lithofacies analysis of colluvial sediments an aid in interpreting the recent history of quaternary normal faults in the basin and range province western united states inferring the frequency and magnitude of past earthquakes from the stratigraphy in exposures of normal faulted sediments is difficult because colluvial lithofacies assemblages adjacent to faults are complex similarities in facies assemblages adjacent to young fault scarps in arid to semiarid areas such as the basin and range province allow lithofacies to be grouped into two genetic architectural elements debris and wash elements upper and lower facies associations can commonly be recognized within each element a lithofacies code scheme similar to those used in the analysis of fluvial and glacial lithofacies sequences provides a concise way of illustrating lithofacies relations in fault exposures the source lithology of colluvial lithofacies is shown in the code and soil horizon symbols can be included the architecture of lithofacies assemblages near fault scarps in semiarid areas is explained by a model of colluvial sedimentation in response to a single surface faulting event analysis of lithofacies assemblages exposed in three trenches across normal faults in the eastern basin and range shows how the model can be used to interpret fault histories similar facies analysis methods may be useful in interpreting colluvial sequences formed by non tectonic processes

geochemistry origin and recharge mechanisms of groundwaters from the garoua sandstone aquifer northen cameroon this paper presents results of the geochemical and isotopic studies on groundwater samples from the garoua sandstone basin in northern cameroon chemical and environmental isotope data are presented and discussed in terms of the origin of dissolved species and of groundwater all of the investigated groundwaters are categorized into two chemical types low mineralized and acidic waters of ca na hco3 type and relatively high mineralized waters of na hco3 type with relatively high ph between 7 40 and 8 22 interpretation of chemical data based upon both thermodynamic calculations and stability diagrams suggests that the chemical evolution of groundwater is primarily controlled by water rock interactions involving 1 acidic weathering of aluminosilicates 2 dissolution of secondary carbonate minerals and 3 cation exchange of na for ca2 however the original composition of groundwater may have been modified by further secondary processes such as mixing of chemically different water masses and anthropogenic no 3 pollution tritium contents in the considered groundwaters are very heterogeneous suggesting differences in the water turnover time or in the recharge conditions or both on the basis of the geographical distribution of 3h contents a hydrogeological relation between river and the groundwater systems has been proposed for the study site interpretation of both 18o and 2h as well as 3h suggests that the recharge of the investigated groundwaters may result from three major mechanisms 1 direct infiltration of local precipitation 2 lateral inflow of river waters 3 probably upward leakage of old groundwaters

geochemical and statistical evaluation of groundwater in imphal and thoubal district of manipur india abstract in order to identify the hydrogeochemical process controlling the quality of groundwater an extensive study was carried out in imphal and thoubal district of manipur india the objectives of the studies were to delineate the spatial and temporal variability in groundwater quality and understand its suitability for human uses in the study area groundwater samples from 45 location have been collected during the pre monsoon monsoon and post monsoon seasons and analyzed for the major ions such as ca2 mg2 na k hco 3 cl so 4 2 no 3 po 4 3 f fe and silica the water quality of both districts was good for domestic and agricultural uses except for few samples these saline samples were localized and were due to the inherent lithology of the study area three major hydrochemical facies ca hco3 type mixed ca na hco3 and ca mg cl types in imphal district and ca hco3 mixed ca mg cl and ca cl type in thoubal district were identified the mineral stability diagrams indicated that the groundwater is in equilibrium with kaolinite and ca montmorillonite whereas gibbs plot showed that the chemical composition of ground water in both districts is controlled by the natural weathering processes irrespective of seasons among the chemical weathering processes silicate weathering was dominant the results were supported by wilcox plot and ussl diagrams the study reflected the overall suitability of groundwater for anthropogenic use

a palaeoseismological and geoarchaeological investigation of the eliki fault gulf of corinth greece abstract palaeoseismological and morphotectonic analyses enable us to define a 400 m wide actively deformed zone associated with the active eliki normal fault central greece bounded on the south by a second order fault and on the north by a composite and prominent fault scarp this scarp is further analysed by trenching based on colluvium stratigraphy displacement of distinct horizons and deposition of sedimentary layers three faulting events have been identified along four fault strands affecting unconsolidated sediments in the trench the two younger events with throws of 0 93 and 1 37 m respectively the third event with a throw of 0 44 m and the penultimate 373 bc event suggest a variable seismic history the entire alluvial plain of the kerynitis and vouraikos rivers which cross the eliki fault has subsided at a rate of 1 4 mm year resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments in places extension in the broader area is accommodated by the seismically active eliki and egion faults structural and palaeoseismological analysis of those two faults indicates that they accommodate 1 5 mm year or about 10 of the geodetically estimated extension of up to 13 mm year

migration of activity within normal fault systems examples from the quaternary of mainland greece abstract we examine five areas of mainland greece where active extension occurs on sub parallel systems of normal faults and where geomorphological and stratigraphic evidence indicates that the faulting has migrated basinwards into the original hanging walls in several cases within the late quaternary by comparing fault slip rates estimated from geomorphological data with current extension rates known from geodetic measurements it appears that the newest faults can account for effectively all the present day motions fault migration of this sort is easy to recognize in young systems close to sea level because vertical movements of footwalls and hanging walls are obvious and reveal which faults are currently most active but is less easy to confirm away from reliable reference levels or in older terrains with poorer time resolution it is probably more common than is appreciated and has a profound effect on syn rift sedimentation and erosion patterns fault migration is probably an inevitable consequence of the interplay between stresses generated by the fault related topography and the ultimate strength of major faults it is likely to be further encouraged in places where lower crustal flow or rotations about a vertical axis are important however it is not clear why migration should preferentially occur into the hanging walls as observed in central greece

organic geochemistry of marine sediments in antarctic region marine lipids in mcmurdo sound abstract the compositions of resolvable lipid components from four sediment cores 0 90 cm of mcmurdo sound ross sea have been examined the various lipid components occur in the following order of abundance sterols fatty acids n alcohols n alkanes pah the data indicate that the organic matter is mainly derived from recycled kerogen mixed with modern marine input the distribution of lipids and lignin analyses indicate that there is little recognizable higher plant debris in the sediments the sediments contain unaltered biogenic triterpenoids and there is no evidence for natural and or anthropogenic petroleum influx in the region aeolian transport of organic carbon from the continents appears to be negligible the dominance of labile alkenes c 25 compounds and hopenes and the presence of unsaturated fatty acids down to a depth of 90 cm reflect a very early diagenetic stage the persistent cold climate has probably helped in the better preservation of these labile lipids in the water column and in the young sediments diploptene 17 h 21 h hop 22 29 ene appeats to originate from autochthonous marine productivity in mcmurdo sound

submarine and coastal sediment failure triggered by the 1995 ms 6 1 r aegion earthquake gulf of corinth greece on june 15th 1995 a locally destructive earthquake of magnitude ms 6 1 on the richter scale occurred offshore 7 5 km nne of the town of aegion in the western gulf of corinth greece an offshore survey using 3 5 khz subbottom profiling system and a remote operated vehicle rov has shown that the earthquake caused small sized subaerial to submarine sediment failure in at least four sites in three fan delta deposits the rododafni the eliki and the tolofonas the fan deltas were located within a radius of about 9 km from the epicentre the areal size of the four sediment failure sites ranged from 2 104 m2 to 6 105 m2 whilst the volume of the failed masses ranged from 4 103 to 3 106 m3 the sediment deformation types identified at the failure sites consist of ground cracking rotational slides elongated slides sediment gravity flows and extrusion of mixtures of water and sand sand boils the sediment failure in the four sites affected the upper 5 6 m of well layered holocene topset and foreset fan delta deposits the failure occurred on slopes ranging from 0 2 to 23 and the slip planes were all bedding planes which have a gradient from 0 2 to 21 the dominant instability mechanism that caused the sediment failure in the rododafni and eliki fan deltas is considered to be liquefaction of a shallow sub surface horizon the liquefaction was caused by elevated pore pressure enhanced perhaps by the presence of gas resulting from the cyclic loading induced by the earthquake the liquefied layer is assumed to have temporarily provided a failure surface for sliding to take place on and caused movement of sand that was ejected onto the surface in the tolofonas fan delta the causative mechanism in the case of the multi block rotational slide is considered to be deformation of the underlying sediments caused by remoulding and or liquefaction while in the case of the elongated slide it is considered to be the result of a combination of shear stress increase and or strength degradation of the unconsolidated sediment both of these conditions could have been generated during the cyclic loading resulting from the aegion earthquake the study of historical documents reveals that sediment failure like those described above have also occurred at least four times during the past 2500 years in the same locations therefore it is suggested that they could be repeated in the future by any earthquake event with a magnitude greater than 6 r depending upon the proximity of the site to the earthquake epicentre

identification and evolution of hydrogeochemical processes in the groundwater environment in an area of the palar and cheyyar river basins southern india the palar and cheyyar river basins in tamil nadu state of southern india are characterised by different geological formations and groundwater is the major source for domestic agricultural and other water related activities hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes and their relation to groundwater quality groundwater samples were collected once a month from 43 groundwater wells in this area from january 1998 to july 1999 sampling procedures and chemical analysis were carried out as per the standard methods chemical data are used for mathematical calculations and graphical plots to understand the chemical process and its relation to the groundwater quality the chemical composition of groundwater in the central part of the study area mainly depends on the recharge from lakes and the river which is explained by a mixing mechanism in addition weathering of silicate minerals controls the concentration of major ions such as sodium calcium magnesium and potassium in the groundwater of this area further the activity ratios indicate that the groundwater is in equilibrium with kaolinite smectite and montmorrillonite the reverse ion exchange process controls the concentration of calcium magnesium and sodium in hard rock formations and dissolution of carbonate minerals and accessory minerals is the source of ca and mg in addition to cation exchange in the sedimentary formations in general the chemical composition of the groundwater in this area is influenced by rock water interaction dissolution and deposition of carbonate and silicate minerals ion exchange and surface water interactions

paleoseismicity of the 1981 corinth earthquake fault seismic contribution to extensional strain in central greece and implications for seismic hazard we present paleoseismological trenching results for the active skinos fault which ruptured the surface on the alkyonides gulf basin margin in the 1981 gulf of corinth earthquake sequence three trenches expose evidence of up to six previous events which are comparable to the 1981 deformation in terms of size and geometry vertical displacement produced by the 1981 earthquake ranged from 0 45 to 1 3 m at the bambakies fan trench sites decreasing towards the eastern fault tip east of the trenches trench 1 reveals two previous events with vertical displacements between 0 5 and 1 2 m since 390 a d trench 2 reveals five or six previous events but these are not dated trench 3 reveals four previous events since 670 a d vertical displacements associated with interpreted paleoearthquakes at the trench sites are 1 2 m the recurrence interval on the skinos fault is estimated to average 330 years however significant variation in recurrence interval is allowed by the available radiometric dates average vertical displacement rates derived from the trenches are in the range 0 7 2 5 mm yr a similar long term average vertical displacement rate of 1 2 2 3 mm yr is estimated for the lifespan of the basin bounding fault this equates to a horizontal seismic strain contribution of 2 5 mm yr from the skinos fault this local seismic strain rate overlaps within error with geodetically determined velocities across the alkyonides gulf assumed to represent uniform deep crustal strain thus seismic deformation on the basin bounding fault system may take up the major part of extension across the basin and aseismic strain is not necessitated by the data if correct this would imply that geodetically determined strain rates may be used as a proxy for potential seismic moment release in seismic hazard analyses for this region

late holocene evolution of the east eliki fault gulf of corinth central greece abstract trench stratigraphy and morphotectonic analysis was used to examine the recent evolution of the helike eliki plain and eliki fault the entire alluvial plain of the kerynites and vouraikos rivers which cross the eliki fault has subsided at rate of 1 4 mm yr resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments along the eastern segment of the eliki fault five trenches have been excavated and their 5000 yr old fluvial and colluvial deposits have been studied in association with the fault strand imprinted on them the kerynites river crosses at high angle the eliki fault and appears to be sensitive in tectonic movements related with the eliki fault sedimentation in the alluvial plain and the fluvial geomorphology of the kerynites river is important for understanding the fault evolution and the burial of the ancient 4th century bc helike city the kerynites river course highlights breaching deformation is the more likely to connect east and west eliki fault segments and that postseismic deformation is a significant mechanism for stress accommodation for part of the west end of the gulf of corinth

geochemical process regulating groundwater quality in a coastal region with complex contamination sources barka sultanate of oman an investigation was carried out to evaluate the geochemical processes regulating groundwater quality in a coastal region barka sultanate of oman the rapid urban developments in barka cause depletion of groundwater quantity and deterioration of quality through excessive consumption and influx of pollutants from natural and anthropogenic activities in this study 111 groundwater samples were collected from 79 wells and analysed for ph ec do temperature major ions silica and nutrients in barka water chemistry shows large variation in major ion concentrations and in electrical conductivity and implies the influence of distinguished contamination sources and hydrogeochemical processes the groundwater chemistry in barka is principally regulated by saline sources reverse ion exchange anthropogenic pollutants and mineral dissolution precipitation reactions due to ubiquitous pollutants and processes groundwater samples were classified into two groups based on electrical conductivity in group1 water chemistry is greatly influenced by mineral dissolution precipitation process and lateral recharge from upstream region jabal al akdar and nakhal mountains in group 2 the water chemistry is affected by saline water intrusion sea spray reverse ion exchange and anthropogenic pollutants besides high nitrate concentrations especially in group 2 samples firm evidence for impact of anthropogenic activities on groundwater quality and nitrate can be originated by the effluents recharge from surface contamination sources ionic ratios such as so4 cl alkalinity cl and total cation cl indicate that effluents recharged from septic tank waste dumping sites and irrigation return flow induce dissolution of carbonate minerals and enhances solute load in groundwater the chemical constituents originating from saline water sources reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta the difference between the actual concentration of each constituent and its theoretical concentration for a freshwater seawater mix calculated from the chloride concentration of the sample and proved that this approach is a promising tool to identify and differentiate the geochemical processes in coastal region hence both regular geochemical methods and ionic delta ensured that groundwater quality in barka is impaired by natural and human activities

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

scales of structural heterogeneity within neotectonic normal fault zones in the aegean region abstract structural heterogeneities within neotectonic normal fault zones in the aegean region are important controls on the geomorphic expression of their uplifted footwall blocks contrasting fault rocks and slip plane phenomena corrugations comb fractures slip parallel fractures and pluck holes are responsible for mesoscopic inhomogeneities within fault scarps along strike disruptions in the continuity of fault scarps step over zones step up zones step down zones footwall cross faults and hangingwall cross faults are products of perturbations in slip plane geometry or intersections with transverse faults large scale variations in range front morphology reflect contrasting patterns of deformation within fault zones some major fault zones and many minor fault zones are characterized by a migration of the active slip plane towards the hangingwall resulting in a distributed network of high angle faults and a range front which is stepped in profile the presence of a localized mass of uneroded bedrock hangingwall salients protruding from the hangingwall of some major fault zones results in intense deformation along a principal slip plane and a range front which is ramp like in profile as a consequence of structural heterogeneities within neotectonic normal fault zones fault scarps and range fronts in the aegean region are subject to a temporally and spatially variable pattern of degradation

assessment of geochemical processes in the unconfined and confined aquifers in the eastern ganges basin a geochemical approach groundwater quality is gaining more importance in groundwater management due to rapid growth in population agriculture and industrial sectors worldwide the goal of the present study is to evaluate the groundwater chemistry and to identify the geochemical processes governing the water chemistry in the shallow unconfined and deeper confined aquifers in the eastern ganges basin using geochemical methods groundwater samples were analysed for major ions and metals fe mn zn cu pb and as shallow wells are found to have high ph ec tds ca mg cl and so4 and low hco3 cl ratio compared to the deep wells however the average concentration of na hco3 no3 po4 f and mn is not significantly varied with depth which indicates that the variation in the water chemistry between unconfined and confined aquifers is not only due to the natural processes but also indicates that surface contamination sources could have affected the water chemistry in the unconfined aquifer in the unconfined aquifer processes like wastewater infiltration denitrification reverse ion exchange and mineral weathering govern the water chemistry the water chemistry in the confined aquifer is regulated by weathering of silicate and carbonate minerals and regional flow

hydrochemical and isotopic characteristics of groundwater in the ndop plain northwest cameroon resilience to seasonal climatic changes shallow groundwater 30 mbgl is an essential source of drinking water to rural communities in the ndop plain northwest cameroon as a contribution to water management the effect of seasonal variation on the groundwater chemistry hydrochemical controls drinking quality and recharge were investigated during the peaks of the dry january and rainy september seasons field measurements of physical parameters were preceded by sampling 58 groundwater samples during both seasons for major ions and stable isotope analyses the groundwater which was barely acidic mean ph of 6 and less mineralised tds ca2 mg2 k and na mg2 ca2 k in the dry and rainy seasons respectively but that of anions text hco 3 text no 3 cl text so 4 2 f was similar in both seasons this suggests a negligible effect of seasonal variations on groundwater chemistry the groundwater which was camghco3 and nahco3 is chemically evolved rainfall camgso4cl in the area silicate mineral dissolution and cation exchange were the main controls on groundwater chemistry while there was little anthropogenic influence the major ions and tds concentrations classified the water as suitable for human consumption as per who guidelines the narrow cluster of 18o and d of same groundwater from both seasons between the 18o and d values of may june precipitation along the ndop meteoric water line indicates meteoric origin rapid recharge after precipitation and timing of recharge between may and june rainfall diffuse groundwater recharge mainly occurs at low altitudes 1 400 m asl within the plain besides major ions and tds the similar 18o and d of groundwater from both seasons indicate a consistent groundwater recharge and flow pattern throughout the year and resilience to present day short term seasonal climatic variations however controlled groundwater abstraction is recommended given the increasing demand

chemistry and late quaternary evolution of ground and surface waters in the area of yabulai mountains western inner mongolia china abstract in the extensive area of western inner mongolia china the water demand of local residents often depends mainly on shallow aquifers although scientific investigations of the quality and formation of the groundwater are still lacking in this study the chemistry and isotopic composition of groundwater and lake water samples collected at 22 sites in the area of yabulai mountains fig 1 in western inner mongolia were analysed chemical water analysis included the determination of na k ca2 mg2 li nh4 al3 co2 co32 hco3 cl so42 no3 f po43 hbo2 and sio2 and 18o and tritium isotopes solute concentrations in groundwater show significant differences within the study area while the water of the three lakes is dominated by sodium and chloride this study reveals the importance of spatial variation of groundwater chemistry in an arid environment that has a relatively homogeneous lithological basement the heterogeneity of groundwater chemistry suggests that the shallow groundwater in western inner mongolia is mainly recharged by infiltration of local rainfall the relatively high tritium content indicates that the water in the shallow aquifer of the study area is generally not older than 100 years former shorelines in the lake basin of shugui fig 1 suggest the presence of a much larger lake in the past under a wetter climate than present hyper arid conditions presumably because of increased east asian monsoon intensity during the middle holocene in the vicinity of commune administrations that have higher population density the tds of ground water is also higher probably owing to water pollution

drainage evolution in a rifted basin corinth graben greece abstract intrabasinal basement highs and transfer faults distance from source and the underlying geology influence the drainage pattern and the evolution of the 41 river basins in the northern peloponnesus these rivers were classified as antecedent 10 multistory 17 re established 5 and juvenile 9 drainage types antecedent drainage is when a river has maintained its original direction of flow across later tectonic topography multistory drainage consists of a re established drainage and of a reverse drainage reverse drainage when flow direction along part of a river is reversed consists of two opposing drainage components a misfit and a reverse element the area between these two elements termed wind gap is a dry valley re established drainage is when a reverse element returns to its original flow direction juvenile drainage consists of small incising and headward eroding streams the sediments that the rivers flow across soft uncohesive marls or coarse grained deposits and pre neogene basement with limestones river power strong close to the source or weak far from the source presence or absence of transfer faults and tilted blocks due to the activity of synthetic and antithetic faults all influence whether an antecedent drainage will remain unchanged or will be changed to a reverse drainage when transfer faults cross cut the area of a wind gap and the underlying sediments were soft uncohesive marls reverse drainage changed to a re established drainage in other cases where transfer faults were absent and underlying deposits were coarse grained sediments or limestones in the area of the wind gap then reverse drainage remained unchanged

geodetic determination of tectonic deformation in central greece from 1900 to 1988 the global positioning system has been used to measure the relative displacements of fifteen monuments in a hundred year old triangulation network spanning part of the aegean extensional basin these displacements reflect the tectonic deformation of the region over the past century showing more than one metre of north south extension across the network the crust in this region appears to contain a few slowly deforming blocks separated by more rapidly deforming zones

identifying source and evaluation of hydrogeochemical processes in the hard rock aquifer system geostatistical analysis and geochemical modeling techniques in order to quantify spatio temporal changes in the hydrogeochemistry of swarnamukhi river basin andhra pradesh india a total of 239 groundwater samples have been collected for pre and post monsoon seasons of 2014 and 2015 the geology of the study area is comprised of granite granitic gneisses shales quartzites laterites and recent alluvium along the river course based on the study of geochemical processes of different seasons it is found that the occurrence of na and hco3 in 2014 shifted toward ca and hco3 in 2015 due to cation exchange process fe shows the higher concentration value than safe limit due to dissolution of ferruginous minerals and domestic sewage discharges bivariate plots of various ions and ratios depict the predominance of silicate weathering over carbonate and evaporite dissolution apart from anthropogenic activities in the enrichment of groundwater constituents high nitrate concentration was observed in the urbanized regions of the basin followed by intense agricultural areas geochemical modeling was carried out using mineral saturation index and thermodynamic stability plots to deduce major weathered products most of the groundwater samples in the study area are saturated with carbonate minerals but are undersaturated with silicate minerals thermodynamic stability plots suggest the formation of kaolinite secondary mineral and presence of aluminosilicate minerals fuzzy calculation is applied to determine the water quality index which categorizes a majority of the samples as excellent to good category for human use factor analysis points toward the mixed source identification of ionic constituents saline water mixing index model calculation suggests the effect of salinization in coastal areas due to heavy withdrawal of the fresh groundwater resources for various uses whereas in the mainland it is due to agricultural runoff and domestic waste water

the tectonic setting and earthquake ground hazards of the 1993 pyrgos earthquake peloponnese greece the pyrgos earthquake in western greece 26 march 1993 m l 5 2 was caused by oblique normal slip on a north dipping and wnw trending fault and produced significant damage in the town of pyrgos several lines of evidence from the epicentral area suggest that faults within two active graben in the pyrgos basin the grape and alfios grabens were reactivated during this earthquake and subsequent aftershocks evaluation of morphotectonic data the fault slip rate between 0 05 and 0 35 mm a 1 and seismic activity associated with the 1993 earthquake suggest that the alfios graben is the most active structure in the basin this graben which is 25 km long and crosses the pyrgos basin is segmented along its strike by transfer zones analysis of the seismic activity in this graben shows that transfer zones are the focus for the concentration of seismic activity and thus the concept of transfer zones is important for understanding the pyrgos earthquake the 1993 earthquake caused landslides at 47 locations and liquefaction phenomena at 7 localities within an area of 145 km 2 the lower threshold level to induce landslides was m l 4 0 and to induce liquefaction was 5 0 the majority of landslides occurred along fault scarps and either caused the slope to retreat and or acted to protect the slope gradient

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

the origin of high nitrate ground waters in the australian arid zone abstract nitrate concentrations beyond the drinking water limit of 10 mg1 1 no3 n are common in australian arid zone ground waters and are often associated with otherwise potable waters in some aquifers nitrate n concentrations of up to 80 mg1 1 have been found and this is a severe constraint on water supply development for small settlements water bore data indicate a correlation of high nitrate ground waters with shallow unconfined aquifers aguifer hydrochemistry indicats that these ground waters were emplaced by episodic holocene recharge events in an otherwise arid climate regime nitrate has been flushed through the unsaturated zone which apparently lacks denitrification activity the nitrate originates by near surface biological fixation and contributing organisms include cyanobacteria in soil crusts and bacteria in termite mounds with the highest soil nitrate concentrations found in the outer skin of termite mounds bacteria associated with the termites appear to fix nitrogen which eventually appears in an inorganic form principally as ammonia nitrate is produced by bacterial oxidation of the ammonia and is leached to the outside of the termite mound by capillary action diffuse recharge from extreme rainfall events then flushes this nitrate to the water table

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

macroscopic seismic anomalies and submarine pockmarks in the corinth patras rift greece prior to the aigion earthquake m 6 2 of 15 june 1995 in the western gulf of corinth people in the area observed anomalous phenomena including bubbling of the sea extraordinary behavior of animals earthquake lights ground deformation and the sound of wind immediately before the shock some precursory phenomena of this kind might be understood as symptoms of gas venting before an earthquake sonar observations made in 1988 showed a chain of submarine pockmarks tracing the aigion fault and evidently produced by the expulsion of fluids under pressure t hasiotis et al mar geol 130 333 344 reported that hot gas erupted from a field of giant submarine pockmarks in the neighboring bay of patras several hours prior to an earthquake in 1993 automated monitoring of bottom water temperature in submarine pockmark fields may detect outgassing events prior to earthquakes in this region

fractal characteristics of active normal faults an example of the eastern gulf of corinth greece abstract we present a model proposing the evolution of segmented normal faults in a currently extended area allowing an explanation of strong earthquakes hosted by short faults active normal faults accommodating the current extension in the gulf of corinth result from the linkage of smaller component faults well exposed fault zones in the sofiko range are arranged as pairs of graben bounding faults and thus our structural analysis has implications for the evolution of active normal faults as well as graben evolution a basal strip of fresh bedrock at the base of fault scarps suggests continuous seismic or aseismic creep thus the structural analysis of component faults that show a power law length distribution describes an evolved fault zone of particular interest is that faulting in this region is self similar between limits distribution is characterized by a fractal dimension of d 1 and the limits in our study are between 10 m mapping resolution and double the maximum displacement of each fault zone component segments of any compartmentalized fault show a length to maximum displacement ratio of two basin architecture and structural analysis suggest that the nucleation points of faults are detectable over the entire evolution of the fault zone all analyzed faults evolved by an independent nucleation model morphotectonic and kinematic data as well as fractal dimension of trace length population plots all suggest that fault zones defining north and south dipping conjugates are active at least over the late stages of basin evolution although this study was focused on a relatively small area this pattern of fault growth appears to be applicable to the entire fault population in the gulf of corinth and is thus an important model for normal faults

geometry and kinematics of active faults and their seismotectonic significance in the western corinth patras rift greece abstract the western part of the corinth patras rift is formed in an area which is being uplifted rifted domains have subsided relative to the adjacent areas in nw peloponnesus and sterea hellas but subsidence rates rarely exceed uplift rates extension is mainly accomplished by wnw trending active faults with lengths up to 25 km most of these faults show an along strike segmentation and often terminate against transfer faults displacement analysis along 170 mesoscopic faults and 36 mappable faults has been carried out to assess slip rates and to estimate the magnitudes and recurrence time intervals of earthquakes occurring along them earthquake magnitude ranges between 5 and 6 7 only eight faults appear to be capable of producing earthquake magnitudes larger than 6 recurrence times of these large earthquakes vary between 80 and 1690 years upper crustal deformation in the western corinth graben can be described by six large asymmetric grabens which are inferred to bottom out to a n dipping curved ramp the asymmetric shape of most wnw trending rifts in the hellenic peninsula including the corinth patras rift promotes the simple shear model of extension against the pure shear model in the upper crustal layer

the evolution of the gulf of corinth greece an aftershock study of the 1981 earthquakes summary a preliminary study of the aftershocks of three earthquakes that occurred near to corinth greece in 1981 is combined with observations of the morphology and faulting to understand the evolution of the eastern gulf of corinth the well located aftershocks form a zone 60km long and 20km wide they do not lie on the main fault planes and are mostly located between the north dipping faulting on which the first two earthquakes occurred and the south dipping faulting associated with the third event a cluster of aftershocks also lies in the footwall of the eastern end of the south dipping fault of the third event morphologically it is observed that in the evolution of the eastern gulf of corinth antithetic faulting apparently predates the appearance of the main faulting at the surface this evolution can be explained by motion on a deep seated shallow angle aseismic normal fault a model based on such a fault also accounts for the aftershock distribution of the 1981 earthquakes

salinization of groundwater in arid and semi arid zones an example from tajarak western iran study of the groundwater samples from tajarak area western iran was carried out in order to assess their chemical compositions and suitability for agricultural purposes all of the groundwaters are grouped into two categories relatively low mineralized of ca hco3 and na hco3 types and high mineralized waters of na so4 and na cl types the chemical evolution of groundwater is primarily controlled by water rock interactions mainly weathering of aluminosilicates dissolution of carbonate minerals and cation exchange reactions calculated values of pco2 for the groundwater samples range from 2 34 10 4 to 1 07 10 1 with a mean value of 1 41 10 2 atm which is above the pco2 of the earth s atmosphere 10 3 5 the groundwater is oversaturated with respect to calcite aragonite and dolomite and undersaturated with respect to gypsum anhydrite and halite according to the ec and sar the most dominant classes c3 s1 c4 s1 and c4 s2 were found with respect to adjusted sar adj sar the sodium na content in 90 of water samples in group a is regarded as low and can be used for irrigation in almost all soils with little danger of the development of harmful levels of exchangeable na while in 40 and 37 of water samples in group b the intensity of problem is moderate and high respectively such water when used for irrigation will lead to cation exchange and na is adsorbed on clay minerals while calcium ca2 and magnesium mg2 are released to the liquid phase the salinity hazard is regarded as medium to high and special management for salinity control is required thus the water quality for irrigation is low providing the necessary drainage to avoid the build up of toxic salt concentrations