global sea level rise published values for the long term global mean sea level rise determined from tide gauge records exhibit considerable scatter from about 1 mm to 3 mm yr this disparity is not attributable to instrument error long term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year instead the differing estimates of global sea level rise appear to be in large part due to authors using data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends in addition virtually all gauges undergo subsidence or uplift due to postglacial rebound pgr from the last deglaciation at a rate comparable to or greater than the secular rise of sea level modeling pgr by the ice 3g model of tushingham and peltier 1991 and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records the value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880 1980 is 1 8 mm yr 0 1 this result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality

detailed observations of california foreshock sequences implications for the earthquake initiation process we find that foreshocks provide clear evidence for an extended nucleation process before some earthquakes in this study we examine in detail the evolution of six california foreshock sequences the 1986 mount lewis ml 5 5 the 1986 chalfant ml 6 4 the 1986 stone canyon ml 4 7 the 1990 upland ml 5 2 the 1992 joshua tree mw 6 1 and the 1992 landers mw 7 3 sequence typically uncertainties in hypocentral parameters are too large to establish the geometry of foreshock sequences and hence to understand their evolution however the similarity of location and focal mechanisms for the events in these sequences leads to similar foreshock waveforms that we cross correlate to obtain extremely accurate relative locations we use these results to identify small scale fault zone structures that could influence nucleation and to determine the stress evolution leading up to the mainshock in general these foreshock sequences are not compatible with a cascading failure nucleation model in which the foreshocks all occur on a single fault plane and trigger the mainshock by static stress transfer instead the foreshocks seem to concentrate near structural discontinuities in the fault and may themselves be a product of an aseismic nucleation process fault zone heterogeneity may also be important in controlling the number of foreshocks i e the stronger the heterogeneity the greater the number of foreshocks the size of the nucleation region as measured by the extent of the foreshock sequence appears to scale with mainshock moment in the same manner as determined independently by measurements of the seismic nucleation phase we also find evidence for slip localization as predicted by some models of earthquake nucleation

testing a model of earthquake nucleation abstract some laboratory models of slip find that a critical amount or velocity of slow slip is required over a nucleation patch before dynamic failure begins typically such patch sizes when extrapolated to earthquakes have been thought to be very small and the precursory slip undetectable ohnaka 1992 1993 has proposed a model in which foreshocks delineate a growing zone of quasi static slip that nucleates the dynamic rupture and suggests that it could be large enough 10 km across to be detectable and thus useful for short term earthquake prediction the 1992 landers earthquake m 7 3 had a distinctive foreshock sequence and initiated only 70 km from the strain meters at the pinon flat observatory pfo we use this earthquake to investigate the validity and usefulness of ohnaka9s model the accurate relocations of dodge et al 1995 show that the foreshock zone can be interpreted as expanding from an area of 800 m along strike by 900 m in depth to 2000 by 3200 m in the 6 5 hr before the mainshock we have calculated the deformation signals expected both at pfo and 20 km from the foreshock zone assuming either constant slip or constant stress drop on a circular patch expanding at 5 cm sec over 6 5 hr we find the slips or stress drops would have to have been implausibly high meters or kilobars to have been detectable on the strain meters at pfo slightly better limits are possible only 20 km from the source even though the distance from landers to pfo is small compared with the average spacing of strain meters in california we are unable to prove or disprove ohnaka9s model of earthquake nucleation this suggests that even if the model is valid it will not be useful for short term prediction

sourcing geochemically identical obsidian multiscalar magnetic variations in the gutansar volcanic complex and implications for palaeolithic research in armenia abstract in obsidian rich armenia one of the most archaeologically significant obsidian resources is the gutansar volcanic complex gvc numerous palaeolithic sites across armenia consist of little more than deposits of obsidian tools and debris and within the hrazdan gorge the vast majority of artifacts is crafted from gvc obsidian for example about 93 of the lithic assemblages from the lower palaeolithic site of nor geghi 1 and the middle palaeolithic site of lusakert cave 1 are gvc obsidian although erupted from multiple volcanic centers gvc obsidians are geochemically identical and cover an area more than 70 km2 for studies seeking to reconstruct movements of palaeolithic hunter gatherers throughout the local landscape the expansive gvc is problematic geochemically identical obsidians dominate the foraging territories of sites within and near the complex here we explore the potential of obsidian magnetic properties to reveal hitherto unobservable patterns in gvc obsidian utilization with the ultimate goal of elucidating palaeolithic behavioral patterns our results show that magnetic properties vary over multiple scales within the gvc allowing obsidian sourcing to become multiscalar these measurements are rapid inexpensive and entirely nondestructive for small artifacts measuring a few basic magnetic properties enables us to distinguish geochemically identical obsidians from three eruptive centers and potentially to attribute artifacts to specific quarrying sites recognize changes in provisioning strategy and estimate a minimum number of cores represented by a lithic scatter

a viscoelastic coupling model for the cyclic deformation due to periodically repeated earthquakes at subduction zones vertical displacements due to periodic reverse faulting events in an elastic plate overlying a viscoelastic maxwell half space are obtained and compared with the observed deformation cycle coseismic strain release postseismic transients interseismic strain accumulation from japan the viscoelastic effects including the influence of buoyant restoring forces are obtained using the method developed by rundle and plate convergence and strain accumulation are incorporated following the procedure suggested by savage the resulting deformation cycle is compared with that of an analogous elastic half space dislocation model in which postearthquake effects are due to transient aseismic slip below the coseismic fault cyclic deformation is similar but not identical for the two models and observations from southwest japan suggest the superiority of the viscoelastic coupling model in particular inclusion of the effects of steady state flow in the asthenosphere overcomes a defect of the elastic half space model and results in agreement with the observed interseismic movement pattern several aspects of the postseismic deformation its landward migration and its transition to the interseismic phase of the cycle are explained as well but the short duration of near trench transients relative to those observed farther inland is not matched the success of a buried slip model in explaining early postseismic near trench movements and asthenospheric flow in accounting for cumulative postearthquake transient motions suggests the existence of a transition zone between lithosphere and asthenosphere whose behavior is brittle elastic in the short term and ductile for longer term deformation and such a modification may reconcile remaining discordant observations however reasonable variations in coupling model parameters cannot account for observed differences in the deformation cycle in other parts of japan and these regional differences remain unexplained

the estimation of global sea level change a problem of uniqueness an objective method of estimating regional averages of coherent sea level sl change is developed the technique is applied to a large set of sl data representative of most of the world s continental margins the results show highly coherent sl changes over many of the regions studied the method is then applied to the regional averages themselves to develop an overall estimate of the coherent pattern of sl variations existing in the historical sl data set the pattern is characterized by a coherent rise of sl in all regions except alaska scandinavia both areas of notorious crustal uplift and southeast asia where sl appears to be falling the analysis suggests little or no change in sl prior to the early 1900 s the period since that time has seen an increase in sl that is optimally fit by a linear trend of 23 cm century the study results suggest that it is not possible to uniquely determine either a global rate of change of sl or even the average rate of change associated with the existing inadequate data set indeed different analysis methods by themselves can cause 50 variations in the estimates of sl trend in the existing data set a signal noise analysis suggests it should be easy to detect small future changes in the sl trends estimated for the period 1930 1980 however detection of theoretically predicted low frequency signals e g caused by co2 warming will be difficult in view of the huge low frequency natural variability associated with glacial tectonic processes

seismicity faulting and structure of the koyna warna seismic region western india from local earthquake tomography and hypocenter locations although seismicity near koyna reservoir india has persisted for 50 years and includes the largest induced earthquake m 6 3 reported worldwide the seismotectonic framework of the area is not well understood we recorded 1800 earthquakes from 6 january 2010 to 28 may 2010 and located a subset of 343 of the highest quality earthquakes using the tomodd code of zhang and thurber 2003 to better understand the framework we also inverted first arrivals for 3 d vp vs and vp vs and poisson s ratio tomography models of the upper 12 km of the crust epicenters for the recorded earthquakes are located south of the koyna river including a high density cluster that coincides with a shallow depth 1 5 km zone of relatively high vp and low vs also high vp vs and poisson s ratios near warna reservoir this anomalous zone which extends near vertically to at least 8 km depth and laterally northward at least 15 km is likely a water saturated zone of faults under high pore pressures because many of the earthquakes occur on the periphery of the fault zone rather than near its center the observed seismicity velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main fault zone due to high pore pressure we interpret our velocity images as showing a series of northwest trending faults locally near the central part of warna reservoir and a major northward trending fault zone north of warna reservoir

five decades of triggered earthquakes in koyna warna region western india a review abstract we review reservoir triggered seismicity rts in the koyna warna region of india since the impoundment of the koyna reservoir in 1962 until the year 2015 we include seismicity that occurred farther south in response to the impoundment of warna reservoir in 1993 about 35 km to the south of koyna reservoir the on going earthquake activity for more than five decades in a small seismic volume of about 30 20 10 km3 has characterized the koyna warna region as globally unique and significant to date 22 earthquakes of m 5 about 200 earthquakes of m 4 and several thousand smaller earthquakes have been recorded by a dense network of stations in the region various seismological geophysical and hydrological studies have been carried out to understand the phenomenon of triggered seismicity including source mechanism fault geometry crustal structure earthquake processes causal relationship with reservoir water level changes and anomalous water level fluctuations in cased bore wells the present review takes stock of all such studies undertaken so far to summarise the understanding on various geo scientific issues and milestone achievements with regard to mechanism of triggered seismicity and source processes fault plane solutions commensurate with geometry of faulting source parameters seismogenic depth crustal structure and the role of reservoir water level two stage increase in seismic energy release coinciding with peaks of annual filling and draining cycle of reservoir with one month delay vis a vis spurt of moderate earthquakes m 5 due to i rapid rise in reservoir level 12 m week ii reservoir water level exceeding the previous maxima and iii duration for which high reservoir level is retained are characteristic features numerical models simulating diffusion of pore fluid pressure fronts during the filling stage of reservoir suggest stress perturbations of the order of 0 75 2 25 bar at hypocentral depth triggering earthquakes on critically stressed pre existing faults in the year 2005 a 13 station digital seismometers network became functional that characterized the distribution of epicentres in the area with increased accuracy and suggested four major seismic zones with well defined clusters scientific drilling carried out recently provide several new information regarding the subsurface geology and structure in the koyna region such as i thickness of deccan traps 933 in the koyna area and 1185 m in the warna area ii presence of granite gneiss basement directly underlying the deccan traps iii absence of infratrappean sediments and iv temperature not exceeding 150 c at hypocentral depth it is planned to establish a deep borehole observatory close to the seismic source zone for direct measurements of physical and mechanical properties of rocks pore fluid pressure hydrology thermal condition and other parameters of an intra plate active fault zone in the near field of earthquakes before during and after their occurrence results from such experiment and long term in situ monitoring of critical parameters would enhance our understanding on the mechanism of triggered earthquakes and the role of reservoir water level fluctuations

environment and collapse eastern anatolian obsidians at urkesh tell mozan syria and the third millennium mesopotamian urban crisis the early to middle bronze age transition in northern mesopotamia has received great attention for the apparent concurrence of aridification deurbanisation and the end of the akkadian empire around 2200 bce our understanding of the crisis has been almost exclusively shaped by ceramics demography and subsistence exchange and the associated social networks have been largely neglected here we report our sourcing results for 97 obsidian artefacts from urkesh a large urban settlement inhabited throughout the crisis before the crisis six obsidian sources located in eastern anatolia are represented among the artefacts such a diversity of eastern anatolian obsidians at one site is hitherto unknown in mesopotamia it implies urkesh was a cosmopolitan city with diverse visitors or visitors with diverse itineraries during this crisis however obsidians came from only two of the closest sources two to three centuries passed before varied obsidians reappeared even when an obsidian source reappears the raw material seems to have come from a different collection spot we discuss the likely exchange mechanisms and related social networks responsible for the arrival of obsidians at urkesh and how they might have changed in response to climatic perturbations and regional government collapse

earthquake source nucleation a physical model for short term precursors abstract ohnaka m 1992 earthquake source nucleation a physical model for short term precursors in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 149 178 this paper deals with a quasistatic leading to a quasidynamic at a later time nucleation process that precedes the earthquake dynamic rupture and models of the earthquake source nucleation are put forward based on physical principles a quasistatic to quasidynamic rupture nucleation process is an intrinsic part of the ensuing earthquake dynamic rupture in other words the nucleation process itself is an short term or immediate precursor that occurs in a localized zone during the earthquake nucleation premonitory slip proceeds in the localized nucleation zone and shear stress also decreases gradually in the zone since slip weakening occurs during the nucleation immediate foreshock activity is a part of the nucleation process leading to the mainshock dynamic rupture therefore hypocentral locations of foreshocks are necessarily restricted to lie near the mainshock hypocentre onset of the mainshock rupture whether or not foreshocks occur during the mainshock nucleation depends on how the rupture growth resistance varies on a local to small scale since patches of greater rupture growth resistance are considered to prevail on a local to small scale in the fault zone carrying immediate foreshocks would be one of the major characteristics of earthquakes that nucleate within the brittle seismogenic layer when a mainshock earthquake nucleates within the brittle seismogenic layer and its hypocentre is located near the base of the seismogenic layer immediate foreshocks for this mainshock are necessarily restricted to lie within a localized region shallower than hypocentral depth of the mainshock by contrast the nucleation process below the base of the seismogenic layer is aseismic in nature so that carrying no conspicuous foreshocks would be a common characteristic of interplate earthquakes that nucleate below the base of the brittle seismogenic layer the breakdown strength p the breakdown stress drop b and the critical slip displacement dc are indicative of the rupture growth resistance to estimate depth variations of these parameters the effects of the normal stress n and temperature t on those parameters are examined using available data so far published the combined effects of n and t on p in the brittle to semibrittle regime are found to be represented empirically by p n t po n 1 cosh 50 t 40 sinh 50 t exp 2000 t where po n 135 7 0 750 n and t is measured in k and n in mpa it is found that dc increases sharply with t but is insensitive to n above 300 c while dc depends on n but is insensitive to t below 300 c on the basis of these results variations in p dc and b at mid crustal depths are estimated for quartzo feldspathic rocks for a given geothermal gradient

relative sea levels of japan from tide gauge records we attempted to separate tectonic ocean ographic and eustatic components of change in relative sea levels derived from the many tide gauge records of japan acquired during the past 50 yr a modified eigenanalysis permitted use of station data of unequal lengths regression analysis and eigenanalysis revealed systematic spatial differences in relative sea level rise of 25 mm yr although the difference is too great to be solely eustatic in origin data are insufficient to permit accurate separation of tectonic and eustatic effects on relative sea levels the low frequency patterns periods longer than 50 yr may have been derived from subduction of the pacific and philippine plates beneath japan higher frequencies 12 6 and 2 yr periods are correlated with oceanographic factors such as shifts in the position of the kuroshio and the el nino southern oscillation the contours of relative change in sea levels provide convincing evidence that neither a single nor several japanese tide gauges can be selected to authentically demote present or past eustatic sea level rise

tongan and samoan volcanic glass pxrf analysis and implications for constructs of ancestral polynesian society a provenance study of volcanic glass specimens from 12 archaeological sites in the kingdom of tonga is carried out employing pxrf portable x ray fluorescence analysis to accomplish this volcanic glass samples from previously identified sources in northern tonga and the adjacent islands of samoa are analyzed results indicate inter island voyaging and interaction over a 600 km linear distance along the tongan island chain from first lapita settlement ca 2900 bp throughout later prehistory tongan volcanic glass however is not found in samoa and with the exception of one late prehistoric specimen samoan volcanic glass is not present in tonga this distribution challenges current concepts of an integrated ancestral society and homeland common to tonga and samoa from the lapita period onward

earthquake precursory studies in india scenario and future perspectives earthquakes are the worst natural calamities that strike without any notice and cause immediate loss of life and property internationally serious and scientifically acceptable earthquake prediction studies started in 1970s and short term prediction of the heicheng earthquake of february 4 1975 in china is a land mark in india a successful medium term prediction of august 6 1988 earthquake m 7 5 in northeast indian region encouraged to intensify such studies in the country these predictions were based mainly on seismological precursors initially the precursory studies were taken in isolated manner but after validation of specific geophysical parameters efforts were made to adopt an integrated approach involving collection analysis and interpretation of various precursory observations in a comprehensive and coordinated manner accordingly a few multi parametric geophysical observatories mpgos have been established at the selected locations in seismically active areas in the country this approach led to successful short term prediction of some moderate earthquakes m p 4 in koyna region famous for reservoir triggered seismicity in western india simultaneously efforts have been made to generate long term multi parametric observations from these observatories as a basic scientific input required for future earthquake prediction related studies the real time analysis of these data sets would help to understand the earthquake generation process and attaining the predictive capabilities by developing models for short term earthquake forecasting to facilitate direct observations and test the hypothesis of reservoir triggered seismicity rts as well as to understand the earthquake generation processes it is planned to undertake deep borehole 6 8 km investigations in koyna region of western india the paper highlights the efforts made so far in india in the area of earthquake precursory studies as well as the future road map

the earthquake deformation cycle at the nankai trough southwest japan geodetic measurements made landward of the nankai trough site of great subduction zone thrust earthquakes in 1854 and 1946 provide a uniquely detailed picture of the strain buildup process supply constraints on the mechanism of strain accumulation and allow for improved estimates of earthquake recurrence provided the two most recent movement cycles are similar the observations dating from about 1890 may be used to reconstruct a single complete deformation cycle coseismic strain release postseismic transients interseismic strain accumulation very complete leveling and tidal gage data indicate that postseismic deformation extends more than 300 km inland from the plate boundary persists for at least 30 years and shows a clear tendency to become longer wavelength with increasing time the transient movements have two timescales the first of about a year or less corresponds to deformation largely uplift concentrated close to the coseismic fault and is most easily explained by aseismic slip or very localized deformation downdip of the earthquake rupture plane the second longer timescale is associated with a diffusion like spread of the deformation further landward an effect qualitatively similar to that first predicted by elsasser to be an expected consequence of faulting in an elastic plate overlying a viscoelastic asthenosphere cumulative uplift since 1890 correlates well with the distribution of uplifted marine terraces although average post 1890 tilt rates exceed late quaternary and holocene averages by at least a factor of three because of the nonlinearity of strain buildup and the significant permanent deformation simple recurrence calculations typically overestimate the true interval between great earthquakes by a factor of 2 to a factor of 3 strict application of the time predictable model assumed correct overcomes these difficulties provided the cumulative transient deformation and the proportion of permanent deformation per cycle can be estimated

ocean signals in tide gauge records tide gauges are designed to measure changes in water level relative to land however vertical motions of the earth s crust manifest themselves as apparent water level changes in tide gauge records these crustally induced changes are often small in amplitude relative to the wide range of oceanic processes which affect water level in coastal regions vertical crustal motion can best be studied by first removing oceanic variability from the time series in this paper we summarize the major oceanic signals in tide gauge records we take the approach that the oceanic signals are unwanted noise in the data methods are described for removing or at least reducing the various oceanic signals these oceanic signals span a broad range of time scales from tides to interannual variability associated with the el nino phenomenon and secular sea level change from a number of oceanographic effects

moving sources a preliminary study of volcanic glass artifact distributions in northeast china using pxrf recent studies have highlighted the long distance transport of obsidian from the paektusan tianchi or baitoushan in chinese volcano on the border between china and north korea to eastern russia and korea but little is known about the role of the local population in the production and movement or exchange of this important raw material this paper addresses this data lacuna by presenting sourcing results of 440 artifacts from 18 late paleolithic sites located in northeast china a portable xrf enabled rapid non destructive characterization of samples the results show that although paektusan obsidian was widely transported throughout northeast asia material from at least three other sources was also used in particular we highlight the significance of basaltic glass artifacts with the same geochemistry as sources found in the primorye region of far east russia in sites from northeast china this result indicates a two way movement of volcanic glass artifacts between primorye and the northeast of china rather than a unidirectional long distance exchange system originating from paektusan volcano

tide gage measurements of uplift along the south coast of alaska annual mean sea levels along the south coast of alaska are used to measure uplift along the alaska aleutian subduction zone oceanographic effects are removed from the observed annual mean sea levels by subtracting a correction that is proportional to the sea level fluctuations observed in southeast alaska that correction is effective in reducing fluctuations in the observed annual mean sea level as far west as the tip of alaska peninsula additional corrections to remove the eustatic rise in sea level and the apparent fall in sea level due to postglacial isostatic rebound of the land are introduced this corrected sea level record should provide a measure of tectonic subsidence in the area affected by the 1964 alaska earthquake postseismic uplift occurs where coseismic subsidence was observed and postseismic subsidence occurs where coseismic uplift was observed the immediate postseismic response is damped out within the first decade and the subsequent uplift rates appear to be steady over the 1974 1989 interval however some of those rates seem to be too high to be sustained over the 1000 year earthquake recurrence interval appropriate to this area if the interseismic deformation is only to recover the coseismic displacement thus a long term 100 years relaxation in uplift rates is postulated the immediate time constant 5 years postseismic relaxation is attributed to postseismic slip on the plate interface directly downdip from the coseismic rupture the long term time constant 100 years relaxation is attributed to flow in the asthenosphere

ten seconds in the field rapid armenian obsidian sourcing with portable xrf to inform excavations and surveys armenia has one of the most obsidian rich natural and cultural landscapes in the world and the lithic assemblages of numerous palaeolithic sites are predominantly if not entirely composed of obsidian recent excavations at the middle palaeolithic cave of lusakert 1 recovered on average 470 obsidian artifacts daily after sourcing more than 1700 artifacts using portable xrf pxrf in our field house our team sought to shift pxrf based obsidian sourcing into the field itself believing that the geological origins of artifacts would be useful information to have on site during an excavation or survey despite increasing use of portable instruments previous studies have principally focused on collections in museums and other archives and as a result obsidian sourcing has remained embedded in post excavation studies one critical factor in the uptake of obsidian sourcing in the field is the time needed to measure each artifact frequently 2 6 min in previous studies here we report our two methods of obsidian sourcing including source matching done automatically by the pxrf instrument s onboard software in only 10 s our tests with armenian geological specimens and palaeolithic artifacts demonstrate the high efficacy of our two methods which are sufficiently fast to become syncopated with our excavation and survey activities by reducing measurement times from a mode of 300 s in recent studies to just 10 s here we show how and why to shift pxrf based obsidian sourcing from the context of white lab coats to that of muddy boots

pxrf characterisation of obsidian from central anatolia the aegean and central europe the obsidian sources of central anatolia the aegean and central europe have been studied in detail over the past 50 years various analytical techniques have been employed to discriminate artefacts from each of these and to reconstruct their zones of distribution this paper presents a pxrf method that allows mass sampling of artefacts focusing on three neighbouring regions particularly where these zones overlap successful discrimination of the obsidian source for products could be achieved using three dimensional scatter plots of trace elements rb sr zr pxrf can thus be appreciated as a powerful tool in the region enabling non destructive on site analyses in contexts where the export of artefacts is often difficult if not impossible the ability to rapidly process large assemblages also has major implications for generating data sets of sufficient resolution to transform archaeological interpretation

source parameters of koyna earthquakes india abstract a seismic zone in southwestern india extending 30 km south from koyna dam has witnessed more than 150 earthquakes of m 4 and 10 of m 5 during the last 34 years during august 1993 to december 1994 a spurt of earthquakes occurred in the vicinity of the newly impounded warna reservoir 25 km south of koyna dam the epicenters are located between the two reservoirs but more near the new reservoir during 1994 digital data acquisition systems were deployed by the national geophysical research institute in the vicinity of the koyna warna reservoirs to help in understanding the physical processes responsible for generating earthquakes in the area source parameters were estimated at three stations using s wave spectrum for 193 selected earthquakes of m 1 5 to 4 7 that were recorded during october 1994 to june 1995 seismic moments of 10 11 to 10 16 n m source radii from 94 to 538 m and stress drops of 0 03 to 19 mpa for earthquakes of magnitude 1 5 to 4 7 were obtained from this analysis it is observed that earthquakes of m 3 are associated with larger stress drops of more than 2 mpa the larger energy release through more numbers of m 3 earthquakes and higher stress drop values are found in 0 to 1 km and 5 to 13 km depth ranges depth range of 1 to 4 km has low seismicity and low stress drop earthquakes higher energy release and stress drops are possibly caused by higher stress concentration and incremental stress on rocks with fluids in subhydrostatic conditions in 0 to 1 km depth range and suprahydrostatic conditions in 5 to 13 km depth range spatially the earthquakes of m 3 and high stress drop are now less near koyna reservoir but frequent near the new reservoir

equivalent strike slip earthquake cycles in half space and lithosphere asthenosphere earth models by virtue of the images used in the dislocation solution the deformation at the free surface produced throughout the earthquake cycle by slippage on a long strike slip fault in an earth model consisting of an elastic plate lithosphere overlying a viscoelastic half space asthenosphere can be duplicated by prescribed slip on a vertical fault embedded in an elastic half space for the case in which each earthquake ruptures the entire lithosphere thickness h the half space equivalent slip rate is as follows depth interval 0 h slip identical to that in lithosphere asthenosphere model i e abrupt coseismic slip and no subsequent slip depth interval 2n 1 h to 2n 1 h n 1 2 slip rate uniform in space and dependent upon time as fn t exp t a where fn is a n 1 degree polynomial in t a is twice the asthenosphere relaxation time and t is measured from the instant after the preceding earthquake the slip rate averaged over the seismic cycle in each depth interval equals the secular rate of relative plate motion for reasonable values of a slip rates below 5h do not vary much from that mean value and can be treated as constant thus the surface deformation due to the earthquake cycle in the lithosphere asthenosphere model can be calculated very simply from the half space model with time dependent slip in the two depth intervals h 3h and 3h 5h and uniform slip at a rate equal to the secular relative plate velocity below depth 5h inversion of 1973 1988 geodetic measurements of deformation across the segment of the san andreas fault in the transverse ranges north of los angeles for the half space equivalent slip distribution suggests no significant slip on the fault above 30 km and a uniform slip rate of 36 mm yr below 30 km one equivalent lithosphere asthenosphere model would have a 30 km thick lithosphere and an asthenosphere relaxation time greater than 33 years but other models are possible

a cost surface model of volcanic glass quarrying and exchange in hawai i abstract the spatial distribution of artifacts from the pu u wa awa a volcanic glass source north kona district hawai i island shows a pattern of direct access by those living in the immediately vicinity of the source with subsequent down the line exchange most quarrying and exchanges likely occurred within a single day s travel from sites where artifacts were deposited the exception to this is the discovery of non local direct access evident in assemblages from the extreme southern end of hawai i island these visits may have involved voyages by canoe while people did not often travel far for volcanic glass they nonetheless appear to have had unfettered accessed to source material and freely conducted inter community exchanges this implies volcanic glass was treated as a common pooled resource and the existence of informal exchange relationships

three dimensional seismic structure beneath southwest japan the subducting philippine sea plate abstract a three dimensional seismic structure beneath southwest japan has been investigated in detail by applying an inversion method this analysis clearly reveals the present and possibly the past subduction of the philippine sea plate beneath southwest japan beneath the izu peninsula the philippine sea plate does not appear to subduct but collides against the continental asian plate here and its thickness appears thinnest at most about 30 km from the tokai to the shikoku regions the high velocity zone corresponds well to the zone of subcrustal earthquakes down to a depth of about 60 70 km indicating that the subduction of the present philippine sea plate does not reach below this depth here however a small high velocity portion appears at depths between 100 km and 150 km beneath a part of the kinki region and probably extends to the chugoku region where no corresponding seismic activities exist these high velocities might be an indication of the remnants of the past subduction of the philippine sea plate in the kyushu region the high velocity zone continues down to a depth of about 150 km or even to 200 km in the southern part corresponding to a steeply inclined seismic zone the philippine sea plate in this region appears to be thicker than in regions east of the kyushu palau ridge it was also found that there exist narrow low velocity zones intervening within the philippine sea plate where two aseismic ridges the kyushu palau and shichito iwojima ridges extend northwards and the nankai trough shows warping these low velocity zones give support to the buoyant subduction hypothesis it also appears that lateral heterogeneities existing within and around the subducting plate are closely related to the mode of rupture of large earthquakes occurring around there

a dislocation model for the earthquake cycle at convergent plate boundaries summary a kinematic model for the earthquake cycle at convergent plate boundaries has been constructed on the basis of dislocation theory we model the lithosphere asthenosphere system by a stratified semi infinite medium under gravity consisting of an elastic surface layer an intervening layer with maxwell viscoelasticity and an elastic substratum the steady motion of plate convergence is naturally represented by uniform slip at a constant rate on the upper boundary of the descending oceanic plate the occurrence of interplate earthquakes is regarded as a perturbation of the steady state plate motion and represented by a periodic sequence of step slips on a finite seismic zone of the plate interface based on dislocation theory we can show that the steady slip on the interface deeper than the lithosphereasthenosphere boundary does not contribute to surface deformation in the steady state accordingly the surface deformation associated with the earthquake cycle is given by the superposition of viscoelastic responses to the steady slip on the interface shallower than the lithosphere asthenosphere boundary the steady backslip on the seismic zone and the periodic sequence of seismic slips we have computed cyclic patterns of vertical displacements at the free surface for two representative cases taking account of gravity effects the patterns of vertical displacements differ notably in the latter stage of the cycle depending on whether or not the seismic zone extends through the entire thickness of the lithosphere after the completion of one earthquake cycle our model yields a certain amount of permanent deformation resulting from the steady plate convergence the pattern of the permanent deformation that is characterized by steep uplift on the continental side sharp subsidence at the plate boundary and gentle uplift on the oceanic side is irrespective of the cyclic process of stress accumulation and release repeated on the seismic zone the earthquake cycle model developed here provides a possible explanation for the formation of earthquake origin marine terraces

characterization of new zealand obsidian using pxrf abstract new zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the north island in total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions shortly after colonization in the late 13th century ad polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the kermadecs and chatham islands although considerable research has been conducted on obsidian sourcing in new zealand the complexity of geochemical source discrimination and the lack of a practical method of non destructive geochemical analysis has hindered progress we present the results of our use of pxrf to provide geochemical data on new zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies a large case study using an important settlement phase site s11 20 from the auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of new zealand

secular and earthquake related vertical crustal movements in japan as deduced from tidal records 1951 1981 abstract monthly tidal records for the last 31 years from about 100 tidal stations are used to delineate vertical crustal movements in japan a new computer aided processing system was created for this purpose its principle is differential use of tidal records in a region so that the oceanographic disturbances of common causes may be eliminated from the sea level data this method enables us to observe nearly absolute vertical land movement at tidal stations with a precision of a few centimeters the japanese islands are divided into nine regions taking oceanographic conditions into account general discussion on recent vertical movements has yielded several notable features and trends as follows 1 1 rapid and stationary subsidence in the northeastern part of japan presumably of tectonic origin 2 2 a complex pattern of uplift and subsidence in the southwestern part of japan which seems to reflect subduction of the philippine sea plate against the honshu block 3 3 relatively stable land on the japan sea side of honshu movements related to the earthquakes during the period 1951 1981 are also discussed although few of the cases show clear cut premonitory movements if abnormal movements in a coastal area appeared with an amplitude exceeding 2 or 3 cm we could detect them by the present system

precursory changes in source parameters for the koyna warna india earthquakes summary precursory changes of stress drop and corner frequency are found for five main earthquakes of m w 4 1 to 4 7 that occurred near the koyna and warna reservoirs during the period of our close monitoring from 1994 onwards earthquakes had started to occur in the area in 1962 soon after the impoundment of the koyna reservoir and are still continuing the epicentres are located in a 30 km long n s seismic zone extending southwards from the koyna dam an ew warna reservoir situated 25 km south of koyna was filled to 60 m in 1992 most subsequent epicentres are close to the new warna reservoir most m 4 earthquakes in this region have been associated with foreshocks for 15 30 days and aftershocks for over a month at the beginning of various foreshock sequences of m w 1 5 to 2 4 the maximum stress drop values ranged from 0 25 to 0 65 mpa the corner frequency ranged from 7 0 to 10 0 hz for all the sequences the stress drops decreased by over 50 per cent of their maximum value during the precursory period of 4 17 days prior to main shocks and remained at that low level for a few days after the main shocks following an initial increase the corner frequency decreased by 8t o4 5per cent the decrease in corner frequency implies a 9 54 per cent increase in fault length and is inferred to be caused by increased pore pressure as a result of dilatancy

short term earthquake forecasting may be feasible at koyna india abstract reservoir triggered earthquakes have been occurring since the impoundment of shivaji sagar lake created by koyna dam in 1962 near the west coast of india over the past 38 years 15 earthquakes of magnitude 5 including the biggest reservoir triggered earthquake of m 6 3 on december 10 1967 and several hundred thousand smaller earthquakes have occurred we believe it is an ideal site for monitoring earthquake precursors which may lead to forecasts of m 5 earthquakes with adequate accuracy this optimism is based on the fact that here earthquakes occur in a small area of 30 km by 15 km and there are no other seismically active regions in the near vicinity the epicentral region is accessible for all kinds of experiments and observations and certain characters of koyna seismicity are quite well understood

testing the accuracy of portable x ray fluorescence to study aztec and colonial obsidian supply at xaltocan mexico abstract this article demonstrates the accuracy of non destructive portable x ray fluorescence p xrf for the study of obsidian in central mexico obsidian sources were identified for a sample of 103 artifacts from the site of xaltocan which spanned the rise and fall of the aztec empire and the first centuries of spanish colonial rule ad 900 1700 sources were assigned by comparing p xrf measurements with previously published source data and were verified using the standard techniques of laboratory xrf l xrf and instrumental neutron activation analysis inaa additional tests of potentially confounding factors show that neither length of read time presence of surface residue nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector our results provide new insight into the stability of supply networks and markets well into the colonial period as well as the homogenizing tendencies of the aztec market system

transient creep of a composite lower crust 2 a polymineralic basis for rapidly evolving postseismic deformation modes postseismic horizontal strain and displacement following the june 28 1992 landers california earthquake mw 7 3 is broad scale and cannot be explained solely by delayed afterslip located at the rupturing fault trace both the observed strain at pinon flat observatory pfo and observed global positioning system receiver velocities evolve rapidly after the landers big bear earthquake sequence the observed exponential decay of these motions with timescales of 4 34 days may reflect a soft creep rheology in the lower crust and brittle ductile transition zone or even within the seismogenic crust itself here a simple model of a two dimensional screw dislocation in a layered maxwell viscoelastic earth is employed in conjunction with a composite rheology to demonstrate that the short timescale transient response modes 4 34 days are consistent with the behavior of a biviscous lower crust the lowest viscosity of this system is derivable from laboratory experimental data on the long term creep of natural quarztites and the highest viscosity is consistent with isostasy related lower crustal flow in a continental extensional tectonic environment the model predicts significant stress relaxation at the base of the seismogenic crust near the base of the seismogenic zone and about 4 km away from the mainshock the rate of predicted relaxation is of the order of 0 01 mpa d 1 during the first 20 days of postseismic flow oblate spheroidal inclusions at 5 concentration levels that are both aligned and fairly flat in shape and that have a viscosity of 3 4 1015 pa s are consistent with both the amplitude and decay time of horizontal crustal strain observed at pfo after the landers mainshock it is speculated that the structures exposed in cross sections and in seismic reflection profiles of the lower crust that have mylonitic associations are in part the cause of such rapid postseismic evolution in southeastern california unmylonitized quartz rich rock at sufficiently elevated temperatures could also contribute to the rapid decay modes

hydrogeochemistry of the koyna river basin india hydrogeochemistry of the koyna river basin famous for the koyna earthquake magnitude 7 of 1967 has been studied basalt is the primary aquifer laterites alluvium and talus deposits form aquifers of secondary importance groundwater generally occurs under water table conditions in shallow aquifers deeper aquifers are associated only with basalts one hundred and 87 water samples were collected from various sources such as dugwells borewells springs and surface water including 40 samples for analysis of iron only major constituents were analyzed analyses show that the concentrations of ca2 exceed that of mg2 in almost all water samples the concentrations of na are generally next to ca2 and are always higher than that of k and co32 and so42 are very low and are often negligible groundwater in borewells tapping deeper aquifers has higher mineralization compared to that in dugwells representing shallow aquifers majority of the water samples are dominated by alkaline earths ca2 mg2 and weak acids hco3 co32 groundwater from shallow aquifers is generally calcium bicarbonate type 53 and calcium magnesium bicarbonate type 27 in case of deeper aquifer it is mostly calcium magnesium bicarbonate type 29 sodium bicarbonate type 24 calcium bicarbonate type 19 calcium magnesium sodium bicarbonate type 19 and sodium calcium bicarbonate type 9 groundwater water is generally fit for drinking and irrigation purposes except in the lower reaches of the koyna river basin which is affected by near water logging conditions

foreshocks and nucleation of small to moderate sized koyna earthquakes india rupture nucleation of five koyna mainshocks during 1993 to 1996 m 4 3 to 5 4 was studied using the space time patterns of foreshocks within 8 km and 500 hr prior to the mainshock the nucleation process occurred in two phases viz quasi static and quasi dynamic prior to the dynamic rupturing of the mainshock the foreshock nucleation zone is observed to grow at a rate of 0 5 to 10 cm sec until it finally attains a diameter of about 10 km before the occurrence of the mainshock it is found that the fracture nucleates at shallow depths 1 km and gradually deepens to cause the mainshock near the base of the seismogenic layer that is at about 8 to 11 km depth the nucleation of earthquakes at shallow depths may be attributed to the effect of increasing pore pressure caused by the reservoirs of koyna and warna dams in subhydrostatic conditions whereas the propagation of fractures toward the base of the seismogenic layer may be controlled by the local stress concentrations along the fault zone and pore pressure diffusion at greater depths

chemical and isotopic seismic precursory signatures in deep groundwater cause and effect abstract exploratory hydrochemical studies were initiated in koyna india to examine the chemical changes in the deep groundwater due to seismic activity 2 months before the occurrence of a m 5 1 earthquake on 14th march 2005 a few deep wells 100 250 m out of a dozen recorded hydrochemical anomalies induced by this earthquake and the anomalies continued for the next 3 months periodical hydrochemical data of one of the wells indicated a linear increase in cl so 4 2 f and depleted 18 o from august 2006 to march 2009 though there is no long term change in groundwater level except short duration seasonal change the observed linear change is hypothesised as an effect of aquifer response to seismic stress related to an impending earthquake of m 5 the observed temporal change in different chemical concentrations projected linearly to the levels of march 2005 and estimated the time of the impending earthquake the same as that of march 2005 event as 2011 12 further the time projection also made based on exponential increase in hydrochemistry after 3 2009 advanced the possible time window to 2010 11 this hypothesis was realized on 12 december 2009 with an earthquake of m 5 1 even the simple arithmetic mean of the 45 a earthquake m 5 history of koyna indicates a recurrence time of 5 4 a to account for the observed temporal hydrochemical changes a model based on mixing of two aquifer waters caused by seismic stress was proposed hourly monitoring of electrical conductivity ec of groundwater also recorded conductivity changes induced by the m 5 1 earthquake on 12th december 2009 a very important observation that emerges from this study is that the cyclic change in subsurface stress leads to earthquakes continuous monitoring of ec may be helpful in visualizing the effect of tectonic forces on groundwater chemistry

realising the potential of portable xrf for the geochemical classification of volcanic rock types abstract the ability to geologically classify stone artefact materials is crucial because it is the first step in provenance allocation and geochemical grouping that inform archaeological models used for understanding exchange systems within prehistoric social networks geochemical analyses have revolutionised exchange studies by making it possible to match stone artefacts back to quarry sources sometimes hundreds or thousands of kilometres away most archaeological basalt characterisation and provenance studies have relied on destructive sampling techniques to obtain the major trace elements nao2 k2o and sio2 wt to identify volcanic rock types on the total alkali silica tas diagram to overcome this limitation this paper presents an alternative method the pearce w f diagram that determines volcanic rock type and alkalinity using elements tio2 zr y and nb that are accurately detected by non destructive portable x ray fluorescence pxrf this new method is proven to be effective in a comparison with recent xrf archaeological basalt studies in the pacific the power to classify volcanic rock types non destructively with pxrf significantly increases the number of artefacts and museum objects available for inclusion in archaeological exchange studies

comparison of xrf and pxrf for analysis of archaeological obsidian from southern peru abstract chemical sourcing is becoming an increasingly important component of archaeological investigation instruments used for elemental analysis generally must be operated in a controlled laboratory environment further many methods require destruction of a small portion of the objects under investigation these facts inhibit the application of chemical sourcing studies in a number of research contexts use of portable non destructive instruments would resolve these issues sixty eight obsidian artifacts from the site of jiskairumoko in southern peru were examined by x ray fluorescence spectrometry xrf and portable x ray fluorescence spectrometry pxrf results were compared for consistency in terms of source determination and individual element concentrations both instruments determined that the same sixty six artifacts derived from the chivay obsidian source and both identified the same two artifacts that could not be assigned to source individual element comparisons showed significant differences but these can be resolved through instrument cross calibration and differences had no bearing on source identification pxrf was found suitable for determining obsidian sources in southern peru and for identifying specimens that require more sensitive analytical methods such as instrumental neutron activation analysis inaa regular use of chivay at jiskairumoko suggests consistent trade relationships developed during the archaic

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

establishing statistical confidence in cortex ratios within and among lithic assemblages a case study of the middle paleolithic of southwestern france abstract recent studies have demonstrated the usefulness of the cortex ratio for quantifying the cortex composition in lithic assemblages and as a viable index of prehistoric artifact transport yet the lack of means for assigning statistical confidence to archaeologically observed cortex ratios inhibits the approach s utility for objective comparisons and interpretation here we derive statistical confidence for archaeological cortex ratios through monte carlo and resampling techniques experimental data with known geometric properties and measured cortex values were employed as a reference for attaching a probability to an archaeological assemblage s cortex ratio the method is demonstrated on assemblages from the middle paleolithic sites of roc de marsal pech de l aze iv and combe capelle bas in southwestern france

lake bonneville constraints on lithospheric thickness and upper mantle viscosity from isostatic warping of bonneville provo and gilbert stage shorelines the deformed shorelines of the late pleistocene lake bonneville provide an excellent opportunity to analyze the response of the earth to surface loads of relatively short wavelengths 400 km and short duration 30 kyr recently revised estimates of the lake loading history and an expanded compilation of shoreline elevations for the bonneville 1550 m provo 1440 m and gilbert 1300 m shorelines have prompted us to reexamine the deflection the earth model we use is identical with that employed by nakiboglu and lambeck and consists of an elastic plate overlying a maxwell viscoelastic channel and a rigid base our calculation differs from that of nakiboglu and lambeck in two respects we used a significantly more detailed load model and we compared our results with observations from three distinct shorelines the lake elevation history spans 32 kyr in 18 piecewise linear segments the water load is computed at each time step from a digital terrain model 4 4 km cell size and a specified lake elevation we find that the use of three separate shorelines significantly reduces the acceptable region of parameter space the effective elastic lithospheric thickness is 23 2 km the mantle viscosity is 1 2 0 2 1020 pa s and the depth to a significant viscosity increase is no less than 300 km though it might be much more examination of the residual deflections differences between observed and computed shoreline elevations reveals a regional tilt down to the ne of 6 10 5 which we attribute to collapse of the peripheral bulge produced by the laurentide ice sheet

loci and maximum size of thrust earthquakes and the mechanics of the shallow region of subduction zones earthquakes do not extend updip along the plate interface at most subduction zones all of the way to the plate boundary at the trench axis or deformation front rather the shallowest part of that interface moves mainly through stable aseismic slip that part of the plate boundary referred to here as the aseismic zone occurs along the base of an accreted wedge of young sediments the probable primary cause for the existence of this aseismic zone is the stable slip properties of the unconsolidated and semiconsolidated sediments in that zone subducted sediment is progressively dewatered and underplated to the base of the overriding plate through this process more consolidated rocks eventually come into contact at depth across both sides of the plate boundary from the point where sufficiently hard rock is found across the plate interface that interface will change its slip behavior to unstable stick slip sliding which is characteristic of consolidated material under most conditions this type of motion is accommodated seismically as episodic slip in large earthquakes the location of this transition to seismic behavior referred to as the seismic front marks the deep end of the aseismic zone and the top of the seismogenic zone i e that part of the plate interface that moves primarily in thrust earthquakes several convergent plate margins are discussed to illustrate the seismic front and the aseismic zone we find that the seismic front defined by smaller earthquakes that occur during the interval between large events is nearly the same as that for large events as inferred from the locations of their aftershocks the location of the seismic front is important for making estimates of the maximum possible size of thrust earthquakes along the plate boundary because it delimits the trenchward limit of the potential rupture area of these events the size of large thrust earthquakes is proportional to rupture area and to at least the cube of the downdip width w of that area thus by defining the location of the seismic front for convergent margins it is possible to make better estimates of w and hence to deduce the maximum size of future interplate earthquakes the average repeat time of such events is also related to w and so better estimates of average repeat time are possible from improved knowledge of w the hypothesis that the location of the seismic front is related to the maximum depth of subduction of unconsolidated sediment has implications for forearc mechanics we use a mechanical analysis laboratory modeling and multichannel seismic information to develop a simple model explaining the growth of forearcs the outer arc high or trench slope break that occurs arcward of most accretionary wedges represents an abrupt change in the critical taper of the accretionary wedge we argue that that change is caused by a large arcward increase in the strength of the material within the overriding plate that stronger material is called the backstop our laboratory modeling experiments indicate that a backstop with a trenchward dipping upper surface results in the development of an overlying structure that includes all of the primary morphologic features observed in modern forearcs in our modeling an accretionary wedge develops trenchward of the backstop an outer arc high develops above the trenchward toe of the backstop and farther arcward a passive forearc basin forms above the stronger material of the backstop this model is consistent with the observation that earthquakes do not extend updip along the plate interface all the way to the trench axis we hypothesize that plate motion is accommodated seismically along the base of the consolidated backstop and mostly or entirely aseismically trenchward of the toe of the backstop along the base of the accretionary wedge at several margins the seismic front is approximately coincident with the outer arc high supporting this interpretation

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

near field high resolution strain measurements prior to the october 18 1989 loma prieta ms 7 1 earthquake high resolution strain recordings were made in deep boreholes throughout california prior to during and following the october 18 1989 ms 7 1 loma prieta earthquake the nearest dilational strainmeters sensitivity 1010 and 3 component tensor strainmeters sensitivity 10 9 were 37 km to 42 km respectively from the main shock high quality data including details of strain offsets were recorded on both instruments through the earthquake these data have been searched for indications of short intermediate and long term strain redistribution and or fault slip that might have indicated imminent rupture short and intermediate term changes in both tensor strain and dilational strain several nanostrain if any during the minutes to months before the earthquake are at least 1000 times smaller than that generated by the earthquake itself if short term preseismic slip did occur at the nucleation point of the earthquake during the previous week and if the type of slip is similar to that during the earthquake its moment could not be more than 1024 dyne cm stated another way slip equivalent to that expected for a m 5 3 earthquake could have occurred in the hypocentral region without the strainmeters detecting it at these distances and azimuthal positions long term changes appear to have occurred in mid 1988 and mid 1989 these changes were both followed by ml 5 earthquakes in the hypocentral region on june 27 1988 and august 8 1989 respectively and since they correspond approximately to changes in geodetic strain rate over the epicenter may indicate precursory strain redistribution in the epicentral region minor postseismic strain recovery 14 occurred in the month following the main shock

continuous borehole strain in the san andreas fault zone before during and after the 28 june 1992 mw 7 3 landers california earthquake abstract high precision strain was observed with a borehole dilational strainmeter in the devil9s punchbowl during the 11 58 ut 28 june 1992 m w 7 3 landers earthquake and the large big bear aftershock m w 6 3 the strainmeter is installed at a depth of 176 m in the fault zone approximately midway between the surface traces of the san andreas and punchbowl faults and is about 100 km from the 85 km long landers rupture we have questioned whether unusual amplified strains indicating precursive slip or high fault compliance occurred on the faults ruptured by the landers earthquake or in the san andreas fault zone before and during the earthquake whether static offsets for both the landers and big bear earthquakes agree with expectation from geodetic and seismologic models of the ruptures and with observations from a nearby two color geodimeter network and whether postseismic behavior indicated continued slip on the landers rupture or local triggered slip on the san andreas we show that the strain observed during the earthquake at this instrument shows no apparent amplification effects there are no indications of precursive strain in these strain data due to either local slip on the san andreas or precursive slip on the eventual landers rupture the observations are generally consistent with models of the earthquake in which fault geometry and slip have the same form as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake finally there are some indications of minor postseismic behavior particularly during the month following the earthquake

validity of off the shelf handheld portable xrf for sourcing near eastern obsidian chip debris handheld portable xrf hhpxrf has received considerable recent attention in archaeology especially for obsidian sourcing published studies largely suggest a high potential for success hhpxrf though has been met with debate and scepticism concerns fall into three categories 1 low accuracy and precision 2 data correction schemes and calibration and 3 ignorance of fundamental xrf issues such as specimen size limits and morphology effects the result is that archaeological interpretations in hhpxrf based studies are cast into doubt should interpretations be believed if authors did not follow the perceived best practices to address such questions the validity of hhpxrf for near eastern obsidian sourcing was tested under deliberately sub optimal conditions irregular obsidian debitage near the minimum size limits was sourced with a success rate of 94 based on a rank matches to 100 based on a and b rank matches even under conditions chosen to mimic off the shelf operation

foreshock sequence of the 1992 landers california earthquake and its implications for earthquake nucleation the june 28 1992 landers california earthquake mw 7 3 was preceded for about 7 hours by a foreshock sequence consisting of at least 28 events in this study we examine the geometry and temporal development of the foreshocks using high precision locations based on cross correlation of waveforms recorded at nearby stations by aligning waveforms rather than trying to obtain travel time picks for each event independently we are able to improve the timing accuracy greatly and to make very accurate travel time picks even for emergent arrivals we perform a joint relocation using the improved travel times and reduce the relative location errors to less than 100 m horizontally and less than 200 m vertically with the improved locations the geometry of the foreshock sequence becomes clear the landers foreshocks occurred at a right step of about 500 m in the mainshock fault plane the nucleation zone as defined by the foreshock sequence is southeast trending to the south and nearly north trending to the north of the right step this geometry is confirmed by the focal mechanisms of the foreshock sequence which are right lateral and follow the trend as determined by the foreshock locations on the two straight segments of the fault and are rotated clockwise for foreshocks that occur within the step the extent of the foreshock sequence is approximately 1 km both vertically and horizontally modeling of the coulomb stress changes due to all previous foreshocks indicates that the foreshocks probably did not trigger each other this result is particularly clear for the mw 4 4 immediate foreshock since stress transfer in the sequence appears not to have played a significant role in its development we infer an underlying aseismic nucleation process probably aseismic creep other studies have shown that earthquake nucleation may be controlled by fault zone irregularities this appears to be true in the case of the landers earthquake although the size of the irregularity is so small that it is not detectable by standard location techniques

3 d modeling of pore pressure diffusion beneath koyna and warna reservoirs western india the mechanism of reservoir triggered seismicity is well understood and explains the earthquake occurrence at different reservoir sites it can be attributed to the stresses due to water loading and to changes in fluid pressure in pores within the rock matrix in the present study a 3 d fluid flow numerical model is used to investigate the pore pressure diffusion as a cause for continued seismicity in the koyna warna region in western india it is shown that reservoir water level fluctuations are sufficient to trigger earthquakes at the seismogenic depths in the region our numerical model suggests that a vertical fault with hydraulic conductivity in the range 2 6 m day facilitates the diffusion of pressure at focal depths of earthquakes in the koyna warna region also for triggering of earthquakes a higher vertical conductivity is required for the warna region than for the koyna region a lag of two months period is found between the maximum water level and the significant hydraulic head required to trigger earthquakes at the focal depth using the appropriate hydraulic conductivity for both the reservoirs

asthenospheric viscosity and stress diffusion a mechanism to explain correlated earthquakes and surface deformations in ne japan summary a significant correlation is found in both space and time between the intraplate land and interplate sea thrust zone only earthquakes in tohoku ne japan that has persisted since the times of reliably reported events in ad 1600 the correlation peaks at a land lead of about 36 yr with an average correlation distance of 200km with the implication of an average strain migration rate of 5 6 km yr 1 the correlation is highly significant 99 per cent both from formal statistics and from tests of random shuffles of the data additional analysis of the data as a point process confirms the results of the correlation analysis the sharpness of the correlation peak when compared to the individual times of occurrence of the land and sea events suggests a trigger mechanism to explain the correlation the general model ofsubduction rupture rebound is extended to include additional features the buckling of the land plate from the force of the subducting slab and the viscoelastic coupling of the plate to the underlying asthenosphere a buckle produces a high stress region in the continental plate where earthquakes are more prone to occur thus producing the spatial correlation in the data this may also explain the preferred location on land for the smaller modern day seismic events in ne japan the viscoelastic coupling controls the interaction between the land and sea events resulting in the temporal correlation in the data because of viscosity the model equations are diffuse like with strain pulses as solutions thus from the inferred strain migration rate it is possible to estimate asthenospheric viscosity 7 1018pa s using this model a large land shock generates a strain pulse that affects the locked fault at the thrust zone several decades later as the continental plate tends to pull away from the subducting slab the frictional force arising from the overburden pressure is reduced thus unlocking the fault and triggering a sea earthquake the viscoelastic model is also used to explain surface deformations measured by triangulation surveys in japan in 1904 and 1964 horizontal displacements which we believe are surface manifestations of the strain pulse from the large 1896 riku u land shock m 7 5 in ne japan are fit well by the model and provide a viscosity estimate 13 1018 pa s

forecast model for great earthquakes at the nankai trough subduction zone an earthquake instability model is formulated for recurring great earthquakes at the nankai trough subduction zone in southwest japan the model is quasistatic two dimensional and has a displacement and velocity dependent constitutive law applied at the fault plane a constant rate of fault slip at depth represents forcing due to relative motion of the philippine sea and eurasian plates the model simulates fault slip and stress for all parts of repeated earthquake cycles including post inter pre and coseismic stages calculated ground uplift is in agreement with most of the main features of elevation changes observed before and after the m 8 1 1946 nankaido earthquake in model simulations accelerating fault slip has two time scales the first time scale is several years long and is interpreted as an intermediate term precursor the second time scale is a few days long and is interpreted as a short term precursor accelerating fault slip on both time scales causes anomalous elevation changes of the ground surface over the fault plane of 100 mm or less within 50 km of the fault trace

pxrf calibrations for volcanic rocks and the application of in field analysis to the geosciences advances in portable x ray fluorescence pxrf technologies have made such instruments an attractive choice for geologists who wish to collect chemical data in the field the acceptance of pxrf data for research purposes such as for example petrogenetic studies by the geologic community has been hampered by a perception of poor quality here we show that current generation pxrf instruments can yield high quality data when deployed either in the laboratory or as a base camp field instrument we have developed four calibrations for major minor and trace elements in geological materials using minimal sample preparation one for the broad range of geologic compositions 0 100 sio2 using rock powders and three with an emphasis on volcanic rock samples rock billets ranging from primitive basalt to rhyolite basalt rock powder and rhyolitic pumice powder the calibrations use influence coefficients to correct for absorbance and secondary enhancement of one element by x rays of other elements present in the sample nugget effects can have a significant influence over the determination of the concentration of elements such as zr if proper care in sample homogenization is not taken we evaluate data quality for each element in each calibration and find that for several elements ti mn fe ca k p cr ni zn rb sr y zr nb precision and accuracy approach those obtainable from full size wavelength dispersive xrf analysis maximization of data quality is achieved by matching of calibration material types and unknowns

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

machine learning classifiers for attributing tephra to source volcanoes an evaluation of methods for alaska tephras glass composition based correlations of volcanic ash tephra traditionally rely on extensive manual plotting many previous statistical methods for testing correlations are limited by using geochemical means masking diagnostic variability we suggest that machine learning classifiers can expedite correlation quickly narrowing the list of likely candidates using well trained models eruptives from alaska s aleutian arc alaska peninsula and wrangell volcanic field were used as a test environment for 11 supervised classification algorithms trained on nearly 2000 electron probe microanalysis measurements of glass major oxides representing 10 volcanic sources artificial neural networks and random forests were consistently among the top performing learners accuracy and kappa 0 96 their combination as an average ensemble effectively improves their performance using this combined model on tephras from eklutna lake south central alaska showed that predictions match traditional methods and can speed correlation although classifiers are useful tools they should aid expert analysis not replace it the eklutna lake tephras are mostly from redoubt volcano besides tephras from known holocene active sources holocene tephra geochemically consistent with pleistocene emmons lake volcanic center dawson tephra but from a yet unknown source is evident these tephras are mostly anchored by a highly resolved varved chronology and represent new important regional stratigraphic markers

interplate coupling in northeast japan deduced from inversion analysis of gps data abstract the spatial distribution of the strength of interplate coupling between the subducting pacific plate and the overlying continental plate in northeast japan was investigated through an inversion analysis of gps data employing akaike s bayesian information criterion the gps data used for the inversion analysis are rates of baseline length changes and vertical displacement rates of crustal movements during the period from april 6 1996 to march 20 1998 which were obtained at 161 continuous gps observation stations operated by the geographical survey institute of japan the result shows the average drag rates of the overriding plate on the model source regions off the tohoku and hokkaido districts are 6 7 cm yr and 6 8 cm yr respectively which are 0 85 and 0 87 as interplate coupling ratio these values are much higher than those in previous studies the average directions of drag rates are oriented n73 w 15 and n78 w 13 on the model source regions off the tohoku and hokkaido districts respectively these directions agree well with the direction of coseismic slip of the foot wall side n75 w of the 1978 miyagiken oki earthquake m 7 4 but differ slightly from the direction estimated from the plate motion model n65 w seno et al j geophys res 101 1996 11305 11315 we also found afterslip of 5 5 cm yr associated with the 1994 sanriku haruka oki earthquake m 7 5 off aomori prefecture interestingly enough large afterslip occurred on the plate boundary even when more than a year had passed after the sanriku haruka oki earthquake the amount of drag rate becomes dramatically small at depths greater than about 50 km on the model source regions indicating weak interplate coupling there

interseismic deformation at the nankai trough japan subduction zone uplift along the coast of southwestern japan following the 1944 tonankai ms 8 0 and 1946 nankaido ms 8 2 earthquakes has been inferred from the 1950 1985 tide gage records although uplift rates vary with geographic position the temporal dependence at each site can be described as the superposition of an exponentially decaying time constant 5 years transient significant only in the first decade postseismic and a steady interseismic rate the steady interseismic uplift rate is defined only over the 1956 1985 interval but the linearity in time ofthat uplift record is such that uplift over the remainder of the interseismic cycle 80 years might reasonably be expected to occur at the same rate moreover the spatial pattern and magnitude of the steady uplift rate are reasonably close to those predicted by a simple dislocation model of subduction however the currently observed steady uplift rate is not consistent with the uplift rate inferred from geodetic leveling for the final half of the previous earthquake cycle thus either the hypothesis of a steady interseismic uplift rate after the first decade postseismic is wrong or the strain accumulation pattern for one earthquake need not be the same as for the preceding earthquake on the same segment