the organic and mineral matter contents in deposits infilling floodplain basins holocene alluviation record from the klodnica and osobloga river valleys southern poland the work examines the timing and environmental conditions of floodplain sedimentation in the valleys of the upland klodnica and piedmont osobloga rivers in the upper odra river basin a distribution of 52 14c ages shows relatively high floodplain sedimentation at the late glacial holocene transition more stable floodplain environments since the early in the klodnica valley and middle holocene in the osobloga valley and a gradual increase in floodplain deposition in the late holocene since 3 4 kyr bp organic matter om and mineral matter mm fluctuations were correlated with variables responsible for the activation of erosion i e vegetation changes human impact and hydrological events as well as factors affecting the local record of sedimentation i e valley morphology hydrologic conditions and episodes of local erosion a clear relationship is shown between an increase in alluviation and climate or human induced extension of unforested areas the deposition of mineral rich sediments increases rapidly during periods characterized by non arboreal pollen values exceeding approximately 8 in pollen diagrams on the other hand the results obtained do not confirm significant interactions between holocene changes in forest composition and alluviation despite the settlement of agrarian groups the sedimentary record of human activity in the osobloga catchment is very poor during the neolithic and early bronze age a large scale alluviation of the osobloga and klodnica valleys was initiated during the settlement of people of the lusatian culture from the middle bronze age and escalated in the early middle ages and modern times the deposition of products of soil erosion was limited to between ca 1 9 1 2 kyr bp probably due to demographic regression during the migration period comparison of om mm fluctuations with phases of increased fluvial activity does not show a relationship between holocene wetter phases and catchment sediment yield sedimentary episodes in the upper odra basin also show a low degree of correlation with the probability density curve of the 14c ages the results obtained in the klodnica and osobloga valleys indicate a strong to moderate correlation between the spatial distribution of the study sites and the origin of mm rich deposits but a weak correlation between the spatial distribution of the study sites and toc content such a pattern suggests that om mm fluctuations relate predominantly to the changes in sediment yield although morphological conditions have a significant impact on the capture potential of sedimentary basins during phases of alluviation additionally high om content is not a simple function of an increase in wetness of the sedimentary environment on the other hand hydrologically conditioned hiatuses as well as erosion episodes impoverish the sedimentary record complicating the consideration on the geochronology of deposits and making it difficult to calculate reliable accumulation rates however they do not reduce the value of om mm fluctuations as an indicator of alluviation events for a preserved series of sediments

laboratory earthquakes the sub rayleigh to supershear rupture transition we report on the experimental observation of spontaneously nucleated supershear rupture and on the visualization of sub rayleigh to supershear rupture transitions in frictionally held interfaces the laboratory experiments mimic natural earthquakes the results suggest that under certain conditions supershear rupture propagation can be facilitated during large earthquake events

estimation of curie point temperature and geothermal structure of island arcs of japan abstract curie depth analysis from aeromagnetic data was performed in a nationwide project to assess the geothermal resources of japan creation of a curie depth map of japan was completed in 1984 and it agrees well with thermal structures such as the high temperature gradient regions of volcanic chains low temperature regions of the forearc basins and the intermediate temperature regions of the backarc basins measured temperature gradient t data were gathered in order to estimate the curie temperature from the t and the curie depths when t is assumed to be constant with respect to depth a remarkable difference is found in the estimated curie temperature t e c of the backarc and forearc side of the basins in the backarc side an average t e c of 450 c is reasonable for both the curie depth estimated from aeromagnetic data average depth of about 10 km in the backarc side and the temperature gradients average gradient of 4 5 c 100 m the average t e c on the forearc side was found to be low at about 300 c the difference in the curie temperatures between the two areas may be due to a regional difference in rock type e g granite as opposed to basalt in the case of the northeast japan arc as suggested by some authors the isotherms may suddenly fall between the volcanic front and the trench based on model studies we recognized that a curie depth map obtained by the algorithm we developed should include an averaging effect this suggests that the inferred curie depth curve across the line marking the sudden fall in the curie isotherm should gradually increase towards the trench therefore the low curie temperature that we estimated may indicate an apparent shallow curie depth caused by the averaging effect against an area bearing deep curie depths hence the reasons for the inconsistency of the estimated curie temperature between the forearc side and backarc side may be as follows 1 the averaging effect of the curie depth estimate which makes the curie depth apparently shallower in the forearc side and 2 the lower curie temperature of basaltic rocks which are assumed to be distributed along the east side of the aseismic front

bayesian analysis of radiocarbon chronologies examples from the european late glacial although there are many late glacial ca 15 000 11 000 cal yr bp proxy climate records from northwest europe some analysed at a very high temporal resolution decadal to century scale attempts to establish time stratigraphical correlations between sequences are constrained by problems of radiocarbon dating in an attempt to overcome some of these difficulties we have used a bayesian approach to the analysis of radiocarbon chronologies for two late glacial sites in the british isles and one in the adriatic sea the palaeoclimatic records from the three sites were then compared with that from the grip greenland ice core although there are some apparent differences in the timing of climatic events during the early part of the late glacial pre 14 000 cal yr bp the results suggest that regional climatic changes appear to have been broadly comparable between greenland the british isles and the adriatic during the major part of the late glacial i e between 14 000 and 11 000 cal yr bp the advantage of using the bayesian approach is that it provides a means of testing the reliability of late glacial radiocarbon chronologies that is independent of regional chronostratigraphical climatostratigraphical frameworks it also uses the full radiocarbon inventory available for each sequence and makes explicit any data selection applied potentially therefore it offers a more objective basis for comparing regional radiocarbon chronologies than the conventional approaches that have been used hitherto copyright 2004 john wiley sons ltd

a supershear transition mechanism for cracks seismic data indicate that fault ruptures follow complicated paths with variable velocity because of inhomogeneities in initial stress or fracture energy we report a phenomenon unique to three dimensional cracks locally stronger fault sections rather than slowing ruptures drive them forward at velocities exceeding the shear wave speed this supershear mechanism differentiates barrier and asperity models of fault heterogeneity which previously have been regarded as indistinguishable high strength barriers concentrate energy producing potentially destructive pulses of strong ground motion

three dimensional dynamic simulation of the 1992 landers earthquake the 1992 landers california earthquake magnitude 7 3 was modeled as the propagation of a spontaneous rupture controlled by a realistic prestress distribution with the use of a three dimensional finite difference method the dynamic rupture reproduces the general slip pattern used to compute the initial stress distribution and generates near fault ground motions at the surface similar to observations the simulated rupture propagates on the fault along a complex path with highly variable speed and rise time changing the magnitude and pattern of the stress significantly the method provides the framework to estimate earthquake rupture parameters from recorded seismic and geodetic data

log boats wooden structures peat and palaeochannels the challenges and opportunities afforded by decadal monitoring of an active quarry a case study from shardlow quarry middle trent valley uk abstract the river trent uk is renowned for a rich palimpsest of alluvial archaeological remains buried within the holocene sands and gravels of the valley floor since the late 1990 s extraction of these postglacial deposits at shardlow quarry in the middle reach of the valley close to the confluence of the river trent and river derwent has been investigated and monitored on a weekly basis by a project team including geoarchaeologists such monitoring of large exposures of floodplain sand and gravel and adjacent pleistocene terrace deposits initially by volunteer activity but latterly funded by the aggregate company under a formal planning agreement has revealed significant alluvial archaeological remains including two logboats a possible brushwood platform several fish weirs and organic rich palaeochannel deposits this paper provides a summary of the wealth of this resource but also reflects on the challenges of undertaking geoarchaeological studies in complex alluvial environments over such an extended time period it concludes by providing advice for best practice that could be applied to other long term studies within similar environments

changing hillslope and fluvial holocene sediment dynamics in a belgian loess catchment floodplain deposition is an essential part of the holocene sediment dynamics of many catchments and a thorough dating control of these floodplain deposits is therefore essential to understand the driving forces of these sediment dynamics in this paper we date floodplain and colluvial deposition in the belgian dijle catchment using accelerator mass spectrometric radiocarbon and optical stimulated luminescence dating relative mass accumulation curves for the holocene were constructed for three colluvial sites and 12 alluvial sites a database was constructed of all available radiocarbon ages of the catchment and this database was analysed using relative sediment mass accumulation rates and cumulative probability functions of ages and site specific sedimen tation curves cumulative probability functions of ages were split into different depositional environments representing stable phases and phases of accelerated clastic deposition the results indicate that there is an important variation between the different dated sites after an initial stable early and middle holocene phase with mainly peat growth in the floodplains clastic sedimentation rates increased from 4000 bc on this first phase was more pronounced and started somewhat earlier for colluvial deposits then for alluvial deposits the main part of the holocene deposits both in colluvial and alluvial valleys was deposited during the last 1 ka the sedimentation pattern of the individual dated sites and the catchment wide pattern indicate that land use changes are responsible for the main variations in the holocene sediment dynamics of this catchment while the field data do not provide indications for a climatological influence on the sediment dynamics copyright 2011 john wiley sons ltd

fluvial development and the sediment regime of the lower calder ribble catchment northwest england in the lower reaches of the calder lancashire tributary of the ribble catchment northwest england five river terraces set into the surrounding glacial terrain have been mapped and their underlying sediments radiocarbon dated the earliest terrace t1 reflects sandur style deposition during deglaciation and it aggraded in a reach cut into glacial diamict and glaciolacustrine muds incision below t1 spanned the start of the holocene driven by a combination of reduced sediment supply under a stabilising landscape and lower base levels t2 had aggraded and was being abandoned by 4000 bc its formation latterly involving a period of comparative stability in terms of channel migration perhaps a function of extensive forest cover and sea levels reaching above present day levels the last 3000 years were marked by substantial changes in the sedimentary regime with increased and varying sediment supply driving cycles of cut and fill and greater lateral channel migration these changes coincided with the first widespread and substantial reductions in forest cover and a progression towards an agricultural landscape between the aggradation of terraces t3 and t4 there was a substantial increase in sediment supply which is broadly in keeping with the erosion history in the surrounding uplands this sediment slug appears to have induced a switch from highly sinuous meandering to lower sinuosity channels characterised by lateral scroll style migration late holocene vegetation changes particularly woodland removal driven by anthropogenic land pressure appear to have rendered the floodplain prone to channel migration and the landscape more susceptible to erosion

rheological controls on fault loading rates in northern california following the 1906 san francisco earthquake 1 to estimate seismic hazard in complex multiple fault systems it is necessary to understand how stresses within the system are transferred accurate estimates of loading rate due to far field tectonic motion and postseismic transients following large earthquakes are required using plausible lower crustal rheologies constrained by observations following the 1906 san francisco earthquake i show that postseismic relaxation may play a significant role in reloading the coseismic fault providing 60 80 of the stress released during great earthquakes further postseismic stressing rates along neighboring faults are highly dependent on the geometry and rheology of the lower crust upper mantle this implies that tectonic loading rate estimates are also highly dependent on lower crustal upper mantle structure thus improvement of seismic hazard estimates within complex multiple fault systems is dependent on a better understanding of structure and rheology at depth

tomography of the 1995 kobe earthquake area comparison of finite frequency and ray approaches summary we determined a detailed 3 d crustal model in the 1995 kobe earthquake m 7 2 area in southwest japan using both finite frequency and ray tomography methods our finite frequency tomography technique is based on the single scattering theory the finite frequency sensitivity kernel derived in this study reflects correctly the sensitivity of the heterogeneity off the geometrical ray path and the existence of fresnel volume and the kernel depends on the dominant frequency of the observed wave the dominant frequency is estimated directly from the earthquake magnitude based on a relation that is obtained by regressively analyzing the displacement spectra of 20 earthquakes in the study area we used 141 118 p wave and 133 648 s wave high quality arrival time data from 2813 kobe aftershocks and 3140 other local earthquakes during 1995 2010 the tomographic images obtained with the finite frequency and ray tomography methods show a high level of similarity which is verified quantitatively by adopting the structural similarity index our results show that the kobe main shock hypocentre is located in a distinctive zone characterized by a high poisson s ratio and a low product vp vs of p and s wave velocities which is interpreted as a fluid filled fractured rock matrix that may have triggered the 1995 kobe earthquake

magnetotelluric imaging of the median tectonic line in western shikoku southwest japan implications of the fault related low resistivity zone abstract we carried out a magnetotelluric mt survey along a profile crossing the median tectonic line mtl in western shikoku japan the mtl is a terrane boundary that formed during the cretaceous between the sanbagawa belt consisting of high pressure temperature p t metamorphic rocks and the ryoke belt of granites and low p t metamorphic rocks the mt image shows a zone of remarkably low resistivity dipping northward at 40 at the surface coincides with the surface trace of the mtl the low resistivity zone probably corresponds to a fluid filled damaged zone of porous media composed of clay minerals and cracked rocks formed by repeated faulting of the mtl since late cretaceous time the calculated maximum porosity of the damaged zone is 7 1 which is clearly higher than that of the non damaged crystalline rocks

full interseismic locking of the nankai and japan west kurile subduction zones an analysis of uniform elastic strain accumulation in japan constrained by permanent gps we analyze permanent global positioning system gps data obtained over japan between 1995 and 1997 to estimate the instantaneous interseismic coupling ratio of the seismogenic zones due to the subduction of the pacific and philippine sea plates below the japanese islands we first derive the gps strain rate fields that characterize the crustal deformation of southern and northern japan and invert them to determine the effective subduction velocity along the central nankai trough on one side and the japan west kurile trench on the other these reference free velocities are close to those predicted by plate motion models with respect to eurasia we conclude that the eurasian reference frame gives a good approximation to the subduction motion and that to first order both subduction zones were fully locked during the period of measurements we then test whether the coupling ratio shows local variations within the seismogenic zones to do this we divide the subduction interface into 35 km 30 km elements that we model by point source groups and we invert the gps velocity field referenced to eurasia to derive the coupling ratio between 0 and 1 on each fault element the results are coherent over the 3 years and confirm that both the central nankai and the japan west kurile seismogenic zones are homogeneously fully locked most of the coupling ratios are close to 1 and a few are close to 0 intermediate values are rare the zones of decoupling correspond either to strong postseismic afterslip associated with the 1994 sanriku oki interplate earthquake japan trench or to a small overestimation of the actual lower limit of the locked zone we conclude that within the resolution of the gps data and the model 1 partial coupling did not exist during these 3 years along the nankai and japan west kurile trenches 2 the small seismic coupling ratio previously derived from earthquakes analysis for the japan and kurile trenches may indicate that a significant part of the elastic energy is dissipated silently through slow earthquakes and postseismic afterslip and 3 the heterogeneous coseismic slip pattern observed for the large and great earthquakes that rupture both subduction zones is in great contrast to the homogeneous loading finally we discuss the nonelastic residual deformation within the frame of the long term deformation of the japanese islands

low frequency earthquakes and tomography in western japan insight into fluid and magmatic activity abstract low frequency lf microearthquakes are detected in the lower crust and uppermost mantle beneath western japan which may reflect fluid and magmatic activity in the subduction zone in this work we combine seismic tomography and the lf earthquakes to study the crustal and upper mantle structure and fluid and magmatic activity in western japan high resolution tomographic images under this region are determined using high quality arrival time data in kyushu the subducting philippine sea slab is detected clearly as a high velocity zone and the arc magma related low velocity low v anomalies under the active arc and back arc volcanoes are imaged clearly prominent low v zones are visible in the crust and uppermost mantle beneath the quaternary volcanoes along the japan sea coast and lf events occur actively under some of those volcanoes lf events are also detected in the source areas of the 1995 kobe earthquake m 7 2 and the 2000 tottori earthquake m 7 3 supporting the hypothesis that the large crustal earthquakes were triggered by the crustal fluids these results indicate that fluid and magmatic activities exist widely in western japan which are caused by dehydration of the subducting philippine sea slab and corner flow in the mantle wedge

configuration of subducting philippine sea plate beneath southwest japan revealed from receiver function analysis based on the multivariate autoregressive model 1 we construct a detailed image of velocity discontinuity beneath southwest japan by using receiver functions we first propose an improved receiver function estimation method based on the statistical multivariate autoregressive model then we apply the new method to the teleseismic waveform data recorded by the high density seismograph network in southwest japan the results show a clear velocity discontinuity at 30 km depth beneath the southern shikoku region this discontinuity corresponding to the boundary between the oceanic crust and the high velocity layer the oceanic moho of the philippine sea plate phs continues down to the north indicating that the aseismic phs extends to the central chugoku region the continental moho is also clearly imaged beneath the chugoku region the depth contour of the phs shows a rather complicated feature with ridges and valleys the most significant ridge is located around longitude 133 e west of which the contours are basically directed north south changing to west east to the east beneath the western part of this ridge hypocenters of microearthquakes are located above this velocity discontinuity while earthquakes mainly occur below the discontinuity within the oceanic mantle beneath the eastern part of the ridge

the 1995 kobe earthquake seismic image of the source zone and its implications for the rupture nucleation in order to understand what may have triggered the 1995 kobe japan earthquake and how the rupture proceeded after initiation we determined high resolution three dimensional 3 d p and s wave velocity and poisson s ratio structures in the kobe epicentral area and relocated the aftershocks with the obtained 3 d velocity model we used 64 337 p and 49 200 s wave high quality arrival times from 3634 kobe aftershocks and local microearthquakes recorded by both permanent seismic networks and portable stations that were set up following the kobe mainshock significant velocity variations of up to 6 are revealed in the aftershock area we found that areas with high aftershock activity are generally associated with low poisson s ratio which may be the strong and competent parts of the fault zone and were apt to generate aftershocks the kobe mainshock hypocenter is located in a distinctive zone characterized by low p and s wave velocities and a high poisson s ratio this anomaly exists in the depth range of 16 to 21 km and extends 15 to 20 km laterally this anomaly may be due to a fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake our interpretation has been supported by many pieces of evidence from hydrological geochemical seismological and geophysical investigations conducted at the kobe earthquake region

bayesian modelling the retreat of the irish sea ice stream we present an 8000 year history spanning 650km of ice margin retreat for the largest marine terminating ice stream draining the former british irish ice sheet bayesian modelling of the geochronological data shows the isis expanded 34 0 25 3ka accelerating into the celtic sea to reach maximum limits 25 3 24 5ka before a collapse with rapid marginal retreat to the northern irish sea basin isb this retreat was rapid and driven by climatic warming sea level rise mega tidal amplitudes and reactivation of meridional circulation in the north atlantic the retreat though rapid is uneven with the stepped retreat pattern possibly a function of the passage of the ice stream between normal and adverse ice bed gradients and changing ice stream geometry initially wide calving margins and adverse slopes encouraged rapid retreat 550m a 1 that slowed 100m a 1 at the topographic constriction and bathymetric high between southern ireland and wales before rates increased 200m a 1 across adverse bed slopes and wider and deeper basin configuration in the northern isb these data point to the importance of the ice bed slope and lateral extent in predicting the longer term 1000 a patterns and rates of ice marginal retreat during phases of rapid collapse which has implications for the modelling of projected rapid retreat of present day ice streams copyright 2013 john wiley sons ltd

dating of post glacial landforms in the central howgills little is known of holocene landform development in upland britain this paper describes a site at middle langdale in the howgill fells of cumbria where large but now stabilized and inactive gullies cut through periglacial material at the base of the gullies large debris cones have buried earlier alluvial sediments on the valley floor on these sediments and buried by the debris cones is a well developed organic soil from which two 14c dates have been obtained in an attempt to estimate the age range of the soil these dates range from 2580 55 years bp for the fine particulate fraction from the base of the organic horizon to 940 95 years bp for fossil rootlets from the uppermost organic layer immediately below the overlying debris cones the pollen evidence suggests that the valley floor site was initially dominated by alder carr and later by a juncus marsh with birch alder and hazel nearby the pollen from the surrounding upland area suggests woodland on the valley sides dominated by oak and elm that was later replaced by a more open environment rich in heath species and in which disturbed ground species were present the magnetic evidence indicates a stable local environment during soil formation but shows a sudden inwash of unweathered debris at the top of the buried soil the evidence suggests that the valley floor was geomorphologically stable throughout the period of soil formation although there was a local change in valley floor vegetation and a reduction of woodland cover on the valley sides at sometime during the period the evidence then points to major geomorphological changes a wave of soil erosion gully development and debris cone deposition perhaps following the scandinavian introduction of sheep farming in the tenth century a d

robust chronologies for landform development obtaining chronological control for geomorphological sequences can be problematic due to the fragmentary and non sequential nature of sediment and landform archives the robust analysis of 14c ages is often critical for the interpretation of these complicated sequences this paper demonstrates a robust methodology for the 14c dating of geomorphological sequences using a case study from the lower ribble valley northwest england the approach adopted incorporates using greater numbers of ages targeting plant macrofossils obtaining replicate measurements from single horizons to assess the extent of reworking and the use of bayesian approaches to test models of the relative order of events the extent of reworking of organic materials and space time dynamics of fluvial change means that it is critical that chronological control is sufficiently resourced with 14c measurements as a result bayesian approaches are increasingly important for the evaluation of large data sets assessing the conformability of relative order models informed by interpretation of the geomorphology can identify contexts or materials that are out of sequence and focuses attention on problem materials reworking and errors in interpretation outlier ages these relative order models provide a framework for the interrogation of sequences and a means for securing probability based age estimates for events that occur between dated contexts this approach has potential value in constraining the sequence of geomorphological development at scales that vary from individual sites to a catchment or region furthering understanding of forcing and change in geomorphological systems copyright 2008 john wiley sons ltd

morphological and sedimentary responses to ice mass interaction during the last deglaciation during decline of the last british irish ice sheet biis down wasting of ice meant that local sources played a larger role in regulating ice flow dynamics and driving the sediment and landform record at the last glacial maximum glaciers in north western england interacted with an irish sea ice stream isis occupying the eastern irish sea basin isb and advanced as a unified ice mass during a retreat constrained to 21 17 3 ka the sediment landform assemblages lain down reflect the progressive unzipping of the ice masses oscillations of the ice margin during retreat and then rapid wastage and disintegration evacuation of ice from the ribble valley and lancashire occurred first while the isis occupied the isb to the west creating ice dammed lakes deglaciation complete after 18 6 17 3 ka was rapid 50 25 m a 1 but slower than rates identified for the western isis 550 100 m a 1 the slower pace is interpreted as reflecting the lack of a calving margin and the decline of a terrestrial grounded glacier ice marginal oscillations during retreat were probably forced by ice sheet dynamics rather than climatic variation these data demonstrate that large grounded glaciers can display complex uncoupling and realignment during deglaciation with asynchronous behaviour between adjacent ice lobes generating complex landform records

seismic imaging of southwest japan using p and pmp data implications for arc magmatism and seismotectonics abstract to better understand the relationship between crustal heterogeneity and seismotectonics and arc magmatism we determined a detailed p wave velocity structure of the crust under a north south belt area in southwest japan by using the first arriving p waves and the reflected p waves from the moho discontinuity pmp from 60 crustal earthquakes recorded by 29 seismic stations our results revealed significant low velocity anomalies beneath the fault zone of the median tectonic line and the daisen volcano which suggest that daisen is potentially an active volcano in the lower crust we detected low velocity anomalies overlying the subducting philippine sea plate which may indicate the existence of fluids released by the slab dehydration the 1955 southern tokusima earthquake m 6 4 occurred between low and high high velocity zones the 2000 western tottori earthquake m 7 3 and other nearby strong earthquakes occurred around the daisen volcano which may be related to the upwelling magma and fluids

three dimensional tomography of the 1992 southern california earthquake sequence constraints on dynamic earthquake rupture tomographic inversion of p wave arrival times from aftershocks of 1992 southern california earthquakes is used to produce three dimensional images of subsurface velocity the preliminary 1992 data set augmented by the 1986 m 5 9 north palm springs sequence consists of 6458 high quality events recorded by the permanent regional network providing 76306 raypaths for inversion the target area consisted of a 104 x 104 x 32 km 3 volume divided into 52 x 52 x 10 rectilinear blocks significant velocity perturbations appear to correlate with rupture properties of recent major earthquakes preliminary results indicate that a low velocity anomaly separates the dynamic rupture of the m 6 5 big bear event from the m 7 4 landers main shock a similar low velocity region separates the m 6 1 joshua tree sequence from the landers rupture high velocity anomalies occur at or near nucleation sites of all four recent main shocks north palm springs joshua tree landersbig bear a high velocity anomaly is present along the san andreas fault between 5 and 12 km depth through san gorgonio pass this high velocity area may define an asperity where stress is concentrated and where future large earthquakes may begin

holocene alluvial fan and terrace formation in the bowland fells northwest england in the bowland fells lancashire northwest england in the headwater valleys of the hodder river system is a suite of holocene fluvial landforms debris cones and alluvial fans at tributary junctions and river terraces along the main valleys post date late pleistocene forms and pre date the modern valley floor alluvial forms eight 14c dates from wood samples incorporated within the terrace and fan deposits have allowed two main phases of holocene erosion to be identified with debris cone fan deposition taking place after c 5400 bp but before c 1900 bp and again at c 900 bp some of the fans and cones are complex with deposits attributable to both phases others are simple and attributable only to the later phase in the headwaters an upper terrace at c 5400 bp pre dates the cones and a lower terrace is contemporaneous with the first debris cone phase lower downvalley the youngest of three terraces date from c 5000 bp or earlier indicating that the sequence is less complex downstream

crustal tomography under the median tectonic line in southwest japan using p and pmp data abstract the median tectonic line mtl is the largest active fault system on the japan islands and underlies many densely populated areas to understand the seismotectonics and to reduce seismic hazard in the mtl region we determined a detailed 3 d crustal structure under the region using a large number of arrival times of the first p waves and moho reflected waves pmp results of detailed resolution tests show that the addition of pmp data can significantly improve the resolution of the lower crustal structure and the entire crustal structure can be imaged better than that by using p wave data alone the obtained tomographic images show that prominent low velocity low v anomalies are visible in the upper crust along the mtl in addition some low v anomalies are visible in the lower crust on either side of the mtl these low v anomalies can be the weaker sections of the seismogenic crust and can be imprint of the existence and migration of aqueous fluids released by the dehydration process of the subducting philippine sea plate under southwest japan

chronology and palaeoenvironmental reconstruction in the sub tidal zone a case study from hinkley point evidence from the severn estuary demonstrates that this region was exploited by mesolithic hunter gatherer fishers bell 2007 the potential for future archaeological discoveries bell 2007 webster 2007 273 bell and warren 2013 39 and the well preserved palaeoenvironmental evidence in the fine grained and organic sediments of the somerset avon and gwent levels hosfield et al 2007a 40 makes the area of importance for archaeological study small quantities of worked flint have been recovered from the foreshore around stolford porlock and minehead bay mullin et al 2009 canti et al 1995 implying human activity in the present intertidal zone which is further enhanced by the suggestion of possible deliberate burning of reed swamps jones et al 2005 similar to that postulated in the severn estuary brown 2005 timpany 2005 bell 2007 while considerable research has been carried out within terrestrial and intertidal contexts remarkably little archaeological work has been undertaken below the mean low water mark webster 2007 273 the bristol channel and severn estuary has seen considerable change in sea level since the last glacial maximum long et al 2002 philips and crips 2010 extending our knowledge beyond the intertidal zone is therefore of key importance for understanding the late palaeolithic and mesolithic palaeogeography of the region hosfield et al 2007b developments in the recovery of offshore holocene peat and sediment sequences now permit the production of multi proxy palaeoenvironmental datasets and landscape reconstructions from submerged sample sites this paper uses evidence from three cores recovered from submarine peat deposits at hinkley point bristol channel uk to explore the issues and challenges associated with producing radiocarbon chronologies from deeply submerged peat sequences within a marine environment we emphasise the importance of analysis of multiple sequences to construct robust chronologies for local hydrological change and landscape reconstruction edwards 2006 the need for local evidence is critical if we are to move beyond generalised and potentially misleading models of human environment interaction scaife 2011 because as this case study demonstrates complex processes and landscape variability might have been features of even highly localised palaeoenvironments

deep structure and seismogenesis of the north south seismic zone in southwest china 1 to understand the deep structure and seismogenesis in the north south seismic zone nssz in southwest china we collected a large number of p and s wave arrival time data from both local earthquakes and teleseismic events to invert simultaneously for the three dimensional p and s wave velocity vp vs structures in the crust and upper mantle the obtained vp and vs models are generally coherent with each other from the crust to the mantle transition zone the nssz is characterized by strong structural heterogeneities from the mountainous areas of southeastern tibet to the yangtze platform low vp and low vs anomalies are generally imaged in the upper crust under the sichuan basin showing good agreement with the surface geological features that the foreland basin contains primarily mesozoic and paleozoic sedimentary rocks with a thickness of several kilometers the deep part of the yangtze platform is characterized by a cratonic lithospheric body dipping southwestward down to 400 km depth beneath the southeastern margin of the tibetan plateau in sharp contrast to low velocity anomalies in the upper mantle beneath the songpan ganzi fold system and the northwest qiangtang block at depths of the lower crust and uppermost mantle a layer with low vp and low vs 1 2 is revealed under a region west of the yangtze platform which may reflect the ductile flow in the lower crust our results indicate that the seismotectonics in the nssz is affected significantly by the ductile flow in the lower crust and strong heterogeneities in the upper mantle under southwest china in addition to the dominant role of the india asia collision

geoarchaeological records in temperate european river valleys quantifying the resource assessing its potential and managing its future throughout the quaternary episodes of glaciation and associated low sea level have resulted in the connection of the terrestrial landmasses of britain and mainland europe the river systems that established themselves across these newly emergent land surfaces of the coastal plain would have created important migration corridors for both animals and humans a point corroborated by the affinity of palaeolithic remains across britain and europe technological developments within the last decade have allowed these now submerged valley floors and adjacent terrestrial landscapes associated with the last cold stage and early and middle parts of the current holocene interglacial to be explored and their archaeological legacies unravelled providing geoarchaeologists with an opportunity to contribute to major cultural debates however in order to maximize knowledge it is essential that geoarchaeologists working within river valleys across both britain and the european continent are addressing similar research questions by collecting data using comparable methodologies this paper reviews the approach taken in different regions and provides a baseline assessment to allow the development of a coherent european wide framework for alluvial geoarchaeology and geoprospection particularly with respect to the holocene record

supershear rupture of the 5 january 2013 craig alaska mw 7 5 earthquake supershear rupture in which a fracture s crack tip expansion velocity exceeds the elastic shear wave velocity has been extensively investigated theoretically and experimentally and previously inferred from seismic wave observations for six continental strike slip earthquakes we find extensive evidence of supershear rupture expansion of an oceanic interplate earthquake the 5 january 2013 mw 7 5 craig alaska earthquake this asymmetric bilateral strike slip rupture occurred on the queen charlotte fault offshore of southeastern alaska observations of first arriving sn and sg shear waves originating from positions on the fault closer than the hypocenter for several regional seismic stations with path calibrations provided by an empirical green s function approach indicate a supershear rupture process several waveform inversion and modeling techniques were further applied to determine the rupture velocity and space time distribution of slip using regional seismic and geodetic observations both theoretical and empirical green s functions were used in the analyses with all results being consistent with a rupture velocity of 5 5 to 6 km s exceeding the crustal and upper mantle s wave velocity and approaching the crustal p wave velocity supershear rupture occurred along 100 km of the northern portion of the rupture zone but not along the shorter southern rupture extension the direction in which supershear rupture developed may be related to the strong material contrast across the continental oceanic plate boundary as predicted theoretically and experimentally the shear and surface wave mach waves involve strongly enhanced ground motions at azimuths oblique to the rupture direction emphasizing the enhanced hazard posed by supershear rupture of large strike slip earthquakes

late holocene environmental change in the howgill fells northwest england abstract new data from chapel beck in the southwest howgill fells combined with existing data support the identification of three phases of extensive hillslope gullying after 2200 between 1250 700 and after 500 cal bp examination of cumulative probability density function cpdf plots of the distribution of calibrated radiocarbon dates confirms the identification of these phases there are differences in the spatial distribution of geomorphic activity between these phases with the c 2200 1800 cal bp episode limited to the western howgill fells in comparison the 1250 700 and post 500 cal bp episodes are more widespread cross region phenomena and affected the more remote central fells pollen and geochemical data reveal several phases of increased human activity in these uplands with small scale temporary clearances during the late bronze age early iron age and more substantial clearances during the late iron age and romano british times 2300 1500 cal bp and these were followed by woodland expansion and decline in human activity during both the mid to late iron age and the period after the roman withdrawal from britain after 1500 cal bp the final substantial woodland clearances occurred from c 1100 900 cal bp after which there has been little woodland recovery a range of pollen sites across the howgill fells indicate that there is spatial variability in the level of human activity and impact iron age romano british woodland clearances appear to have affected the west of the region more than the remote central valleys whereas the later 1100 900 cal bp woodland reduction affected the entire region this pattern is similar to that identified from the geomorphology and demonstrates the importance of pollen sites that record local palaeo vegetation information and the significance of using a series of sites to explore intra regional variability in the vegetation history we suggest that human activity is a critical factor in mediating the late holocene geomorphic record but climate and particularly individual storms are the trigger mechanism responsible for erosion and incision on hillslopes and within the wider fluvial system palaeoclimate data humification and plant macrofossil from peat deposits at archer moss identify shifts to wetter conditions c 3100 2700 2400 1700 1300 1100 and after 650 cal bp and probably reflect increases in summer wetness of these the 2400 1700 1300 1100 and post 650 cal bp wetter phases coincide with increased geomorphic activity and perhaps encouraged incision on hillslopes rendered more susceptible to erosion by the activities of people

late pleistocene holocene river dynamics at the trent soar confluence england uk although river confluences have received geomorphic attention in recent years it is difficult to upscale these studies so confluence dominated reaches are commonly presumed to be either 1 braided or 2 meandering and characterized by laterally migrating channels if the geomorphology of a confluence zone is to be considered over longer timescales changes in river style need to be taken into account this paper uses a combination of remote sensing techniques lidar gpr er borehole survey and chronometric dating to test this differentiation in the confluence zone of a medium sized mixed load temperate river system trent uk which on the basis of planform evidence appears to conform to the meandering model however the analysis of confluence sediment body stratigraphy demonstrates that the confluence does not correspond with a simple meander migration model and chronostratigraphic data suggests it has undergone two major transformations firstly from a high energy braid plain confluence in the lateglacial 25 13 k yrs cal bp to a lower energy braided confluence in the early to middle holocene early holocene 2 4 kyr bp which created a compound terrace second incision into this terrace creating a single channel confluence 2 4 0 5 kyr cal bp with a high sinuosity south bank tributary the river soar the confluence sediment body stratigraphy is characterized by a basal suite of late pleistocene gravels bisected by younger channel fills which grade into the intervening levee and overbank sediments the best explanation for the confluence sediment body stratigraphy encountered is that frequent switching soft avulsions sensu edmonds et al 2011 of the tributary are responsible for the downstream movement of the channel confluence at an average rate of approximately 0 5 m per year dissecting and reworking older braid plain sediments the late holocene evolution of the confluence can be seen as a variant of the incisional frequent channel reorganization avulsion model with sequential downstream migration of the reattachment point copyright 2012 john wiley sons ltd

supershear rupture on multiple faults for the mw 8 6 off northern sumatra indonesia earthquake of april 11 2012 1 we perform a back projection method to image the rupture propagation and short period energy release of the 2012 off northern sumatra earthquake mw8 6 using hi net data recorded in japan the results show a complex pattern of four conjugate faults over about 180 sec there is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks with lengths of 200 to 400 km rupture speeds for several of the fault segments were very high about 5 km s and exceed the local s wave velocity this is the first example of an oceanic earthquake with supershear rupture speed

tomographic p wave velocity images of the loma prieta earthquake asperity tomographic inversion is applied to delay times from local earthquakes to image 3 d velocity variations surrounding the main rupture of the 1989 loma prieta earthquake the 55 times 45 square km region is represented by blocks of 1 km per side laterally and by 8 layers of varying thickness to 18 km depth high quality p wave arrival times recorded on the usgs calnet array from 549 crustal earthquakes with depths of 0 to 25 km were used as sources preliminary results note several velocity variations 5 12 that correlate with specific characteristics of the 1989 rupture these include prominent high velocity anomalies near the mainshock hypocenter and prominent low velocity anomalies where the dip of the san andreas fault appears to change significantly the termination of prominent low velocity features existing primarily in the hanging wall to depths of 7 9 km correlates with the top of the rupture zone high velocity variations along the fault dominate where aftershock activity is high the high velocity anomaly located at depth along the fault is interpreted as imaging the asperity on which the loma prieta earthquake occurred

earthquake ruptures modulated by waves in damaged fault zones faults are usually surrounded by damaged zones of lower elastic moduli and seismic wave velocities than their host rocks if the interface between the damaged rocks and host rocks is sharp enough earthquakes happening inside the fault zone generate reflected waves and head waves which can interact with earthquake ruptures and modulate rupture properties such as rupture speed slip rate and rise time we find through 2 d dynamic rupture simulations the following 1 reflected waves can induce multiple slip pulses the rise time of the primary pulse is controlled by fault zone properties rather than by frictional properties 2 head waves can cause oscillations of rupture speed and in a certain range of fault zone widths a permanent transition to supershear rupture with speeds that would be unstable in homogeneous media 3 large attenuation smears the slip rate function and delays the initial acceleration of rupture speed but does not affect significantly the rise time or the period of rupture speed oscillations 4 fault zones cause a rotation of the background stress field and can induce plastic deformations on both extensional and compressional sides of the fault the plastic deformations are accumulated both inside and outside the fault zone which indicates a correlation between fault zone development and repeating ruptures spatially periodic patterns of plastic deformations are formed due to oscillating rupture speed which may leave a permanent signature in the geological record our results indicate that damaged fault zones with sharp boundaries promote multiple slip pulses and supershear ruptures

holocene environmental reconstruction of sediment source linkages at crummock water english lake district based on magnetic measurements to reconstruct lateglacial and holocene environmental changes in the british uplands two c 5 8 m long sediment cores from crummock water nw england together with several hundred soil samples from the crummock water catchment were studied using magnetic techniques optically stimulated luminescence osl dating using fine silt quartz and 14c dating of terrestrial plant macrofossils were used to establish a chronology for the lake sediments a good agreement between optical and 14c ages indicates first that the osl dating method can be used to date lake sediments in the british isles second that macrofossil based 14c dating can be used to avoid the problem of old carbon error associated with bulk sample 14c dating of lake sediments and third that the established chronology is robust the lake sediment magnetic properties indicate a series of changes in sediment composition during the holocene which correlate well with sediment lithology water content and weight loss on ignition the first change corresponds to the lateglacial postglacial climatic shift at around 11400 years ago the subsequent suite of changes corresponds to a probable regional onset of human activity at 2000 bc and particularly to the intensification of human activity at around ad 900 a comparison of the lake sediment magnetic properties and those of the catchment soils shows a clear linkage for the lateglacial period and for the period after ad 900 in contrast detailed magnetic measurements of the early through mid holocene sediments suggest that their magnetic properties are dominated by bacterial magnetosomes

from sedimentary records to sediment budgets multiple approaches to catchment sediment flux this paper reviews the traditional approach to sediment budget studies in geomorphology new approaches and more specifically the potential impact of new methodological advances each component of the budget is discussed including the spatial and volumetric estimations of erosion deposition and storage and the precision and accuracy of flux rate estimation examples are used from recent work in germany the netherlands and the uk and include the pedogenic approach to erosion estimation remote sensing lidar geophysics and sediment based dating techniques for flux rate estimation the precision and accuracy of catchment sediment flux estimates based upon sediment storage is not only dependant upon volumetric accuracy but also on the precision and accuracy of sediment dating in this area there has been a revolution with direct sediment dating techniques tl osl esr freeing budget studies from the constraints and biases of radiocarbon of particular importance is the use of cosmogenic nuclides for dating but which can also be used to derive long term erosion rates but only using a steady state assumption finally a tentative initial application of the sediment budget approach to pleistocene terrace staircase in unglaciated basins is discussed it is argued that only now do we have the techniques available to be able to produce accurate sediment budget estimations at spatial scales greater than that of zero order basins and over time periods greater than that covered by direct observations

interpreting alluvial archives sedimentological factors in the british holocene fluvial record abstract a holocene alluvial archive of 506 dated units for great britain is analysed in terms of the sedimentation styles involved the database is classified by sedimentation unit channel sediments palaeochannel fills floodplain surface sediments floodbasins and colluvial deposits and alluvial ensemble fans and cones upland gullies and streams braided systems and active inactive meandering and anastomosing systems floodplain palaeochannel and floodbasin sediments dominate the record mostly from meandering anastomosing systems different sediment units show varied potential for recording environmental change some are relatively poorly dated with respect to the volumes of material involved whilst many dates float in periods of depositional activity which lasted for extended time periods much dated activity is autogenic and of relatively little value in interpreting external environmental influence ensembles and units are similar in age patterns in some respects commonly they exhibit sets of short term peaks in sedimentation activity but differ in others floodbasins and to an extent braided systems feature in the earlier holocene whilst dated fan deposition is more evident in the late holocene there is a general bias towards sediment units of late holocene age which probably reflects preservation factors previous british holocene alluviation models are reviewed it is suggested that the majority of earlier models reflect partial views imposed by limited regional coverage and available dating

gently north dipping median tectonic line mtl revealed by recent seismic reflection studies southwest japan abstract the median tectonic line mtl with a length of more 1000 km is the most significant fault in japan it juxtaposes the high p t sambagawa metamorphic rocks against the low p t metamorphic rocks of the ryoke belt the mtl was probably formed in the cretaceous with many subsequent reactivations the western segment of the mtl is still active with an almost pure right lateral sense of motion although a great amount of geological information on the mtl has been accumulated information about the subsurface especially the deep seated structure of the mtl is still insufficient it has been generally assumed that the mtl is vertical or steeply dipping at depth because of its straight surface trace and its recent lateral motion recently new geophysical data have suggested that the mtl dips gently northward at depth we have acquired a complementary set of geophysical profiles seismic reflection and refraction gravity and mt across the mtl in east shikoku our results confirm that the mtl dips northward at about 30 to 40 degrees from the surface to about 5 km depth where it becomes listric this fault geometry more reasonably explains the reactivation history of the mtl the motion has occurred on a listric type fault in so called oblique or lateral ramp manner

fluvial sediments correlations and palaeoenvironmental reconstruction the development of robust radiocarbon chronologies abstract multiple sequences of radiocarbon dates extracted from organic materials are increasingly being used to provide robust chronologies for landscape development particularly the timing and correlation of significant climatic and process events whilst the validity of using such frameworks in sedimentary environments such as lake basins and raised bogs has been the focus of much attention such debates have not extended to fluvial systems using examples from three lowland vertically accreting river valleys in east anglia uk this paper assesses the robustness of their associated radiocarbon chronologies by assessing the contrasting age estimates that are obtained by dating different parts of the same organic sample humic humin and plant macrofossils at a variety of stratigraphic levels overall the humin and humic acid fraction results were statistically consistent whilst the plant macrofossil remains were found to be of a slightly younger age in these examples it is argued that the younger ages appear to be the result of phragmites common reed roots pushing plant macrossils through the sedimentary sequence or opening up voids for material to fall through although studies in lacustrine and mire environments suggest alternative explanations may also be possible whichever explanation is preferred this study demonstrates clearly that the complexity of valley floor stratigraphy and processes is such that using single radiocarbon dates whether ams or bulk samples to reconstruct chronologies of geomorphic system response may need to be refined and subjected to the same level of assessment that has been applied in other sedimentary systems

bayesian age modelling applied to palaeoflood geochronologies and the investigation of holocene flood magnitude and frequency a new methodology based on bayesian age modelling is presented for the analysis of palaeoflood geochronologies and palaeodischarge data bayesian age models were developed using the oxcal radiocarbon calibration software for the geochronologies of three palaeoflood sites in spain namely the gaudalentin tagus and llobregat rivers in se central and ne spain respectively the age depth plots resulting from the applied sequence models enabled the construction of flood magnitude frequency plots through substitution of the original stratigraphic depth data with the associated minimum discharge quantified by hydraulic modelling the age models presented demonstrate that a bayesian approach for analyzing holocene flood magnitude and frequency prevents the loss of geomorphic and hydrologic information inherent in radiocarbon frequency methods previously used in the analysis of palaeoflood data sets frequency approaches do not allow proper consideration of flood magnitude information and only incorporate t

state of stress before and after the 1994 northridge earthquake the state of tectonic stress in the epicentral area of the 17 january 1994 northridge earthquake mw 6 7 is investigated by applying a stress inversion method to p wave polarity data from earthquakes in northridge from july 1981 to january 1994 and from the northridge aftershocks during january 1994 to december 1995 a 3 d crustal model is used to trace the rays taking off from the hypocenter which reduced the effects of large structural heterogeneities on the determination of the stress tensor we found significant temporal changes of stress orientations induced by the northridge earthquake the principal pressure p axis is oriented n32 e from 1981 to june 1992 and n30 e from 28 june 1992 to 16 january 1994 suggesting that the stress field in northridge was not affected by the 1992 landers earthquake during two weeks following the northridge mainshock the p axis is oriented n13 e which is a significant 17 change from that before the earthquake n30 e between february 1994 and august 1995 the p axis orientation changes from n18 e to n26 e and finally ends up at n34 by the end of 1995 which is close to that before the northridge earthquake these results suggest that the stresses rotated coseismically then rotated more slowly back to their original orientation the aftershocks caused by the mainshock changed the stress distribution in the crust which showed up as a regional stress change the stress recovery appears to have completed within two years after the mainshock which is very short compared to the time scale of the earthquake cycle

sensitivity of floodplain geoecology to human impact a holocene perspective for the headwaters of the dijle catchment central belgium floodplain deposition rates have increased markedly under influence of human impact throughout the late holocene in many western and central european catchments consequently the geomorphology and ecology of many floodplains changed in this study we discuss this human impact and its influence on the floodplain geoecology during the middle and late holocene for the headwaters of the dijle catchment located in the belgian loess belt the floodplain geoecology and the regional vegetation was reconstructed from sedimentological and palynological analyses an age depth model for the studied sequences was obtained using 17 radiocarbon dates statistical analyses of the pollen data cluster analysis and canonical correspondence analysis were used to detect changes in the pollen record our data show that until c 2500 cal bp human impact was nearly absent or localized with no discernible influence on the floodplain geoecology the floodplain was in a stable phase and consisted of a marshy environment where organic material could accumulate which is interpreted as the natural state of the floodplain from c 2500 cal bp onwards human impact gradually increased however only when human impact in the catchment crossed a threshold around 500 cal bp the floodplain geoecology changed with clearing of the alder carr forest the establishment of a single channel river and the dominance of minerogenic overbank sedimentation spatial variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differences in hillslope floodplain connectivity and local differences in human impact

dynamic rupture models for the southern san andreas fault abstract dynamic rupture and resultant ground motions up to 0 25 hz are simulated for an m w 7 6 earthquake on the southern san andreas fault spontaneous rupture is modeled with slip weakening friction and 3d viscoelastic wave solutions are computed with a support operator numerical method the initial traction model is derived from inversions of the m w 7 3 1992 landers strong ground motion records and borrows heavily from that used for the terashake2 simulations by olsen et al 2008 heterogeneity in the traction model leads to focusing of the rupture front and the focusing produces cases of supershear rupture velocity in asperities areas of high initial traction as well as cases of high peak slip rate and cohesive zone contraction in antiasperities separate solutions are computed for version 3 0 and 4 0 respectively of the southern california earthquake center community velocity model scec cvm we also compare the case of a flat ground surface a common simplification made for finite difference simulations to the case of the ground surface conformed to regional topography the overall distribution of simulated ground motion intensity is consistent with that derived from the empirical model of campbell and bozorgnia 2008 in the sense that the bulk of simulated pseudospectral velocity psv values are within the 68 confidence intervals of the empirical model simulated psvs corresponding to low probability in the empirical model are principally associated with basin wave guide and directivity effects an important example first identified by the terashake1 simulations olsen et al 2006 is the stronger than expected ground motions at the site of montebello due to a basin wave guide effect we find that this effect is lessened for version 4 0 of the scec cvm relative to version 3 0 due to a shallower model for the chino basin

seismic velocity structure of the crust beneath the japan islands abstract more than 13 000 arrival times of 562 local shallow earthquakes selected from the japan university network earthquake catalog are used to investigate the seismic velocity structure of the crust beneath the japan islands we simultaneously determined the hypocenter parameters p and s wave station corrections and depth distributions of the conrad and moho discontinuities beneath the whole of the japan islands by applying an inversion method the p and s wave station corrections show similar distribution patterns they are negative relatively late arrivals of seismic waves in hokkaido and positive relatively early arrivals of seismic waves in western japan in eastern honshu they are positive along the coast of the pacific ocean and negative in the land area and along the coast of the japan sea the conrad discontinuity is located at a depth range from 12 to 22 km in hokkaido the conrad is shallow in the eastern pan and becomes deep toward the west in ne honshu the conrad is deep beneath the land area and becomes shallow toward the surrounding seas in western japan the conrad is shallow in the northern part and becomes deep toward the south the moho is located in a depth range from 25 to 40 km in hokkaido the moho has the shape of a circular cone with a maximum depth of 36 km in most parts of the japan islands the moho is deep beneath the land area and becomes shallow toward the surrounding seas the moho is deepest up to 40 km beneath the central part of the chubu district

river entrenchment and terrace formation in the uk holocene abstract a meta analysis of a large database of 14c dated fluvial units is used to assess the chronology and controls of episodic holocene river entrenchment and terrace formation in the uk most holocene terraces are of a fill cut type developed in pleistocene sediments in places now reaching down to pre holocene bedrock holocene terraces are widespread in higher relief areas of the uk and peripheral higher energy rivers and include up to 7 levels in some valley floor reaches using 14c constrained data sub sets for incision episodes the onset vertical ranges formation times and rates of entrenchment are examined together with geographical distributions the height range of terrace separation is relatively small 0 5 3 5 m with a long term averaged incision rate over the late and mid holocene of 0 43 0 5 0 67 0 7 and 0 81 m ka in the tweed rheidol severn ouse and ribble catchments and a regional similarity in the scale of incision events the periods 4200 3700 3100 2900 2100 1900 1800 1500 cal bp and most notably the last 1000 years with prominent peaks at 900 800 and 700 600 cal bp were times of accelerated incision it appears likely that extreme flood events triggered the formation of incision slots rather than entrenchment being a direct response to glacio tectonic uplift or the result of incremental valley floor lowering by combined incision and lateral reworking river entrenchment has also been rapid in recent centuries reflecting the coupling of extreme events with anthropogenic effects on catchment hydrology incision results in changes of river channel flood power and overbank flood extent and improved data on the long term and large scale vertical tendency of uk rivers are needed for flood risk management purposes

seismic imaging of the 1999 izmit turkey rupture inferred from the near fault recordings we use near fault accelerograms to infer the space time history of rupture on the fault during the izmit earthquake the records show that the ground displacement and velocity near the fault were surprisingly simple rupture propagated toward the west at a velocity of about 3 km s and toward the east at a remarkably high average velocity of 4 7 km s over a distance of about 45 km before decelerating to about 3 1 km s on the eastern segment slip on the fault is particularly large down to a depth of 20 km on the central portion of the fault where it reaches about 7 m slip is large also below 10 km on the eastern fault segment and this may have contributed to the loading of shear stress on the duzce fault on the western fault segment large slip seems confined to shallow depths

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records

coupling relationships hillslope fluvial linkages in the hodder catchment nw england abstract variations in the coupling of sediment transfer between different parts of a fluvial catchment e g hillslope to axial stream can hamper understanding but are an integral part of the geomorphological record depositional environments respond to a combination of land use climate storms floods and autogenic conditioning the distribution of sediment in the upland landscapes of nw england is out of equilibrium with contemporary climate and geomorphological processes more a function of peri and paraglacial mobilisation of glacigenic deposits soil and vegetation development after deglaciation have interrupted any progression toward sediment exhaustion with sediment release controlled largely by extrinsic perturbation with late holocene anthropogenic activity climate and extreme hydrological events the likely candidates this paper presents a new radiocarbon dated holocene geomorphological succession for the river hodder nw england alongside evaluating new palaeoecological and geoarchaeological data to discern the impacts of human activity these data show a late holocene expansion in human occupation and use of the landscape since the iron age 700 0 cal b c with more substantial changes in the character and intensity of upland land use in the last 1300 years the geomorphological responses in the uplands were the onset of considerable and widespread hillslope erosion gullying and associated alluvial fan development interpretation of the regional radiocarbon chronology limits gullying to four more extensive and aggressive phases after 500 cal b c the downstream alluvial system has responded with considerable valley floor deposition and lateral channel migration that augmented sediment supply by remobilising the existing floodplain terraces and led to the aggradation of a series of inset alluvial terraces the timing of these changes between states of aggradation and incision in alluvial reaches reflects the increased connectivity between the hillslope and alluvial systems aspects of both the regional climate and land use histories are conducive to increasing discharge and sediment flux but the region wide lowering of erosion thresholds appears a key driver conditioning these sediment rich conditions and producing a landscape that was more susceptible to erosion under lower magnitude flows

crack density and saturation rate in the 1995 kobe earthquake region we have estimated the 3 d distribution of crack density parameter and saturation rate in the 1995 kobe earthquake region by applying a crack theory to values of seismic velocity and poisson s ratio obtained from seismic tomography our results show that and exhibit considerable heterogeneity higher and exist in the kobe fault zone in particular at the mainshock hypocenter high areas are generally consistent with high areas but high areas have a much wider distribution indicating that microcracks exist in more localized areas while fluids are permeating through wider areas in the crust a significant discrepancy between and exists beneath osaka bay where is low while is high is generally high beneath seas but low beneath land areas osaka bay and the present sea land distribution in southwest japan have existed for 2 millions years this period is long enough for the sea water to permeate down to the deep crust through the active faults that would have been ruptured during many earthquakes cycles

evidence for the location and cause of large crustal earthquakes in japan large crustal earthquakes magnitude 5 7 8 0 depth 0 20 km during a period of 115 years from 1885 to 1999 in japan occurred in or around zones of low seismic velocity revealed by seismic tomography the low velocity zones may represent weak sections of the seismogenic crust the crustal weakening is considered to be closely related to the subduction of the oceanic pacific and philippine sea plates in this region along the volcanic front and in back arc areas the crustal weakening may be caused by active volcanoes and magma chambers in the forearc areas fluids are detected in the earthquake source zones which may have contributed to the crustal weakening and the rupture nucleation the fluids may be related to the dehydration of the subducting philippine sea slab these results indicate that large crustal earthquakes do not strike anywhere but only anomalous areas that may be detected with geophysical methods

scale model and numerical simulations of near fault seismic directivity foam rubber experiments simulating unilaterally propagating strike slip earthquakes provide a means to explore the sensitivity of near fault ground motions to rupture geometry subsurface accelerometers on the model fault plane show rupture propagation that approaches a limiting velocity close to the rayleigh velocity the slip velocity waveform at depth is cracklike slip duration of the order of narrower fault dimension w divided by s wave speed surface accelerometers record near fault ground motion enhanced along strike by rupture induced directivity most experimental features initiation time shape duration and absolute amplitude of acceleration pulses are successfully reproduced by a 3d spontaneous rupture numerical model of the experiments numerical and experimental model acceleration pulses show similar decay with distance away from the fault and fault normal components in both models show similar large amplitude growth with distance along fault strike this forward directivity effect is also evident in response spectra the fault normal spectral response peak at period w 3 increases approximately sixfold along strike on average in the experiments with similar increase about fivefold in the corresponding numerical simulation the experimental and numerical model response spectra agree with an empirical directivity model for natural earthquakes at long periods near w and both overpredict shorter period empirical directivity effects with the amount of overprediction increasing systematically with diminishing period we attribute this difference to rupture and wavefront incoherence in natural earthquakes due to fault zone heterogeneities in stress frictional resistance and elastic properties present in the earth but absent or minimal in the experimental and numerical models rupture front incoherence is an important component of source models for ground motion prediction but finding an effective kinematic parameterization may be challenging

relations among fault behavior subsurface geology and three dimensional velocity models the development of three dimensional p wave velocity models for the regions surrounding five large earthquakes in california has lead to the recognition of relations among fault behavior and the material properties of the rocks that contact the fault at seismogenic depths regions of high moment release appear to correlate with high seismic velocities whereas rupture initiation or termination may be associated with lower seismic velocities these relations point toward a physical understanding of why faults are divided into segments that can fail independently an understanding that could improve our ability to predict earthquakes and strong ground motion

reply to comment cumulative probability functions and their role in evaluating the chronology of geomorphological events during the holocene richard c chiverrell varyl r thorndycraft and thomas o hoffmann journal of quaternary science 26 76 85

supershear transition due to a free surface in 3 d simulations of spontaneous dynamic rupture on vertical strike slip faults supershear rupture propagation has been inferred from seismic observations for natural faults and observed in laboratory experiments we study the effect of the free surface on the transition of earthquake rupture from subshear to supershear speeds using simulations of spontaneous dynamic rupture on vertical strike slip faults we find that locally supershear rupture near the free surface can occur due to i the generalized burridge andrews mechanism that is a supershear loading field between p and sv wave arrivals generated by the main rupture front at depths and ii the phase conversion of sv to p diffracted waves at the free surface weaker supershear slip due to the generalized burridge andrews mechanism is caused by the low strength at shallow portions of the fault relative to deeper ones dominant supershear rupture is supported by the additional supershear loading field produced by phase conversion locally supershear propagation at the free surface occurs regardless of the level of prestress and can cause transition to supershear propagation over the entire seismogenic depth such global supershear transition which depends on prestress can occur under prestress levels lower than the theoretical estimates for models with no free surface although the effectiveness of supershear transition due to the free surface can be diminished by several potentially important factors it may play an important role on natural faults at least in those strike slip earthquakes that accumulate significant surface slip

hillslope gullying in the solway firth morecambe bay region great britain responses to human impact and or climatic deterioration abstract in the solway firth morecambe bay region of great britain there is evidence for heightened hillslope instability during the late holocene after 3000 cal bp little or no hillslope geomorphic activity has been identified occurring during the early holocene but there is abundant evidence for late holocene hillslope erosion gullying and associated alluvial fan and valley floor deposition interpretation of the regional radiocarbon chronology available from organic matter buried beneath alluvial fan units suggests much of this geomorphic activity can be attributed to four phases of more extensive gullying identified after 2500 2200 1300 1000 1000 800 and 500 cal bp both climate and human impact models can be evoked to explain the crossing of geomorphic thresholds and palaeoecological data on climatic change bog surface wetness and human impact pollen together with archaeological and documentary evidence of landscape history provide a context for addressing the causes of late holocene geomorphic instability high magnitude storm events are the primary agent responsible for gully incision but neither such events nor cooler wetter climatic episodes appear to have produced gully systems in the region before 3000 cal bp increased gullying after 2500 2200 cal bp coincides with population expansion during iron age and romano british times the widespread and extensive gullying after 1300 1000 cal bp and after 1000 800 cal bp coincides with periods of population expansion and a growing rural economy identified during norse times 9 10th centuries ad and during the medieval period 12 13th centuries ad these periods were separated by a downturn associated with the harrying of the north ad 1069 to 1070 the gullying episode after 500 cal bp also coincides with increased anthropogenic pressure on the uplands with population growth and agricultural expansion after ad 1500 following 150 years of malaise caused by livestock and human the black death plagues poor harvests and conflicts on the scottish english border the increased susceptibility to erosion of gullies is a response to increased anthropogenic pressure on upland hillslopes during the late holocene and the role of this pressure appears crucial in priming hillslopes before subsequent major storm events in particular the cycles of expansion and contraction in both population and agriculture appear to have affected the susceptibility of the upland landscape to erosion and the hillslope gullying record in the region therefore contributes to understanding of the timing and spatial pattern of human exploitation of the upland landscape

barrier induced supershear ruptures on a slip weakening fault here we investigate the effects of a patch with elevated effective normal stress barrier on two dimensional in plane supershear rupture propagation on a planar fault from numerical experiments our results confirm that the barrier may slow down or stop coseismic ruptures but may also induce supershear ruptures we demonstrate that the supershear rupture may emerge in a region that is delineated by two approximate linear boundaries if the barrier size is below the lower boundary ruptures can overcome the barrier and propagate at subshear speeds if the barrier size is larger than the upper boundary ruptures are always stopped by the barrier furthermore we find that the barrier induced supershear ruptures may eventually slow down into subshear speed depending on the size and the location of the barrier the duration of supershear ruptures increases as the barrier sizes grow from the lower to the upper boundary which are proportional to the reduction in rupture speeds caused by the barrier these results indicate that a barrier on the fault may not stop coseismic ruptures rather the barrier may induce ruptures propagating at supershear speeds that play important roles in near field ground shaking and damage

material contrast does not predict earthquake rupture propagation direction 1 earthquakes often occur on faults that juxtapose different rocks the result is rupture behavior that differs from that of an earthquake occurring on a fault in a homogeneous material previous 2d numerical simulations have studied simple cases of earthquake rupture propagation where there is a material contrast across a fault and have come to two different conclusions 1 earthquake rupture propagation direction can be predicted from the material contrast and 2 earthquake rupture propagation direction cannot be predicted from the material contrast in this paper we provide observational evidence from 70 years of earthquakes at parkfield ca and new 3d numerical simulations both the observations and the numerical simulations demonstrate that earthquake rupture propagation direction is unlikely to be predictable on the basis of a material contrast

effects of a low velocity zone on a dynamic rupture dynamic crack earthquake simulations generally assume that the crustal material surrounding faults is laterally homogeneous tomographic and near fault seismic studies indicate that the crust near faults is instead comprised of rocks of varying material velocities we have tested the effects of adding material velocity variation to simulations of spontaneously propagating earthquakes we used two dimensional plane strain conditions coupled with a slip weakening fracture criterion and examined earthquakes on faults that bisect finite width low velocity zones embedded in country rock and earthquakes on faults that bound two different velocity materials when a fault bisects a low velocity zone the normal stress remains unchanged but both the rupture velocity and slip velocity pulse shape are perturbed the presence of the low velocity zone induces high frequency oscillations in the slip function near the rupture front when the fault is on the edge of the low velocity zone the oscillations are more pronounced and repeated sticking and slipping can occur near the rupture front for the slip weakening velocity independent friction model however the temporary sticking does not lead to permanent arrest of slip and slip duration is still controlled by the overall rupture dimension when an earthquake ruptures a fault juxtaposing a lower velocity material against a higher velocity material the normal stress across the fault near the crack tip is perturbed the sign of the normal stress perturbation depends on the direction of rupture leading in some cases to a directional dependence of rupture velocity when slip is accompanied by stress reduction a positive feedback develops between the normal and shear stress changes as previously noted by andrews and ben zion 1997 resulting in an apparently unavoidable grid size dependence in computation of stress change near the rupture front numerical experiments indicate however that the rupture velocity is insensitive to this zone size dependence which is highly localized immediately behind the crack tip the factors controlling the rupture velocity in the simulations including directional dependence are further elucidated by a new analytical solution for rupture of an asperity on a frictionless interface

structural factors controlling the rupture process of a megathrust earthquake at the nankai trough seismogenic zone summary the nankai trough is a vigorous subduction zone where large earthquakes have been recorded with a recurrence time of 100 200 yr the 1946 nankaido earthquake is well known as an unusual event among these earthquakes because the rupture zone estimated from long period geodetic data is more than twice as large as that derived from seismic wave data in the summer of 1999 an onshore offshore deep seismic survey was performed along a 355 km long profile in the western nankai trough seismogenic zone seismic signals both from an airgun array 207 l and land explosions maximum of 500 kg were recorded simultaneously by 98 oceanbottom seismographs and 93 land seismic stations conventional 2 d seismic reflection data were also acquired along part of the offshore profile from the wide angle seismic data we found a subducting seamount at the centre of the proposed rupture zone with dimensions of 13 km thick by 50 km wide at 10 km depth the seismic velocity image also shows that the seamount is now colliding with the japanese island arc crust from this significant structure this paper proposes that the subducted seamount functioned as a barrier at least during the 1946 earthquake i e the rupture of the 1946 earthquake extended over the entire locked zone to the east of the subducted seamount and then the rupture was deflected around the subducted seamount at the down dip end of the locked zone between cape muroto and cape ashizuri another significant structure a highly reflective layer is obtained beneath shikoku island a very slow p wave velocity 3 km s 1 is necessary in a thin layer at the base of the island arc crust in order to explain the observed high amplitude reflection phases an area of low resistivity obtained by a previous magnetotelluric study corresponds to the highly reflective layer this suggests a possible water layer at the base of the island arc crust the water may be generated by dehydration of the downgoing probably partially serpentinized mantle which is implied by a low p wave velocity 7 5 km s 1 beneath the subducted seamount a locally observed non slip region during the 1946 earthquake at the eastern part of shikoku island is interpreted as a result of weak coupling at the possible water layer

tomography of the source area of the 1995 kobe earthquake evidence for fluids at the hypocenter seismic tomography revealed a low seismic velocity 5 and high poisson s ratio 6 anomaly covering about 300 square kilometers at the hypocenter of the 17 january 1995 magnitude 7 2 kobe earthquake in japan this anomaly may be due to an overpressurized fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake

segmentation and holocene surface faulting on the median tectonic line southwest japan the median tectonic line mtl active fault system is a 300 km long arc parallel right lateral strike slip fault related to oblique subduction of the philippine sea plate beneath the eurasian plate at the nankai trough southwest japan the fault on shikoku island has a slip rate of 5 10 mm yr one of the highest in onshore japan we identified 12 geometric segments along the mtl separated by discontinuities such as en echelon steps bends changes in strike and gaps in the surface trace a chronology of latest holocene surface faulting on the mtl was constructed based on previously published and new work including trenching geomorphic mapping and acoustic profiling and piston coring of the submarine extension of the fault zone the mtl probably does not rupture along its entire length in a single earthquake but instead consists of multiple earthquake segments that rupture independently of one another the recurrence interval and surficial offset for surface rupturing earthquakes at four individual sites on the mtl in shikoku island are 1000 3000 years and 5 8 m respectively the relatively long recurrence interval and large surficial offset per earthquake suggest large seismic moment release during surface rupturing earthquakes on the mtl as commonly observed for japanese moderate to large intraplate earthquakes because the predicted rupture lengths based on empirical relations between surface displacement and rupture length are considerably larger than those of individual segments large earthquakes on the mtl probably rupture multiple geometrically defined segments the fault was previously thought to be unruptured at least in the past 1000 years based on the absence of historical evidence for destructive earthquakes however trench excavations show that part of the mtl ruptured most recently during or after the 16th century a d with at least 6 9 0 7 m of slip along the main fault trace this rupture may be correlated to the 1596 keicho kinki earthquake but further geological and historical investigations are needed to confirm this hypothesis

sediment transmission and storage the implications for reconstructing landform development the late holocene last 3000 years development of the lower ribble valley northwest england displays evidence for a complex response to a sediment recharge event forced by land use change induced increases in erosion and sediment delivery the deposition of fluvial sediments during the late holocene was restricted to a series of reaches or depocenters separated by zones with no sediment accumulation constrained by older glacial and fluvial terrain apparent reach wide correlations of fluvial terraces break down under the scrutiny applied by comprehensive and extensive radiocarbon control bayesian testing of relative order models show that large scale geomorphological changes e g the progression from one terrace level to another were time transgressive between different depocenters the different histories of sediment delivery and storage are probably a function of local and process scale variations in these depocenters and reflect dis connectivity relationships within a reach in propagating a basin scale change superslug in the sediment regime disconnectivity in the depositional regime through a fluvial reach limits what we can reconstruct in terms of sediment budgets but radiocarbon dating of multiple palaeochannels offers considerable potential for landform based research to uncover rates of change within individual depocenters copyright 2009 john wiley sons ltd

crustal velocity field of southwest japan subduction and arc arc collision we investigate crustal deformation in southwest japan over a 3 year period revealed by a permanent dense global positioning system gps array southwest japan is a part of the amurian plate a microplate moving about 10 mm yr toward the east with respect to the eurasian plate it overrides the philippine sea plate at the nankai trough and collides with the northeast japan arc in the central part of japan in this paper we first derive gps site velocities relative to the stable part of the amurian plate in order to isolate signals of crustal deformation caused by the subduction and or the collision the velocity field has a conspicuous feature indicating the interseismic elastic loading by the philippine sea plate slab at the nankai trough characterized by the northwestward movements of points throughout the studied area their amplitudes are the largest at the pacific coast and decay toward the japan sea coast with a subtle systematic shift of azimuths a model assuming an elastic half space the convergence rate at the nankai trough based on a refined euler vector and the strength of the coupling inferred from a thermal model could explain the velocity field in the western part of the studied area to a large extent those in the eastern part systematically deviate from them and the residual components there show east west shortening and north south extension this may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and northeast japan this suggests that the collision between southwest and northeast japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block a velocity contrast was found across the median tectonic line the largest inland active fault in japan but the current permanent gps network is not dense enough for us to discuss its coupling depth

climate scale modelling of suspended sediment load in an alpine catchment debris flow rio cordon northeastern italy abstract pulsing storms and prolonged rainfall can drive hydrological damaging events in mountain regions with soil erosion and debris flow in river catchments the paper presents a parsimonious model for estimating climate forcing on sediment loads in an alpine catchment rio cordon northeastern italian alps hydroclimatic forcing was interpreted by the novel clismssl climate scale modelling of suspended sediment load model to estimate annual sediment loads we used annual data on suspended solid loads monitored at an experimental station from 1987 to 2001 and on monthly precipitation data the quality of sediment load data was critically examined and one outlying year was identified and removed from further analyses this outlier revealed that our model underestimates exceptionally high sediment loads in years characterized by a severe flood event for all other years the clismssl performed well with a determination coefficient r2 equal to 0 67 and a mean absolute error mae of 129 mg y 1 the calibrated model for the period 1986 2010 was used to reconstruct sediment loads in the river catchment for historical times when detailed precipitation records are not available for the period 1810 2010 the model results indicate that the past centuries have been characterized by large interannual to interdecadal fluctuations in the conditions affecting sediment loads this paper argues that climate induced erosion processes in alpine areas and their impact on environment should be given more attention in discussions about climate driven strategies future work should focus on delineating the extents of these findings e g at other catchments of the european alpine belt as well as investigating the dynamics for the formation of sediment loads

recurrence analysis of the mass movement activity at stambach austria based on radiocarbon dating abstract the stambach mass movement austria is a large and deep seated mass movement in the austrian alps it consists of a complex and compound mass movement system the latest major reactivation of the stambach mass movement was initiated in 1982 by rock fall activity that triggered an earth flow which transformed into a mud flow six sediment cores were taken along the entire earth flow body showing a complex mixture of rock fall blocks and earth flow material whenever the earth flow was active numerous wooden remains were buried within the flow mass thirteen of these remains sampled from the sediment cores were radiocarbon dated the results indicate that the first activation of the stambach mass movement occurred at least around 9750 9900 cal bp followed by at least three further events during the holocene around 6310 5650 2320 1880 and 1600 1180 cal bp accumulation of toppled rock towers in the head area of the earth flow followed by a sudden collapse and saturated undrained loading of the earth flow body is the main trigger for activating the earth flow these long lasting preparatory processes make it difficult to determine certain recurrence intervals however our data show that the stambach mass movement was and most probably still can be reactivated after more than 3000 years of dormancy

a faulting model for the 1979 imperial valley earthquake by comparing synthetic particle velocities with the near source strong motion data we have constructed by trial and error a faulting model for the 1979 imperial valley earthquake the calculation of the synthetic seismograms takes into account the vertical inhomogeneity of the elastic parameters in the imperial valley and the spatial variation of the slip rate parameters on the fault plane the independent slip rate parameters are 1 the strike slip rate amplitude 2 the dip slip rate amplitude 3 the duration that slip rate is nonzero the rise time of the slip function and 4 the rupture time which determines when the slip rate is initiated our faulting model has the following principal features 1 faulting occurred on the imperial fault and on the brawley fault rupture on the brawley fault being triggered by rupture on the imperial fault 2 the imperial fault is a plane 35 km long and 13 km wide with a strike of 323 measured clockwise from north and a dip of 80 ne the brawley fault is a 10 km long and 8 km wide plane with a strike of 360 and a dip of 90 3 faulting on the imperial fault is primarily right lateral strike slip with a small component of normal dip slip in the sediments at its northern end the larger strike slip rates are generally confined between depths of 5 and 13 km with maximum values of about 1 0 m s the duration varies on the fault with a maximum of 1 9 s which is considerably shorter than the total time for the rupture to take place 4 the rupture velocity on the imperial fault is highly variable locally it exceeds the shear wave velocity and in one instance the compressional wave velocity the average rupture velocity though is less than the shear wave velocity 5 although the slip on the brawley fault contributes only about 4 of the total moment it greatly affects the ground motion at nearby stations 6 the total seismic moment is 6 7 1018 n m where the imperial fault contributes 6 4 1018 n m and the brawley fault contributes 2 7 1017 n m in the process of trying almost 300 faulting models we found that given the elastic parameters of the medium the synthetic seismograms were most sensitive to the specification of the rupture time although the slip rate amplitudes are linearly related to the data the rupture time and the duration are not the parameterization of the nonlinear variables has a strong effect on the generation of synthetic seismograms from a finite fault

structural heterogeneity and its implications for the low frequency tremors in southwest japan abstract to better understand the generation of low frequency tremors lfts that occurred in the nankai subduction zone detailed 3 d seismic velocity vp and vs and poisson s ratio structures are determined by inverting 181 576 p wave and 159 517 s wave arrival time data from 7572 earthquakes we also estimated the crack density e saturation rate and porosity structures along the lft belt using the inverted velocity data our results provide geophysical evidence for that the long duration tremors are closely related to the dehydration reactions of the subducting philippine sea slab and in the lowermost crust low vp low vs high high e high and high porosity anomalies are imaged at depths of 25 45 km along the lft belt which may indicate the existence of fluids liberated by the dehydration of the descending slab and or by the metamorphism in the lowermost crust the interpretation accords well with the behavior of the subducted hydrous minerals which are expected to dehydrate at the temperature of 350 500 c at depths of 35 50 km in southwest japan two prominent lft gaps between shikoku and kii peninsula and between kii peninsula and tokai along the tremor belt are imaged with low and low anomalies due to the lack of dehydration reactions within those gaps we conclude that the lfts are caused by the dehydrated fluids migrating in the faults and or by crack opening closing and extending in the corner of mantle wedge along the subducting philippine sea slab possibly due to the high pore fluid pressure and high crack density under the forearc region of the nankai subduction zone

timing and displacement of holocene faulting on the median tectonic line in central shikoku southwest japan abstract the median tectonic line mtl extends about 900 km parallel to the general trend of the southwest japan island arc the central segment of the mtl has been active during the quaternary although the average slip rate along the mtl is up to several mm a 1 there is no historical record of destructive earthquakes along it in order to collect data on the behavior of the mtl during late holocene times especially on the timing of seismic events and the amount of displacement during each event trench studies were conducted on the active segment in central shikoku in 1984 and 1988 the results are summarized as follows 1 the latest two seismic events produced by slip on the mtl in central shikoku occurred during the early 8th century a d and between 3250 and 2820 years b p 2 the amount of displacement during the latest event is inferred to have been about 5 7 m 3 the earthquake magnitude for the latest event is estimated at 7 9 richter scale and a fault segment trace about 70 km long ruptured during that event 4 an average slip rate along the active trace of the mtl in central shikoku during the late quaternary is estimated to be 5 8 mm a 1

evidence for a supershear transient during the 2002 denali fault earthquake elastodynamic considerations suggest that the acceleration of ruptures to supershear velocities is accompanied by the release of rayleigh waves along the fault from the stress breakdown zone these waves generate a secondary slip pulse trailing the rupture front but manifest almost entirely in ground motion perpendicular to the fault in the near source region we construct a spontaneously propagating rupture model exhibiting these features and use it to explain ground motions recorded during the 2002 denali fault earthquake at pump station 10 located 3 km from the fault we show that the initial pulses on both the fault normal and fault parallel components are due to the supershear stress release on the fault whereas the later arriving fault normal pulses result from the trailing subshear slip pulse on the fault online material mpeg movies of rupture history and ground motion

crustal structure fault segmentation and activity of the median tectonic line in shikoku japan abstract we conducted a seismic tomographic analysis to estimate the crustal structure beneath the shikoku and chugoku regions in japan the philippine sea slab phs slab subducts continuously in a se nw direction beneath this region and the crustal structure is complex furthermore the median tectonic line mtl one of the longest and most active arc parallel fault systems in japan hereafter the mtl active fault system is located in this area and the right lateral strike slip movement of this fault system is related to the oblique subduction of the phs slab the mtl active fault system has ruptured repeatedly during the last 10 000 years and has high seismic potential our tomographic analysis clarified the heterogeneous crustal structure along the mtl active fault system this fault system in shikoku can be divided into two segments an east segment and a west segment on the basis of the velocity structure this segmentation model is consistent with other such models that have been determined from geological and geomorphological data such as fault geometry slip rate and faulting history this consistency suggests that the surface characteristics of the mtl active fault system are related to structural properties of the crust in particular a prominent low velocity low v zone is present in the lower crust beneath the east segment our tomographic images show that the lower crust structure beneath the east segment is obviously different from that of the other segment furthermore this low v zone may indicate the presence of fluid possibly related to dehydration of the phs slab as the presence of fluid in the lower crust affects the activity of the fault stress accumulation and the fault failure mechanism may differ between the two segments of the mtl active fault system

a numerical approach to 14c wiggle match dating of organic deposits best fits and confidence intervals c 14 wiggle match dating wmd of peat deposits uses the non linear relationship between c 14 age and calendar age to match the shape of a sequence of closely spaced peat c 14 dates with the c 14 calibration curve a numerical approach to wmd enables the quantitative assessment of various possible wiggle match solutions and of calendar year confidence intervals for sequences of c 14 dates we assess the assumptions advantages and limitations of the method several case studies show that wmd results in more precise chronologies than when individual c 14 dates are calibrated wmd is most successful during periods with major excursions in the c 14 calibration curve e g in one case wmd could narrow down confidence intervals from 230 to 36 yr c 2003 elsevier science ltd all rights reserved

evidence for rapid fault healing derived from temporal changes in s wave splitting 1 tadokoro et al 1999 had made an s wave splitting analysis on the nojima fault zone that ruptured during the 1995 hyogo ken nanbu earthquake for a period 9 12 months after the mainshock the direction of faster shear wave polarization had been parallel to the fault strike suggesting fractures of shear fault origin in this study we made an additional s wave splitting analysis for a period 33 45 months after the mainshock and detected the rotation of that is the direction was parallel to the regional maximum horizontal compressional stress which is oblique to the fault strike this temporal change suggests that all the fractures of shear fault origin had completely healed and cracks of tectonic stress origin recovered between the two periods this is strong evidence for rapid fault healing which completed within 33 months after the mainshock

cumulative probability functions and their role in evaluating the chronology of geomorphological events during the holocene cumulative probability functions cpfs for large numbers of radiocarbon age determinations are increasingly being used by scientists as a methodology to discern environmental histories while the recent compilation of regional databases of the radiocarbon dating control for fluvial sediment sequences has been beneficial for identifying gaps in knowledge and stimulating new research there are a number of problems that critically undermine the use of these cpfs as sensitive hydroclimatic proxies i the cpf method is underpinned by the assumption that each radiocarbon measurement is a true age estimate for a point in time whereas each measured age in fact forms a scatter around the true age of the sample ii calibration of radiocarbon ages is responsible for much of the structure in cpfs and compounds the problem of scatter and smears the chronological control iii the databases incorporate multiple types of environmental changes differing chronological relationships between the 14c measurements and the dated events with pre dating dating or post dating chronological control each displaying variable length temporal lags all mixed together in the same analysis and iv the radiocarbon ages from individual case studies need to be more robustly tested before being incorporated into regional databases all these factors negate the value of cpfs as sensitive proxies of environmental change because peaks in probability for individual radiocarbon measurements are likely to be an incorrect estimate for the age of a geomorphological event and this problem is compounded by combining probabilities for multiple unrelated events in this paper we present a critical analysis of cpfs and their interpretation before suggesting alternative approaches to analysing radiocarbon geochronologies of geomorphic events which include i bayesian age modelling of river terrace development ii developing regional databases that test specific geomorphic hypotheses iii bayesian age modelling of palaeoflood records and iv analysis of sedimentation rates copyright 2011 john wiley sons ltd

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research