a scaling law for slow earthquakes with the availability of the global positioning system and other technical advances a growing number of unusual earthquake phenomena occurring at relatively long periods have been recognized they include deep episodic tremor low frequency earthquakes slow slip events and silent earthquakes based on data chiefly from western japan ide et al report that these slow seismic events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes a diverse array of unusual earthquake phenomena occurring at relatively long periods slow events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes indicating that they comprise a new earthquake category recently a series of unusual earthquake phenomena have been discovered including deep episodic tremor1 low frequency earthquakes2 very low frequency earthquakes3 slow slip events4 and silent earthquakes5 6 7 8 9 each of these has been demonstrated to arise from shear slip just as do regular earthquakes but with longer characteristic durations and radiating much less seismic energy here we show that these slow events follow a simple unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes we find that their seismic moment is proportional to the characteristic duration and their moment rate function is constant with a spectral high frequency decay of f 1 this scaling and spectral behaviour demonstrates that they can be thought of as different manifestations of the same phenomena and that they comprise a new earthquake category the observed scale dependence of rupture velocity for these events can be explained by either a constant low stress drop model or a diffusional constant slip model this new scaling law unifies a diverse class of slow seismic events and may lead to a better understanding of the plate subduction process and large earthquake generation

a field study of hydraulic geochemical and stable isotope relationships in a coastal wetlands system both chemical and stable isotope data provide important supplemental information to more traditional hydraulic data and unravel the processes that underpin the large variations in chemical and stable isotopic composition within a coastal wetland system the system studied was the lake warden wetlands located in esperance in south coast of western australia the spatial and temporal variations of chemical and isotopic composition of the individual water bodies within the system were measured for an annual cycle in broad terms the groundwater levels appear to follow the topography but the distinct higher chloride and isotopic concentrations observed within the wetlands were not reflected in the low lying coastal plain groundwater the hydraulic analysis of the region surrounding the wetlands suggest that the wetlands are flow through bodies however the chemical and isotope information indicates the lakes almost invariably act as discharge points for the surface water flows and the north south groundwater flow the northeast southwest groundwater flow is along an observed paleochannel within the wetlands system and in this case the chemical and isotopic evidence are complimentary with the hydraulic study the study highlighted the importance of correcting the isotopic values for the salt effect in highly saline water the isotopic activity ratios of 2h 2ha of some samples were up to 15 higher than the uncorrected values the high salinity of the terminal lake in the wetlands chain also required implementation of a theoretical evaporative model to explain the lower enrichment of the isotopic results as compared to expectations for a shallow and ephemeral lake the inter lake variation in the theoretical evaporative model parameters coupled with a significant variation in the hydrochemistry and isotope composition suggests that the lakes within the wetlands system cannot be treated as single water body as is implied by the bathymetry survey

salinization in coastal aquifers of arid zones an example from santo domingo baja california sur mexico groundwater quality in the santo domingo irrigation district area in baja california sur mexico indicates the presence of various salinization processes 1 the geological matter of marine origin comprising the aquifer material suffers diagenetic effects due to its interaction with groundwater of low salinity 2 the effects of intensive agriculture practices produce effluents that infiltrate to the saturated zone and 3 the extraction of groundwater causes modifications in the natural flow system induces lateral flow of seawater from the coast line however groundwater management has been carried out with the belief that the latter is the main source of salinization this has resulted in a policy of installing wells increasingly far from the coast which is not solving the problem irrigation return and seawater that remains in the geological units have been identified as major sources of salinization controls should be imposed when installing wells in contact with clayey units that form the base of the aquifer extracted groundwater consists of a mixture of 1 groundwater of relatively low salinity that circulates in the aquifer and 2 an extreme member with salinity different to seawater contained mainly in formations that have low permeability which limits the aquifer underneath the geochemistry of carbonates and cation exchange reactions both direct and reverse control the concentration of ca mg na and hco3 as well as ph values the concentrations of dissolved trace elements f li ba sr suggest that the extreme saline member is different from the average seawater composition a distinction between the salinization caused by farming practices and that blamed on seawater is defined by the use of no3

multiparameter two dimensional inversion of scattered teleseismic body waves 3 application to the cascadia 1993 data set this is the third paper in a three part series that examines formal inversion of the teleseismic p wave coda for discontinuous two dimensional 2 d variations in elastic properties beneath dense arrays of three component broadband seismometers in this paper the method is applied to data from the incorporated research institutions for seismology program for array seismic studies of the continental lithosphere iris passcal cascadia 1993 experiment undertaken across central oregon two major features are imaged in the resulting model the continental moho becomes evident 150 km from the coast beneath the western cascades and extends through the eastern end of the profile at 35 40 km depth in the western portion of the model oceanic crust of the subducting juan de fuca plate dips shallowly 12 at the coast and more steeply 27 below the willamette valley and is evident to depths of 100 km beneath the high cascades the abrupt increase in plate dip at 40 km depth coincides with an apparent thickening of the oceanic crust followed by a diminution in its signature building on previous work we argue that these results are consistent with the consequences of prograde metamorphic reactions occurring within the oceanic crust progressive dehydration at lower grade facies conditions culminates in the transformation to eclogite producing a pronounced increase in the seismic velocity density and dip of the subducting plate and structural complexity in the overlying wedge

characteristic variations of sea surface temperature with multiple time scales in the north pacific abstract temporal evolution and spectral structure of sea surface temperature sst anomalies in the north pacific over the last 37 years are investigated on the three characteristic time scales shorter than 24 months hf 24 60 months es and longer than 60 months dc the leading empirical orthogonal function eof for the dc time scale is characterized by a zonally elongated monopole centered at around 40 n 180 the leading eof for the hf time scale is somewhat similar to that for the dc time scale although there are two centers of action with the same polarity at the mid and western pacific the leading eof for the es time scale however exhibits a different pattern whose center of action at the mid pacific is located farther southeastward in the time evolution of the sst anomalies associated with the leading eof of the dc time scale several anomaly periods can be identified that last five years or longer the transition from a persistent period to another with the opposite polarity is gene

high frequency ground motion scaling in the pacific northwest and in northern and central california abstract large data sets of vertical and horizontal seismograms from the pacific northwest seismic network northern california seismic network and berkeley digital seismic network are used to study the high frequency 0 25 16 hz ground motion scaling characteristics in washington oregon northern california 39 n to 42 n and 119 w to 124 w and central california 35 n to 39 n and 118 w to 123 w we used peak filtered ground velocities to characterize the propagation excitation and site terms the regression results for propagation were modeled using a geometrical spreading function g r and a frequency dependent attenuation q f q 0 f for the pacific northwest the best q model that fits the observation is expressed by q f 280 f 0 55 the eastern central california and western central california results are parameterized with q f 280 f 0 50 and q f 240 f 0 35 respectively the northern california results are not easy to model and require using a frequency dependent and a frequency dependent geometrical spreading the geometrical spreading effect for the frequencies higher than 5 hz is very strong in that region the excitation terms for the small events studied were modeled using a brune s source model an average stress drop of 30 bars was obtained for the pacific northwest the northern california average value for stress drop is 90 bars the observations of eastern central california were modeled with a stress drop of 49 bars while the best fit for the western part required 80 bars the range of the values obtained for q g r and indicates that the ground motion parameters for one region should not be used for another as an example our results show that the ground motion amplitude due to an m w 5 0 earthquake at a distance of 50 km is different by a factor of 1 5 between the pacific northwest and eastern central california

earthquake spectra and near source attenuation in the cascadia subduction zone f 1 for slow events and as f 2 for fast earthquakes we show that at least in cascadia wave propagation effects likely control spectral decay rates above 2 hz we use seismograms from multiple small aperture arrays to estimate the spectral decay rates of near source spectra of 37 small events and find strong correlation between source location and decay rate the decay rates 1 vary overall by an amount in excess of that inferred to distinguish slow sources from fast earthquakes 2 are indistinguishable for sources separated by a few tens of km or less and 3 separate into two populations that correlate with propagation through and outside a low velocity zone imaged tomographically we find that some events repeat as is characteristic of low frequency earthquakes lfes but have spectra similar to those of non repeating earthquakes we also find no correlation between spectral decay rates and rates of ambient tremor activity these results suggest that earthquakes near the plate boundary at least in cascadia do not distinctly separate into slow and fast classes and correctly accounting for propagation effects is necessary to characterize sources

frequency dependent lg q within the continental united states frequency dependent crustal attenuation 1 q is determined for seven distinct physiographic tectonic regions of the continental united states using high quality lg waveforms recorded on broadband stations in the frequency band 0 5 to 16 hz lg attenuation is determined from time domain amplitude measurements in one octave frequency bands centered on the frequencies 0 75 1 0 3 0 6 0 and 12 0 hz modeling errors are determined using a delete j jackknife resampling technique the frequency dependent quality factor is modeled in the form of q q 0 f regions were initially selected based on tectonic provinces but were eventually limited and adjusted to maximize ray path coverage in each area earthquake data was recorded on several different networks and constrained to events occurring within the crust m b 3 5 in size a singular value decomposition inversion technique was applied to the data to simultaneously solve for source and receiver terms along with q for each region at specific frequencies the lowest crustal q was observed in northern and southern california where q is described by the functions q 152 37 f 0 72 0 16 and q 105 26 f 0 67 0 16 respectively the basin and range province pacific northwest and rocky mountain states also display lower q and a strong frequency dependence characterized by the functions q 200 40 f 0 68 0 12 q 152 49 f 0 76 0 18 and q 166 37 f 0 61 0 14 respectively in contrast in the central and northeast united states q functions are q 640 225 f 0 344 0 22 and q 650 143 f 0 36 0 14 respectively show a high crustal q and a weaker frequency dependence these results improve upon previous lg modeling by subdividing the united states into smaller distinct tectonic regions and using significantly more data that provide improved constraints on frequency dependent attenuation and errors a detailed attenuation map of the continental united states can provide significant input into hazard map mitigation both scattering and intrinsic attenuation mechanisms are likely to play a comparable role in the frequency range considered in the study

demise of a harbor a geochemical chronicle from ephesus a b s t r a c t at the end of the first century bc ephesus became the roman capital of asia minor and the most important commercial religious and cultural center of the region in order to evaluate the status of anthropogenic fluxes in the port of ephesus a 12 m long sediment core drilled in the roman basin was investigated to shed light on the paleo environmental evolution of the harbor using grain size distri bution analysis 14 c ages major and trace element geochemistry and pb isotope compositions with the help of complementary sedimentological data and principal component analysis five distinct units were identified which together reflect the different stages of water history in the harbor among the major disruptive events affecting the port were earthquakes and military events both of which were partic ularly effective at destroying the water distribution system seasonal floods of the cayster river kucuk menderes were the major source of the silt that progres sively infilled the harbor silting in was further enhanced by the westward migration of the river mouth a single major disruptive event located at 550 cm core depth and heralding the development of anoxia in the harbor marks the end of the dynamic regime that otherwise controlled the harbor water throughout the roman empire period this remarkable event may correspond to a major disruption of the aqueduct system or to a brutal avulsion of the cayster river bed it clearly represents a major disturbance in the history of life at ephesus it is poorly dated but probably occurred during the reign of augustus or shortly after lead isotope and trace metal evidence suggest that in the four bottom units pollution was subdued with respect to other pb metal inputs presumably those from aqueducts and natural karstic springs near the top of the core which coincides with harbor abandonment and the more recent period anthropogenic pb contam ination is clearly visible in both pb abundances and isotopic compositions

water and sediment geochemistry of major kumaun himalayan lakes india four major himalayan lakes in kumaun region in india namely nainital bhimtal sattal and naukuchiatal have been studied to understand water and sediment geochemistry the lakes are characterised by varying degrees of natural and human influences the nainital is intensively used and is a major tourist destination whereas the other three lakes have attracted much attention lately the lakes have a tectonic origin and are characterised by dolomites limestones shales and silicate rocks the water chemistry is dominated by ca mg and hco3 an indication of a carbonate lithology source for the water composition about 55 80 of na and only 30 40 of ca in the lakes are derived from silicate lithology the nainital lake is also characterised by a high chemical index of alteration which is reflected in its high carbonate and the clay mineral content of the sediments model calculations show that 33 and 67 of nitrate in sattal lake is contributed by agriculture and cultural effects respectively the 87sr 86sr ratios in the lakes are very high 0 72 with samples from sattal lake being extremely radiogenic 0 82 similar to many himalayan rivers the 1 sr 87sr 86sr in sediments show two major sources for sr silicates and carbonates the contributions of sr from carbonate and silicate lithology is estimated to be 25 and 60 respectively in bhimtal lake

a rotated eof analysis of global sea surface temperature variability with interannual and interdecadal scales abstract spatiotemporal variability of preferred global scale sea surface temperature anomaly patterns is documented applying a varimax rotated empirical orthogonal function r eof analysis to monthly mean sst anomalies the present study focuses especially on the interdecadal variability of leading r eof modes it is first found that temporal variability of r eof1 has a quasi periodicity of 2 5 years and coincides quite well with the occurrence of the enso event hence this mode can be identified with the enso mode and distinguished from the other modes dominated by interdecadal variability the authors find that r eof2 typically shows the dominance of interdecadal variability and signals of the enso phenomenon are removed this mode is characterized by increasing indian ocean sst and decreasing central north pacific sst around 40 50 n in the recent ten or more years a further indication is that both r eof3 and r eof4 which show the dominance of interdecadal variability are fundamentally regarded a

segmentation of mesoscale ocean surface dynamics using satellite sst and ssh observations multisatellite measurements of altimeter derived sea surface height ssh and sea surface temperature sst provide a wealth of information about ocean circulation particularly mesoscale ocean dynamics which may involve strong spatiotemporal relationships between ssh and sst fields within an observation driven framework we investigate the extent to which mesoscale ocean dynamics may be decomposed into a mixture of dynamical modes characterized by different local regressions between ssh and sst fields formally we develop a novel latent class regression model to identify dynamical modes from joint ssh and sst observation series applied to the highly dynamical agulhas region we demonstrate and discuss the geophysical relevance of the proposed mixture model to achieve a spatiotemporal segmentation of the upper ocean dynamics

non volcanic tremor associated with the march 2010 gisborne slow slip event at the hikurangi subduction margin new zealand 1 non volcanic tremor accompanies slow slip events at most circum pacific subduction zones previously the hikurangi subduction margin new zealand and the boso peninsula of japan have been noted as exceptions where slow slip which occurs at shallow depth compared to other subduction zones does not generate seismic tremor the lack of tremor observations raises questions whether tremor and slow slip are manifestations of the same process and whether different temperature and pressure conditions influence the physical mechanism of tremor production analysis of seismic data during the march 2010 gisborne slow slip event new zealand reveals that this slow slip event at the northern hikurangi margin is accompanied by tremor with distinctive characteristics compared to local microearthquakes both the gisborne area of new zealand and the boso peninsula of japan are underlain by thick accumulations of sedimentary rocks that likely inhibit the observation of low amplitude tremor due to high attenuation discovery of tremor in new zealand suggests that tremor may always accompany slow slip and that its apparent absence at the boso peninsula the hikurangi margin prior to this study and any future regions discovered to experience slow slip without concurrent tremor may be the effect of highly attenuating sediments

imaging the source region of cascadia tremor and intermediate depth earthquakes the subduction of hydrated oceanic crust releases volatiles that weaken the plate boundary interface trigger earthquakes and regulate transient phenomena such as episodic tremor and slip ets it is not clear how dehydration can separately induce earthquakes within the subducting plate and ets partly because few data exist on their relationship to subduction zone structures we present results of a seismic experiment in the washington cascades united states that images a region producing both earthquake types migration of scattered teleseis mic waves provides images of low velocity subducting crust at depths 40 45 km with sharp boundaries above and below it the sharp upper boundary indicates a layer of weak sediment or an overpressured fault zone that terminates abruptly downdip at 40 45 km depth regular earthquakes are at the top of the mantle within the downgoing plate everywhere the plate is 95 km deep but ets only exists where the sharp upper boundary occurs the ets location supports models of slow slip that require near lithostatic fluid pressure whereas regular earthquakes nucleate closer to the origin of metamorphic dehydration very low shear stresses on the plate boundary may limit seismicity to ets and similar phenomena

modes of interannual and interdecadal variability of pacific sst abstract the multichannel singular spectrum analysis has been used to characterize the spatio temporal structures of interdecadal and interannual variability of sst over the pacific ocean from 20 s to 58 n using the comprehensive ocean atmosphere data set from 1950 to 1993 three modes with distinctive spatio temporal structures were found they are an interdecadal mode a quasi quadrennial qq oscillation with a period of 51 months and a quasi biennial qb oscillation with a period of 26 months the interdecadal mode is a standing mode with opposite signs of sst anomalies in the north pacific and in the tropical pacific the amplitude of this mode is larger in the central north pacific than in the tropical pacific this mode contributes 11 4 to the total variance it is associated with cooling in the central north pacific and warming in the equatorial pacific since around 1976 77 the qq oscillation exhibits propagation of sst anomalies northeastward from the philippine sea and then eastward along 4

attenuation of lg in the western us using the usarray 1 the unprecedented breadth and density of the usarray allows us to resolve lateral variations of 1 hz lg attenuation to 0 5 degrees over much of the western united states we collected over 31 000 lg amplitudes from 547 events and 408 stations of the initial usarray footprint two dimensional tomographic inversion yielded q ranging from 60 to 550 with a variance reduction of 47 relative to the best fit constant q model q 155 q is low over most of the region with lowest values associated with recent volcanic activity and active shear zones high q is found in older stable crust notably the colorado and columbia plateaus while smaller islands of high q are associated with batholiths including the sierra nevada peninsular and bitterroot ranges the western mojave and okanogan highlands as well as other areas of competent crust such as the harcuvar range and two topographically bounded blocks in the basin and range

earthquake stress drops and inferred fault strength on the hayward fault east san francisco bay california we study variations in earthquake stress drop with respect to depth faulting regime creeping versus locked fault behavior and wall rock geology we use the p wave displacement spectra from borehole seismic recordings of m 1 0 4 2 earthquakes in the east san francisco bay to estimate stress drop using a stack and invert empirical green s function method the median stress drop is 8 7 mpa and most stress drops are in the range between 0 4 and 130 mpa an apparent correlation between stress drop and magnitude is entirely an artifact of the limited frequency band of 4 55 hz there is a trend of increasing stress drop with depth with a median stress drop of 5 mpa for 1 7 km depth 10 mpa for 7 13 km depth and 50 mpa deeper than 13 km we use s p amplitude ratios measured from the borehole records to better constrain the first motion focal mechanisms high stress drops are observed for a deep cluster of thrust faulting earthquakes the correlation of stress drops with depth and faulting regime implies that stress drop is related to the applied shear stress we compare the spatial distribution of stress drops on the hayward fault to a model of creeping versus locked behavior of the fault and find that high stress drops are concentrated around the major locked patch near oakland this also suggests a connection between stress drop and applied shear stress as the locked patch may experience higher applied shear stress as a result of the difference in cumulative slip or the presence of higher strength material the stress drops do not directly correlate with the strength of the proposed wall rock geology at depth suggesting that the relationship between fault strength and the strength of the wall rock is complex

tectonic significance of mafic volcanic rocks in a mesozoic sequence of the menderes massif west turkey the mesozoic platform sequence of the menderes massif consists of thick succession of detrital and carbonate rocks in this sequence there are mafic metavolcanic rocks at two different levels the first level of mafic metavolcanic intercalations is in the late triassic detrital rich series located in the caltasi formation which is the lowermost unit of the mesozoic platform the second level of the mafic metavolcanic rocks is located in the late cretaceous paleocene selcuk formation laying on top of the platform sequence the caltasi formation which is composed of mica schists thinly bedded cherts calc schist and mafic volcanic intercalations unconformably overlie the bayindir formation which consists of mica schists phyllites and white quartzites of palaeozoic or probably older age the mafic volcanic rocks in the caltasi formation are alkaline basalts with within plate characteristics and are formed during an intraplate extension the caltasi formation is conformably overlain by the kayaalti formation represented by calc schists dolomitic marbles and rudist and emery bearing massive marbles in ascending order the selcuk formation overlies the kayaalti formation and consists of a mica schist matrix with allochthonous blocks of mafic volcanic rocks metaperidotites metagabbros and massive marbles the mafic volcanic rocks in the selcuk formation are tholeiitic basalts and are petrologically similar to mid oceanic basalts the geological and geochemical characteristics of the mafic metavolcanic rocks in the caltasi formation indicate that during the late triassic the menderes platform was segmented probably by the opening of a branch of the neotethyan ocean between the late triassic and the late cretaceous the menderes carbonate platform was built up during the latest cretaceous early paleocene a slab of oceanic crust obducted on this platform and provided slices of mafic metavolcanic rocks into the selcuk formation

hydrogeochemical investigation of kucuk menderes river coastal wetland selcuk izmir turkey kucuk menderes river forms a rich coastal wetland inside in the selcuk plain three saline brackish lakes one swamp and kucuk menderes river are these wetlands components alkaline slightly alkaline type lakes are recharged from precipitation and karstic springs that discharge from marble schist and marble alluvium contacts in the northern and southern parts of the study area water types of the wetland are na cl and na ca mg hco3 cl in both rainy and dry seasons both seawater intrusion and evaporation as being the sources of the ions justify the presence of na cl na so4 and cl so4 in the wetland water environmental isotopes were used to identify the relationship between wetland and groundwater in the selcuk plain the 18o and d composition of wetland area samples have changed between 6 42 to 4 56 and 36 40 to 23 80 respectively the lakes and rivers are plotted on the mixing line by slope of 5 2 and these data indicate that wetland is affected from seawater intrusion the recharge area that was sampled in order to compare the wetland has ca hco3 water type with a neutral slightly alkaline ph values and the main hydrogeochemical process is weathering the different types of silicates iron manganese and selenium are the dominant minor ions due to the high biological activities and organic matters in the lakes there are two contamination risks for this wetland 1 waste disposal site and 2 water treatment plant where the purified waters are released into the river ec al as cd cu fe and zn values exceed those of aquatic life standards in the near future these sites will pose a danger for wetland wild life and surrounding irrigation water suppliers

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

comprehensive analysis of earthquake source spectra and swarms in the salton trough california 1 we study earthquakes within california s salton trough from 1981 to 2009 from a precisely relocated catalog we process the seismic waveforms to isolate source spectra station spectra and travel time dependent spectra the results suggest an average p wave q of 340 agreeing with previous results indicating relatively high attenuation in the salton trough stress drops estimated from the source spectra using an empirical green s function egf method reveal large scatter among individual events but a low median stress drop of 0 56 mpa for the region the distribution of stress drop after applying a spatial median filter indicates lower stress drops near geothermal sites we explore the relationships between seismicity stress drops and geothermal injection activities seismicity within the salton trough shows strong spatial clustering with 20 distinct earthquake swarms with at least 50 events they can be separated into early mmax and late mmax groups based on the normalized occurrence time of their largest event these swarms generally have a low skew value of moment release history ranging from 9 to 3 0 the major temporal difference between the two groups is the excess of seismicity and an inverse power law increase of seismicity before the largest event for the late mmax group all swarms exhibit spatial migration of seismicity at a statistical significance greater than 85 a weighted l1 norm inversion of linear migration parameters yields migration velocities from 0 008 to 0 8 km hour to explore the influence of fluid injection in geothermal sites we also model the migration behavior with the diffusion equation and obtain a hydraulic diffusion coefficient of approximately 0 25 m2 s for the salton sea geothermal site which is within the range of expected values for a typical geothermal reservoir the swarms with migration velocities over 0 1 km hour cannot be explained by the diffusion curve rather their velocity is consistent with the propagation velocity of creep and slow slip events these variations in migration behavior allow us to distinguish among different driving processes

human impact on holocene sediment dynamics in the eastern mediterranean the example of the roman harbour of ephesus during the past millennia many erosion and accumulation processes have been modified by anthropogenic impact this holds especially true for the environs of ancient settlements and their harbours along the mediterranean coasts our multi proxy investigations in the roman harbour and the harbour canal of ephesus western turkey reveals that humans have significantly triggered soil erosion during the last three millennia since the eighth century bc and especially since the hellenistic period a high sed imentation rate indicates fast alluviation and delta progradation of the kucuk menderes deforestation agriculture especially ploughing and grazing especially goats were the main reasons for erosion of the river catchment area one consequence was significant siltation of the hellenistic roman harbour basin this sediment trap archives the human impact which was strongly enhanced from hellenistic roman to byzantine times second first centuries bc to the sixth seventh centuries ad evidenced by high sedimentation rates raised values of heavy metal contaminations lead pb copper cu the occurrence of fruit tree pollen and of intestinal parasites from the middle to the end of the first millennium ad the influence of ephesus declined which resulted in a decrease of human impact studies of several ancient settlements around the mediterranean sea tell a comparable story they also confirm that during their most flourishing periods the human impact totally overprinted the climatic one to detect the latter geo bio archives of relatively pristine areas have to be investigated in detail

sedimentary underplating at the cascadia mantle wedge corner revealed by seismic imaging earth s largest earthquakes occur at the boundary between subducting oceanic crust and the overriding plate yet the position of the plate boundaries remains uncertain analysis of zones of low seismic wave velocities beneath the northern cascadia subduction zone implies that the plate boundary here may be deeper than previously thought

tiny intraplate earthquakes triggered by nearby episodic tremor and slip in cascadia episodic tremor and slip ets has been observed in many subduction zones but its mechanical underpinnings as well as its potential for triggering damaging earthquakes have proven difficult to assess here we use a seismic array in cascadia of unprecedented density to monitor seismicity around a moderate 16 day ets episode in the 4 months of data we examine we observe five tiny earthquakes within the subducting slab during the episode and only one more in the same area which was just before and nearby the next ets burst these earthquakes concentrate along the sides and updip edge of the ets region consistent with greater stress concentration there than near the middle and downdip edge of the tremor area most of the seismicity is below the megathrust with a similar depth extent to the background intraslab seismicity the pattern of earthquakes that we find suggests slow slip has a more continuous temporal and spatial pattern than the tremor loci which notoriously appear in bursts jumps and streaks

variations of fluid pressure within the subducting oceanic crust and slow earthquakes 1 we show fine scale variations of seismic velocities and converted teleseismic waves that reveal the presence of zones of high pressure fluids released by progressive metamorphic dehydration reactions in the subducting philippine sea plate in tokai district japan these zones have a strong correlation with the distribution of slow earthquakes including long term slow slip ltss and low frequency earthquakes lfes overpressured fluids in the ltss region appear to be trapped within the oceanic crust by an impermeable cap rock in the fore arc and impede intraslab earthquakes therein in contrast fluid pressures are reduced in the lfe zone which is deeper than the centroid of the ltss because there fluids are able to infiltrate into the narrow corner of the mantle wedge leading to mantle serpentinization the combination of fluids released from the subducting oceanic crust with heterogeneous fluid transport properties in the hanging wall generates variations of fluid pressures along the downgoing plate boundary which in turn control the occurrence of slow earthquakes

coupled pattern analysis of sea surface temperature and topex poseidon sea surface height abstract though thermal effects dominate steric changes in sea level the long period contribution of thermal expansion to sea level is uncertain nerem et al found that a global map of sea surface temperature sst trends and a corresponding map of topex poseidon derived sea surface height ssh trends were strongly correlated this result is explored with a coupled pattern analysis cpa between five years of global sst and ssh which allows for matching of modes of common temporal variability the dominant mode found is an annual cycle that accounts for nearly all 95 3 of the covariance between the fields and has a strong sst ssh spatial correlation 0 68 the spatial correlation is strong in both the atlantic 0 80 and the pacific 0 70 good temporal and spatial agreement between the ssh and sst fields for the primary seasonal mode suggests that a robust regression between fields may have some physical significance with respect to thermal expansion and that the regression coefficient might be

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

slow earthquakes coincident with episodic tremors and slow slip events we report on the very low frequency earthquakes occurring in the transition zone of the subducting plate interface along the nankai subduction zone in southwest japan seismic waves generated by very low frequency earthquakes with seismic moment magnitudes of 3 1 to 3 5 predominantly show a long period of about 20 seconds the seismicity of very low frequency earthquakes accompanies and migrates with the activity of deep low frequency tremors and slow slip events the coincidence of these three phenomena improves the detection and characterization of slow earthquakes which are thought to increase the stress on updip megathrust earthquake rupture zones

tremor bands sweep cascadia 1 during the slow slip events in cascadia and japan a well documented feature of nonvolcanic tremor nvt is its puzzling slow along strike migration but the cause possible implications and underlying physics of this long term tremor migration and its relationship with slow slip remain elusive here we use tremor data recorded by a dense seismic array in cascadia and apply a beam backprojection technique to map the spatiotemporal evolution of tremor with high resolution it reveals that elongated slip parallel bands of tremor activity illuminate the slipping part of the plate interface over the time scale of several hours and sweep cascadia along strike from south to north we propose that small changes in static stress due to slow slip in a section of the fault cause slip and associated nvt activity in the adjacent section and the resulting progressive along strike transfer of stress is responsible for the long term tremor migration during a slow slip event

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

hydrogeochemical investigation in an arid region of iran tabas central iran groundwater is the most important source of water supply in iran and understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in tabas area a total of 29 samples of groundwater in tabas area have been analyzed for ions and major elements groundwater of the study area is characterized by the dominance of na cl water type groundwater was generally acidic to high alkaline with ph ranging from 5 42 to 10 75 the tds as a function of mineralization characteristics of the groundwater ranged from 479 to 10 957 mg l with a mean value of 2 759 mg l the ca2 mg2 so42 and hco3 were mainly derived from the dissolution of calcite dolomite and gypsum the cu pb and zn ions are not mobile in recent ph eh but these conditions controlled dissolved se v and mo in groundwater the as is released in groundwater as a result of the weathering of sulfide minerals like arsenopyrite

sea surface temperature and sea surface height variability in the north pacific ocean from 1993 to 1999 1 correlations between advanced very high resolution radiometer pathfinder sea surface temperature sst and topex sea surface height ssh anomalies are calculated for the 7 year period 1993 1999 in the equatorial and north pacific these correlations provide measures of ssh and sst covariability and are obtained using an empirical orthogonal function analysis separately on the two fields and a singular value decomposition svd method on both fields simultaneously these correlations reveal distinct sst ssh states a warm elevated period from january 1993 to december 1994 a cooler lower phase spanning january 1995 through december 1996 and the strongly variable el nino southern oscillation enso period spanning 1997 1999 the relationships between these sst ssh states and the dominant interannual and interdecadal modes of pacific variability are investigated through correlations with indices for the southern oscillation pacific north american pna pattern and pacific decadal oscillation pdo when including the tropics significant correlations between the first svd mode of the sst ssh covariability and the interannual enso pattern and interdecadal pdo pattern are evident restricting the focus to the extratropical north pacific reveals significant correlations with only the interdecadal pdo pattern while the first mode reveals connections to the enso and pdo patterns the second svd mode indicates significant correlations to the pna pattern for both the tropical and extratropical pacific

cascadia tremor spectra low corner frequencies and earthquake like high frequency falloff the discovery of non volcanic tremor nvt has opened a new window to observe major earth plate boundaries however the spectral characteristics of nvt have not been well studied due to poor signal to noise ratio snr on individual seismograms we estimate the spectral content of cascadia tremor between 2 5 and 20 hz by suppressing noise using array analysis and compute empirical path corrections using nearby small earthquakes we demonstrate that the displacement spectra of the cascadia tremor have corner frequencies around 3 8 hz and fall off at f 2 to f 3 at higher frequencies our results have the following implications 1 the high frequency falloff of tremor agrees with the observations of regular earthquakes suggesting that tremor can be analyzed using standard spectral models prior analyses that have shown a tremor spectral falloff proportional to f 1 may reflect only the spectral behavior over a limited frequency band 2 tremor may be no different from a swarm of microearthquakes with abnormally small stress drops on the order of kpa likely due to the presence of fluids alternatively the low corner frequencies of tremor may reflect abnormally slow ruptures 3 fitting a standard brune 1970 spectral model implies a moment release rate of cascadia tremor of 3 8 1010 n m s assuming the tremor signals are p waves or 1 4 1010 n m s assuming s waves this implies that a typical 20 day long tremor episode releases moment equivalent to mw 5 1 p wave or mw 4 9 s wave although these may be underestimates if the spectra deviate substantially from the brune model at very low frequencies

moments magnitudes and radiated energies of non volcanic tremor near cholame ca from ground motion spectra at upsar 1 by averaging the spectra of events within two episodes of tremor on jan 21 and 24 2005 across the 12 stations of upsar we improved the s n sufficiently to define source spectra analysis of eleven impulsive events revealed attenuation corrected spectra of displacement similar to those of earthquakes with a low frequency plateau a corner frequency and a high frequency decay proportional to f 2 seismic moments m0 estimated from these spectra range from about 3 to 10 1011 n m or moment magnitudes in the range 1 6 to 1 9 the corner frequencies range from 2 6 to 7 2 hz and if interpreted in the same way as for earthquakes indicate low stress drops that vary from 0 001 to 0 04 mpa seismic energies estimated from the ground motion spectra vary from 0 2 105 to 4 4 105 j or apparent stresses in the range 0 002 to 0 02 mpa the low stress parameters are consistent with a weak fault zone in the lower crust at the depth of tremor in contrast the same analysis on a micro earthquake located near cholame depth 10 3 km revealed a stress drop of 0 5 mpa and an apparent stress of 0 02 mpa residual spectra from 2 model fits to the displacement spectra of the non volcanic tremor events show peaks near 4 hz that are not apparent in the spectra for the microearthquake nor for the spectrum of earth noise these spectral peaks may indicate that tremor entails more than shear failure reminiscent of mechanisms possibly entailing fluid flow associated with volcanic tremor or deep volcanic earthquakes

analysis of nonvolcanic tremor on the san andreas fault near parkfield ca using u s geological survey parkfield seismic array 1 reports by nadeau and dolenc 2005 that tremor had been detected near cholame valley spawned an effort to use upsar u s geological survey parkfield seismic array to study characteristics of tremor upsar was modified to record three channels of velocity at 40 50 sps continuously in january 2005 and ran for about 1 month during which time we recorded numerous episodes of tremor one tremor on 21 january at 0728 was recorded with particularly high signal levels as well as another episode 3 days later both events were very emergent had a frequency content between 2 and 8 hz and had numerous high amplitude short duration arrivals within the tremor signal here using the first episode as an example we discuss an analysis procedure which yields azimuth and apparent velocity of the tremor at upsar we then provide locations for both tremor episodes the emphasis here is how the tremor episode evolves twelve stations were operating at the time of recording slowness of arrivals was determined using cross correlation of pairs of stations the same method used in analyzing the main shock data from 28 september 2004 a feature of this analysis is that 20 s of the time series were used at a time to calculate correlation the longer windows resulted in more consistent estimates of slowness but lower peak correlations these values of correlation peaks of about 0 25 however are similar to that obtained for the s wave of a microearthquake observed peaks in slowness were traced back to source locations assumed to lie on the san andreas fault our inferred locations for the two tremor events cluster near the locations of previously observed tremor south of the cholame valley tremor source depths are in the 14 24 km range which is below the seismogenic brittle zone but above the moho estimates of error do not preclude locations below the moho however the tremor signal is very emergent but contains packets that are several times larger than the background tremor signal and lasts about 5 s these impulsive wavelets are similar to low frequency earthquakes signals seen in japan but appear to be broader band rather than just higher in low frequency energy they may be more appropriately called high energy tremor het het signals at upsar correlate well with the record of this event from station ghib of the hrsn borehole array at parkfield and hets typically have a higher cross correlation coefficient than the rest of the tremor event the amplitudes of a large het are consistent with a magnitude of 0 1 when compared with a m2 3 event that had about the same epicenter polarizations of the tremor episode at upsar are mostly just north of east both linearity and azimuth evolve over time suggesting a change in tremor source location over time and linearity is typically higher at the hets

is climate variability over the north pacific a linear response to enso abstract indices of the dominant spatial patterns of wintertime northern hemisphere 500 mb height and north pacific sea surface temperature are strongly correlated with one another on interannual and interdecadal timescales and both am correlated with indices of the el nin southern oscillation one possible interpretation of these relationships is that the tropical sst anomalies associated with enso force the atmospheric circulation over the north pacific and these atmospheric anomalies in turn give rise to the observed sst anomalies over the extratropical north pacific in this study linear relationships between enso and extratropical variables are examined in two different ways first the component of the observed extratropical variability that is linearly dependent upon enso is removed the dominant spatial patterns in the residual variability of 500 mb height and sst anomalies over the north pacific are shown to be similar to their counterparts in the total fields and remain strongly coupled on

a regional index of northeast pacific variability based on satellite altimeter data 1 an index of climate variability to monitor the state of the upper ocean is proposed for the northeast ne pacific ocean based on sea surface height ssh data from satellite altimetry while sea surface temperature sst is often used characterize ocean variability ssh reflects the integrated influence of temperature and salinity anomalies through the water column a canonical correlation analysis shows that ssh and sst anomalies vary coherently at large spatial scales and low frequencies over the region ssh anomalies are less subject to short period variability and the temporal components for ssh resemble smoothed low pass filtered versions of the sst components also examined is the relationship between the sst based pacific decadal oscillation pdo index and the large scale upper ocean variability reflected in the leading principal component of ssh anomalies the comparison demonstrates that the ssh principal component provides a robust index of regional climate variability that is less noisy than the pdo the results are used to examine the 1998 2002 climate event over the ne pacific

contamination risk assessment of fresh groundwater using the distribution and chemical speciation of some potentially toxic elements in calabar southern nigeria the computer program phreeqc was used to determined the distribution chemical speciation and mineral saturation indices in a fresh groundwater environment with limited mining activities in the adjoining areas the aim was mainly to determine the potential risk of a coastal plain aquifer contamination by some potentially toxic elements the results show that the elements ba cd cu fe mn ni rb sr and zn are distributed as free metal ions arsenic is in the neutral form of h3aso3 o while three species of aluminium al3 aloh2 al oh 2 dominate the major species of uranium include uo2co3 uo22 uo2 and uo2oh respectively in order of abundance the groundwater is saturated with respect to alunite kal3 so4 2 oh 6 basaluminite al4 oh 10 so4 boehmite al oh cu metal cu cuprous ferrite cufeo2 diaspore alo oh gibbsite al oh 3 goethite feooh hematite fe2o3 magnetite fe3o4 and uraninite uo2 most of the species are not mobile under the prevailing ph 3 3 to 5 9 and eh 7 to 158 mv conditions the mobile ones are very low in concentration and will be immobilized by precipitation of mineral phases the study concludes that presently these species do not pose any risk to the aquifer

spatiotemporal variability of interdecadal sea level oscillations in the north pacific 1 the interdecadal variations in the north pacific sea level field were investigated on the basis of two historical tide gauge data sets long term sea level records spanning 100 years but spatially limited in the midlatitudes the cl data set and records from a wider area but with a data length of about 50 years the hcl data set a seesaw like sea level oscillation between the eastern and the western pacific was extracted as the first mode of empirical orthogonal functions eof from the cl data set this mode shows a 22 5 year period of variation that has continued throughout the 20th century a similar variation was found in the hcl data set as the first mode of complex eof ceof though its dominant period was 14 5 years this interdecadal sea level oscillation is the steric sea level change associated with the pacific inter decadal oscillation pdo in the upper ocean temperature field because the temporal evolution and spatial structure in the interdecadal oscillation resemble those of the dominant modal pattern in the temperature field however this mode shows a standing wave characteristic in the midlatitudes rather than propagating though the clockwise phase propagation around the subtropical gyre has been reported in the temperature field another interdecadal oscillation is found in the ceof second mode which was dominant in the 1960s when the first mode was relatively weak the second mode shows a 15 to 16 years period of variation and phase lags of 3 4 years at the subtropical stations relative to those in the midlatitudes

trace element geochemistry in the upper amazon drainage basin bolivia abstract the distribution of trace elements sr mo ba rb u mn ni cu zn and cd was investigated in surface waters and associated particulates in two upper amazonian basins mamore and beni dissolved sr ba mo rb u and to a lesser extent zn and cd correlate with major ions and appear to be predominantly derived from soluble rocks carbonates evaporites or sulfides essentially contained in shales these elements are conservative in waters except in highly alkaline or sulfate rich waters where calcite and barite can precipitate the concentrations of transition element are generally not correlated with major ion chemistry their behaviour can be largely explained by equilibrium reactions in solution and solid liquid exchanges additionally the distribution of mn and cu reflects also the lithological differences between the mamore and beni basins the occurrence of mineralisation in the beni basin explains the high zn cd as well as the concentrations of cu in some rivers of the beni basin the higher content of mn in the mamore basin may reflects the predominance of carbonate rocks the fractionation of trace elements in spm has been attributed to the sorting of feldspars during transport in water and to the mixing between clay minerals and quartz these minerals refractory to weathering and introduced in water rivers by mechanical erosion have not contributed to the dissolved load

an integrated perspective of the continuum between earthquakes and slow slip phenomena slow slip a mechanism by which faults can relieve stress was thought to be distinct from earthquakes however a global review of slow slip phenomena suggests that instead there is a continuum between the two types of event

quantifying the time function of nonvolcanic tremor based on a stochastic model 1 nonvolcanic tremor is the seismically observable component of slow earthquakes which have been recently discovered in subduction zones around the world including major study areas at the nankai and cascadia subduction zones although tremor appears to occur randomly in both areas cascadia tremor has a longer duration than nankai tremor in the present study this difference in tremor duration is quantified using a brownian slow earthquake model that explains several features of tremor and slow earthquakes a previous brownian model is improved and applied to explain the cumulative distribution function of tremor amplitude which is approximated by a 2 distribution the model also shows that the power spectrum of tremor amplitude has a simple analytic formula including a characteristic time an inversion method is developed to measure the characteristic time from the tremor spectrum in the presence of non gaussian background noise the method is applied to several tremor sequences in the nankai and cascadia subduction zones to quantitatively confirm the apparent differences in tremor behavior between the two areas the constants for cascadia and nankai tremor are 1000 3000 s and 100 1000 s respectively with temporal increases in these values observed over the course of 1 day records of activity the difference in characteristic time between the two areas may reflect geometric constraints such as the width of the tremor region