structural outline of a tertiary basement cored uplift inversion structure in western spitsbergen svalbard kinematics and controlling factors the tertiary fold and thrust belt of spitsbergen can be divided into a western basement involved fold thrust stack and a central eastern foreland fold and thrust belt in western nordenskiold land the first order structure is an ene verging basement cored fold and fault complex involving paleozoic to tertiary strata the northern part reveals an upright monocline geometry of east tilted sedimentary cover units with associated layer parallel to low angle thrusts and folds these structures consist of two populations oriented both parallel to nnw sse and oblique to wnw ese the general structural trend of the fold complex in the central and southern parts of west nordenskiold land the fold complex involves tilted basement cut by steep transverse faults and late normal faults the east limb of the fold complex displays repeated basement and paleozoic strata orustdalen formation in its core and mesozoic triassic strata influenced by map scale chevron folds and two decollement levels all located above an eastward rotated major detachment fault the kleivdalen thrust establishing fold fault relations includes a three stage structural history in the fold complex as follows 1 a phase of early nne ssw shortening associated with wnw ese folds and thrusts and 2 a dominant ene wsw basement involved shortening leading to the first order nnw sse striking fold complex followed by 3 approximately e w extension the resulting structures and structural variability along strike as well as across strike appear to have been controlled by basement and carboniferous basin structures underlying the permian cretaceous platform strata restored stratigraphic sections based on thrust repetition of basement and cover e g within a type section of the carboniferous orustdalen formation support such an interpretation a tentative inversion tectonic model reproduces the position s of local and major thrust ramps and associated folds as a result of inheritance from carboniferous basin structures

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

an unusual triangle zone in the external northern alpine foreland switzerland structural inheritance kinematics and implications for the development of the adjacent jura fold and thrust belt abstract triangle zones represent typical structural elements of thin skinned foreland fold and thrust belts here we report the results of an in depth structural analysis of a rather unusual triangle zone at the front of the easternmost jura fold and thrust belt in the otherwise only very mildly deformed alpine foreland of northern switzerland the investigation is based on the interpretation of recently reprocessed and depth migrated 2d reflection seismic sections classical bed length and area cross section balancing methods were used to validate the interpretation and unravel the tectonic evolution of the triangle zone according to our interpretation the analyzed triangle zone formed along the baden irchel herdern lineament bih lineament a regional paleozoic normal fault that shows evidence of cenozoic reactivation the triangle zone is composed of one major foreland directed thrust rooting in triassic evaporites and a back thrust splaying from it in the middle jurassic opalinus clay pointing to the importance of secondary detachments steeply dipping secondary reverse faults next to the triangle zone suggest reactivation of pre existing normal faults the formation of the thrust triangle is considered to relate to thin skinned foreland deformation in late miocene time strain estimations of the thrust triangle along strike show a laterally very uniform amount of shortening which is in contrast to the southward adjacent jura fold and thrust belt we interpret this constant shortening to represent the maximum contractional strain attainable by the specific geometry of the bih triangle zone at this point the complex structure became mechanically ineffective and further shortening led to the formation of new contractional structures in its hinterland this kinematic hypothesis suggests an early stage formation of the bih triangle zone followed by back stepping of the deformation front as such it challenges the classical view of a purely forward breaking sequence for the jura fold and thrust belt in the northwestern foreland of the alps

seismicity patterns in the himalayan plate boundary and identification of the areas of high seismic potential abstract space time distribution of earthquakes along the himalayan plate boundary has been investigated with a view to discerning fluctuations in seismicity rates associated with great earthquakes the possibilities of epicentre migration and gaps in seismic activity data from 1800 to 1976 were considered this study shows that all great earthquakes m 8 0 were preceded by seismically quiescent periods of at least 19 years furthermore earthquake quiescence has also been recognised to follow the great earthquakes three possible trends of migration of epicentres of great earthquakes have been recognised 1 1 the first trend starts from the 1905 kangra earthquake the epicentres of subsequent earthquakes migrating eastwards along the plate boundary 2 2 the second trend of migration starts from the great nepal earthquake of 1833 associated with eastward migration 3 3 the third trend commences from the great assam earthquake of 1897 and shows a westward migration of earthquake epicentres the middle section of the himalayan convergent plate boundary 80 e to 90 e in general displays a relatively low level of seismicity as compared to the adjacent sections a remarkable decrease in seismicity following the year 1970 has been observed along a section of the himalaya which lies to the east of the rupture zone of the great 1905 kangra earthquake since 1970 the seismicity rate has also dropped in the region lying in between the rupture zones of the great assam earthquakes of 1897 and 1950 as has earlier been reported by khattri and wyss 1978 such decreases in the level of seismicity along active plate boundaries have been demonstrated to be indicative of building up of stresses leading to future great earthquakes mogi 1969 mccann et al 1979

the jal az zor escarpment as a product of complex duplex folding and strike slip tectonics a new study in kuwait northeastern arabian peninsula abstract the origin of jal az zor escarpment has been equivocal due to limited exposure and subsurface data the escarpment was assumed to be a result of differential weathering and erosion most recently mapping of basement lineaments suggested a deep fault system as a most likely cause the aim of this article is to use shallow seismic data acquired across various locations along the escarpment to investigate the underlying geology structural elements and link these features to surface observations to understand the near subsurface geology post stack time processing was applied to 2d seismic data acquired recently in the area the objective was to focus on the shallow intervals represented by the rus dammam and kuwait formations the analyses revealed a train of tight concentric folds that increase in stage development towards the escarpment in the dammam formation the shallower kuwait formation shows early stages of fault propagation folding as a result of the kuwait arch uplift towards the south of the escarpment we suggest that friction along the dammam formation upper contact detachment planes increased towards the south thus promoting the propagation of the fold reaching the surface resulting in the jal az zor escarpment that we see today structural kinematic analysis suggests that the jal az zor escarpment is also a principal displacement zone pdz that is dominated by dextral strike slip motion and exhibits a series of restraining bends positive flower structures and a horsetail splay 2d structural restoration and balancing suggest a total shortening magnitude of approximately 6 25 km considering the arabian and eurasian plates velocity vectors along with the relatively large amount of shortening this deformation initiated during the early pleistocene calabrian the presence of tight concentric and fault propagation folds combined with dextral strike kinematics introduce new complexities into the structural styles and assemblages of the area otherwise thought to follow the overall northern arabian peninsula tectonics

structural analysis and kinematic evolution of the inverted central south celtic sea basin abstract the central south celtic sea basin shows excellent examples of tectonics and sedimentation relationships as evidenced by detailed geological interpretation of a local grid of seismic profiles these relationships together with balanced restored geological cross sections and block diagrams have been used to unravel the post variscan evolution of this part of the celtic sea basin three sedimentary mega sequences separated by two erosional surfaces have been recognized overlying a deformed palaeozoic basement in this area 1 permo triassic jurassic syn rift mega sequence sedimentation of the lowest part of this succession is strongly controlled by extensional faults whereas the rest of the sequence indicates much less fault control lateral extent of these rocks is also controlled by the disposition of the palaeozoic basement which appears as an elevation in the pembrokeshire ridge area where no sedimentation occurs 2 cretaceous post rift mega sequence 3 tertiary post rift mega sequence the cretaceous and tertiary successions are more extensive than permo triassic jurassic sediments covering the central south celtic sea basin and the pembrokeshire ridge the structural framework displayed by the syn rift and post rift sequences is very different thus the general structure beneath the jurassic cretaceous late cimmerian unconformity consists of a wsw ene trending fault system and related folds this resulted from an extensional phase which led to a sub basin compartmentalization of the area and a subsequent inversional event which caused significant reverse movement along previous extensional structures early cretaceous erosion was responsible for an important and unequal denudation the timing of the switch between extension and inversion cannot be determined due to early cretaceous erosion overlying the jurassic cretaceous unconformity cretaceous sediments are slightly deformed by broad anticlines formed during early tertiary mainly as a result of tightening of previous folds the tertiary sequence shows a subhorizontal disposition responsible for the present day smooth bathymetric relief of the south celtic sea basin

intermediate depth earthquakes in a region of continental convergence south island new zealand it is rare to find earthquakes with depths greater than 30 km in continent continent collision zones because the mantle lithosphere is usually too hot to enable brittle failure however a handful of small intermediate depth earthquakes 30 97 km have been recorded in the continental collision region in central south island new zealand the earthquakes are not associated with subduction but all lie within or on the margins of thickened crust or uppermost mantle seismic high velocity anomalies the largest of the earthquakes has m l 4 0 corresponding to a rupture radius of between 100 and 800 m providing bounds on the upper limit to the rupture length over which brittle failure is taking place in the deep brittle plastic transition zone the earthquake sources may be controlled by large shear strain gradients associated with viscous deformation processes in addition to depressed geotherms

the permian to cretaceous structural evolution of the western approaches basin melville sub basin uk summary the tectonic sedimentary evolution of the western part of the western approaches basin melville sub basin was initiated during early permian times when synrift clastic sedimentation and volcanism commenced within an ene trending half graben this sequence thickened to the south and onlapped a high to the north during the permian an early nnw sse basin extension was accommodated on an array of ene wsw trending normal faults linked by nnw sse orientated transfer faults this was followed by a period of ene wsw extension along the basin axis when the normal and transfer faults of the previous faulting episode swapped roles this was possibly related to early rifting in the bay of biscay both sets of faults appear to be controlled to some extent by variscan thrusts and strike slip faults within the basement during the upper triassic the ridge in the north subsided allowing a thick sequence of salt to be deposited where there had previously been a topographic high during jurassic times sedimentation extended across the permian triassic half graben into the french sector this was followed by an episode of rifting and wrench deformation and inversion during which the permian to jurassic basin was domed and uplifted the cretaceous to tertiary sedimentation which followed probably resulted from postrift thermal subsidence related to cooling of the continental platform adjacent to the opening atlantic ocean steep normal and or strike slip faults data from the earliest part of this postrifting stage

revisiting the earthquake sources in the himalaya perspectives on past seismicity abstract the 2500 km long himalaya plate boundary experienced three great earthquakes during the past century but none of them generated any surface rupture the segments between the 1905 1934 and the 1897 1950 sources known as the central and assam seismic gaps respectively have long been considered holding potential for future great earthquakes this paper addresses two issues concerning earthquakes along the himalaya plate boundary one the absence of surface rupture associated with the great earthquakes vis a vis the purported large slip observed from paleoseismological investigations and two the current understanding of the status of the seismic gaps in the central himalaya and assam in view of the paleoseismological and historical data being gathered we suggest that the ruptures of earthquakes nucleating on the basal detachment are likely to be restricted by the crustal ramps and thus generate no surface ruptures whereas those originating on the faults within the wedges promote upward propagation of rupture and displacement as observed during the 2005 kashmir earthquake that showed a peak offset of 7 m the occasional reactivation of these thrust systems within the duplex zone may also be responsible for the observed temporal and spatial clustering of earthquakes in the himalaya observations presented in this paper suggest that the last major earthquake in the central himalaya occurred during ad 1119 1292 rather than in 1505 as suggested in some previous studies and thus the gap in the plate boundary events is real as for the northwestern himalaya seismically generated sedimentary features identified in the 1950 source region are generally younger than ad 1400 and evidence for older events is sketchy the 1897 shillong earthquake is not a decollement event and its predecessor is probably 1000 years old compared to the central himalaya the assam gap is a corridor of low seismicity between two tectonically independent seismogenic source zones that cannot be considered as a seismic gap in the conventional sense

mineralogy of three slightly palagonitized basaltic tephra samples from the summit of mauna kea hawaii certain palagonites from hawaii are considered to be among the best analogs for martian fines based upon similar spectral properties for this study three distinctly colored layers were sampled from slightly palagonitized basaltic tephra just below the summit of mauna kea at 4145 m elevation the mineralogy of size fractions of these samples was examined by diffuse reflectance visible and near ir and far ir spectroscopy optical microscopy x ray diffraction mossbauer spectroscopy magnetic analysis electron microprobe analysis empa and transmission and scanning electron microscopy for the 20 1000 m size fraction sample hwmk11 red is essentially completely oxidized and has a hematite ti hematite pigment dispersed throughout the silicate matrix the alteration is present throughout particle volumes and only a trace amount of glass is present no palagonitic rinds were detected in addition to ferric fe ti oxides other phases detected were plagioclase feldspar and a trace of olivine sample hwmk12 black has the lowest proportion of ferric bearing phases and is thus least weathered it consists mostly of unaltered glass with embedded plagioclase and minor amounts of pyroxene olivine and ti magnetite in some grains a thin palagonitic rind is visible indicating some surface alteration the mineralogy for sample hwmk13 yellow is the same as that for hwmk12 except that it has distinct well developed palagonitic rinds consisting of erionite and smectite for all samples the amount of glass and plagioclase decreases and the amount of smectite increases with decreasing particle size for size fractions 20 m for hwmk11 the amount of hematite is essentially constant and mica is present only in the coarse clay sized fraction smectites are low in structural fe for hwmk12 and hwmk13 the zeolite erionite is present along with smectites and nanophase ferric oxides np ox erionite abundance decreases and np ox abundance increases with decreasing particle size the smectite in both black and yellow samples contains some fe3 in octahedral layers there were only two mineral phases containing iron in the fine clay fraction namely smectites and iron oxides for hwmk11 relatively large iron oxide particles 0 1 to 0 4 m were dispersed on clay surfaces for hwmk12 and hwmk13 much finer np ox particles were present in lesser concentrations formation of the zeolite erionite is consistent with the arid climate zone where these samples were collected however transient hydrothermal processes that occurred during the eruption of mauna kea volcano under its permanent ice cap during the pleistocene may have resulted in minerals such as zeolites and smectites which may persist as relicts over a long period of time most of the iron released during weathering of basaltic tephra precipitated as poorly crystalline iron oxides and some of the fe has substituted for the octahedral cations in the structure of authigenic smectites the ti hematite in hwmk11 however is the result of high temperature oxidation of ti magnetite and exsolution from ironbearing silicate phases visible and near ir reflectivity spectra for the 20 m size fraction of hwmk11 is dominated by well crystalline ti hematite corresponding spectra for hwmk12 and hwmk13 whose ferric mineralogy is dominated by np ox particles are more similar to martian bright region spectra

earthquake frequency distribution and the mechanics of faulting the level of intraplate seismicity in japan generally shows a positive correlation with the density of quaternary faulting in southwest japan where intraplate seismicity is concentrated on land rates of seismic moment release m 0 are similar when calculated from either the 400 year historical record of seismicity or geologically determined slip rates of quaternary faults a data set of 18 earthquakes with seismic moments m0 ranging from 0 01 to 3 1027 dyn cm shows a relationship between rupture lengthl and m0 log m0 23 5 1 94 log l when seismic moment on each quaternary fault is assumed to occur in discrete events every t m0 m 0g years where m0 is estimated for a rupture extended over the entire fault length and m 0g is proportional to the slip rate of each quaternary fault the moment frequency distribution of earthquakes log n a b log m0 predicted from the geologic record is virtually identical to that seen with the 400 year record of seismicity in contrast if it is assumed that earthquakes on each fault occur according to the gutenberg richter relation we obtain poor agreement with the observed seismicity thus while regional seismicity satisfies the relation log n a b log m0 or equivalently log n a b log m where m is magnitude it appears that seismicity on individual faults does not this further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults

the relationship between the geometry of normal faults and that of the sedimentary layers in their hanging walls abstract we derive an analytical expression that relates the shape of a fault in cross section to the shape of the bedding horizons in its hanging wall block the expression assumes that the hanging wall deforms by simple shear and that the footwall remains undeformed throughout although this paper concentrates on normal faults the expression is equally valid and applicable to thrust faults the direction of simple shear in the hanging wall block is arbitrary and has a dramatic effect on the predicted fault or bedding geometry there is no reason to believe that the simple shear occurs on vertical planes as is commonly assumed in graphical approaches to this problem and ignoring the presence of inclined simple shear is likely to lead to considerable underestimates of the amount of extension across normal faults and in the amount of shortening across thrusts similar though more complicated expressions can be obtained when compaction within the hanging wall block is taken into account for a planar normal fault such compaction may result in the development of a hanging wall syncline

a systematic technique for the sequential restoration of salt structures abstract a method is described for the sequential restoration of cross sections in areas of salt tectonics where deformation is confined to the salt and higher layers the subsurface geometry evolves with time through the interaction of various processes sedimentation compaction isostatic adjustment thermal subsidence if present faulting and salt withdrawal diapirism the technique systematically calculates and removes the effects of each of these processes during specified time intervals defined by the interpreted horizons it makes no assumptions about salt kinematics and generally results in the area of the salt layer changing through time the method is described for restoration of extensional terranes but it is also suitable for areas of contractional salt tectonics with only minor modifications after converting an interpreted seismic profile to depth the top layer is stripped off and the underlying section is decompacted according to standard porosity depth functions a deep baseline unaffected by compaction or deformation is used to restore any isostatic compensation or thermal subsidence isostasy is calculated according to the airy model and differential sedimentary loading across a section is shown to be approximately balanced by changes in salt thickness so that the load is evenly distributed after these processes have been reversed the resulting geometry and the seismic data are used to create the sea floor template for structural restoration fault offsets are removed and the layers down to the top salt are restored to this template while the base salt remains fixed the resulting space between the restored top salt and the fixed base salt defines the restored salt geometry in addition the difference between the sea floor template and a fixed sea level provides a measure of the change in water depth ignoring eustatic changes in sea level the technique is applied to an interpreted seismic profile from the eastern green canyon ewing bank area of offshore louisiana the section is characterized by a variety of salt structures including salt rollers a diapiric massif a remnant salt sheet and a salt weld which are shown to have derived from an originally continuous salt sheet which has been modified by sedimentary loading early loading created vertical basin growth that was accommodated primarily by salt withdrawal and associated diapiric rise through the process of downbuilding once the salt weld formed continued sedimentation was accommodated by a lateral increase in basin size caused by down dip extension on listric growth faults

sandbox experiments of inverted listric and planar fault systems abstract the kinematic and geometric evolution of basement controlled inversion structures has been analyzed using a plane strain sandbox apparatus the results of two representative scaled analogue models comprising rigid listric and planar detachment faults that both have cut off angles of 60 to the horizontal are described in detail the hangingwall above these detachment geometries was constructed from alternate layers of sand and mica in order to simulate an anisotropic sedimentary sequence in both experiments initial shortening at the onset of inversion was accommodated by bulk strain this was followed by reactivation of the basal detachment together with the main basin controlling planar and listric faults which propagate upwards through the post rift sequence at approximately the same angle as the upper part of the detachment fault i e 60 reactivation of relatively steep intra basinal extensional faults within the cover was restricted to nucleation of reserve faults and thrusts in the region of the tips during approximately the first 10 to 15 contraction this resulted in gently dipping thrusts that propagated upwards through the post rift sequence to produce harpoon shaped structures later in the inversion phase after approximately 15 contraction backthrusts cut through and displaced the original antithetic extensional graben faults producing downward tapering wedge shaped structures at the margins of the basin although deformation in these experiments was limited to purely dip slip displacement the nature of the original extensional faults and their reactivated tip regions resulted in cross sectional geometries that have a marked resemblance to strike slip induced flower structures uplift was asymmetric and centred above the upper part of the main detachment above the listric fault but was more symmetrical and centred above the soling out point of the detachment in the case of the planar fault geometry the results of these experiments show distinct similarities to structures seen on seismic sections form the southern north sea and other inverted sedimentary basins

benefits and limitations of different 2d algorithms used in cross section restoration of inverted extensional faults application to physical experiments abstract in recent years 2d restoration techniques have been systematically used to restore cross sections through inverted basins the accuracy of these techniques and in particular which method better restores the inverted extensional faults to previous stages is uncertain and difficult to assess in natural examples to address this drawback the applicability of flexural slip and vertical oblique slip restoration techniques executed with section restoration software is tested through restoration of physical experiments of inverted extensional faults to their pre inversion stage the experiments chosen consist of simple listric and planar faults in which 1 the original state and the kinematic path followed by the rocks to reach the final state is known 2 the boundary conditions are known 3 erosion is absent and 4 the orientation of extension and compression vectors is equal comparing the restored sections with their corresponding actual pre inversion stage reveals that flexural slip is the best restoration method whereas the combination of different slip angles method gives the worst results the accuracy of these techniques depends to a great extent on the master fault geometry the coefficient of friction along it and the amount of inversion the best results are obtained for a physical model that consists of a listric fault with 60 dip at the top of the rigid footwall a shallow detachment low coefficient of friction along the fault and mild amount of inversion since the deformation mechanisms and the geometry of the inverted structures are non identical in physical experiments and in natural examples the results obtained in our study should be cautiously applied to cross sections across natural inverted basins

neogene basin inversion and recent slip rate distribution of the northern termination of the alhama de murcia fault eastern betic shear zone se spain the alhama de murcia fault is one of the main active structures of the eastern betic shear zone se spain characterized by the presence along its trace of neogene basins developed under early to late miocene extensional tectonics a dominant nnw sse shortening direction is active from late miocene driven by the present day plate convergence we present the structural analysis of the northeastern section of this fault where reliable estimations of slip rates were unknown due to the lack of geomorphological evidence of recent activity the recent tectonic evolution and reactivation of the northeastern section is closely related to the fortuna basin development and tectonic inversion we approach the structural analysis through the interpretation of seismic reflection profiles well data fieldwork and 3d geological modeling we estimated a maximum long term slip rate of 0 32 0 18 0 13 mm yr in the librilla sector last 4 8 7 6 ma based on cross section restorations and assuming current motion trends from gps data according to the results from the cross sections restored along the section and a vertical displacement analysis based on a 3d model the slip rate distribution shows a decrease of activity toward the northeastern tip of the studied fault section this supports a transference of deformation between the alhama de murcia fault and the carrascoy fault which seems to absorb part of the shortening during the plio quaternary explaining the lower relief created by the activity of the northeastern section the slip rates obtained have important implications in seismic hazard assessments and in the distribution of deformation along the region

seismotectonics of the 20 october 1991 uttarkashi earthquake in garhwal himalaya north india the 20 october 1991 uttarkashi earthquake killed over a thousand people and caused extensive damage to property in the garhwal himalaya region the body wave magnitude of the earthquake was 6 6 and the fault plane solution indicates reverse faulting the hypocenrre was located at a focal depth of about 12 km between the chail and jutogh thrusts but movement propagated southward along the jamak gangori fault jgf and dunda fault df which are developed as blind faults related to the growing uttarkashi antiform

cenozoic deformation history of the qaidam basin nw china results from cross section restoration and implications for qinghai tibet plateau tectonics abstract the deformation and uplifting history of the qinghai tibet plateau is a controversial issue and so far there has been insufficient evidence for interpretation investigations of the cenozoic deformation in the northeastern edge of this plateau may provide some relevant information in this paper the cenozoic deformation history of the qaidam basin has been studied based on results from the balanced cross section restoration of six geological sections they indicate that 1 the qaidam basin has been undergoing continuous shortening since the beginning of cenozoic with two relatively fast shortening phases the first during 42 8 40 5 ma and the second during 2 8 ma present 2 the shortening rate of the qaidam basin reached its maximum value since 2 8 ma and approximately 32 of the average total cenozoic shortening took place in this period and 3 the shortening of all sections reached approximately 50 of their respective total shortening by miocene the cenozoic deformation history of the qaidam basin shows good synchroneity with uplifting history of the qinghai tibet plateau it is therefore proposed that the deformation and uplifting in the south and north edges of the qinghai tibet plateau was almost synchronous with the altyn tagh fault formed at the beginning of india asia collision accordingly it is postulated that since the india asia collision at the beginning of cenozoic the indian plate moved northward continuously with two relatively fast phases the first during 42 8 40 5 ma and the second during 2 8 ma present approximately 50 of the total cenozoic northward displacement of the indian plate of the total amount of crustal shortening and uplifting of the qinghai tibet plateau and of the total cenozoic strike slip displacement of the altyn tagh fault were probably reached by the early miocene moreover another 30 40 might have taken place during 2 8 ma present the periods during 42 8 40 5 ma and during 2 8 ma present may also be the two fast phases for crustal shortening and uplifting of the qinghai tibet plateau and strike slip displacement of the altyn tagh fault

infrared reflectance spectroscopy of martian analogues one of the main goals of mars exploration is to determine the characteristics of surface materials to shed light on its geological evolution to this end infrared spectra acquired by ground based observations and by space borne remote sensing represent one of the most diagnostic tools in order to best interpret these data a careful comparison with laboratory spectra of martian surface analogues is needed in the present work we report the results of transmittance specular and diffuse biconical reflectance measurements of three materials potentially representative of bright regions on the surface of mars andesite palagonite and montmorillonite few spectroscopic data are available in the literature for andesite the palagonite from etna volcano exhibits important differences from hawaiian palagonite although montmorillonite has been already studied by various authors it was included here in order to build a self consistent set of data the infrared spectral range covered by our measurements 400 6000 cm 1 matches most of the mars radiance spectrum and the spectral resolution of 2 cm 1 has allowed us to perform an accurate band identification using the measurements we have computed the optical constants of the samples the chemical and morphological characterization of the analyzed samples has allowed us to perform a careful interpretation of the observed spectral features the dependence of the band intensities observed in diffuse reflectance on the particle size was used to identify fundamental and combination overtone bands this complex of laboratory data obtained by morphological chemical and spectroscopic analyses provides a reference for the martian mineral identification through interpretation of remote observations

variation of vertical stress in the carnarvon basin nw shelf australia abstract variations in vertical stress magnitudes can be attributed to lateral facies variations diagenesis localized uplift and disequilibrium compaction overpressure vertical stress magnitudes have been calculated using density and checkshot data from 47 wells in the carnarvon basin on the nw shelf of australia the vertical stress ranges from 20 2 mpa km 1 to 23 8 mpa km 1 below seabed demonstrating a significant variation across the basin the largest vertical stress magnitudes were calculated for the dampier sub basin the eastern barrow sub basin and on the peedamullah shelf the smallest vertical stress magnitudes were calculated in the kangaroo syncline the western barrow sub basin and offshore across the exmouth plateau high rock densities thus high vertical stress magnitudes can be due to uplifted rock that is over compacted relative to its current depth in the carnarvon basin areas of elevated vertical stress magnitudes correspond to areas of identified uplift uplift at the bambra anticline has previously been estimated to be approximately 900 m calculations within the bambra 4 well demonstrate that a 900 m increase in burial depth of a regionally consistent lithostratigraphic unit the muderong shale equates to a 0 22 g cm 3 increase in rock density thus the difference between uplifted over compacted rock and normally compacted rock no uplift is equivalent to a difference in the vertical stress magnitude of 2 1 mpa km 1 at the bambra anticline this value totalling the difference between over compacted uplifted and normally compacted sedimentary rock 2 1 mpa km 1 accounts for some part of the 3 6 mpa km 1 variation in vertical stress magnitude observed across the carnarvon basin therefore recent tectonic uplift has had a significant impact on the present day magnitude of the vertical stress and is interpreted to be responsible for the majority of observed variation of vertical stress in the carnarvon basin

origin of rollover rollover is the folding of hanging wall fault blocks by bending or collapse in response to slip on nonplanar commonly listric normal faults the shapes of rollover folds are controlled by a number of variables including 1 the shape of the fault 2 the total fault slip after a bed is deposited 3 the direction of relative particle motion in hanging wall collapse 4 the history of sedimentation rate relative to fault slip rate and 5 compaction the importance and role of each of these variables is illustrated by a two dimensional balanced structural modeling technique that treats continuously curved faults as though composed of a large number of straight fault segments in this modeling an active axial surface oriented parallel to the direction of relative p rticle motion in hanging wall collapse emanates from each fault bend and is the instantaneous locus of folding the quantitative correctness of this theory of rollover is tested by modeling natural structures from the gulf of mexico for which both fault shape and fold shape are known from high quality seismic and well sections the direction of hanging wall collapse commonly is in the antithetic or synthetic normal fault or coulomb shear orientations although sliding along weak bedding planes also is an important collapse mechanism in some regions collapse is in the antithetic shear direction for concave fault bends and in the synthetic shear direction for convex bends these collapse directions can be observed directly in some high quality seismic images as axial surfaces emanating from fault bends the shapes of rollovers within growth strata depend strongly on the sedimentation rate relative to fault slip rate as well as the total slip after a bed is deposited the crests of classic gulf coast rollovers are growth axial surfaces along which are abrupt changes in sedimentation rate within the growth st atigraphic interval these changes are produced by deformation of the sediment water interface along active axial surfaces compaction can substantially modify the relationship between fault shape and rollover shape however under certain common conditions the history of compaction can be neglected if the folding is modeled in the compacted state

geometric models of listric normal faults and rollover folds existing geometric models allow master fault shapes to be constructed given the shape and heave or displacement of a deformed marker horizon in the hanging wall these models assist in projecting normal faults to depth where the fault geometry is poorly constrained by available seismic data currently it is unclear which model best predicts the actual relation between rollover and fault geometries to address this deficiency the relative accuracies of the constant heave constant displacement constant bed length slip line and inclined shear constructions are evaluated using clay model analogs and seismic examples each of the geometric models predicts a different fault shape and depth to detachment for the same rollover shape because different hanging wall deformat on mechanisms are assumed a construction is developed for determining the hanging wall geometry from a known fault geometry this construction is based on the inclined shear model and geometric constraints imposed by material displacement paths viewed from different reference frames fixed to the hanging wall and footwall blocks in clay models the inclined shear antithetic shear greek alpha 20 degrees and slip line constructions produce the best agreement between actual and modeled fault and marker bed shapes in rollovers for subsurface examples the inclined shear model antithetic shear greek alpha 20 40 degrees and the constant displacement model predict fault trajectories that are the most similar to the positions and shapes of the master fault segments interpreted fr m offshore norway and gulf of mexico seismic lines the shear angle required in the inclined shear model can often be estimated from the orientation of minor faults in the hanging wall the shear angle may also be determined through iterative modeling in which the shear angle is systematically varied and the resultant model fault shape is compared to the shape of the shallow segment of the master fault interpreted from the seismic record

restoration of cross sections to constrain deformation processes of extensional terranes abstract restoring balanced cross sections constrains the possible deformation processes affecting extensional terranes with a ductile substratum such as salt and syndeformational sedimentation cross sections are divided into fault blocks and shear domains each of which can be undeformed with a different set of parameters the success of restorations is judged by compatibility between the blocks and the reasonableness of the restored structures fault blocks in physical models restore with simple shear at about 60 dipping in the direction which removes extension corresponding to an antithetic orientation in the hangingwalls of normal growth faults and subparallel to the fault in the footwall other components of the deformation are rigid rotation translation and decompaction shear angles inferred from natural examples are more varied ranging from vertical to moderately inclined nearly always dipping in a direction that removes extension

cretaceous tertiary inversion history of the dampier sub basin northwest australia insights from quantitative basin modelling abstract seismic sequence analysis has been combined with a kinematic and flexural model for the deformation of the lithosphere to define the history distribution and magnitude of inversion within the dampier sub basin northwest australia during the cretaceous and tertiary inversion tends to be focused along the trend of pre existing border fault systems and or internal to the basin across the roll over anticlines of collapsed hangingwall blocks the spatial distribution of inversion varied with different faults involved in the inversion process at different times whereas cretaceous inversion concentrated along major boundary faults of the northeast southwest oriented rankin madeleine and rosemary legendre trends the locus of miocene inversion was located adjacent to the northwest limits of the rosemary legendre trend total shortening of the lithosphere during the santonian and tertiary was modelled to be 2 6 and 0 16 km respectively with northeast southwest trends being preferentially reactivated the amplitudes of inversion structures range from 1000 m over the eastern rankin trend to hundreds of metres for inversion structures comprising the rosemary legendre trend although responsible for the development of relatively subtle features inversion has critically controlled the major structures for trapping hydrocarbons within the dampier sub basin

predicting strain using forward modelling of restored cross sections application to rollover anticlines over listric normal faults a strategy to predict strain across geological structures based on previous techniques is modified and evaluated and a practical application is shown the technique which employs cross section restoration combined with kinematic forward modelling consists of restoring a section placing circular strain markers on different domains of the restoration and forward modelling the restored section with strain markers until the present day stage is reached the restoration algorithm employed must be also used to forward model the structure the ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small scale fractures the forward model may be frozen at different time steps different growth stages allowing prediction of both spatial and temporal variation of strain the method is evaluated through its application to two stages of a clay experiment that includes strain markers and its geometry and deformation history are well documented providing a strong control on the results to demonstrate the method s potential it is successfully applied to a depth converted seismic profile in the central sumatra basin indonesia this allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults

the status of central seismic gap a perspective based on the spatial and temporal aspects of the large himalayan earthquakes abstract the central himalaya considered as a prominent seismic gap is generally believed to be the most vulnerable segment due for a great plate boundary earthquake m 8 two significant historical earthquakes are known to have occurred in this region in ad 1505 and 1803 interpreted by some workers as great earthquakes occurrences of these events question the validity of central himalaya being a seismic gap here we analyze the macroseismal data from the central himalaya and the gangetic plains and suggest that neither of these earthquakes can be qualified as a plate boundary type event and the size of at least the 1803 does not exceed mw 7 7 our studies further indicate that the central himalayan frontal thrusts may be undergoing a quiescence of 1000 years in terms of generation of great earthquakes assuming a steady elastic strain accumulation due to plate convergence and its simple translation as periodic great earthquakes such long quiescence may appear intriguing we suggest that the long term quiescence and the spatial and temporal clustering that characterize the distribution of large earthquakes in the himalaya is a manifestation of the tectonic deformation associated with a highly evolved fold and thrust belt our analyses also indicate that the large moderate earthquakes are mostly concentrated on higher level thrusts these structures probably accommodate most of the seismogenic slip in the himalaya and the rest of the strain could possibly be expended on passive folding consequently great earthquakes m 8 are relatively infrequent as in the case of central himalaya apparently leading to long periods of quiescence

kinematic evolution and fracture prediction of the valle morado structure inferred from 3 d seismic data salta province northwest argentina the valle morado structure located in northwest argentina is an approximately 7 km long and 4 km wide north northeast south southwest trending anticline cut by faults that involve paleozoic basement and mesozoic cenozoic sedimentary cover geological interpretation of a three dimensional seismic survey that covers the structure plus a well and two dimensional regional scale seismic lines indicates that the valle morado is an andean pop up structure formed by foreland directed faults resulting from reverse reactivation of cretaceous extensional faults dipping westward and newly formed hinterland directed reverse faults dipping eastward the orientation of the preexisting extensional faults is nearly perpendicular to the andean tectonic transport direction in the northern part of the structure and oblique toward the south resulting in almost pure contraction in the north and transpression southward curvature analysis performed on two interpreted reservoir seismic horizons suggests that the maximum density of open fractures is likely to occur along the anticline axis in the northern portion of the fold and along the northeast southwest striking foreland directed reactivated faults to the south the direction of the open fractures interpreted from ultrasonic borehole image data along the well coincide with that of the open fractures predicted from the curvature analysis

sandbox model studies of inversion tectonics abstract scaled plane strain sandbox models have been used to simulate basement controlled structural inversion in a sedimentary overburden two basement configurations were tested in the first one reversal of movement along vertical and normal faults that controlled a graben relief induced only a partial recovery of displacement along the pre existing overburden faults the inversion produced new reverse faults in the footwall of the pre existing overburden faults the reactivated normal faults and the new reverse faults defined wedge shaped fault blocks at the edges of the inverted structure in the second configuration the relationship between inversion and tilted fault blocks was tested when a tilting basement block does not move parallel to its bounding fault a compression is induced in the overburden which generates an inverted structure bounded by new reverse faults both experiments show that structural inversion not only reactivates pre existing faults but also generates new faults in the overburden faults related to inversion are the result of horizontal compression either associated with rotation of one of the fault blocks or with vertical uplift of basement blocks

half graben structures balanced models of extensional fault bend folds one common structural style in extensional regimes is a half graben bounded on one side by a master normal fault and on the other side by a domain of beds dipping toward the master fault this geometry is modeled as being caused by a bend in the master fault the hanging wall beds dipping toward the master fault are bounded by axial surfaces formed as the hanging wall moves past the bend resulting in an extensional fault bend fold the footwall beds remain undeformed and unrotated the major assumptions used in the derivation are that the geometry is area balanced and that the axial surfaces in the hanging wall have dips equal and opposite to the dip of the master fault above the bend important consequences of the model include a relationship between master fault dip above and below a bend and the amount of hanging wall dip the horizontal width of the dipping beds in the hanging wall is twice the heave on the master fault above the bend the asymmetry of the axial surfaces in the hanging wall requires that the rotated beds be strained hanging wall beds dipping toward the master fault are predicted for a fault bend wherein the dip decreases downward hanging wall beds dipping away from the master fault are predicted for a bend wherein the dip increases downward the model fits measurements taken from a published ramp and flat clay model by e cloos and is used to develop a balanced and restorable cross section of the schell creek fault a basin and range structure in nevada

along strike growth of the ostler fault new zealand consequences for drainage deflection above active thrusts 1 rarely are geologic records available to constrain the spatial and temporal evolution of thrust fault growth as slip accumulates during repeated earthquake events here we utilize multiple generations of dated and deformed fluvial terraces to explore two key aspects of the along strike kinematic development of the ostler fault zone in southern new zealand over the past 100 k y accumulation of fault slip through space and time and fixed length thrust growth that results in patterns of drainage diversion suggestive of laterally propagating faults along the ostler fault surface deformation patterns revealed by topographic surveying of terrace profiles in nine transverse drainages define systematic variations in fault geometry and suggest deformation over both listric and planar thrust ramps kinematic modeling of folded terrace profiles and 100 fault scarp surveys along major fault sections reveals remarkably similar slip distributions for multiple successions of geomorphic surfaces spanning 100 k y spatially abrupt and temporally sustained displacement gradients across zones of fault section overlap suggest that either persistent barriers to fault propagation or interference between overlapping faults dominate the interactions of fault tips from the scale of individual scarps to the entire fault zone deformed terrace surfaces dated using optically stimulated luminescence and cosmogenic radionuclides indicate steady maximum rates of fault slip of 1 9 mm yr during the late quaternary slip data synthesized along the central ostler fault zone imply that displacement accumulated at approximately constant fault lengths over the past 100 k y a northward temporal progression of abandoned wind gaps along this section thus reflects lateral tilting in response to amplification of displacement rather than simple fault lengthening or lateral propagation oscillations of climate at 104 yr time scales modulate the formation and incision of geomorphic surfaces during successive glacial stages superimposed on apparently steadier rates of fault slip such climate dependent surfaces contribute to a pattern of progressive drainage deflection along the central ostler fault zone that is largely independent of fault propagation

the kumaun and garwhal lesser himalaya india part 1 structure and stratigraphy our understanding of the geologic evolution of the himalaya remains incomplete particularly in regard to structural and geochronologic details of the proterozoic paleozoic lesser himalayan sequence we conducted an integrated field mapping geochronological study and geochemical analysis of the lesser himalayan sequence strata in the kumaun and garwhal himalaya of nw india 78 00 80 30 e structural observations reveal a systematic change in deformation styles from lower to higher structural levels in the main central thrust footwall in the south and at lower structural levels the main central thrust footwall is characterized by parallel folding and sparse development of axial cleavage quartz microstructures indicate that deformation occurred at temperatures below 350 c in contrast in the north and at higher structural levels close to the main central thrust deformation is characterized by replacement of original bedding the development of penetrative cleavage and schistosity locally folds are tight in places isoclinal and overturned the corresponding quartz microstructures indicate that deformation occurred above 350 c dating of detrital zircons from lesser himalayan sequence metasedimentary units and igneous zircons from schistose gneisses throughout the lesser himalayan sequence allow refinements to the stratigraphic framework first unlike has been observed in western nepal immediately west of our study area u pb zircon dating suggests the absence of paleoproterozoic strata in the ramgarh thrust hanging wall this suggests that the thrust cuts upsection laterally along strike second u pb detrital zircon dating suggests that metasedimentary strata in the ramgarh thrust hanging wall are correlative with basal units of the outer lesser himalayan sequence removing the necessity that the ramgarh thrust hanging wall was allochthonous with respect to its footwall lesser himalayan sequence units schistose gneisses with u pb ages of ca 1850 ma are older than lesser himalayan sequence units in the area suggesting that they are thrust emplaced lesser himalayan sequence basement we conclude that the ramgarh thrust is an out of sequence thrust postdating a folding event in its footwall the earlier proposal that neoproterozoic cambrian lesser himalayan sequence strata are the southern extension of the tethyan himalayan sequence requires that the tons thrust which separates the distal and proximal facies of the lesser himalayan sequence be a major south directed structure with a slip magnitude of 50 100 km

chronologic modeling of faulted and fractured reservoirs using geomechanically based restoration technique and industry applications we have developed a geomechanically based restoration method to model reservoir deformation the approach founded on the finite element method simulates the physical behavior of the rock mass and considers heterogeneous material properties bedding slip and the mechanical interaction of faults to demonstrate the method s potential we analyze the deformation and fault growth in the hanging wall of a synsedimentary listric normal fault from a sand box model which provides an analog for evaluating complex faulted reservoirs the numerical model results are then analyzed to investigate the chronology of faulting the numerical model corresponds well to the physical model and provides additional insights about reservoir evolution and deformation the approach is also tested on a natural example of folding using outcrop data to study contractional deformation these examples illustrate how undetected faults and fractures reservoir compartmentalization hydrocarbon migration pathways and hydrocarbon traps can be understood in the context of tectonic processes and how this understanding can be exploited in decision making and reducing risk we conclude that the geomechanically based restoration of faulted and fractured reservoirs has significant potential for industry applications compared to common geometric restoration techniques which lack a mechanical basis

the geometry of listric normal faults and deformation in their hangingwalls abstract in cross sections containing listric extensional faults area balancing techniques for depth to decollement are usually based on either bed length conservation or displacement conservation listric fault geometry may be constructed from a hangingwall roll over profile using the chevron construction this construction based on conservation of heave necessitates a reduction in fault displacement with decreasing fault dip a modification of this construction utilizing conservation of fault displacement predicts a listric fault that detaches at a shallower depth a new construction based on slip lines uses fault perpendicular displacement segments to generate listric fault shape fault propagation strain may be responsible for anomalous hangingwall geometries and these can be predicted by forward modelling using either a modified chevron construction or a slip line construction

inversion of synrift normal faults in the high atlas mountains morocco copyright 1997 society for exploration geophysics see also http segdl aip org getabs servlet getabsservlet prog normali http atlas geo cornell edu morocco publications beauchamp1997 htm

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

geological structures and controls on half graben inversion in the western gunsan basin yellow sea abstract this paper focuses on the structural styles of an inverted half graben in the western gunsan basin cretaceous paleogene in the yellow sea detailed seismic interpretation calibrated by well data indicates that the half graben formed by the cretaceous to eocene extension and subsequently underwent contraction which led to the basin inversion the inversion occurred during the oligocene and middle miocene in the oligocene inversion phase the hanging wall strata underwent shortening by inverted extensional faults newly formed reverse faults and fault related folds the inversion deformation was caused by an nne directed regional contraction that is nearly normal to the orientation of earlier extensional faults the style and distribution of internal deformation was mainly governed by variations in the dip angle of the pre inversion fault plane the early miocene inversion phase commenced with the development of a broad asymmetric hanging wall anticline caused by the preferential reactivation of the nw trending bounding fault this preferential reactivation suggests an orientation change of inversion stress from the oligocene nne directed to the miocene ne directed contraction the bounding fault continued to be reactivated during the middle miocene which caused the growth of a monocline

cross section restoration and balancing as aid to seismic interpretation in extensional terranes structural cross sections in extensional terranes can be improved significantly by restoration and balancing principles originally developed for fold and thrust belts in rift basins and passive continental margins use of restoration techniques in analysis of growth faults elongate salt swells and other extensional structures results in geologically valid seismic interpretations sections must be in depth as opposed to two way time and oriented in the direction of material transport and decompaction must accompany restoration hanging wall deformation is characterized by different processes depending on the mechanical properties of the rocks being extended and can be approximated by various geometric and kinematic models antithetic faulting is analogous to antithetic shear combined antithetic and synthetic faulting is approximated by vertical shear domino style extension corresponds to rigid body rotation and flexural slip flow is modeled by bed length balance methods selection of the appropriate algorithm is crucial for proper restoration and balancing applications of these techniques illustrated here using seismic data from the gulf coast and north sea include 1 evaluating and adjusting seismic interpretations 2 projecting listric fault trajectories to depth 3 delineating more accurately the geometry and extent of hydrocarbon reservoirs 4 identifying new exploration leads 5 determining the deformation history of an area and 6 constraining the timing and direction of hydrocarbon migration and entrapment

sequence of formation of back limb thrusts and imbrications implications for development of idaho wyoming thrust belt computer synthesized structural cross sections show back limb thrusts or splays of larger thrusts may form in the same sequence as the regional development of a thrust belt the computer models are independent of scale and are pertinent to both small scale imbricate structures and larger scale problems such as the timing of the darby and prospect thrusts in the wyoming thrust belt modified journal abstract

characterizing the main himalayan thrust in the garhwal himalaya india with receiver function ccp stacking abstract we use common conversion point ccp stacking of ps receiver functions to image the crustal structure and moho of the garhwal himalaya of india our seismic array of 21 broadband seismometers spanned the himalayan thrust wedge at 79 80 e between the main frontal thrust and the south tibet detachment in 2005 2006 our ccp image shows the main himalayan thrust mht the detachment at the base of the himalayan thrust wedge with a flat ramp flat geometry seismic impedance contrasts inferred from geologic cross sections in garhwal imply a negative impedance contrast velocity decreasing downward for the upper flat located beneath the lower himalaya and a positive impedance contrast velocity increasing downward for the ramp located beneath the surface trace of the munsiari thrust or mct i at the lower flat located beneath the higher himalaya spatially coincident measurements of very high electrical conductivities require the presence of free fluids and we infer a negative impedance contrast on the mht caused by ponding of these fluids beneath the detachment our seismic image indicates that the upper flat of the mht is 10 km below sea level and dips north at 2 connecting to a mid crustal ramp which is 10 km high and dips at 16 the lower flat is 20 25 km below sea level and dips at 4 the main central thrust mct appears as a negative impedance contrast dipping at 16 the moho is nearly horizontal at 35 45 km depth beneath the sub himalaya and lower himalaya deepening to 50 km or more beneath the higher himalaya this depth is 10 25 km shallower than in the nw indian himalaya and 5 10 km shallower than in central nepal requiring significant along strike variations in crustal thickness the observed thickness of subducted indian crust in garwhal is 20 28 km

characterization of etnean soils and application to mars we present the results of a study of some petromineralogical chemical and spectral properties of etnean palagonitic soils these soils exhibit highly variable mineralogy although they are considered among the best candidates as martian soil analogs five specimens of etnean volcanic soil were collected at different altitudes four of these are weathered and reworked pyroclasts from the historic eruptive activity the fifth represents an ancient paleosoil 5420 2370 years b p the chemical composition is hawaiitic petrography and mineralogy of grain mounts show they mainly consist of glass particles black and red orange containing microphenocrystals of plagioclase clinopyroxene olivine and ti magnetite in order of abundance one sample also contains rare amphiboles ir 2 3 25 m transmittance and uv visible near ir 0 4 2 6 m diffuse reflectance spectra were obtained and compared with those of martian dust

influence of basin architecture on the style of inversion and fold thrust belt tectonics the southern adelaide fold thrust belt south australia abstract the southern adelaide fold thrust belt involves neoproterozoic adelaidean strata deposited during protracted rift and sag phases and an overlying cambrian kanmantoo sequence represented by a thick wedge of turbidites rapidly deposited in an eastwards deepening basin deeply incised into the underlying rocks the belt was deformed during the delamerian orogeny developed at the southeastern margin of the australian craton during early palaeozoic nw directed displacement during this shortening event the margin of the kanmantoo basin was reactivated and formed a significant strain guide that controlled key features of the fold thrust belt strain integrated and restored sections reveal contrasting geometric and kinematic styles along the strike of the belt a transpressional zone is developed at the steep basin margin in the south oriented oblique to the structural grain the central parts of the belt are dominated by strong buttressing growth fault reactivation and basement involved footwall shortcut thrusting in the northern part of the belt shortening is accommodated by homogeneous folding above a master de collement these variations in regional structural style and internal strain partitioning reflect significant variations in the original kanmantoo basin margin geometry rheological parameters control the partitioning of strain associated with pervasive fabrics for example cleavage and transposed bedding folding is accompanied by negative line length changes shortening in the northern part of the belt in its thrusted central part pelites commonly show positive line length changes psammites were least affected by line length changes and thus provide key beds for section balancing pervasive strain makes a full restoration of cross sections impossible however incorporating regional strain data assists establishment of balanced and restorable sections which provide a powerful tool in understanding both pre deformational basin geometry and its shortening

interpretation validation on vertically exaggerated reflection seismic sections abstract reflection seismic data is usually displayed with a vertical exaggeration factor in the range 2 6 irrespective of whether it is time or depth domain data this vertical exaggeration gives certain advantages to stratigraphic and structural interpretation and is sometimes a prerequisite to view long wavelength structures however vertical exaggeration distorts geological structures affecting dip curvature line length cross sectional area volume and angular relationships reflection seismic can be assigned a vertical exaggeration heterogeneity factor based on the extremes of seismic velocities in the absence of appreciable poorly compacted units and bathymetry and generally on depth domain data vertical exaggeration is relatively homogeneous analytical solutions are derived to quantify the distortion of angular relationships curvature and bed thickness under homogeneous vertical exaggeration modelled extensional and compressional geometries give acceptable area balance restorations using vertical shear under homogeneous vertical exaggeration these vertically exaggerated restorations are neither admissible nor viable because the deformed and restored state sections are unrealistic given low heterogeneity of vertical exaggeration and relatively simple structure that typifies many extensional geometries and some thrust geometries aspect ratios of 1 1 are not definitively required for section validation by restoration

application of geometric models to inverted listric fault systems in sandbox experiments paper 1 2d hanging wall deformation and section restoration abstract fault geometry is a primary control on hanging wall deformation in order to examine their geometrical relationships a positive inversion analogue experiment was conducted using a rigid fault surface of listric geometry the hanging wall deformation observed on a representative vertical section was examined with conventional 2d geometric models and was restored to its pre inversion phase with two techniques these results suggest that the deformation can be best approximated by inclined simple shearing iss the iss model can determine the inclination of the apparent shear plane and the amount of apparent horizontal shortening which is equivalent to that calculated with the conventional depth to detachment method this estimated apparent shortening was generally smaller than the actual amount of the experiments probably due to tectonic compaction

estimated detectability limits of iron substituted montmorillonite clay on mars from thermal emission spectra of clay palagonite physical mixtures the thermal emission properties of two mars soil analogs palagonite and iron substituted montmorillonite clay and their physical mixtures are presented in the 5 to 25 m 2000 to 400 cm 1 region the clay spectrum has both greater number of spectral features and higher emissivity contrast when compared to the palagonite spectrum emissivity peaks located near 8 9 11 1 and 19 9 m 1120 905 and 505 cm 1 and troughs restsrahlen features located near 8 8 9 7 18 9 and 22 2 m in the spectrum of the clay provide the ability to identify the presence of clay when it is physically mixed with the palagonite in the mixtures studied when 15 wt of clay is mixed with 85 wt palagonite the 19 9 m emissivity peak and the 9 7 m reststrahlen trough are readily identifiable but the 8 9 and 11 1 m peaks and the 8 8 9 3 and 18 9 m troughs are only marginally identifiable this indicates that identification of clays on mars using midinfrared data should rely upon the sensitivity of the 19 9 and 9 7 m features to the clays presence

structural restoration of seismic and geologic sections in extensional regimes seismic sections from extensional basins can be structurally transformed to produce restored seismic sections showing subsurface geology of the past restoration is achieved using a simple and effective algorithm which is suited for use in an interactive seismic interpretation environment seismic data are resampled along paleovertical trajectories which are the deformed equivalents of what were originally closely spaced vertical lines paleoverticals are generated within the present day section as follows 1 origin points are equally spaced along a reference horizon that corresponds to an original depositional surface 2 paleovertical segments are vertical within fault blocks 3 paleoverticals are offset across faults by the reference horizon slip and 4 restor d depth is equated to distance down a paleovertical these rules can be modified to conform with such styles of extensional deformation as vertical simple shear inclined shear or rigid rotation and to account for compaction structures with complex fault patterns readily are restored several examples from the gulf of mexico and offshore west africa show that seismic restoration is useful for 1 unravelling structural and stratigraphic history 2 revealing tectonically masked features and 3 checking interpretations across faults for seismic correlation and structural balance geologic sections can be restored in similar fashion

kinematic structural restorations and discrete fracture modeling of a thrust trap a case study from the tarija basin argentina the integration between kinematic structural restorations and discrete fracture simulation is applied to a thrusted and fractured fault block in the tarija basin northern argentina the emphasis is on the influence of the factor time on the deformation history and fracture growth the structural evolution of the gas bearing santa rosa reservoir forms the basis for understanding the development of the 3d fracture system as simulated with 3d kinematic restorations during the restoration the cumulative dilatational strain was calculated and mapped and compared to traditional curvature analyses the strain maps are subsequently used to simulate geologically realistic discrete fracture networks that form the basis for further exploration and development of the field

intensity magnitude location and attenuation in india for felt earthquakes since 1762 a comprehensive consistently interpreted new catalog of felt intensities for india martin and szeliga 2010 this issue includes intensities for 570 earth quakes instrumental magnitudes and locations are available for 100 of these events we use the intensity values for 29 of the instrumentally recorded events to develop new intensity versus attenuation relations for the indian subcontinent and the himalayan region we then use these relations to determine the locations and mag nitudes of 234 historical events using the method of bakun and wentworth 1997 for the remaining 336 events intensity distributions are too sparse to determine mag nitude or location we evaluate magnitude and location accuracy of newly located events by comparing the instrumental with the intensity derived location for 29 cali bration events for which more than 15 intensity observations are available with few exceptions most intensity derived locations lie within a fault length of the instrumen tally determined location for events in which the azimuthal distribution of intensities is limited we conclude that the formal error bounds from the regression of bakun and wentworth 1997 do not reflect the true uncertainties we also find that the regression underestimates the uncertainties of the location and magnitude of the 1819 allah bund earthquake for which a location has been inferred from mapped surface deformation comparing our inferred attenuation relations to those developed for other regions we find that attenuation for himalayan events is comparable to intensity attenuation in california bakun and wentworth 1997 while intensity attenuation for cratonic events is higher than intensity attenuation reported for central eastern north america bakun et al 2003 further we present evidence that intensities of intraplate earth quakes have a nonlinear dependence on magnitude such that attenuation relations based largely on small to moderate earthquakes may significantly overestimate the magnitudes of historical earthquakes