hydrochemical appraisal of groundwater and its suitability in the intensive agricultural area of muzaffarnagar district uttar pradesh india muzaffarnagar is an economically rich district situated in the most fertile plains of two great rivers ganga and yamuna in the indo gangetic plains with agricultural land irrigated by both surface water as well as groundwater an investigation has been carried out to understand the hydrochemistry of the groundwater and its suitability for irrigation uses groundwater in the study area is neutral to moderately alkaline in nature chemistry of groundwater suggests that alkaline earths ca mg significantly exceed the alkalis na k and weak acids exceed the strong acids cl so4 suggesting the dominance of carbonate weathering followed by silicate weathering majority of the groundwater samples 62 posses ca mg hco3 type of hydrochemical species followed by ca na mg hco3 na ca mg hco3 ca mg na hco3 cl and na ca hco3 so4 types a positive high correlation r2 0 928 between na and cl suggests that the salinity of groundwater is due to intermixing of two or more groundwater bodies with different hydrochemical compositions barring a few locations most of the groundwater samples are suitable for irrigation uses chemical fertilizers sugar factories and anthropogenic activities are contributing to the sulphate and chloride concentrations in the groundwater of the study area overexploitation of aquifers induced multi componential mixing of groundwater with agricultural return flow waters is responsible for generating groundwater of various compositions in its lateral extent

moment tensor solutions for small and moderate earthquakes in the ibero maghreb region 1 we applied time domain moment tensor inversion of local and regional waveforms to small and moderate mw 3 5 5 7 shallow earthquakes from the iberian peninsula northern morocco and northern algeria for the 6 years period from november 1995 to march 2002 and the previous network of autonomously recording seismograms nars experiment moment tensor solutions were obtained for 58 events considerably increasing the total number of available solutions in the study area for each event we performed a moment tensor inversion and a double couple grid search for simple faulting events the grid search is valuable as a quality test for its ability to reveal potential ambiguities of the solutions and to assess confidence limits of fault plane parameters or principal axes orientation the computed mechanisms show regional consistency a large part of the iberian peninsula is characterized by normal faulting mechanisms with sw ne oriented t axes thrusting and se nw compression is dominant in algeria in the alboran sea the westernmost part of the mediterranean and the transition between both regimes strike slip mechanisms dominate with approximately n s oriented p axes this pattern suggests a regional anomaly characterized by clockwise rotation of the principal horizontal stress orientations

3 d rotation of double couple earthquake sources summary we discuss 3 d rotations by which one double couple earthquake source can be rotated into another arbitrary double couple due to the symmetry of double couple sources there are four such rotations an algorithm is obtained in analytical form which is also available as a computer program solving the inverse problem of 3 d rotation of double couple earthquake sources i e for each pair of focal mechanisms or seismic moment tensor solutions the program finds all four rotations which rotate one mechanism into another this algorithm may be used in a wide variety of studies of stress field causing earthquakes investigations of the relationship between the focal mechanisms and the tectonic features of a seismogenic region etc the same inversion algorithm can be used to study the 3 d rotation of any symmetric second rank tensor such as the stress or strain tensor

effects of three dimensional earth structure on cmt earthquake parameters abstract we investigate errors in centroid earthquake parameters due to unmodeled structural heterogeneity we generate a simulated dataset consisting of synthetic seismograms for 50 earthquakes and 150 stations distributed globally to generate the synthetic seismograms we use a spectral element wave propagation package specfem3d globe that accounts for the earth s three dimensional structure an established centroid moment tensor inversion algorithm from the global cmt project is used to invert the synthetic dataset with and without added noise for earthquake source parameters this algorithm uses a one dimensional earth structure together with approximate corrections for three dimensional structure to model the seismograms we interpret the differences between the estimated source parameters and the parameters used to compute the synthetic dataset as errors due to unmodeled structural heterogeneity and the presence of noise we expect that the errors obtained in this study are representative of the errors in the global cmt catalogue we find that the errors in scalar moment moment tensor elements and location are small on average the depth and centroid time are however biased by a small amount we find that the error in depth can be reduced significantly by applying corrections for the difference in the velocity structure at the source and receiver locations from the earth s average structure in the cmt inversions this modification has a minimal effect on the errors in centroid time we do not find large errors in scalar moments even where the crustal thickness at the source is very different from the earth s average crustal thickness

improving local earthquake locations using the l1 norm and waveform cross correlation application to the whittier narrows california aftershock sequence experiments with different earthquake location methods applied to aftershocks of the october 1 1987 whittier narrows earthquake in california ml 5 9 suggest that local event locations can be greatly improved through the use of the l1 norm station corrections and waveform cross correlation the whittier narrows sequence is a compact cluster of over 500 events at 12 to 18 km depth located within the dense station coverage of the southern california seismic network scsn a telemetered network of several hundred short period seismographs scsn travel time picks and waveforms obtained through the southern california earthquake center are examined for 589 earthquakes between 1981 and 1994 in the vicinity of the mainshock using a smoothed version of the standard southern california velocity model and the existing travel time picks improved location accuracy is obtained through use of the l1 norm rather than the conventional least squares l2 norm approach presumably due to the more robust response of the former to outliers in the data a large additional improvement results from the use of station terms to account for three dimensional velocity structure outside of the event cluster to achieve greater location accuracy waveforms for these events are resampled and low pass filtered and the p and s wave cross correlation functions are computed at each station for every event pair for those events with similar waveforms differential times may be obtained from the cross correlation functions these times are then combined with the travel time picks to invert for an adjusted set of picks that are more consistent than the original picks and include seismograms that were originally unpicked locations obtained from the adjusted picks show a further improvement in accuracy location uncertainties are estimated using a bootstrap technique in which events are relocated many times for sets of picks in which the travel time residuals at the best fitting location are used to randomly perturb each pick improvements in location accuracy are indicated by the reduced scatter in the residuals smaller estimated location errors and the increased tendency of the locations to cluster along well defined fault planes median standard errors for the final inversion are 150 m in horizontal location and 230 m in vertical location although the relative locations within localized clusters of similar events are better constrained seismicity cross sections resolve the shallow dipping fault plane associated with the mainshock and a steeply dipping fault plane associated with a ml 5 3 aftershock these fault planes appear to cross and activity began on the secondary fault plane prior to the large aftershock

amplitude spectra moment tensor inversion of shallow earthquakes in spain summary the study of focal mechanisms for shallow earthquakes of low to moderate magnitude at regional distances requires a proper inversion technique one of the major problems is the correct separation of path effects from source effects the method used should take into account problems arising from errors in the definition of crustal structure and inclusion of the high frequency content of the waveforms in this study a method of frequency domain moment tensor inversion to determine deviatoric moment tensor solutions from body wave amplitude spectra is described the method has been tested with synthetic data to define instabilities that are due to mismodelling of several parameters the inversion technique is applied to broadband seismic data of shallow 10 km depth earthquakes in spain solutions are obtained for a range of depths and compared with solutions obtained with different methods such as first motion polarities and moment tensor inversion in the time domain a combined fit of amplitude spectra first motion polarities and double couple component is introduced as a method which resolves better the non uniqueness of solution the proposed method can be implemented in fast moment tensor inversion when a green functions database has been created in advance for the studied area

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

diatomaceous origin of siliceous shale in eocene lake beds of central british columbia the abundance of diatoms in neogene lacustrine sediments and their apparent scarcity in paleogene deposits have long perplexed geoscientists but siliceous shales from eocene lake beds of central british columbia provide new insights major element geochemistry x ray diffraction patterns and relict diatom frustules suggest that eocene beds at horsefly mcabee and princeton originated as lacustrine diatomite that underwent diagenetic alteration to produce siliceous shale the combination of high sio2 and low al2o3 values and the presence of opal ct x ray diffraction peaks provide a distinctive geochemical fingerprint for biogenic silica deposits that have been remineralized the discovery of diatomaceous geochemical signatures in siliceous shales may prove to be a useful tool for extending the geologic record of diatoms perhaps helping to reduce the apparent discrepancy between fossil evidence and evolutionary interpretations based extant species

triggering of earthquake aftershocks by dynamic stresses it is thought that small static stress changes due to permanent fault displacement can alter the likelihood of or trigger earthquakes on nearby faults many studies of triggering in the near field particularly of aftershocks rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault here we report a comparison of the aftershock pattern of the moment magnitude mw 7 3 landers earthquake not only with static stress changes but also with transient oscillatory stress changes transmitted as seismic waves that is dynamic stresses dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone these dynamically weakened faults may fail after the seismic waves have passed by and might even cause earthquakes that would not otherwise have occurred we find similar asymmetries in the aftershock and dynamic stress patterns the latter being due to rupture propagation whereas the static stress changes lack this asymmetry previous studies have shown that dynamic stresses can promote failure at remote distances but here we show that they can also do so nearby

regional moment tensor determination in the european mediterranean area initial results the broadband seismic network in the european mediterranean area provides high quality data we invert these regional three component data for the source parameters of moderate to strong earthquakes in the entire european mediterranean area regional seismograms have a good signal to noise ratio even for moderate sized events that are too small for teleseismic analysis the magnitude threshold for source parameter determination can thus be significantly lowered the threshold depends on the average event station distances within dense broadband networks we analyze mw 3 0 earthquakes in areas far from broadband seismic stations the lower bound is mw 4 5 4 8 still considerably lower than the teleseismic analysis threshold about mw 5 0 5 3 for larger events we perform rapid moment tensor analysis using near real time data solutions are posted within hours after event occurrence in a second step we merge near real time and later available data to obtain a regional moment tensor catalog of moderate to large earthquakes for the entire european mediterranean area within less than 1 year we have analyzed 67 earthquakes ranging in size from mw 2 9 to 7 5 the solutions cover the seismically active areas of the european mediterranean area particularly important are solutions for slowly deforming regions where large earthquakes that could be analyzed with teleseismic data occur infrequently the solutions are reliable for events with independent source parameter estimates the agreement is generally high the solutions are robust variations in epicentral parameters source depth or exact choice of stations do not affect source parameter estimates strongly the moment magnitudes provide a unified estimate of earthquake size for the european mediterranean area we perform regression analyses to link our moment magnitudes with local body and surface wave magnitudes

patterns of co seismic strain computed from southern california focal mechanisms summary geometrical properties of an earthquake population can be described by summation of seismic potency tensors that provide a strain based description of earthquake focal mechanisms we apply this method to 170 000 potency tensors for 0 ml 5 southern california earthquakes recorded between january 1984 and june 2003 we compare summed tensors for populations defined by faulting region and earthquake magnitude to investigate the relation between earthquake characteristics tectonic domains and fault related length scales we investigate spatial scales ranging from 1 700 km and use the results to identify systematic differences between seismic behaviour for different faults and different regions our results show features that are indicative of both scale invariant and scale dependent processes on the largest scale the overall potency tensor summation for southern california 0 ml 5 earthquakes over 20 yr corresponds closely to a double couple dc mechanism with slip direction parallel to relative plate motion the summed tensors and derived quantities for the different regions show clear persistent variations that are related to the dominant tectonic regime of each region significant differences between the non dc components of the summed tensors which we relate to fault heterogeneity indicate systematic differences in deformation associated with earthquake populations from different fault zones or different magnitude ranges we find an increase of heterogeneity for populations of smaller earthquakes and for regions where faulting deviates strongly from the overall sense of deformation even when corrected for quality the results imply an overall organization of earthquake characteristics into domains that are controlled to first order by geometrical properties of the largest faults and the plate motion smaller scale characteristics are related to local variations in the orientation complexity and size of faults

geochemistry of groundwater in parts of guntur district andhra pradesh india hydrogeochemical investigations which are significant for the assessment of water quality have been carried out to study the sources of dissolved ions in groundwaters of some rural areas of guntur district andhra pradesh india groundwaters in the area are mostly brackish high contents of sio2 and na and cl ions in groundwater in comparison with those of seawater suggests a meteoric origin of groundwater the high concentration of sio2 and various geochemical signatures reflect the weathering of minerals however the na k vs cl ratio suggests weathering has occurred only to some extent the chemistry of groundwater favours the formation of clay minerals montmorillonite illite and chlorite because of evapotranspiration the positive saturation index of caco3 and the high signatures of ma2 ca2 and na ca2 reveals the occurrence of evaporation the evaporation enhances the concentration of ions which occurred originally in the water in the soils during summer the very high so 4 2 and cl contents in some groundwaters and the occurrence of kankar caco3 in the area suggest a long history of evaporation greater ionic concentration in the groundwaters of post monsoon compared with pre monsoon indicates the increasing addition of leachates into the groundwater from the soils in the monsoon and anthropogenic activities which leads to a deteriorating quality of groundwater according to the gibbs diagrams rock weathering to some extent and evaporation are the dominant phenomena responsible for the higher ionic concentrations found in groundwater measures that benefit sustainable management of groundwater quality are suggested in this study

evaluation of hydrogeochemical processes in arsenic contaminated alluvial aquifers in parts of mid ganga basin bihar eastern india the study region covers 1 650 km2 of the mid ganga basin in bihar experiencing intensive groundwater draft the area forms a part of the gangetic alluvial plain where high incidence of arsenic groundwater contamination 50 g l has recently been detected seventy seven groundwater samples have been collected and analysed for major ions iron and arsenic arsenic contamination max 620 g l is confined in hand pump zones 15 35 m within the newer alluvium deposited during middle holocene to recent age the older alluvial aquifers are arsenic safe and recorded maximum concentration as 9 g l out of 12 hydrochemical facies identified four have been found arsenic affected ca hco3 mg hco3 ca mg hco3 and mg ca hco3 the geochemical evolution of groundwater as investigated by graphical interpretation and statistical techniques correlation principal component analysis revealed that dissolution of detrital calcite dolomite and infiltration of rainwater are the major processes shaping the groundwater chemistry in the newer alluvium arsenic and iron showed strong positive correlation rainfall infiltration carrying organic matter from recently accumulated biomass from this flood prone belt plays a critical role in releasing arsenic and iron present in the sediments geochemical evolution of groundwater in older alluvium follows a different path where cation exchange has been identified as a significant process

source parameter inversion for recent great earthquakes from a decade long observation of global gravity fields we quantify gravity changes after great earthquakes present within the 10 year long time series of monthly gravity recovery and climate experiment grace gravity fields using spherical harmonic normal mode formulation the respective source parameters of moment tensor and double couple were estimated for the 2004 sumatra andaman earthquake the gravity data indicate a composite moment of 1 2 1023 n m with a dip of 10 in agreement with the estimate obtained at ultralong seismic periods for the 2010 maule earthquake the grace solutions range from 2 0 to 2 7 1022 n m for dips of 12 24 and centroid depths within the lower crust for the 2011 tohoku oki earthquake the estimated scalar moments range from 4 1 to 6 1 1022 n m with dips of 9 19 and centroid depths within the lower crust for the 2012 indian ocean strike slip earthquakes the gravity data delineate a composite moment of 1 9 1022 n m regardless of the centroid depth comparing favorably with the total moment of the main ruptures and aftershocks the smallest event we successfully analyzed with grace was the 2007 bengkulu earthquake with m0 5 0 1021 n m we found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events deeper sources i e in the upper mantle could not reproduce the gravity observation as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume thus reducing the negative gravity component focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum

constraints on the long period moment dip tradeoff for the tohoku earthquake since the work of kanamori and given 1981 it has been recognized that shallow pure dip slip earthquakes excite long period surface waves such that it is difficult to independently constrain the moment m 0 and the dip of the source mechanism with only the product m 0 sin 2 being well constrained because of this it is often assumed that the primary discrepancies between the moments of shallow thrust earthquakes are due to this moment dip tradeoff in this work we quantify how severe this moment dip tradeoff is depending on the depth of the earthquake the station distribution the closeness of the mechanism to pure dip slip and the quality of the data we find that both long period rayleigh and love wave modes have moment dip resolving power even for shallow events especially when stations are close to certain azimuths with respect to mechanism strike and when source depth is well determined we apply these results to usgs w phase inversions of the recent m9 0 tohoku japan earthquake and estimate the likely uncertainties in dip and moment associated with the moment dip tradeoff after discussing some of the important sources of moment and dip error we suggest two methods for potentially improving this uncertainty

the december 7 2012 japan trench intraplate doublet mw 7 2 7 1 and interactions between near trench intraplate thrust and normal faulting a pair of large earthquakes ruptured within the pacific plate below the japan trench about 14 s apart on december 7 2012 the doublet began with an m w 7 2 thrust event 50 70 km deep followed by an m w 7 1 7 2 normal faulting event in the range 10 30 km deep about 27 km to the south southwest the deep lithosphere thrust earthquake is the largest such event to be recorded seaward of the rupture zone of the great march 11 2011 tohoku m w 9 0 earthquake it follows an extensive intraplate normal faulting aftershock sequence since 2011 extending up to 100 km east of the trench many small normal faulting aftershocks of the doublet occurred along a 60 km long trench parallel trend beneath the inner trench slope the complex overlapping signals produced by the doublet present challenges for routine long period moment tensor inversion procedures but the inadequacy of any single point source inversion was readily evident from comparisons of different data sets and solutions using different frequency bands we use a two double couple inversion of w phase signals to quantify the doublet characteristics along with an iterative deconvolution of p wave signals that extracts a compatible three sub event sequence the occurrence of a large deep compressional event near the trench several years subsequent to a great megathrust event is similar to a sequence that occurred in the central kuril islands between 2006 and 2009 and appears to be associated with stress changes caused by the preceding interplate thrusting and intraplate normal faulting recent large deep compressional events in the philippine trench and northern kermadec trench regions may be influenced by strain accumulation on adjacent locked interplate megathrusts regions having more pronounced curvature of the subducting plate may have unrelaxed bending stresses facilitating occurrence of large deep thrust faulting in advance of future megathrust failures as was observed in 1963 in the central kuril islands region but not in the gently curving pacific plate offshore of the great tohoku event

polarities of p and s waves and shear wave splitting observed from the bucaramanga nest colombia the bucaramanga nest colombia is an intense seismic source centered at 6 48 n 73 10 w and 161 km depth beneath the eastern andes during a 3 week period 161 microearthquakes mb 4 3 were recorded by a 260 by 140 km array of 12 three component university of wisconsin uw seismographs centered above the nest eighty eight percent of the events recorded were from the nest providing a unique opportunity to study natural events that have different source parameters but nearly the same ray paths shear wave splitting analysis shows that the average polarization direction of the first arriving shear waves from the nest events at nine of the seismographs is n12 e 18 after corrections based on the amount of discrepancy between the observed average p wave azimuth and the expected event to station azimuth average s wave polarization is n6 e 15 variation in time delays with azimuth and epicentral distance appears to be due to the varying angles between the ray path and the principal axes of the anisotropic system shear wave splitting observed from 17 events along the wadati benioff zone outside the nest shows that the time delays increase with increasing depth and defines a wedge shaped anisotropic volume above the subducting plate the anisotropic layer has a maximum thickness of approximately 60 km at the depth of the nest and is thinning updip the anisotropy most likely results from aligned anisotropic minerals such as olivine and orthopyroxene in a localized mantle flow in the lithosphere above the wadati benioff zone a region weakened by active fluid migration and mobilized by the heating and shearing along the suducting slab

application of gis and hydrogeochemistry of groundwater pollution status of nagapattinam district of tamil nadu india this study evaluated groundwater quality of the coastal aquifer in nagapattinam district with intensive agricultural activities in the southern part of india chemical components such as ph ec tds major cations and anions were used to identify seawater intrusion fifty two groundwater samples were collected from dug and bore wells in this region during summer and monsoon seasons 2011 ec tds na and cl were higher in summer than in monsoon the correlation and two way joining cluster analyses clearly show that groundwater quality is mainly controlled by seawater intrusion and other anthropogenic sources modified hill piper exhibits that most of the samples belong to water contaminated with gypsum sector the interpretation of gibbs plot represents the groundwater samples that fall in evaporation and rock weathering zone and other samples are affiliated to various anthropogenic activities based on na sar chloride hardness and wilcox classification the groundwater is moderately suitable for agriculture this region is vulnerable to seawater intrusion during summer due to the severe pumping of groundwater in groundwater quality maps produced by inverse distance weighting of arcgis some good and medium patches could be used for agriculture to a certain extent the northern southern and central parts of the study area fell in poor quality regions because of seawater intrusion and infiltration of irrigation water contaminated with pesticides and fertilizers

source process of the 3 november 2002 denali fault earthquake central alaska from teleseismic observations 1 the november 3 2002 denali fault earthquake which is the largest inland event ever recorded in central alaska occurred along an arcuate segment of the right lateral strike slip denali fault we use first motion p wave polarities and inversions of teleseismic p waveforms for a fixed focal mechanism to constrain the rupture process we find clear evidence for a substantial reverse component near the hypocenter at the beginning of the rupture twenty five seconds later rupture propagated unilaterally to the east on a strike slip fault and released most of the seismic moment along an asperity located 170 km east of the hypocenter with a maximum slip of 8 m this earthquake had a duration of 120 s and ruptured more than 300 km in length correlation with gravity anomalies suggests a relation between moment distribution and physical properties of subsurface rock units that may support a weaker middle fault segment marked by fewer aftershocks

contribution of satellite gravimetry to understanding seismic source processes of the 2011 tohoku oki earthquake 1 the 2011 great tohoku oki earthquake apart from shaking the ground perturbed the motions of satellites orbiting some hundreds km away above the ground such as grace due to coseismic change in the gravity field significant changes in inter satellite distance were observed after the earthquake these unconventional satellite measurements were inverted to examine the earthquake source processes from a radically different perspective that complements the analyses of seismic and geodetic ground recordings we found the average slip located up dip of the hypocenter but within the lower crust as characterized by a limited range of bulk and shear moduli the grace data constrained a group of earthquake source parameters that yield increasing dip 7 16 2 and simultaneously decreasing moment magnitude 9 17 9 02 0 04 with increasing source depth 15 24 km the grace solution includes the cumulative moment released over a month and demonstrates a unique view of the long wavelength gravimetric response to all mass redistribution processes associated with the dynamic rupture and short term postseismic mechanisms to improve our understanding of the physics of megathrusts

a deep outer rise reverse fault earthquake immediately triggered a shallow normal fault earthquake the 7 december 2012 off sanriku earthquake mw 7 3 1 teleseismic body wave analysis revealed that the 7 december 2012 off sanriku earthquake mw 7 3 at the outer rise of japan trench consisted of two successive subevents the first subevent with reverse fault mechanism event 1 mw 7 1 at 56 km depth was followed by approximately 20 s later the second subevent with normal fault mechanism event 2 mw 7 2 at 6 km depth finite fault slip models show that the slip of event 1 was concentrated around the initial rupture point with the maximum of 2 7 m and that event 2 had two asperities with the maximum of 4 5 m at both sides of the initial rupture point the static coulomb failure function analyses suggested that event 1 triggered event 2 and that both subevents were promoted by the 2011 tohoku earthquake mw 9 1

source models of great earthquakes from ultra low frequency normal mode data abstract we present a new earthquake source inversion technique based on normal mode data for the simultaneous determination of the rupture duration length and moment tensor of large earthquakes with unilateral rupture we use ultra low frequency f m w 8 5 i sumatra andaman 26th december 2004 ii nias sumatra 28th march 2005 iii bengkulu 12th september 2007 iv tohoku japan 11th march 2011 v maule chile 27th february 2010 and vi the 24 may 2013 m w 8 3 okhotsk sea russia deep 607 km event while finite source inversions for rupture length duration magnitude and fault mechanism are possible for the sumatra andaman and tohoku events for all the other events their lower magnitudes only allow stable point source inversions of mode multiplets we obtain the first normal mode finite source model for the 2011 tohoku earthquake which yields a fault length of 461 km a rupture duration of 151 s and hence an average rupture velocity of 3 05 km s giving an independent confirmation of the compact nature of this event for all the other earthquakes studied our new source models agree well with previous studies we do not find any unexplained systematic differences between our results and those in the literature suggesting that for the wave frequencies considered the moment magnitude and the fault mechanism of the earthquakes studied do not show a strong frequency dependence

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

a probability method for local earthquake focal mechanisms we propose a method for obtaining focal mechanisms of earthquakes recorded on a local network it is based on the non linear estimation of the probability function for strike dip and slip of the focal mechanism from p polarities s polarizations and s p amplitude ratios the method is shown to be effective for the analysis of small earthquakes recorded by local networks in particular the s p amplitude ratios bring strong constraints on fault parameters even if large errors are present an application to a small earthquake recorded at the volcanic zone of campi flegrei naples italy during a seismic outburst is presented

microseismicity and focal mechanisms of the intermediate depth bucaramanga nest colombia the bucaramanga nest of intermediate depth seismicity in northern colombia was investigated from microearthquakes m sub b less than or equal to4 3 recorded from june 20 to july 6 1979 by a local array of 12 digital three component seismographs of 161 events studied 142 are from the nest and 19 define a thin wadati benioff w b zone mainly from 110 to 190 km depth the w b zone part of the bucaramanga segment strikes n10 sup 0 e with a dip increasing wtih depth from 30 sup 0 e to near vertical beneath the nest the 89 best located events from within the nest define a volume of about 8 km nw by 4 km ne by 4 km depth centered at 161 km depth with relative location accuracies of 0 5 to 1 0 km double couple fault plane solutions of 59 events were determined from an objective procedure using p wave polarities and s p amplitude ratios there is no dominant trend in focal mechanisms nor any reasonable correlation with regional stress patterns or previously determined mechanisms from teleseismic data the subduction and assimilation of a linear feature such as an island arc undergoing a phase transformation may explain the existence of the bucaramanga nest however the extraordinarilymore high rate of seismicity suggests that the nest may be moving rate several orders of magnitude faster than the rate of relative plate motion alone the intense seismicity and variation in focal mechanisms suggest that the nest represents some aspect of stress release associated with the ascent of fluids perhaps brine or magma that will ultimately result in the initiation of volcanic activity over this recently emplaced w b zone copyright american geophysical union 1987 less

automatic regional moment tensor inversion in the european mediterranean region summary we produce fast and automatic moment tensor solutions for all moderate to strong earthquakes in the european mediterranean region the procedure automatically screens near real time earthquake alerts provided by a large number of agencies each event with magnitude m 4 7 triggers an automatic request for near real time data at several national and international data centres moment tensor inversion is performed using complete regional long period 50 100 s waveforms initially the data are inverted for a fixed depth to remove traces with a low signal tonoise ratio the remaining data are then inverted for several trial depths to find the best fitting depth solutions are produced within 90 min of an earthquake we analyse the results for the period 2000 april to 2002 april to evaluate the performance of the procedure for quality assessment we compared the results with the independent swiss regional moment tensor catalogue srmt and divided the 87 moment tensor solutions into three groups 38 a quality solutions with well resolved m w depth and focal mechanism 21 b quality solutions with wellresolved m w and 28 unreliable c quality solutions the non homogeneous station and event distributions varying noise level and inaccurate earthquake locations affected solution quality for larger events m w 5 5 we consistently obtained a quality solutions for m w 4 5 5 5 we obtained a and b quality solutions solutions that pass empirical rules mimicking the a posteriori quality for our data set are automatically disseminated

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

groundwater hydrochemistry of a sugarcane cultivation belt in parts of muzaffarnagar district uttar pradesh india the kali hindon is a watershed in the most productive central ganga plain of india the whole area is a fertile track with sugarcane being the principal crop systematic sampling was carried out to assess the source of dissolved ions impact of sugar factories and the quality of groundwater thirty six samples were collected covering an area of 395 km2 the quality of groundwater is suitable for irrigational purposes but is rich in so4 which is not best for human consumption graphical treatment of major ion chemistry helps identify six chemical types of groundwater all possible species such as na cl k cl na hco3 na so4 ca hco3 mg hco3 ca so4 and mg so4 are likely to occur in the groundwater system the most conspicuous change in chemistry of groundwater is relative enrichment of so4 the interpretation of data reveals that so4 has not been acquired through water rock interaction the source of so4 is anthropogenic sugar factories alone are responsible for this potential environmental hazard

computing a large refined catalog of focal mechanisms for southern california 1981 2010 temporal stability of the style of faulting using the method developed by hardebeck and shearer 2002 2003 termed the hash method we calculate focal mechanisms for earthquakes that occurred in the southern california region from 1981 to 2010 when available we use hypocenters refined with differential travel times from waveform cross correlation using both the p wave first motion polarities and the s p amplitude ratios computed from three component seismograms we determine mechanisms for more than 480 000 earthquakes and analyze the statistical features of the whole catalog we filter the preliminary catalog with criteria associated with mean nodal plane uncertainty and azimuthal gap and obtain a high quality catalog with approximately 179 000 focal mechanisms as more s p amplitude ratios become available after 2000 the average nodal plane uncertainty decreases significantly compared with mechanisms that include only p wave polarities in general the parameters of the focal mechanisms have been stable during the three decades the dominant style of faulting is high angle strike slip faulting with the most likely p axis centered at n5 e for earthquakes of m 2 5 events using the 210 moment tensor solutions in tape et al 2010 as benchmarks we compare the focal plane rotation angles of common events in the catalog seventy percent of common earthquakes match well with rotation angles less than the typical nodal plane uncertainty the common events with relatively large rotation angles are either located around the edge of the scsn network or poorly recorded

seismicity of the atlantis massif detachment fault 30 n at the mid atlantic ridge 1 at the oceanic core complex that forms the atlantis massif at 30 n on the mid atlantic ridge slip along the detachment fault for the last 1 5 2 ma has brought lower crust and mantle rocks to the seafloor hydroacoustic data collected between 1999 and 2003 suggest that seismicity occurred near the top of the massif mostly on the southeastern section while detected seismicity along the adjacent ridge axis was sparse in 2005 five short period ocean bottom seismographs obs were deployed on and around the massif as a pilot experiment to help constrain the distribution of seismicity in this region analysis of six months of obs data indicates that in contrast to the results of the earlier hydroacoustic study the vast majority of the seismicity is located within the axial valley during the obs deployment and within the array seismicity was primarily composed of a relatively constant background rate and two large aftershock sequences that included 5 teleseismic events with magnitudes between 4 0 and 4 5 the aftershock sequences were located on the western side of the axial valley adjacent to the atlantis massif and close to the ridge transform intersection they follow omori s law and constitute more than half of the detected earthquakes the obs data also indicate a low but persistent level of seismicity associated with active faulting within the atlantis massif in the same region as the hydroacoustically detected seismicity within the massif the data indicate a north south striking normal fault and a left lateral strike slip fault near a prominent transform parallel north facing scarp both features could be explained by changes in the stress field at the inside corner associated with weak coupling on the atlantis transform alternatively the normal faulting within the massif might indicate deformation of the detachment surface as it rolls over to near horizontal from an initial dip of about 60 beneath the axis and the strike slip events may indicate transform parallel movement on adjacent detachment surfaces