density was the only variable explaining a major part of the variance in both e 60 and e nt 57 gully density itself was significantly related to topography and vegetation cover but not to rainfall erosivity importantly gully density was not only related to overall slope steepness but also to the longitudinal slope of the river network and the hypsometric integral suggesting that not only land cover disturbance but also tectonic uplift controls gully density and erosion rates the absence of a clear climate signal both with respect to the variation in gully density and in e can be explained by the overwhelming effect that climate has on vegetation cover our research showed that non topsoil erosion processes are the dominant sediment sources on the clp and are strongly controlled by natural factors the effect of human disturbance on non topsoil erosion processes is far less important than its effect on topsoil erosion given the dominance of non topsoil erosion processes on the clp this suggests that the high sediment production of the clp is mainly attributable to natural factors

imaging of the subducted kyushu palau ridge in the hyuga nada region western nankai trough subduction zone abstract we performed 3d seismic tomography of the hyuga nada region western nankai subduction zone to investigate the relationship of the subducted part of kyushu palau ridge kpr to coseismic rupture propagation seismicity and shallow very low frequency earthquakes combining active source and passive source data recorded both onshore and offshore we imaged the deep slab from near the trough axis to the coastal area our results show the subducted kpr as a low velocity belt oriented nw se extending down the plate boundary to around 30 km depth at this depth we suggest that the subducted kpr detaches from the slab and becomes underplated on the overriding continental plate as the coseismic slip areas of past large earthquakes do not extend into the subducted kpr we suggest that it may inhibit rupture propagation the interior of the subducted kpr shows active intraslab seismicity with a wide depth distribution shallow very low frequency earthquakes are continuously active above the location of the subducted kpr whereas they are intermittent to the northeast of the subducted kpr thus the subducted kpr appears to be an important factor in coseismic rupture propagation and seismic phenomena in this region

depth distribution of coseismic slip along the nankai trough japan from joint inversion of geodetic and tsunami data coseismic slip distribution on the fault plane particularly in the downdip direction associated with large subduction earthquakes can be estimated by joint inversion of geodetic and tsunami data two large earthquakes the 1944 tonankai earthquake mw 8 1 and the 1946 nankaido earthquake mw 8 3 occurred on the nankai trough southwestern japan where the philippine sea plate is subducting beneath the eurasian plate the source areas of these events extended over both land and ocean coseismic crustal movements on land were measured by leveling while those in ocean were recorded as tsunami waveforms on tide gauges the coseismic slip distribution inverted from these data shows that the slip on the shallower part of the fault plane is comparable to that on the deeper parts this indicates that large coseismic slip can occur beneath an accretionary wedge where current seismicity is low the result has implications for other subduction zones having a similar tectonic environment such as for the pacific northwest region of the united states although the possibility of a large earthquake there is still debated should a large subduction earthquake occur in this region coseismic slip on the shallow part could be large and the potential for large tsunamis is high

pleistocene paleoenvironmental evolution at continental middle latitude inferred from carbon and oxygen stable isotope analysis of ostracodes from the guadix baza basin granada se spain abstract a representative paleoenvironmental reconstruction of continental middle latitude from ca 2 my to the upper part of middle pleistocene 279 77 ky was obtained from the carbon and oxygen stable isotopes analyzed in ostracode shells cyprideis torosa recovered in the guadix baza basin se spain an intramontaneous closed depression filled by alluvial and lacustrine sediments this study was performed along a 356 m thick composite section dated previously by paleomagnetism and the amino acid racemization method 13c and 18o profiles reflected changes in temperature the evaporation infill ratio in the water bodies and the amount of rain 13c is also affected by changes in plant biomass periods with high 13c and 18o values are associated with warm and dry regimes and with less vegetation which in some cases coincide with the development of displacive gypsum crystals whereas low 13c and 18o values correlate with cold and humid episodes which cause more vegetation biomass and therefore increasing the input of isotopically light carbon intermediate 18o values are linked to temperate dry or humid episodes when they coincide with high or low 13c values respectively 86 paleoclimatic events were distinguished in the pleistocene record from the 13c and 18o profiles from both the statistical analysis of the geochemical data and the geological observations four cold and humid long periods low 18o and four warm and dry long periods high 18o were defined this differs with respect to the paleoclimatological behavior established for the northern hemisphere where during cold periods glacial no water was available while permafrost conditions persisted whereas in warm episodes interglacial higher precipitation rates occurred good correspondences between the guadix baza basin paleoclimatic record and a marine oxygen isotope sequence two continental cores and other long mediterranean paleoenvironmental records pollen sequences from israel were found which suggested that climate changes in the guadix baza basin were in tune with global climatic changes

gully formation and the role of valley floor vegetation southeastern australia attempts to understand the causes of gully erosion have been hampered by a poor understanding of quantitative changes to the force of flows and the resistance to scour we used flume experiments on an unincised valley floor to determine flow resistance and the critical shear stress for scour under natural and degraded vegetation covers applying the results to sites of gully formation in southeastern australia demonstrates the crucial role that reduced vegetation cover plays in increasing the susceptibility of valleys to channel incision widespread and rapid gully formation in the 19th century required degradation of valley floor vegetation and was not solely the result of land use or climatically induced increases in discharge

establishing a holocene sediment budget for the river dijle abstract a holocene sediment budget was constructed for the 758 km 2 dijle catchment in the belgian loess belt in order to understand long term sediment dynamics hillslope sediment redistribution was calculated using soil profile information from 809 soil augerings which was extrapolated to the entire catchment using morphometric classes as large parts of the forests within the catchment prove to have undergone little or no erosion since medieval times a correction was applied for the presence of forests total holocene erosion amounts 817 66 mt for the catchment of which 327 34 mt was deposited as colluvium this corresponds with a net holocene soil erosion rate of 10 8 0 8 10 3 mg ha 1 for the entire dijle catchment alluvial deposits were studied through 187 augerings spread over 17 cross valley transects the total alluvial sediment deposition equals 352 11 mt or 42 of total eroded sediment mass results indicate that at the scale of a medium sized catchment the colluvial sediment sink is as important as the alluvial sediment sink and should not be neglected as a result the estimation of erosion through alluvial storage and sediment export would yield large errors dating of sediment units show an important increase in alluvial deposition from medieval times onwards indicating the important influence of agricultural activities that developed from that period mean sediment export rates from the catchment for the last 1000 1200 years range between 0 8 and 1 3 mg ha 1 a 1 and are consistent with present suspended sediment measurements in the dijle erosion for agricultural land for this period is 9 2 2 2 mg ha 1 a 1 sediment budgets for the various tributary catchments provide an insight in the sources and sinks of sediment at different scales within the catchment

holocene floodplain sediment storage and hillslope erosion within the rhine catchment the response of fluvial systems to land use and climate change varies depending on catchment size while forcing response mechanisms of small catchments are reasonably well understood the response of larger drainage basins is less clear in particular the impact of land use and climate change on the rhine system is poorly understood because of the catchment size 185 000 km 2 and the long history of human cultivation which started approximately 7500 years ago a sediment budget is calculated to specify the amount of alluvial sediment that was deposited during the holocene and to estimate long term soil erosion rates the results suggest that 599 14 10 9 t of holocene alluvial sediment is stored in the non alpine part of the rhine catchment south and central germany eastern france the netherlands about 50 of holocene alluvial sediment is deposited along the trunk valley and the delta upper rhine lower rhine coastal plain while the rest is stored along the tributary valleys the floodplain sediment storage corresponds to a mean erosion rate of 0 559 0 16 t ha per yr 38 59 10 7 mm kyr across the rhine catchment outside the alps this holocene averaged estimate amounts for sediments that were delivered to the channel network and is at the lower limit of erosion rates from other studies of different methodology

strontium content of ostracods indicates lacustrine palaeosalinity individual non marine ostracod valves contain sr in proportion to the sr content of their host lake water two commonly coexisting large planktonic species mytilocypris praenuncia and australocypris robusta have a sr distribution coefficient kd sr ca of 0 082 which is independent of temperature in the range 10 18 c if the relationship between salinity and the sr content of a hydrologically simple lake is known palaeosalinities can be calculated from fossil ostracods we present here palaeosalinities for the past 10 000 yr for lake keilambete victoria calculated from ostracod sr ca of fossil material which are in striking agreement with independent interpretations of palaeosalinity the range of salinity spans 14 95 we also show that a reliable quantitative continuous indicator of lacustrine palaeosalinity is important for the elucidation of continental palaeoenvironments for palaeoclimatology and archaeology and ocean continent climatic correlations and interactions

cosmogenic nuclide budgeting of floodplain sediment transfer abstract cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin a change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain we have modeled depth and time dependent cosmogenic nuclide concentration changes for 10 be 26 al and 14 c during sediment storage and mixing in various active floodplain settings ranging from confined shallow rivers with small floodplains to foreland basin scale floodplains traversed by deep rivers floodplain storage time estimated from channel migration rates ranges from 0 4 kyr for the beni river basin bolivia to 7 kyr for the amazon river basin while floodplain storage depth estimated from channel depth ranges from 1 to 25 m for all modeled active floodplain settings the long lived nuclides 10 be and 26 al show neither significant increase in nuclide concentration from irradiation nor decrease from decay we predict a hypothetical response time after which changes in 10 be or 26 al concentrations become analytically resolvable this interval ranges from 0 07 to 2 myr and exceeds in all cases the typical residence time of sediment in a floodplain due to the much shorter half life of 14 c nuclide concentrations modeled for the in situ produced variety of this nuclide are however sensitive to floodplain storage on residence times of the cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them is predicted to either increase or decrease in 10 be and 26 al concentration depending on the depositional depth these conditions can be evaluated using the 26 al 10 be ratio that readily discloses the depth and duration of storage we illustrate these models with examples from the amazon basin as predicted modern bedload collected from an amazon tributary the bolivian beni river shows no systematic change in nuclide concentration as sediment is moved through 500 km of floodplain by river meandering in contrast in the central amazon floodplain currently untouched by the modern river system low 26 al 10 be ratios account for minimum burial depths of 5 to 10 m for a duration of 5 myr the important result of this analysis is that in all likely cases of active floodplains cosmogenic 10 be and 26 al concentrations remain virtually unchanged over the interval sediment usually spends in the basin thus spatially averaged denudation rates of the sediment producing area can be inferred throughout the entire basin provided that nuclide production rates are scaled for the altitudes of the sediment producing area only because floodplain storage does not modify nuclide concentrations introduced from the sediment source area

magnesium content of non marine ostracod shells a new palaeosalinometer and palaeothermometer abstract ostracods are microcrustaceans with calcitic carapaces each consisting of two valves or shells that grow by moulting and regeneration of sequentially larger valves up to nine times before reaching maturity the mg content of these valves is species dependent and is a function of their growth stage and the temperature salinity mg content and mg ca ratio of their host water newly formed partly calcified valves of the non marine nektic ostracod mytilocypris henricae have high mg contents 100 000 ppm mg in caco3 at individual shell weights of 2 g this relative mg content decreases as calcification proceeds until shell weights exceed 120 g whereupon the mg content is constant and useful as an indicator of the ostracod s environment mg ca ratios in individual ostracod valves from several species of the genera mytilocypris and australocypris from culture experiments and a series of australian lakes indicate that the valve s mg content increases as a function of increasing temperature and salinity within the range 11 25 c and for waters containing 24 2325 ppm mg the molar mg ca ratio in these ostracods fully calcified valves increases by 0 0015 or 370 ppm mg in caco3 per 1 c and per change of 125 ppm mg in solution for most mainland australian lakes a change in water composition of 125 ppm mg corresponds to a change of 3 5 in salinity for a given mg content of a lake the mg ca ratio of the water may vary within the range of common lacustrine values without significantly affecting mg uptake in the ostracod valves these relationships can provide palaeosalinities and or palaeotemperatures for ostracods recovered from continental sediments for mg partitioning an increase in temperature and salinity produce increased mg content in ostracods whereas for 18o fractionation in biogenic calcite an increase in temperature produces a decrease in 18o of the ostracod and an increase in salinity leads to an increase in 18o of the ostracod thus a combination of 18o and mg measurements on non marine ostracods should enable unique resolution of palaeotemperature and palaeosalinity variations

geological and historical evidence of irregular recurrent earthquakes in japan great m 8 earthquakes repeatedly occur along the subduction zones around japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions assuming a simple characteristic earthquake model that similar earthquakes repeat at regular intervals probabilities of future earthquake occurrence have been calculated by a government committee however recent studies on past earthquakes including geological traces from giant m 9 earthquakes indicate a variety of size and recurrence interval of interplate earthquakes along the kuril trench off hokkaido limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years along the japan trench off northern honshu recurrence of giant earthquakes similar to the 2011 tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits along the sagami trough near tokyo two types of kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized but studies show that the recent three kanto earthquakes had different source extents along the nankai trough off western japan recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable such variability makes it difficult to apply a simple characteristic earthquake model for the long term forecast and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees

flow resistance and sediment transport by concentrated overland flow in a grassland valley abstract flow resistance and sediment transport data are needed from well vegetated humid environments to evaluate surface wash erosion and channel incision by overland flow in humid environments runoff in valley floors can reach depths of several centimetres but erosion is often limited by dense grass cover intense grazing reduces grass cover but the impacts of this on sediment transport processes are poorly understood we conducted flume experiments in a grassed valley of coastal california to investigate flow resistance and sediment yield under natural conditions and with progressive clipping of grass cover flow resistance has a laminar like relationship with reynolds number but we attribute this to very low velocity beneath submerged stems and not to the state of flow the sediment transport relations provide support for the concept of a threshold shear stress below which erosion is effectively prevented by surface resistance shear stress partitioning suggests that on a densely grassed surface over 90 of flow resistance is exerted on plant stems this effectively prevents sediment transport at boundary shear stresses as high as 1000 1800 dyn cm2 complete clipping of the grass cover reduces the critical shear stress for sediment transport to 11 38 of that under natural conditions continued surface wash erosion and channel initiation are prevented however by strong soil cohesion provided by a dense root mat even with reduction of root density boundary shear stresses of at least 250 430 dyn cm2 are required for channel incision

sediment residence time and connectivity in non equilibrium and transient geomorphic systems abstract growing empirical evidence shows that many geomorphic systems are in transient state or out of equilibrium with respect to the external driving forces the transient state is often related to the dis connectivity of the many constituent parts of geomorphic systems as a result of sediment storage along the sediment flow path from its source to the final sink the response time of geomorphic systems to external changes is thus dependent on the residence time of sediment in various storage compartments here i present a mathematical concept based on reservoir theory to model residence time of sediment using millennial scale sediment budgets the framework sheds light on the limitation of the sediment delivery ratio which is often used as a measure of sediment connectivity in geomorphic systems and provides analytical information on process type pace of sediment flux and connectivity of storage compartments along the sediment cascade the application of the reservoir theory to geomorphic systems under agricultural land use shows that sediment delivery ratios are linked to the virtual velocity of the eroded sediment the time since the onset of agricultural land use and the size of the studied basins with respect to the temporal evolution of sediment storages that temporarily remove sediment from the conveyor belt the framework aims to estimate the sediment residence time in storages which is linked to the effective time scale of disconnectivity reanalysis of a long term empirical sediment budget from central europe reveals that the response to agricultural land use which started 5000 years bp is mainly buffered by the long residence time of sediment on hillslopes in the order of 10 3 years which results in a delayed floodplain aggradation furthermore the framework was applied to paraglacial mountain systems that inherit striking evidences of pleistocene glacial erosion and still recover from the change from glacial to interglacial conditions as a consequence of the reduced lateral and longitudinal connectivity i show that paraglacial response times of sediment flux in mountain headwater in the canadian rocky mountains range in the order of 100 400 ka the results indicate that response times at the transition from glacial to interglacial conditions are much longer than the return interval of the major glaciations causing a transient behavior of mountain headwater basins during interglacial periods the presented reanalysis of millennial scale sediment budgets of agricultural and mountain geosystems provides an integrative framework to link paleo environmental reconstructions and the connectivity of transient geomorphic system to external changes

mega earthquakes rupture flat megathrusts the 2004 sumatra andaman and 2011 tohoku oki earthquakes highlighted gaps in our understanding of mega earthquake rupture processes and the factors controlling their global distribution a fast convergence rate and young buoyant lithosphere are not required to produce mega earthquakes we calculated the curvature along the major subduction zones of the world showing that mega earthquakes preferentially rupture flat low curvature interfaces a simplified analytic model demonstrates that heterogeneity in shear strength increases with curvature shear strength on flat megathrusts is more homogeneous and hence more likely to be exceeded simultaneously over large areas than on highly curved faults

dynamic rupture scenarios of anticipated nankai tonankai earthquakes southwest japan 1 we investigated dynamic rupture scenarios of anticipated megathrust earthquakes on the nankai tonankai subduction zone southwest japan to improve the scenario reliability the model parameters should be constrained by available data or derived from their analysis we employed the three dimensional plate interface geometry and the slip deficit rate on the interface accumulated slip deficit was used to obtain the stress drop distribution of anticipated earthquakes the estimated stress drop distribution is consistent with the seismogenic asperity locations known from the analysis of past earthquakes fault friction constitutive parameters however had to be assumed from indirect observations because they cannot be constrained directly by the data based on various geophysical observations we defined three regions where larger fracture energy is required these are the eastern edge of the tonankai area the western edge of the nankai area and the region between the tonankai and nankai areas beneath the kii peninsula such lateral heterogeneity promoted the segmented rupture along the nankai trough with predefined stress drop and constitutive parameters various rupture scenarios for tonankai and nankai asperities were obtained for different initiation locations in some cases a single segment is ruptured while in other cases all the segments are broken due to dynamic linkage at the segment boundary causing a giant earthquake the initiation location is a critical parameter that controls the rupture propagation across the segment boundary these scenarios will be extremely useful to evaluate deterministically the strong ground motions and tsunami hazards caused by the next major earthquakes in southwest japan

historical nankai suruga megathrust earthquakes recorded by tsunami and terrestrial mass movement deposits on the shirasuka coastal lowlands shizuoka prefecture japan geological investigations of coastal sediment sequences play a key role in verifying earthquake and tsunami characteristics inferred from historical records in this paper we present a multi proxy investigation of a coastal lowland site facing the nankai suruga megathrust and appraise evidence for tsunamis and earthquake triggered terrestrial mass movements occurring over the last 800 years combining a high resolution chronology with x ray computed tomography and analyses of particle size diatoms pollen non pollen palynomorphs and aerial photographs we present the most compelling geological evidence of the 1361 ce koan also known as shohei tsunami reported to date from any site along the megathrust this finding is consistent with either of two recent hypotheses a single larger rupture of both the nankai and tnankai regions or two smaller ruptures separated by a few days enhancing the site chronology using bayesian age modelling we verify evidence for inundation during the 1498 ce mei tsunami while previous investigations identified evidence for historically recorded tsunamis in 1605 1707 and 1854 ce and a storm surge in 1680 or 1699 ce we encountered a thick sand layer rather than discrete extreme wave deposits in this interval the overprinting of evidence highlights the potential for geological records to underestimate the frequency of these events a terrestrial mass movement also deposited a sand layer at the site radionuclide dating and aerial photographs provide independent confirmation that this may have been triggered by intense shaking in 1944 ce during the most recent great nankai suruga megathrust earthquake

rapid fluvial incision along the yellow river during headward basin integration the onset of fluvial erosion in an area of tectonic uplift is thought to reflect the timing of the uplift geomorphological data from the yellow river in tibet indicate that the rapid incision of this river channel occurred as a result of climate change at least six million years after the onset of plateau uplift

drainage basin responses to climate change recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion the sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution the golem model simulates basin evolution under the action of weathering processes hillslope transport and fluvial bedrock erosion and sediment transport results from perturbation analyses reveal that the nature and timescale of basin response depends on the direction of change an increase in runoff intensity or a decrease in vegetation cover will lead to a rapid expansion of the channel network with the resulting increase in sediment supply initially generating aggradation along the main network followed by downcutting as the sediment supply tapers off by contrast a decrease in runoff intensity or an increase in the erosion threshold will lead to a retraction of the active channel network and a much more gradual geomorphic response cyclic changes in runoff intensity are shown to produce aggradational degradational cycles that resemble those observed in the field cyclic variations in runoff also lead to highly punctuated denudation rates with denudation concentrated during periods of increasing runoff intensity and or decreasing vegetation cover the sediment yield from threshold dominated basins may therefore exhibit significant variability in response to relatively subtle environmental changes a finding which underscores the need for caution in interpreting modern sediment yield data

crustal earthquake triggering by pre historic great earthquakes on subduction zone thrusts triggering of earthquakes on upper plate faults during and shortly after recent great m 8 0 subduction thrust earthquakes raises concerns about earthquake triggering following cascadia subduction zone earthquakes of particular regard to cascadia was the previously noted but only qualitatively identified clustering of m 6 5 crustal earthquakes in the puget sound region between about 1200 900 cal years b p and the possibility that this was triggered by a great cascadia thrust subduction thrust earthquake and therefore portends future such clusters we confirm quantitatively the extraordinary nature of the puget sound region crustal earthquake clustering between 1200 900 cal years b p at least over the last 16 000 we conclude that this cluster was not triggered by the penultimate and possibly full margin great cascadia subduction thrust earthquake however we also show that the paleoseismic record for cascadia is consistent with conclusions of our companion study of the global modern record outside cascadia that m 8 6 subduction thrust events have a high probability of triggering at least one or more m 6 5 crustal earthquakes

tsunami hazards along the eastern australian coast from potential earthquakes results from numerical simulations australia is surrounded by the pacific ocean and the indian ocean and thus may suffer from tsunamis due to its proximity to the subduction earthquakes around the boundary of australian plate potential tsunami risks along the eastern coast where more and more people currently live are numerically investigated through a scenario based method to provide an estimation of the tsunami hazard in this region we have chosen and calculated the tsunami waves generated at the new hebrides trench and the puysegur trench and we further investigated the relevant tsunami hazards along the eastern coast and their sensitivities to various sea floor frictions and earthquake parameters i e the strike the dip and the slip angles and the earthquake magnitude rupture length the results indicate that the puysegur trench possesses a seismic threat causing wave amplitudes over 1 5 m along the coast of tasmania victoria and new south wales and even reaching over 2 6 m at the regions close to sydney maria island and gabo island for a certain worse case while the cities along the coast of queensland are potentially less vulnerable than those on the southeastern australian coast

the 2011 tohoku oki tsunami three years on abstract the 2011 tohoku oki tsunami that devastated the pacific coast of tohoku japan was a turning point for modern research as a result of this event it was recognized that paleotsunami research is vital to help understand the size and recurrence interval of low frequency large tsunamis this paper reviews the progress of geological research on the 2011 tohoku oki tsunami and summarizes new questions that are arising out of this work for example recent work suggests that the landward extent and thickness of the sandy deposit as well as the presence or absence of marine microfossils in the sediment are most likely to be mainly controlled by the initial wave properties sediment source offshore bathymetry and onshore topography this in turn implies that there are certain relationships between the characteristics of a tsunami deposit and the wave properties and it may be possible to reconstruct the latter from the deposits offshore tsunami deposits related to the 2011 tohoku oki tsunami have also been well described this recent research indicates that sedimentation and erosion in inner bay and open ocean 20 m water depth locations can be in the order of several meters suggesting that the tsunami shear force was strong in the nearshore zone on the other hand sandy to muddy deposits a few centimeters thick were observed at about 100 to 6000 m water depth it is likely that the tsunami resulted in resuspension of sea bottom sediments and that suspended material flowed downslope as a turbidity current or suspended flow although many authors recognize the possibility that strong earthquake groundshaking might have also generated turbidity currents studies of the 2011 tohoku oki event have led researchers back to two of the fundamental issues of tsunami geology understanding the linkage between onshore and offshore sedimentation and erosion and establishing identification criteria for tsunami deposits moreover though beyond the issue of simple tsunami geology it is important for all researchers to communicate with governments and the general public in order to reduce future casualties by using risk assessments based on our understanding of infrequent large tsunamis

changes in sediment yield of the yellow river basin of china during the holocene this research reconstructs the changes in sediment yield of the yellow river based mainly on a large number of 14 c dates collected from the literature the total volume of sediment yield of the basin during the holocene is estimated to be 8 0 x 10 12 tons the annual sediment yield had an increasing trend over the holocene from 0 68 0 72 0 79 to 1 0 1 x 10 9 tons over each 2500 year period from the early holocene to the present the changes in sediment yield are ascribed to both natural and anthropogenic reasons in which the latter became important in the late holocene the mean rate of increase in natural sediment yield throughout the holocene is estimated to be about 0 027 x 10 6 ton year and the natural annual sediment yield is projected to be 0 95 x 10 9 tons at the present the increasing trend of natural sediment yield is reasoned to be the consequence of evolution of landforms enhanced by tectonic movement and climatic change in the loess plateau the principal sediment source of the river towards a condition favorable to soil erosion comparing the estimated annual natural sediment yield with the current annual sediment load of 1 6 x 10 9 tons of the river it is clear that human activities have augmented natural soil erosion by about 41 in the yellow river basin furthermore an estimate of the overall pattern of anthropogenic sediment yield shows an accelerated increasing trend which is approximately correspondent with that of population in the loess plateau area c 2002 elsevier science b v all rights reserved

origin and evolution of a splay fault in the nankai accretionary wedge subduction zones are often characterized by wedge shaped sedimentary complexes called accretionary prisms that form when sediments are scraped off the subducting plate and added to the overriding plate large landward dipping thrust faults can cut through such a prism these faults known as megasplay faults 1 2 originate near the top of the subducting plate and terminate at the shallow landward edge of the prism1 3 4 5 6 megasplay faults have been the subject of numerous geological and geophysical studies4 5 6 7 8 9 10 11 12 13 14 15 but their initiation and evolution through time remains poorly constrained here we combine seismic reflection data from the nankai accretionary wedge with geological data collected by the integrated ocean drilling program iodp and find that the splay fault cutting this wedge initiated approx1 95 million years myr ago in the lower part of the prism as an out of sequence thrust oost after an initial phase of high activity the movement along the fault slowed down but uplift and reactivation of the fault resumed about 1 55 myr ago the alternating periods of high and low activity along the splay fault that we document hint at episodic changes in the mechanical stability of accretionary prisms

rates and spatial variations of soil erosion in europe a study based on erosion plot data an extensive database of short to medium term erosion rates as measured on erosion plots in europe under natural rainfall was compiled from the literature statistical analysis confirmed the dominant influence of land use and cover on soil erosion rates sheet and rill erosion rates are highest on bare soil vineyards show the second highest soil losses followed by other arable lands spring crops orchards and winter crops a land with a permanent vegetation cover shrubs grassland and forest is characterised by soil losses which are generally more than an order of magnitude lower than those on arable land disturbance of permanent vegetation by fire leads to momentarily higher erosion rates but rates are still lower than those measured on arable land we also noticed important regional differences in erosion rates erosion rates are generally much lower in the mediterranean as compared to other areas in europe this is mainly attributed to the high soil stoniness in the mediterranean measured erosion rates on arable and bare land were related to topography slope steepness and length and soil texture while this was not the case for plots with a permanent land cover we attribute this to a fundamental difference in runoff generation and sediment transfer according to land cover types on the basis of these results we calculated mean sheet and rill erosion rates for the european area covered by the corine database estimated rill and interrill erosion rates are ca 1 2 t ha 1 year for the whole corine area and ca 3 6 t ha 1 year 1 for arable land these estimates are much lower than some earlier estimates which were based on the erroneous extrapolation of small datasets high erosion rates occur in areas dominated by vineyards the hilly loess areas in west and central europe and the agricultural areas located in the piedmont areas of the major european mountain ranges c 2010 elsevier b v all rights reserved

modeling of long period ground motions in the nankai subduction zone model simulation using the accretionary prism derived from oceanfloor local s wave velocity structures the accretionary prism in the subduction zone which consists of thick low velocity oceanic sediments significantly affects the propagation of seismic waves for shallow offshore earthquakes including large interplate earthquakes in order to simulate long period 5 s ground motions in the nankai subduction zone we constructed a three dimensional 3d seismic velocity structure model of the accretionary prism by interpolation extrapolation of local s wave velocity structures beneath 46 oceanfloor seismic stations donet which are deployed just above the accretionary prism off the southern kii and eastern shikoku regions we modeled local s wave velocity structures using a simple two parameter depth varying velocity function to investigate the effects of the accretionary prism on ground and seafloor motions we conducted numerical simulations of seismic wave propagation for three local earthquakes that occurred in southwestern japan the simulations reasonably reproduced the observed seismograms not only for the period ranges of the moment tensor inversion 50 s but also for the strong long period ground motions in the sedimentary basins 5 s especially in the region where donet stations are densely deployed since depth varying local s wave structures significantly improve the reproducibility of long period ground motions our modeling procedure is useful for modeling long period ground motions of local and regional offshore subduction zone earthquakes

synthesizing sea surface height change including seismic waves and tsunami using a dynamic rupture scenario of anticipated nankai trough earthquakes abstract the development of offshore observation technology will provide researchers with tsunami records from within an earthquake focal area but this will create new problems because seismic waves coexist with tsunami inside a focal area the seismic waves could act as noise for the tsunami signal this study shows an efficient method to calculate sea surface height change caused by an earthquake including both seismic waves and tsunami simulation results indicate that seismic waves overlap with tsunami both affect the change in sea surface height although most previous tsunami studies have neglected the contribution of seismic waves we also numerically simulated the sea surface displacement wavefield and hypothesized results for an anticipated rupture scenario of a huge earthquake that may possibly occur in the nankai trough japan the synthesized record could be used to evaluate the performance of a real time tsunami prediction method additionally we discussed the similarity and difference between two kinds of tsunami waveforms the displacement of the sea surface and the pressure change at the sea bottom although seismic waves appeared in both waveforms the contribution of seismic waves was lower in the displacement at the sea surface than in the pressure change at the sea bottom

sediment yield in africa abstract several studies have compiled and analysed measured contemporary catchment sediment yield sy t km 2 y 1 values for various regions of the world although this has significantly contributed to our understanding of sy africa remains severely underrepresented in these studies the objective of this article is therefore 1 to review and compile available sy data for africa 2 to explore the spatial variability of these sy data and 3 to examine which environmental factors explain this spatial variability a literature review resulted in a dataset of sy measurements for 682 african catchments from 84 publications and reports representing more than 8340 catchment years of observations these catchments span eight orders of magnitude in size and are relatively well spread across the continent a description of this dataset and comparison with other sy datasets in terms of spatial and temporal distribution and measurement quality is provided sy values vary between 0 2 and 15 699 t km 2 y 1 median 160 t km 2 y 1 average 634 t km 2 y 1 the highest sy values occur in the atlas region with sy values frequently exceeding 1000 t km 2 y 1 also the rift region is generally characterised by relatively high sy values while rivers in western and central africa have generally low sy values spatial variation in sy at the continental scale is mainly explained by differences in seismic activity topography vegetation cover and annual runoff depth other factors such as lithology catchment area or reservoir impacts showed less clear correlations the results of these analyses are discussed and compared with findings from other studies based on our results we propose a simple regression model to simulate sy in africa although this model has a relatively low predictive accuracy 40 it simulates the overall patterns of the observed sy values well potential explanations for the unexplained variance are discussed and suggestions for further research that may contribute to a better understanding of sy in africa are made

overview of holocene tsunami deposits along the nankai suruga and sagami troughs southwest japan tsunami deposits provide a basis for reconstructing holocene histories of great earthquakes and tsunamis on the pacific coast of southwest japan the deposits have been found in the past 15 years at lakes lagoons outcrops and archaeological excavations the inferred tsunami histories span 3000 years for the nankai and suruga troughs and nearly 10 000 years for the sagami trough the inferred histories contain recurrence intervals of variable length the shortest of these 100 200 years for the nankai trough 150 300 years for the sagami trough resemble those known from written history of the past 1000 1500 years longer intervals inferred from the tsunami deposits probably reflect variability in rupture mode incompleteness of geologic records and insufficient research the region s tsunami history could be clarified by improving the geologic distinction between tsunami and storm dating the inferred tsunamis more accurately and precisely and using the deposits to help quantify the source areas and sizes of the parent earthquakes

shakedown in madagascar occurrence of lavakas erosional gullies associated with seismic activity erosion via lavaka formation is widespread in madagascar but controls on why and where lavakas occur are not understood geographic information system analysis reveals a spatial correlation between lavaka abundance and the frequency of seismic events most lavakas occur in or near areas where recorded earthquakes magnitude 0 5 5 6 are most frequent this correlation explains the unevenness of lavaka distribution in the malagasy highlands and highlights the importance of natural factors in lavaka formation seismic activity appears to precondition the landscape to lavaka formation although the mechanism by which this happens is not yet known recognizing the connection however allows us to pinpoint areas prone to future lavaka development in zones of active deforestation areas with the greatest frequency of seismic events are most at risk for high density lavaka development

imaging shear strength along subduction faults subduction faults accumulate stress during long periods of time and release this stress suddenly during earthquakes when it reaches a threshold this threshold the shear strength controls the occurrence and magnitude of earthquakes we consider a 3 d model to derive an analytical expression for how the shear strength depends on the fault geometry the convergence obliquity frictional properties and the stress field orientation we then use estimates of these different parameters in japan to infer the distribution of shear strength along a subduction fault we show that the 2011 mw9 0 tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength this observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength with increasing constraints on the different parameters at play our approach could in the future help identify favorable locations for large earthquakes

modern hydrology and late holocene history of lake karakul eastern pamirs tajikistan a reconnaissance study abstract lake karakul in the pamirs tajikistan is a deep brackish water lake in a closed basin at almost 4000 m above sea level water samples from the catchment area and lake karakul and a 104 cm sediment core from its shallow eastern sub basin were investigated and provide a first lake record from the region spanning the last 4200 cal yr bp multi proxy analyses revealed the following a relatively high meltwater inflow from glaciers snow fields and frozen ground in the catchment as a result of relatively warm conditions was reconstructed for the period between 4200 and 3500 cal yr bp the shift to colder climatic conditions around 3500 cal yr bp was probably abrupt total organic carbon values displayed the most dramatic drop for the entire core within less than 40 years in contrast the subsequent re establishment of warmer conditions occurred gradually over several centuries a higher meltwater supply to the lake and warmer conditions were recorded since ca 1900 cal yr bp with two slightly colder intervals between 1200 and 800 cal yr bp and between 400 and 100 cal yr bp the abrupt shift to significantly colder and drier conditions around 3500 cal yr bp in the eastern pamirs is seen also in records from the aral sea and the guliya ice core from the western tibetan plateau however more palaeoclimate studies in this highly continental part of central asia are needed to assess the spatial and temporal patterns of the holocene climate in the region

palaeoenvironmental indicators from late holocene and contemporary ostracoda of the aral sea abstract the aral sea is a large terminal lake i e having no outflow in south western asia it is diminishing in size and the salinity of the water is increasing due to excessive withdrawal of water for irrigation from the two main rivers flowing into it the biota of the lake has been decimated and the chemical composition changed dramatically since 1960 three short sediment profiles two cores and one section are examined with a view to reconstructing the most recent history of the sea from microfossil assemblages historical and geological records indicate that since its formation aral sea levels have changed such variation may have been accompanied by changes in the chemistry of the sea through increased evaporation or precipitation in the present work analyses of the mg ca and sr ca molar ratios particularly the latter of benthonic ostracoda from the aforementioned cores indicate that although present salinity levels were never attained during the period of deposition of the sections studied past saalinity variation can be inferred oxygen and carbon isotope analyses of ostracoda and mollusca from one of the sections however indicates two possible periods of relative salinity increase

monitoring of gully erosion on the loess plateau of china using a global positioning system abstract with the development of a technique global positioning system gps has become progressively less expensive lighter and easier to use the accuracy of gps has been improved and it appears applicable to the continuously monitoring morphology changes on the earth surface with small and slow change the objective of this study is to use gps to measure the morphology of gullies in a small catchment near suide shaanxi province china there are three main gully types in the study area bank gullies floor gullies and hill slope gullies and this study mainly focuses on the hill slope gullies the hill slope gullies in the study area are mainly discontinuous and are developing rapidly the gully density in the study area is very large the retreat rate of hill slope gullies is 0 16 2 02 m year 1 the relationships between the upslope drainage area a and the critical slope gradient s for hill slope gullies is s 0 1839a 0 2385 the values of as2 range from 41 to 814 m2 for the hill slope gully headcuts and most of them fell into the range of 100 300 m2 both of these relationships are suggested as indexes for estimating the location of gully headcuts

the impact of humans on continental erosion and sedimentation rock uplift and erosional denudation of orogenic belts have long been the most impor tant geologic processes that serve to shape continental surfaces but the rate of geomor phic change resulting from these natural phe nomena has now been outstripped by human activities associated with agriculture con struction and mining although humans are now the most important geomorphic agent on the planet s surface natural and anthro pogenic processes serve to modify quite dif ferent parts of earth s landscape in order to better understand the impact of humans on continental erosion we have examined both long term and short term data on rates of sediment transfer in response to glacio fl u vial and anthropogenic processes phanerozoic rates of subaerial denuda tion inferred from preserved volumes of sedimentary rock require a mean conti nental erosion rate on the order of 16 m per million years m m y resulting in the accumulation of 5 gigatons of sediment per year gt yr erosion irregularly increased over the 542 m y span of phanerozoic time to a pliocene value of 53 m m y 16 gt yr current estimates of large river sediment loads are similar to this late neogene value and require net denudation of ice free land surfaces at a rate of 62 m m y 21 gt yr consideration of the variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confi ned to drainage headwaters 83 of the global river sediment fl ux is derived from the high est 10 of earth s surface subaerial erosion as a result of human activity primarily through agricultural practices has resulted in a sharp increase in net rates of continental denudation although less well constrained than estimates based on surviving rock volumes or current river loads available data suggest that present farmland denudation is proceeding at a rate of 600 m m y 75 gt yr and is largely confi ned to the lower elevations of earth s land surface primarily along passive continental margins 83 of cropland erosion occurs over the lower 65 of earth s surface the conspicuous disparity between natu ral sediment fl uxes suggested by data on rock volumes and river loads 21 gt yr and anthropogenic fl uxes inferred from measured and modeled cropland soil losses 75 gt yr is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately downslope from erod ing croplands over the history of human agriculture accumulation of postsettlement alluvium on higher order tributary channels and fl oodplains mean rate 12 600 m m y is the most important geomorphic process in terms of the erosion and deposition of sedi ment that is currently shaping the landscape of earth it far exceeds even the impact of pleistocene continental glaciers or the cur rent impact of alpine erosion by glacial and or fl uvial processes conversely available data suggest that since 1961 global cropland area has increased by 11 while the global population has approximately doubled the net effect of both changes is that per capita cropland area has decreased by 44 over this same time interval 1 per year this is 25 times the rate of soil area loss antici pated from human denudation of cropland surfaces in a context of per capita food pro duction soil loss through cropland erosion is largely insignifi cant when compared to the impact of population growth

the fluctuating aral sea a multidisciplinary based history of the last two thousand years abstract the aral sea an intracontinental saline lake in western central asia is of great interest because of its rapid shrinkage during the last 50 years which caused catastrophic environmental and socio economic consequences for the region and its population geoscientists established the existence of similar multiple fast and deep lake level fluctuations in the past however a comprehensive picture of these changes has been lacking in this paper we summarize published and new geomorphological sedimentological paleoenvironmental geoarcheological and historical data to reconstruct fluctuations in the aral during the last two thousand years two deep regressions are recognized in addition to the modern human induced regression the regressions occurred at ca 2 1 1 3 and 1 1 0 35 ka cal bp according to the sedimentary and faunal data and 2 1 1 45 and 1 0 0 85 0 45 ka cal bp according to the archeological and historical data the aral sea lake level dropped to ca 10 m a s l during the first regression and to ca 29 m a s l during the second one transgressions which separated these periods reached elevations of ca 52 m a s l and 54 m a s l respectively according to the current data the regressions lasted longer than the transgressions or were of equal duration reasons considered for past aral sea lake level changes include both natural and human related causes as the region features more than 2000 years of agricultural activity

fdm simulation of seismic waves ocean acoustic waves and tsunamis based on tsunami coupled equations of motion we have developed a new unified modeling technique for the total simulation of seismic waves ocean acoustic waves and tsunamis resulting from earthquakes based on a finite difference method simulation of the 3d equations of motion using the equilibrium between the pressure gradient and gravity in these equations tsunami propagation is naturally incorporated in the simulation based on the equations of motion the performance of the parallel computation for the newly developed tsunami coupled equations using a domain partitioning procedure shows a high efficiency coefficient with a large number of cpu cores the simulation results show how the near field term associated with seismic waves produced by shallow earthquakes leads to a permanent coseismic deformation of the ground surface which gives rise to the initial tsunami on the sea surface propagation of the tsunami along the sea surface as a gravity wave and ocean acoustic waves in seawater with high frequency multiple p wave reflections between the free surface and sea bottom are also clearly demonstrated by the present simulations we find a good agreement in the tsunami waveform between our results and those obtained by other simulations based on an analytical model and the navier stokes equations demonstrating the effectiveness of the tsunami coupling simulation model based on this simulation we show that the ratio of the amplitude of ocean acoustic waves to the height of the tsunami both of which are produced by the earthquake strongly depends on the rise time of the earthquake rupture this ratio can be used to obtain a more detailed understanding of the source rupture processes of subduction zone earthquakes and for implementing an improved tsunami alert system for slow tsunami earthquakes

ostracod shell chemistry as proxy for paleoenvironmental change abstract the application of ostracod shell chemistry as a paleoenvironmental tool has grown within the past decades most studies have investigated mg and sr in ostracod shells as proxies for temperature and salinity and the use of a wide range of trace elements as prospective paleoenvironmental indicators has yet to be developed for lacustrine systems only a few preliminary studies have used trace metals in paleolimnological studies such as cd ba and zn as paleonutrient indicators or mn fe and u as redox and oxygenation indicators this paper reviews the state of the art of geochemical analyses in microfossils such as ostracods foraminifera and corals and provides insights in new trace element proxies with the goal to promote the use of trace elements in ostracod shells as paleoenvironmental proxies in paleoceanography foraminifera and corals are most prominently used to reconstruct past climate conditions well established proxies such as 18o mg ca and sr ca provide information about changes in sea surface temperatures in addition a great number of new proxies have been developed recently such as radiogenic isotopes and redox sensitive trace elements in paleolimnology ostracod shell chemistry is widely used to assess paleohydrological changes reconstruction of temperature and salinity changes in lake environments is often achieved by oxygen isotopes as well as mg ca and sr ca ratios but depending on the hydrological and geological settings of the lake system local calibrations are needed to assess which proxy is suited to reflect which processes new proxies need to be tested by novel techniques that recently have become available compared to conventional instrumentation used in ostracod shell chemistry methods such as laser ablation icp ms and nanosims allow single shell analysis and provide high resolution data the potential of ostracods in paleolimnology is not yet fully assessed but can be developed by learning from paleoceanographic studies

a systematic review of geological evidence for holocene earthquakes and tsunamis along the nankai suruga trough japan the nankai suruga trough the subduction zone that lies immediately south of japan s densely populated southern coastline generates devastating great earthquakes magnitude 8 characterised by intense shaking crustal deformation and tsunami generation forecasting the hazards associated with future earthquakes along this 700 km long fault requires a comprehensive understanding of past fault behaviour while the region benefits from a long and detailed historical record palaeoseismology has the potential to provide a longer term perspective and additional crucial insights in this paper we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the nankai suruga trough incorporating literature originally published in both japanese and english and enhancing available results with new age modelling approaches we summarise and critically evaluate evidence from a wide variety of sources palaeoseismic evidence includes uplifted marine terraces and biota marine and lacustrine turbidites liquefaction features subsided marshes and tsunami deposits in coastal lakes and lowlands while 75 publications describe proposed evidence from 70 sites only a limited number provide compelling well dated evidence the best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period this spatiotemporal compilation suggests that the 1707 ce earthquake ruptured almost the full length of the subduction zone and that earthquakes in 1361 ce and 684 ce may have been predecessors of similar magnitude intervening earthquakes were of lesser magnitude highlighting the variability in rupture mode that characterises the nankai suruga trough intervals between ruptures of the same seismic segment range from 450 years during the historical period over longer timescales palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes at present there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in 1707 ce however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the nankai suruga trough alongside the lack of research designed to quantify the maximum magnitude of past earthquakes we emphasise issues over alternative hypotheses for proposed palaeoseismic evidence the paucity of robust chronological frameworks and insufficient appreciation of changing thresholds of evidence creation and preservation over time as key issues that must be addressed by future research

coseismic slip resolution along a plate boundary megathrust the nankai trough southwest japan geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 tonankai mw 8 1 and 1946 nankaido mw 8 3 earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust data used include 798 angle changes from triangulation surveys 328 leveling section differences and 5 coseismic tidal gage offsets many of the nominally coseismic triangulation data span 50 years nearly half the earthquake cycle and correction for interseismic deformation using post 1950 observations is applied microseismicity is used to define the configuration of the plate boundary interface and approximate it with a continuous multisegment fault model because the onshore geodetic data have very limited resolving power for offshore fault segments offshore coseismic slip was constrained by satake s 1993 estimation based on tsunami data the majority of the coseismic slip occurs between 15 and 25 km depth although resolution declines toward the trench axis it is sufficiently good to define two distinct high slip regions one off southeastern shikoku island 11 m maximum and the other offshore of kii peninsula 3 m maximum the slip magnitude off southeastern shikoku coupled with the plate convergence rate would imply an recurrence interval of about 270 years much longer than the average repeat time of 120 years for historical great earthquakes on the nankai trough however the maximum coseismic slip is sensitive to the assumed fault geometry and slippage on trough parallel splay faults could significantly decrease the maximum slip to about 6 m

rupture process of the 1944 tonankai earthquake ms 8 1 from the inversion of teleseismic and regional seismograms 1 we digitized teleseismic and regional records of the 1944 tonankai earthquake we used the multiple time window method to invert these records for the spatial and temporal distribution of slip and rake we assume a 220 140 km fault with a spacing of 20 20 km and a maximum rupture velocity of 2 5 km s the inversion resolved an asperity along the accretionary wedge and under the shima and atsumi peninsulas the rupture propagated from southwest to northeast and there was little slip near the hypocenter consistent with the absence of uplift in the overlying submarine forearc basin the peak slip is 2 3 m and the total seismic moment is 2 4 1028 dyn cm mw 8 2 we compared the predicted and observed vertical geodetic displacements and inferred that the limit of rupture is consistent with the change from subsidence to uplift west of the atsumi peninsula this suggested that the earthquake did not rupture the plate interface in the tokai gap we modeled the tsunami using sea bottom displacements generated from this slip model the tide gauge amplitudes and frequency content are consistent with those predicted resolution tests from inverting synthetic seismograms computed using a simplified slip model indicated that the combination of teleseismic and regional data sets best recovers the asperity locations and peak slips given similar station geometry and degrees of freedom an inversion of the synthetic regional data set indicates that slip artifacts can occur early in the rupture process due to many clipped records while the inversion of synthetic teleseismic data set had less resolution and recovered only 50 of the peak slip

difference in the maximum magnitude of interplate earthquakes off shikoku and in the hyuganada region southwest japan inferred from the temperature distribution obtained from numerical modeling the proposed hyuganada triangle abstract to clarify differences in the maximum magnitude of interplate earthquakes offshore of shikoku m 8 and in the western adjacent hyuganada region m 7 5 southwest japan where the oceanic philippine sea phs plate subducts beneath the continental amuria plate along the nankai trough we calculated the temperature distribution for the plate interface using a three dimensional thermal convection model we attribute the observed very low heat flow values less than approximately 45 mw m 2 in the southern part of the hyuganada region to the subduction of the kyushu palau ridge which is presumably older than the adjacent shikoku basin to the east trial and error methods suggest an age difference of about 20 myr between these two areas the heat flow calculated from the temperature distribution fits the observed heat flow in the hyuganada region well the results show that hyuganada earthquakes may take place in the newly proposed hyuganada triangle bounded by a southeastern isotherm of about 200 c on the plate interface a northwestern boundary between the upper surface of the subducting phs plate and the continental moho discontinuity a northern isotherm of about 350 c and a northeastern margin normal zone with a possible barrier or large friction parameter l interplate earthquakes in such a limited seismogenic zone may reach a maximum magnitude of m 7 5 our results also suggest that a seismic gap seaward of the hyuganada region may be caused by stable sliding arising from low temperature resulting in a deeper updip limit than that offshore of shikoku the seismic gap offshore southwest of southern kyushu along the ryukyu trench may result from the overlapping of two stable sliding regimes on the plate interface one with low temperature at shallower depths caused by the subduction of the old phs plate and the other a serpentinized mantle wedge at deeper depths

modeling earthquake sequences along the manila subduction zone effects of three dimensional fault geometry abstract to assess the potential of catastrophic megathrust earthquakes m w 8 along the manila trench the eastern boundary of the south china sea we incorporate a 3d non planar fault geometry in the framework of rate state friction to simulate earthquake rupture sequences along the fault segment between 15 n 19 n of northern luzon our simulation results demonstrate that the first order fault geometry heterogeneity the transitional segment possibly related to the subducting scarborough seamount chain connecting the steeper south segment and the flatter north segment controls earthquake rupture behaviors the strong along strike curvature at the transitional segment typically leads to partial ruptures of m w 8 3 and m w 7 8 along the southern and northern segments respectively the entire fault occasionally ruptures in m w 8 8 events when the cumulative stress in the transitional segment is sufficiently high to overcome the geometrical inhibition fault shear stress evolution represented by the s ratio is clearly modulated by the width of seismogenic zone w at a constant plate convergence rate a larger w indicates on average lower interseismic stress loading rate and longer rupture recurrence period and could slow down or sometimes stop ruptures that initiated from a narrower portion moreover the modeled interseismic slip rate before whole fault rupture events is comparable with the coupling state that was inferred from the interplate seismicity distribution suggesting the manila trench could potentially rupture in a m8 earthquake

identifying storm surge deposits in the muddy intertidal zone of ena bay central japan abstract storm surge and tsunamis deposits provide essential information for those tasked with mitigating the impacts of natural disasters on coastal lowlands in low and middle latitude regions and also along active margins however studying these deposits in coastal lowland strata is becoming increasingly difficult particularly in residential regions because of extensive anthropogenic disturbance researchers have therefore had to extend the scope of their work to include shallow marine deposits such as bay sediments and some have also worked on storm surge deposits related to recent storm events in this study we identified and examined sandy storm surge deposits of up to 14 cm thick that were deposited by 2017 typhoon lan lowest pressure of 915 hpa the largest storm in the past 60 years within the tidal flat sediments of ena bay in the southern coastal area of metropolitan tokyo central japan we compared these deposits with the tsunami deposits 10 50 cm thick found on the tidal flats of koajiro bay near ena bay that resulted from the kanto earthquake magnitude 8 these differences mean that the thickness of such deposits is a valid criterion for distinguishing between storm surge and tsunami deposits on tidal flats

the use of ostracods from marginal marine brackish waters as bioindicators of modern and quaternary environmental change abstract ostracoda microscopic aquatic crustacea from brackish waters have a great potential for ecological monitoring and palaeoenvironmental analyses in highly variable environments this has been proven in many articles during recent decades but their potential has yet to be fully developed or utilised the analysis of ostracod assemblage composition species distributions eco phenotypic variability and the analysis of stable isotopes and trace elements in ostracod shells provide valuable information on present and past water salinity temperature and chemistry hydrodynamic conditions substrate characteristics climate sea level variations oxygen and nutrient availability this article provides an overview on the application of ostracods from brackish waters for palaeoenvironmental reconstruction in the quaternary and for environmental studies in present day environments

microbiotic signatures of the anthropocene in marginal marine and freshwater palaeoenvironments the term anthropocene has been proposed to indicate a geological interval character ized by global anthropogenic environmental change this paper attempts to recognize a method by which the anthropocene can be defined micropalaeontologically in order to do this microfloras and microfaunas diatoms macrophytes dinoflagellate cysts foraminifera and ostracods from nearshore waters through to paralic and freshwater aquatic milieux are considered and biotic varia bility with an anthropogenic causation identified microbiotic change can be related to anthropo genically induced extinctions pollution related mutation environmentally influenced assemblage variability geochemistry of carapaces tests floral change related to lacustrine acidification faunal and floral correlation to industrial and agricultural signatures and introduction of exotic species via shipping the influence of humanity on a local scale can be recognized in assemblages as far back as 5000 years bp however widespread anthropogenic change took place in europe and america particularly in the nineteenth and twentieth centuries although in asia e g japan it cannot be observed prior to the twentieth century profound and global biotic change began in the mid twentieth century and if the anthropocene is to be defined in this way then the period 1940 1945 might encompass the biotic base of the interval

high precision slip distribution of the 1944 tonankai earthquake inferred from tsunami waveforms possible slip on a splay fault abstract inversion of tsunami waveforms is a well established technique for estimating the slip distributions of subduction zone earthquakes with some of the most detailed results having been obtained for earthquakes in the nankai trough sw japan the present study although it uses a method and tsunami waveform data set almost identical to previous study aims to improve on previous work by using a more precise specification of initial conditions for the calculation of tsunami green s functions specifically we incorporated four improvements in the present study 1 we used a realistic plate model based only on seismic survey results and assumed it to be the fault plane of the 1944 tonankai earthquake 2 the smallest subfaults consistent with the long wavelength approximation were used in the tsunami inversion analysis 3 we included the effect of horizontal displacement of the ocean bottom on tsunami generation and 4 we performed a checkerboard resolution test as obtained in previous studies a zone of high slip 2 0 m was resolved off the shima peninsula however the more precise calculation of tsunami green s functions has revealed additional detail that was not evident in previous studies which we demonstrate is resolvable and correlates with the position of known faults in the accretionary prism while there was little or no slip near the trench axis in the eastern part of the rupture zone there was up to 1 5 m of slip resolved within 30 km of the trough axis in the western part along the coast of the kii peninsula this troughward slip zone coincides with the position of a large splay fault mapped in multichannel reflection surveys furthermore it is also clear that the upper edge of the enshu fault off shima and atsumi peninsulas is consistent with the up dip limit of slip in the eastern part of our model we tested the possibility that slip occurred on the former splay fault instead of on the plate interface during the 1944 tonankai earthquake and find that slip on this splay fault is also consistent with the data although we cannot distinguish whether slip was dominant on the splay fault or on the plate interface we further suggest that the position of the enshu fault may be determined by the subduction of topographic highs and that such faults may have an important influence on the up dip rupture limit of the 1944 tonankai and potentially other subduction zone earthquakes

possible slip history scenarios for the hyuga nada region and bungo channel and their relationship with nankai earthquakes in southwest japan based on numerical simulations the nankai earthquakes are great interplate earthquakes with recurrence intervals of 100 200 years occurring along the nankai trough southwestern japan new geological evidences suggest that the rupture area of the 1707 earthquake one of the largest extended farther westward than previously thought and similar magnitude events may have recurrence intervals of several hundred years west of the nankai earthquake segments in the bungo channel region slow slip events sses have occurred with recurrence intervals of several years since 1980 farther westward no m 7 5 interplate earthquakes have occurred except for one in 1968 in the northern hyuga nada region near the bungo channel we numerically simulated the generation cycles of nankai earthquakes hyuga nada earthquakes and bungo channel sses to obtain possible slip histories in these regions particularly during 1707 1980 we showed that the nankai and hyuga nada earthquakes occur mostly independently with average recurrence intervals of 151 and 117 years respectively an sse patch slipped coseismically during both the nankai and hyuga nada earthquakes the rupture of the nankai earthquakes extended to the hyuga nada region every 500 600 years and was followed by quiescence of sses for more than 200 years subsequently sses occurred repeatedly every 8 years current observational findings are generally consistent with the characteristics obtained from our scenarios except regarding the recurrence intervals of hyuga nada earthquakes for which few observations are available further evidence of the slip history in these regions will be required to use information from such simulations to forecast future earthquakes

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

impacts of tides on tsunami propagation due to potential nankai trough earthquakes in the seto inland sea japan the impacts of tides on extreme tsunami propagation due to potential nankai trough earthquakes in the seto inland sea sis japan are investigated through numerical experiments tsunami experiments are conducted based on five scenarios that consider tides at four different phases such as flood high ebb and low tides the probes that were selected arbitrarily in the bungo and kii channels show less significant effects of tides on tsunami heights and the arrival times of the first waves than those that experience large tidal ranges in inner basins and bays of the sis for instance the maximum tsunami height and the arrival time at toyomaesi differ by more than 0 5 m and nearly 1 h respectively depending on the tidal phase the uncertainties defined in terms of calculated maximum tsunami heights due to tides illustrate that the calculated maximum tsunami heights in the inner sis with standing tides have much larger uncertainties than those of two channels with propagating tides particularly in harima nada the uncertainties due to the impacts of tides are greater than 50 of the tsunami heights without tidal interaction the results recommend simulate tsunamis together with tides in shallow water environments to reduce the uncertainties involved with tsunami modeling and predictions for tsunami hazards preparedness

the 3 d distribution of random velocity inhomogeneities in southwestern japan and the western part of the nankai subduction zone 1 seismic waves at high frequencies 1 hz show collapsed and broadened wave trains caused by multiple scattering in the lithosphere this study analyzed the envelopes of direct s waves in southwestern japan and on the western side of the nankai trough and estimated the spatial distribution of random inhomogeneities by assuming a von karman type power spectral density function psdf strongly inhomogeneous media have been mostly imaged at shallow depth 0 20 km depth in the onshore area of southwestern japan and their psdf is represented as p m 0 05m 3 7 km3 with m being the spatial wave number whereas most of the other area shows weak inhomogeneities of which psdf is p m 0 005m 4 5 km3 at hyuga nada in nankai trough there is an anomaly of inhomogeneity of which psdf is estimated as p m 0 01m 4 5 km3 this psdf has the similar spectral gradient with the weakly inhomogeneous media but has larger power spectral density than other offshore areas this anomalous region is broadly located in the subducted kyushu palau ridge which was identified by using velocity structures and bathymetry and it shows no clear correlation with the fault zones of large earthquakes in past decades these spatial correlations suggest that possible origins of inhomogeneities at hyuga nada are ancient volcanic activity in the oceanic plate or deformed structures due to the subduction of the kyushu palau ridge

the slip distribution of the 1946 nankai earthquake estimated from tsunami inversion using a new plate model abstract a new model for the shape of the philippine sea plate psp subducting beneath southwest japan was constructed by combining marine seismic survey results and seismicity data this resulted in a plate model that is generally 3 5 km shallower than previous estimates and contains new details of plate boundary structure near the nankai trough axis we estimated the slip distribution of the 1946 nankai earthquake by inverting tsunami waveforms using the new plate boundary model and found that the large slip off cape muroto and seismic moment were reduced by about 10 from the previous estimate of tanioka and satake 2001a however we also found reason to suspect the tide gauge closest to the epicenter at shimotsu and this resulted in a much more substantial reduction in the amount of slip in the eastern segment of the rupture area we also find that our new rupture model correlates well with features of the subducting plate boundary such as a large subducting seamount off cape muroto kodaira et al 2000a this suggests that such features have an important effect on either earthquake rupture propagation or the interseismic accumulation of elastic strain energy or both

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

detailed coseismic slip distribution of the 1944 tonankai earthquake estimated from tsunami waveforms coseismic slip distribution on the fault plane of the 1944 tonankai earthquake is estimated from inversion of tsunami waveforms three improvements from a previous study satake 1993 are made these are 1 smaller subfaults are used to resolve detailed slip distribution 2 the sub faults fit better to the plate interface geometry and 3 finer and more accurate bathymetry data is used the inversion result shows that a maximum slip of about 3 m occurred on the plate interface off shima peninsula the total seismic moment is estimated to be 2 0 1021 nm mw 8 2 the result confirms that the 1944 tonankai earthquake did not rupture the plate interface beneath the tokai region and supports the existence of the seismic gap in the tokai region suggested by ishibashi 1981 the slip of about 1 5 m on the plate interface beneath atsumi peninsula northeast of the large slip area is necessary to explain the observed tsunami waveforms although no seismic moment release was estimated from strong motion data by kikuchi et al 1999 this may suggest that the rupture beneath atsumi peninsula was slow

evaluating the role of climate and tectonics during non steady incision of the yellow river evidence from a 1 24 ma terrace record near lanzhou china abstract the competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain most of recent studies have attributed terrace formation to climatic changes and held that even in tectonically active settings climate variations control cycles of terrace planation and abandonment based on field investigations of loess paleosol sequences magnetostratigraphy and optically stimulated luminescence osl dating we develop a new chronology for a spectacular flight of terraces along the yellow river near lanzhou china over past 1 24 ma all the terraces are strikingly similar in that they have several meters of paleosol developed directly above fluvial deposits on the terrace treads suggesting that the abandonment of each terrace due to river incision occurs during the transition from glacial to interglacial climates however the ages of terraces cluster in two relatively short time periods 1 24 0 86 ma and 0 13 ma present during the intervening time between 0 86 ma and 0 13 ma terraces either did not form or were not preserved we suggest that this record indicates that rock uplift rates varied through time and influenced terrace formation preservation thus our results demonstrate the utility of deep chronologic records from fluvial terraces for deconvolving the effects of tectonics and climate on fluvial incision

interplate coupling distribution along the nankai trough in southwest japan estimated from the block motion model based on onshore gnss and seafloor gnss a observations