self similar earthquake triggering bath s law and foreshock aftershock magnitudes simulations theory and results for southern california 1 bath s law the observation that the largest aftershock is on average 1 2 magnitudes smaller than its main shock independent of main shock size suggests some degree of self similarity in earthquake triggering this behavior can largely be explained with triggering models in which the increased triggering caused by larger magnitude events is exactly compensated for by their decreased numbers and these models can account for many features of real seismicity catalogs the bath s law magnitude difference of 1 2 places a useful constraint on aftershock productivity in these models a more general test of triggering self similarity is to plot foreshock and aftershock rates as a function of magnitude m relative to the main shock magnitude mmax of the largest event in the sequence both computer simulations and theory show that these dn dm curves should be nearly coincident regardless of main shock magnitude the aftershock dn dm curves have the same gutenberg richter b value as the underlying distribution but the foreshock dn dm curves have the same b value only for foreshock magnitudes less than about mmax 3 for larger foreshock values the dn dm curve flattens and converges with the aftershock dn dm curve at m mmax this effect can explain observations of anomalously low b values in some foreshock sequences and the decrease in apparent aftershock to foreshock ratios for small magnitude main shocks observed apparent foreshock and aftershock dn dm curves for events close in space and time to m 2 5 to 5 5 main shocks in southern california appear roughly self similar but differ from triggering simulations is several key respects 1 the aftershock b values are significantly lower than that of the complete catalog 2 the number of aftershocks is too large to be consistent with bath s law and 3 the foreshock to aftershock ratio is too large to be consistent with bath s law these observations indicate for southern california that triggering self similarity is not obeyed for these small main shocks or that the space time clustering is not primarily caused by earthquake to earthquake triggering

hydrological characteristics of the drainage system beneath a surging glacier a rare combination of natural circumstances permits assessment of current theories on water flow beneath glaciers outburst floods from the subglacial lake grimsvotn in iceland took place before during and after surging of skei ararjokull the glacier beneath which the outburst floods drain the observable drainage patterns associated with these floods show the different nature of the basal water conduit system of the glacier during surge and non surge phases during surge conditions basal water is dispersed slowly across the bed in a distributed drainage system but when the glacier is not surging water is transported rapidly through a system of tunnels

formation of smooth terrains on comet tempel 1 abstract we suggest that the regions of smooth terrain which were observed on comet 9p tempel 1 by the deep impact spacecraft were formed by blowing ice grains in an outburst of gas from the comet interior when gas is released from 10 to 20 m deep layers which were heated to 135 k it is released quiescently onto the surface by individual conduits if large amounts of gas are released the drainage system cannot release them fast enough and wider interconnected channels are formed leading to sudden outburst of gas instability triggering a sudden shift of flow is well known in subglacial drainage of water the ballistic trajectory of the ice particles reach a distance of 3 km in the atmosphereless comet whose gravity is 0 034 cm s 1 if ejected at an angle of 45 at a speed of 95 cm s 1 this speed is close to the speeds measured in laboratory experiments 167 140 sin i and 167 cm s 1 for particles of 0 3 1000 and 14 650 m respectively blowing of ice grains can overcome the 1650 m long horizontal section of smooth terrain i1 fig 1 whereas simple flow of material downhill would stop close to the foot of the hill the ice particles at the end of their trajectory have a horizontal velocity component and this low velocity ballistic sedimentation would lead to formation of lineaments on the smooth terrain like in solid particulate volcanic eruptions

aftershock statistics of major subduction earthquakes abstract large megathrust subduction earthquakes generate prolific aftershock sequences which last over an extended period of time and affect wide spatial areas among those aftershocks the largest ones can cause additional damage and pose significant risks to population and infrastructure therefore modeling aftershock sequences of large subduction earthquakes is of considerable importance for seismic hazard assessment and earthquake risk mitigation it can also play a prominent role in the ground shaking modeling of major mainshock aftershock sequences in this work we analyze statistical properties of aftershock sequences of large subduction earthquakes worldwide which occurred from 1973 to present including recent catastrophic events in sumatra chile and japan we use information provided in the national earthquake information center neic catalog to extract 70 aftershock sequences generated by mainshocks of m 7 0 and above we construct their temporal decay rates and magnitude frequency statistics to model their temporal behavior we estimate the parameters of the modified omori law in the magnitude domain we model the frequency magnitude statistics using the gutenberg richter scaling relationship we also analyze statistically the difference between the magnitude of the mainshock and the corresponding largest aftershock in the sequence and discuss this in terms of bath s law one of the main goals of this work is to investigate the variation in parameter values of the above empirical laws with respect to the magnitude of the mainshock our main finding indicates that most parameters do not depend on the magnitude of the mainshock however they show some variation in values across different subduction settings online material the location and spatial information for elliptical regions of aftershock zones

foreshock occurrence before large earthquakes rates of foreshock occurrence involving shallow m 6 and m 7 mainshocks and m 5 foreshocks were measured in two worldwide catalogs over 20 year intervals the overall rates observed are similar to ones measured in previous worldwide and regional studies when they are normalized for the ranges of magnitude difference they each span the observed worldwide rates were compared to a generic model of earthquake clustering based on patterns of small and moderate aftershocks in california the aftershock model was extended to the case of moderate foreshocks preceding large mainshocks overall the observed worldwide foreshock rates exceed the extended california generic model by a factor of 2 significant differences in foreshock rate were found among subsets of earthquakes defined by their focal mechanism and tectonic region with the rate before thrust events higher and the rate before strike slip events lower than the worldwide average among the thrust events a large majority composed of events located in shallow subduction zones had a high foreshock rate while a minority located in continental thrust belts had a low rate these differences may explain why previous surveys have found low foreshock rates among thrust events in california especially southern california while the worldwide observations suggests the opposite california lacking an active subduction zone in most of its territory and including a region of mountain building thrusts in the south reflects the low rate apparently typical for continental thrusts while the worldwide observations dominated by shallow subduction zone events are foreshock rich if this is so then the california generic model may significantly underestimate the conditional probability for a very large m 8 earthquake following a potential m 7 foreshock in cascadia the magnitude differences among the identified foreshock mainshock pairs in the harvard catalog are consistent with a uniform distribution over the range of observation

mineralogy of the ganges and brahmaputra rivers implications for river switching and late quaternary climate change late quaternary sediments of the bengal basin contain a history of river switching and climate change as revealed from sand and clay size mineralogy of boreholes and modern riverbed grabs epidote to garnet ratios e g in sand fraction sediments are diagnostic of source with high 1 e g indicating brahmaputra provenance and low 1 e g indicating ganges provenance in the clay fraction of surficial sediments smectite is diagnostic with high values 39 in the ganges and low values 3 in the brahmaputra in contrast the brahmaputra contains more kaolinite 29 vs 18 more illite 63 vs 41 and more chlorite 3 vs 1 than the ganges analysis of mineralogic and stratigraphic data indicates that the two rivers have changed position several times during the holocene extended periods of mixed river inputs appear to be isolated to the early holocene suggesting rapidly migrating braided channels during sea level lowstand tectonically driven accommodation in the sylhet basin may have contributed to the favored easterly course of the brahmaputra during much of the holocene relative abundances of illite and chlorite ic vs smectite and kaolinite sk record varying degrees of physical and chemical weathering respectively high ic values in early post glacial deposits suggest a dominance of physical weathering at that time however a general increase in sk concentrations throughout the holocene appears to reflect enhanced chemical weathering under increasingly warmer and more humid conditions notably a peak in sk concentrations that corresponds to an early holocene warm period 10 7 ka suggests that weathering patterns in the catchment respond quickly to climatic shifts

recycling of graphite during himalayan erosion a geological stabilization of carbon in the crust at geological time scales the role of continental erosion in the organic carbon oc cycle is determined by the balance between recent oc burial and petrogenic oc oxidation evaluating its net effect on the concentration of carbon dioxide and dioxygen in the atmosphere requires the fate of petrogenic oc to be assessed here we report a multiscale nanometer to micrometer structural characterization of petrogenic oc in the himalayan system we show that graphitic carbon is preserved and buried in marine sediments while the less graphitized forms are oxidized during fluvial transport radiocarbon dating indicates that 30 to 50 of the carbon initially present in the himalayan rocks is conserved during the erosion cycle graphitization during metamorphism thus stabilizes carbon in the crust over geological time scales

adaptive daily forecasting of seismic aftershock hazard abstract seismic aftershock hazard analysis is one of the first steps toward establishing an integrated risk based decision making support framework for emergency management in the event of an ongoing aftershock sequence this work focuses on providing adaptive daily forecasts of the mean daily rate of exceeding various spectral acceleration values the aftershock hazard two well established earthquake occurrence models suitable for daily seismicity forecasts associated with the evolution of an aftershock sequence namely the modified omori s aftershock model mo and the epidemic type aftershock sequence etas are adopted an adaptive and evolutionary mo based aftershock occurrence model with distinct spatial and temporal components is proposed in this model the parameters deciding the temporal decay are updated based on the data provided by the ongoing aftershock sequence this model adopts an evolutionary spatial seismicity pattern loosely based on spatial clustering of aftershock events in the sequence bayesian updating is also employed to provide sequence based parameter estimates for a given ground motion prediction model daily forecasts of the mean rate of exceedance of various spectral acceleration levels are calculated based on alternative occurrence models and the updated ground motion prediction relation as a numerical example daily forecasts of the aftershock hazard curve are obtained for the l aquila aftershock sequence based on the mo based and etas occurrence models and an updated version of the sabetta and pugliese 1996 ground motion prediction model these daily hazard forecasts are then compared with the observed daily rates of exceeding various spectral acceleration thresholds

bath s law derived from the gutenberg richter law and from aftershock properties 1 the empirical bath s law states that the average difference in magnitude between a mainshock and its largest aftershock is 1 2 regardless of the mainshock magnitude following vere jones 1969 and console et al 2003 we show that the origin of bath s law is to be found in the selection procedure used to define mainshocks and aftershocks rather than in any difference in the mechanisms controlling the magnitude of the mainshock and of the aftershocks we use the etas model of seismicity which provides a more realistic model of aftershocks based on i a universal gutenberg richter gr law for all earthquakes and on ii the increase of the number of aftershocks with the mainshock magnitude using numerical simulations of the etas model we show that this model is in good agreement with bath s law in a certain range of the model parameters

brahmaputra river assam india physiography basin denudation and channel aggradation the brahmaputra river in assam india characterized by high seasonal variability in flow sediment transport and channel configuration experienced a secular period of aggradation from 1971 to 1979 the suspended load budget indicates an overall aggradation of the 607 km assam reach of the brahmaputra by about 16 cm during that period with about 70 of the suspended sediment inflow into the reach being retained in the channel expressed as a percentage of the change in storage for the different reaches computed errors due to sampling variability in sediment discharge generally lie within about 5 15 and do not appear to be large enough to affect the conclusions drawn from the suspended load budget for a 145 km reach of the brahmaputra an alternative method based on measurement of channel cross sections suggests 21 cm of aggradation somewhat more than estimated by the suspended load budget based on the suspended load carried by trans himalayan rivers the present rate of denudation of the eastern himalayas is estimated to be 73 157 cm 103 years the average rate for the last 2 3 million years estimated from the volume of alluvial fill in the brahmaputra valley in assam the sediment yield of the himalayan rivers and assuming a total yield to deposition ratio of 1 4 present study is 3 cm 103 years the current high rate of denudation of the himalayas may be attributed mainly to the rapid uplift of the mountain system recent earthquake activity and high susceptibility of geologic formations to erosion by running water coupled with the effectiveness of the monsoon rainfall regime

higher erosion rates in the himalaya geochemical constraints on riverine fluxes the modern erosion rate of continental scale mountains is difficult to estimate and is usually based on measurement of the suspended load flux of rivers combined with assumptions about river bedload transport and sedimentation in flood plains these two parameters are very difficult to measure directly in continental scale basins in this paper we examine the chemical composition of the suspended load bedload and dissolved load of the ganga and brahmaputra rivers and compare them with the average composition of himalayan source rocks a mass balance equation of erosion fluxes shows that a si rich component is needed in addition to suspended and dissolved load fluxes to account for the composition of the source rock it corresponds to bedload sediment and flood plain deposits which are enriched in quartz by mineral sorting during transport the combined budget of si al and fe in the river system allows us to estimate this si rich flux by this method the total himalayan erosion is estimated to be twice the measured flux of suspended load the comparison between the brahmaputra and the ganga shows that the eastern himalaya has a higher erosion rate 2 9 mm yr than the western himalaya 2 1 mm yr this is likely the result of the higher runoff in the brahmaputra basin the intensity of the monsoon acts as a first order control of the erosion rate in the range

rapid and widespread dispersal of flood sediment on the northern california margin the dispersal of flood sediment from small river systems is a poorly studied yet potentially important aspect of active continental margin sedimentation in january 1995 during a flood with a 30 yr return period the eel river northern california delivered an estimated 25 3 106 t metric tons of fine grained 62 m sediment to the ocean the flood formed a distinct layer on the sea bed that was centered on the 70 m isobath extended for 30 km along shelf and 8 km across shelf and was as thick as 8 5 cm but contained only 6 106 t of sediment thus 75 of the flood derived sediment did not form a recognizable deposit but was instead rapidly and widely dispersed over the continental margin stratigraphic models of and compilations of sediment flux to active continental margins need to take the dispersive nature of small river systems into account

a common origin for aftershocks foreshocks and multiplets we demonstrate that the statistics of earthquake data in the global cen troid moment tensor cmt and national earthquake information center neic catalogs and local california council of the national seismic system cnss catalog are consistent with the idea that a single physical triggering mechanism is responsible for the occurrence of aftershocks foreshocks and multiplets specifically we test the hypothesis that tectonic earthquakes usually show clustering only as a result of an initial earthquake triggering subsequent ones and that the magnitude of each trig gered earthquake is entirely independent of the magnitude of the triggering earth quake therefore a certain percentage of the time as determined by the gutenberg richter magnitude frequency relationship an earthquake should by chance be larger than or comparable in size to the earthquake that triggered it this hypothesis predicts that the number of times foreshocks or multiplets are observed should be a fixed fraction of the number of aftershock observations we find that this is indeed the case in the global cmt and neic catalogs the average ratios between foreshock aftershock and multiplet rates are consistent with what would be predicted by the gutenberg richter relationship with b 1 we give special attention to the solomon islands where it has been claimed that unique fault structures lead to unusually high numbers of multiplets we use monte carlo trials to demonstrate that the solomon islands multiplets may be explained simply by a high regional aftershock rate and earthquake density we also verify our foreshock results from the more complete recordings of small earthquakes available in the california catalog and find that foreshock rates for a wide range of foreshock and mainshock magnitudes can be projected from aftershock rates using the gutenberg richter relationship with b 1 and the relationship that the number of earthquakes triggered varies with triggering earthquake magnitude m as c10m where c is a productivity constant and is equal to 1 finally we test an alternative model that proposes that foreshocks do not trigger their mainshocks but are instead triggered by the mainshock nucleation phase in this model the nucleation phase varies with mainshock magnitude so we would expect mainshock magnitude to be correlated with the magnitude number or spatial extent of the foreshocks we find no evidence for any of these correlations

relationships between mineral surfaces and organic carbon concentrations in soils and sediments abstract relationships between mineral specific surface area and organic carbon oc concentration are examined for sediments and soil a horizons from throughout the world i found published elsewhere that continental shelf sediments from many different regions exhibit downcore loss of oc to a refractory background level which shows a consistent relationship with mineral surface area slope 0 86 mg m 2 oc this trend is equivalent to a monolayer of organic matter over all surfaces and is termed the monolayer equivalent me level sediments and soils from other environments are compared to this empirically derived relationship several continental slope areas show extension of this relationship to considerable depth marked excesses of oc above this trend which persist downcore were found in sediments with high carbonate mineral content or slope sediments with low dissolved oxygen concentrations in the overlying water column about half of the soils examined also adhered to this relationship while soils with high carbonate content low ph or poor drainage showed oc concentrations higher than the me level oc concentrations below the me level are found in deltaic regions and areas with low organic matter delivery such as the deep sea or arid soils the nature of mineral surfaces was examined using n2 adsorption desorption isotherms and most surface area was found to be present as pores with

major ion chemistry of the ganga brahmaputra river system weathering processes and fluxes to the bay of bengal the ganga brahmaputra one of the world s largest river systems is first in terms of sediment transport and fourth in terms of water discharge a detailed and systematic study of the major ion chemistry of these rivers and their tributaries as well as the clay mineral composition of the bed sediments has been conducted the chemistry of the highland rivers upper reaches of the ganga the yamuna the brahmaputra the gandak and the ghaghra are all dominated by carbonate weathering ca mg and hco3 account for about 80 of the cations and anions in the lowland rivers the chambal the betwa and the ken hco3 excess over ca mg and a relatively high contribution of na k to the total cations indicate that silicate weathering and or contributions from alkaline saline soils and groundwaters could be important sources of major ions to these waters the chemistry of the ganga and the yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions illite is the dominant clay mineral about 80 in the bedload sediments of the highland rivers kaolinite and chlorite together constitute the remaining 20 of the clays in the chambal betwa and ken smectite accounts for about 80 of the clays this difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins the highland rivers weather acidic rocks whereas the others flow initially through basic effusives the ganga brahmaputra river system transports about 130 million tons of dissolved salts to the bay of bengal which is nearly 3 of the global river flux to the oceans the chemical denudation rates for the ganga and the brahmaputra basins are about 72 and 105 tons km yr 1 respectively which are factors of 2 to 3 higher than the global average the high denudation rate particularly in the brahmaputra is attributable to high relief and heavy rainfall

comparing foreshock characteristics and foreshock forecasting in observed and simulated earthquake catalogs in this paper we compare the empirical results regarding foreshocks obtained from the japan data with results for synthetic catalogs in order to clarify whether or not the corresponding results are consistent with the description of the seismicity by a superposition of background activity and epidemic type aftershock sequence etas models this question is important because it is still controversially discussed whether the nucleation process of large earthquakes is driven by seismically cascading etas type or by aseismic accelerating processes to explore the foreshock characteristics we first applied the same clustering algorithms to real and synthetic catalogs and analyzed the temporal spatial and magnitude distributions of the selected foreshocks most properties are qualitatively the same in the real data and in synthetic catalogs however we find some quantitative differences particularly in the temporal acceleration spatial convergence and magnitude dependence which also depend on the assumed synthetic catalogs furthermore we calculated forecast scores based on a single link cluster algorithm which could be appropriate for real time applications we find that the japan meteorological agency catalog yields higher scores than all synthetic catalogs and that the etas models having the same magnitude sequence as the original catalog performs better more close to the reality than etas models with randomly picked magnitudes we also find that the etas model that takes account of the triggering effect by small earthquakes below threshold magnitude performs more closely to the reality

tracing the distribution of erosion in the brahmaputra watershed from isotopic compositions of stream sediments bank sediments and suspended loads of the brahmaputra river and its important tributaries were collected from the himalayan front to bangladesh along with most of the important tributaries chemical and isotopic compositions of the sediments are used to trace sediment provenance and to understand erosion patterns in the basin overall isotopic compositions range from 0 7053 to 0 8250 for sr and nd from 20 5 to 6 9 this large range derives from the variable proportions of sediments from himalayan formations with high sr isotopic ratios and low nd and transhimalayan plutonic belt with lower sr isotopic ratios and higher nd the latter are exposed to erosion in the tsangpo and in the eastern tributary drainages overall erosion of the himalayan rocks is dominant representing ca 70 of the detrital influx compositions of the brahmaputra main channel are rather stable between 0 7177 and 0 7284 for sr and between 14 4 and 12 5 for nd throughout its course in the plain from the siang tsangpo at the foot of the himalayan range down to the delta this stability despite the input of large himalayan rivers suggests that the siang tsangpo river represents the major source of sediment to the whole brahmaputra geochemical budget implies that erosion of the namche barwa zone represents about 45 of the total flux at its outflow before confluence with the ganga from only 20 of the mountain area higher erosion rates in the eastern syntaxis compared to the other himalayan ranges is related to the rapid exhumation rates of this region possibly triggered by higher precipitation over the far eastern himalaya and the high incision potential of the tsangpo river due to its very high water discharge

the shape topography and geology of tempel 1 from deep impact observations deep impact images of the nucleus of comet tempel 1 reveal pervasive layering possible impact craters flows with smooth upper surfaces and erosional stripping of material there are at least 3 layers 50 200 m thick that appear to extend deep into the nucleus and several layers 1 20 m thick that parallel the surface and are being eroded laterally circular depressions show geographical variation in their forms and suggest differences in erosion rates or style over scales 1 km the stratigraphic arrangement of these features suggests that the comet experienced substantial periods of little erosion smooth surfaces trending downslope suggest some form of eruption of materials from this highly porous object the deep impact images show that the nucleus of tempel 1 cannot be modeled simply as either an onion layer or rubble pile structure

molecular and isotopic records of c4 grassland expansion in the late miocene abstract siwalik paleosol and bengal fan sediment samples were analyzed for the abundance and isotopic composition ofn alkanes in order to test for molecular evidence of the expansion of c4 grasslands on the indian subcontinent the carbon isotopic compositions of high molecular weight alkanes in both the ancient soils and sediments record a shift from low 13c values ca 30 to higher values ca 22 prior to 6 ma this shift is similar in magnitude to that recorded by paleosol carbonate and fossil teeth and is consistent with a relatively rapid transition from dominantly c3 vegetation to an ecosystem dominated by c4 plants typical of semi arid grasslands the n alkane values from our paleosol samples indicate that the isotopic change began as early as 9 ma reflecting either a growing contribution of c4 plants to a dominantly c3 biomass or a decrease in water availability to c3 plants molecular and isotopic analyses of other compounds including n alcohols and low molecular weightn alkanes indicate paleosol organic matter contains contributions from a mixture of sources including vascular plants algae and or cyanobacteria and microorganisms a range of inputs is likewise reflected in the isotopic composition of the total organic carbon from these samples in addition then alkanes from two samples show little evidence for pedegenic inputs and we suggest the compounds were derived instead from the paleosol s parent materials we suggest the record of vegetation in ancient terrestrial ecosystems is better reconstructed using isotopic signatures of molecular markers rather than bulk organic carbon this approach provides a means of expanding the spatial and temporal records of c4 plant biomass which will help to resolve possible tectonic climatic or biological controls on the rise of this important component of the terrestrial biosphere

statistical features of foreshocks in comparison with other earthquake clusters summary when earthquakes occur in a cluster the probability that they will be foreshocks of a forthcoming significantly larger earthquake appears dependent on the magnitude differences origin time spans and distances between several of the earliest events in a cluster the earthquake catalogue of the japan meteorological agency jma 1926 91 mj 2 4 is decomposed into numbers of clusters in time and space to compare statistical features of foreshocks with those of swarms and main shockaftershock sequences since the number of foreshocks in individual earthquake clusters is usually small two types of data stacking are considered first we consider the spatial and temporal distribution of events relative to the location and time of the coming main shock for the foreshocks a relative doughnut shaped pattern which converges in time to the main shock s epicentre is seen while this pattern is weak for swarms next we consider the temporal spatial and magnitude distributions of events relative to the time location and magnitude of earlier events in every sequence then a statistical discrimination of foreshocks from earthquakes of other types of clusters is explored the search for significant trends of relative frequency of foreshocks in comparison with other cluster types revealed the following features of foreshocks 1 their relative frequency is high when the inter event time span is less than several days but the maximum is attained at about several hours span 2 their relative frequency is high at short distances between epicentres especially within 10 km and then decreases as the distance gets larger and 3 their relative frequency increases as the magnitude increases among the earliest shocks in a cluster the stability of the results is confirmed by finding similar trends using different cluster identification methods and different threshold magnitudes further microearthquakes in the japan university network data file 1983 87 m 2 2 and moderate to large earthquakes in the international seismological centre world catalogue isc 1979 90 mh 2 5 are examined to see some effects of the magnitude thresholds of these catalogues similar features to those obtained in the jma catalogue are also found for these catalogues

foreshock rates from aftershock abundance the question whether foreshocks behave like mainshocks that happen to have larger aftershocks is important for the understanding of earthquake nucleation and the modeling of earthquake clustering many models including the short term earthquake probability step model for forecasting short term earthquake hazard in california and the epidemic type aftershock sequence etas model for the description of earthquake clustering imply that all earthquakes of magnitude m including foreshocks can trigger earthquakes according to a magnitude dependent triggering ability 10 m the magnitudes of the triggered earthquakes are proportional to 10 bm according to the gutenberg richter relation for the magnitude frequency distribution and therefore can be larger than the magnitude of the initiating event however numerous studies observe a lower foreshock occurrence than predicted from aftershock models in this article we show that for homogeneous earthquake catalogs and a consistent definition of foreshocks and aftershocks foreshock rates can be predicted from aftershock characteristics for southern california the probability that the initiating event of an earthquake cluster in the magnitude range 2 0 4 5 is followed by at least one larger event within one day is around 4 this agrees well with corresponding data from the global centroid moment tensor cmt catalog where the probability that the initiating earthquake of a cluster is followed by at least one larger event within 30 days is around 3 these foreshock rates are significantly lower than previously reported and we discuss possible reasons for this

loading and fate of particulate organic carbon from the himalaya to the ganga brahmaputra delta abstract we use the evolution of river sediment characteristics and sedimentary corg from the himalayan range to the delta to study the transport of corg in the ganga brahmaputra system and especially its fate during floodplain transit a detailed characterisation of both mineral and organic particles for a sampling set of river sediments allows taking into account the sediment heterogeneity characteristic of such large rivers we study the relationships between sediment characteristics mineralogy grain size specific area and corg content in order to evaluate the controls on corg loading contributions of c3 and c4 plants are estimated from corg stable isotopic composition 13corg we use the evolution of 13corg values from the himalayan range to the delta in order to study the fate of corg during floodplain transit ganga and brahmaputra sediments define two distinct linear relations with specific area in spite of 4 5 times higher specific area ganga sediments have similar corg content grain size and mineralogy as brahmaputra sediments indicating that specific area does not exert a primary control on corg loading the general correlation between the total corg content and al si ratio indicates that corg loading is mainly related to 1 segregation of organic particles under hydrodynamic forces in the river and 2 the ability of mineral particles to form organo mineral aggregates bed and suspended sediments have distinct 13corg values in bed sediments 13corg values are compatible with a dominant proportion of fossil corg derived from himalayan rocks erosion suspended sediments from himalayan tributaries at the outflow of the range have low 13corg values 24 8 average indicating a dominant proportion of c3 plant inputs in the brahmaputra basin 13corg values of suspended sediments are constant along the river course in the plain on the contrary suspended sediments of the ganga in bangladesh have higher 13corg values 22 4 to 20 0 consistent with a significant contribution of c4 plant derived from the floodplain our data indicate that during the plain transit more than 50 of the recent biogenic corg coming from the himalaya is oxidised and replaced by floodplain corg this renewal process likely occurs during successive deposition erosion cycles and river course avulsions in the plain

late quaternary climatic variability in the central ganga plain a multi proxy record from karela jheel lake abstract a multi proxy study involving phytoliths diatoms thecamoebians and sponge spicules was carried out on a trench profile 260 cm deep from karela lake in the central ganga plain to reconstruct climatic variations since ca 17 000 cal bp the testate amoebae record indicate spells of winter monsoon between ca 17 000 cal bp and 13 700 cal bp increased diversity of diatoms testate amoebae and sponge spicules in addition to low humidity aridity index iph values suggest strengthened monsoon inducing the expansion of lake margin and high primary productivity during ca 13 700 to 4300 cal bp further between ca 4300 and 2900 cal bp higher iph values and related responses of other studied proxies show a stressed lake ecosystem since ca 2900 cal bp area of the lake was reduced responding to low intensity of the indian summer monsoon anthropogenic activities may also have played a role in the lake shrinking at least during some parts of this duration

the largest expected earthquake magnitudes in japan the statistical perspective abstract earthquake catalogs are probably the most informative data source about spatiotemporal seismicity evolution the catalog quality in one of the most active seismogenic zones in the world japan is excellent although changes in quality arising for example from an evolving network are clearly present here we seek the best estimate for the largest expected earthquake in a given future time interval from a combination of historic and instrumental earthquake catalogs we extend the technique introduced by zoller et al 2013 to estimate the maximum magnitude in a time window of length t f for earthquake catalogs with varying level of completeness in particular we consider the case in which two types of catalogs are available a historic catalog and an instrumental catalog this leads to competing interests with respect to the estimation of the two parameters from the gutenberg richter law the b value and the event rate above a given lower magnitude threshold the a value the b value is estimated most precisely from the frequently occurring small earthquakes however the tendency of small events to cluster in aftershocks swarms etc violates the assumption of a poisson process that is used for the estimation of we suggest addressing conflict by estimating b solely from instrumental seismicity and using large magnitude events from historic catalogs for the earthquake rate estimation applying the method to japan there is a probability of about 20 that the maximum expected magnitude during any future time interval of length t f 30 years is m 9 0 studies of different subregions in japan indicates high probabilities for m 8 earthquakes along the tohoku arc and relatively low probabilities in the tokai tonankai and nankai region finally for scenarios related to long time horizons and high confidence levels the maximum expected magnitude will be around 10

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

estimating the etas model from an early aftershock sequence forecasting aftershock probabilities as early as possible after a main shock is required to mitigate seismic risks in the disaster area in general aftershock activity can be complex including secondary aftershocks or even triggering larger earthquakes however this early forecasting implementation has been difficult because numerous aftershocks are unobserved immediately after the main shock due to dense overlapping of seismic waves here we propose a method for estimating parameters of the epidemic type aftershock sequence etas model from incompletely observed aftershocks shortly after the main shock by modeling an empirical feature of data deficiency such an etas model can effectively forecast the following aftershock occurrences for example the etas model estimated from the first 24 h data after the main shock can well forecast secondary aftershocks after strong aftershocks this method can be useful in early and unbiased assessment of the aftershock hazard

deep impact excavating comet tempel 1 deep impact collided with comet tempel 1 excavating a crater controlled by gravity the comet s outer layer is composed of 1 to 100 micrometer fine particles with negligible strength 1000 kelvins a large increase in organic material occurred during and after the event with smaller changes in carbon dioxide relative to water on approach the spacecraft observed frequent natural outbursts a mean radius of 3 0 0 1 kilometers smooth and rough terrain scarps and impact craters a thermal map indicates a surface in equilibrium with sunlight

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

multi proxy evidence for compositional change of organic matter in the largest tropical peninsular river basin of india summary the distribution and compositional changes of organic matter om within the godavari river system is increasingly influenced by reduced monsoon rainfall and an increased number of damming to track these changes stable isotopes of organic carbon and concentrations of lignin phenols were analyzed in total suspended matter tsm sediments agriculture soils and plants from godavari basin the results indicated that the upper tributaries drained heavier carbon 13 c org 20 4 2 2 than the lower tributaries 13 c org 25 4 1 5 owing to the regional vegetation in the upper to lower basins om originating from algae near dam impoundments was incorporated into tsm and sediment due to extreme drought condition the organic carbon oc content was higher in tsm and in the sediment of the region after the middle reach dam sriram sagar than before 2 2 1 6 vs 1 0 0 1 oc and 2 1 2 3 vs 0 6 0 2 oc respectively the lignin yield 8 was lower in tsm and in the sediment after the dam impoundment than before 0 37 vs 1 94 mg 100 mg oc and 2 9 1 1 vs 5 4 2 3 mg 100 mg oc respectively due to an increased contribution of lignin free oc from algae and degraded soil less rainfall and dam impoundments enhanced the fraction of labile om from freshwater algae and an estuarine phytoplankton bloom in the study year our study is the first to document lignin fluxes from an indian monsoonal river godavari the flux of lignin phenols of 7 26 10 9 g yr 1 is much lower than those of most world rivers except the rivers from polar arctic

major and trace element geochemistry of bay of bengal sediments implications to provenances and their controlling factors major and trace elements of sediments from a 13 m long piston core sk187 pc33 from the western bay of bengal have been investigated in this study to infer about the changes in provenances and related controlling factors during the last glacial interglacial period factor analysis of these geochemical dataset ascertains dominant role of riverine supply of sediments in regulating the geochemistry of sk187 pc33 sediments the al normalized major k and ti and trace elemental cu and cr ratios of these marine sediments fall within the ranges observed for their major provenances viz ganga brahmaputra and the godavari krishna gk rivers and depth profiles of these ratios showed significant variations with synchronous excursion at around the last glacial maxima lgm implying a change in their provenances with relatively reduced himalayan contribution during this climatic event relatively higher cia and ti ca ratios with lower k al ratios of these sediments during the holocene hint intense chemical weathering in the river basins in response to strengthened monsoon during this period inverse model calculation of al normalized elemental ratios of the sediments estimated an average sediment contribution of 66 13 and 34 13 from the himalayan and the peninsular indian rivers to the core site respectively consistent with the depth profiles of elemental ratios the estimated sediment contributions from the himalayan rivers are observed to decrease by 20 from the himalayan rivers particularly that of the ganga to the studied location during the lgm lowering of sediment supply from the himalaya ganga during the lgm is due to weakening of south west monsoon and reduction in available exposure area for weathering due to extent of glacier cover outcomes of this study underscore the strong linkage between erosion and climate

statistics between mainshocks and foreshocks in italy and southern california 1 the most used and accepted models for daily forecasts are based on short term space and time earthquake clustering for occurrence rates and on the gutenberg richter law for the frequency magnitude these models have been demonstrated to produce reliable prospective space time magnitude forecasts during an aftershock sequence but their skill in forecasting mainshocks is still under discussion this paper studies the foreshock statistics of the italian and californian seismicity in two ways i we compare the foreshock activity observed in real seismic catalogs and in synthetic catalogs derived from a pure epidemic type aftershock sequence etas model ii we analyze the triggering capability of earthquakes using different etas parameterizations in order to check whether large events are triggered in the same way as regular earthquakes the results indicate that the foreshock activity observed in the real catalogs is compatible with what is expected by the etas model moreover we find that the empirical foreshock rates have an intrinsic variability due to limited sampling that may explain most of the differences found so far in different seismic catalogs

watershed control on the carbon loading of marine sedimentary particles abstract previous investigations of the factors governing organic carbon burial on continental margins have pointed toward the important apparently protective association of carbon with mineral particles these studies have also revealed dramatic transformations of carbon particle relationships at the land sea interface riverine particles in some settings lose a large portion of their loads of sorbed terrestrial carbon upon discharge to the ocean and gradually reload to similar levels with marine carbon the eel river in northern california and the adjacent continental shelf were selected as an ideal system to investigate the rates of these processes the river is episodically subject to large floods and the shelf stratigraphy preserves a record of the resultant large pulses of sediment and carbon input to the marine environment carbon isotopic carbon to nitrogen and carbon to surface area ratios of particles in flood deposits were expected to reflect the rapid unloading of terrestrial carbon from discharged particles whereas nonflood sediments that have accumulated at slower rates on the shelf were expected to carry higher loads of marine carbon our results indicate however that particles on the eel shelf have retained their loads of terrigenous carbon and that a significant portion of the particle sorbed carbon buried on the shelf is kerogen derived from the mesozoic tertiary franciscan complex we hypothesize that rates of uplift and mass wasting in the eel watershed and rates of particle delivery to and burial on the continental shelf are so rapid that kerogen is not completely oxidized and is recycled instead the loading of carbon on clay sized particles delivered to the shelf moreover is dependent on river discharge and may reflect the relative importance of different mass wasting processes during precipitation events of varying intensity the eel river system is likely to be representative of other small mountainous rivers and indicates that processes on land may play an important role in governing the amount and character of carbon being buried on the continental margins

differences between spontaneous and triggered earthquakes their influences on foreshock probabilities 1 in this study we investigate the foreshock probabilities calculated from earthquake catalogs from japan southern california and new zealand unlike conventional studies on foreshocks we use a probability based declustering method to separate each catalog into stochastic versions of family trees such that each event is classified as either having been triggered by a preceding event or being a spontaneous event the probabilities are determined from parameters that provide the best fit of the real catalogue using a space time epidemic type aftershock sequence etas model the model assumes that background and triggered earthquakes have the same magnitude dependent triggering capability a foreshock here is defined as a spontaneous event that has one or more larger descendants and a triggered foreshock is a triggered event that has one or more larger descendants the proportion of foreshocks in spontaneous events of each catalog is found to be lower than the proportion of triggered foreshocks in triggered events one possibility is that this is due to different triggering productivity in spontaneous versus triggered events i e a triggered event triggers more children than a spontaneous events of the same magnitude however further analysis on simulated data shows that such difference might be caused by the events triggered by smaller events below the magnitude threshold of the catalog even if the physical interpretation is unclear a clustering model where spontaneous events and triggered events have different triggering behaviors can be used to assess the risk of foreshocks and to avoid overpredicting

c and o isotope compositions of modern fresh water mollusc shells and river waters from the himalaya and ganga plain the aim of this paper is to unfold the relationship between the o and c isotope compositions of modern fresh water mollusc shells and water in order to refine the basis of interpretation for paleoenvironnemental reconstruction in the sub himalayan river basins large number of mollusc shells and associated host water from both running water and closed body of water were analysed including intra shell variability in a few cases the o isotopic compositions of river waters in the himalaya and ganga plain have a large range from 18 in the north of the high range up to 8 to 4 in the ganga plain 18o of rivers are also seasonally variable especially in foothills rivers whereas the seasonal contrast is smoothed out for the main himalayan rivers having large catchments o isotopic compositions of bulk shells aragonite vary between 15 and 5 average 18oara values are consistent with precipitation at equilibrium with host waters at a temperature range of 20 25 c suggesting that shell growth may be favoured during non monsoon conditions shells collected along the main himalayan rivers have 18o values uniformly distributed within 11 and 6 reflecting the minimal seasonal contrast shown by these rivers in contrast o isotopic compositions of shells from foothills rivers vary only by 4 this shows that depending on the type of river where the molluscs grow the information in term of 18o amplitude will be different for identical climatic conditions in closed or pond water bodies significant enrichment in 18o due to evaporation is observed the c isotopic compositions of river dissolved inorganic carbon dic decrease downstream from 0 to 10 reflecting input of soil derived alkalinity and plant productivity in the river 13c of shells are systematically lower than compositions calculated for equilibrium with river dic indicating that in addition to dic a significant fraction of carbon is derived from metabolic sources intra shell 13c are stable compared to the seasonal variability of dic suggesting that the pool of organic carbon changes throughout year

short term earthquake forecasting using early aftershock statistics abstract we present an alarm based earthquake forecast model that uses the early aftershock statistics east this model is based on the hypothesis that the time delay before the onset of the power law aftershock decay rate decreases as the level of stress and the seismogenic potential increase here we estimate this time delay from t g the time constant of the omori utsu law to isolate space time regions with a relative high level of stress the single local variable of our forecast model is the e a value the ratio between the long term and short term estimations of t g when and where the e a value exceeds a given threshold i e the c value is abnormally small an alarm is issued and an earthquake is expected to occur during the next time step retrospective tests show that the east model has better predictive power than a stationary reference model based on smoothed extrapolation of past seismicity the official prospective test for california started on 1 july 2009 in the testing center of the collaboratory for the study of earthquake predictability csep during the first nine months 44 m 4 earthquakes occurred in the testing area for this time period the east model has better predictive power than the reference model at a 1 level of significance because the east model has also a better predictive power than several time varying clustering models tested in csep at a 1 level of significance we suggest that our successful prospective results are not due only to the space time clustering of aftershocks

weathering processes in the ganges brahmaputra basin and the riverine alkalinity budget abstract we present river chemistry data for a network of rivers draining the western and central nepal himalaya our sampling locations cover the system from the sources of rivers in tibet to the gangetic plain water samples were collected throughout the year including the monsoon season for rivers in nepal and for the ganges and brahmaputra in bangladesh rivers draining the north himalaya are characterized by low discharge under a cold and arid climate main stream waters have 13 c dic near 0 and high so42 so42 hco3 ratios xso4 with values around 40 eq and high cl ca is the dominant cation ca2 cations 55 to 75 eq after correction of sodium by chloride dissolved sulfate is produced in waters from the tethian sedimentary series whereas chlorine is related to thermal waters dissolved sulfate is primarily derived from sulfide oxidation rather than evaporite dissolution 13 c dic values of up to 3 9 show that metamorphic co2 is an important weathering agent rivers of the north himalayan basins have about 50 of their alkalinity derived from carbonate dissolution 20 from biogenic activity and 30 from metamorphic co2 on the south flank of the himalaya rivers are more depleted in 13 c and have on average lower xso4 most rivers have 13 c dic and xso4 values compatible with a simple mixing between soil co2 and sulfate derived from sulfide oxidation during the monsoon discharge increases by a factor 20 but the total dissolved concentration is only slightly reduced xso4 and 13 c decrease while ca cations increases implying enhanced dissolution of pedogenic calcite as a whole the g b riverine flux of alkalinity derived from silicate weathering is around 2 7 1011 mol year modest at the global scale sulphuric acid controls 20 30 of the weathering reaction in the brahmaputra and 6 to 9 in the ganges na and k balance 60 to 65 of the silicate derived alkalinity flux and the long term co2 consumption by ganges and brahmaputra is near 6 4 1010 mol year the flux of metamorphic co2 converted to alkalinity via weathering reactions is ca 1 1010 mol year

organic matter preservation on continental slopes importance of mineralogy and surface area abstract theoretical considerations calculations and data reported by keil et al 1994a were used to assess the recent hypotheses that mineral surface roughness controls the specific surface area of continental margin sediments and that the matrix linked organic carbon content of continental margin sediments occurs as a monolayer or monolayer equivalent coating of organic compounds on the surfaces of detrital minerals and other detrital nonorganic grains mayer 1994 results of our analysis indicate that it is not the surface roughness of the terrigenous detrital framework grains that controls the specific surface area of most continental margin sediments even in the sand and silt fractions but rather the presence of nonspherical high surface area to volume particles primarily clays but also oxy hydroxides and ultra structured nonorganic bioclasts such as diatom frustules analysis of the mineralogy organic carbon content surface area and in situ microfabric of continental margin sediments off california in the mendocino and san luis obispo areas and off the state of washington indicate a strong correlation between the amount of matrix linked organic matter present and the suite of clay minerals data indicate that organic carbon appears to be preferentially sequestered in smectite rich sediments compared to those whose clay fractions are dominated by chlorite we suggest that this association is a function of differences in the site density and chemistry of the clays and differences in their flocculation behavior our data also indicate that organic carbon preservation on the three california transects all of which have a suboxic oxygen minimum zone that impinges on the sea floor is not significantly influenced by differences in bottom water oxygen concentration and carbon stable isotope data suggest no preferential preservation of continental organic matter over that of marine origin

fluxes and sources of particulate organic carbon in the ganga brahmaputra river system 1 sources and fluxes of particulate organic carbon oc in the ganga brahmaputra river system were estimated from 13c 12c ratios of bedrocks soils bank and suspended river sediments from a himalayan watershed narayani nepal and the bangladesh floodplain in the watershed of the narayani oc 13c values for bank and suspended sediments have similar values and narrow ranges with a mean of about 24 2 at the base of the himalayas on the bangladesh floodplain bank and suspended sediments are enriched in 13c 13c about 22 5 relative to those collected at the base of the himalayas the oc exported at the base of the himalayan range is estimated to include about 15 from the 13c enriched c4 biomass while the c4 contribution is about 25 of the oc exported by the ganga and brahmaputra a calculated total oc flux of 0 65 1012 molc yr 1 is exported to the ocean or trapped in the plain in sediments of the ganga and brahmaputra the clay size fraction is depleted in 13c 2 6 relative to the bulk sediment possible explanations are that either the organic matter associated with clays is largely inherited from the himalayan watersheds or and considered more likely the clays and coarser sediments sample different oc pools possibly with different ages the growth of c4 crops has dramatically increased since the mid twentieth century on the floodplain the oc budget of the actual ganga brahmaputra system is broadly comparable to that derived from the quaternary sediments of the bengal fan that represents about 10 of the global oc contribution to the continental margins

the provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the ganges brahmaputra rivers organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere in order to use sedimentary records to reconstruct past environmental conditions on the continents such as vegetation cover and type or precipitation intensity we need to understand the provenance of the organic signatures and how they are transferred and potentially modified by fluvial transport to the sedimentary reservoir in particular we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern day ganges and brahmaputra river complex one of the largest fluvial systems on earth the distribution of n alkanes and n alkanoic acids in ganges brahmaputra river sediments suggests that vascular plant inputs are consistently a significant component of the organic carbon pool molecular 13c measurements reveal that c3 vegetation inputs delivered by the himalayan rivers are partly degraded and replaced by mixed c3 c4 vegetation input in the floodplain the hydrogen isotopic composition of long chain c24 n alkanoic acids in combination with their stable c isotopic composition provides constraints on the isotopic composition of the environmental water used by higher plants within the drainage basin calculated compositions compare well with the depleted d isotopic ratios of the river water during the summer monsoon suggesting that h isotopic compositions of long chain alkanoic acids are a valuable proxy for the composition of summer monsoon moisture in the ganges brahmaputra basin detailed studies of the isotopic anatomy of modern river systems are critical for informed interpretation of marine sedimentary records in river influenced continental margins

development of a dust mantle on the surface of an insolated ice dust mixture results from the kosi 9 experiment astronomical observations indicate that formation and destruction of dust mantles on cometary nuclei may be the cause for erratic and systematic variations of cometary activity i e emission of dust a laboratory experiment kosi 9 has been performed to study the evolution of a dust mantle on top of a sublimating ice dust mixture in vacuum a sample consisting of water ice with a 10 by weight admixture of olivine grains has been insolated in three periods at variable intensities from 200 to 1900 w m2 both increasing surface temperature of the sample and decreasing gas and particle emissions indicated the formation of a dust mantle during the first period during the second insolation period after the gas flux had reached a critical value of a few 1021 water molecules m 2 s 1 avalanches of mantle material occurred on the inclined sample surface broke up the mantle locally and opened up a fresh icy surface enhanced ice and dust particle emission resumed for some time from these spots a large number of the emitted dust particles were of a fluffy aggregate structure i e they had large cross section to mass ratios compared to compact particles during the third period the critical gas flux was not reached and no enhanced dust and ice emission was observed a dry dust mantle of a few millimeters thickness developed during the course of the experiment consequences of these findings for cometary scenarios are discussed

immediate foreshocks time variation of the b value abstract we compare b values in the frequency magnitude law for the foreshocks and long term seismicity foreshocks are considered in two non overlapping time intervals preceding a main shock i last hours ii last days statistical analysis of the regional and global earthquake catalogs shows that in either of these intervals b value drops by a half compared to long term seismicity this extends the previous results by molchan and dmitrieva molchan g dmitrieva o 1990 dynamics of the magnitude frequency relation for foreshocks phys earth planet inter 61 99 112 who have found such a drop a few hours before a mainshock our results concern a statistical regularity not necessarily seen for each individual sequence of foreshocks

a generalized omori s law for earthquake aftershock decay 1 earthquake aftershock sequences have been found to approximately satisfy three empirical scaling relations i the gutenberg richter frequency magnitude scaling ii bath s law for the difference in the magnitude of a mainshock and its largest aftershock and iii the modified omori s law for the temporal decay of aftershock rates the three laws are incorporated to give a generalized omori s law for aftershock decay rates that depend on several parameters specific for each given seismogenic region it is shown that the characteristic time c first introduced in the modified omori s law is no longer a constant but scales with a lower magnitude cutoff and a mainshock magnitude the generalized omori s law is tested against earthquake catalogs for the aftershock sequences of the landers northridge hector mine and san simeon earthquakes

anomalous early aftershock decay rate of the 2004 mw6 0 parkfield california earthquake 1 we analyze the seismicity rate immediately after the 2004 mw6 0 parkfield california earthquake from near source seismograms by scrutinizing high frequency signals we can distinguish mainshock coda from early aftershocks occurring as soon as 30 s after the mainshock we find as expected that a significant fraction of aftershocks in the first few hours after the main shock are missing in the northern california seismic network catalog we observe a steady rate of aftershocks in the first 130 s followed by a power law decay of aftershock activity thus there appears to be a distinct early stage of aftershock activity that does not fit the omori s law with a constant p value a phenomenon that we refer to as early aftershock deficiency ead our observation suggests that mainshock rupture and aftershocks are distinct processes not described by a single omori s law several physical models of aftershocks can explain the ead

statistical physics approach to understanding the multiscale dynamics of earthquake fault systems 1 earthquakes and the faults upon which they occur interact over a wide range of spatial and temporal scales in addition many aspects of regional seismicity appear to be stochastic both in space and time however within this complexity there is considerable self organization we argue that the occurrence of earthquakes is a problem that can be attacked using the fundamentals of statistical physics concepts of statistical physics associated with phase changes and critical points have been successfully applied to a variety of cellular automata models examples include sandpile models forest fire models and particularly slider block models these models exhibit avalanche behavior very similar to observed seismicity a fundamental question is whether variations in seismicity can be used to successfully forecast the occurrence of earthquakes several attempts have been made to utilize precursory seismic activation and quiescence to make earthquake forecasts some of which show promise

bayesian analysis of extreme earthquake occurrences part i probabilistic hazard model bayesian probability theory in conjunction with the model of extremes is used to develop a bayesian distribution of extreme earthquake occurrences by assuming that earthquakes represent a poisson process with exponential distribution of magnitudes the bayesian distribution represents the probability that m max the largest earthquake expected to occur within a period of t years will exceed some specified magnitude m and may be computed from the relationship p m max m t 1 t t t 1 f m n where n and t represent updated posterior bayesian estimates of the number of earthquakes and the time period of observation respectively and f m is the bayesian distribution of magnitudes each updated from prior estimates of seismicity using historical observations of earthquake occurrences through the application of bayesian probability theory the above distribution contains two features that make it more powerful and reliable than the conventional extreme value distribution first it incorporates statistical uncertainty in the estimation of seismicity in addition to the inherent uncertainty associated with the random nature of earthquake occurrences second it provides a rigorous means of combining prior information on seismicity such as geologica data with available historical observations of earthquake occurrences the last feature represents a major step toward the ability of earthquake engineers to systematically use information from geologists and seismologists regarding the seismic potential of faults and small regions in the probabilistic assessment of seismic hazards and provides a means of periodically updating estimates of earthquake occurrence probabilities as new seismicity data become available

the largest aftershock how strong how far away how delayed 1 proposed in the 1950 s bath s law states that the largest aftershock has a magnitude that is typically 1 2 less than that of the mainshock thirty years of the global earthquake catalog allow us to extend bath s law in time space and focal mechanism on average reverse faults have a smaller magnitude and distance from the mainshock to largest aftershock than strike slip faults the distribution of the time intervals between mainshocks and their largest aftershocks obeys power law but with a somewhat faster rate of decay than for aftershocks in general this implies that the largest aftershocks are more likely to occur earlier rather than later in a given sequence of aftershocks

seismicity analysis through point process modeling a review the occurrence times of earthquakes can be considered to be a point process and suitable modeling of the conditional intensity function of a point process is useful for the investigation of various statistical features of seismic activity this manuscript summarizes likelihood based methods of analysis of point processes and reviews useful models for particular analyses of seismicity most of the analyses can be implemented by the computer programs published by the author and collaborators

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

waveform relocated earthquake catalog for southern california 1981 to june 2011 we determine a new relocated catalog hys catalog 2011 for southern california from 1981 through june 2011 about 75 3 of the hypocenters are calculated with absolute and differential travel time picks and 24 7 could be relocated only by using absolute travel time picks with 3d or 1d velocity models the total catalog consists of more than 502 000 earthquakes in the region extending from baja california in the south to coalinga and owens valley in the north the catalog consists of three m 7 1 m 7 2 and m 7 3 mainshocks their foreshocks and aftershocks and background seismicity caused by tectonic and other processes in the southern california crust hypocenters in the new relocated catalog exhibit tighter spatial clustering of seismicity than does the routinely generated catalog and the depth distribution is tighter and reflects the thickness of the seismogenic zone more accurately compared to the standard catalog the relocated hypocenters are more easily related to other data sets such as mapped late quaternary faults

statistical discrimination of foreshocks from other earthquake clusters summary when earthquake activity begins it may be a foreshock sequence to a larger earthquake a swarm or a simple main shock aftershock sequence this paper is concerned with the conditional probability that it will be foreshock activity of a later larger earthquake depending on the occurrence pattern of some early events in the sequence the earthquake catalogue of the japan meteorological agency 1926 1993 m 24 is decomposed into a large number of clusters in time and space in order to compare statistical features of foreshocks with those of swarms and aftershocks using such a data set ogata utsu katsura 1995 revealed some discriminating features of foreshocks relative to the other types of clusters for example the events closer proximity in time and space and a tendency towards chronologically increasing magnitudes which encouraged us to construct models which forecast the probability of the earthquakes being foreshocks specifically the probability is a function of the history of magnitude differences spans between origin times and distances between epicentres within a cluster for purposes of illustration the models were fitted to the early part of the data 1926 1975 and the validity of the forecasting procedure was checked on data from the later period 1976 1993 two procedures for evaluating the performance of the probability forecast are suggested furthermore for the case where only a single event is available i e either it is the first event in a cluster or an isolated event we also forecast the probability of the event being a foreshock as a function of its geographic location then the validity of the forecast is demonstrated in a similar manner finally making use of the multi element prediction formula we show that the forecasting performance is enhanced by the joint use of the information in the location of the first event and that in the subsequent interevent history in the cluster

δ13c of organic carbon in the bengal fan source evolution and transport of c3 and c4 plant carbon to marine sediments carbon isotopic measurements on organic carbon oc in sediment cores from the bengal fan odp leg 116 show a dramatic 10 increase beginning ca 7 ma ago and a rapid decrease after 0 9 ma these shifts reflect changes in the mixing ratio of terrigenous carbon derived from c3 and c4 plants the rapid increase in 13c of bengal fan oc at 7 ma shows that late miocene expansion of c4 plants already documented in the siwaliks was widespread over all the himalayan foreland after 7 ma relations of 13c with sedimentological parameters show that c4 plants dominate in the foreland whereas c3 plants remain abundant in the mountain range variations in the source of the sediments and of the oc appear to be sensitive to climate hydrologic conditions in the basin major changes in the isotopic composition of the carbon flux in one of the worlds largest river systems modify the isotopic budgets of both marine dissolved carbon and the sedimentary carbon mass

short term properties of earthquake catalogs and models of earthquake source i review the short term properties of earthquake catalogs in particular the time and size distributions and the completeness of the early part of aftershock sequences for strong shallow earthquakes i determine the parameters of the omori and gutenberg richter laws for aftershocks close in time to a mainshock aftershock sequences of large earthquakes in southern california 1952 kern county 1992 joshua tree landers big bear sequence 1994 northridge and 1999 hector mine recorded in the caltech catalog are analyzed to demonstrate that at the beginning of these series many small earthquakes are absent from the catalog the number of missing earthquakes increases with the magnitude range of a catalog and for some data sets exceeds the number of aftershocks close to a mainshock listed in a catalog comparing global earthquake catalogs harvard centroid moment tensor and preliminary determination of epicenter with local data sets indicates that the catalogs based on longer period waves miss many early aftershocks even when their magnitudes are well above the stated magnitude threshold such short term incompleteness may introduce significant biases to the statistical analysis of the seismicity pattern in particular for branching models of earthquake occurrence incorporating the omori law for such models the likelihood function strongly depends on close aftershocks i review the techniques to alleviate this problem analyzing the source rupture process of several recent large earthquakes suggests that rupture propagation is highly inhomogeneous in space time and focal mechanism these random variations in the rupture process can be viewed as an extension of the aftershock stochastic generating mechanism toward the origin time of a mainshock i review various models of the earthquake rupture process and suggest that fractal distributions of microevents in time space and focal mechanism constitute the development of an earthquake the final identification of an individual earthquake depends on both objective and subjective factors manuscript received 21 may 2003

fluidization and multiphase transport of particulate cometary material as an explanation of the smooth terrains and repetitive outbursts on 9p tempel 1 article history the deep impact mission discovered repetitive outbursts on comet 9p tempel 1 and the presence of several smooth terrains on its surface we present new measurements of the extent of the smooth terrains the slopes along their centerlines and the areas of their likely source regions our analysis of these features indicates that they are 0 3 m in size should become fully relaxed during the emplacement time explaining the smooth texture seen in the images in contrast the repetitive outbursts require a gas laden reservoir to have formed in the vicinity of the phase change boundary well below their preferred location we visualize the outbursts to be the result of either spouting or bubble transport to the surface where the release of gas is diurnally modulated by either thermal stresses or h2o sublimation back pressure the source region for the i2 smooth terrain is found to coincide with an h2o ice rich area and we propose that the process of elutriation i e the separation of different classes of particulates depending on their drag properties occurs in the fluidized material as it flows up to and through the surface in this way the material becomes enhanced in h2o crystals relative to siliceous and carbonaceous particulates

experimental studies of ice grain ejection by massive gas flow from ice and implications to comets triton and mars abstract this is an experimental study of ice grain ejection when trapped gases are released from water ice when ice is formed by adherence of water molecules at low temperatures it forms an amorphous structure with many pores where gas molecules can reside when further ice layers are formed the gases are trapped in the ice upon its warming up the ice structure changes releasing fractions of the trapped gas if they do not encounter obstacles they are released quiescently by dynamic percolation in a non dense ice a huge flux of ice grains emanates from the ice propelled by gas jets and covering its entire surface when the overlying ice is denser due to back migration of water vapor during its sublimation gas trying to escape from below cannot penetrate the dense ice and breaks it producing non circular craters and a chaotic terrain as observed experimentally and in close encounters with comets wild 2 tempel 1 and hartley 2 these experimental findings explain several observations of solar system bodies ice grain ejection from comets temple 1 and hartley 2 also explained are the dark jets observed on triton where their ejection speed suggests a deep source on mars dark streaks are observed in the southern pole in spring most likely by plumes carrying dark dust carried by winds and falling on the surface as found by us experimentally only frozen co 2 covered by water ice or mixed with it will work to form jets whereas pure frozen co 2 will sublimate quiescently

effect of human controlled hydrological regime on the source transport and flux of particulate organic carbon from the lower huanghe yellow river evaluating the role of fluvial transfer of terrestrial organic carbon oc and subsequent burial in the global carbon cycle requires the sources and fluxes of fluvial oc to be assessed which remains poorly constrained in the huanghe yellow river here we report the elemental stable isotopic and radiocarbon activity of particulate organic carbon poc sampled at the outlet of huanghe in 2012 2013 we show that the huanghe riverine poc can be explained by binary mixing of fossil pocfossil and non fossil pocnon fossil components the former may reach 40 of the total poc the huanghe pocnon fossil is mostly sourced from c3 plants with a mean residence time of c 2200 years the current human controlled hydrological regime strongly influenced the poc sources transport modes and fluxes in 2012 2013 the huanghe delivered 0 73 tg 1 tg 1012 g of poc to the sea and about 28 of the annual poc flux occurred within a short human induced flood event globally the huanghe should be one of the largest rivers in the transfer and re burial of fossil oc however the fate of huanghe fossil oc is still unconstrained and needs to be further investigated copyright 2015 john wiley sons ltd

comparison of early aftershock forecasting for the 2008 wenchuan m s 8 0 earthquake the ms8 0 earthquake that occurred in wenchuan sichuan in 2008 provides an important case for the study of operational earthquake forecasting and short term aftershock forecasting of major disaster inducing earthquakes in china this paper focuses on the comparative study of the applicability of the epidemic type aftershock sequence etas model the reasenberg jones r j model and the omi r j model which are widely adopted internationally for short term aftershock forecasting and seismic hazard mitigation strategy research we compare the stability of model parameters and aftershock occurrence rate forecasting and evaluate the effectiveness of forecasting using the n test and t test with multiple time windows the results show that the sequence parameters of the etas model the r j model and the omi r j model tend to stabilize after 15 50 15 50 and 6 00 days following the earthquake respectively and the attenuation of the wenchuan ms8 0 earthquake is rather normal compared to the etas model and the r j model the omi r j model obtain steadier model parameters in a shorter time with significantly smaller parameters porj corj borj and standard deviations among the three models the overall aftershock occurrence rate forecasted by the r j model is the highest followed by the omi r j model while that of the etas model is the lowest n test results show overall forecasting effectiveness of 93 8 80 7 and 97 7 for the etas r j and omi r j models respectively with the etas and omi r j models superior to the r j model and the omi r j model slightly better than the etas model the overall information gain per earthquake calculation results show that the etas model is superior to the omi r j and r j models while the omi r j model is better than the r j model thus the combined use of the etas and omi r j models by focusing on their respective strengths might ensure optimal performance these maneuverable forecasting approaches to short term aftershock model forecasting will play a vital role in efficient post disaster relief emergency management decision making and post disaster reconstruction

bayesian confidence intervals for the magnitude of the largest aftershock aftershock sequences which follow large earthquakes last hundreds of days and are characterized by well defined frequency magnitude and spatio temporal distributions the largest aftershocks in a sequence constitute significant hazard and can inflict additional damage to infrastructure that is already affected by the main shock therefore the estimation of the magnitude of a possible largest aftershock in a sequence is of high importance in this work a bayesian predictive distribution and the corresponding confidence intervals for the magnitude of the largest expected aftershock in a sequence are derived using the framework of bayesian analysis and extreme value statistics the analysis is applied to 19 well known aftershock sequences worldwide to construct retrospectively the confidence intervals for the magnitude of the subsequent largest aftershock by using the statistics of early aftershocks in the sequences

comparison of short term and time independent earthquake forecast models for southern california we have initially developed a time independent forecast for southern california by smoothing the locations of magnitude 2 and larger earthquakes we show that using small m 2 earthquakes gives a reasonably good prediction of m 5 earthquakes our forecast outperforms other time independent models kagan and jackson 1994 frankel et al 1997 mostly because it has higher spatial resolution we have then developed a method to estimate daily earthquake probabilities in south ern california by using the epidemic type earthquake sequence model kagan and knopoff 1987 ogata 1988 kagan and jackson 2000 the forecasted seismicity rate is the sum of a constant background seismicity proportional to our time independent model and of the aftershocks of all past earthquakes each earthquake triggers aftershocks with a rate that increases exponentially with its magnitude and decreases with time following omori s law we use an isotropic kernel to model the spatial distribution of aftershocks for small m 5 5 mainshocks for larger events we smooth the density of early aftershocks to model the density of future aftershocks the model also assumes that all earthquake magnitudes follow the gutenberg richter law with a uniform b value we use a maximum likelihood method to estimate the model parameters and test the short term and time independent forecasts a retro spective test using a daily update of the forecasts between 1 january 1985 and 10 march 2004 shows that the short term model increases the average probability of an earthquake occurrence by a factor 11 5 compared with the time independent forecast

origin of particulate organic carbon in the upper st lawrence isotopic constraints abstract seven sampling locations in the upper st lawrence river near the city of cornwall ontario canada including the main river and six near shore ecosystems a creek embayments and a wetland were studied in order to determine the origin of particulate organic carbon parameters studied included chlorophyll a chl a particulate organic carbon poc and dissolved inorganic carbon dic as well as the isotopic compositions of the latter two 13cpoc 13cdic the results show that in situ photosynthesis and detrital inputs are both significant contributors to the poc pool in the isolated embayments the former dominates during warm seasons with poc concentrations up to 2663 g l and chl a concentrations up to 26 1 g l near shore ecosystems have a wide range of 13cpoc values 31 5 to 16 3 but this variability is not reflected in the main channel there the 13cpoc signal is uniformly close to 27 in accord with estimates from earlier studies on the river s estuary this suggests that the poc contribution from near shore ecosystems is minor although the main channel has low chl a concentrations model calculations suggest that most of its poc originates from photosynthetic activity probably within the great lakes

three ingredients for improved global aftershock forecasts tectonic region time dependent catalog incompleteness and intersequence variability following a large earthquake seismic hazard can be orders of magnitude higher than the long term average as a result of aftershock triggering because of this heightened hazard emergency managers and the public demand rapid authoritative and reliable aftershock forecasts in the past u s geological survey usgs aftershock forecasts following large global earthquakes have been released on an ad hoc basis with inconsistent methods and in some cases aftershock parameters adapted from california to remedy this the usgs is currently developing an automated aftershock product based on the reasenberg and jones 1989 method that will generate more accurate forecasts to better capture spatial variations in aftershock productivity and decay we estimate regional aftershock parameters for sequences within the garcia et al 2012 tectonic regions we find that regional variations for mean aftershock productivity reach almost a factor of 10 we also develop a method to account for the time dependent magnitude of completeness following large events in the catalog in addition to estimating average sequence parameters within regions we develop an inverse method to estimate the intersequence parameter variability this allows for a more complete quantification of the forecast uncertainties and bayesian updating of the forecast as sequence specific information becomes available online material omori parameter confidence limits alternative omori fits taking into account b value variation larger tectonic regions and a longer temporal fitting window and synthetic test results

loss of organic matter from riverine particles in deltas abstract in order to examine the transport and burial of terrigenous organic matter along the coastal zones of large river systems we assessed organic matter dynamics in coupled river delta systems using mineral surface area as a conservative tracer for discharged riverine particulate organic matter pom most pom in the rivers studied n 6 is tightly associated with suspended mineral material e g it is sorbed to mineral surfaces average organic loadings in the amazon river 0 67 0 14 mg c m 2 the river for which we have the largest dataset are approximately twice that of sedimentary minerals from the amazon delta 0 35 mg c m 2 stable carbon isotope analysis indicate that approximately two thirds of the total carbon on the deltaic particles is terrestrial the combined surface normalized isotope distinguished estimate is that 70 of the amazon fluvial pom is not buried in the delta consistent with other independent evidence aller et al 1996 losses of terrestrial pom have also been quantified for the river delta systems of columbia in the usa fly in new guinea and huange he in china if the losses of riverine pom observed in these river delta systems are representative of rivers worldwide then the surface constrained analyses point toward a global loss of fluvial pom in delta regions of 0 1 x 1015 g c y 1

foreshocks explained by cascades of triggered seismicity 1 the observation of foreshocks preceding large earthquakes and the suggestion that foreshocks have specific properties that may be used to distinguish them from other earthquakes have raised the hope that large earthquakes may be predictable among proposed anomalous properties are the larger proportion than normal of large versus small foreshocks the power law acceleration of seismicity rate as a function of time to the mainshock and the spatial migration of foreshocks toward the mainshock when averaging over many sequences using southern california seismicity we show that these properties and others arise naturally from the simple model that any earthquake may trigger other earthquakes without arbitrary distinction between foreshocks aftershocks and mainshocks we find that foreshock precursory properties are independent of the mainshock size this implies that earthquakes large or small are predictable to the same degree as seismicity rate is predictable from past seismicity by taking into account cascades of triggering the cascades of triggering give rise naturally to long range and long time interactions which can explain the observations of correlations in seismicity over surprisingly large length scales

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control