the bristol mendip foreland thrust belt the thrusts and associated fold structures of the bristol mendip area are interpreted in terms of a thin skinned piggy back foreland thrust belt of variscan age with dominant northward transport strike normal balanced sections and compatible strike parallel sections have been constructed to illustrate the 3 d geometry of the linked thrust system north south shortening of c 20 km 40 is calculated from deformed and restored strike normal sections a thick and extensive thrust wedge of pre old red sandstone basement in the west of the area is responsible for culminations expressed at the surface as the mendip periclines uplifted culminations permit erosion to lower stratigraphic levels in the west and south of the area strike parallel sections and a hanging wall cut off map indicate that the majority of thrusts in the area are mainly oblique ramps rather than simple frontal and lateral ramps or flats the en echelon pattern of the mendip periclines may be related to the oblique ne climb of two of these thrusts the angle of frontal ramp climb through the dinantian stratigraphy is generally low and this explains the presence of numerous klippen of lower on upper carboniferous rocks whilst suggesting that certain thrust sheets were much more extensive than present outcrops indicate early pre thrusting movement on basement lineaments in the variscan foreland created uplifts angular unconformities and a predominance of n s structures in the north of the area

extremely early recurrence of intraplate fault rupture following the tohoku oki earthquake intraplate earthquakes on a fault in earth s upper crust commonly recur in 1 000 years or longer the 2011 m9 tohoku oki earthquake triggered the activation of intraplate earthquakes in northern kanto japan including two m6 events on 19 march 2011 and 28 december 2016 located near one another here we use displacements captured by satellite radar and the global navigation satellite system to show that the two earthquakes ruptured an identical fault detailed fault slip modelling shows that the deformation data for the two earthquakes are well explained by slip along a common fault geometry and that the majority of the slipped area on the fault overlaps strain analysis reveals that the first m6 earthquake was followed by exceptionally large postseismic deformation such deformation is consistent with afterslip around the m6 rupture area which in turn rebuilds the shear stress on the fault enabling the next earthquake we infer that the rapid and large postseismic deformation of the 2011 tohoku oki earthquake promoted such afterslip and made the second earthquake recur in just 5 8 years this study suggests a mechanism to explain observations of extreme temporal clustering in palaeoseismic earthquake recurrence studies a pair of closely spaced intraplate earthquakes in japan can be explained by postseismic deformation associated with the 2011 tohoku oki earthquake

structural geological factors in open pit coal mine design with special reference to thrusting case study from the ffyndaff sites in the south wales coalfield

etude de l equilibre isostatique dans le sud ouest de l ocean indien a l aide des resultats de refraction sismique abstract the aseismic ridges of the southwestern indian ocean are in isostatic equilibrium with respect to the adjacent deep basins the structural units can be split into two different groups according to their mean crustal densities we demonstrate that the crustal thickness within the two groups is a linear function of the water depth this relationship expresses the airy isostatic equilibrium however the southern domain of the madagascar ridge is balanced neither with the northern domain of the ridge nor with any other unit of the area of study the northern domain has undergone only slight subsidence since the middle eocene while the southern domain would have rapidly subsided since the early miocene

balanced cross sections and their implications for the deep structure of the northwest alps reply abstract the structure of the northwest external french alps around the internal belledonne and mont blanc massifs in the beaufortain area can be explained by foreland wnw propagating thrust tectonics the internal belledonne massif is interpreted as having developed by imbrication of an originally thin skin of basement with a mesozoic cover above this massif all thrusts tend to climb lateral sections to the south to converge with the frontal pennine thrust the southern termination of the mont blanc massif is merely a spectacular example of such a lateral ramp

a comparative analysis of some late carboniferous basins of variscan europe vegetation diversity and pattern changes and their relation to tectono sedimentary histories are compared between selected euramerican late palaeozoic coalfields to understand better the controls on the dynamics of the pennsylvanian terrestrial ecosystems and to demonstrate the problems with comparing data from various basins the analysis is based on data from the following basins of different geotectonic and palaeogeographical positions the cratonic pennines basin the foreland south wales and upper silesia basins and the fault related intra sudetic and central and western bohemia basins the analysis indicates that complex factors are responsible for changes in plant diversity and vegetation patterns these are related to climate tectonics preservation potential sampling biases and the current state of revision of the flora in each basin plant diversity patterns in the basins differ because of local controls and or the character and detail of the available data maximum diversity varies among the basins within the langsettian and duckmantian substages two apparent step like drops in diversity were detected within coal bearing strata of most basins at the duckmantian bolsovian boundary and at the bolsovian asturian boundary further and more prominent falls are related to transitions from coal bearing to non coal bearing mostly red bed strata or vice versa during stephanian times interpretation of climatic signals recorded in the sedimentary successions indicates that westphalian and middle stephanian times were wet intervals whereas early and late stephanian times were drier

lateral and vertical changes of deformation style in the osen roa thrust sheet oslo region abstract changes in deformation style and amounts of shortening in the osen roa thrust sheet of the oslo region occur vertically and laterally approaching the thrust front in the south deformation in the cambromiddle ordovician sequence passes laterally from closely spaced imbricates in the north 50 60 shortening through triangle pop up and imbricate zones toward the south 20 37 shortening to widely spaced zones of deformation up to 20 shortening approaching the thrust front changes in deformation style are attributed to changing boundary conditions across the klekken thrust declining end of orogenic forces and an increase in thickness of competent units in the ordovician rocks to the south vertical changes in deformation style are attributed to the increasing percentage of competent units upward in the cambro silurian sedimentary rocks in the north the accompanying decrease in shortening upwards requires a structurally necessary upper detachment horizon to separate folded late middle ordovician silurian sediments from imbricated early cambro middle ordovician sediments below while southward in the oslo area the upper detachment needs to be placed between silurian and cambro ordovician units finally in eiker with less than 20 shortening the whole cambrosilurian sequence appears to have deformed as a single unit in the northern oslo region the upper detachment probably has a backthrust sense of motion above an imbricate stack passive roof duplex further south the upper detachment is probably directed toward the foreland

anomalous heat flow near the crozet plateau and mantle convection abstract a heat flow study has been performed near the crozet plateau southern indian ocean where the geoid and bathymetry are anomalously high with respect to the nearby deep ocean basins data collected on 67 ma old oceanic crust agree with simple plate model predictions at the stations furthest removed from the plateau heat flow values increase significantly towards the centre of the feature suggesting a thermal origin for this uplift the ratio of geoid to bathymetry confirms that simple crustal thickening with airy local compensation cannot explain the observations the data are compatible with a model of dynamic convective support of the plateau by an underlying thermal plume in the earth s mantle

the impact of tectonic deformation upon coal seams in the south wales coalfield uk observations on the nature and appearance of coal seams which were deformed during the late carboniferous variscan orogeny have been made over several years within a number of opencast coal sites located across the south wales coalfield the deformation of coal seams was dominated by brittle failure and subsequent movement along fracture planes examination of hand specimens and smaller scale samples using a scanning electron microscope reveals the presence of two distinct types of small scale tectonic fracture markings within deformed coals striated fracture surfaces with prominent ridges and grooves can bear a superficial resemblance to shatter cones in appearance but are unique to coal in their tectonic setting and appear to have formed by static shear failure whereas strongly polished fracture surfaces result from movement across fracture planes deformed coal seams are also affected by distinctive large scale tectonic fracture sets the extent of fracturing within coal seams can be assessed using different techniques including measuring fracture frequency directly performing various strength and hardness tests making relatively simple subjective assessments on the appearance of the coal or monitoring the size distribution of the coal product by applying some of these methods within working opencast sites it can be shown that large amounts of abnormally fractured coal were formed along coal based thrust flats or detachments but that the distribution of fractured coal along detached seams is rarely homogeneous enhanced fracturing often occurred in association with the localised thickening of seams along small scale thrusts or within coal duplexes variable seam thicknesses and pockets of structurally thickened coal are seen as the most efficient means by which the presence and location of significant amounts of fractured coal can be predicted from borehole evidence during prospecting

resolving depth dependent subduction zone viscosity and afterslip from postseismic displacements following the 2011 tohoku oki japan earthquake abstract we developed a 3 d viscoelastic finite element model of the m9 2011 tohoku oki japan earthquake capable of predicting postseismic displacements due to viscoelastic relaxation and afterslip we consider seismically inferred slab geometries associated with the pacific and philippine sea plate and a wide range of candidate viscoelastic rheologies for each case we invert for afterslip based on residual surface displacements observed gps minus that predicted due to viscoelastic relaxation to develop combined viscoelastic relaxation and afterslip models we are able to find a mechanical model that fully explains all observed geodetic on land and seafloor horizontal and vertical postseismic displacements we find that postseismic displacements are in about equal parts due to viscoelastic relaxation and afterslip but their patterns are spatially distinct accurately predicting both horizontal and vertical on land postseismic displacements requires a mantle wedge viscosity structure that is depth dependent reflecting the manner in which temperature pressure and water content influence viscosity no lateral heterogeneities within the mantle wedge viscosity structure beneath northern honshu are required westward directed postseismic seafloor displacements may be due flow via low temperature plastic creep within the lower half of a pacific lithosphere weakened by plate bending the distribution of afterslip is controlled by the location of coseismic slip from the tohoku oki and other regional historic earthquakes the paradigm by which afterslip is thought of as the dominant postseismic mechanism immediately following earthquakes with viscoelastic relaxation to follow in later years is shown to no longer be valid

deep structure of the vale of glamorgan south wales uk the deep structure of the vale of glamorgan is investigated using recently acquired seismic data reflection sections from a commercial seismic survey in the vale enable the carboniferous limestone old red sandstone and silurian sequences to be mapped in the subsurface the old red sandstone sequence thins westwards under the southern part of the vale and in the southwest corner of the vale the base of the old red sandstone is interpreted to overstep across the underlying silurian sequence in an analogous manner to its regional overstep in west wales the precambrian basement surface is not clearly represented on the sections but may coincide with the base of a reflective sequence observed in places along one of the reflection lines basement depth estimates from the reflection sections are compared with estimates derived from a new time term analysis of data from long seismic refraction lines basement depths remain uncertain to 1 2 km but appear to be greater under the central part of the vale than under the western part and along the south coastal zone a linked system of variscan forethrusts is traced to outcrop in the core of the cowbridge anticline but none involves major displacement the ty9n y nant moel gilau fault system of the south wales coalfield is shown to be a component of the linked fault system and its current net extension is attributed to mesozoic reactivation of a variscan thrust involving only limited displacement the individual thrusts appear to connect to a basal thrust that may extend northwards into or under the south wales coalfield the amount of displacement along the basal thrust cannot be determined reliably but it may exceed 10 km and involve large scale repetition of palaeozoic sequences under the vale

tectonic evolution of the southwest indian ocean since the mid cretaceous plate motions and stability of the pole of antarctica africa for at least 80 myr summary the southwest indian ridge is the boundary where seafloor is being created between the african and antarctic plates east of the newly recognized du toit fracture zone at 27 e it trends north easterly and is cut by a series of six deep near north south clefts marking transform faults this series starts with the dual prince edward fracture zone near 35 e and includes discovery i1 also dual at 42 e indomed at 46 e and gallieni at 52 e terminating with the spectacular atlantis i1 and melville fracture zones at 57 30 e and 60 30 e respectively the trend of these fracture zones is compatible with an instantaneous pole of relative motion for antarctica africa at 8 4 n 42 4 w between 35 e and 55 e the development of the southwest indian ridge has separated the elevated madagascar ridge from the discontinuous crozet plateau that was contiguous to it prior to eocene time in this entire sector the ocean floor overall is elevated with respect to ocean floor of equivalent age elsewhere between these features anomalies 0 22 0 53 ma have been identified north and 13 26 35 60 ma south of the ridge axis these anomalies and 0 34 0 80 ma located just to the west in the mozambique basin lie at the same distance from the ridge axis as a similar sequence east of the bouvet triple junction the similarity in distance from the ridge axis of these anomaly sequences is evidence that africa and east antarctica have been separated by a single plate boundary from 80ma to the present the pole representing the motion of these two plates at the present has not moved in totality far from the position it occupied in the late cretaceous 80 ma furthermore calculation of intermediate finite rotation poles for four intervals within this span reveals only minor 15 excursions from the present pole the spatial reconstruction of the southwest indian ridge at 80ma anomaly 34 places the ridge midway between africa and eastern antarctica and lying at right angles to the north trending mozambique ridge the separation of antarctica from africa following initial opening in the jurassic may have been as straightforward as it appears to have been from 80 ma to the present

impact of sulphur and trace element geochemistry on the utilization of a marine influenced coal case study from the south wales variscan foreland basin abstract incremental channel samples through two high volatile a bituminous coal seams the amman rider and bute seams below and above the vanderbeckei marine band at the westphalian a b boundary have been analysed using proximate petrographic inductively coupled plasma mass spectrometry icp ms x ray fluorescence xrf and scanning electron microscopy with energy dispersive x ray sem edx techniques the results show that both coals are vitrinite rich and indicate a similar history of palaeomire development with a period of falling water tables towards the middle plies of each seam mean sulphur contents in the coal with the marine roof the amman rider seam 4 19 wt are almost 4 times higher than in the coal with a non marine roof the bute seam 1 09 wt implying that high sulphur contents are derived from sea water sulphate in both coals sulphur is predominantly in the form of pyritic sulphur both syngenetic framboidal and euhedral crystals and epigenetic vein and cleat fill pyrite are present relatively constant levels of organic sulphur at around 2 have been recorded in the amman rider seam sulphur levels in the basal and top plies of each seam are at least twice that of the ply with the lowest sulphur content in the seam reflecting the stages in palaeomire development most strongly influenced by sulphate containing waters thorium uranium ratios are below 2 9 in the coal with a marine roof the amman rider seam indicating an enrichment of u from sea water most marked at the top and bottom of the seam the seam without a marine roof shows th u ratios between 2 5 and 4 9 indicating mild marine enrichment of u the concentrations of environmentally significant trace elements eses are correlated with either the ash or sulphur contents or both the correlation between s and pb as cu ni in the coal with a marine roof implies an origin of these eses from sea water and their mode of occurrence in sulphide minerals most eses in this coal are present at levels at least twice that of the global average in coals the exceptions being pb and zn which have concentrations less than half the global average by contrast the coal without a marine roof and with lower sulphur contents has most eses present at concentrations less than a third of the global average the exceptions being ni and cu diagenetic hydrothermal activity is documented in the middle ply of the coal with a marine roof this hydrothermal system redistributed the sulphur pb and as in this ply the principal utilization of bituminous coals in the south wales coalfield is as feed coals in power station boilers the resultant concentration of most eses in the solid residues from power plant coal combustion theoretically can be alleviated by careful blending of feed coals with low and high ese contents

the kerguelen isles southern indian ocean new results on deep structure from refraction profiles abstract additional seismic refraction profiles shot across the kerguelen archipelago terres australes et antarctiques francaises known as taaf located in the southern indian ocean substantiate the oceanic type crust of the archipelago and the kerguelen plateau as well the crust mantle boundary is better modelled by a transition than by a discrete interface seismic velocities of 6 60 6 80 km s are in the range of those within oceanic layer 3 velocities of 7 2 7 5 km s observed at long ranges may be interpreted according to at least two distinct hypotheses 1 1 notwithstanding their rather low values they represent upper mantle material and might be assigned to peridotites serpentinised by hydrothermal circulations as reported for various oceanic and continental features 2 2 these velocities are assigned to the lower crust intruded by melt produced by adiabatic decompression of upper mantle material during rifting underplating a small increase in mantle temperature caused by the presence of heat sources i e the southeast indian ridge and the kerguelen mantle plume nearby may have produced huge quantities of melt facilited by the slow movement of the antarctic plate then building up the aseismic kerguelen plateau

mesozoic reactivation of variscan thrusting in the bristol channel area uk new seismic reflection data from the bristol channel area provide direct evidence of a major variscan thrust in the palaeozoic basement beneath the mesozoic bristol channel syncline the thrust has an average southerly dip of about 25 and it rises into the major fault the central bristol channel fault zone cbcfz at the northern margin of the bristol channel syncline the cbcfz is attributed to reactivation in extension of the variscan thrust probably during the early cretaceous there is no evidence for major synsedimentary movement on the cbcfz and the bristol channel syncline does not represent a rollover structure section restoration suggests that the cbcfz has cut up through a previously tilted sequence of triassic and jurassic strata pervasive nnw sse cross faults are interpreted as original variscan transfer faults that have been reactivated in the mesozoic and tertiary

structure profonde du plateau de madagascar relations avec le plateau de crozet abstract a study of the crust beneath the madagascar ridge and the submarine crozet plateau has established clear similarities between these two structures located in symmetrical positions with respect to the southwest indian ridge seismic refraction interpretation confirms the division of the madagascar ridge in a northern and a southern domain along latitude 31 s no argument in favour of a continental nature of the northern domain can be put forward this domain would rather correspond to a strongly anomalous oceanic crust the deep structure of the southern domain ressembles that of the submarine crozet plateau seismic velocities beneath these two structures are close to those encountered in the oceanic crust the southern domain of the madagascar ridge and the submarine crozet plateau probably have a common origin and were later separated since the early paleocene by spreading from the southwest indian ridge local isostatic equilibrium of the northern domain of the madagascar ridge achieved by crustal thickening is confirmed by gravity models the depth to the moho being close to that deduced from seismic refraction results gravity also confirms that the southern domain is unbalanced with respect to the northern one and to the adjacent oceanic basins

a depositional model for the mid westphalian a to late westphalian b coal measures of south wales mid westphalian a to late westphalian b sediments of the south wales coalfield comprise mainly lacustrine raised mire and flood deposits developed in an upper coastal plain environment occasional high sinuosity fine grained channel systems drained the subdued topography of the wales brabant massif to the north and east of the basin low sinuosity channels with lithic coarse grained fills drained a rising source to the south direct marine influence was restricted to a single marine band facies distributions were controlled by 1 local scale 10 2 10 3 m 2 autocyclic sedimentary processes 2 regional scale 10 km 2 synsedimentary fault activity and differential subsidence and 3 basin wide scale 10 2 km 2 response to changes in relative sea level base level changes are recorded by basin wide bivalve horizons up dip or landward extension of marine bands developed in lacustrine mudstones above basin wide coal seams peat accumulation was terminated by a water table rise related to base level rise following flooding re establishment of the clastic supply resulted in the gradual infilling of the basin wide lake to produce coarsening upwards cyclothems or parasequences a eustatic origin for parasequence development is supported by the development of identical facies associations and parasequences in coeval sediments from the pennine and midland valley coalfields

structure of the kerguelen plateau province from seasat altimetry and seismic reflection data the kerguelen plateau in the southern indian ocean stands 2 4 km above the adjacent sea floor and is 2 500 km long fig 1 1 2 seasat provided a unique data set for deriving the free air gravity field of the region fig 2 3 5 here we report the results of a new analysis of the plateau province s structure employing both seasat and newly acquired multichannel seismic mcs data6 7 for ground truth the northern sector is characterized by volcanism and a sedimentary basin the southern sector by a broad anticlinal arch major faulting and a sedimentary basin and the eastern sector by an abyssal basin labuan and bounding ridge william s the three sectors argue for a more complex tectonic evolution of the feature than has been previously proposed

gps observations of postseismic deformation for the 1995 hyogo ken nanbu earthquake japan 11 months of gps observations which started within 2 days of the 1995 hyogo ken nanbu earthquake detected significant postseismic crustal deformation that reached 20 mm at some stations a comparison of postseismic and coseismic deformation shows a similar pattern in the direction of displacements we tried to determine the predominant relaxation mechanism by examining the time dependence of observed postseismic deformation we considered three models an exponential a power law and a logarithmicaly decaying model however each of these three time dependent models can explain the observed data equally well in case of the exponential relaxation model the relaxation time constant was estimated to be about 50 days in the power law model the index p was nearly 1 0 this is almost the same as the p value of omori s decay law of aftershock sequences for this event this suggests that the mechanism causing postseismic deformation may be related to that producing aftershocks

oceanic mafic granulite xenoliths from the kerguelen archipelago oceanic plateaus are large accumulations of volcanic and plutonic rocks on the ocean floor whose detailed nature and origin are only poorly understood their immense volumes frequent occurrence since the cretaceous period1 and conspicuous presence in all major ocean basins point to their significance in understanding the earth s thermal and chemical evolution we report here the discovery of mafic granulite xenoliths from kerguelen island at the northern end of the kerguelen plateau one of the two largest oceanic plateaus granulites are normally found only in continental settings where the crust is thick enough to experience the high temperatures and pressures required for granulite facies minerals to form we speculate that the kerguelen xenoliths represent basaltic magmas underplated during the evolution of the plateau and more generally that such mafic granulites are an important constituent of the lower parts of oceanic plateaus which are inaccessible by drilling

structural controls on palaeozoic basin evolution and inversion in southwest wales the tectonic evolution of sw dyfed is presented in terms of a model of basin evolution and subsequent destruction by reactivation of the basin bounding faults in contractional mode movements along long lived palaeozoic extensional faults were reversed during variscan compression with the pre existing faults accommodating the contraction in addition to the development of a thin skinned thrust and fold system basin analysis of the pre variscan extensional system uses sedimentological and stratigraphical evidence to constrain the timing of movements of the basin bounding faults thus allowing division of the stratigraphy into depositional megasequences related to these extensional movements field examples on all scales illustrate active extension during the palaeozoic structural cross sections through sw dyfed demonstrate the interrelationship of the extensional and contractional deformations with palinspastic restorations of the cross sections illustrating the complexity of the pre variscan template

major earthquakes occur regularly on an isolated plate boundary fault the scarcity of long geological records of major earthquakes on different types of faults makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult we provide a fault proximal major earthquake record spanning 8000 years on the strike slip alpine fault in new zealand cyclic stratigraphy at hokuri creek suggests that the fault ruptured to the surface 24 times and event ages yield a 0 33 coefficient of variation in recurrence interval we associate this near regular earthquake recurrence with a geometrically simple strike slip fault with high slip rate accommodating a high proportion of plate boundary motion that works in isolation from other faults we propose that it is valid to apply time dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide

syn sedimentary gravity slides growth faults in the coal measures of south wales growth faults are an important class of syn sedimentary fault which have been widely recognized in sub surface studies of hydrocarbon bearing clastic basin successions1 4 they are listric normal faults which are active for a limited period during sediment deposition and therefore affect a discrete sedimentary interval whilst active the faults substantially influence sedimentation and a thicker generally sand dominated succession accumulates on the downthrown side which is consistently towards the basin the faults are not directly related to basement tectonics and instead are thought to originate principally by gravity sliding within the sediment pile5 over pressured undercompacted conditions in buried muds aid development of the faults by reducing the slope required to initiate sliding5 and in some cases associated mud diapirism also contributes by creating steeper slopes6 despite their widespread recognition in sub surface studies relatively few examples have been described from exposed successions7 10 and none from the economically important upper carboniferous coal measures of europe here we describe examples of growth faults recently discovered in an opencast site of the coal measures in south wales and comment on their possible significance

simultaneous reactivation of two subparallel inland normal faults during the mw 6 6 11 april 2011 iwaki earthquake triggered by the mw 9 0 tohoku oki japan earthquake the gigantic m w 9 0 11 march 2011 tohoku oki earthquake suddenly changed the overriding inland area to an extensional stress regime and triggered massive seismic swarms in the coastal region the largest earthquake of m w 6 6 struck southern fukushima on 11 april 2011 and ruptured two previously mapped faults the northwest nw trending yunodake fault and the north northwest nnw trending itozawa fault clear 15 km long and 14 km long surface ruptures appeared along both faults respectively exhibiting a predominantly normal sense of slip down to the west the maximum vertical offset on the yunodake fault is 0 8 m whereas that on the itozawa fault is 2 1 m the itozawa fault rupture is in part marked by uphill facing scarps which is discordant with the large scale topography but consistent with saddled ridges and ponded alluvium the yunodake fault which bounds a neogene half graben structure juxtaposing mesozoic metamorphic rocks against neogene sedimentary rocks shows left lateral deflections of streams seismological data and interviews of local residents revealed that the two subparallel faults ruptured simultaneously based on the location of its hypocenter we however interpret that the itozawa rupture was primary and then triggered normal faulting on the yunodake fault under the heightened coulomb stress caused by the preceding tohoku oki earthquake our paleoseismic trench across the itozawa fault exposed evidence for a penultimate earthquake that occurred sometime between 12 620 and 17 410 cal yr b p there is no evidence that the itozawa fault ruptured during or immediately after the a d 869 jogan earthquake which is believed to be the penultimate giant megathrust earthquake along the japan trench

an interpretation of the variscan structures in sw england the variscan structures in sw england apart from the high level structures in the culm synclinorium of n devon are recumbent with an overall gentle southward dip of cleavages thrusts and recumbent folds translation was towards the nnw the structures are interpreted on a thin skinned model with a basal decollement dipping gently s related to a s dipping subduction zone s of the lizard the granites are thought to have been generated to the s of their present position and injected northwards above the decollement zone

variscan compressional structures within the main productive coal bearing strata of south wales the structure of the main productive coal measures within the anthracite zone in the western part of the south wales coalfield is re examined using data from recently operational opencast coal sites variscan thrusts and or folds and bed parallel shear structures are present within all of the sites studied at east pit unaffected by any large scale zone of disturbance bed parallel shear structures are developed along many of the gently dipping coal seams which form a series of simultaneously active detachments representing a process of easy slip thrusting a ne sw striking fold dominated disturbance at gilfach iago is interpreted to overlie a reactivated basement fault a more complex disturbance zone at ffos las combines both e w trending folds and more variably oriented thrusts which together shorten the coal bearing strata by up to 2 km and this is interpreted to be the major variscan frontal thrust ramp in the extreme west of the coalfield the variscan compressional structures within south wales are not consistent with a simple thin skinned thrust system the strain induced by deep seated variscan thrusts was distributed throughout much of the coal bearing sequence by easy slip deformation rather than being localized along a single regional detachment and additional thrusts present around the northern margin of the coalbasin appear to have formed as isolated autochthonous structures the inherent weakness of coal seams across south wales is attributed to the presence of greatly increased fluid pressures which would have been generated both by the maturing coal and by the influx of fluids along deep seated disturbance zones

p t conditions in the south wales coalfield evidence from coexisting hydrocarbon and aqueous fluid inclusions siderite nodules in the carboniferous coal measures of south wales contain cavities which are often infilled with quartz carbonates sulphides and hydrocarbons the quartz contains a mixture of hydrocarbon and aqueous fluid inclusions the aqueous fluid inclusions consist of a dilute brine 3 wt nacl equivalent and have homogenization temperatures in the range 97 212 oc mean 143 oc the hydrocarbon fluid inclusions are dominated by methane with a small component of higher order hydrocarbons their homogenization temperatures are in the range 35 78 c mean 54 c it is assumed that the two fluids were trapped simultaneously during growth of the quartz and thus a p t estimate of entrapment can be obtained by graphical intersection of the hydrocarbon isochores and the aqueous fluid bubble point homogenization temperatures assuming hydrocarbon saturation this method gives temperatures between 130 and 160 oc and pressures between 40 and 55 mpa the timing of mineralization is uncertain but it is suggested that it took place during burial and low grade metamorphism of the subsiding sedimentary basin i e in the upper carboniferous the hydrothermal fluids were probably derived from evolved meteoric or connate waters expelled during subsidence and sediment compaction

crustal structure of mauna loa volcano hawaii from seismic refraction and gravity data abstract in october 1978 the u s geological survey established a 100 km long seismic refraction profile normal to the kona coast of hawaii island analysis of these data along with available gravity data suggest that the oceanic crust dips about 3 landward under the submerged flank of the island increasing to 8 5 under the kona coast maximum vertical deflection of the base of crust from beneath the deep ocean to a point beneath the summit of mauna loa is about 9 km high velocity high density rocks vp about 7 1 km sec density about 2 9 gm cm 3 comprise the bulk of the volcanic edifice and reach to within a few kilometers of the surface beneath the north flank of mauna loa the data also suggest that an elongate high velocity high density body lies parallel to the kona coast just below the surface this body probably represents an extinct buried rift zone

thrust tectonics deep structure and crustal subduction in the alps and himalayas the structural restoration of collision orogenic belts onto crustal templates provides important insights into the tectonic evolution deep structure and amounts of plate convergence after the initial contact between two continental masses balanced cross sections have been constructed parallel to the local displacement directions across the western alps and western himalayas and demonstrate very large amounts of crustal shortening above intra crustal detachments to achieve a balance substantial volumes of lower crust must have been subducted beneath the two tectonic hinterlands a model of eclogite metamorphism is invoked to facilitate this subduction and to explain the varying isostatic responses of the alpine and himalayan hinterlands patterns of eclogite metamorphism are controlled by the geometry of thrust profiles on a lithospheric scale the development of crust mantle detachments being of crucial importance such a profile is proposed for the himalayas suggesting that relatively small volumes of the footwall crust succumbed to eclogite metamorphism in the alps however a steeper thrust profile apparently developed emplacing mantle onto crust causing wholescale eclogite metamorphism in the underlying franco swiss crust the resultant density increase would provide a mechanism of isostatic collapse and flexural subsidence in the po plain region

damage to the shallow landers fault from the nearby hector mine earthquake crustal faults have long been identified as sites where localized sliding motion occurs during earthquakes which allows for the relative motion between adjacent crustal blocks although there is a growing awareness that we must understand the evolution of fault systems on many timescales to relate present day crustal stresses and fault motions to geological structures formed in the past fault zone damage and healing have been documented quantitatively in only a few cases we have been monitoring the healing of damage on the shallow johnson valley fault after its rupture in the 1992 magnitude 7 3 landers earthquake and here we report that this healing was interrupted in 1999 by the magnitude 7 1 hector mine earthquake rupture which occurred 20 30 km away the hector mine earthquake both strongly shook and permanently strained the johnson valley fault adding damage discernible as a temporary reversal of the healing process the fault has since resumed the trend of strength recovery that it showed after the landers earthquake these observations lead us to speculate that fault damage caused by strong seismic waves may help to explain earthquake clustering and seismicity triggering by shaking and may be involved in friction reduction during faulting

subsidence associated with the lusi mud eruption east java investigated by sar interferometry abstract a mud volcano lusi initiated its eruption on 29 may 2006 adjacent to a hydrocarbon exploration well in east java ground subsidence in the vicinity of the lusi eruptive vent was well recorded by a synthetic aperture radar sar palsar onboard the japanese alos satellite we apply an interferometric sar insar technique on ten palsar data scenes acquired between 19 may 2006 and 21 may 2007 in order to obtain continuous maps of ground displacements around lusi although the displacements in the area closest to the eruptive vent spatial extension of about 1 5 km are not detectable because of the erupted mud all the processed interferograms indicate subsidence in an ellipsoidal area of approximately 4 km north south 3 km east west centered at the main eruptive vent in particular interferograms spanning the first four months until 4 oct 2006 and the subsequent 46 days between 4 oct 2006 and 19 nov 2006 show at least about 70 cm and 80 cm of displacements away from the satellite respectively possible causes of the subsidence i e 1 loading effect of the erupted mud 2 creation of a cylindrical mud conduit and 3 pressure decrease and depletion of materials at depth are investigated the effects of the first two causes are found to be insufficient to explain the total amount of subsidence observed in the first six months the third possibility is quantitatively examined using a boundary element approach by modeling the source of deformation as a deflating oblate spheroid the spheroid is estimated to lie at depths of a few hundred to a thousand meters the estimated depths are significantly shallower than determined from analyses of erupted mud samples the difference is explained by presence of significant amount of inelastic deformation including compaction and downward transfer of material

mechanisms of coal metamorphism case studies from paleozoic coalfields controls on coal metamorphism can be complex in this paper we examine four paleozoic coalfields the western kentucky portion of the illinois basin the pennsylvania anthracite fields the south wales coalfield and the bowen basin an increase in temperature with depth of burial is certainly a factor in coal metamorphism in many coalfields however including the coalfields reviewed here it has become apparent that such a simple mechanism does not explain the coal rank patterns observed the flow of hydrothermal fluids through the coals has been proposed as a cause of coal metamorphism evidence includes inverted rank gradients elevated cfl as an indicator of brine fluids isotopic evidence for hydrothermal fluids and vein and cleat mineral assemblages in any case multiple hypotheses must often be evaluated in the examination of any coalfield since the simple paradigm of coal rank increases with a simple increase in temperature with increasing depth does not fit the evidence observed in many cases

inverting for slip on three dimensional fault surfaces using angular dislocations the increasing quality of geodetic data synthetic aperture radar interferometry insar dense global positioning system gps arrays now available to geophysicists and geologists are not fully exploited in slip inversion procedures most common methods of inversion use rectangular dislocation segments to model fault ruptures and therefore oversimplify fault geometries these geometric simplifications can lead to inconsistencies when inverting for slip on earthquake faults and they preclude a more complete understanding of the role of fault geometry in the earthquake process we have developed a new three dimensional slip inversion method based on the analytical solution for an angular dislocation in a linear elastic homogeneous isotropic half space the approach uses the boundary element code poly3d that employs a set of planar triangular elements of constant displacement discontinuity to model fault surfaces the use of triangulated surfaces as discontinuities permits one to construct fault models that better approximate curved three dimensional surfaces bounded by curved tiplines shapes that commonly are imaged by three dimensional reflection seismic data and inferred from relocated aftershock data we demonstrate the method s ability to model three dimensional rupture geometries by inverting for slip associated with the 1999 hector mine earthquake the resulting model avoids displacement anomalies associated with the overlapping rectangular dislocations used in previous models improving the fit to the geodetic data by 32 and honors the observed surface ruptures thereby allowing more direct comparisons between geologic and geodetic data on slip distributions online material hector mine input files and file format description

a mountain front model for the variscan deformation of the south wales coalfield access to the considerable geological database of british coal together with seismic evidence of subsurface relationships has enabled the development of a structural model for the south wales coalfield detailed site investigations are used as key examples the simple broad synclinal nature of the coalfield masks a more complex structural system thrusting of variscan age is largely confined to the lower and middle coal measures and throughout the central and northern coalfield is dominantly a forethrust system however along the south crop a major backthrust system is developed which in places penetrates the upper coal measures the south crop shows features analogous with a mountain front and is interpreted as a triangle zone in which pre existing basement faults have facilitated uplift the lack of thrusting within the upper coal measures in contrast to the underlying lower and middle coal measures suggests they have acted as a passive roof to the thrust system geographical variation in the intensity of the deformation can be related to the proximity of and buttressing against the caledonian massif although broadly analogous with current models of foreland basin development and deformation the south wales coalfield demonstrates the importance of pre existing massifs and lineaments in determining the precise evolution of an area

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

contribution a l etude de la structure profonde du banc de crozet ocean indien austral abstract the crozet bank the eastern part of the crozet plateau southern indian ocean is capped by two groups of islands that form the crozet archipelago terres australes et antarctiques francaises a n s trending 1500 m deep basin the indivat basin cuts the crozet bank between the two island groups into two parts bearing different geological and volcanic characteristics in the west a 2 5 km thick basalt layer indicating well developed volcanism and in the east a thin basalt layer and layer 3 just below a detrital layer such an arrangement may resemble that observed in oceanic structures where serpentinized peridotites have been cored just below the sediments the interpretation of gravity anomalies on ile aux cochons and ile de la possession combined with marine geophysical data collected in the surrounding regions of the southern indian ocean shows that the crustal thickening observed below the crozet bank is caused by a 12 km thick layer 3 which precludes local airy type compensation of the crozet bank the isostatic compensation of the crozet bank is mainly achieved by lower density material within the upper mantle down to a depth of 50 km the compensation level is 60 km deep a long wavelength heat flow anomaly observed over the eastern region of the crozet plateau indicates that the lower density of the upper mantle is of deep thermal origin within the lithosphere

complex ruptures of the 11 april 2011 mw 6 6 iwaki earthquake triggered by the 11 march 2011 mw 9 0 tohoku earthquake japan abstract after the 11 march 2011 m w 9 0 tohoku earthquake japan a swarm of shallow normal faulting earthquakes was triggered in a localized region beneath the border between fukushima and ibaraki prefectures in eastern honshu here we examine the coseismic displacement field and a fault model of the largest event of the swarm the 11 april 2011 m w 6 6 iwaki earthquake radar interferometry applied to data of the japanese alos satellite reveals complex ruptures associated with the iwaki earthquake in particular the interferogram clearly shows multiple surface ruptures along each of the subparallel yunodake and itozawa faults the slip distributions on these faults as estimated by inverting the interferogram suggest that the faults dip 60 70 westward and that slip on the itozawa fault extended to a splay fault at depths shallower than about 5 km our results indicate that the highland area west of the itozawa fault was downthrown by up to 2 4 m during the iwaki earthquake online material original and de trended interferograms over a wider area

correction for interferometric synthetic aperture radar atmospheric phase artifacts using time series of zenith wet delay observations from a gps network 1 radar interferograms provide precise millimeter level measurements of crustal deformation at fine resolution over wide areas the dominant error source in many interferograms results from spatial heterogeneity of the wet component of atmospheric refractivity resulting in excess path length of the radar signal propagating through the neutral atmosphere in this report we introduce a method to compensate for atmospheric phase artifacts in a radar interferogram using spatially interpolated zenith wet delay zwd data obtained from a network of global positioning system gps receivers in the region imaged by the radar our method based on taylor s frozen flow hypothesis uses gps data recorded prior to and after the individual radar acquisition times to infer denser spatial networks of control points for interpolation than is suggested by the sparse and irregular spatial distribution of gps receivers we test this approach by correcting phase fluctuations observed in a radar interferogram over an area covered by the southern california integrated gps network stations using maps of atmospheric delay interpolated from the denser network of gps zwd measurements generated by our method we find that the largest improvement results from removing an altitude dependent model derived from the gps data the uncorrected interferogram in our example has an rms fluctuation of 16 1 mm which falls to 8 6 mm after the altitude correction a map derived from zwd measurements recorded only at the instances of radar acquisition reduced overall fluctuations in the data from 8 6 to 8 1 mm rms while using the inferred denser network reduces the error further to 7 5 mm rms most of this residual variation is due to decorrelation of the signal and does not result from atmospheric propagation however after smoothing to remove decorrelation noise the residual drops from 4 7 to 3 9 mm gps stations only and then to 2 7 mm rms when the denser network algorithm is used

finding realistic dike models from interferometric synthetic aperture radar data the february 2000 eruption at piton de la fournaise dike intrusions often cause complex ground displacements that are not sufciently explained by simple analytical models we develop a method to nd complex and realistic dike geometries and overpressures from interferometric synthetic aperture radar insar data this method is based on a combination of a boundary element method with realistic topography and a neighbourhood algorithm inversion dike model geometry is roughly a quadrangle with its top reaching the ground the inversion has two stages search and appraisal the appraisal stage involves calculations of model marginal probability density functions using mist val ues calculated during the search stage the mist function takes into account the variance and correlation of data noise synthetic tests show that a model is successfully retrieved within predicted narrow condence intervals we apply the method on insar data of the february 2000 ank eruption at piton de la fournaise and get a trapezoid dike dipping seaward 61 0 n 67 3 with its bottom passing 800n1000 m beneath the summit a model with a basal slip plane does not better explain observed asymmetric displacements and thus this asymmetry is solely attributed to the dipping dike the dike lies above a narrow band of pre eruption seis micity suggesting that lateral magma propagation occurred neglecting topography results in poor modeling at depth and in overestimations of overpressure or opening height both about 30 and volume about 20

the association between tectonic deformation inorganic composition and coal rank in the bituminous coals from the south wales coalfield united kingdom analysis of vertical distribution of coal rank in three collieries and one opencast mine in the se of the south wales coalfield has revealed deviations from hilt s law in both proximate analyses and in vitrinite reflectance the variations in rank parameters studied are closely correlated with variations in the intensity of tectonic deformation measured using a numerical deformation index ndi three seams in the sequence were also analysed for major and trace element geochemistry and rock eval pyrolysis variations in these parameters are related to thrust inclusion of floor and or roof mudrocks into the seams a detailed conceptual model of a major thrust and associated in seam thrust detachments and lag faults is developed to explain the vertical rank profile by post coalification faulting it is concluded that although the model can explain the vertical pattern of rank the complexity of the required faults render the model improbable the alternative mechanisms for enhancement of the rank parameters associated with tectonic deformation including shear stress control frictional heating and localised fluid flow are discussed and are thought more likely to be responsible for the deviations from hilt s law in the vertical rank profile rank suppression shown by three seams two of which are overlain by marine bands is thought to be related to biochemical activity in the peat environment resulting from the influx of saline waters

lateral variation of the cutoff depth of shallow earthquakes beneath the japan islands and its implications for seismogenesis abstract we estimated the spatial distribution of the cut off depth of shallow seismicity beneath the japan islands based on data from a recently constructed nationwide dense seismic network in order to avoid the effect of heterogeneous seismic velocity structure we determined the 3d seismic velocity structure for the whole of japan which was then used to relocate the hypocenters the cut off depth was determined by calculating d90 the depth above which 90 of the earthquakes occur a spatial distribution of estimated d90 values shows a considerable lateral variation ranging from about 5 km to about 40 km the d90 s are deep along the pacific coast of eastern japan locally shallow d90 s extend along belt like stretches of volcanic areas heat flow is low along the pacific coast in eastern japan and high in the volcanic areas this indicates that the lateral variation of d90 s is formed mainly by lateral geotherm variation cooling by the subducting old very cold pacific plate may cause the deep d90 s along the pacific coast in eastern japan heating by magma supplied from the mantle wedge below is considered to be the main cause of the shallow d90 s in the volcanic areas magma and or aqueous fluids derived from solidified magma contribute not only to locally shallow d90 s but also to the weakening of ambient rocks in the lower crust resulting in stress concentrations in the upper crust just above them large shallow inland earthquakes tend to occur in such areas suggesting that a model of shallow earthquake generation applied to tohoku can be used in other areas in japan as well

a seismic refraction survey in the kerguelen isles southern indian ocean summary two 65 km long on land refraction lines with shot detonated at sea were implemented in the courbet peninsula eastern region of the kerguelen archipelago terres australes et antarctiques francaises southern indian ocean the first profile pi oriented ne sw runs from cap ratmanoff toward mont ross and the second one p2 from pointe suzanne se of the courbet peninsula through the val studer data from both profiles were supplemented by using the bouguer gravity anomaly map not previously studied the data combined standard travel time interpretation wide angle reflected wave study synthetic seismograms and s wave analysis the velocity depth behaviour shows that the mean crustal thickness ranges from 14 to kerguelen resembles those observed beneath aseismic ridges i e the crozet rise and the madagascar ridge average velocity of 5 5 km s on both lines is in the range of those determined for oceanic layer 2 which is there 8 9 km thick average velocity of 6 6 km s is in the range of velocities within oceanic layer 3 the transition to mantle velocity 7 95 km s is best modelled by a positive velocity gradient within the crust this feature is similar to that observed on structures generated near spreading centres these new data com bined with geological and geochemical investigations in the archipelago support an oceanic origin for the kerguelen heard ridge and also broken ridge both structures were joined 40myr ago as shown by the magnetic anomaly pattern refraction studies invalidate the assumption that isostatic compensation is achieved by a 23 km deep crustal root but substantiate the i 17km only varying with the locality the structure of the crust beneath

a model for the development of the irish variscides a clear correlation exists in the southern irish variscides between extensional structures which controlled late palaeozoic sedimentation in the munster basin and contractional thrusts and folds of end carboniferous age this correlation is interpreted to indicate that the extensional structural framework of the basin including a basal low angle detachment and an array of superjacent normal faults was reused during transpressive inversion of the basin to produce the fold thrust belt the extensional framework which in turn was to some extent derived by reactivation of caledonian structures therefore exerted a fundamental control on the geometry and style of contractional deformation it is not evident that the detachment had a discrete link to the fold belt in south wales or the main variscan orogen in europe

the structure of mountain fronts commonly the part of a mountain front which is visible at the surface consists of foreland dipping thrust belt rocks elevated above their regional structural position and overlain more or less conformably by molasse several explanations for their geometry are possible 1 major detachments exist within or beneath the molasse resulting in transport of the foreland basin examples of this geometry come from the swiss molasse plain the southern pyrenees and the mackenzie mountains of canada 2 displacement is lost on major backthrusts beneath the frontal monocline examples cited here are the rockies of alberta the sulaiman ranges of pakistan the mackenzies and the andes in peru 3 thrust sheets travelled over an old land surface and syntectonic molasse contemporaneously offlaps the topographic high of the thrust front this phenomenon occurs along the alpine thrust front in haute provence 4 the frontal fold represents deformation above a large scale thrust tip no unequivocal example of tip line strain at this scale has been recorded although this type of deformation may occur in the brooks range of alaska in many areas mountain fronts show a combination of these idealized geometries

the confrontation of structural styles and the evolution of a foreland basin in central sw england detailed mapping of the rocks to the north and south of plymouth reveals a sedimentary sequence deformed by a series of folds and thrusts two structural zones exist each with a different style of deformation in the lower to upper devonian rocks of the southern zone slip vectors vergence and facing of d1 folds indicate that the transport direction is to the north west an associated first phase cleavage dips to the south east the northern zone of upper devonian and lower carboniferous strata extends into central devon and east cornwall and the geometry and facing of the early folds in these rocks indicate a transport direction to the south or south east d1 folds generally verge north but are downward facing towards the south a flat lying penetrative slaty cleavage occurs in the mudrocks and also indicates southward facing generally the carboniferous rocks in this area are inverted the two structural zones confront each other at an e w trending line which passes through cargreen 8 km north of plymouth here the deformation is more intense as the cleavage common to the southern zone overprints that of the northern zone resulting in the formation of d2 folds the confrontation is interpreted as a northerly dipping backthrust produced by large scale underthrusting it is proposed that the northward advancing variscan thrust belt progressively underthrust the carboniferous foreland basin flysch deposits which became inverted and backthrust towards the south

common ground between two british pennsylvanian wetland floras using large first hand datasets to assess utility of historical museum collections abstract studies on the macrofloral record of the pennsylvanian palaeotropical peat forming wetlands coal swamps depend heavily on historical collections in museums this paper examines the robustness of such collections for macrofloral studies 110 000 individually recorded specimens from south wales field collected by david davies during the early 20th century were compared with the 6500 museum voucher specimens derived from them eventually intended for a representative teaching collection this showed that the voucher collections accurately reflect the order of abundances of the plant groups as documented in the field records but not their actual numerical abundances these welsh data were then compared with the available museum collections for similar aged macrofloras in the nearby bristol somerset coalfield cluster analyses and detrended correspondence analyses were performed 1 on the raw data recorded on the museum labels 2 on standardised data that were updated to reflect the currently accepted taxonomy for these fossils and 3 on standardised data in which single occurrences of taxa have been removed the results suggest that unstandardised museum collection data can reveal meaningful biostratigraphical and biogeographical patterns but that these become clearer with the standardised data the effect of removing the singleton taxa was less clear although it did provide a slightly enhanced resolution with cluster analysis whilst previous studies have considered these to be separate basins with the bristol somerset coalfield being proximal to south wales on the mid pennsylvanian variscan front results show an overall consistency between the two basins and suggest a common gene pool and vegetational physiognomy as well as a general stasis through time based on relatively stable environmental and growth conditions the study confirms that even unrevised historical collections can provide some data to help understand the dynamics of these systems however it also underlines the importance of taxonomy in such studies as it helps improve both the biostratigraphical and biogeographical resolution

the south wales coalfield low grade metamorphism in a foreland basin setting the south wales coalfield comprises namurian westphalian and stephanian sequences which developed in the external zone of the variscan orogenic belt sedimentation is thought to have been concentrated in a paralic basin related to crustal flexure in a foreland basin setting linked to variscan tectonic loading to the south it has long been recognized that coal rank varies across the coalfield from high volatile bituminous rank in the east and southeast to anthracite in the northwest this is confirmed here on the basis of comprehensive volatile matter and vitrinite reflectance data sets computer contoured to generate isovol and isoreflectance maps a steady increase in coalification with depth is also recorded clay mineral investigations show the presence of illite and kaolinite across the entire coalfield area while neither pyrophyllite nor mixed clays were detected illite crystallinity values from mudstones are in the range 1 20 0 44 2 vitrinite reflectance data indicate maturation temperatures in the range 123 290 c clay mineral and ic values suggest temperatures up to 230 c while previous descriptions of pyrophyllite from the coalfield would allow locally for even higher temperatures coalification appears to have occurred rapidly maximum 5 ma following deposition implying high heat flux during westphalian times this is also indicated by fluid inclusion evidence from quartz crystals in clay ironstone nodules the inference is of a high geothermal gradient c 50 c km 1 during westphalian times contrasting with an earlier gradient estimate of 20 37 c km 1 relatively high gradients have also been determined previously for the ruhr coalfield which occupies a similar tectonic setting in the external zone of the variscan orogenic belt such a gradient is at odds with the proposed foreland basin tectonic setting for the south wales coalfield in which low geothermal gradients would be anticipated

late carboniferous tectonic subsidence in south wales implications for variscan basin evolution and tectonic history in sw britain detailed stratigraphic data have been used to backstrip seven sections from the carboniferous south wales coal basin resulting tectonic subsidence curves for the interval 319 305 ma namurian westphalian d are convex up indicating increasing subsidence rate with time with rates between 130 and 250 m ma 1 suggesting a foreland basin setting forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north northeasterly direction across sw england between 319 and 305 ma could have generated the backstripped subsidence patterns sensitivity tests show that while many of the forward model parameters are poorly constrained and the model results non unique backstripped subsidence patterns allow reasonable constraint on the different model cases so that model predictions can be treated as one possibility in a limited range the predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of sw england these results suggest that subsidence in other late carboniferous uk basins may also have been influenced by flexure due to a propagating orogenic load

the woolhope and usk basins silurian rift basins revealed by subsurface mapping of the southern welsh borderland subsurface mapping of the southern welsh borderland has utilized over 600 km of seismic data and three exploration boreholes to investigate the subsurface of this classic geological area the survey reveals two silurian basins each about 400 km 2 in area in the western part of the midland platform the woolhope basin underlies the silurian inlier of the woolhope anticline the basin fill is bounded to the northwest by faults of the neath disturbance and was also influenced by wnw striking extensional growth faults the fill thins eastward towards the malvern line lower silurian sequences thin southward before thickening again particularly across wnw striking faults the resulting usk basin underlying the usk inlier has ill defined margins but some additional n s fault control the fownhope 1 and usk 1 wells indicate that rapid subsidence occurred in both basins during rhuddanian and aeronian early to mid llandovery time modelling of this subsidence assuming the finite duration lithospheric extension model yields stretching factors of between 1 3 and 1 6 the later part of the fill to both basins is marine but red conglomerates sandstones and mudstones in their early llandovery intervals suggest continental fluvial environments in the initial stages of basin development the woolhope and usk basins show that the western sector of the midland platform rifted during early to mid llandovery time perhaps during regional dextral transtension the rifting is synchronous with and perhaps genetically related to an episode of mafic volcanism in the southwest part of the platform however this rifting apparently predates the late llandovery telychian fault controlled subsidence seen in the welsh basin to the northwest

mechanical and thermal isostatic response of the del cano rise and crozet bank southern indian ocean from altimetry data an analysis of the relationship between the bathymetry and the gravity field has been carried out both in the frequency domain admittance technique and in the space domain over the del cano rise and the crozet bank southern indian ocean a bathymetric map contoured from original shipboard data and a geoid anomaly map computed from a merged set of seasat and geos3 data were used the inversion of admittances for water depth crustal thickness crustal density and elastic plate thickness shows that the isostatic response of the lithosphere supporting the del cano rise differs very much from that of the one situated beneath the crozet bank the del cano rise appears to have been formed near the active southwest indian ridge before early eocene and is locally supported by a thickened crust shallow thermal processes contribute to the present topography of the crozet bank emplaced further away from the southeast indian ridge on older crust

widespread seismicity excitation throughout central japan following the 2011 m 9 0 tohoku earthquake and its interpretation by coulomb stress transfer 1 we report on a broad and unprecedented increase in seismicity rate following the m 9 0 tohoku mainshock for m 2 earthquakes over inland japan parts of the japan sea and izu islands at distances of up to 425 km from the locus of high 15 m seismic slip on the megathrust such an increase was not seen for the 2004 m 9 1 sumatra or 2010 m 8 8 chile earthquakes but they lacked the seismic networks necessary to detect such small events here we explore the possibility that the rate changes are the product of static coulomb stress transfer to small faults we use the nodal planes of m 3 5 earthquakes as proxies for such small active faults and find that of fifteen regions averaging 80 by 80 km in size 11 show a positive association between calculated stress changes and the observed seismicity rate change 3 show a negative correlation and for one the changes are too small to assess this work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there which is likely quite common

volcano wide fringes in ers synthetic aperture radar interferograms of etna 1992 1998 deformation or tropospheric effect mount etna 3300 m is the volcano that has been first and most studied by differential synthetic aperture radar previous papers gave evidence for a large scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models also atmospheric effects on mountainous areas are known to be very significant accordingly interferograms may reflect both deformation and tropospheric effects we investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms from 38 ers synthetic aperture radar ascending scenes taken from 1992 to 1999 we have computed 238 interferograms the amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters from a simple analysis of phase elevation relation we give evidence for the clear difference in pattern between stratified tropospheric effects and large scale deformation produced by a source in a three dimensional elastic body with topography using combination of inversion processes we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms finally time evolution of the parameters and modeling probability estimation are retrieved for each sar image estimated relative change in tropospheric delay varies in time from 2 7 to 3 0 1 2 fringes they are consistent with other tropospheric estimations at etna based on ground met and global positioning system observations on the same period of time magmatic volume variations remain below error bars and thus cannot be estimated properly finally some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods without the need to invoking a deformation of the volcano

the westphalian stephanian macrofloral record from the south wales coalfield uk the south wales coalfield has the most complete westphalian macrofloral record anywhere on the variscan foreland or adjacent basins with 135 biodiversity meaningful morphospecies having been recognized all of the standard macrofloral biozones of the westphalian stage have been recognized although a detailed comparison with the central pennines coalfields has indicated some discrepancies in the relative positions of the biozonal boundaries total species richness progressively increases through the langsettian substage and then remains relatively stable through most of the duckmantian and bolsovian substages there is a distinct reduction in total species richness towards the top of the bolsovian substage but this partially recovers in the middle asturian substage with the appearance of a range of marattialean ferns and medullosalean and callistophytaleans pteridosperms there is no evidence of any significant drop in total species richness towards the top of the succession indicating that conditions at this time were relatively stable the change from coastal floodplain to alluvial braidplain conditions in middle bolsovian times correlates with a marked increase in the proportion of medullosalean remains being preserved in the adpression record reflecting an expansion of the clastic substrate habitats