geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

sulphuric acid speleogenesis and landscape evolution montecchio cave albegna river valley southern tuscany italy abstract montecchio cave grosseto province tuscany italy opens at 320 m asl in a small outcrop of jurassic limestone calcare massiccio fm close to the albegna river this area is characterised by the presence of several thermal springs and the outcropping of travertine deposits at different altitudes the montecchio cave with passage length development of over 1700 m is characterised by the presence of several sub horizontal passages and many medium and small scale morphologies indicative of sulphuric acid speleogenesis sas the thermal aquifer is intercepted at a depth of about 100 m below the entrance the water temperature exceeds 30 c and sulphate content is over 1300 mg l 1 the cave hosts large gypsum deposits from 40 to 100 m below the entrance that are by products of the reaction between sulphuric acid and the carbonate host rock the lower part of the cave hosts over 1 m thick calcite cave raft deposits which are evidence of long standing probably thermal water in an evaporative environment related to significant air currents sulphur isotopes of gypsum have negative 34 s values from 28 3 to 24 2 typical of sas calcite cave rafts and speleogenetic gypsum both yield young u th ages varying from 68 5 ka to 2 ka bp indicating a rapid phase of dewatering followed by gypsum precipitation in aerate environment this fast water table lowering is related to a rapid incision of the nearby albegna river and was followed by a 20 30 m fluctuation of the thermal water table as recorded in the calcite raft deposits and gypsum crusts

some considerations concerning seismic geomorphology and paleoseismology abstract seismic geomorphology studies landforms which developed in connection with earthquakes among them two different end members may be distinguished 1 seismo tectonic landforms including surface faults and fractures land uplift and subsidence at different scales surface bulges elongate ridges and any other permanent ground deformations directly related to tectonic stress and 2 seismo gravitational landforms such as landslides deep seated gravitational slope deformations sinkholes and fissures due to sediment compaction or liquefaction and sand blows connected with both seismic shaking and gravitational stress a clear cut distinction between the two categories of landforms is not always easy to make and in many instances not really useful while there are in many cases ground effects that might be and should be considered as simultaneous combinations of seismo tectonic and seismo gravitational processes this applies especially to surface fracturing and faulting which could be the combined result of tectonic stress stress produced by seismic shaking and gravitational stress the objective of this paper is to review selected case histories mainly from italy and the mediterranean region in order to show the importance of a comprehensive study of earthquake generated landforms for understanding the seismicity level of the area under investigation we argue that in earthquake prone areas seismic landforms often constitute typical patterns seismic landscapes whose recognition mapping and paleoseismological analysis may help in the evaluation of seismic hazards

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

active tectonics and human survival strategies tectonic movements continuously remould the surface of earth in response to plate motion yet such deformation is rarely taken into account when assessing landscape change and its impact on human land use except perhaps as an occasional hazard to human life or a temporary disruption in the longer term parems of human history however active tectonics also create and sustain landscapes that can be beneficial to human survival forming a complex topography of potentially fertile sedimentary basins enclosed by mountain bard that can facilitate the control and exploitation of food resources especially animal prey we discuss the tectonic history of northwest greece and show how the paleolithic sites of the region are located to take advantage of tectonically created features at both a local and a regional scale we suggest that the association of significant concentrations of early paleolithic sites with tectonically active regions is not coincidental and that on the longer time spans of human biological evolution active tectonics has been an importam selective agent contributing to the development of the human species as an intelligent predator

geomorphic constraints on listric thrust faulting implications for active deformation in the mackenzie basin south island new zealand 1 deformed fluvial terraces preserved over active thrust related folds record the kinematics of folding as fault slip accumulates on the underlying thrust in the mackenzie basin of southern new zealand the kinematics revealed by folded fluvial terraces along the active ostler and irishman creek fault zones are inconsistent with traditional models for thrust related folding in which spatially uniform rock uplift typically occurs over planar fault ramps instead warped and tilted terraces in the mackenzie are characterized by broad continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation by relating this pattern of surface deformation to the underlying thrust with a newly developed simple geometric and kinematic model we interpret both faults as listric thrusts rooted at depth into gently dipping planar fault ramps constraints on the model from detailed topographic surveying of deformed terraces ground penetrating radar over active fault scarps and luminescence dating of terrace surfaces suggest slip rates for the ostler and irishman creek faults of 1 1 1 7 mm yr and 0 5 0 7 mm yr respectively the predicted depth of listric faulting for the ostler fault 0 7 0 2 0 1 km and the irishman creek fault 1 3 0 5 0 1 km generally agrees with geophysical estimates of basin depth in the mackenzie and suggests control of preexisting basin architecture on the geometry of active thrusting despite the potential effects of changes in fault curvature and hanging wall internal deformation the methodology presented here provides a simple tool for approximating the kinematics of surface deformation associated with slip along listric or curviplanar thrust faults

carbon mineralization and lignin content of eroded sediments from a grazed watershed of south africa abstract despite the increasing interest in the role of soil erosion on the global carbon cycle few studies were carried out to evaluate the fate of eroded organic carbon oc at the landscape level although eroded c may constitute an atmospheric c source upon mineralization or a c sink if entrapped it is largely unknown how landscape position and molecular composition influence the fate of terrestrial c mobilized during erosion induced storm events the objective of this study was to assess the impact of soil water erosion on potential carbon mineralization and to interpret these results using additional information on organic matter composition in both soils and sediments the study was conducted in a 23 ha grassland catchment of the south african drakensberg foothill showing numerous features of land degradation the elemental and stable isotope composition and the lignin component of soils from different landscape positions were compared to those of sediments eroded from 1 1 m microplots in addition and to assess changes in oc availability during soil erosion co 2 emissions from soil and eroded sediments were measured continuously under laboratory conditions over a 20 day period the lignin component of the samples was characterized by cuo oxidation our results showed that eroded sediments were enriched in organic carbon by factor 1 8 and in lignin by factor 3 7 lignin characterization indicated that it was less decomposed in eroded sediments than in the original soils but did not control carbon mineralization a negative trend was observed between the c n ratio of eroded sediments and soil and co 2 production suggesting that microbial biomass could be n limited carbon mineralization in eroded sediments greatly exceeded that of soils and was described by a single pool first order model whereas mineralization of soil c followed a sigmoidal pattern we conclude that organic matter present in eroded sediments consists of relatively undecomposed plant material and is mineralized to a greater extent than soil organic matter regardless of landscape position

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

models of the complex source of the el asnam earthquake abstract the el asnam earthquake of 10 october 1980 was originated by a thrust across a sw ne oriented fault 36 km long and 15 km wide it is a complex event with a rupture propagating from the sw to the ne fault mapping hypocenter distribution and b factor studies indicate fault branching to the ne a dislocation model is used to explain the branch with normal faulting at beni rached as a consequence of the thrust across a main fault that changes orientation the mechanism of the 1954 earthquake must be similar even though only normal faulting was observed at the surface

crustal structure of the northern margin of the eastern tien shan china and its tectonic implications for the 1906 m 7 7 manas earthquake abstract the tien shan orogenic belt is the most active intracontinental mountain belt in the world we describe an 86 km long n s trending deep seismic reflection profile which passes through the southern junggar basin located on the northeastern tien shan piedmont two distinct anticlines beneath the northern margin of the tien shan are clearly imaged in the seismic section in addition we have imaged two detachment surfaces at depths of 7 and 16 km the detachment surface at 16 km depth corresponds to the main detachment that converges with the steep angle reverse fault the junggar southern marginal fault on which the 1906 m 7 7 manas earthquake occurred a 12 14 km thick sedimentary basin is imaged beneath the southern junggar basin near shihezi the crust beneath the northern margin of the tien shan is 50 55 km thick and decreases beneath the junggar basin to 40 45 km thick the crustal image of the deep seismic reflection profile is consistent with models derived from nearby seismic refraction data and bouguer gravity anomalies in the same region the faulting associated with the 1906 manas earthquake also fits within the structural framework imaged by the seismic reflection profile present day micro seismicity shows a hypocentral depth distribution between 5 and 35 km with a peak at 20 km we hypothesize that the 1906 manas earthquake initiated at a depth of 20 km and propagated upwards causing northward slip on the sub horizontal detachments beneath the southern junggar basin thus in accord with regional geological mapping the current shortening within the eastern tien shan is accommodated both by high angle reverse faulting and detachment faulting that can be clearly imaged at depth in seismic reflection data

corrosion morphology and cave wall alteration in an alpine sulfuric acid cave kraushohle austria abstract whereas most karstic caves worldwide are formed by carbonic acid a small but significant number of sub surface cavities are the product of sulfuric acid speleogenesis sas in the eastern alps no cave has so far been attributed to this type in this multidisciplinary study we demonstrate that kraushohle in northern styria was indeed formed by sas the cave pattern shows individual chambers 3d mazes and blind galleries as well as typical sas morphologies such as cupolas gypsum replacement pockets corrosion notches and convection niches ceiling pendant drip holes are described here for the first time and these corrosion features are fully consistent with the sas model other features of kraushohle include thick gypsum deposits with strongly depleted 34 s values and other minerals mostly sulfates indicating highly acidic conditions we also studied acid rock interaction processes giving rise to widespread corrosion and concomitant replacement by gypsum petrographic and geochemical analyses reveal the presence of a distinctive alteration layer of highly increased porosity at the interface between the host limestone and the secondary gypsum dissolution and replacement of the limestone was fast enough to prevent the development of c and o isotopic alteration halos but resulted in selective leaching of elements this stable isotope signal is thus different from the pronounced isotope gradient commonly observed in co 2 dominated hypogenic caves petrographic observations reveal that the limestone gypsum replacement was a nearly constant volume process

earthquake faulting as a structural process abstract structural geology is concerned with the history of movement in the earth s crust and the processes by which displacements occur in the upper one third to one half of deforming continental crust displacement is accommodated largely by seismic slip increments on existing faults it follows that earthquakes and related processes are an integral part of structural geology traditionally structural geologists have been preoccupied with the complexity of the finite deformation within fault zones and with the stress states prevailing at the initiation of faults in intact crust future structural work should be directed more towards understanding the dynamic character of fault reactivation during incremental slip and related effects questions of interest include rheological and geometrical controls on the initiation perturbation and termination of ruptures directivity effects associated with rupture propagation the recognition of structures resulting from repeated stress cycling within seismogenic crust and identification of structural features diagnostic of shear stress levels during faulting structures arising from the inter relationships between slip episodes and induced fluid flow are of special importance because these dynamic fault processes appear influential in the development of much fault hosted mineralization mesothermal gold quartz lodes hosted in high angle reverse shear zones of mixed brittle ductile character form illustrative examples of structures that arguably can only be interpreted by seismo structural analysis embodying the concepts listed above

drainage diversions as evidence of propagating active faults example of the el asnam and thenia faults algeria digital elevation models and aerial photographs provide evidence of past drainage diversions associated with known and inferred active faults in northern algeria the el asnam anticline is a fault bend fold that is growing in response to displacement on the historically active el asnam fault the diversion of the fodda river and a sequence of uplifted palaeovalleys across the anticline formed in response to the active southwestward propagation of the sidi ada el ardja segment of the el asnam anticline deformation associated with the 1980 el asnam earthquake ms 7 3 and its effect on drainage demonstrate the occurrence of coseismic uplift of the el asnam anticline associated with slip on the underlying thrust fault similar geomorphic relations are observed between the isser river and the thenia fault diversions of the isser river and evidence for quaternary uplift indicate that the thenia fault which is close to algiers is tectonically active and should be considered to be a source of potentially damaging earthquakes

speleogenesis of an exhumed hydrothermal sulphuric acid karst in cambrian carbonates mount san giovanni sardinia in the past few years the systematic study of caves intercepted by mine workings in southwest sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity these relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves a combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves cave formation had already started in cambrian times but culminated in the carboniferous when most of the large voids still accessible today were formed a key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the cambrian during the quaternary a variety of minerals formed inside the caves calcite and aragonite that yielded sequences of palaeo environmental interest and also barite phosgenite hydrozincite hemimorphite and many others these minerals are in part due to a phreatic thermal hypogenic cave forming phase and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores massive gypsum deposits elsewhere typical of this kind of caves are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage copyright 2013 john wiley sons ltd

horizontal coseismic deformation of the 1999 chi chi earthquake measured from spot satellite images implications for the seismic cycle along the western foothills of central taiwan 1 the 1999 chi chi earthquake mw 7 6 broke a major thrust fault along the western foothills of the central range of taiwan we have measured the horizontal coseismic displacement field by correlating optical satellite images acquired before and after the earthquake these data reveal the fault trace and a clockwise rotation of surface displacements toward the north with much larger displacements and strain in the hanging wall at the surface coseismic slip increases from 5 6 m near the epicenter to 10 11 m to the north in the epicentral area we observe a left lateral strike slip zone trending n125 e and farther north a fault zone trending n s with a right lateral component the data were modeled using elastic dislocations the fault geometry consists of a shallow

the structural evolution of active fault and fold systems in central otago new zealand evidence revealed by drainage patterns abstract central otago in new zealand is an area of active continental shortening in which a peneplain surface cut into schist has been deformed by folds which are developed above buried reverse faults we use the drainage patterns in this region to demonstrate various processes in fold and fault growth and interaction that would be difficult to identify by other means in particular we show 1 how simple asymmetric folds can develop into box folds 2 how apparently continuous ridges were formed by the coalescing of quite separate propagating fold and fault segments 3 evidence for the relative ages or relative uplift rates of adjacent structures and 4 evidence for the propagation direction of folds or faults as they grow the few quantitative estimates we obtain for fault propagation rates suggest an increase in length of 10 50 m per earthquake on faults about 20 km long these estimates are very uncertain but are similar in magnitude to an estimate made in nevada for a normal fault of similar size and are also similar to predicted estimates from theoretical growth models they raise the question of whether fault growth earthquake recurrence rates and climate change can interact to produce semi regular discrete features in an active landscape

co seismic ruptures of the 12 may 2008 ms 8 0 wenchuan earthquake sichuan east west crustal shortening on oblique parallel thrusts along the eastern edge of tibet abstract the m s 8 0 wenchuan earthquake which devastated the mountainous western rim of the sichuan basin in central china produced a surface rupture over 200 km long with oblique thrust dextral slip and maximum scarp heights of 10 m it thus ranks as one of the world s largest continental mega thrust events in the last 150 yrs field investigation shows clear surface breaks along two of the main branches of the ne trending longmen shan thrust fault system the principal rupture on the nw dipping beichuan fault displays nearly equal amounts of thrust and right lateral slip basin ward of this rupture another continuous surface break is observed for over 70 km on the parallel more shallowly nw dipping pengguan fault slip on this latter fault was pure thrusting with a maximum scarp height of 3 5 m this is one of the very few reported instances of crustal scale co seismic slip partitioning on parallel thrusts this out of sequence event with distributed surface breaks on crustal mega thrusts highlights regional ew directed present day crustal shortening oblique to the longmen shan margin of tibet the long rupture and large offsets with strong horizontal shortening that characterize the wenchuan earthquake herald a re evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau and require a re assessment of seismic hazard along potentially under rated active faults across the densely populated western sichuan basin and mountains

mechanics of wedge shaped fault blocks 2 an elastic solution for extensional wedges listric planar low angle and high angle normal faults are common in hanging walls of detachment faults an elastic model has been developed to evaluate the role of basal friction wedge geometry pore fluid pressure within the wedge and boundary conditions applied along the wedge rear in controlling the stress distribution in an extensional fault wedge this model assumes a stress free condition on the top and fractional sliding on the base of the wedge respectively a linear variation of stress components as a function of depth along the wedge rear and a uniform horizontal stress applied on the wedge toe the model predicts that 1 for the surface slope equal to zero a thin wedge favors development of high angle and planar faults whereas a thick wedge favors development of low angle and listric normal faults variation of pore fluid pressures along the basal detachment fault hardly affects the predicted fault geometry pore fluid pressure within the wedge is critical in controlling the state of stress in the wedge higher values of the internal pore fluid pressure promote low angle normal faulting and locally high angle reverse faulting 2 variation of surface slope and the uniform horizontal normal stress applied at the wedge toe does not affect the predicted fault geometry appreciably although the distribution of deviatoric stress magnitude changes for different cases and 3 listric normal faults are predicted in all computations and the fault curvature increases as the vertical gradient of the horizontal normal stress along the wedge rear the wedge angle surface slope dip angle and the internal pore fluid pressure increase the model provides a simple conceptual guide to deciphering the formation of complex fault geometries and cross cutting relationships as a function of mechanical parameters related to geologic processes and settings for example it provides an explanation for why low angle normal faults cut high angle normal faults in hanging walls of some detachment fault systems in the u s cordillera

sulfur and oxygen isotopes in the gypsum deposits of the provalata sulfuric acid cave macedonia abstract sulfur stable isotopes from cave sulfates mainly gypsum have been used in a number of studies to trace the source of sulfur in caves formed by sulfuric acid but only few studies apply combined use of sulfur and oxygen stable isotopes to further understand the processes operating in sulfuric acid speleogenesis sas here we present results of a detailed study of the distribution of sulfur and oxygen stable isotopes within the gypsum deposits formed during sulfuric acid speleogenesis of provalata cave macedonia the 18o vs vsmow values range between 3 9 and 8 2 and the 34s vs cdt values between 7 5 and 0 7 we found a strong positive correlation between the 18o and 34s values with a 0 5 increase in the 34s for every 1 increase in the 18o indicating that both oxygen and sulfur isotopes were concurrently affected during the oxidation process we attribute these effects to be either due to environmental control concentrations of h2s and o2 or due to isotope fractionation during multi step microbial oxidation also affected by the environmental conditions additionally a shift of 1 85 in the 34s values prior to the h2s oxidation is found indicating evolution of the h2s 34s in the sas system the wide range of both 18o and 34s values in the gypsum deposits of the small provalata cave show that both the number of samples and their location can be an important factor for the understanding of sulfuric acid speleogenesis using stable isotopes

role of fluids in surface deformation caused by the 1999 chi chi earthquake in taiwan the 1999 chi chi earthquake significantly altered the landscape of central taiwan surface deformation produced by the earthquake along the trace of the chelungpu thrust can be classified into two styles 1 uplift without significant surface rupture and 2 uplift accompanied by surface rupture here we examine areas that exhibited the first style of deformation e g wufeng seismic stress at the time of the main shock may have been relieved by high pore fluid pressure in a 300 m thick sand and gravel aquifer along the thrust fault frictional heating of these sediments resulted in thermal expansion and an increase in pore fluid pressure high pore fluid pressure damped seismic wave energy and enhanced intergranular slips of unconsolidated sandy and gravel sediments which were possibly assisted by sulphuric acid corrosion leading to a high sulphate content in the groundwater c 70 mg l 1 these changes permitted surface folding and terrace style uplifting to occur without significant rupture in contrast other areas in which the second style of deformation is dominant e g fengyuen shihkang have thin 0 10 m sand and gravel deposits and lower concentrations of sulphate c 30 mg l 1 in groundwater in these areas sediments were heated but not sufficiently to produce significant thermal expansion and increase in pore fluid pressure accumulation of stress in these locations led to rupture at the ground surface with the formation of steep fault scarps the areas exhibiting the first deformation style are characterized by the presence of high pore fluid pressure frictional heat conduction and possibly chemical corrosion related to sulphuric acid attack and formation of sulphate in contrast to those involving significant uplift and surface rupture the areal distribution of these two surface deformation styles suggests that the aforementioned fluid related subsurface processes may have altered the characteristics of sediments and caused diverse responses to the quake copyright 2002 john wiley sons ltd

the 21 may 2003 zemmouri algeria earthquake mw 6 8 relocation and aftershock sequence analysis 1 a strong earthquake mw 6 8 struck the coastal region east of algiers and the tell atlas of algeria on 21 may 2003 and was responsible of severe damage and about 2400 casualties the coastal mainshock was followed by a large number of aftershocks the largest reaching mw 5 8 on 27 may 2003 we study the mainshock first major aftershocks and about 900 events recorded by temporary seismic stations using master event approach and double difference dd methods although the seismic station array has a large gap coverage the dd algorithm provides with an accurate aftershocks location the mainshock hypocenter relocation is determined using three major aftershocks 5 0 mw 5 8 chosen as master events the new mainshock location shifted on the coastline 36 83n 3 65e at 8 10 km depth seismic events extend to about 16 km depth and form a n 55 60 e trending and 45 55 se dipping fault geometry up to now it is the unique among the recently studied seismic events of the tell atlas of algeria mainshock and aftershocks relocation the thrust focal mechanism harvard cmt n 57 44 se dip 71 rake and the seismic moment 2 86 1019 nm infer a 50 km long fault rupture that may appear at the sea bottom at 6 to 12 km offshore north of the coastline the zemmouri earthquake occurred along the complex thrust and fold system of the tell atlas and provides with new constraints on the earthquake hazard evaluation in northern algeria

speleothems from mawsmai and krem phyllut caves meghalaya india some evidences on biogenic activities the mawsmai cave and krem phyllut caves east khasi hills meghalaya india has so far not yet attracted the attention of geomicrobiologists observations and hypotheses on the possible influence of identified microorganisms for speleothem formations in meghalaya are reported for the first time xrd studies identified calcite in speleothems and gypsum in cave wall deposits as the dominant minerals sem edax showed interesting microfabric features showing strong resemblance with fossilised bacteria calcified filaments needle calcite and numerous nano scale calcite crystals highly weathered and disintegrated crystals of calcite that point towards a significant microbial influence in its genesis thin section petrography showed laminated stromatolitic features the microorganisms identified by conventional isolation and further evaluation of isolates by molecular techniques include bacillus cereus bacillus mycoides bacillus licheniformis micrococcus luteus and actinomycetes microscopic observations also showed unidentifiable cocci and four unidentifiable strains of caso4 gypsum precipitating bacteria experimental studies confirmed that these bacteria are able to precipitate calcium minerals calcite gypsum minor amounts of dolomite in the laboratory these results allow us to postulate that species like these may contribute to active biogenic influence in the cave formations at meghalaya

source and genesis of sulphate and phosphate sulphate minerals in a quartz sandstone cave environment gypsum caso4 2h2o alunite kal3 so4 2 oh 6 and rare phosphate sulphate sanjuanite al2 po4 so4 oh 9 h2o and rossiantonite al3 po4 so4 2 oh 2 h2o 14 have recently been identified as secondary mineral deposits in different quartz sandstone caves in the gran sabana region venezuela due to the extended time scale required for speleogenesis in the hard and barely soluble quartz sandstone lithology these caves are considered to be as old as 20 to 30 my the study of these peculiar secondary mineral deposits potentially reveals important insights for understanding the interaction between deep superficial and atmospheric processes over thousands to perhaps millions of years in this study chemical and petrographic analyses of potential host rock sources sulphur and oxygen isotope ratios and meteorological hydrological and geographical data are used to investigate the origin of sulphates and phospho sulphates the results suggest that the deposition of sulphates in these caves is not linked to the quartz sandstone host rock rather these mineral deposits originate from an external atmospheric sulphate source with potential contributions of marine non sea salt sulphates terrestrial dimethyl sulphide and microbially reduced h2s from the forests or peatbogs within the watershed air currents within the caves are the most plausible means of transport for aerosols driving the accumulation of sulphates and other secondary minerals in specific locations moreover the studied sulphate minerals often co occur with silica speleothems of biological origin although this association would suggest a possible biogenic origin for the sulphates as well direct evidence proving that microbes are involved in their formation is absent nonetheless this study demonstrates that these quartz sandstone caves accumulate and preserve allogenic sulphates playing a yet unrecognized role in the sulphur cycle of tropical environments

sulfuric acid speleogenesis sas close to the water table examples from southern france austria and sicily caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings from arid regions to mid latitude and alpine areas h2s is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers in tectonically disturbed areas major fractures eventually allow these h2s bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid this extremely strong acid reacts with the carbonate bedrock creating caves some of which are among the largest and most spectacular in the world production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment these caves are generated at or immediately above the water table where condensation corrosion processes are dominant creating a set of characteristic meso and micromorphologies due to their close connection to the base level these caves can also precisely record past hydrological and geomorphological settings certain authigenic cave minerals produced during the sulfuric acid speleogenesis sas phase allow determination of the exact timing of speleogenesis this paper deals with the morphological geochemical and mineralogical description of four very typical sulfuric acid water table caves in europe the grotte du chat in the southern french alps the acqua fitusa cave in sicily italy and the bad deutsch altenburg and kraushohle caves in austria

seismotectonics of the el asnam earthquake the mechanism of the el asnam earthquake of 10 october 1980 ms 7 2 the strongest recorded in northwestern africa is compatible with a convergence between the african and european plates the thrust is also consistent with field observations and with long period data from the global network aftershocks cluster around the fault trace with a maximum depth of 12 km maximum vertical displacement is 6 m and there is some left lateral motion the fault trace of the 1954 earthquake at beni rached was also reactivated

low angle normal faults in lower eocene chalks near beer sheva israel abstract forty outcrops of lower eocene chalks mor formation around beer sheva were examined for faulting ten well exposed normal faults with mean dip and strike of 39 6 and 294 n66 w 28 respectively were found in four outcrops the timing of fault movement is partly constrained by unfractured lower eocene chert nodules which follow some of the fault traces hence the faults are interpreted to be the result of dynamic failure due to horizontal nne ssw compression during the early eocene horizontal compression is implied by analogy to descriptions of recent faulting caused by an earthquake in another location local folding in the lower eocene secondary fractures and flat and ramp structures associated with the investigated faults

accretion mass wasting and partitioned strain over the 26 dec 2004 mw9 2 rupture offshore aceh northern sumatra abstract the aceh segment of the sunda arc absorbed the largest slip along the 26 december 2004 mw9 2 subduction earthquake rupture and caused the highest and most disastrous tsunami run ups sea floor disruption marks the frontal active part of the accretionary prism along that segment an rov bathymetric and seismic survey r v natsushima jamstec 2 3 2005 revealed pervasive and deeply rooted fracturing along the upper trench slope grabens and ejecta clasts from fluid escape along the crest of an anticline ridge coupled with mass wasting and erosional scouring on the slope below it specific features of the disruption and its patchy distribution suggest coseismic faulting and folding with gravitational collapse of the steepened anticline forelimb the same ridge 40 km along strike was pristine disruption was also generally undetected by rov on the ache basin side of the forearc ridge suggesting a minor role for shaking only some of the faults in the imbricate and segmented accretionary structure ruptured but together they may account for 2004 sea floor rupture along the aceh segment this hypothesis accounts for unusual thrust aftershocks and suspended sediment along the frontal active part of the prism it can also account for the huge tsunami heights in northern sumatra because faults in the prism are steeper than the megathrust down dip and because slip may be larger in the prism following prior blind ruptures rare but large coseismic deformation of the prism can generally account for the erosional morphology of trench slopes and for al least some tsunami earthquakes on the landward side of the forearc high the west andaman fault borders the aceh basin and branches southward into a fault crossing obliquely the forearc high seismic profiles at the bifurcation image a flower structure with strain partitioning and an active dextral pull apart this fault system however did not release significant strain in 2004

catchment scale carbon redistribution and delivery by water erosion in an intensively cultivated area large uncertainties still exist on both the rates of soil organic carbon soc mobilization by soil erosion as well as the fate of the eroded c using a range of techniques we characterized soil c redistribution by water erosion in two small agricultural catchments in the belgian loess belt results from rainfall simulations showed that c enrichment in eroded sediments was much higher than clay enrichment average enrichment ratios of 2 47 and 1 36 on average respectively selectivity was also observed in depositional processes sediments deposited within the catchments were depleted in c and finer fractions as compared to the source soil selectivity was much more pronounced in winter than in summer which is related to the degree of aggregation of the transported deposited sediment the combined selectivity of erosion and depositional processes resulted in a significant c enrichment of the sediment exported from the catchments with the c enrichment ratio cer between 1 2 and 3 0 overall catchment scale c enrichment was higher than clay enrichment enrichment ratios varied both with season and event intensity the uncertainties on catchment wide erosion and deposition rates precluded the closure of the sediment c budgets however using a simple model we were able to show that both the magnitude and variation of observed catchment scale cer was as expected from our understanding of c mobilization and deposition within the catchment this suggests that most of the mobilized c was not mineralized during the erosion events but either re deposited within the catchment or exported with the runoff this was confirmed by the comparison of the elemental and isotopic signatures between exported sediments and source soil in order to assess the role of erosion in the c cycle understanding how c is mobilized and re deposited selectively by erosion appears therefore as important as improving our understanding of the impact of erosion on c mineralization

carbonate minerals in the global carbon cycle abstract carbonate minerals constitute earth s largest c reservoir this reservoir is considered unimportant to the global c cycle over long periods of time e g 10 6 yrs because it provides balanced sources and sinks of atmospheric co 2 as carbonate minerals precipitate and dissolve from carbonic acid respectively however carbonate mineral reactions may impact the carbon cycle at short time scales 10 2 to 10 5 yrs particularly when atmospheric pco 2 changes by several hundred ppm as exemplified by the paleocene eocene thermal maximum at transitions between glacial interglacial times and over the past century from anthropogenic inputs here i review recent literature about mechanisms in which carbonate minerals may impact the global carbon cycle carbonate mineral dissolution which increases dissolved inorganic carbon dic concentrations may represent a net atmospheric co 2 sink as primary productivity consumes dic resulting in organic c burial in fluvial systems of carbonate terrains alternatively carbonate minerals dissolved by sulfuric and nitric acids may represent an atmospheric source of co 2 with no rapid balancing atmospheric sink sulfuric acid dissolves carbonate minerals of modern carbonate platform sediments and water filled sinkholes and in the deep sea at the base of carbonate platform scarps in terrestrial landscapes sulfuric acid dissolves carbonate minerals of karst terrains hypogene caves and in comminuted glacial sediments nitric acid forms from oxidation of reactive n which has doubled in the past hundred years as humans fix atmospheric n 2 similar to some reactions involving sulfuric acid nitric acid dissolution of carbonate minerals represents a net source of atmospheric co 2 this source is concentrated in fertilized agricultural fields in carbonate terrains each of these processes represents a small flux relative to major c exchanges such as volcanic sources and silicate mineral weathering but collectively they could impact the c cycle at magnitudes similar to these major processes these impacts may increase as humans further alter elemental cycles of s and n

defining fault avoidance zones and associated geotechnical properties using masw a case study on the springfield fault new zealand abstract the springfield thrust fault at dalethorpe west canterbury new zealand provides a test case to explore the correlation between shear wave velocities at a range of scales and direct field observations of distributed deformation and outcrop properties the springfield fault ruptures to the surface through hard torlesse greywacke overlain on a flight of late quaternary glacio fluvial terraces by 5 m of gravel fault slip has displaced all but the lowest terraces revealing the geometry and location of faulting we used multi channel analysis of surface waves and meter scale cross hole measurements to map shear wave velocities below the lowest apparently undisplaced terrace we correlated these surveys with geotechnical parameters measured at outcrops and investigated relationships in the laboratory both field and laboratory results indicate that the shear wave velocity of torlesse greywacke declines sharply with increasing fracture density field surveys further indicate that relatively unweathered high velocity greywacke is being exhumed in a bivergent wedge between two opposite facing thrusts the fracturing and low shear wave velocities are focused in a wide low velocity damage zone that has developed in the hanging wall of the main thrust and a smaller but similar feature in the hanging wall of the backthrust this is consistent with the geomorphology of the site our correlations of geomorphic indicators of deformation with fault zone velocity structure provide a useful method with which to characterize the distribution of cumulative strain this type of analysis has utility for land use planning on or close to active faults especially where they are obscured by fluvial deposits

sulfuric acid caves of italy a review abstract in italy especially along the apennine chain numerous active and inactive sulfuric acid speleogenetic sas caves have been documented in the last two decades here we present an overview of these peculiar hypogene systems illustrating their main geomorphological and mineralogical features and the microbial signatures observed in the active underground environment sas caves are widely distributed in the northern and central apennines whereas they are less abundant in the southern apennines in the apulian foreland in sicily and in sardinia their location is significantly influenced by lithological and structural rock properties as they occur in carbonate areas where acidic fluids deriving from the interactions with deep seated sulfates and or sulfides rise through deeply rooted geological structures geomorphological observations demonstrated sub horizontal maze passages to be one of the most favorite arrangements for sas caves whereas gypsum sulfur and alunite supergroup minerals are the most typical sulfuric acid by products the 34 s results demonstrated the deep seated h2s sources to be mainly related to the interaction between triassic evaporites and hydrocarbons

occurrence of hypogenic caves in a karst region examples from central italy the caves of the umbria and marche regions in central italy are made up of three dimensional maze systems that display different general morphologies due to the various geological and structural contexts at the same time the internal morphologies of the passages galleries and shafts present some similarity with solutional galleries characterized by cupolas and blind pits anastamotic passages roof pendants and phreatic passages situated at different levels some of these caves are still active as is the case for frassassi gorge parrano gorge and acquasanta terme with galleries that reach the phreatic zone where there is a rising of highly mineralized water rich in hydrosulfydric acid and with erosion of limestone walls and the formation of gypsum elsewhere there are fossil caves such as monte cucco and pozzi della piana where large speleothems of gypsum are present 500 m or more above the regional water table in all of these important karst systems it is possible to recognize basal input points through fracture and intergranular porosity networks at the base of the oxidizing zone in the core of the anticline where mineralized water rises up from the triassic evaporitic layers in small hydrogeological circuits different underground morphologies can derive from the presence of a water table related to an external stream or from the confined setting of the carbonate rocks underlying low permeable sedimentary cover where artesian conditions can occur

sulfuric acid speleogenesis in the majella massif abruzzo central apennines italy abstract many active and inactive hypogene sulfuric acid cave systems are known along the apennines italy the cavallone bove cave system is located in the external part of the central apennine chain in the majella massif and opens at 1470 m asl along the taranta gorge south of chieti the presence in these caves of peculiar geomorphological features such as feeders rising channels megacusps cupolas and replacement pockets offers evidence of rising acidic fluids the secondary mineral deposits including meter size white gypsum deposits alunite jarosite black layers of iron manganese oxides and hydroxides along with a rare association of authigenic rutile ilmenite minerals indicate a sulfuric acid origin stable isotope analyses of sulfates further confirm a sulfuric acid speleogenetic sas origin of these minerals and in general of the whole cave system with h2s coming from the bacterial sulfate reduction of deep seated triassic evaporites interacting with hydrocarbons alunite dating demonstrates this water table sas cave to have been active at least until 1 52 0 28 ma all the evidence suggests that cavallone bove is an ancient sulfuric acid karst system that was uplifted

precipitation of iron in microbial mats of the spring waters of borra caves vishakapatnam india some geomicrobiological aspects the borra caves vishakapatnam india can be described as a speleothem cave with significant amounts of unexplored microbial mats in spring waters here we present the first observations and hypotheses on the possible impact of the microorganisms in these mats on the cave formation focusing on their role on iron mineral precipitation the spring waters ph neutral 7 5 7 7 contained dissolved metals like iron and the organic mat sludge ph 7 0 7 3 had a toc content of approximately 5 4 wt geochemically the spring waters deep below the microbial mats contained fe 369 ppb sr 198 ppb and the organic mat sludge contained mg 9 ppm fe 427 ppb zn 149 ppb sr 190 ppb xrd observations displayed fe minerals dominantly hematite minor amounts of zinc gallium sulfide and nitrofuryl compounds at least four groups of bacteria identified by direct microscopy and sem edx on the basis of morphology could be observed in all samples leptothrix like organisms entombed bacterial mineral sheaths a few stalks of gallionella like organisms and some additional bacteria that could not be further identified leptothrix like organisms contained 43 22 60 08 wt fe and the mineral precipitated near and around these bacteria in the actual unaltered samples on site contained 30 76 45 22 wt fe as identified and quantified by sem edx this study indicates that the precipitation of these iron rich mats in the spring waters could be linked to the presence of abundant active communities of iron precipitating bacteria at borra caves vishakapatanam

an aftershock study of the el asnam algeria earthquake of 1980 october 10 summary an array of 28 portable seismic stations was operated in the region of el asnam following the magnitude 7 3 ms thrust earthquake of 1980 october 10 locations of 494 events are presented in this paper and provide an indication of the overall form of the aftershock distribution tests to establish location accuracy particularly depth reduce this set to 277 events which it is argued are well constrained p waves alone are used in this study as a consequence of a debate about the reliability of reading s phases from the reduced set of 277 events 81 events provide well constrained focal mechanisms the locations are presented in the form of maps and cross sections and discussed in relation to information already derived from field mapping of surface breaks and teleseismic studies of the waveforms of the main event the zone of surface faulting including secondary normal faulting extended for 35 km but the aftershock distribution extends for twice this distance along the part of the fault which experienced substantial displacement in the main shock the fault plane itself appears to be devoid of aftershocks although many lie in the footwall beneath the fault at junctions between segments of thrust faulting strike slip motion occurs this is apparent in the aftershock focal mechanisms and in the surface ruptures in one place the large number of aftershocks in the north east area appears to be due to the reactivation of a fan like system of smaller reverse faults associated with surface folding activity at the south west end is considerably less than that in the north east and is not obviously associated with recognizable geological or morphological features

earthquake relocation in the ligurian sea western mediterranean geological interpretation abstract relocated epicenters are computed with a model based on complex local structure i e oceanic floor in the central ligurian basin and thinned continental margins by superposing these relocated earthquakes on a basement bathymetric map the structural relations are clearly demonstrated compressive stress towards the west northwest is confirmed in the northern ligurian basin by focal mechanism study according to our results most of the earthquakes appear to be shallow and linked to rejuvenation of older distensive and strike slip structures on margins as in the basin by a compressional motion

microbiology and geochemistry in a hydrogen sulphide rich karst environment abstract cueva de villa luz a hypogenic cave in tabasco mexico offers a remarkable opportunity to observe chemotrophic microbial interactions within a karst environment the cave water and atmosphere are both rich in hydrogen sulphide measured h 2 s levels in the cave atmosphere reach 210 ppm and so 2 commonly exceeds 35 ppm these gases plus oxygen from the cave air are absorbed by freshwater that accumulates on cave walls from infiltration and condensation oxidation of sulphur and hydrogen sulphide forms concentrated sulphuric acid drip waters contain mean ph values of 1 4 with minimum values as low as 0 1 the cave is fed by at least 26 groundwater inlets with a combined flow of 200 300 l s inlet waters fall into two categories those with high h 2 s content 300 500 mg l mean p co 2 0 03 0 1 atm and no measurable o 2 and those with less than 0 1 mg l h 2 s mean p co 2 0 02 atm and modest o 2 content up to 4 3 mg l both water types have a similar source as shown by their dissolved solid content however the oxygenated water has been exposed to aerated conditions upstream from the inlets so that original h 2 s has been largely lost due to outgassing and oxidation to sulphate increasing the sulphate concentration by about 4 chemical modelling of the water shows that it can be produced by the dissolution of common sulphate carbonate and chloride minerals redox reactions in the cave appear to be microbially mediated sequence analysis of small subunit 16 s ribosomal rna genes of 19 bacterial clones from microbial colonies associated with water drips revealed that 18 were most similar to three thiobacilli spp a genus that often obtains its energy from the oxidation of sulphur compounds the other clone was most similar to acidimicrobium ferrooxidans a moderately thermophilic mineral sulphide oxidizing bacterium oxidation of hydrogen sulphide to sulphuric acid and hence the cave enlargement is probably enhanced by these bacteria two cave enlarging processes were identified 1 sulphuric acid derived from oxidation of the hydrogen sulphide converts subaerial limestone surfaces to gypsum the gypsum falls into the cave stream and is dissolved 2 strongly acidic droplets form on the gypsum and on microbial filaments dissolving limestone where they drip onto the cave floors the source of the h 2 s in the spring waters has not been positively identified the villahermosa petroleum basin within 50 km to the northwest or the el chichon volcano 50 km to the west may serve as source areas for the rising water depletion of 34 s values 11 7 for sulphur stabilized from h 2 s in the cave atmosphere along with the hydrochemistry of the spring waters favour a basinal source

hypogene sulfuric acid speleogenesis and rare sulfate minerals in baume galiniere cave alpes de haute provence france record of uplift correlative cover retreat and valley dissection the oxidation of hydrocarbons and sulfide sources h2s pyrite produces sulfuric acid that strongly reacts with bedrock causing limestone dissolution and complex interactions with other minerals from the bedrock or from cave fillings mainly clays this type of cave development known as sulfuric acid speleogenesis sas is a subcategory of hypogene speleogenesis where aggressive water rises from depth it also produces uncommon minerals mainly sulfates the typical byproducts of sas baume galiniere is located in southern france in the vaucluse spring watershed this small maze cave displays characteristic sas features such as corrosion notches calcite geodes iron crusts and various sulfate minerals sulfur isotopes of sas byproducts jarosite and gypsum clearly show they derive from pyrite oxidation using xrd and micro raman spectroscopy thirteen minerals were identified including elemental sulfur calcite quartz pyrite goethite gypsum and fibroferrite plus all of the six members of the jarosite subgroup jarosite argentojarosite ammoniojarosite hydroniumjarosite natrojarosite plumbojarosite the baume galiniere deposits are the first documented cave occurrence of argentojarosite and the second known occurrence of plumbojarosite hydronium jarosite ammoniojarosite and fibroferrite in the vaucluse watershed there were numerous upwellings of deep water along major faults located at the contact of the karstic aquifer and the overlying impervious covers the mixing of deep and meteoric waters at shallow depths caused pyrite depositions in numerous caves including baume galiniere sulfuric acid speleogenesis occurred later after base level drop when the cave was under shallow phreatic conditions then in the vadose zone with oxidation of pyrites generating sulfuric acid attenuated oxidation is still occurring through condensation of moisture from incoming air baume galiniere cave records the position of the semi impervious paleo cover and documents its retreat in relationship to valley incision caused by uplift and tilting of the vaucluse block during the neogene

interpretation of radon anomalies in seismotectonic and tectonic gravitational settings the south eastern crati graben northern calabria italy the study area is located in the south eastern part of the crati valley northern calabria italy which is a graben bordered by n s trending normal faults and crossed by nw se normal left lateral faults numerous severe crustal earthquakes have affected the area in historical time present day seismic activity is mainly related to the n s faults located along the eastern border of the graben in this area much seismically induced deep seated deformation has also been recognised in the present paper radon concentrations in soil gas have been measured and compared with a lithology b quaternary faults c historical and instrumental seismicity and d deep seated deformation the results highlight the following a there is no evidence of a strong correlation between lithology and the radon anomalies b a clear correlation between the n s geometry of radon anomalies and the orientation of main fault systems has been recognised except in the southernmost part of the area where the radon concentrations are strongly affected by the superposition of the n s and the nw se fault systems c epicentral zones of instrumental and historical earthquakes correspond to the highest values of radon concentrations probably indicating recent activated fault segments in particular high radon values occur in the zones struck by earthquakes in 1835 1854 and 1870 d deep seated gravitational deformation generally coincides with zones characterised by low radon concentrations in the studied area the anisotropic distribution of radon concentrations is congruent with the presence of neotectonic features and deep seated gravitational phenomena the method used in this study could profitably contribute towards either seismic risk or deep seated gravitational deformation analyses

seismotectonics of the lower cheliff basin structural background of the el asnam algeria earthquake the 1980 el asnam earthquake should be understood within its tectonic environment a seismotectonic map of the lower cheliff basin scale 1 500 000 has been synthesized from known geologic tectonic and seismological work on the region and from satellite photos the data set was integrated by a computer in order to handle different scales and projections several important tectonic features divide the region into 5 domains active faults and recent folds are consistent with a nnw sse direction of compression the cheliff basin is limited to the south by the relizane fault the basin is also crossed by three broken folds the eastern one being the one associated with the el asnam fault historical and instrumental seisinicity seems to be located at both ends of relizane fault it is suggested that the sites corresponding to folds and reverse faulting crossing the basin are relevant to seismic risk a simple tectonic model is proposed

the mineral springs of the scrajo spa sorrento peninsula italy a case of natural seawater intrusion this paper deals with the mineral springs feeding the scrajo spa in the sorrento peninsula southeast of naples approximately 6 km from castellammare di stabia another spa location the scrajo mineral water is sulphureous salt bromine iodic and co2 rich the two hydromineral areas fall within the groundwater basin of mt faito formed chiefly by limestones due to the high permeability of the limestones there is considerable rainwater infiltration which recharges a basal fresh groundwater resting on denser seawater this groundwater body feeds the mineral springs of the scrajo spa the springs of castellammare di stabia and some submarine springs all the data gathered for the scrajo springs led to propose the following mineralisation scheme 1 the basal fresh groundwater of mt faito on underlying seawater receives endogenous contributions of co2 and h2s which cause a natural seawater intrusion within the fresh groundwater 2 the upwelling of gases would appear to occur via the major faults which bound sorrento peninsula to the nw 3 during the year the chemistry of the springs changes according to different degrees of seawater intrusion the minimum occurs in june and the maximum in november the close interaction between the sea and the scrajo s mineral waters but also those of castellammare di stabia highlights their particular vulnerability not only to over extraction of groundwater but also to climate change finally a hypothesis is presented to explain the connection between the mineral waters rich in co2 and h2s and the concentration of karst phenomena observed in the scrajo area

puente hills blind thrust system los angeles california we describe the three dimensional geometry and quaternary slip history of the puente hills blind thrust system pht using seismic reflection profiles petroleum well data and precisely located seismicity the pht generated the 1987 whittier narrows moment magnitude m w 6 0 earthquake and extends for more than 40 km along strike beneath the northern los angeles basin the pht comprises three north dipping ramp segments that are overlain by contractional fault related folds based on an analysis of these folds we produce quaternary slip profiles along each ramp segment the fault geometry and slip patterns indicate that segments of the pht are related by soft linkage boundaries where the fault ramps are en echelon and displacements are gradually transferred from one segment to the next average quaternary slip rates on the ramp segments range from 0 44 to 1 7 mm yr with preferred rates between 0 62 and 1 28 mm yr using empirical relations among rupture area magnitude and coseismic displacement we estimate the magnitude and frequency of single m w 6 5 6 6 and multisegment m w 7 1 rupture scenarios for the pht manuscript received 16 november 2001

faulting mechanism of the el asnam algeria 1954 and 1980 earthquakes from modelling of vertical movements abstract since 1980 most of the papers published on the el asnam earthquake concern the geological and seismological aspects of the fault zone only one paper published by ruegg et al 1982 constrains the faulting mechanism with geodetic measurements the purpose of this paper is to reexamine the faulting mechanism of the 1954 and 1980 events by modelling the associated vertical movements for this purpose we used all available data and particularly those of the levelling profiles along the algiers oran railway that has been remeasured after each event the comparison between 1905 and 1976 levelling data shows observed vertical displacement that could have been induced by the 1954 earthquake on the basis of the 1954 and 1980 levelling data we propose a possible model for the 1954 and 1980 fault systems our 1954 fault model is parallel to the 1980 main thrust fault with an offset of 6 km towards the west the 1980 dislocation model proposed in this study is based on a variable slip dislocation model and explains the observed surface break displacements given by yielding et al 1981 the dewey 1991 and avouac et al 1992 models are compared with our dislocation model and discussed in this paper

fracture interaction in the gregory rift east africa abstract vertical fracture is important and fracture interaction is quite intensive in the central gregory rift crack branching and non coplanar crack interactions in the rift are characterized for major and minor faults these two manifestations follow theoretical and experimental angular relationships of fracture reasonably well mantle diapirism seems to have been responsible for both tensile probably unstable fracture and block tilting ultimately resulting in fault dips deviating from the vertical

source mechanisms of twenty six large shallow earthquake ms 6 5 during 1980 from p wave first motion and long period rayleigh wave data source mechanisms of 26 large shallow earthquakes are determined in terms of a double couple point source with a correction for the nondirectional part of source finiteness by using p wave first motions and long period rayleigh wave spectra recorded on wwssn ida and gdsn networks the combined use of both data sets allows us to determine the double couple mechanism uniquely in most cases constrained linear moment tensor inversion m xz m yz 0 correctly determines the strike of the fault but fails to estimate the dip and underestimates the scalar moment all thrust events along the deep sea trenches analyzed in this study show nodal planes which dip perpendicular to the trench axis at an angle shallower than 45 the fit to data of the double couple inversion is comparable to that of the constrained moment tensor inversion using the phase spectra of surface waves we can detect a slow source process with an accuracy of about 10 to 20 sec

elastic dislocation modelling for prediction of small scale fault and fracture network characteristics predictingthe effects of small scale faults and fractures on reservoirbehaviour requires a definition of their spatial distribution orientation and mode elastic dislocation ed theory can predict the distribution of displacement strain and stress in the rock volume surrounding major faults from mapping of fault geometry and slip distribution in 3d seismic reflection datasets the intensity of small scale faulting can be related to the predicted local strain or the degree to which the shear stresses exceeded the rock failure envelope we illustrate the methodology with three case studies i a relatively simple thrust anticline from venezuela where hydro carbons are trapped in pliocene sandstones within the faulted hanging wall anticline ii the gull faks field and of the north sea and iii the miskar field offshore tunisia where large seismically mapped normal faults are forward modelled to predict small scale fault characteristics for comparison with detailed interpretation and seismic attribute analysis key requirements for the development of a robust predictive model of the small scale fault and fracture network are a geometrically consistent framework model judicious choice of mechanical properties and a reasonable estimate of regional background strain

incubation experiments to constrain the production of methane and carbon dioxide in organic rich shales of the permian irati formation parana basin abstract the permian irati formation in brazil hosts organic rich shales and heavy hydrocarbons suitable for biogenic production of methane ch4 and carbon dioxide co2 in this study shale samples from the irati formation were used in laboratory incubation experiments performed under different temperatures 22 c 50 c 70 c and 80 c to evaluate the generation of ch4 and co2 under thermal conditions compatible with biodegradation in shallow gas systems

control of rupture by fault geometry during the 1980 el asnam algeria earthquake summary the el asnam earthquake of 1980 october 10 ms 7 3 occurred on a segmented reverse fault in the atlas mountains of algeria this report re examines the teleseismic data for the main shock and major aftershocks in the light of detailed studies of the surface breaks geodetic changes and aftershock distribution the observed thrust fault is split into southern central and northern segments by distinct offsets and changes in trend the southern and central segments are each about 12 km long but the northern segment showed only 3 4 km of surface thrust breaks however widespread tensional faulting on ridges in the north east area together with focal mechanisms of locally recorded aftershocks indicates that a series of imbricate listric thrusts exists to the north of the northern fault segment using isc arrival time lists a relative relocation scheme is applied to the main shock and major aftershocks to improve their locations with respect to the mapped faults the main shock epicentre was at the south west end of the fault system in a zone where the thrust has a zig zag surface trace by contrast most of the major aftershocks were located further north east and were associated with the northern thrust segment and the imbricate thrusts to the north the largest aftershock mb 6 1 which occurred about 3 hr after the main shock was located to the east of the main thrust fault beneath the chelif alluvial basin first motion fault plane solutions are presented for the main shock and largest aftershock the main shock solution indicates a fault plane dipping 54 nw with strike 040 the aftershock solution however has a more e w trend 080 in agreement with the trends of the basin edges near its location the rupture history of the main shock is investigated by forward modelling of the long period p waves four subevents are clearly distinguishable the first three subevents occurred in rapid succession and contributed to the first cycle of the p wave radiation these three subevents represent the successive rupturing of the southern central and northern fault segments in order to match the observed waveforms these three ruptures must have different mechanisms and moments the fault segments have successively shallower dipts from south to north 54 45 and 40 respectively and the central segment had the largest moment release in agreement with the geodetic data of ruegg et al the delay times between the three sources suggest a rupture velocity of about 3 5 km s 1 and their nucleation depths were 7 km the junctions between the fault segments acted as geometric barriers to the rupture propagation but were broken by its passage the fourth subevent of the main shock produced the second cycle of the p wave radiation it began about 18 s after the first i e several seconds after the end of the third rupture nabelek demonstrates that the fourth subevent occurred on a shallow angle 20 thrust plane examination of the locally recorded aftershocks suggests that this plane is a decollement surface underlying the imbricate thrusts of the north east area the total seismic moment found from the body wave modelling is 7 7 1026 dyne cm in good agreement with geodetic and surface wave studies

origin of the hydrocarbon gases carbon dioxide and hydrogen sulfide in dodan field se turkey abstract gas occurrences consisting of carbon dioxide co 2 hydrogen sulfide h 2 s and hydrocarbon hc gases and oil within the dodan field in southeastern turkey are located in cretaceous carbonate reservoir rocks in the garzan and mardin formations the aim of this study was to determine gas composition and to define the origin of gases in dodan field for this purpose gas samples were analyzed for their molecular and isotopic composition the isotopic composition of co 2 with values of 1 5 and 2 8 suggested abiogenic origin from limestone 34 s values of h 2 s ranged from 11 9 to 13 4 h 2 s is most likely formed from thermochemical sulfate reduction tsr and bacterial sulfate reduction bsr within the bakuk formation the bakuk formation is composed of a dolomite dominated carbonate succession also containing anhydrite tsr may occur within an evaporitic environment at temperatures of approximately 120 145 c basin modeling revealed that these temperatures were reached within the bakuk formation at 10 ma furthermore sulfate reducing bacteria were found in oil water phase samples from dodan field as a result the h 2 s in dodan field can be considered to have formed by bsr and tsr as indicated by their isotopic composition hc gases are of thermogenic origin and were generated within the upper permian kas and gomaniibrik formations as indicated by the heavier isotopic composition of methane and ethane hc gases were later altered by tsr based on our results the dodan gas field may have formed as a result of the interaction of the following processes during the last 7 8 ma 1 thermogenic gas generation in permian source rocks 2 the formation of thrust faults 3 the lateral up dip migration of hc gases due to thrust faults from the kas formation into the bakuk formation 4 the formation of h 2 s and co 2 by tsr within the bakuk formation 5 the vertical migration of gases into reservoirs through the thrust fault and 6 lateral up dip migration within reservoir rocks toward the dodan structure

the influence of bedrock derived acidity in the development of surface and underground karst evidence from the precambrian carbonates of semi arid northeastern brazil very extensive cave systems are developed in precambrian una group carbonates in the campo formoso area eastern brazil in contrast the area is largely devoid of significant surface karst landforms as would be expected given its semi arid climate the caves in the area display many morphological features characteristic of deep seated hypogenic caves such as lack of relationship with the surface ramiform network pattern abrupt variations of passage cross sections and absence of fluvial sediments but do not show evidence of vertical passages marking the ascending path of acidic water nor present extensive gypsum or acid clay mineral deposits hydrochemical analyses of present day ground water indicate that oxidation of bedrock sulphide is an active process and sulphuric acid may be the main agent driving carbonate dissolution in the area a shallow mode of speleogenesis is thus proposed in which sulphuric acid produced through the oxidation of sulphide beds within the carbonates controls cave initiation and development moreover the geological situation of the area in an ancient stable passive margin precludes the possibility of deep seated sources of acidity under dry climate due to the absence of recharge solutional landforms will be largely subdued in the surface hypogenic processes if present are likely to predominate producing a landscape characterized by a marked disparity in the comparative degree of development between surface and underground landforms rates of karst landform development have traditionally been analysed through a climatic perspective runoff being the main controlling factor in promoting karst development this view needs to be reassessed in the light of the growing awareness of the importance of climate independent processes related to hypogenic sources of acidity copyright 2003 john wiley sons ltd

phantom earthquakes and triggered aseismic creep vertical partitioning of strain during earthquake sequences in iran 1 we present evidence for significant aseismic fault slip at shallow depth above a pair of mainshock aftershock sequences in the zagros mountains of iran the two mw 5 9 earthquakes are each spanned by high quality geodetic imagery and have well recorded sequences of aftershocks that occurred beneath a salt decollement earlier studies of the geodetic data inferred that the mainshocks were located above the decollement requiring a 10 km spatial separation between aftershock cluster and earthquake centroid we find that the geodetic data simultaneously allow two slip sources of similar magnitude one within the basement collocated with aftershocks and one shallow source also equivalent to mw 6 responsible for the primary signal apparent in the geodetic imagery should this phenomenon be widespread in the zagros it would partially explain a previously noted discrepancy between observed seismic moment release in the zagros and current convergence rates between the arabian and eurasian plates

crater lake and post eruption hydrothermal activity el chichon volcano mexico abstract explosive eruptions of volcan el chichon in chiapas mexico on march 28 and april 3 4 1982 removed 0 2 km3 of rock to form a 1 km wide 300 m deep summit crater by late april 1982 a lake had begun to form on the crater floor and by november 1982 it attained a maximum surface area of 1 4 105 m2 and a volume of 5 106 m3 accumulation of 4 5 m of rainfall between july and october 1982 largely formed the lake in january 1983 temperatures of fumaroles on the crater floor and lower crater walls ranged from 98 to 115 c by october 1983 the maximum temperature of fumarole emissions was 99 c in january 1983 fumarole gas emissions were greater than 99 vol h2o with traces of co2 so2 and h2s the water of the lake was a hot t 52 58 c acidic ph 0 5 dilute solution 34 046 mg l 1 dissolved solids cl s 20 5 sediment from the lake contains the same silicate minerals as the rocks of the 1982 pyroclastic deposits together with less than 1 of elemental sulfur the composition and temperature of the lake water is attributed to 1 solution of fumarole emissions 2 reaction of lake water with hot rocks beneath the lake level 3 sediments washed into the lake from the crater walls 4 hydrothermal fluids leaching sediments and formational waters in sedimentary rocks of the basement 5 evaporation and 6 precipitation

africa eurasia kinematics main constraints and uncertainties abstract it is widely believed that the africa eurasian relative motion in the mediterranean region is oriented se nw to s n this result has been deduced from the analysis of north atlantic kinematic data by assuming that eurasia is a unique coherent plate from the north atlantic ridges to the pacific trenches however this assumption cannot easily account for the not negligible tectonic activity inside and around western europe rhine graben system pyrenees and off shore portugal this paper shows that if one allows western europe to move independently from main eurasia the kinematic indicators in the north atlantic do not exclude other kinematic solutions which are significantly different from those currently accepted in particular it is demonstrated that a ssw nne to sw ne trending africa eurasia convergence beside allowing plausible explanations of major post tortonian deformation events in the central mediterranean region can fit north atlantic data within experimental errors

contemporary tectonics of the himalayan frontal fault system folds blind thrusts and the 1905 kangra earthquake the sub himalayan fold thrust belt consists of deformed late cenozoic and older deposits south of the main boundary thrust mbt in pakistan east of the indus river the sub himalaya comprises the potwar plateau and the salt range which is thrust southward over the jhelum river floodplain along the salt range thrust although an estimated 9 14 mm a 1 shortening has been taken up on the salt range thrust during the last 2 ma the range front scarp does not show signs of recent faulting shortening may be shifting southward to the lilla overpressured anticline which rises from the jhelum floodplain as a fault propagation fold farther east shortening is partitioned among several anticlines underlain by foreland and hinterland dipping blind thrusts southeast of the main deformation zone the pabbi hills overpressured anticline is best explained as a fault propagation fold throughout the potwar plateau and salt range thrusts and folds rise from a basal decollement horizon in eocambrian evaporites the pakistani part of the decollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths in india and nepal the sub himalaya is narrower reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland the southern boundary of the sub himalaya is the himalayan front fault discontinuous because part of the shortening is expressed at the surface by folding broad alluvial synclinal valleys dun valleys are bounded on the south by rising barrier anticlines of siwalik molasse the 1905 kangra earthquake m8 produced uplift on the mohand anticline and the dehra dun valley suggesting that this earthquake occurred on a decollement horizon above basement downdip from the fold if so the kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold

holocene coastal deformation in simeulue and nias indonesia west of sumatra indonesia the islands of nias and simeulue as well as their smaller neighbours display elevated coral reefs and abandoned intertidal platforms faunas from three sections indicate a late cainozoic age for the reefs unaltered mollusc shells from nineteen fossil platforms were dated by first order 14c analysis the localities sampled were 0 5 to 3 5 m above normal high tide apart from one non finite result the ages ranged between modern 300 yrs and 5800 300 yrs b p the resulting average uplift rates are 0 3 1 0 mm yr no simple relationship between sample age and height is apparent but the bulk of the ages fall within three periods 0 800 yrs b p 2000 3400 yrs b p and 4500 5800 yrs b p suggesting that episodes of uplift were separated by periods of quiescence and that they were seismic in origin the pattern of deposition at the key section on nias supports this inference evidence of recent subsidence in eastern simeulue shows that uplift was locally accompanied by tilting the pattern and rate of movement are consistent with the position of the islands on the outer arc ridge of the sunda arc and with the long term uplift rates derived from palaeontological sources the inverse darwin coral reef model proposed here for the development of reefs on the flanks of rising neogene cores may also be applicable elsewhere

preliminary results of a paleoseismological analysis along the sahel fault algeria new evidence for historical seismic events abstract the 60 km long sahel ridge west of algiers tell atlas north algeria is considered as an ene wsw fault propagation fold running along the mediterranean coast and associated with a north west dipping thrust its proximity with algiers makes this structure a potential source of destructive earthquakes that could hit the capital city as occurred in 1365 ad and 1716 ad the first paleoseismologic investigation on the sahel ridge was conducted in order to detect paleo ruptures related to active faulting and to date them from the first investigations in the area a first trench was excavated across bending moment normal faults induced by flexural slip folding in the hanging wall of the sahel anticline thrust ramp paleoseismological analyses recognize eight rupture events affecting colluvial deposits 14c dating indicates that these events are very young six of them being younger than 778 ad the first sedimentary record indicates two ruptures before 1211 ad i e older than the first historical earthquake documented in the region three events have age ranges compatible with the 1365 1673 and 1716 algiers earthquakes whereas three other ones depict very recent ages i e younger than 1700 ad potential of these secondary extrados faults for determining paleoseismic events and thrust behaviour is discussed

field and teleseismic observations of the 1981 golbaf sirch earthquakes in se iran summary in 1981 june and july two large earthquakes occurred on the gowk fault system in south east iran both earthquakes were associated with surface faulting showing a combination of reverse and right lateral strike slip motion on parallel adjacent faults striking north south and dipping both east and west such motion can be seen to have occurred in the recent past and is responsible for the formation of elongated alluvium filled depressions in the footwall region common to both the east and west dipping faults the earthquake of june 11 involved motion along about 15 km of the gowk fault system with a moment of about 1 0 1026 dyne cm the earthquake of july 28 was larger and occurred farther north with movement along at least 65km of the gowk fault system and a moment of about 7 1026 dyne cm surface faulting in both earthquakes was complex and spread over several kilometres width on en echelon fault segments as well as on faults dipping both east and west the long period wwssn seismograms of these two mainshocks are unusually complicated and clearly made up of several individual subevents sensible interpretation of these waveforms without guidance from the surface faulting and the long period sro moment tensor inversion of dziewonski woodhouse would be impossible however a combination of these three data sources allows a geologically plausible interpretation of the rupture processes in these earthquakes to be made although the faulting in both mainshocks was on the same large scale feature the gowk fault the rupture zones of the two earthquakes did not apparently overlap and were separated by a gap of 5 km along strike in which both coseismic and recent geological displacements are very small rupture in both mainshocks appears to have nucleated near this gap and to have propagated away from it other such gaps are visible along the irregular displacement of the northern fault break and may have been the nucleation positions for individual subevents of the july 28 earthquake recognition of such nucleation sites is of obvious importance to earthquake prediction efforts

geomorphology and surface tilting in an active extensional basin sw montana usa the valley and alluvial cone of the antecedent madison river in the missouri flats area of sw montana lie in a half graben bounded by a prominent prehistoric fault scarp footwall sourced alluvial fans and fans derived from a major transfer zone have prograded onto the oldest of a prominent suite of three paired terraces of holocene age which bound the modern braided floodplain of the river the terraces have been cut into the pleistocene alluvial cone and are cut by the prehistoric fault scarp levelling studies on the terrace surfaces in the hangingwall reveal that movement on the fault has caused surface tilting erosion and deposition a suite of terraces present in the footwall of the fault shows backtihing consistent with footwall uplift having occurred

microbial contributions to cave formation new insights into sulfuric acid speleogenesis the sulfuric acid speleogenesis sas model was introduced in the early 1970s from observations of lower kane cave wyoming and was proposed as a cave enlargement process due to primarily h 2 s autoxidation to sulfuric acid and subaerial replacement of carbonate by gypsum here we present a reexamination of the sas type locality in which we make use of uniquely applied geochemical and microbiological methods little h 2 s escapes to the cave atmosphere or is lost by abiotic autoxidation and instead the primary h 2 s loss mechanism is by subaqueous sulfur oxidizing bacterial communities that consume h 2 s filamentous epsilonproteobacteria and gammaproteobacteria characterized by fluorescence in situ hybridization colonize carbonate surfaces and generate sulfuric acid as a metabolic byproduct the bacteria focus carbonate dissolution by locally depressing ph compared to bulk cave waters near equilibrium or slightly supersaturated with calcite these findings show that sas occurs in subaqueous environments and potentially at much greater phreatic depths in carbonate aquifers thereby offering new insights into the microbial roles in subsurface karstification

a blind thrust and overlying folding earthquake of the 2016 mw 6 0 hutubi earthquake in the northern tien shan fold and thrust belts china

earthquake induced flooding and paleoseismicity of the el asnam algeria fault related fold late quaternary activity of the el asnam thrust fault responsible for the october 10 1980 ms 7 3 earthquake and 36 km coseismic faulting is explored through diverse paleoseismological field methods we trenched through the main and secondary 1980 coseismic scarps made an analysis of earthquake induced flood deposits conducted a geomorphic study of leveling profiles and offset geological units across thrust and normal scarps and considered the geomorphology of the active fold twenty five radiocarbon ages from colluvial and alluvial deposits along with conventional fossils and artefacts dating of geological units show the timing of successive net vertical displacements on the thrust related fold and bending moment faults previous work showed that eight pre 1980 earthquakes occurred in clusters during the late holocene cumulative net vertical slip that amounts to 3 times the 1980 displacement is observed on multiple thrust fault scarps and offsets of geological units on bending moment faults maximum cumulative vertical displacements which are visible in different zones along the fault segments can reach 10 to 25 times the 1980 coseismic displacements the late quaternary uplift rate on the el asnam fault is 0 6 mm yr and taking into account slip variation along the fault this rate may range between 0 25 1 6 mm yr from which we obtain a shortening rate of 0 17 1 2 mm yr because the tell atlas mountains exhibit comparable seismogenic fault related folds with parallel and sequential structures of active faults a total average shortening rate of 2 05 mm yr during the late quaternary represents part of the convergence accommodated along the africa eurasia plate boundary

representative styles of deformation along the chelungpu fault from the 1999 chi chi taiwan earthquake geomorphic characteristics and responses of man made structures the chi chi earthquake provides dramatic evidence of the damaging effects of surface ground deformation to buildings lifelines and other facilities much of the building damage is associated with surface faulting and folding along the chelungpu thrust fault our detailed surveying at representative sites along the fault shows that the rupture commonly is a relatively simple 1 to 4 m high scarp with minor hanging wall deformation and localized but severe uplift folding and graben formation along the scarp crest for individual scarps the width of deformation is about 10 to 20 times the net vertical displacement distributed secondary faulting and folding on the hanging wall occurred as much as 350 m from the primary fault near the northern end of the rupture growth of a pre existing 1 km wide late quaternary anticline produced severe ground rupture along multiple thrusts and backthrusts but only minor tilting between fault strands the pattern of building damage coincides with the pattern of geologic deformation with severe damage along large fault scarps and lesser but still significant damage attributable to distributed secondary surface deformation on the hanging wall rupture related building damage on the footwall occurred next to the prerupture fault trace where the hanging wall bulldozed onto the footwall the width of this damage zone is related to the local horizontal shortening along the fault and generally is less than 10 m building zonation along reverse faults should account for this pattern of surface deformation in addition buildings with massive foundations locally influenced the style and location of near surface deformation producing variations in fault strike or accentuated secondary deformation on the hanging wall manuscript received 15 january 2001

fate of sulfide in the frasassi cave system and implications for sulfuric acid speleogenesis abstract the oxidation of hydrogen sulfide h 2 s has led to the formation of some of the world s largest caves through a process known as sulfuric acid speleogenesis sas here we present a multi year study of the large sulfidic and actively forming frasassi cave system italy we show that despite the presence of abundant sulfide oxidizing biofilms in frasassi streams h 2 s g degassing to the cave atmosphere was the major sink for dissolved sulfide degassing rates ranged from 0 9 to 80 mol m 2 s 1 whereas microbial oxidation rates were between 0 15 and 2 0 mol m 2 s 1 furthermore microsensor measurements showed that sulfuric acid is not a major end product of microbial sulfide oxidation in the streams our results suggest that subaerial sas will be important for karstification and more important than subaqueous sas wherever ground waters with high sulfide concentrations emerge as flowing streams in contact with cave air

active folding in the algerian earthquake of 10 october 1980 a fold controlling the form of the local topography near el asnam algeria increased in amplitude at the time of the earthquake of 10 october 1980 the deformation occurred rapidly in an elastic brittle manner and not in the gradual ductile fashion in which folds are normally thought to develop

effects of water erosion on the redistribution of soil organic carbon in the hilly red soil region of southern china abstract water erosion processes can significantly affect the delivery and distribution patterns of soil organic carbon soc within the landscape while many studies focus on the erosion processes and runoff transport of soc little attention has been paid to the on site redistribution and vertical transport of soc this study characterizes soc erosion dynamics including infiltration associated movement and discusses the effects of rainfall intensity and slope position on soc transport within the hilly red soil region of southern china the results show that soc loss was likely due to sediment transport rather than runoff the eroded soc was not significantly enriched which may be due to the soil properties and the type of rainfall event the initial soc concentration affected the enrichment ratio of eroded soc in the sediment on site horizontal redistribution occurred regardless of rainfall intensity whereas the soc transport trends varied with rainfall intensity and slope positions this demonstrates that soil preservation could reduce soc loss and thus influence the global carbon cycle

earthquake hazards of active blind thrust faults under the central los angeles basin california we document several blind thrust faults under the los angeles basin that if active and seismogenic are capable of generating large earthquakes m 6 3 to 7 3 pliocene to quaternary growth folds imaged in seismic reflection profiles record the existence size and slip rates of these blind faults the growth structures have shapes characteristic of fault bend folds above blind thrusts as demonstrated by balanced kinematic models geologic cross sections and axial surface maps we interpret the compton los alamitos trend as a growth fold above the compton ramp which extends along strike from west los angeles to at least the santa ana river the compton thrust is part of a larger fault system including a decollement and ramps beneath the elysian park and palos verdes trends the cienegas and coyote hills growth folds overlie additional blind thrusts in the elysian park trend that are not closely linked to the compton ramp analysis of folded pliocene to quaternary strata yields slip rates of 1 4 0 4 mm yr on the compton thrust and 1 7 0 4 mm yr on a ramp beneath the elysian park trend assuming that slip is released in large earthquakes we estimate magnitudes of 6 3 to 6 8 for earthquakes on individual ramp segments based on geometric segment sizes derived from axial surface maps multiple segment ruptures could yield larger earthquakes m 6 9 to 7 3 relations among magnitude coseismic displacement and slip rate yield an average recurrence interval of 380 years for single segment earthquakes and a range of 400 to 1300 years for multiple segment events if these newly documented blind thrust faults are active they will contribute substantially to the seismic hazards in los angeles because of their locations directly beneath the metropolitan area

fault displacement gradient folds and the structure at lost hills california u s a abstract geometric models of fault propagation folds require that the underlying fault tip propagate upward across layering however related folds can be generated if the tip remains stationary or even moves back along the ramp as a pre existing fault is reactivated fault propagation folds detachment folds as well as those produced when there is no propagation are generated by a displacement gradient along the underlying fault and as a general class can be called fault displacement gradient folds new geometric equations are derived which relate fold shape to displacement gradient and fault propagation folds are a special case of these more general equations growth sequences associated with these structures have been used to distinguish fault propagation folds from fault bend folds when the underlying structure is obscured a displacement gradient fold in which the fault tip retreats back down the ramp generates a growth sequence that in some cases could be confused with that of a fault bend fold the structure at lost hills in the san joaquin valley of california u s a has been interpreted as a fault bend fold but it may be a displacement gradient fold which formed as a pre existing fault was reactivated during a pliocene change in plate motion

hypogenic contribution to speleogenesis in a predominant epigenic karst system a case study from the venetian alps italy abstract buso della rana and buso della pisatela are two karstic caves located in north east italy they are part of the same karst system and are developed in the castelgomberto calcarenitic marine sediments which were deposited in a shallow caribbean type sea during the eocene the buso della rana pisatela system developed mostly at the contact between the castelgomberto calcarenite and underlying volcanic rocks the system of caves is 37 km long and has only three entrances two of which are semi artificial the overlying karst plateau is not directly connected to the buso della rana pisatela system and with the exception of one deep abyss exhibits a rather poorly developed karst this is unexpected considering the presence at depth of such a large and long cave gypsum caso 4 2h 2 o has locally been observed on the walls of the buso della pisatela cave energy dispersive x ray spectroscopy eds performed with a scanning electron microscope sem reveals the presence of sulfur bearing minerals within the host rock gypsum was formed by oxidation of these minerals as indicated by negative 34 s values the oxidation of sulfide minerals forms a sulfuric acid solution that dissolves the castelgomberto calcarenite and once it is oversaturated in calcium precipitates as gypsum the lack of well developed karst on top of the plateau and the analyses suggest that the formation mechanisms for the buso della rana pisatela system differ from classical epigenic speleogenesis the pyrite effect has been recognized in other caves and described in literature in our case pyrite is responsible of two hypo speleogenetic processes i the dissolution of a portion of the host rock and ii the enlargement of the karst voids as a consequence of the haloclastic effect

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

carbon flux and landscape evolution in epigenic karst aquifers modeled from geochemical mass balance this paper considers the contributions of epigenic karst processes as a major element of the carbon cycle and a significant agent of landscape evolution geochemical models developed from monitoring data and water samples are used to estimate the variation and magnitude of dissolved inorganic carbon dic flux in karst landscapes at several scales from local to global at the local scale the cumberland river watershed of southeast kentucky these geochemical models are also used to evaluate the potential role of sulfur in the production of dic and to compute an estimated rate of landscape erosion geochemical modeling using ionic species and modeled discharge reveal a variable rate of dic flux driven by large fluctuations in calcite saturation and discharge ratios of reaction products and principal component analyses pca suggest that some bedrock dissolution may be driven by the oxidation of reduced sulfur derived from brines entrained into the karst aquifers over the 3730 km2 of carbonate exposure in the cumberland river 25 8 62 4 gg yr of carbon dioxide co2 is conveyed from the atmosphere through the dissolution of carbonate at the global scale this translates to 123 296 tg yr of co2 delivered by karst processes into the aqueous system the bedrock portion of dic equates to a flux of 32 6 2 6 m3 35 2 2 8 m3 of bedrock during the period of study of which 29 was dolomite this translates to a landscape erosion rate of 13 1 17 9 mm ka in the 3 45 4 32 km2 of carbonate exposure in the studied watershed based upon 16 km of cave survey data spanning a vertical range of 72 to 75 m above base level this suggests that cave development in the watershed spans the plio pleistocene using the modeled erosion rates the ages of cave levels 4 03 5 71 3 08 4 56 1 57 2 43 1 01 1 67 0 45 0 91 and 0 45 ma are in good agreement with regional studies of plio pleistocene landscape evolution in the appalachian lowland plateaus copyright 2015 john wiley sons ltd

geochemistry of the volcano hydrothermal system of el chichon volcano chiapas mexico the 1982 eruption of el chichon volcano ejected more than 1 km3 of anhydrite bearing trachyandesite pyroclastic material to form a new 1 km wide and 300 m deep crater and uncovered the upper 500 m of an active volcano hydrothermal system instead of the weak boiling point temperature fumaroles of the former lava dome a vigorously boiling crater spring now discharges 20 kg s of cl rich 15 000 mg kg and sulphur poor 200 mg kg of so4 almost neutral ph up to 6 7 water with an isotopic composition close to that of subduction type magmatic water d 15 18o 6 5 this spring as well as numerous cl free boiling springs discharging a mixture of meteoric water with fumarolic condensates feed the crater lake which compared with values in 1983 is now much more diluted 3000 mg kg of cl vs 24 030 mg kg less acidic ph 2 6 vs 0 56 and contains much lower amounts of s 200 mg kg of so4 vs 3550 mg kg with 34s 0 5 4 2 17 in 1983 agua caliente thermal waters on the southeast slope of the volcano have an outflow rate of approximately 100 kg s of 71 c na ca cl water and are five times more concentrated than before the eruption b r molina unpublished data relative n2 ar and he gas concentrations suggest extensional tectonics for the el chichon volcanic centre the 3he 4he and 4he 20ne ratios in gases from the crater fumaroles 7 3ra 2560 and agua caliente hot springs 5 3ra 44 indicate a strong magmatic contribution however relative concentrations of reactive species are typical of equilibrium in a two phase boiling aquifer sulphur and c isotopic data indicate highly reducing conditions within the system probably associated with the presence of buried vegetation resulting from the 1982 eruption all cl rich waters at el chichon have a common source this water has the appearence of a partially matured magmatic fluid condensed magmatic vapour neutralized by interaction with fresh volcaniclastic deposits and depleted in s due to anhydrite precipitation shallow ground waters emerging around the volcano from the thick cover of fresh pumice deposits red waters are ca so4 rich and have a negative oxygen isotopic shift probably due to ongoing formation of clay at low temperatures

distinction between epigenic and hypogenic maze caves abstract certain caves formed by dissolution of bedrock have maze patterns composed of closed loops in which many intersecting fractures or pores have enlarged simultaneously their origin can be epigenic by shallow circulation of meteoric groundwater or hypogenic by rising groundwater or production of deep seated solutional aggressiveness epigenic mazes form by diffuse infiltration through a permeable insoluble caprock or by floodwater supplied by sinking streams most hypogenic caves involve deep sources of aggressiveness transverse hypogenic cave origin is a recently proposed concept in which groundwater of mainly meteoric origin rises across strata in the distal portions of large flow systems to form mazes in soluble rock sandwiched between permeable but insoluble strata the distinction between maze types is debated and is usually based on examination of diagnostic cave features and relation of caves to their regional setting in this paper the principles of mass transfer are applied to clarify the limits of each model to show how cave origin is related to groundwater discharge dissolution rate and time the results show that diffuse infiltration and floodwater can each form maze caves at geologically feasible rates typically within 500 ka transverse hypogenic mazes in limestone to enlarge significantly within 1 ma require an unusually high permeability of the non carbonate beds generally 10 4 cm s large discharge and calcite saturation no greater than 90 which is rare in deep diffuse flow in sedimentary rocks deep sources of aggressiveness are usually required the origin of caves by transverse hypogenic flow is much more favorable in evaporite rocks than in carbonate rocks

present day kinematics of the plate boundary zone between africa and europe from the azores to the aegean anticlockwise rotation of africa relative to europe around an euler pole in the eastern atlantic causes plate convergence in the central mediterranean towards n20 w at rate considered a priori to be 5 10 mm yr 1 however previous summaries of the present day deformation sense in the central mediterranean are inconsistent with observations in southern italy recent investigations of italy and adjacent parts of north africa enable local deformation sense observed to be reconciled with sense predicted from relative plate motions suggested angular velocity of the african plate relative to europe is 0 07 myr 1 around a pole near 21 n 21 w this predicts 2 6 mm yr 1 maximum extension rate towards n64 e near the azores consistent with the minimum local accretion of new oceanic crust in the past few millions of years and 4 3 mm yr 1 plate convergence towards n20 w in the central mediterranean at 13 e further east the northern margin of the african plate can be regarded as the gargano seismic zone in the central adriatic sea the northern adriatic sea is a microplate rotating anticlockwise relative to europe at 0 3 myr 1 around a pole in northwestern italy causing northeastward shortening in yugoslavia and up to 4 mm yr 1 extension in central and northern italy the african plate is deforming internally in tunisia and northern libya extending obliquely in direction e10 s at rate up to 5 5 mm yr 1 the resultant velocity relative to europe in the ionian and southern adriatic seas 5 mm yr 1 towards n50 e explains the observed relative velocity across southern italy kinematic consistency requires present day shortening rate east of calabria associated with subduction on the tyrrhenian sea benioff zone and tyrrhenian sea extension rate to be both zero or equal to within 1 mm yr 1

deformations associated with the el asnam earthquake of 10 october 1980 geodetic determination of vertical and horizontal movements the resurvey of both a geodetic network and a leveling net was carried out in june 1981 8 months after the ms 7 3 el asnam earthquake of 10 october 1980 previous seismological and neotectonic studies ouyed et al 1981 yielding et al 1981 indicate that this event results from a northeast trending overthrust complex fault of about 40 km length which shows at least three principal segments with slightly different directions vertical movements evaluated by means of a trigonometric leveling method show an uplift of the northwestern side of the thrust fault of about 5 m and a depression of the southeastern edge of about 1 m these movements are progressively attenuated away from the fault trace horizontal movements have been evaluated by a classical first order triangulation method the resulting mean strain tensors calculated for different triangles of the geodetic network indicate a shortening of about 2 50 m which is consistent with the se nw direction of compression determined from neotectonic evaluations and focal mechanisms dislocation models are used to explain and discuss the observed deformations in light of the seismological data and observed ground breakages five segments are required to explain both horizontal and vertical deformations the magnitude of vertical displacements about 6 m at the junction between the southwest and the central segments of the fault argues for the breaking of this area during the main shock and for a slip vector of about 8 m at least in the central segment

chronology and development of the 1980 earthquake at el asnam algeria a postscript abstract radiocarbon dating has now confirmed the alluvial chronology that was used in assessing the extent of deformation during the 1980 el asnam earthquake it also supports the suggestion that earlier movements were related to a hypocentre further to the east