the rootzone of an ancient hydrothermal system exposed in the troodos ophiolite cyprus abstract a well exposed oceanic hydrothermal rootzone in the troodos ophiolite cyprus is composed of the basal sheeted dikes the upper 50 100 m of the gabbroic sequence and a contact aureole interpreted as a fossil conductive boundary layer the basal sheeted dikes and upper gabbros were pervasively altered at high temperatures 400 775 c and cut by a series of broadly distributed mineralized faults that are oriented parallel to the strike of the sheeted dike complex fluid inclusion and mineralogical data for fault breccias show that circulating fluids were 350 400 c fairly oxidizing and relatively h2s rich with a range in salinity 1 5 7 8 wt nacl equivalent field and petrological evidence suggest that the rootzone migrated from the basal sheeted dikes into the upper gabbros and back again perhaps for several cycles these migrations and p t oscillations in the conductive boundary layer were likely caused by fluctuations in thermal conditions imposed by the magmatic system at a spreadin

petrological statistical approach to interpret recent and subrecent lagoon subfacies idku nile delta of egypt abstract an approach combining petrology and statistics cluster analysis is developed to better distinguish a series of subfacies in surficial and short core samples from idku lagoon in the northwestern nile delta egypt the method integrates lithology physical and biogenic structures grain size and composition of the sand size fraction seven lithofacies eight grain size types and six clusters reveal comparable geographic distributions that are a direct response to geomorphic setting and depositional processes both of which have been modified by man although positioned in an arid setting and affected by anthropogenic factors land reclamation pollutants regional subfacies distribution patterns in idku lagoon are largely a function of the spatial configuration of freshwater dominated to brackish to higher salinity dominated near inlet zones typical of lagoons receiving significant freshwater input within idku a northern depositional province near the inlet and along the coastal sand barrier is defined by associations of terrigenous and coarse grained sediment types a southern province bounded by lagoon margins and marshes is characterized by finer grained sediment types with a high biogenic content recording lower energy levels the petrological statistical approach is used to identify and interpret lagoon subfacies in older to 6000 years b p core sections in idku region and in former abu qir lagoon additionally cluster analysis serves to determine specific lagoon subfacies from hand samples alone whether from surface grabs or cores this is based on a comparison of lithofacies and clusters determined for surficial and short core samples in the idku region to test the method a separate cluster analysis also using surficial and short core samples was used to define manzala lagoon subfacies in the northeastern nile delta results are generally comparable to those obtained in the idku study and show a close relation among manzala lagoon subfacies geomorphic configuration and depositional processes the petrological statistical method could be applied to other regions and also to the geological record

long term acceleration of aseismic slip preceding the mw 9 tohoku oki earthquake constraints from repeating earthquakes a decadal scale deformation transient preceding the 2011 mw 9 tohoku oki japan earthquake was reported from continuous gps data and interpreted as accelerating aseismic slip on the japan trench megathrust given the unprecedented nature of this transient independent confirmation of accelerating slip is required here we show that changes in the recurrence intervals of repeating earthquakes on the japan trench megathrust in the period 1996 to 2011 are consistent with accelerating slip preceding the tohoku oki earthquake all sequences of repeating earthquakes with statistically significant trends in recurrence interval at 95 confidence offshore south central tohoku occurred at an accelerating rate furthermore estimates of the magnitude of slip acceleration from repeating earthquakes are consistent with the completely independent geodetic estimates from a joint inversion of the gps and seismicity data we infer that a substantial portion of the megathrust experienced accelerating slip partly surrounding the eventual rupture zone of the mw 9 earthquake

propagation of slow slip leading up to the 2011 mw 9 0 tohoku oki earthquake many large earthquakes are preceded by one or more foreshocks but it is unclear how these foreshocks relate to the nucleation process of the mainshock on the basis of an earthquake catalog created using a waveform correlation technique we identified two distinct sequences of foreshocks migrating at rates of 2 to 10 kilometers per day along the trench axis toward the epicenter of the 2011 moment magnitude mw 9 0 tohoku oki earthquake in japan the time history of quasi static slip along the plate interface based on small repeating earthquakes that were part of the migrating seismicity suggests that two sequences involved slow slip transients propagating toward the initial rupture point the second sequence which involved large slip rates may have caused substantial stress loading prompting the unstable dynamic rupture of the mainshock

age origin and climatic controls on vegetated linear dunes in the northwestern negev desert israel abstract the stabilized northwestern nw negev vegetated linear dunes vld of israel extend over 1300 km 2 and form the eastern end of the northern sinai nw negev erg this study aimed at identifying primary and subsequent dune incursions and episodes of dune elongation by investigating dune geomorphology stratigraphy and optically stimulated luminescence osl dating thirty five dune and interdune exposed and drilled section were studied and sampled for sedimentological analyses and osl dating enabling spatial and temporal elucidation of the nw negev dunefield evolution in a global perspective the nw negev dunefield is relatively young though sporadic sand deposition has occurred during the past 100 ka dunes began to accumulate over large portions of the dunefield area only at 23 ka three main chronostratigraphic units corresponding to three osl age clusters were found throughout most of the dunefield indicating three main dune mobilizations late to post last glacial maximum lgm at 18 11 5 ka late holocene 2 0 8 ka and modern 150 8 years the post lgm phase is the most extensive and it defined the current dunefield boundaries it involved several episodes of dune incursions and damming of drainage systems dune advancement often occurred in rapid pulses and the orientation of vld long axes indicates similar long term wind directions the late holocene episode included partial incursion of new sand reworking of late pleistocene dunes as well as limited redeposition the modern sand movement only reactivated older dunes and did not lengthen vlds this aeolian record fits well with other regional aeolian sections we suggest that sand supply and storage in sinai was initiated by the late pleistocene exposure of the nile delta sands late pleistocene winds substantially stronger than those usually prevailing since the onset of the holocene are suggested to have transported the dune sands across sinai and into the northwestern negev our results demonstrate the sensitivity of vegetated linear dunes located along the northern fringe of the sub tropical desert belt to climate change i e wind and sediment supply

interplate coupling in the kanto district central japan and the boso peninsula silent earthquake in may 1996 i studied crustal deformation in the kanto district central japan based on continuous gps data horizontal as well as vertical displacement rate demonstrate significant interaction between the landward kanto block and the philippine sea plate although the subduction effect of the pacific plate is not apparent it is reasonable to consider the entire kanto district is displaced westward due to the interaction with the pacific plate the gps velocity data were inverted to estimate the slip deficit distribution on the sagami trough subduction zone the result delineates a strongly coupled region on the plate interface part of which corresponds to the 1923 kanto earthquake the strongly coupled region is located shallower than 20 km in addition the plate interaction is laterally heterogeneous even in the same depth range implying thermal structure is not the only factor controlling interplate coupling the gps data also detected a silent earthquake event on the interface of the philippine sea slab east of the boso peninsula in the middle of may 1996 the silent rupture propagated over a 50 km 50 km wide area during about a week the maximum slip was approximately 50 mm and the released seismic moment was 4 7 1018nm mw 6 4 there was a small seismicity triggered by this silent event the silent slip was located in the peripheral of the strongly coupled area suggesting that frictional properties and or stress conditions are inhomogeneous on the plate boundary interface

pre and post seismic slow slip on the plate boundary off sanriku ne japan associated with three interplate earthquakes as estimated from small repeating earthquake data abstract the spatio temporal variation of quasi static slow slip on the plate boundary before and after three major earthquakes mj 7 1 in 1989 mj 6 9 in 1992 and mj 7 6 in 1994 off sanriku northeastern japan is estimated using small repeating earthquake data the small repeating earthquake sequence employed is considered to correspond to repeated rupture of a small isolated asperity surrounded by a quasi static slipping area and the activity of the source reflects the quasi static slip rate small repeating earthquakes accompanying moderate sized events appear to have been activated prior to the major events under investigation with activity starting 6 days 2 days and 8 months before the occurrence of the 1989 1992 and 1994 events these results indicate that the quasi static slip near the hypocenters of these major earthquakes was accelerated prior to the main shocks causing stress concentration at the asperities responsible for the main shocks this idea is supported by the fact that both the epicenters locations of initial breaks and areas where quasi static slip was accelerated were located on the same side of the main shock asperities migration of quasi static slip acceleration in the off sanriku region was also identified apparent in the aftershock activity of the 1994 event and the earthquake swarms including the 1989 mj 7 1 and 1992 mj 6 9 events the present results reveal that quasi static slip may have played a crucial role in the occurrence of these large earthquakes as well as contributing to aftershock and swarm activity on the plate boundary

the mw 9 0 northeast japan earthquake total rupture of a basement asperity summary the mw 9 0 off northeast japan tohoku oki earthquake occurred on 2011 march 11 at the interface between the north american na and pacific pa plates the occurrence of interplate earthquakes can be regarded as the sudden release of tectonic stress accumulated by the interseismic gradual increase of slip deficit in source regions the inversion analysis of gps velocity data for a seismically calm period 1996 2000 before the tohoku oki earthquake has revealed the existence of five remarkable slip deficit zones distributed on the na pa plate interface along the southern kuril japan trench we analysed coseismic gps displacement data for the tohoku oki earthquake with the same inversion method and obtained the bimodal distribution of coseismic slip spreading over the southern two miyagi oki and fukushima oki interseismic slip deficit zones the maximum slip is 32 m for the miyagi oki slip deficit zone but only 7 m for the fukushima oki slip deficit zone the extraordinarily large coseismic slip in the miyagi oki slip deficit zone where ordinarily large earthquakes with about 3 m coseismic slips have repeated every 40 yr in the past two centuries suggests the total rupture of a 300 km long basement asperity underlying much smaller scale local asperities

space time model for repeating earthquakes and analysis of recurrence intervals on the san andreas fault near parkfield california we propose a stochastic model for characteristically repeating earthquake sequences to estimate the spatiotemporal change in static stress loading rate these earthquakes recur by a cyclic mechanism where stress at a hypocenter is accumulated by tectonic forces until an earthquake occurs that releases the accumulated stress to a basal level renewal processes are frequently used to describe this repeating earthquake mechanism variations in the rate of tectonic loading due to large earthquakes and aseismic slip transients however introduce nonstationary effects into the repeating mechanism that result in nonstationary trends in interevent times particularly for smaller magnitude repeating events which have shorter interevent times these trends are also similar among repeating earthquake sites having similar hypocenters therefore we incorporate space time structure represented by cubic b spline functions into the renewal model and estimate their coefficient parameters by maximizing the integrated likelihood in a bayesian framework we apply our model to 31 repeating earthquake sequences including 824 events on the parkfield segment of the san andreas fault and estimate the spatiotemporal transition of the loading rate on this segment the result gives us details of the change in tectonic loading caused by an aseismic slip transient in 1993 the 2004 parkfield m6 earthquake and other nearby or remote seismic activities the degree of periodicity of repeating event recurrence intervals also shows spatial trends that are preserved in time even after the 2004 parkfield earthquake when time scales are normalized with respect to the estimated loading rate

a decadal scale deformation transient prior to the 2011 mw 9 0 tohoku oki earthquake gps time series in northeast japan exhibit nonlinear trends from 1996 to 2011 before the mw 9 0 2011 tohoku oki earthquake after removing reference frame noise we model time series as linear trends plus constant acceleration correcting for coseismic and postseismic effects from the numerous mw 6 5 earthquakes during this period we find spatially coherent and statistically significant accelerations throughout northern honshu large areas of japan outside the tohoku region show insignificant accelerations demonstrating that the observation is not due to network wide artifacts while the accelerations in northern tohoku sanriku area can be explained by decaying postseismic deformation from pre 1996 earthquakes the accelerations in south central tohoku appear unrelated to postseismic effects the latter accelerations are associated with a decrease in average trench normal strain rate and can be explained by increasing slip rate on the japan trench plate interface and or updip migration of deep aseismic slip in the decades before the 2011 tohoku oki earthquake

the fluvial evolution of the holocene nile delta abstract the evolution of the nile delta the largest delta system in the mediterranean sea has both high palaeoenvironmental and archaeological significance a dynamic model of the landscape evolution of this delta system is presented for the period c 8000 4500 cal bp analysis of sedimentary data and chronostratigraphic information contained within 1640 borehole records has allowed for a redefinition of the internal stratigraphy of the holocene delta and the construction of a four dimensional landscape model for the delta s evolution through time the mid holocene environmental evolution is characterised by a transition from an earlier set of spatially varied landscapes dominated by swampy marshland to better drained more uniform floodplain environments archaeologically important pleistocene inliers in the form of sandy hills protruding above the delta plain surface known as turtlebacks also became smaller as the delta plain continued to aggrade while the shoreline and coastal zone prograded north these changes were forced by a decrease in the rate of relative sea level rise under high rates of sediment supply this dynamic environmental evolution needs to be integrated within any discussion of the contemporary developments in the social sphere which culminated in the emergence of the ancient egyptian state c 5050 cal bp

late quaternary stratigraphy and paleogeography of the eastern nile delta egypt abstract a petrological study of numerous sediment borings identifies the late pleistocene and holocene lithofacies in the northeastern nile delta of egypt a coarsening upward sequence characterizes the major holocene depocenters located along the northern margin of the present delta stratigraphic correlation of radiocarbon dated sections and mapping of key facies such as delta front mud reveal the locations of four major holocene delta lobes related to former distributary branches of the nile river mendesian pelusiac tanitic and pre modern damietta these lobes formed primarily of marine prodelta and delta front deposits interfinger geographically but radiocarbon dating indicates that their bases are not synchronous lobes developed for the most part since 8000 years b p i e as the rate of eustatic sea level rise began to decrease climatic and sediment discharge fluctuations lateral migrations of distributaries and isostatic subsidence of land are additional factors that affected the temporal and spatial distributions of the lobes paleogeographic maps reveal the changes with time in the distributions of different lobes and deltaic plain environments marsh lagoons and concomitant displacement of the coastline holocene sediment accumulation rates to 500 cm per 1000 years are calculated this is 10 times greater than that on the nile cone and 50 times greater than on the egyptian continental shelf the delta coastal margin in the study area migrated northward by as much as 50 km during the past 5000 years an average progradational rate of up to 10 m per year the general configuration of the present delta developed during the past millennium the major changes recently induced by man in this region coupled with a series of continuing natural phenomena slow rise in sea level coastal erosion subsidence have markedly affected the evolution of the delta petrological study of the nile delta sediments provides baseline reference information to help recognize changes in the recent geological past to help identify those taking place at present and possibly to help predict those likely to occur in this region in the future

molluscan faunas and paleobathymetry of holocene sequences in the northeastern nile delta egypt abstract the fossil molluscan component serves as a valuable indicator of the paleobathymetric variations which occurred in the nile delta egypt during the past 7500 years paleobiocoenoses have been identified on the basis of molluscan faunas in three radiocarbon dated cores as part of a long term study to help interpret the holocene evolution of the northeastern delta one of these smithsonian boring s 21 near port said has been selected as a type core because it includes a near complete holocene coarsening upward sequence of distinct open marine to coastal lithofacies typical of this depocenter the fossil molluscan faunas comprising 59 species all of which are presently living in the mediterranean serve to determine approximate changes in paleodepth at this site with time in particular the recognized paleocommunities show a good correspondence with several infralittoral biocoenoses of unconsolidated mud and sand rich substrates of the present mediterranean terrigenous mud fine well sorted sands fine sands in very shallow water and superficial muddy sands in sheltered areas the methodology was applied to two other cores of near comparable age in this region smithsonian core s 31 and boring fadda 1 earlier studied by others these two were also selected because they are characterized by a holocene sequence of marine to coastal lithologies similar to core s 21 the approach used serves to determine temporal and spatial differences in paleobathymetry at the three sites this investigation shows that analysis of the faunas in subsurface sections serves to refine paleoenvironmental interpretations of the nile delta moreover the molluscan paleobiocoenoses are best evaluated in conjunction with the lithofacies in which they occur

quasi static slip on the plate boundary associated with the 2003 m8 0 tokachi oki and 2004 m7 1 off kushiro earthquakes japan abstract we analyzed small repeating earthquakes recorded over a 13 year period and gps data recorded over an 8 month period to estimate interplate quasi static slip associated with the 2003 tokachi oki earthquake m8 0 and the 2004 off kushiro earthquake m7 1 the repeating earthquake analysis revealed that the slip rate near the source region of the tokachi oki earthquake was relatively low

morphology and dynamic sedimentology of the eastern nile delta shelf coleman j m roberts h h murray s p and salama m 1981 morphology and dynamic sedimentology of the eastern nile delta shelf mar geol 42 301 326 some 13 000 km of bathymetry and overlapping side scan sonar data were collected over a 4450 km2 area of the eastern nile river shelf these data coupled with more detailed surveys of selected areas including bottom sampling and current measurements contribute to the understanding of shelf morphology lithofacies relationships and sediment transport processes four morphologic zones were defined zone 1 smooth bottomed flocculated clays and silty clays extending from the shore line 40 km seaward to the 25 m contour zone 2 a sand belt 5 20 km wide extending eastward from the damietta mouth and curving toward the coast at the boundary of the study area dominant bottom features were migratory bedforms of various dimensions superimposed on linear sand ridges zone 3 smooth clay to silty clay bottom topography punctuated with distinct algal mounds the mounds up to 10 m relief are composed of living coralline algae which contribute coarse debris to the surrounding sediments zone 4 mud diapirs and shelf edge slumps characterize this distal part of the shelf and the upper slope sand on the inner shelf is actively migrating and probably does not represent a relict deposit the damietta distributary causes a large scale perturbation in the mean easterly drift along the egyptian coast unusually strong currents capable of transporting and reworking large volumes of sand are associated with an eddy trapped behind this feature the directionality of these currents and the curvature of the eddy axis correspond well to the distribution pattern of sand on the inner shelf

spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 mw 9 0 tohoku oki earthquake 1 imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle both geodetic and seismic estimates of the coseismic rupture extent for the march 11 2011 mw 8 9 9 0 earthquake tohoku oki earthquake may be spatially correlated 0 26 0 05 to 0 82 0 05 with a region estimated to be partially to fully coupled in the interseismic period preceding the earthquake though there is substantial variation in the estimated distribution and magnitude of coseismic slip the 400 km long region estimated to have slipped 4 m corresponds to an area of the subduction zone interface that was coupled at 30 of long term plate convergence rate with peak slip near a region coupled 80 the northern termination of rupture is collocated with a region of relatively low 20 interseismic coupling near the epicenter of the 1994 mw 7 6 sanriku oki earthquake and near a region of potential long term low coupling or ongoing slow slip slip on the subduction interface beneath the coastline 40 50 km depth is best constrained by the land based gps data and least constrained on the shallowest portion of the plate interface due to the 230 km distance between geodetic observations and the japan trench

3 d modelling of plate interfaces and numerical simulation of long term crustal deformation in and around japan we developed a 3 d simulation model for long term crustal deformation due to steady plate subduction in and around japan by incorporating viscoelastic slip response functions into a realistic 3 d plate interface model constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes the lithosphere asthenosphere system is modelled by an elastic surface layer overlying a maxwellian viscoelastic half space kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity fault slip across the interfaces with this model giving the steady slip rates at plate interfaces calculated from nuvel 1a we simulated long term crustal deformation due to steady plate subduction in and around japan the simulated crustal deformation pattern is characterized by steep uplift at island arcs sharp subsidence at ocean trenches and gentle uplift at outer rises the numerical results show the strong dependence of the deformation pattern on the 3 d geometry of plate interfaces

clustering and periodic recurrence of microearthquakes on the san andreas fault at parkfield california the san andreas fault at parkfield california apparently late in an interval between repeating magnitude 6 earthquakes is yielding to tectonic loading partly by seismic slip concentrated in a relatively sparse distribution of small clusters 20 meter radius of microearthquakes within these clusters which account for 63 of the earthquakes in a 1987 92 study interval virtually identical small earthquakes occurred with a regularity that can be described by the statistical model used previously in forecasting large characteristic earthquakes sympathetic occurrence of microearthquakes in nearby clusters was observed within a range of about 200 meters at communication speeds of 10 to 100 centimeters per second the rate of earthquake occurrence particularly at depth increased significantly during the study period but the fraction of earthquakes that were cluster members decreased

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

periodic slow slip triggers megathrust zone earthquakes in northeastern japan both aseismic and seismic slip accommodate relative motion across partially coupled plate boundary faults in northeastern japan aseismic slip occurs in the form of decelerating afterslip after large interplate earthquakes and as relatively steady slip on uncoupled areas of the subduction thrust here we report on a previously unrecognized quasi periodic slow slip behavior that is widespread in the megathrust zone the repeat intervals of the slow slip range from 1 to 6 years and often coincide with or precede clusters of large magnitude m 5 earthquakes including the 2011 m 9 tohoku oki earthquake these results suggest that inherently periodic slow slip events result in periodic stress perturbations and modulate the occurrence time of larger earthquakes the periodicity in the slow slip rate has the potential to help refine time dependent earthquake forecasts

3 d spatial variation of b values of magnitude frequency distribution beneath the kanto district japan summary a method is developed for estimation and interpolation of 6 values in space a 3 d spline function is considered for the logarithm of the 6 value at each location in the space since many parameters for the spline coefficients are required to obtain a sensible estimate of the spatial variation of 6 values we consider the penalized log likelihood with the standard roughness penalties for the spline function further the error bands of the b value estimation at each location can be calculated using the current method the spatial distribution of 6 values beneath the kanto district down to the depth of 100km is determined based on hypocentral data of microearthquakes from the kanto tokai observational network of the national research center for disaster prevention the stability of the estimated pattern is checked by comparing with the results using alternative cut off magnitudes this is further ensured by comparison with the result obtained by an alternative model using equally divided blocks on the whole the vertical change in 6 value is greater than the horizontal one it is high in the crust of the eurasian plate especially above the upper boundary of the subducting pacific plate and in the northwest part or the volcanic area in the kanto district a steep decrease of the 6 values is seen to take place in perpendicular direction to the subducting pacific plate boundary also a similar change is seen in the boundary between the eurasian and phillippine sea plates especially beneath the southern part of the kanto plain the 6 value is low in the upper boundary of the subducting plates but high in the lower plane of the double seismic zone in the pacific plate it appears that even within a narrow area of aftershocks the 6 value can change significantly it is also found that the variation of the 6 value estimate is in good agreement with the structure of seismic wave fractional velocity perturbations the regions of high and low 6 values correspond respectively to the lower and higher parts of the p wave velocity the similar relationship is seen with the spatial structure of the seismic wave attenuation

pre and postseismic slow slip surrounding the 2011 tohoku oki earthquake rupture abstract slow aseismic slip that accommodates part of the long term plate motion on subduction megathrusts is thought to be strongly related to the occurrence of large earthquakes on the same fault zone however the temporal evolution and spatial distribution of the aseismic slip before major earthquakes and of accelerated postseismic afterslip are largely unconstrained we estimate cumulative offsets of small repeating earthquakes that are interpreted to reflect the in situ aseismic slip history on the subduction zone offshore northeastern japan these data reveal contrasting aseismic slip patterns between the coseismic rupture area of the mw 9 0 tohoku oki earthquake and surrounding portions of the subduction thrust the rupture area is characterised by low and variable slip rates before 2008 and the slip stopped almost completely after the earthquake the region surrounding the rupture area exhibited higher aseismic fault slip rates before the earthquake and clear postseismic slip of up to 1 6 m within 9 months following the main shock the frictional fault properties and complete relief of ambient stress in the central rupture zone of the main shock probably control the observed distribution the postseismic slip shows a more abrupt increase in the region closer to the source suggesting outwards propagation of afterslip small but distinct increases in the slip rate in the 3 yr before the earthquake near the area of large coseismic slip suggests preseismic unfastening of the locked area in the last stage of the earthquake cycle

3 d simulation of earthquake generation cycles and evolution of fault constitutitve properties the earthquake generation cycle consists of tectonic loading quasi static rupture nucleation dynamic rupture propagation and stop and subsequent stress redistribution and fault restrengthening from a macroscopic point of view the entire process of earthquake generation cycles should be consistently described by a coupled nonlinear system of a slip response function a fault constitutive law and a driving force on the basis of such a general idea we constructed a realistic 3 d simulation model for earthquake generation cycles at a transcurrent plate boundary by combining the viscoelastic slip response function derived for a two layered elastic viscoelastic structure model the slip and time dependent fault constitutive law that has an inherent mechanism of fault restrengthening and the steady relative plate motion as a driving force into a single closed system with this model we numerically simulated the earthquake generation cycles repeated in a seismogenic region on a plate interface and examined space time changes in shear stress slip deficits and fault constitutive properties during one complete cycle in detail the occurrence of unstable dynamic slip brings about decrease both in fault strength and shear stress to a constant residual level after the arrest of dynamic slip the breakdown strength drop p of fault is restored rapidly and the process of stress accumulation resumes in the seismogenic region on the other hand the restoration of the critical weakening displacement d c proceeds gradually with time through the interseismic period the restoration of d c can be regarded as the macroscopic manifestation of the microscopic recovery process of fractal fault surface structure through numerical simulation with a multi segmented fault model we examined the effects of viscoelastic faultto fault interaction the effect of transient viscoelastic stress transfer through the asthenosphere is significant as well as the direct effect of elastic stress transfer and it possibly explains the time lag of the sequential occurrence of large events along a plate boundary

seismological studies at parkfield vi moment release rates and estimates of source parameters for small repeating earthquakes abstract waveform data from a borehole network of broadband seismographic stations have been used to study microearthquakes along the parkfield segment of the san andreas fault saf analysis of almost 10 years of such data demonstrates that much of the seismicity in this region consists of repeating sequences quasiperiodic sequences of earthquakes that are essentially identical in terms of waveform size and location scalar seismic moments have been estimated for 53 of these repeating sequences and combined with equivalent estimates from 8 similar but larger event sequences from the stone canyon section of the fault and the main parkfield sequence these estimates show that seismic moment is being released as a function of time in a very regular manner measurements of the moment release rate combined with an assumed tectonic loading rate lead to estimates of the seismic parameters source area slip and recurrence interval such parameters exhibit a systematic dependence upon source size over a range of 10 10 in seismic moment that can be described by three simple scaling relationships several implications of these scaling relationships are explored including the repeat time of earthquakes average stress drop strength of the fault and heat generated by earthquakes what emerges from this analysis of moment release rates is a quantitative description of an earthquake process that is controlled by small strong asperities that occupy less than 1 of the fault area this means that the fault is highly heterogeneous with respect to stress strength and heat generation such heterogeneity helps to explain many of the apparent contradictions that are encountered in the study of earthquakes such as why faults appear weak why significant heat flow is not observed how significant high frequencies can be generated by large earthquakes and how various geologic features such as pseudotachylytes might form

holocene evolution of the northeastern corner of the nile delta abstract the constructive phase of the modern nile delta as manifested in a 48 m section drilled east of the suez canal commenced in very early holocene times sands rich in marine fauna were deposited in the littoral zone and the shoreline was more than 20 km landward of its present day position subsequently clays and silts were dumped from the nile distributaries and the marine faunal spectrum became very limited and brackish later in early and middle holocene times the sediments deposited were rich in freshwater delta plain diatoms and pollen and in allochthonous fern spores from the tropics indicating proximity of a distributary mouth the middle part of the section 22 5 17 5 m is very poor in faunal and floral remains pollen grains from sabkha vegetation are abundant the environment which seems lagoonal and slightly hypersaline is related to the sea regression in middle holocene times euryhaline pelecypods dating from about 3000 yr b p are abundant around the 8 m depth upward there is an increase in pollen grains from sabkhas the section is poor in diatoms and those present are mostly euryhaline and lagoonal allochthonous spores derived from the nearby pelusiac branch are abundant between 3000 and 2000 yr b p the constructive phase of the modern delta terminated and winnowed sands began accreting in front of the delta plain

interplate seismogenic zones along the kuril japan trench inferred from gps data inversion stress accumulation between earthquakes results from slip that is insufficient to fully accommodate plate movement an inverse analysis of gps data from the kuril japan trench reveals a trench parallel belt of stress accumulation with six peaks in the depth range of 10 40 km suggesting potential source regions for future earthquakes in the subduction zones around japan where four plates interact with one another large earthquakes have occurred repeatedly1 these interplate earthquakes are part of the process of tectonic stress accumulation and release that is driven by relative plate motion2 3 4 stress accumulation between earthquakes results from slip deficit slip that is insufficient to fully accommodate plate movement for the prediction of large earthquakes it is therefore important to monitor the distribution of slip deficit on plate interfaces here we apply an inversion method based on bayesian modelling using direct and indirect prior information on the magnitude and distribution of fault slip5 to horizontal and vertical velocities from global positioning system data for the seismically calm period between 1996 and 2000 we obtain a precise distribution of slip deficit rates on the interface between the north american and pacific plates around japan which reveals a trench parallel belt of slip deficit with six peaks in the depth range of 10 40 km these peaks agree with the source regions of past large interplate earthquakes along the kuril japan trench we conclude that the slip deficit zones identified with our method are potential source regions of large earthquakes

3 d physical modelling of stress accumulation processes at transcurrent plate boundaries we constructed a 3 d physical model of tectonic loading at transcurrent plate boundaries by considering viscoelastic stress relaxation in the asthenosphere and spatial variation in frictional properties peak strength and critical weakening displacement of faults with this model we simulated the process of stress accumulation and release at a seismogenic region with relatively high strength on the plate interface in low strength regions surrounding the seismogenic region quasi static fault slip gradually proceeds with the progress of relative plate motion the increase of slip deficits in the seismogenic region brings about stress concentration at its margin the stress accumulation rate is roughly proportional to the inverse of the effective fault length the accumulated stress is released by unstable dynamic rupture if the critical weakening displacement d c is small and by stable fault slip if d c is very large when a fault system consists of two adjacent seismogenic regions sudden stress release in one region accelerates the stress accumulation process in another region through transient viscoelastic stress transfer as well as instantaneous elastic stress transfer this indicates the importance of elastic and viscoelastic interaction between adjacent seismic faults even in stress accumulation processes

earthquake triggering by migrating slow slip initiated by m8 earthquake along kuril trench japan 1 evidence of a slow slip temporally ahead of the m7 earthquake doublet that occurred in november december 2004 offshore of eastern hokkaido japan was registered in continuous gps measurements the gps data suggest that a slow slip around a forthcoming rupture zone on the plate boundary triggered these earthquakes this slow slip episode was itself triggered by the m8 tokachi earthquake of september 2003 this is a demonstration of the geodetic visualization of the mechanism of a triggering of a subsequent earthquake caused by a preceding large earthquake the geodetic data will improve the reliability of the warning of an occurrence of a subsequent earthquake after a large one that is currently dependent on only co seismic static stress increase

simulation of the transition of earthquake rupture from quasi static growth to dynamic propagation we have simulated a rupture transition from quasi static growth to dynamic propagation using the boundary integral equation method in order to make a physically reasonable model of earthquake cycle we have to evaluate the dynamic rupture propagation in the context of quasi static simulation we used a snapshot of the stress distribution just before the earthquake in the quasi static simulation the resultant stress will be fed back to the quasi static simulation since the quasi static simulation used the slip and time dependent constitutive relation the friction law itself evolves with time thus we used the slip weakening constitutive relation for dynamic rupture propagation consistent with that used for the quasi static simulation we modeled a san andreas type strike slip fault in which two different size asperities existed

fault slip rates at depth from recurrence intervals of repeating microearthquakes unique attributes in sequences of recurring similar microearthquakes at parkfield california provide a means for inferring slip rate at depth throughout the active fault surface from the time intervals between sequence events application of the method using an 11 year microseismicity record revealed systematic spatial and temporal changes in the slip rate that were synchronous with earthquake activity and other independent measures of fault zone slip if this phenomenon is found to be generally common behavior in active faults it forms the basis for a method to monitor the changing strain field throughout a seismogenic fault zone

repeating earthquakes and interplate coupling along the western part of the north anatolian fault abstract the sea of marmara accommodates segments of the north anatolian fault naf in turkey and remains the only part of the western naf that has not ruptured during the last century at its nearest the segment is 20 km from istanbul the largest city in turkey thus it is important to understand the locking state of the fault since it illuminates the strain accumulation rate along the fault segments which in turn is an important input parameter in seismic hazard studies to infer the interplate locking state we used repeating earthquakes that indicate fault creep in the surrounding area using long term april 2005 to may 2013 seismic observations at 12 broadband seismic stations operated by bogazici university kandilli observatory and earthquake research institute we defined repeating earthquakes from waveform coherences that were 0 95 for 40 second long waveforms of the vertical component using the selection procedure we found 21 repeating earthquakes with magnitude 2 3 to 3 2 that are grouped into 9 sequences they are distributed along the main naf comprising three groups of activity one group in the sea of marmara and a group either side to the east and west the three groups are located near the boundary of previous large earthquake ruptures suggesting relatively weak coupling there we also estimated the fault creep rate from the cumulative slip of the repeating earthquakes using a scaling relationship between repeating earthquakes moment and slip the slip rate for these three groups are similar 3 4 cm yr and comparable to albeit slightly higher than those expected from global plate models 2 4 cm yr this suggests relatively weak locking around the groups the relocation results of the repeating earthquake hypocenters in the sea of marmara suggest the creep is occurring at 10 to 20 km depth these results suggest heterogeneous coupling in the segment

physics based 3 d simulation for earthquake generation cycles at plate interfaces in subduction zones the generation of interplate earthquakes can be regarded as a process of tectonic stress accumulation and release driven by relative plate motion we completed a physics based simulation system for earthquake generation cycles at plate interfaces in the japan region where the pacific plate is descending beneath the north american and philippine sea plates and the philippine sea plate is descending beneath the north american and eurasian plates the system is composed of a quasi static tectonic loading model and a dynamic rupture propagation model developed on a realistic 3 d plate interface model the driving force of the system is relative plate motion in the quasi static tectonic loading model mechanical interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity fault slip across them on the basis of dislocation theory for an elastic surface layer overlying maxwell type viscoelastic half space in the dynamic rupture propagation model stress changes due to fault slip motion on non planar plate interfaces are evaluated with the boundary integral equation method the progress of seismic dynamic or aseismic quasi static fault slip on plate interfaces is governed by a slip and time dependent fault constitutive law as an example we numerically simulated earthquake generation cycles at the source region of the 1968 tokachi oki earthquake on the north american pacific plate interface from the numerical simulation we can see that postseismic stress relaxation in the asthenosphere accelerates stress accumulation in the source region when the stress state of the source region is close to a critical level dynamic rupture is rapidly accelerated and develops over the whole source region when the stress state is much lower than the critical level the rupture is not accelerated this means that the stress state realized by interseismic tectonic loading essentially controls the subsequent dynamic rupture process

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

recent subsidence and northeast tilting of the nile delta egypt abstract sediment borings collected in the nile delta of egypt many of them radiocarbon dated indicate that the entire northern sector of this major depositional center in the eastern mediterranean is presently subsiding mapping of the base of the holocene deltaic facies which is dated at about 8000 6500 yrs b p reveals that differential lowering of the northern delta plain is preferentially accentuated toward the northeast long term subsidence rates at or near the coast averaged for the mid to upper holocene range from about 0 1 to 0 25 cm yr between alexandria and the north central delta margin rates increase markedly eastward to a maximum of about 0 5 cm yr in the port said manzala lagoon region and this rapid lowering explains the presence of thick marine delta lobe sequences of holocene age in cores in the northeastern delta in contrast only reworked remnants of holocene marine delta lobe deposits of the earlier river nile branches which once flowed to the north and northwest are preserved seaward of the present north delta coast subsidence has induced marked environmental changes particularly with respect to coastal erosion and salt water incursion the asymmetric pattern of saline ground water here attributed in part to the northeast tilt of the delta plain has serious implications for agricultural development in this intensely cultivated region

subsidence in the northeastern nile delta rapid rates possible causes and consequences holocene fluvial and marine deposits have accumulated in a graben like structure on the northeastern margin of the nile delta this part of the delta which includes lake manzala port said and the northern suez canal has subsided rapidly at rates of up to 0 5 centimeter per year since about 7500 years ago this subsidence has diverted at last four major distributaries of the nile river into this region the combined effects of continued subsidence and sea level rise may flood a large part of the northern delta plain by as much as 1 meter by the year 2100 the impact of continued subsidence now occurring when sediment input along the coast has been sharply reduced because of the aswan high dam is likely to be substantial particularly in the port said area and as far inland as south of lake manzala