surface water and groundwater contaminations and the resultant hydrochemical evolution in the yongxiu area west of poyang lake china major ion and stable hydrogen and oxygen isotopic compositions were employed in this study of surface water and groundwater contaminations and their impacts on intrinsic hydrochemical evolution in the yongxiu area west of poyang lake south china a total of 36 samples were collected from surface water and groundwater in the study area where water pollution risk is high due to the fertilizer use for farmland and the waste drainage from a nearby silicon industry site the results show that the surface water bodies have been badly polluted and are characterized by low ph values minimum 2 85 and high concentrations of chemical compounds such as cl na nh4 n no3 n and tds groundwater has also been polluted with the similar specific contaminates as both surface water and groundwater may have similar contamination sources and groundwater is recharged from the precipitation infiltration and surface water leakage as indicated by oxygen 18 and deuterium compositions due to the thin unsaturated zone in the area the acidification and the intrusion of contamination further lead to hydrogeochemical reactions and changed hydrochemical type of groundwater from ca mg hco3 to ca mg na cl the data evaluation methods and results of this study could be useful to the water sustainable usage management in this area and other environmental vulnerable areas

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

damped regional scale stress inversions methodology and examples for southern california and the coalinga aftershock sequence 1 we present a new focal mechanism stress inversion technique to produce regional scale models of stress orientation containing the minimum complexity necessary to fit the data current practice is to divide a region into small subareas and to independently fit a stress tensor to the focal mechanisms of each subarea this procedure may lead to apparent spatial variability that is actually an artifact of overfitting noisy data or nonuniquely fitting data that does not completely constrain the stress tensor to remove these artifacts while retaining any stress variations that are strongly required by the data we devise a damped inversion method to simultaneously invert for stress in all subareas while minimizing the difference in stress between adjacent subareas this method is conceptually similar to other geophysical inverse techniques that incorporate damping such as seismic tomography in checkerboard tests the damped inversion removes the stress rotation artifacts exhibited by an undamped inversion while resolving sharper true stress rotations than a simple smoothed model or a moving window inversion we show an example of a spatially damped stress field for southern california the methodology can also be used to study temporal stress changes and an example for the coalinga california aftershock sequence is shown we recommend use of the damped inversion technique for any study examining spatial or temporal variations in the stress field

intrabasin variability of the carbon isotope record across the permian triassic transition sverdrup basin arctic canada abstract a major late paleozoic depocentre the sverdrup basin canadian high arctic has been largely left out of the latest permian extinction debate as early workers presumed middle to late permian strata were absent basin scale sequence stratigraphic and chemostratigraphic correlations indicate late permian strata are only missing on the basin margins where they were removed by sub triassic erosion whereas continuous deposition is recorded in the basin centre the varying degree of sub triassic erosion has significant impact on the carbon isotope record across the latest permian extinction event where both the apparent rate and magnitude of carbon isotope shift vary as a function of basin position the intrabasin variability in apparent 13corg shift across the event is equivalent to that observed globally in contrast to the abrupt isotope shifts recorded on the basin margin similar to many records reported globally the basin centre section shows a systematic shift associated with the latest permian extinction the earth likely underwent a prolonged period of increasing environmental stress leading up to the event

the state of stress in an overriding plate situated above a flat slab the andes of central peru in the andes of central peru that are situated above a flat dipping slab analysis of both structural data collected in the field and available focal mechanisms show that the quaternary and recent state of stress is characterized by n s trending extension in the western cordillera and along the pacific coast whereas e w trending compression prevails in the sub andean lowlands and at the contact between the nazca and south american plates the eastern cordillera deformations suggest an intermediate state of stress i e strike slip faulting characterized by e w trending compression and n s trending extension thus major fault zones striking nw se i e parallel to the central peruvian andes are normal with a sinistral component in the western cordillera e g cordillera bianca and reverse sinistral in the eastern cordillera e g cordillera de huaytapallana this state of stress displays similarities with that of southern peru and may be also interpreted as an effect of compensated high topography in this model the vertical stress zz increases with the topography and hmax is considered as fairly constant trending e w roughly parallel to the convergence on both edges of the andes tectonics being compressional zz is 3 and hmax is 1 in the high andes zz becomes 1 then hmax is 2 allowing hmin striking n s to be 3 along the pacific coast tectonics is not compressional as expected and a nearly neutral state of stress may be due to a topographical effect related to the nearby deep peru chile trench however a conspicuous difference occurs in the andes of central peru in respect to the southern peru andes compressional strike slip tectonics is observed in the eastern cordillera indeed the mean elevation of the eastern cordillera is 3 7 km whereas that of the western cordillera is 4 2 km allowing an intermediate state of stress to occur therefore in central peru a lower mean andean topography and a stronger coupling consequence of the flat subduction seems to explain that compressional tectonics is distributed in a more widespread area than in southern peru superficial deformations related to the subduction of the aseismic nazca ridge are restricted to the coastal domain opposite to this ridge they support the fact that submarine topography of large extension may subduct without producing compressional deformation in the overriding plate which can be reminiscent of a collisional setting

inversion of field data in fault tectonics to obtain the regional stress i single phase fault populations a new method of computing the stress tensor summary we attempt a general definition of the inverse problem of computing the components of the regional stress tensor from a set of field data including the measurements of the strike and dip of several faults and the directions and senses of relative motion along these faults as indicated by slickenslides in previous treatments of this problem no experimental errors could be taken into account except those in measuring the pitch of slickenslides thus errors in the orientation of the fault strike and dip which have considerable practical importance were neglected in our work all experimental errors in the field measurements are taken into account so that the agreement between the computed stress tensor and the set of field measurements can be rigorously checked

processes of water rock interaction in the turonian aquifer of oum er rabia basin morocco possible water rock interaction processes in the moroccan basin of oum er rabia were discussed by a geochemical study of groundwater from the turonian limestone aquifer the most important water resource in the region different types of water according to the classification of piper were defined waters have shown an evolution from dominant cho3 ca mg type through mixed to so4 cl ca mg type the use of geochemical diagrams and chemical speciation modeling method has shown that water rock interaction is mainly controlled by carbonate and anhydrite dissolution ion exchange and reverse ion exchange processes water rock equilibrium conditions are favorable for the precipitation of calcite dolomite kaolinite and magnesian smectite

mesozoic c cycle perturbations and climate evidence for increased resilience of the cretaceous biosphere to greenhouse pulses the mesozoic c isotope record traces the history of the global carbon cycle major perturbations of the carbon cycle triggered by extraordinary volcanic activity are recorded in negative spikes cou

periodic variation of stress field in the koyna warna reservoir triggered seismic zone inferred from focal mechanism studies abstract the koyna warna region in western india is globally recognized as the premier site of reservoir triggered seismicity rts associated with the koyna and warna reservoirs the region is characterized by continuous seismic activity observed since several decades including the world s largest triggered earthquake of m6 3 which occurred in koyna in 1967 while the role of reservoirs in triggering earthquakes has been widely discussed the actual tectonic mechanism controlling earthquake genesis in this region is hardly understood the koyna warna region is exclusively governed by earthquakes of strike slip and normal fault mechanism distinct from the thrust faulting seen in other active zones in the indian region in the present study a comprehensive catalog of 50 focal mechanism solutions of earthquakes that occurred during the last 45 years in the koyna warna region is developed both from previous literature and from moment tensor inversion studies by the authors using broadband data from a local seismic network operating since 2005 the seismicity and fault plane data have enabled precise delineation of trends of the major causative faults which are further accentuated using the double difference technique stress inversion of the focal mechanism data has provided the best fitting principal compressive and tensile stress field of the region which in conjunction with the deciphered fault zones provides a feasible model of seismogenesis in this region based on the observed temporal variation of faulting mechanism a model of alternating cycles of predominantly strike slip and normal faulting is proposed which is attributed to a periodic peaking and relaxation respectively of the horizontal compressive stress field in this region due to the indian plate collision with eurasia

stress and strain from earthquakes at the southern termination of the taupo volcanic zone new zealand abstract we use first motion polarity data from small earthquakes recorded by a recent dense seismograph deployment to determine 16 new focal mechanisms at the southern termination of the taupo volcanic zone tvz these crustal earthquakes are between 11 km and 41 km deep and have focal mechanisms which range from normal to strike slip we then combine these focal mechanism data with previously determined focal mechanisms to investigate earthquake strain directions a prominent feature of the combined data is the consistency of the t axes which indicates that subhorizontal nnw extensional strain predominates at all depths in the crust at the southern termination of the tvz we then use all currently available first motion data to invert for the stress tensor orientation first motion data from earthquakes throughout the crust show a consistent minimum principal stress 3 orientation which is subhorizontal and oriented nw the 3 azimuth that we observe 316 is perpendicular to the strike of recent aligned vents in the southern tvz very similar to the extension direction in the ruapehu segment of the tvz determined from structural data and consistent with the 3 direction determined from a stress inversion using crustal earthquakes in the central tvz north of lake taupo this suggests that the stresses driving the opening of the tvz continue to be active at its southern termination the stress and strain results combined with the earthquake distribution are consistent with a model where the tvz is only the present day surface expression of an extensive region of active mantle corner flow that is progressively eroding thicker crust to the south we also investigate the temporal evolution of stress around mt ruapehu the southernmost large andesitic volcano in the tvz given previous suggestions that this may change during the eruption cycle we find no major change in the stress tensor orientation at the time of the 1995 eruption using first motion data from earthquakes 15 20 km from the volcano

abnormal pollen grains an outcome of deteriorating atmospheric conditions around the permian triassic boundary records of abnormal gymnosperm pollen morphotypes from coeval localities in russia and nw china provide independent and unique evidence of deteriorating atmospheric conditions at the close of the permian although at similar palaeolatitude the vologda region of european russia and the junggar basin of xinjiang province china were thousands of kilometres apart and on different tectonic plates the co occurrence of the megaspore otynisporites eotriassicus fuglewicz 1977 and its restricted distribution elsewhere in marine sections with either late permian ammonoids or the basal triassic conodont marker hindeodus parvus confirms the age range and correlation of the russian and nw chinese sections in three chinese sections rapid changes in carbon isotopic 13 c org composition of between 4 and 10 occur over the intervals showing abnormal pollen these patterns reflect bioclastic facies contributions responding to local environmental changes they are nevertheless coincident with global perturbations in the atmosphere caused by extensive volcanic activity around the permian triassic boundary

vulnerability mapping of the turonian limestone aquifer in the phosphates plateau morocco turonian limestones are an important source of water indispensable for industrial urban and agricultural development in the phosphates plateau this is an elaboration of a vulnerability map of the aquifer based on a multicriterion approach according to the drastic charter that serves as a tool for assessment management and protection of the groundwater quality

heterogeneities in stress and strength in tohoku and its relationship with earthquake sequences triggered by the 2011 m9 tohoku oki earthquake inland tohoku has been recognized as under the wnw ese compressional stress state before the 2011 m9 tohoku oki earthquake earthquakes that occurred there were characterized by reverse faulting with the compressional axis oriented in almost the wnw ese direction the tohoku oki earthquake reduced this wnw ese compressional stress and therefore should have suppressed the earthquake occurrence however several intensive earthquake sequences were triggered in inland tohoku in this study we investigated the triggering mechanism of these remote earthquake sequences in the stress shadow based on the detailed distribution of stress orientations newly determined from pre mainshock focal mechanism data the spatial distribution of stress orientations shows that there exist some regions with anomalous stress fields even before the tohoku oki earthquake on the spatial scale of a few tens of kilometers this spatial heterogeneity in the stress field suggests that the differential stress magnitude in inland tohoku is low a few tens of mpa locations of the earthquake clusters tend to correspond to regions where the principal stress axis orientations of the pre mainshock period are similar to those of the static stress change by the tohoku oki earthquake this observation suggests that these earthquake sequences were triggered by a local increase in differential stress due to the static stress change however a few swarm sequences occurred in central tohoku with delays ranging from a few days to few weeks after the tohoku oki earthquake despite the reduction in differential stress these sequences have notable characteristics including upward migration of hypocenters such features are similar to the fluid injection induced seismicity the source regions of these swarms are located near the ancient caldera structures and major geological boundaries the swarm activities were probably triggered by the upward fluid movement along such pre existing structures these observations demonstrate that information about the temporal evolutions of both stress and frictional strength is necessary to understand the triggering mechanism of earthquakes

controls on the distribution of major ions in pore waters of a thick surficial aquitard transport and geochemical processes controlling the chemical and isotopic composition of pore waters in the upper 45 m of a thick surficial clay rich till battleford formation were studied the upper 3 m of the till is oxidized and fractured the remaining 77 m of the till the aquitard is nonfractured and unoxidized concentrations of total dissolved solids so42 na mg2 and k decrease with depth through the unoxidized zone to a depth of about 15 m below ground below which the concentrations remain constant a similar trend was observed for alkalinity however the decrease in concentration occurs over 20 m in contrast to these ions ca2 concentrations increase with depth through the upper 20 m unoxidized zone below which the concentrations remain relatively constant the distribution of dissolved ions shows the presence of two end members elevated solute concentrations in the oxidized zone attributed to geochemical weathering that occurred since the start of the holocene and connate pleistocene age water at depths between 20 and 45 m abiotic and biotic geochemical reaction rates in the aquitard were shown to be extremely slow or not occurring

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

non climatic factors and the environmental impact of volcanic volatiles implications of the laki fissure eruption of ad 1783 studies of the potential of icelandic volcanic eruptions to modify the environment of the british isles have primarily concentrated on the degree of induced climate change but models and temperatu

crustal structure and seismotectonics of central sicily southern italy new constraints from instrumental seismicity summary in this paper we propose a new model of the crustal structure and seismotectonics for central sicily southern italy through the analysis of the depth distribution and kinematics of the instrumental seismicity occurring during the period from 1983 to 2010 and its comparison with individual geological structures that may be active in the area the analysed data set consists of 392 earthquakes with local magnitudes ranging from 1 0 to 4 7 we defined a new detailed 1 d velocity model to relocate the earthquakes that occurred in central sicily and we calculated a moho depth of 37 km and a mean vp vs ratio of 1 73 the relocated seismic events are clustered mainly in the area north of caltanissetta e g mainland sicily and in the northeastern sector madonie mountains of the study area only minor and greatly dispersed seismicity is located in the western sector near belice and along the southern coast between gela and sciacca the relocated hypocentral distribution depicts a bimodal pattern 50 per cent of the events occur within the upper crust at depths less than 16 km 40 per cent of the events occur within the middle and depth crust at depths between 16 and 32 km and the remaining 10 per cent occur at subcrustal depths the energy release pattern shows a similar depth distribution on the basis of the kinematic analysis of 38 newly computed focal plane solutions two major geographically distinct seismotectonic domains are distinguished the madonie mountain domain with prevalent extensional and extensional oblique kinematics associated with upper crust late pliocene quaternary faulting and the mainland sicily domain with prevalent compressional and compressional oblique kinematics associated with thrust faulting at mid to deep crust depth along the north dipping sicilian basal thrust sbt the stress inversion of the mainland sicily focal solutions integrated with neighbouring mechanisms available in the literature highlights a regional homogeneous compressional tensor with a subhorizontal nnw sse striking 1 axis in addition on the basis of geodetic data the mainland sicily domain may be attributed to the sse ward thrusting of the mainland sicily block along the sbt plane seismogenic shearing along the sbt at mid crustal depths was responsible for the unexpected belice 1968 earthquake mw 6 1 with evident implications in terms of hazard assessment

evidence for atmospheric pollution across the permian triassic transition evidence for a cause and effect relationship between the emplacement of the siberian traps large igneous province and the permian triassic marine mass extinction has been growing over the past decades however how the siberian traps volcanism affected the terrestrial vegetation is still a matter of controversy here we demonstrate that a substantial part of plants life cycle namely their reproductive organs was adversely affected by environmental conditions effects include malformed spores and pollen grains unseparated tetrads and darkened walls of spores and pollen sporoderm from permian triassic sediments from the finnmark platform offshore norway the co occurrence of these morphological changes with the main carbon isotope excursion and the marine mass extinction may suggest that they were caused by atmospheric pollution linked to siberian traps emissions

interaction of faults and perturbation of slip influence of anisotropic stress states in the presence of fault friction and comparison between wallace bott and 3d distinct element models abstract two decades after their birth the validity of fault slip inversion methods is still strongly debated these methods are based upon a very simplified mechanical background the wallace bott hypothesis following previous studies the 3d distinct element method 3dec software is used to explore the effect of varying stress anisotropy i e the shape ratio on slip perturbation along pairs of faults two end member configurations are modelled in taking into account fault friction and internal deformation of faulted blocks the first model deals with a relatively simple case where two nonintersecting conjugate normal faults are reactivated in an oblique normal stress regime the second one simulates an extreme situation where two perpendicular intersecting faults are submitted to oblique extension the average direction of fault slip predicted by 3dec models is compared to the corresponding slip predicted by the simplified wallace bott model for the two simulated cases it is shown that results from 3dec and wallace bott models are mutually consistent and argue for the validity of fault slip data inversion methods consistency remains even if slip is significantly deviated near the intersection line of faults these deviations depend on the degree of anisotropy of applied stresses in presence of fault friction furthermore modelling results suggest that for intersecting faults with convergent slip directions consideration of fault friction in the models leads to reduction of slip perturbation in other words modelling results lead to the nonintuitive conclusion that the validity of the simplified wallace bott model is strengthened when 3dec model s complexity i e the number of parameters incorporated increases

floral changes across the triassic jurassic boundary linked to flood basalt volcanism one of the five largest mass extinctions of the past 600 million years occurred at the boundary of the triassic and jurassic periods 201 6 million years ago the loss of marine biodiversity at the time has been linked to extreme greenhouse warming triggered by the release of carbon dioxide from flood basalt volcanism in the central atlantic ocean in contrast the biotic turnover in terrestrial ecosystems is not well understood and cannot be readily reconciled with the effects of massive volcanism here we present pollen spore and geochemical analyses across the triassic jurassic boundary from three drill cores from germany and sweden we show that gymnosperm forests in northwest europe were transiently replaced by fern and fern associated vegetation a pioneer assemblage commonly found in disturbed ecosystems the triassic jurassic boundary is also marked by an enrichment of polycyclic aromatic hydrocarbons which in the absence of charcoal peaks we interpret as an indication of incomplete combustion of organic matter by ascending flood basalt lava we conclude that the terrestrial vegetation shift is so severe and wide ranging that it is unlikely to have been triggered by greenhouse warming alone instead we suggest that the release of pollutants such as sulphur dioxide and toxic compounds such as the polycyclic aromatic hydrocarbons may have contributed to the extinction

stress rotation in the kachchh rift zone gujarat india double difference relocations of the 1402 kachchh events 2001 2006 clearly delineate two fault zones viz south dipping north wagad fault nwf and almost vertical gedi fault gf the relocated focal depths delineate a marked variation of 4 and 7 km in the brittle ductile transition depths beneath gf and nwf respectively the focal mechanism solutions of 464 aftershocks using 8 12 first motions show that the focal mechanisms ranged between pure reverse and pure strike slip except for a few pure dip slip solutions the stress inversions performed for five rectangular zones across the kachchh rift reveal both clockwise and anticlockwise rotation 7 32 in the 1 orientation within the rupture zone favoring a heterogeneous stress regime with an average n s fault normal compression this rotation may be attributed to the presence of crustal mafic intrusives 5 35 km depth in the rupture zone of the 2001 bhuj main shock results suggest a relatively homogeneous stress regime in the gf zone favoring strike slip motion with a fault normal n s compression

temporal and spatial variation of local stress fields before and after the 1992 eruptions of crater peak vent mount spurr volcano alaska we searched for changes in local stress field orientation at mount spurr volcano alaska between august 1991 and december 2001 this study focuses on the stress field orientation beneath crater peak vent the site of three eruptions in 1992 and beneath the summit of mount spurr local stress tensors were calculated by inverting subsets of 140 fault plane solutions for earthquakes beneath crater peak and 96 fault plane solutions for earthquakes beneath mount spurr we also calculated an upper crustal regional stress tensor by inverting fault plane solutions for 66 intraplate earthquakes located near mount spurr during 1991 2001 prior to the 1992 eruptions and for 11 months beginning with a posteruption seismic swarm the axis of maximum compressive stress beneath crater peak was subhorizontal and oriented n67 76 e approximately perpendicular to the regional axis of maximum compressive stress n43 w the strong temporal correlation between this horizontal stress field rotation change in position of the 1 3 axes relative to regional stress and magmatic activity indicates that the rotation was related to magmatic activity and we suggest that the crater peak stress field rotation resulted from pressurization of a network of dikes during the entire study period the stress field beneath the summit of mount spurr also differed from the regional stress tensor and was characterized by a vertical axis of maximum compressive stress we suggest that slip beneath mount spurr s summit occurs primarily on a major normal fault in response to a combination of gravitational loading hydrothermal circulation and magmatic processes beneath crater peak online material regional and local fault plane solutions

solute and isotopic geochemistry and ground water flow in the central wasatch range utah ground water flow systems in the rugged central wasatch range utah were investigated by solute and isotopic methods six types of ground water systems were identified on the basis of rock type and structure the systems are broadly grouped into four categories 1 granitic systems 2 non granitic systems a unconsolidated alluvial systems b consolidated sedimentary rock systems and c fault controlled systems 3 thermal systems 4 mine drainage systems these ground water systems have distinctive solute and isotopic chemistries based on an analysis of 3h and 14c data all of the ground waters have a component of post 1952 recharge water and most of the ground waters are composed almost entirely of post 1952 recharge water a few of the ground water systems contain some water which is hundreds to perhaps thousands of years old the 18o and 2h data plot on a local meteoric water line and none of the data exhibit a positive 18o shift the absence of a positive 18o shift suggests maximum aquifer temperatures are approximately 100 c granitic terrains are dominated by fracture controlled local ground water flow systems which respond rapidly to recharge events the granitic ground water systems have estimated maximum circulation depths of about 160 m below land surface all the alluvial most of the consolidated sedimentary bedrock and some of the fault controlled ground water systems are shallow circulating local flow systems with short travel times ground water circulation of most of the local flow systems is within 200 m of land surface and is bedding plane controlled some of the consolidated bedrock and many of the fault controlled ground water systems are of the intermediate type and have circulation depths to 500 m four thermal ground water systems have been identified the thermal systems are heated by the geothermal gradient and have not circulated deeper than 2 2 5 km the thermal systems are of the intermediate and regional type the solute chemistry of most of the non granitic ground waters may be attributed to the dissolution of carbonate minerals and minor amounts of gypsum contributions of external co2 g to some of the thermal systems from either metamorphic or silicate hydrolysis processes is suspected

a stress inversion procedure for polyphase fault slip data sets palaeostress estimation from striated fault data is frequently frustrated by the fact that natural fault data are heterogeneous in the sense that they cannot satisfactorily be explained by reactivation brought about by a single stress tensor in many instances there is clear evidence to show that striation data can record the effects of multiple stress events any attempt to find the tensor which best fits or explains such dynamically mixed data sets risks determining a spurious stress state which is some form of compromise between the real stress states corresponding to different tectonic phases to avoid this problem a strategy is proposed here which involves an initial separation of the raw data into coherent sub sets prior to formal stress inversion this separation is performed by assigning attributes to each fault which describe the fault s compatibility with trial stress tensors using these attributes faults can be grouped into dynamically homogeneous families using the statistical techniques of cluster analysis

the little skull mountain nevada earthquake of 29 june 1992 aftershock focal mechanisms and tectonic stress field implications the ml 5 6 29 june 1992 little skull mountain earthquake occurred in the southern nevada test site nye county nevada within 20 km of a potential national nuclear waste repository at yucca mountain nevada while microseismicity in the immediate epicentral vicinity occurred for years prior to the mainshock foreshock activity ml 2 were also sufficiently well recorded to provide local network p wave focal mechanism solutions the mainshock and the majority of the aftershocks through september 1992 display predominantly normal slip focal mechanisms but unambiguous strike slip and oblique slip focal mechanism solutions are also present in the aftershock series the mainshock and immediate foreshock depths were 10 1 km below sea level and depths of focus of aftershocks range from about 6 to 12 km a large subset of the aftershock hypocenters define a southeast dipping structure probably the mainshock fault plane no variation of mechanism style with depth is apparent two mainshock and 84 aftershock focal mechanism solutions were input into gephart s 1990 stressfield inversion program and principal compressional stress directions j j 1 2 3 were determined as well as the stress difference ratio r 1 2 1 3 the results indicate a uniform stress field in which 3 minimum stress is oriented 116 5 azi plunge and 1 maximum stress is oriented 219 69 with r 0 35 the inversion s selection of preferred nodal planes invokes bott s 1959 criterion which states that slip occurs in the direction of resolved shear traction on preexisting fault surfaces for the predominantly normal slip little skull mountain earthquake mechanisms having northeast striking planes the southeast moderately to steeply dipping dip 55 nodal planes are selected however for the dip slip earthquake mechanisms exhibiting more northerly trending strikes shallowly to moderately west dipping 25 dip 65 nodal planes are selected when a coulomb mohr analysis was applied to the focal mechanisms using the above principal stress directions and an assumed ratio 1 3 the ratio of resolved shear stress to normal stress n on the southeast dipping nodal plane of the mainshock exhibited a near maximum level suggesting a high fault strength in contrast a wide range of fault strengths or apparent coefficients of friction was suggested by the n ratios for little skull mountain aftershock preferred nodal planes seismicity on misoriented faults i e those on which shear stress was relatively low may have been the result of a temporarily elevated fluid pore pressure following the mainshock

stress field in the northern rhine area central europe from earthquake fault plane solutions abstract fault plane solutions fps from 110 earthquakes in the northern rhine area with local magnitudes ranging from 1 0 to 6 1 and occurring between 1976 and 2002 are determined fps are retrieved from p wave first motions using a grid search approach allowing a detailed exploration of the parameter space the influence of the 1d velocity model on take off angles and resulting fps is examined all events were relocated with a recently developed minimum 1d model of the velocity structure j geophys res 2003 rose diagrams of the orientation of p t and b axes show a clear preference of trends of p and t axes at n292 e and n27 e respectively the majority of b axes trend in northerly directions plunges of p and t axes are mostly around 45 while most b axes are subhorizontal the main direction of the maximum horizontal stress directly inferred from the fault plane solutions is n118 e to calculate the orientations of the principal stress axes and the shape of the stress tensor the inversion method of gephard and forsyth j geophys res 89 1984 9305 was applied to the whole data set and to several subsets of data the subsets were formed by grouping events from various geological and tectonic areas and by grouping events into different depth ranges the subset areas include the lower rhine embayment the rhenish massif the middle rhine area the neuwied basin and the area known as the stavelot venn massif inversion of the entire data set shows some ambiguity between a strike slip and extensional stress regime with a vertical axis for the medium principal stress and a trend of n305 e and n35 e for the 1 and 3 axis respectively as the best fitting tensor earthquakes from the lower rhine embayment and to some degree from the middle rhine area indicate an extensional stress regime in the lower rhine embayment plunge and trend of the 1 axis are 76 and n162 e and for the 3 axis 7 and n42 e the best fitting solution for the area of the stavelot venn massif is a strike slip regime with subhorizontal 1 and 3 axes with a trend of n316 e and n225 e respectively stress orientations found here agree overall with the results from earlier studies based on smaller data sets the directions of the maximum and minimum horizontal stresses inverted from focal mechanisms agree well with the stress field predicted by the european stress map this confirms earlier interpretations that the stress field of the rhine graben system is controlled by plate driving forces acting on the plate boundaries however amplitudes of the stresses change on a local scale and with depth estimates of the absolute magnitude of principal stresses favor a normal faulting regime in the shallow crust above 12 km depth and a strike slip regime in the lower crust

existence of interplane earthquakes and neutral stress boundary between the upper and lower planes of the double seismic zone beneath tohoku and hokkaido northeastern japan abstract using data from the recently constructed nationwide dense seismic network we determined the hypocenters and focal mechanisms of many intermediate depth intraslab earthquakes within the pacific slab beneath northeastern japan the results show that in addition to the upper and lower planes of the double seismic zone a considerable number of intraslab earthquakes also occur between the two planes this interplane earthquake activity is not homogeneously distributed in space being high beneath eastern hokkaido and the fore arc regions of southeast and central tohoku the focal mechanisms of the interplane earthquakes tend to be of the down dip compressional type dc in tohoku and the hokkaido corner but down dip tensional type de in eastern hokkaido upper plane earthquakes are characterized by dc type stress while lower plane earthquakes are de type in both tohoku and eastern hokkaido the existence of interplane earthquakes enables estimation of the position of the neutral plane between the upper plane dc stress and the lower plane de stress we did so by applying stress tensor inversions to focal mechanism data obtained in the present study and japan meteorological agency jma data the results show that the neutral plane is located about 22 km beneath the upper plate interface beneath tohoku but only about 10 km beneath the upper surface beneath eastern hokkaido this difference in the location of the neutral plane may be due to the difference in buoyancy force exerted by the less dense metastable olivine wedge that is a result of the oblique plate subduction beneath hokkaido comparison of large intraslab earthquakes beneath the two regions shows that their aftershock areas are limited by the neutral plane suggesting that large earthquake ruptures are confined to either the dc or de stress field and do not go beyond the neutral plane

fracture coalescence as a mechanism for earthquakes observations based on mining induced microseismicity abstract microseismic events with magnitudes less than zero recorded within a volume at depth in an underground mine are used to evaluate failure conditions associated with a magnitude 2 9 event rockburst the approach incorporated several independent methods of analysis including the principal component analysis pca of seismicity focal mechanisms stress inversion underground in situ stress measurements and structural mapping and three dimensional numerical modelling derived stresses a good correlation was found between stress inversion and pca derived microseismic failure planes and structural mapping and between the in situ principal stress orientations and those obtained through stress inversion and numerical modelling a few days prior to the large event and during the aftershock sequence a change in microseismic failure plane orientation to a shallower dip angle than mapped underground was found to coincide with the numerical modelling derived plane of maximum slip potential this orientation along with measured fracture characteristics persistence and spacing and an increase in event clustering into the plane suggests that the formation of the large event plane of rupture was likely related to the coalescence of mapped fractures an observed reduction in stress release accompanying the increased tendency towards planarity prior to the large event indicates that the development of a large rupture surface occurred under an increased effective shear stress build up as part of the earthquake generation process and the process of coalescence can be considered as the breakage of barriers new fracture growth accompanied by an increase in the effective shear stress on the remaining asperities pre existing fractures

constraining geomechanical models by using microseismic derived fractures from source mechanisms geomechanical modeling of hydraulic stimulations requires data to build and calibrate models to predict decline curves and other aspects of long term reservoir performance initialization of these models requires knowledge of the preexisting fractures and geologic properties of the media orientations of different fracture sets their intensities and spacing along with characterization of their size scales critically impact geomechanical predictions of the stimulations in terms of proppant and fluid placement and the decline of reservoir productivity with sufficient sampling of azimuths around the stimulation the mechanisms and associated fracture planes and stress strain conditions can be reconstructed through seismic moment tensor inversion smti of recorded microseismic event waveforms at smaller scale lengths signal to noise ratios can be low and events might not be observed at high enough quality to permit smti to extend the characterization of these fractures to smaller scales a stochastic optimization algorithm is used designed to search for optimally placed fractures in the reservoir that intersect with event locations while constraining their orientations from the same distribution observed at larger smti resolvable length scales effectively this technique allows for extension of the power law governing fracture distribution to smaller scales by invoking observed trends in self similar behavior in turn characterization of the wider band of fractures in the reservoir provides necessary inputs into geomechanical models to predict fluid and proppant distributions from the full band of generated microseismicity and long term behavior of the reservoir through decline curve estimation

determination of the stress field in a mountainous granite rock mass abstract the design of an underground hydroelectric power scheme in northern portugal has required the characterisation of the local stress field nineteen hydraulic tests have been conducted in two 500 m deep vertical boreholes in addition twelve overcoring tests together with twelve flat jack tests have been performed from an existing adit located some 1 7 km away from the location of the hydraulic tests results have been integrated into a stress model that takes into account both topography and tectonics effects most of the data are consistent with a linearly elastic gravity loaded model provided a very soft geomaterial is considered this implies that the stress field in this granite rock mass is controlled by gravity alone and shear stress relaxation along faults and fractures but is unaffected by present day tectonics

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

delineation and interpretation of seismotectonic domains in western north america indicators of crustal stress and regional seismicity are used to delineate six seismotectonic domains in western north america the san andreas east central california ecc mendocino triple junction mtj and pacific northwest pnw domains are found to have similar stress fields although the style and rate of deformation in each is different we propose that all of these domains are generated by shear between the pacific and north american plates in the mtj and pnw domains this shear may be evidence for the initiation of a transform fault connection between the san andreas and the queen charlotte island fault systems the ecc a region including much of the sierra nevada appears to result from the relatively stiff nature of the san andreas fault system the big bend and region of relatively new faulting in northern california act to make the san andreas fault system appear stiff on a regional scale two other domains the northern basin and range nbr and the intermountain seismic belt isb show evidence of being controlled by more local forces the nbr has been heated and uplifted in the past and is presently extending to the northwest because of a release of tectonic compression at the juan de fuca north america plate boundary the isb can be explained by readjustments between the colorado plateau and the basin and range province which may be caused by the lowering of the basin and range due to extension

the state of stress near the mendocino triple junction from inversion of earthquake focal mechanisms focal mechanisms of 70 earthquakes occurring in the region of the mendocino triple junction between 1977 and 1995 are inverted to obtain the regional stress orientations and relative magnitudes in this technically complex area a diverse set of earthquake geometries is consistent with a single stress field characterized by north northwest horizontal maximum principal compressive stress although this stress direction is almost perpendicular to convergence between the north american and gorda plates it is consistent with the stress direction inferred within the gorda plate northwest of the triple junction a maximum compressive stress direction nearly parallel to strike of the cascadia subduction zone implies very low resolved shear stress across this plate boundary evidence for failure along the southernmost section of the cascadia subduction zone comes from the occurrence of the recent 1992 ms 7 1 cape mendocino underthrusting earthquake as well as from measurements of holocene surface uplift consistent with the 1992 coseismic uplift pattern rupture of the cascadia subduction zone under this stress regime requires that the southernmost region of the gorda north american plate boundary is weak

seismicity and seismotectonics study in southwestern albania using a local dense seismic network abstract the albanides represent a complex orogen made up of a heterogeneous tectonic nappe pile of paleozoic mesozoic and cenozoic domains albania is tectonically active and moderate to strong earthquakes have occurred in the past however abundant microseismicity has not been monitored and studied by a dense seismic network during this study a seismic network of 40 stations was deployed in southern albania for one year a total of 2113 microearthquakes were well located the most accurately located events and 810 focal mechanisms were used in order to define the seismotectonics and the stress pattern in the area results indicate that thrust and strike slip faulting both exist in southwestern albania suggesting a continuation of the complex tectonic setting of the neighboring northwestern greece to the north

an example of stress tensor distribution deduced from the aftershocks of the november 23 1980 southern italy earthquake abstract the total inversion algorithm tarantola and valette 1982 is applied to a set of focal mechanisms corresponding to the aftershocks of the southern italy november 23 1980 earthquake m s 6 9 and the elements of several stress tensors are computed the obtained complex distribution of stress for this region is analyzed and two zones around the main event corresponding to areas of tension and compression distributed at different depths are delimited a stress tensor was sought for a third region corresponding to events which occurred along the strike of the main event and with magnitudes greater than 2 2 but with ambiguous results

are late permian carbon isotope excursions of local or of global significance we present a new biostratigraphically calibrated organic and inorganic c isotope record spanning the basal late permian to earliest triassic from southern guizhou nanpanjiang basin south china after fluctuations of a likely diagenetic overprint are removed three negative carbon isotope excursions cies persist these include a short lived cie during the early wuchiapingian a protracted cie ending shortly after the wuchiapingian changhsingian boundary and a third cie straddling the permian triassic boundary comparison of our new c isotope record with others from the same basin suggests that influences of local bathymetry and of the amount of buried terrestrial organic matter are of importance comparison with other coeval time series outside of south china also highlights that only the negative cie at the permian triassic boundary is a global signal these differences can be explained by the different volumes of erupted basalts between the late permian emeishan and the younger siberian large igneous provinces and their distinct eruptive modalities emeishan volcanism was largely submarine implying that sea water was an efficient buffer against atmospheric propagation of volatiles the equatorial position of emeishan was also an additional obstacle for volatiles to reach the stratosphere and benefit from an efficient global distribution consequently the local significance of these cies calls into question global correlations based on c isotope chemostratigraphy during the late permian the timing of the late permian chinese cies is also not reflected in changes in species diversity or ecology unlike the sudden and global permian triassic boundary crisis and subsequent early triassic upheavals

strike slip faulting on the northern margin of the south china sea evidence from two earthquakes offshore of hainan island china in december 1969 in december 1969 two earthquakes mb 4 7and4 8 occurred in a rift basin offshore of hainan island china in a passive continental margin environment by modeling short period p and long period sh waveforms recorded at wwssn stations we have determined the focal mechanisms and source parameters of these two events to be strike 45 7 dip 78 4 rake 6 7 focal depth 8 3 km seismic moment 1 73 0 4 1023 dyne cm and stress drop 56 6 bar for the 17 december event and strike 36 6 dip 60 4 rake 2 7 focal depth 8 3 km seismic moment 1 43 0 13 1023 dyne cm and stress drop 47 6 bar for the 20 december event results of relative location computed from differential arrival times indicate that the 20 december event is slightly deeper than the 17 december event but within the resolution limit of the waveform constraint analysis of the local tectonic setting geometry of isoseismals aftershock distribution and fault plane solutions indicate that the 17 december event probably ruptured along a ne sw striking fault on the northern margin of the songtao uplift in the qiongdongnan basin the 20 december event probably ruptured along another major ne sw striking fault on the northern margin of the qiongdongnan basin the fault motions of both earthquakes were almost pure left lateral strike slip p and t axes show that the epicentral area is subject to nearly horizontal n s directed compression and e w directed extension consistent with previously observed stress field in the area the two earthquakes represent reactivation of pre existing zones of weakness in the basin by the present day tectonic stress field a review of earthquakes in the region indicates that strike slip motion is characteristic of the seismotectonics of the northern margin of the south china sea

correlating seismicity parameters and subsidence in the tokai region central japan 1 we demonstrate that transients in subsidence rate in the tokai area of central japan correlate with changes in the rate and size distribution of earthquakes three largely independent seismic catalogs cover this region national research institute for earth science and disaster prevention nied japanese meteorological agency jma and japan university network catalog junec comparing seismicity patterns between these three data sets offers a unique opportunity to verify seismicity anomalies based on independent sources a study of data quality magnitude reporting consistency and consistency across the three data sources reveals that the nied data for the period 1981 2002 are best suited for seismicity analysis we spatially and temporally map seismicity rates finding that a significant decrease in the earthquake rate of m 2 0 events coincides with an accelerated subsidence period however this anomaly disappears when including smaller magnitudes in the analysis this relative quiescence of larger events can readily be explained when interpreting the transient in seismicity in the framework of a change in the earthquake size distribution or b value the background b value of about 0 8 increased in the period 1987 5 1989 5 to a value of b 1 2 a highly significant change that can be confirmed in all three data sets the correlation between subsidence and b value change is significant stress tensor inversions of focal mechanism data for the anomalous period show an increase in thrusting type earthquakes while a unique interpretation of the relationship between subsidence and b value is not possible we propose that an increase in the locking stress a slow stick event is consistent with all observations

hydrogeological conditions and quality of ground waters in northern banat pannonian basin geological relationships hydrogeology and chemical composition of ground water in northern banat were studied through the period 2000 2004 using the available background data from published and unpublished sources northern banat is the extreme northeastern part of the republic of serbia and a geotectonic part of the vast pannonian depression the source of domestic and industrial water supply is only groundwater from artesian and subartesian aquifers of lower pleistocene q11 and upper pleistocene pl32 sand deposits the ground water peculiar in chemical composition is the only source of drinking water in the arid area a notable variation in the chemical composition of artesian waters within the same geotectonic unit pannonian basin abstracted for municipal water supplies of kikinda novi knezevac and djala has attracted attention of these authors our paper attempts to interpret the variation in the chemical composition of ground water and the cause of the variation by the interaction of ground water and rocks forming the aquifers on the case example of the water supply sources for the three mentioned towns with respect to the depth and lithology of the aquifers we interpret the varied chemical compositions of waters in the mentioned sources as a consequence of natural factors geological environment geological relationships and hydrogeological conditions

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

hyperthermal driven mass extinctions killing models during the permian triassic mass extinction many mass extinctions of life in the sea and on land have been attributed to geologically rapid heating and in the case of the permiantriassic and others driven by large igneous province volcanis

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

mantle plume the invisible serial killer application to the permian triassic boundary mass extinction the earth experienced a severe mass extinction at the permian triassic boundary ptb about 252 million years ago this biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the precambrian time the eruption of the largest continental flood basalt the siberian traps overlapped this mass killing many hypotheses have been proposed but no definitive conclusion currently exits here we present characteristics of three sections from iran and china and propose that an active mantle plume initiated a series of processes which led to the mass mortality and produced major sedimentological mineralogical and geochemical changes observed in the transition from the paleozoic to the mesozoic the injection of mantle plume related igneous dike swarms into the continental margin facilitated the release of massive amounts of ch 4 primarily from the dissociation of marine gas hydrates and secondarily from the maturation of organic rich sediments and fracturing of hydrocarbon reservoirs the bulk of the ch 4 was aerobically oxidized in the water column producing dissolved co 2 with low 13 c values this co 2 saturated seawater became acidic to the point of dissolution of shelf carbonates promoting precipitation of siliciclastic rich strata in the transition from the permian to the triassic methane derived co 2 also lowered carbon isotopic composition of seawater leading to the observed decline in 13 c composition of organic and inorganic marine carbon at the ptb gas charged oceans released large volumes of co 2 and ch 4 into the atmosphere which created a severe global warming the end permian inferno causing the release of additional ch 4 from the dissociation of polar gas hydrates these events lowered 13 c compositions of terrestrial carbon simultaneously feeder dikes from the mantle plume formed the siberian traps flood basalt marine mass extinction was the result of a change in seawater composition due to the injection and oxidation of ch 4 in the water column causing low ph high concentrations of co 2 ca 2 and hco 3 and low co 3 2 values combined with a hot seawater temperature these changes made calcification of marine organisms difficult and produced major physiological crisis including reduced metabolic rates high sensitivity to environmental stress and hampered growth and reproduction terrestrial mass extinction can be attributed to severe global warming and soil acidification produced by increased atmospheric co 2 acid rain that was generated by so 2 derived from the siberian trap eruption and loss of habitat cessation of the plume activity during early triassic stopped the release of ch 4 into the ocean and terminated continental flood basalt eruption ending the environment of death on land and in sea the cut off of co 2 production in the ocean instantly increased carbonate saturation of seawater resulting in extensive seafloor cementation it also resulted in the deposition of marine carbonates by microbial activities in the hostile post extinction environment from the trigger to recovery the perturbation which included the end permian mass mortality could have lasted for at least 2 myr several major mass extinctions of the phanerozoic are temporally accompanied by flood basalt eruptions so far these two events have been interpreted in a cause and effect relation flood basalt eruption causes mass extinction this study proposes that flood basalts and their time correlative biological crises are themselves the consequence of a complex perturbation caused by mantle plume activities if so major disturbances in the near surface of the earth are ultimately controlled by changes in the mantle the physical sedimentological observations presented here combined with previous paleontological evidence cast doubt on other interpretations which use geochemical variables numerical modeling biomarkers and ce anomaly to suggest that late permian ocean was anoxic all the way to the photic zone

latest permian mercury anomalies a sedimentary record from the buchanan lake section canadian high arctic shows anomalous high levels of mercury hg during the latest permian extinction lpe on northwest pangea significant influx of hg progressively overwhelmed the marine system major disruption of the organic matter mediated hg drawdown process resulted in accumulation of dissolved hg to maximum levels at the lpe boundary affecting an already stressed global ecosystem a switch to euxinic marine conditions at the lpe boundary led to chemical drawdown of hg sulfides as marked by progressive hg mitigation this allowed self recovery from toxic hg conditions and ultimately led to reestablishment of the internal hg organic matter drawdown process we hypothesize that anomalous hg levels may be attributed to the significant natural atmospheric emissions caused by catastrophic siberian traps volcanic eruptions

african stress pattern from formal inversion of focal mechanism data abstract the kinematic models and the associated orientation of extensional stress of the east african rift system have been subjected to much debate since a long time in the past decades the proposed models relied on the interpretation of the overall rift geometry geological fault slip data and the few focal mechanisms available these models generally suffer of a poor time control and an underestimation of the possible changes in the stress field and geodynamic regime with time and space in the recent years there has been a significant increase in the number of focal mechanisms available for the entire rift system and it is now possible to estimate the present day stress field in relative detail based on seismotectonic data alone we compile 347 focal mechanism data from the global harvard cmt catalogue and various other sources and grouped 332 of them in 24 distinct regions boxes on the basis of their geographical proximity kinematic homogeneity and tectonic setting for each box and for the same data set reduced stress tensors have been obtained by formal stress inversion using both the tensor program delvaux sperner 2003 and the slick method michael 1984 1987 both inversion methods show in comparable results in terms of horizontal stress axes orientations and tectonic stress regimes which stem for the robustness of the approach the obtained stress pattern reflects a complex interaction between 1st order effects as different driving forces including plate boundary forces and 2nd and 3rd order effects as gravitational potential of topography intra lithospheric processes and the influence of structural heterogeneities of the rift structures the evidence present in the stress orientations of the 2nd and 3rd order stress pattern as the variations in the horizontal stress axes along the axis of the rift are of particular interest as they were not yet captured or shown in earlier numerical models of the stress field additional sources of tectonic forces in supplement to the gravitational potential energy forces as considered in the earlier models are necessary to explain the observed patterns

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

seismicity and s wave velocity structure of the crust and the upper mantle in the baikal rift and adjacent regions abstract correlations between seismicity seismotectonic deformation std field and velocity structure of the crust and the upper mantle in the baikal rift and the adjacent areas of the siberian platform and the mongol okhotsk fold belt have been investigated the 3d s wave velocity structure up to the depths of 500 km has been modeled using a representative sample of rayleigh wave group velocity dispersion curves about 3200 paths at periods from 10 to 250 s the std pattern has been reconstructed from mechanisms of large earthquakes and is in good agreement with gps and structural data analysis of the results has shown that most of large shallow earthquakes fall in regions of low s wave velocities in the uppermost mantle western mongolia and areas of recent mountain building in southern siberia and in zones of their relatively high lateral variations northeastern flank of the baikal rift in the first case the dominant std regime is compression manifested in a mixture of thrust and strike slip deformations in the second case we observe a general predominance of extension

incidences of water rock interaction on natural resources characters oum er rabia basin morocco the oum er rabia basin provides important water resources from a multi layer aquifer system of which the turonian limestone aquifer constitutes the main potential resource the same basin is also known by its wealth in phosphates and comprises the ouled abdoun series the largest moroccan phosphate occurrence the present work attempts to characterize the interaction of natural resources with their impacts on water and phosphates quality hydrogeochemical data on waters of the turonian and the eocene aquifers as well as their petrographical analyses by optical and electronic microscopes and by the x ray diffraction method on weathered and non weathered rocks of relative aquifers have shown that water rock interaction has a large influence on the quality of water and phosphate resources in the oum er rabia basin

moment tensors state of stress and their relation to post glacial rebound in northeastern canada summary in the stable craton of northeastern canada moderate seismicity as well as glacial isostatic adjustment gia has been observed we investigate five earthquakes with moment magnitudes between 3 6 and 4 1 that have occurred in northern hudson bay since 2007 which may be triggered by gia focal mechanisms of the earthquakes are determined using a waveform fitting procedure for surface waves in which the best double couple mechanism is obtained through a grid search over strike dip and rake all events exhibit a thrust fault mechanism in general agreement with mechanisms of previously analysed earthquakes in that area stress inversion results incorporating our new mechanisms as well as previously published results exhibit significant differences from previously calculated stresses from gia models for the first time maximum horizontal stress direction shmax is compared to the modelled stress values for northeastern canada we find that the maximum horizontal stress direction strikes roughly nnw sse in contrast to previously inferred ne sw orientation of shmax our results indicate that the local stress field in northern hudson bay deviates from regional stresses resulting from the existence of a roughly e w oriented zone of faulting which is not included in existing gia models

calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor

fault tectonics of the baja california peninsula and the opening of the sea of cortez mexico abstract a detailed field analysis of neogene and quaternary faults in baja california has enabled us to reconstruct the stress pattern and the tectonic evolution of the central and southern parts of the peninsula the deformation which is related to the opening of the gulf affects the whole peninsula but decreases from east to west most observed faults normal and or dextral strike nnw sse to wnw ese their mechanisms include both strike slip and dip slip as well as intermediate motions compressional events have occurred since late neogene times but were probably of minor quantitative importance because reverse faults are rare and small the principal fault pattern includes dextral nnw sse riedel shears and n s tension faults induced by dextral strike slip along two main nw se fault zones bordering the peninsula the gulf of california to the east which is the most important and the tosco abreojos fault to the west the resulting pattern of deformation shows that the eastern part has been a complex transform extensional zone since late miocene early pliocene times

analyses of the stress field in southeastern france from earthquake focal mechanisms summary owing to the apparent deformation field heterogeneity the stress regimes around the provence block from the fronts of the massif central and alpine range up to the ligurian sea have not been well defined to improve the understanding of the se france stress field we determine new earthquake focal mechanisms and compute the presentday stress states by inversion of the 89 available focal mechanisms around the provence domain including 17 new ones calculated in the current study this study provides evidence of six distinct deformation domains around the provence block with different tectonic regimes on a regional scale we identify three zones characterized by significantly different stress regimes a western one affected by an extensional stress normal faulting regime a southeastern one characterized by a compressional stress reverse to strike slip faulting regime with nnw to wnw trending s1 and a northeastern one namely the digne nappe front marked by a ne trending compression note that the digne nappe back domain is controlled by an extensional regime that is deforming the western alpine core this extensional regime could be a response to buoyancy forces related to the alpine high topography the stress regimes in the southeast of the argentera massif and around the durance fault are consistent with a coherent nnw trending s1 implying a left lateral component of the active reverse oblique slip of the moyenne durance fault in the rhone valley an e trending extension characterizes the tectonic regime implying a normal component of the present day no mes fault displacement this study provides evidence for short scale variation of the stress states which arises from abrupt changes in the boundary force influences on upper crustal fragments blocks these spatial stress changes around the provence block result from the coeval influence of forces applied at both its extremities namely in the northeast the alpine front push and in the southeast the northward african plate drift in addition to these boundary forces the mantle plume under the massif central influences the western block boundary

mapping of groundwater quality in the turonian aquifer of oum er rabia basin morocco a case study this study takes the groundwater of the moroccan limestone aquifer of oum er rabia as an example of statistical and cartographical approaches in water resources management statistical analyses based on frequency distribution and pca methods revealed the homogeneity of waters with the existence of abnormal points and have helped to assess correlations between the studied variables the mapping approach illustrated that waters are influenced by the lithology of the surrounding rocks and are of ca mg hco3 ca mg cl so4 and mixed types according to the piper classification the quality of water is of high to medium north of the basin but it is of medium to bad ne and south due to excessive contents of chloride sulfate and nitrate according to the us salinity laboratory classification water used for irrigation in the eastern and the southern parts of the basin should take into consideration the drainage conditions the nature of plants and the addition of gypsum doses

seismic evidence for a slab tear at the puerto rico trench 1 the fore arc region of the northeast caribbean plate north of puerto rico and the virgin islands has been the site of numerous seismic swarms since at least 1976 a 6 month deployment of five ocean bottom seismographs recorded two such tightly clustered swarms along with additional events joint analyses of the ocean bottom seismographs and land based seismic data reveal that the swarms are located at depths of 50 150 km focal mechanism solutions found by jointly fitting p wave first motion polarities and s p amplitude ratios indicate that the broadly distributed events outside the swarm generally have strike and dip slip mechanisms at depths of 50 100 km while events at depths of 100 150 km have oblique mechanisms a stress inversion reveals two distinct stress regimes the slab segment east of 65 w longitude is dominated by trench normal tensile stresses at shallower depths 50 100 km and by trench parallel tensile stresses at deeper depths 100 150 km whereas the slab segment west of 65 w longitude has tensile stresses that are consistently trench normal throughout the depth range at which events were observed 50 100 km the simple stress pattern in the western segment implies relatively straightforward subduction of an unimpeded slab while the stress pattern observed in the eastern segment shallow trench normal tension and deeper trench normal compression is consistent with flexure of the slab due to rollback these results support the hypothesis that the subducting north american plate is tearing at or near these swarms the 35 year record of seismic swarms at this location and the recent increase in seismicity suggest that the tear is still propagating

sodium calcium ion exchange in the weathering of shales implications for global weathering budgets unpolluted rivers and streams that drain marine shales show an excess of sodium compared to chloride and a deficiency of calcium and magnesium compared to sulfate and alkalinity this is due in part to cation exchange of sodium for divalent cations on clay minerals consideration of the global weathering budget suggests that up to 34 of the sodium in the total dissolved stream load may be due to cation exchange rather than sodium production via silicate dissolution weathering reactions these results suggest that the weathering budgets for sodium and calcium are in need of revision because of the inclusion of cation exchange processes in the weathering cycle this implies that silicate dissolution is less important in determining the composition of global river water than was previously thought

faulting within the eastern baikal rift as characterized by earthquake studies earthquake relocations focal mechanism determinations waveform modeling and stress analyses using focal mechanism information are used to examine the faulting processes within the western baikal rift 95 to 108 5 results of the study show that high angle dip 70 faulting is most likely to occur in the more youthful parts of the rift and is most likely to be associated with m 4 5 events like the eastern rift nearly all earthquakes occurred on faults dipping 30 suggesting that in no part of the rift is significant deformation occurring on low angle structures focal mechanism information does not indicate there is a sharp boundary to the western rift as observed in the eastern rift less normal faulting rakes 60 to 120 occurs in the western rift than the eastern rift waveform modeling of the two largest earthquakes 1950 mondy and 1959 srednebaikal in the western rift gives focal depths of 10 to 15 km the 1959 event appears to have occurred along the eastern boundary fault on lake baikal just to the north of proval bay a feature created a m 7 1 earthquake in 1862 the 1950 event may have occurred along the southern boundary fault of the tunka depression stress orientation information indicates a near horizontal nw se to wnw ese striking 3 in the eastern part of the western rift

reservoir characterization using oil production induced microseismicity clinton county kentucky abstract microseismic monitoring tests were conducted from 1993 to 1995 in the seventy six oil field clinton county kentucky oil is produced from low porosity fractured carbonate rocks at 3 no injection operations were conducted gross changes in production rate correlate with event rate event rate lags changes in production rate by 2 to 3 weeks hypocenters and first motion data have revealed previously undetected low angle thrust faults above and below the currently drained depth intervals production history well logs and drill tests indicate that the seismically active faults or fractures are previously drained intervals that have subsequently recovered to hydrostatic pressure via brine invasion storage capacity computed for one of these drained fractures implies that total oil production represents about 20 of total pore volume correlation of older production intervals and well log porosity anomalies with the seismically active faults indicate that the oil reservoir in the study area is primarily a set of compartmentalized low angle thrust faults although low angle fracture sets have not previously been considered in the exploration and development of the area the mapped thrust faults are consistent with other investigators interpretations of oil associated with secondary fracture sets occurring along deeper seated wrench fault structures stress determined from composite focal mechanisms indicates a near surface

shallow subduction tectonics and fault interaction the weber new zealand earthquake sequence of 1990 1992 a series of four large earthquakes with epicenters very close to one another occurred in 1990 1992 in the weber region of the southeast coast of the north island new zealand the region is one of oblique plate convergence and subduction the plate interface being at about 20 km depth the first event february 19 1990 ml 6 1 mw 6 2 occurred within the upper part of the subducting pacific plate on a steeply northwest dipping normal fault as defined by relocated aftershocks the mechanism of this event reflects downdip tension within the subducting plate due to slab pull forces as is common in new zealand the second event may 13 1990 ml 6 2 mw 6 4 occurred on an imbricate fault in the overlying australian plate dipping shallowly northwest with components of both thrusting and dextral strike slip motion the slip vector is similar to the direction of plate convergence showing no arc normal rotation as observed for subduction thrust events in other areas of oblique convergence it is unlikely that the spatial and temporal closeness of these events is coincidence a similar pair occurred to the south in 1942 but the coupling mechanism is not clear perhaps being related to aseismic slip downdip on the subduction interface two subsequent events both of ml 5 5 occurred on august 15 1990 and march 2 1992 and extended the aftershock zone of the deeper first main shock to the northeast matching the extent of the shallower second main shock mechanisms of aftershocks of the two larger events are quite variable but as a whole are similar to the relevant mainshock the time history of the aftershocks of the first deeper event shows a period of quiescence beginning 35 days before the second shallow event the mean magnitude of those events that did occur was high this observation cannot be explained by station biases weather or changes in analysis methods and may be due to stress changes induced by precursory aseismic slip which would discourage aftershock occurrence

deposition of atmospheric heavy metals to the greenland ice sheet from the 1783 1784 volcanic eruption of laki iceland abstract in order to assess better the influence of major volcanic events on the large scale atmospheric cycles of heavy metals greenland ice dated from the time of the fallouts from the great 1783 1784 eruption of laki volcano in iceland has been analysed for pb cd cu zn and sulphate the concentrations of the four heavy metals investigated are found to be greatly enhanced in the ice layers which correspond to the fallouts from the eruption confirming that such events do modify the atmospheric cycles of heavy metals cumulative fallout of heavy metals to the whole greenland ice cap from the 1783 1784 laki eruption ranges from 1 t for pb and cd to 40 t for zn for cd cu and zn it represents a few percent of the cumulative anthropogenic fallout to the ice cap from the industrial revolution to the present

determination of stresses from heterogeneous focal mechanism data an adaptation of the multiple inverse method abstract a new method is proposed to separate stresses from earthquake focal mechanism data double couple component of focal mechanisms from spatially or temporarily varying state of stress the underlying multiple inverse method was originally devised for geological fault slip data but we have adapted its resampling scheme to focal mechanism data to cope with the nodal planes ambiguity problem the stresses compatible with a dataset are recognized as the clusters of reduced stress tensors the clusters are identified with the k means clustering the uncertainty of the stresses are evaluated from the spread of the clusters the technique is shown to successfully determine valid stresses from simulated data we have also applied the technique to natural data from southwestern japan

slip partitioning and deformation cycles close to major faults in southern california evidence from small scale faults geometry and kinematics of small scale faults adjacent to large seismically active faults have been analyzed for a large region of southern california the sampled population of small scale faults is scattered in orientation and slip but possesses distinct trends two important characteristics are first the paucity of small scale faults that mimic orientations and mechanisms of the adjacent master faults and second the large variation in slip mechanisms of fault planes oriented e w and n s in order to test the similarity of the sampled fault population to present day deformations data on geometry and slip of the small scale faults have been used for stress inversions these results are compared with those derived from focal mechanisms of low magnitude earthquakes in the same region stress orientations derived from small scale faults are spatially heterogeneous but horizontal axes of stress maintain n s and e w trends over the entire region the similarities between stress inversions from small faults and seismicity support the conclusion that most of the sampled faults are recent and formed during cyclical events of fracturing in a relatively strong crust adjacent to weak master faults

acid rain and ozone depletion from pulsed siberian traps magmatism the siberian traps flood basalts have been invoked as a trigger for the catastrophic end permian mass extinction widespread aberrant plant remains across the permian triassic boundary provide evidence that atmospheric stress contributed to the collapse in terrestrial diversity we used detailed estimates of magmatic degassing from the siberian traps to complete the first three dimensional global climate modeling of atmospheric chemistry during eruption of a large igneous province our results show that both strongly acidic rain and global ozone collapse are possible transient consequences of episodic pyroclastic volcanism and heating of volatile rich siberian country rocks we suggest that in conjunction with abrupt warming from greenhouse gas emissions these repeated rapidly applied atmospheric stresses directly linked siberian magmatism to end permian ecological failure on land our comprehensive modeling supplies the first picture of the global distribution and severity of acid rain and ozone depletion providing testable predictions for the geography of end permian environmental proxies