continental scale salt tectonics on mars and the origin of valles marineris and associated outflow channels a synthesis of deformation patterns within and around the thaumasia plateau mars points to a new interpretation for regional deformation and the origin of valles marineris and associated outflow channels the morphology of the thaumasia plateau is typical of thin skinned deformation akin to a mega slide in which extensional deformation in syria planum and noctis labyrinthus connects via lateral zones of transtension and strike slip claritas fossae and valles marineris to a broad zone of compressional uplift and shortening defined by truncated craters and thrust faults along the coprates rise and thaumasia highlands however the low regional slope 1 results in gravitational body forces that are too small to deform the basaltic lava flows conventionally thought to compose the flanks of the tharsis volcanic province instead we conclude that geothermal heating and topographic loading of extensive buried deposits of salts and or mixtures of salts ice and basaltic debris would allow for weak detachments and large scale gravity spreading we propose that the generally linear chasmata of valles marineris reflect extension collapse and excavation along fractures radial to tharsis either forming or reactivated as part of one lateral margin of the thaumasia gravity spreading system the other dextral lateral margin is a massive splay of extensional faults forming the claritas fossae which resembles a trailing extensional imbricate fan the compressional mountain belt defined by the coprates rise and thaumasia highlands forms the toe of the mega slide topographic observations and previous structural analyses reveal evidence for a failed volcanic plume below syria planum that could have provided further thermal energy and topographic potential for initiating regional deformation either intrusively through inflation or extrusively through lava flow and or ash fall emplacement higher heat flow during noachian time or geothermal heating due to burial by tharsis derived volcanic rocks would have contributed to flow of salt deposits as well as formation of groundwater from melting ice and dewatering of hydrous salts we further propose that connection of overpressured groundwater from aquifers near the base of the detachment through the cryosphere to the martian surface created the outflow channels of echus coprates and juventae chasmata at relatively uniform source elevations along the northern margin of the mega slide where regional groundwater flow would have been directed toward the surface our hypothesis provides a unifying framework to explain perplexing relationships between the rise of the tharsis volcanic province deformation of the thaumasia plateau and the formation of valles marineris and associated outflow channels

use of ground probing radar and resistivity surveys for archaeological investigations in japan geophysical methods are normally used to estimate the distribution of cultural relics before digging objects of archaeological interest are usually located within a few meters of the surface therefore geophysical methods suitable for archaeological exploration are those which provide high resolution at shallow depths the most commonly used geophysical methods are ground probing radar resistivity and magnetometry of these methods we used mainly ground probing radar and resistivity surveys in archaeological investigations at four sites three of the sites were in gumma prefecture japan they were covered with volcanic deposits loam or pumice using ground probing radar we were able to locate ancient dwellings burial mounds and a distribution of archaeologically significant culture layers at the other site in nara prefecture we located part of the remains of an ancient city in this investigation the resistivity method and ground probing radar were combined to determine the loc

compression of oceanic lithosphere an analysis of intraplate deformation in the central indian basin intraplate compressional deformation in the central indian basin is expressed as linear e w trending topographic undulations and geoid anomlies with characteristic spacings of approximately 200 km to elucidate the nature of this deformation we develop models of an oceanic lithosphere in a state of horizontal compression the lithosphere is treated as a viscous or plastic layer of uniform strength which overlies a viscous half space in which strength decreases exponentially with depth we compare models in which deformation with a dominant wavelength develops in response to flexural buckling and the hydrodynamic growth of instabilities for the viscous flexural buckling model deformation is constrained to occur in the antisymmetric mode by flexural folding which is characterized by uniform bending of the layer in the hydrodynamic flow model a range of deformational styles are possible in a strong viscous lithosphere deformation of the layer occurs by flexural folding at a wavelength which agrees with that predicted from flexural buckling theory in a lithosphere of intermediate strength the layer deforms by folding characterized by thickening which localizes beneath topographic highs in a relatively weak lithosphere the layer incurs an even greater amount of localized thickening and deforms in the symmetric or pinch and swell mode by inverse boudinage if the layer has a plastic rheology deformation occurs by inverse boudinage independent of the yield stress results from models in which the layer folds either flexurally or with periodic thickening are consistent with the observed depth distribution of seismicity in the central indian basin and with experimental rock rheological data because of the trade off between buoyancy forces and layer strength in determining the dominant wavelength a lithosphere which was overlain by weak sediments when intraplate deformation initiated can be characterized by a compressive layer strength almost a factor of 3 less than a lithosphere which was initially sediment free for a range of plausible models which consider both a sediment covered and sediment free lithosphere the observed wavelength requires deviatoric stresses in the indian plate of several hundreds of mpa

aquisgrani terrae motus factus est part 1 the aachen cathedral germany built on weak ground charlemagne charles the great placed the centre of his kingdom during carolingian times in aachen germany aquisgrana this medieval period and his regency are associated with a period of extensive constructions in aachen including the carolingian part of the aachen cathedral the cathedral was the first building in germany to join the unesco world heritage list the foundations and construction ground of the cathedral were excavated during recent archaeological and geotechnical investigations the cathedral is founded on pillars and piles in devonian blue limestone and shale covered by pleistocene loess sediments remains of roman buildings such as thermae are situated below this part of the cathedral the pillars are connected by up to 5 m deep foundation walls and are up to 2 4 m thick even though information about the construction site is important for the assessment of structural health and remediation measures it is often rare for old historical buildings documentations from construction time concentrate on the construction progress and financial aspects detailed descriptions on the foundation ground and techniques are usually not preserved this information is of relevance for assessment of earthquake related structural damages and site effects on construction investigations in the course of remediation measures or archaeological surveys fill this information gap they provide insights in the ancient foundation techniques and can be used for identifying earthquake related phenomena in the construction site furthermore a direct insight into potential seismic effects associated with the ground and building response on seismic shaking becomes possible in the case of the aachen cathedral typical geotechnical investigation methods including drilling and laboratory tests were applied together with gpr measurements to evaluate the construction ground and evaluate potential seismological effects

constraints on the lithospheric structure of venus from mechanical models and tectonic surface features radar images of the surface of venus show numerous structures that are interpreted as having formed due to horizontal compression and extension of the lithosphere many of these features exhibit characteristic scales widths or spacings of deformation one of 10 20 km and another of 100 300 km for a range of simple models we test the hypothesis that these length scales are controlled by dominant wavelengths arising from unstable compression or extension of the venus lithosphere results show that the existence of tectonic features that exhibit both length scales can be explained if at the time of deformation the lithosphere consisted of a crust that was relatively strong near the surface and weak at its base and an upper mantle that was stronger than or of nearly comparable strength to the upper crust the spacings of these features imply crustal thicknesses in the approximate range 5 30 km and a thermal gradient not greater than 25 k km 1 features that exhibit only the smaller scale of deformation can be explained by either a lithosphere with a thick crust that overlies a weak mantle or a lithosphere with a strong mantle but with small internal strength contrasts for a broad range of parameters the models require not only that smaller scale compressional and extensional features have similar spacings but also that the widths and spacings of larger scale compressional features be greater than those formed in extension this is consistent with observed differences in the characteristic length scales of larger scale surface features as well as the similarities in spacings of observed smaller scale features

integrated data analysis at an archaeological site a case study using 3d gpr magnetic and high resolution topographic data we have collected magnetic 3d ground penetrating radar gpr and topographic data at an archaeological site within the palace garden of paretz germany the survey site covers an area of approximately 35 40 m across a hill structure dips of up to 15 that is partly covered by trees the primary goal of this study was to detect and locate the remains of ancient architectural elements which from historical records were expected to be buried in the subsurface at this site to acquire our geophysical data we used a recently developed surveying approach that combines the magnetic and gpr instrument with a tracking total station tts besides efficient data acquisition this approach provides positional information at an accuracy within the centimeter range at the paretz field site this information was critical for processing and analyzing our geophysical data in particular gpr data and enabled us to generate a high resolution digital terrain model dtm of the surveyed area integrated analysis a

assessment of global and regional tectonic models for faulting in the ancient terrains of mars structural landforms within parts of the heavily cratered terrain of mars were studied in order to test various models of global fracturing landforms analyzed were scarps grabens simple ridges and channel wall scarps many of these landforms predate graben formation in tharsis very few structural landforms were found to be either radial to tharsis or normal to principal stress trajectories calculated for tharsis isostasy or flexural loading these results suggest either that the structures are locally derived or if they were produced by tharsis activity that the state of stress in tharsis was different from that which produced the classic graben systems association of narrow valley networks with subdued grabens in one portion of margaritifer sinus suggests that one episode of narrow valley formation coincided with flexural loading in tharsis crustal fracturing in oxia palus that predates outflow channel formation does not correlate with tharsis tectonism and may reflect fracturing by the proposed chryse multiring basin to the north in contrast to previous studies no evidence was found for either an orthogonal martian grid or conjugate sets of shear fractures it is concluded that mars probably did not experience significant tidal despinning calculations of thermal stress within a cooling early lithosphere performed for varying lithospheric thicknesses predict large scale tensile near surface failure many of the large ridges in memnonia that predate classical tharsis centered tectonism may reflect normal faulting generated in part by thermal stress

dust and ice deposition in the martian geologic record abstract the polar layered deposits of mars demonstrate that thick accumulations of dust and ice deposits can develop on the planet if environmental conditions are favorable these deposits appear to be hundreds of millions of years old and other deposits of similar size but of greater age in nonpolar regions may have formed by similar processes possible relict dust deposits include from oldest to youngest noachian intercrater materials including arabia mantle deposits noachian to early hesperian south polar pitted deposits early hesperian hellas and argyre basin deposits late hesperian electris deposits and the amazonian medusae fossae formation these deposits typically are hundreds of meters to a couple kilometers thick and cover upward of a million or more square kilometers the apparent persistence of dust sedimentation at the south pole back to the early hesperian or earlier and the early growth of tharsis during the late noachian and perhaps earlier indicates that extensive polar wandering is unlikely following the middle noachian a scenario for the overall history of dust and perhaps ice deposition on mars includes widespread voluminous accumulations perhaps planetwide during the noachian as impacts volcanism and surface processes generated large amounts of dust the arabia deposits may have formed as ice availability and dust accumulation waned during the early hesperian thick dust sedimentation became restricted to the south pole and the deep hellas and argyre basins the north polar sedimentary record prior to the amazonian is largely obscured deposits at electris and medusae fossae may have resulted from local sources of fine grained material perhaps volcanic eruptions

determination of electrical properties of the ground at shallow depth with an electrostatic quadrupole field trials on archaeological sites1 knowledge of both the electrical resistivity and the dielectric permittivity of the ground is important for the determination of characteristics such as granularity porosity moisture and salt content whereas the measurement of is very common and can be achieved using either the d c resistivity method or a wide variety of em devices remains practically unknown in the low frequency domain between the ip domain and the high frequency domain following the principle of the quadrupole technique used in d c prospecting and of the quadrupolar probe for measuring the complex permittivity of the ionosphere we propose a new approach which does not require any galvanic contact between the poles and the ground the transfer impedance can be evaluated using the quasi static approximation for low frequency or the full em theory for higher frequencies the conditions under which both calculations apply are discussed at low frequencies and for low resistivity ground the electrostatic quadrupole measures exactly as with the d c technique for higher resistivities or frequencies the simultaneous measurement of both properties becomes possible examples in archaeological prospecting are presented and checked against independent d c resistivity measurements or excavation analyses

quantitative analysis of the extensional tectonics of tharsis bulge mars geodynamic implications about 10 of the tharsis bulge surface is intensely faulted with a fault density up to 1 fault km in these intensely faulted areas 54 impact craters which exhibit faulted walls and floor are now elliptical in shape these ellipticities indicate an average strain value of 10 inside these provinces this strain value is 4 times greater than the strain deduced from normal fault morphometric analysis this high value indicates that the strain is not only due to 60 dip normal faults and that some additional tectonic processes exist such as boudinage this important strain value corresponds to an elongation of about 50 km across thaumasia and tempe mareotis provinces and 20 km across alba patera regio the amount of elongation for the entire tharsis region is 2 orders of magnitude higher than the strains and motions related to standard models of bulge formation these intensely faulted areas are restricted areas where faults are both radial to the bulge and perpendicular to the topographic slope the stretching does not influence the regional topography and there are no topographic shoulders or important level differences between faulted and nonfaulted areas which would indicate that the crust is not thinned under the stretched provinces outside these intensely faulted areas the graben width is remarkably constant all over the tharsis bulge indicating the existence of a brittle ductile transition or an incompetent level at about 1 2 km below the surface a new origin for the tharsis tectonic features is proposed as a preliminary hypothesis the intensely faulted areas correspond to the uphill parts and to denudation zones of gravity slidings which move on a 2km deep incompetent level the gliding of the slab on the very low dipping flanks of tharsis needs three conditions 1 the viscosity of the incompetent layer must be equal to the viscosity of the ice 2 the brittle layer must have been previously faulted by the bulging itself 3 these preexisting radial fault directions must be perpendicular to topographic slope the ridged plain units in lunae palus and coprates provinces thus correspond to a zone of blocking inside the gliding slab due to an interruption of the decollement level

orientation relative age and extent of the tharsis plateau ridge system the tharsis ridge system is roughly circumferential to the regional topographic high of northern syria planum and the major tharsis volcanoes however many of the ridges have orientations that deviate from the regional trends normals to vector means of ridge orientations calculated in 10 boxes of latitude and longitude show that the tharsis ridges are not purely circumferential intersections of vector mean orientations plotted as great circles on a stereographic net show that the ridges are not concentric to a single point but to three broad zones these data indicate either that the tharsis ridge system did not form in response to a single regional compressional event with a single stress center or that the majority of the ridge system did form in a single event but with locally controlled deflections in the generally radially oriented stress field superposition relationships and relative ages suggest that the compressional stresses that produced the ridges occurred after the emplacement of the ridged plains volcanic units early in the hesperian period but did not extend beyond the time of emplacement of the syria planum formation units or the basal units of the tharsis montes formation during the latter half of the hesperian period comparison of topographic data with the locations of ridges demonstrates a good correlation between the topographic edge of the tharsis rise and outer extent of ridge occurrence compressional deformation related to tharsis is present out to about 5100 km from the regional topographic center located near northern syria planum the innermost extent cannot be determined because the ridged plains units have been buried by more recent volcanic units although ridge formation appears to have extended farther inward than is presently observed models involving a combination of isostatic stresses and stresses resulting from flexural loading appear to explain best the observed tensional features topography gravity and to a first approximation the locations and orientations of the compressional ridges

tectonic deformation by rotating parallel faults the bookshelf mechanism abstract in various tectonic environments extension of crustal parts and shear distortion has been accommodated by the rotation of an array of parallel faults because of its kinematic resemblance to the tilting of a row of books on a shelf the tectonic process may be referred to as a bookshelf mechanism its most important manifestions are cross faulting between normal faults or parallel wrench faults the extension of deltaic slope deposits and all forms of tilted block tectonics kinematically there are two basic modes of the mechanism a the dilational mode where rotating faults tend to open up and possibly become paths for fluid migration and b the domino style where reclining faults remain closed in both cases formation and rotation of the faults may take place in one tectonic event fault displacements may therefore often remain small and difficult to detect from the mechanical point of view bookshelf operations that accommodate shearing between parallel and predominantly parallel moving rock boundaries bookshelf mechanisms proper have to be differentiated from those operations responding to an imposed crustal extension or shortening after a review of geological evidence the process is addressed from a geomechanical point of view in order to determine the geological operating conditions and controlling parameters the crucial mechanical factor in the bookshelf mechanism is the component of normal stress that acts in the direction of the imposed displacement component parallel to the driving boundary plates in contrast to the usual assumption the driving shear stress on the boundary plates not only depends on the normal stress on the plates but it also varies with the value of the normal stress that acts inside the sheared material in the direction of the plate parallel displacement component it is the relationship between the two normal stresses that also determines the type of rotating parallel faults large scale rotation of parallel normal faults in domino style tilted block tectonics is primarily associated with the extension of ductile substrata from mechanical arguments and sand box experiments it has been inferred how the process and in particular the dip direction of the parallel faults is controlled by the way substratal extension progresses by means of the direction of a substratal squeeze flow the presence of a surface slope the strength anisotropy associated with fore set beds and by the configuration of competent boundaries of the extending overburden

age and origin of the lowlands of mars one of the many significant findings of the mars global surveyor mission is the presence of hundreds of quasi circular depressions qcds observed from high resolution mola topography data their presence has recently been interpreted to reflect a northern lowlands that archive some of the earliest recorded rocks on mars mostly below a veneer of hesperian and amazonian materials here we analyze these data coupled with a recent synthesis of geologic geophysical geomorphic topographic and magnetic information such analysis allows us to suggest a potential plate tectonic phase during the recorded early into middle noachian martian history that transitioned into a monoplate world with episodic magmatic driven activity persisting to present this working hypothesis is based on 1 the observation that the basement of the northern plains is younger than the basement of the southern highlands but older than the material exposures of the cratered highlands suggesting different formational ages for each one of the three geologic time units 2 the observation that parts of the very ancient highland s crust are highly magnetized thus suggesting that most if not all of the formation of the lowlands basement postdates the shut off of the martian dynamo some 4 gyr ago and so allowing hundreds of millions of years for the shaping of the buried lowlands consequently the role of endogenic processes in the earliest geological evolution of mars early perhaps into middle noachian requires reconsideration since mola topographic and mgs magnetic data afford a temporal window sufficient for very early non primordial shaping of the northern lowlands basement

global and regional ridge patterns on mars abstract over 16 000 wrinkle ridges on mars have been classified mapped and digitized to provide a large computer accessible data base for analyzing regions subjected to possible compressive stresses the survey has revealed major compressive structures that occur well beyond the tharsis dominated hemisphere the large variety of affected geologic terrains indicate stresses not simply localized in the intercrater plains one major area of inferred compression occurs in the southern cratered highlands near longitude 180 w where major ridges and scarps extend over 3000 km the occurrence and orientation of many ridges are locally controlled by ancient impact basins the chryse basin in particular has an important effect on ridges in northern lunae planum the removal of all basin concentric ridges reveals however a complex global pattern although such patterns may yet be controlled by heavily degraded impact basins major regional trends also emerge that appear to require broader scale global stresses most ridges in the western hemisphere are shown to be orthogonal to three centers corresponding to tharsis 1 n 122 w syria 12 s 104 w and chryse 19 n 47 w ridges not included in these three sets are generally more random and highly localized most but by no means all ridges in the eastern hemisphere are controlled by the hellas and isidis basins a simple global grid is not yet identifiable and may not be recognizable owing to the large number of regional patterns

the large thaumasia graben on mars is it a rift 1 we investigate the morphology and topography of one of the largest fault bounded tectonic structures on mars a complex approximately n s trending system of troughs and scarps at the western border of the thaumasia plateau in the claritas region hereinafter referred to as thaumasia graben or tg it is located between 15 s and 38 s latitude and at 255 e longitude no detailed investigation of its morphotectonic setting has been performed yet the region is a complexly fractured area with a number of different fault sets including simple and complex graben the tg extends over more than 1000 km along its trend averaging 100 km in width and 1 6 km in depth crustal extension is accommodated by the formation of a system of asymmetric graben or halfgraben on the basis of fault orientation and trough depth the tg can be subdivided in a north south direction into three segments except for the northernmost segment the predominant master fault system is located along the eastern flank of the tg highlighting the overall asymmetric architecture fault length segments vary from 50 to 90 km with observable displacements of 1 3 2 2 km crustal extension inferred from gridded mola topography across scarp offsets varies along trend between 0 5 km and 4 km assuming a fault dip of 60 this is relatively moderate extension if compared to terrestrial continental rifts but consistent with extension measured across the tempe rift on mars we find that the thaumasia graben displays some characteristics which are common to terrestrial continental rifts whereas other properties are distinctively not rift like

new evidence for a magmatic influence on the origin of valles marineris mars in this paper we show that the complex geological evolution of valles marineris mars has been highly influenced by the manifestation of magmatism e g possible plume activity this is based on a diversity of evidence reported here for the central part melas chasma and nearby regions including uplift loss of huge volumes of material flexure volcanism and possible hydrothermal and endogenic induced outflow channel activity observations include 1 the identification of a new 50 km diameter caldera vent like feature on the southwest flank of melas which is spatially associated with a previously identified center of tectonic activity using viking data 2 a prominent topographic rise at the central part of valles marineris which includes melas chasma interpreted to mark an uplift consistent with faults that are radial and concentric about it 3 hirise identified landforms along the floor of the southeast part of melas chasma that are interpreted to reveal a volcanic field 4 crism identification of sulfate rich outcrops which could be indicative of hydrothermal deposits 5 grs k th signature interpreted as water magma interactions and or variations in rock composition and 6 geophysical evidence that may indicate partial compensation of the canyon and or higher density intrusives beneath it long term magma tectonic and water interactions late noachian into the amazonian albeit intermittent point to an elevated life potential and thus valles marineris is considered a prime target for future life detection missions

tectonic history of the tharsis region mars the faults of the tharsis region of mars have been mapped and delineated on the basis of age the orientation of each group of faults was analyzed to determine if they were radial to a point the results indicate that there are at least four discrete centers of faulting within the tharsis area which are of significantly different age the four centers proposed are from oldest to youngest 1 in the thaumasia highlands 2 in northern syria planum and finally 3 and 4 near pavonis mons while episodes 3 and 4 occupy the same geographic position they are separated in time by the development of the tharsis lava plains and shields each episode of tectonism was separated from the next by a period of major basaltic volcanism the tectonic features of the tharsis area are thus viewed as being the cumulative result of the superposition of several discrete episodes of faulting rather than the result of one episode about a single point

crater fault interactions a metric for dating fault zones on planetary surfaces abstract constructing a tectonic history of a planetary surface requires determining precise fault ages a task not always possible with current analytical methods here we introduce a new method to constrain the ages of faults improving upon earlier methods that used cross cutting relationships with crater dated host surfaces and apply it to faulted terrains by counting all craters and categorizing them into faulted unfaulted and unclear types to date deformation directly additionally we construct a simple probabilistic model to account for regions of low fault density this new technique is applied to the tectonically complex thaumasia plateau mars to assess the timing of regional faulting and demonstrate its usefulness and ease of application

strike slip faulting of ridged plains near valles marineris mars the surface of mars shows abundant evidence of extensional and contractional deformation in the form of normal faults grabens and wrinkle ridges 1 3 in contrast strike slip faults have been considered to be extremely rare or absent on mars4 5 this view is based on the lack of significant lateral offset of pre existing markers such as craters across suspected faults thus mars is believed to have evolved without plate tectonics or other large scale lateral motions of the lithosphere6 however careful study of viking orbiter images is revealing that strike slip faults may be present on mars7 here i identify and document several well preserved examples of martian strike slip faults and examine their relationships to wrinkle ridges the strike slip faulting predates or overlaps periods of wrinkle ridge growth south east of valles marineris and some wrinkle ridges may have nucleated and grown as a result of strike slip displacements along the echelon fault arrays lateral displacements of several kilometres inferred along these arrays may be related to tectonism in tharsis

the shallow structure of the martian lithosphere in the vicinity of the ridged plains wrinkle ridges in the smooth plains of the coprates and lunae planum regions of mars form linear or concentric patterns with a regular spacing of 25 50 km the authors test the hypothesis that the periodic development of deformation was a consequence of unstable horizontal compression that occurred prior to probable ridge related faulting of a strength stratified lithosphere which consists of a mechanically strong surface plains unit that successively overlies a weak megaregolith and a strong lithospheric basement results show that a range of models with both rigid and deformable megaregolith basement interface conditions yield solutions which can explain the ridge spacing within the constraint provided by the estimated thickness of the smooth plains materials in models that incorporate viscous and plastic rheologies uniform and exponentially varying vertical strength distributions and the presence or absence of interfacial slip at the base of the surface plains unit the ridge spacing is primarily controlled by the power law exponent of the lithosphere the megaregolith plains unit thickness ratio and the plains unit megaregolith strength contrast deformable basement models with a viscous rheology 1 le n approx le 3 can explain the ridge spacing if the megaregolith was thicker than and approximately 1 3 orders of magnitude weaker than themore plains unit similar models with a perfectly plastic n yields infinity rheology require plains unit thicknesses greater than 5 km which exceeds most observational estimates ridge spacing in the combined viscous and plastic models can be consistent with either a dry water rich or ice rich megaregolith at the time of ridge formation less

ground penetrating radar surveys used in archaeological investigations during 1982 and 1983 two ground penetrating radar surveys were carried out in conjunction with archaeological investigations in canada the first survey was a detailed high resolution radar survey at the site of a sixteenth century basque whaling station on the labrador coast designed to locate the graves of the basques the second was a rapid low resolution reconnaissance survey as part of a prehistory impact assessment program at the site of the new national museum of man in hull quebec both surveys were experimental and were designed to see whether ground penetrating radar would be useful for identifying and locating anomalies of archeological significance radar was successful in detecting archeological anomalies several meters in size at both locations and the high resolution survey was moderately successful in identifying basque graves ongoing work involves comparing radar results with the archaeological investigations to increase the understanding of how radar can be applied to archaeology a

plains tectonism on venus the deformation belts of lavinia planitia high resolution radar images from the magellan spacecraft have revealed the first details of the morphology of the lavinia planitia region of venus a number of geologic units can be distinguished including volcanic plains units with a range of ages transecting these plains over much of the lavinia region are two types of generally orthogonal features that we interpret to be compressional wrinkle ridges and extensional grooves the dominant tectonic features of lavinia are broad elevated belts of intense deformation that transect the plains with complex geometry they are many tens to a few hundred kilometers wide as much as 1000 km long and elevated hundreds of meters above the surrounding plains two classes of deformation belts are seen in the lavinia region ridge belts are composed of parallel ridges each a few hundred meters in elevation that we interpret to be folds typical fold spacings are 5 10 km fracture belts are dominated instead by intense faulting with faults in some instances paired to form narrow grabens there is also some evidence for modest amounts of horizontal shear distributed across both ridge and fracture belts crosscutting relationships among the belts show there to be a range in belt ages in western lavinia in particular many ridge and fracture belts appear to bear a relationship to the much smaller wrinkle ridges and grooves on the surrounding plains ridge morphology tends to dominate belts that lie more nearly parallel to local plains wrinkle ridges and fracture morphology tends to dominate belts that lie more nearly parallel to local plains grooves we use simple models to explore the formation of ridge and fracture belts we show that convective motions in the mantle can couple to the crust to cause horizontal stresses of a magnitude sufficient to induce the formation of deformation belts like those observed in lavinia we also use the small scale wavelengths of deformation observed within individual ridge belts to place an approximate lower limit on the venusian thermal gradient in the lavinia region at the time of deformation

topography of valles marineris implications for erosional and structural history compilation of a simplified geologic geomorphic map onto digital terrain models of the valles marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus thickness of deposits inside the troughs volumes of void spaces above geologic geomorphic units and volumes of deposits the central troughs north ophir north and central candor and north melas chasmata lie as much as 11 km below the adjacent plateaus in ophir and candor chasmata interior layered deposits reach 8 km in elevation if the deposits are lacustrine and if all troughs were interconnected lake waters standing 8 km high would have spilled out of coprates chasma onto the surrounding plateaus having surface elevations of only 4 5 km in this case interior deposits above about 4 km in the central troughs would not be lacustrine they could be volcanic on the other hand the troughs may not have been interconnected at the time of interior deposit emplacement they may have formed isolated ancestral basins the existence of such basins is supported by independent structural and stratigraphic evidence the ancestral basins may have eventually merged perhaps through renewed faulting to form northern subsidiary troughs in ophir and candor chasmata and the coprates north melas ius graben system the peripheral troughs are only 2 5 km deep shallower than the central troughs they may have formed from a combination of erosional collapse and structural activity chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus which supports the idea of release of water under artesian pressure from confined aquifers the layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels if these layered deposits are of volcanic origin they may have been emplaced beneath ice in the manner of table mountains areal and volumetric computations show that erosion widened the troughs by about one third and that deposits occupy one sixth of the interior space even though the volume eroded is larger than the volume deposited topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source additional material may have come from subterranean piping from reworking of local disintegration products on the floors such as chaotic materials or from eolian influx but overall it is likely that the additional material is volcanic and that it forms mostly the upper more diversely bedded layers of the interior deposits

3 d ground penetrating radar applied to fracture imaging in gneiss three dimensional ground penetrating radar georadar techniques suitable for geological engineering applications have been developed and tested initial experiments were conducted on the floor of a quarry in southern switzerland from which ornamental gneissic rock is extracted during a brief two day period constant offset georadar data were recorded over a 650m2 area with a grid cell size of 0 1 m 0 2 m georadar velocities were estimated from the results of expanding spread surveys all georadar data and associated geometry files were recorded automatically in seismic industry formats the experimental georadar data set was processed image enhanced and interpreted using 3 d seismic reflection software operating on a workstation arbitrary vertical sections time slices 3 d images and animated movies in which the observer travels through the entire data volume were constructed from the resultant migrated georadar data semi automatic tracking routines allowed continuous subhorizontal reflectio

planetary science a mega landslide on mars the vast thaumasia plateau on mars is fringed by extensive zones of deformation topographic and structural analysis suggests that the plateau may have slipped in a massive landslide deforming its margins in the process

structural development of coprates chasma and western ophir planum valles marineris rift mars a portion of valles marineris was mapped in detail in order to clarify the dominant processes responsible for the formation of coprates chasma new crater counts indicate that the caprock on western ophir planum plateau has a late hesperian crater age whereas trough floor preserved in western coprates chasma has an early to late hesperian crater age caprock on western ophir planum correlates in relative age with the syria planum formation and the caprock may overlie lower hesperian ridged plains material the conspicuous absence of wrinkle ridges on ophir planum may reflect burial by this later material trough floor material in coprates chasma correlates in relative age with ridged plains material on the adjacent lunae planum and coprates plateaus and represents a structurally coherent block displaced downward by normal faulting the crater counts and detailed structural relationships demonstrate the commonly accepted view that coprates chasma occupies a graben the floor of this graben is only thinly mantled by intratrough deposits and is relatively intact the trough shows no evidence for a chaotically broken and jumbled floor as required by genesis models of collapse and subsurface drainage formation of coprates chasma by keystone collapse of locally elevated topography is not supported by available topographic data but a general association between the trough and volcanotectonic activity in the tharsis region is considered to be a likely explanation for the trough forming stresses subtle asymmetries in topography and boundary fault development across coprates chasma may imply a gentle down to the north half graben geometry for the trough normal faults that define the northern margin of western coprates chasma and those that deform the adjacent ophir planum plateau change trend systematically with position implying a 30 rotation of the local horizontal principal stresses in this region during trough growth faulting on ophir planum appears related to the faulting that created the coprates chasma trough the geology and structure of coprates chasma are comparable to those of other troughs such as melas ius and perhaps candor chasmata suggesting that these troughs may also have formed as grabens the revised crater age for western ophir planum indicates that the initiation of trough faulting and subsidence in the valles marineris system is early late hesperian and may have been synchronous across the system relative to the prevailing cratering rate

origin of periodically spaced wrinkle ridges on the tharsis plateau of mars ridged plains are a major geologic unit on mars and are a predominant unit on the tharsis plateau a region that has undergone uplift extension and extensive shield and flood volcanism these units probably flood volcanic in origin are characterized by landforms classed as wrinkle ridges wrinkle ridges are interpreted to be folds resulting from buckling followed by reverse to thrust faulting flexure fracture a prominent characteristic of many of the wrinkle ridges on mars particularly those in the tharsis ridge system is the periodic nature of their spacing the periodic spacing has been evaluated in six major provinces on the tharsis plateau with regions further divided into domains based largely on variation in ridge orientation the average spacing of the tharsis ridges based on 2934 measurements is 30 km in an effort to account for the periodic nature of the wrinkle ridges the ridged plains material is modeled as both a single member and a multilayer with frictionless contacts that has buckled at a critical wavelength of folding free slip between layers is assumed based on the possible existence of mechanically weak interbeds in the ridged plains sequence separating groups of flows the near surface mechanical structure in the area of ridged plains is approximated by a strong layer or layers overlying a weak megaregolith of finite thickness overlying a strong basement buckling of the ridged plains is assumed to be decoupled from the basement by the weak megaregolith decoupling is enhanced if the megaregolith were water or ice rich at the time of deformation the rheologic behavior of the ridged plains and megaregolith is approximated by a linear elastic and linear viscous material the models are examined for a range in 1 the strength contrast between the ridged plains material and the underlying megaregolith 2 thickness of the ridged plains material 3 thickness of the megaregolith and 4 number of layers the elastic model can explain the observed ridge spacing only if the ridged plains are relatively thick 2400 m with multiple layers n 1 and relatively high contrasts in young s modulus e e0 100 the high e e0 required is possible only if the megaregolith was water rich at the time of deformation over the same range in values of the parameters viscous buckling is much less restricted the viscous model can explain the observed ridge spacing over a wide range in ridged plains thickness 250 m to several kilometers megaregolith thickness number of layers n 1 to 8 and contrasts in viscosity 0 10 in addition viscous buckling is viable if the megaregolith were dry water rich or ice rich at the time of deformation the absence of folds with a cross sectional geometry in the shape of a sinusoid anticline syncline pairs may be the result of initial deformation of the ridged plains material into low amplitude folds in infinitesimal strain followed by plastic yielding in the cores of the anticlines in finite strain initial elastic or viscous buckling coupled with plastic yielding confined to the hinge area followed by the development of reverse to thrust faulting could account for the asymmetric fold geometry of many of the wrinkle ridges

drape folding of compressible elastic layers i analytical solutions for vertical uplift abstract two new analytical solutions allow the effects of layer thickness vertical fault zone width and throw layer compressibility and basal slip on drape fold geometry to be investigated welded case i and non welded case ii lower contacts with step vertical displacement functions and an upper free surface are used as boundary conditions comparison of fold profiles displacement fields and principal stress trajectory fields suggests that fold form yields relatively little information about lower boundary geometry or stress conditions drape folds with non welded contacts however are distinctly asymmetric along their lower boundaries displacement and principal stress trajectory fields on the other hand can be used to distinguish which of the two boundary conditions was used to produce a given theoretical fold values of maximum shear stress are much higher along welded contacts than along non welded contacts suggesting that faulting and brecciation should be more prevalent along welded contacts these findings are consistent with published field observations and suggest that some attributes of theoretical folds for example lower boundary geometry and minor fracture orientation may be used to infer the conditions under which real drape folds were formed

the growth of geological structures by repeated earthquakes 2 field examples of continental dip slip faults a strong test of our understanding of the earthquake cycle is the ability to reproduce extant fault bounded geological structures such as basins and ranges which are built by repeated cycles of deformation along strike slip faults the coseismic and interseismic deformation can be nearly equal in magnitude and opposite in sign resulting in little permanent deformation except for the fault offset for dip slip faults portions of the crust are lifted and dropped and so buoyancy forces are exerted the seismic and interseismic deformations do not balance and structures grow and become subject to erosion and deposition we consider three examples for which the structure and fault geometry are well known the white wolf reverse fault in california site of the 1952 kern county m 7 3 earthquake the lost river normal fault in idaho site of the 1983 borah peak m 7 0 earthquake and the cricket mountain normal fault in utah site of quaternary slip events basin stratigraphy and seismic reflection records are used to profile the structure and coseismic deformation measured by leveling surveys is used to estimate the fault geometry to reproduce these structures we add the deformation associated with the earthquake cycle the coseismic slip and postseismic relaxation to the flexure caused by the observed sediment load treating the crust as a thin elastic plate overlying a fluid substrate the cumulative deformation is principally dependent on the elastic plate thickness modestly sensitive to the sediment substrate density difference and insensitive to the fluid viscosity for the 4 to 8 ma structures we deduce a longterm flexural rigidity of 2 15 1019 nm this is equivalent to an elastic plate thickness of 2 4 km for a young s modulus of 2 5 1010 nm 2 this value is found where independent estimates of the elastic thickness from the coherence between surface topography and gravity yield values of about 4 km but where coseismic fault slip extends to a depth of 10 15 km thus much of the seismogenic crust must weaken substantially during the life of active faults causing the fault bounded basins to narrow over time

geomorphology of ma adim vallis mars and associated paleolake basins 1 ma adim vallis one of the largest valleys in the martian highlands appears to have originated by catastrophic overflow of a large paleolake located south of the valley heads ma adim vallis debouched to gusev crater 900 km to the north the landing site for the spirit mars exploration rover support for the paleolake overflow hypothesis comes from the following characteristics 1 with a channel width of 3 km at its head ma adim vallis originates at two eastern and western gaps incised into the divide of the 1 1 m km2 enclosed eridania head basin which suggests a lake as the water source 2 the sinuous course of ma adim vallis is consistent with overland flow controlled by preexisting surface topography and structural control is not evident or required to explain the valley course 3 the nearly constant 5 km width of the inner channel through crater rim breaches the anastomosing course of the wide western tributary the migration of the inner channel to the outer margins of bends in the valley s lower reach a medial sedimentary bar 200 m in height and a step pool sequence are consistent with modeled flows of 1 5 106 m3 s peak discharges were likely higher but are poorly constrained by the relict channel geometry 4 small direct tributary valleys to ma adim vallis have convex up longitudinal profiles suggesting a hanging relationship to a valley that was incised quickly relative to the timescales of tributary development 5 the eridania basin had adequate volume between the initial divide and the incised gap elevations to carve ma adim vallis during a single flood 6 the eridania basin is composed of many overlapping highly degraded and deeply buried impact craters the floor materials of the six largest craters have an unusually high internal relief 1 km and slope 0 5 1 5 among degraded martian craters which are usually flat floored long term fluvial sediment transport appears to have been inhibited within these craters and the topography is inconsistent with basaltic infilling 7 fluvial valleys do not dissect the slopes of these deeper crater floor depressions unlike similar slopes that are dissected at higher levels in the watershed these characteristics 6 7 suggest that water mantled at least the lower parts of the eridania basin floor throughout the period of relatively intense erosion early in martian history the lake level increased and an overflow occurred near the close of the noachian age determined using 5 km crater counts initially the eridania basin debouched northward at two locations into the intermediate basin a highly degraded impact crater 500 km in diameter as this intermediate basin was temporarily filled with water erosion took place first along the lower northern reach of ma adim vallis debouching to gusev crater the western overflow point was later abandoned and erosion of the intermediate basin interior was concentrated along the eastern pathway subsequent air fall deposition impact gardening tectonism and limited fluvial erosion modified the eridania basin region so evidence for a paleolake is restricted to larger landforms that could survive post noachian degradation processes

integrated geophysical surveys for the subsurface mapping of buried structures under and surrounding of the agios voukolos church in izmir turkey abstract this work presents the results of the integrated usage of geophysics in the agios voukolos church one of the unique orthodox constructions in izmir the surveys had two main objectives to define subsurface characteristics inside and around the church and search for possible structural damage such as cracks and fissures that may exist in the subfloor of the church magnetic gradiometry ground penetrating radar and electrical resistivity tomography were used in the investigations this study is the first indoor application of magnetic gradiometry the studies revealed that several suspicious relics and crypts might have existed under the floor of the church in addition investigations of the courtyard area indicated potential buried structures under the settling area of the church this study demonstrates the importance of the integrated usage of non destructive geophysical techniques in searching for possible hidden subsurface structures in standing historical buildings in addition magnetic gradiometry might be useful in indoor studies assuming that there are no important magnetic sources near the site

a new survey of multiring impact basins on mars multiring impact basins have profoundly influenced the geologic evolution of mars we compile and summarize the evidence for martian impact basins and suggest eight new examples multiring basins on mars define three morphologic subclasses with increasing basin size basins having diameters 300 3600 km have extremely shallow topographic profiles and numerous concentric structures expressed as scarps massifs and channels radial and concentric structures analogous to those associated with orientale are not apparent for basins of argyre size or larger these variations in basin morphology and structure may be associated with mechanical interactions between basin forming impacts relatively thin weak lithosphere and for the largest impacts spherical target geometry multiring basins are recognized on all parts of mars including tharsis elysium and the northern lowlands much of the subsequent resurfacing of cratered terrain such as lunae planum ridged plains is associated spatially with multiring basins nucleation of long lived volcanic complexes in tharsis and elysium was probably aided by early impact basins the planetary terrain dichotomy was probably established during the period of heavy meteoritic bombardment and subsequent processes in the northern plains region were not sufficiently vigorous to destroy or completely obscure the underlying multiring basin fabric the revised population of multiring basins is consistent with the size frequency distribution of craters 500 km in diameter on mars basins having diameters 500 d 1850 km are characterized by a cumulative frequency slope of 0 75 0 16 whereas the larger basins define a slope of 1 7 0 45 this change in slope occurs over the same diameter range as the significant change from orientale type basin morphology at smaller diameters to argyre and chryse type basin morphology the population of craters and basins on mars confirms that the relative crater densities on the terrestrial planets due to heavy bombardment are comparable perhaps suggesting a common source for the impacting objects

tectonic evolution of the eastern margin of the thaumasia plateau mars as inferred from detailed structural mapping and analysis 1 the eastern margin of the thaumasia plateau emtp is characterized by a diversity of tectonic features which recorded its complex and still controversial tectonic history a detailed structural survey and analyses have been carried out in order to assess the kinematics and relative age of the main deformational events combining results from statistics of lineament orientations and density of fault length for each geologic unit and taking into account crosscutting relationships among tectonic structures three main deformational events have been recognized the early stage of the tectonic evolution of emtp is recorded by noachian units at the southern edge of melas dorsa and is represented by n s oriented grabens sutured by early hesperian formations starting from late noachian the extensional stress field became ne sw oriented and resulted in the formation of nw se striking sets of grabens at the boundary between noachian and hesperian the most important change in tectonic regime occurred the hesperian tectonics are characterized by an e w shortening possibly related to an eastward motion of the thaumasia plateau this tectonic phase likely produced a n s oriented wrinkle ridges as well as regional folds and thrust faults e w oriented preexisting tectonic lineaments could have been reactivated forming regional transfer zones in this scenario coprates rise melas dorsa and thaumasia ridge could be interpreted as mountain belts resulting from buckling and thrust faulting of the eastern and southern margins of the thaumasia plateau the proto valles marineris could have experienced a left lateral component of displacement and played a role of a transfer shear zone

unraveling the geologic and tectonic history of the memnonia sirenum region of mars implications on the early formation of the tharsis rise abstract the geologic and tectonic history of the memnonia sirenum region of mars has been reconstructed on the basis of geologic mapping and relative age dating of rock units and structures using crater counts and superposition relations comparisons between the ages of rock unit formation and the orientations of the earliest structures associated with tharsis demonstrate a strong interplay among tectonic magmatic and aqueous activity in the memnonia sirenum region early noachian geologic activity identified within this region includes the formation of large northeast trending extensional basins stratigraphic and tectonic evidence suggests that these basins formed concurrently with the early formation of tharsis when the dynamo and associated magnetosphere were still in operation in addition to the ancient basins later tharsis influenced activity includes prominent tectonic fault systems associated with the formation of tharsis and arsia mons detailed mapping of the faults indicates that structures associated with memnonia and sirenum fossae resulted from the formation of tharsis during the middle to late noachian late stage amazonian activity also identified within this region includes valley networks and collapse depressions that are linked and or occur among tharsis centered faults that cut features throughout this region including mangala valles

determining magnetic susceptibility of ancient and modern potsherds using a fast cheap and portable probe archaeometry is the application of scientific techniques to archaeology the general perception is that it consists of the use of a number of geophysical techniques that were originally developed to explore for mineral deposits in order to delineate anthropological remains in the subsurface without disturbing them such techniques include resistivity tomography e g saey et al 2012 glover 2010 papadopoulos et al 2006 proton spin magnetometry e g buyuksaraca et al 2006 ground penetrating radar e g dabas et al 2000 neubauer et al 2002 and electromagnetic measurements e g bigman 2012 the perception has been fed by television series such as the time team and now many university based geophysicists spend at least some of their time applying their techniques to archaeological remains however these techniques are only one part of archaeometry which also covers the use of physical and chemical methods to understand how archaeological remains were made and used e g lima et

the formation of the south tharsis ridge belt basin and range style extension on early mars the south tharsis ridge belt strb is located along the northeastern edge of terra sirenum and partially surrounds the southwestern part of tharsis in an arc it consists of 29 large ridges separated by distances 130 to 260 km with average relief of 1 5 km above the surrounding plains because the strb is among the oldest tectonic features associated both spatially and developmentally with tharsis it may provide key information on the early evolution of tharsis and possibly pre tharsis processes earlier studies concluded that the ridges formed through compressional tectonism however the shape size and separation of the ridges support the interpretation that the strb resembles the extensional basin and range province on earth both regions are characterized by series of parallel mountain ranges separated by broad valleys in this study we evaluate both extensional and compressional hypotheses for the origin of the ridges using evidence from topography deformed craters crustal thickness models and strain modeling though neither interpretation explains all aspects of the ridges the topography of the ridges and crustal thinning associated with the western part of the ridge belt support an extensional origin strain models predict that basin and range style wide rifting would be expected for early martian conditions this extension may have been initiated by plume induced uplift in the early stages of tharsis formation but the large amount of extensional strain inferred in the western strb must have been accommodated by compression elsewhere possibly in the heavily deformed craters of western terra sirenum

stress in the indo australian plate cloetingh s and wortel r 1986 stress in the ind austr ian plate in b johnson and a w bally editors intraplate deformation characteristics processes and causes tectonophysics 132 49 67 we modelled the state of stress in the indo australian plate in order to investigate quantitatively variations observed in tectonic style the numerical procedure incorporates the dependence of slab pull and ridge push on the age of the oceanic lithosphere estimates are presented for the average net resistive forces at the himalayan collision zone the suction force acting on the overriding indo australian plate segment at the tonga kermadec trench and the drag at the base of the lithosphere our modelhng shows a concen ation of compressive stresses of the order of 3 5 lcbar in the ninetyeast ridge area the effects of the compressive resistance associated with himalayan collision and subduction of young lithosphere off the northern part of the sunda arc are focused in this region the stress field as calculated gives a consistent explanation for the observed concentration of seismic activity stein and okal 1978 and significant deformation in the oceanic crust weissel et al 1980 mcadoo and sandwell 1985 in the area the calculated stress field in the area adjacent to the southeast and central india ridges is characterized by tension parallel to the spreading axis this explains the concentration of near ridge normal faulting seismicity with t axes subparaile1 to the spreading ridge in the indian ocean as recently observed by bergman et al 1984 and wiens and stein 1984 the regional stress field along the strike of the sunda arc varies from compression seaward of and parallel to the sumatra trench segment to tension perpendicular to the java flores segment this explains the selective occurrence of well developed grabens seaward off the java flores segment of the trench observed by hilde 1983 our modelling shows that the observed rotation of the stress field denham et al 1979 in the australian continent is mainly the consequence of its geographic position relative to the surrounding trench segments and the variations of the forces acting on the down going slab in each of these the state of compression in west and central australia is induced by the action of resistive forces at the himalayan and banda arc collision zones the joint occurrence of high levels of compression in the plate s interior and normal faulting seismicity in the near ridge areas is a transient feature unique to the present dynamic situation of the indo australian plate

thick shell tectonics on one plate planets applications to mars a theory for stress distributions in thick lithospheric shells on one plate planets is developed based on the zero frequency equations of a self gravitating elastic spherical shell overlying a strengthless fluid stress distributions in lithospheres are reviewed for both the compensated and flexural modes in the former case surface stresses only depend on surface topography while for the latter case it is shown for long wavelengths that stress trajectories are mainly dependent on the lithospheric lateral density distribution and not on elastic properties computational analyses are carried out for mars and it is found that isostatically compensated models correctly predict the graben structure in the immediate tharsis region and a flexural loading model is satisfactory in explaining the graben in the regions surrounding tharsis a three stage model is hypothesized for the evolution of tharsis isostasy with north south graben formation on tharsis followed by flexural loading and radial graben formation on the perimeter of tharsis followed by a last stage of loading with little or no regional deformation this model is consistent with the martian lithosphere monotonically thickening over geologic time

system of tectonic features common to earth mars and venus investigations of landforms on the terrestrial planets have revealed a system of tectonic features consisting of long narrow regularly spaced folds and or thrust faults referred to as wrinkle ridges and conjugate sets of cross trending strike slip faults these are observed in the yakima fold belt of the columbia plateau earth the ridged plains of the tharsis province mars and the lowland plains of lavinia planitia venus the wrinkle ridges and strike slip faults reflect a relatively small amount of crustal shortening in these regions of distributed deformation the observed geometric relations between the structures are consistent with those predicted by the coulomb anderson model although the tectonic settings of the provinces studied on the three planets are very different the crustal materials appear to have deformed in a similar manner

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

lithospheric scale buckling and thrust structures on mars the coprates rise and south tharsis ridge belt detailed photogeologic mapping documents for the first time the deformation sequence of the coprates rise materials of middle noachian through perhaps early hesperian age were involved in the horizontal shortening of crustal and lithospheric rocks that produced uplift and asymmetric east vergent folding of these layers during the late noachian and perhaps early hesperian previous suggestions of normal faulting as the deforming mechanism are not supported by the new mapping or by dislocation models of rise topography the most likely mechanism for producing the coprates rise is folding due to buckling instability and perhaps thrust faulting an extensive ridge belt concentric to south tharsis is defined by a newly recognized system of approximately coeval long wavelength topographic ridges and swales that include the coprates rise horizontal shortening of crust and lithosphere is manifested by periodically spaced structures at two different scales wrinkle ridges spaced tens of kilometers apart and the south tharsis system of ridges spaced hundreds of kilometers apart both types of structures may be associated with early volcanotectonic activity and crustal thickening in south tharsis these and other large ridges indicate that lithospheric buckling and thrust faulting may have been common on early mars

how preexisting weaknesses control the style of continental breakup continental breakup is a highly variable process differences occur in the relative timing and extent of volcanism uplift and graben formation as well as in the mode and amount of continental extension before breakup we propose a model which reconciles this variability with the previously recognized tendency for breakup to occur along preexisting weak trends continental lithosphere is viewed as a composite material composed of two strong layers one in the upper mantle and one in the middle crust finite element simulation indicates that extensional failure at weaknesses in the mantle causes concentrated extension in the mantle and diffuse extension in the crust this leads to early melt segregation and volcanism margin uplift during the late stages of the extension process and relatively narrow symmetrical extended margins in contrast failure at weaknesses in the crustal strong zone causes focused extension in the crust and diffuse extension in the mantle this produces initial graben formation cooling in the lower crust and upper mantle and broad asymmetrical extended margins volcanism only occurs late in the process failure at laterally offset weaknesses within both strong layers leads to a deformation pattern dominated simple shear thus differences in the prerift configuration of the continental lithosphere can control the overall style of continental breakup

new temple discovery at the archaeological site of nysa western turkey using gpr method abstract we carried out a ground penetrating radar gpr study at specific sites around the nysa city western turkey to assess the potential of detection method and imaging of buried archaeological features as a major educational and cultural aegean city during the hellenistic and roman times nysa has been the focus of archaeological investigations for the last 100 yrs past and ongoing excavations have revealed major ancient buildings such as theatres amphitheatres a library and shops however it is suspected that the original city may have extended further and reached a larger size we collected 22 profiles using a gpr system equipped with two shielded antennas of 250 and 500 mhz central frequencies after processing steps gpr results revealed the existence of buried walls located at 50 m west of the library they systematically display a characteristic signature hyperbolic shaped point source reflections in gpr profiles and may be described in terms of location geometry and dimension to a certain extent of construction style excavations made after our study confirmed our results and unearthed a previously unknown temple hence shallow geophysical investigations helped in gathering crucial archaeological information to better characterize the extent and richness of the city of nysa

historical seismicity and implications for diffuse plate convergence in the northeast indian ocean large historical earthquakes provide constraints on the geographical extent and kinematics of the slow diffuse plate boundary extending from the central indian ridge to the sumatra trench the fault parameters of pre 1963 earthquakes are derived using a grid search for the best fit between observed and synthetic body waveforms surface wave spectral amplitudes and polarity and polarization constraints and location uncertainties are determined using a bootstrap resampling method the march 9 1928 ninetyeast ridge m 7 7 event shows left lateral strike slip faulting along a plane approximately coincident with the orientation of the ninetyeast ridge two small events which occurred at the location of the 1928 event in 1980 show focal mechanisms nearly identical to that determined for the 1928 earthquake and apparently reactivated the same fault the 1928 waveforms can also be fit by a thrust faulting solution with ene striking fault planes but a variety of evidence including the recent strike slip earthquakes at the same location suggest the strike slip solution these earthquakes are located along the western scarp of the ridge and do not represent reactivation of the ninetyeast fracture zone to the east of the edifice which was a major plate boundary in the early cenozoic the january 23 1949 m 6 75 and march 22 1955 m 7 0 wharton basin earthquakes although only 350 km apart show different strike slip and thrust faulting mechanisms all earthquakes show a regionally consistent pattern of horizontal compressional stress which changes from nw se in the wharton basin to n s in the central indian basin the compressional axes are oriented perpendicular to linear gravity anomalies associated with lithospheric flexure indicating little change in stress orientation since the onset of folding seismic deformation along the diffuse boundary consists of sinistral strike slip faulting associated with n s features such as the ninetyeast ridge and the 86 e fracture zone and thrust or reverse faulting in regions between fracture zones assuming transform motion the approximate slip rate along the northern ninetyeast ridge calculated from the summed moments of earthquakes is 2 8 mm yr this value is an order of magnitude less than previous estimates and suggests that at most only a small fraction of the current relative plate motion 7 mm yr occurs along the ridge the geographic distribution of seismicity suggests that the wharton basin east of the ninetyeast ridge is nearly as seismically active as the central indian basin to the west this result along with observed long wavelength gravity anomalies in the wharton basin indicates that the india australia plate boundary intersects the sumatra trench along a diffusely deforming region several thousand kilometers long rather than along a discrete transform zone

evidences for a noachian hesperian orogeny in mars a number of tectonic structures have been located at the thaumasia plateau daedalia planum and aonia terra mars they include isolated folds with axial traces up to 200 km long trains of tightly folded structures tens of km long and thrusts their size and geometry are similar to those on earth and the direction of compression seems to have varied amply with time suggesting a complex tectonic evolution crater counts on the deformed terrain point to noachian to early hesperian ages on the basis of the geometry and geological relations of these structures we propose that they form part of an old martian orogen the thaumasia aonia orogen which embraced not only the thaumasia plateau but areas of daedalia planum aonia terra and nereidum montes as well a regional coherent layering is previous to the deformation and could represent the trace of even older stresses on the martian lithosphere

a mobile four electrode array and its application to the electrical survey of planetary grounds at shallow depths this paper deals with a mobile array for mapping the electric properties of planetary surfaces with a resolution of the order of a few meters in all dimensions the principle of the measuring technique is first recapitulated the prototype model of this novel instrument is then described the array was operated at a frequency of 128 khz over a site with apparent resistivities in the range 20 100 m and the experimental results are found to be in excellent agreement with those derived from another independent technique it is demonstrated from measurements collected on a second site with resistivities of the order of several kilo ohm meters that this new technique also yields information about the dielectric constant of the ground this method is not only applicable to geological surveys on earth but also appears particularly attractive for the exploration of the surface of other planets by means of landers penetrators or unmanned rovers

simultaneous use of electrostatic quadrupole and gpr in urban context investigation of the basement of the cathedral of girona catalunya spain there is a growing demand for nondestructive geophysical investigation in archaeology especially in an urban context this is a result of taking our heritage more seriously than in the past since excavations are possible only over a very limited area any a priori information brought by geophysical methods can help to focus these excavations the classical geophysical methods used in archaeology resistivity magnetism are not applicable in an urban context with problems of accessibility and inherent electromagnetic noise the potential of the combined use of ground penetrating radar gpr and electrostatic es quadrupole data is demonstrated in the investigation of the floor of the cathedral of girona in northern spain a 1 3 1 3 m electrostatic quadrupole was towed continuously over a set of parallel profiles to produce a resistivity map for a 20 60 m area a set of resistive anomalies corresponds with known structures probably graves the largest observed anomalies appear to be related to fou

the search for graves over the decades grave markers in old cemeteries have been lost geophysical exploration can sometimes locate the unmarked burials the two techniques which may be best for this search are a ground penetrating radar survey and a soil conductivity survey a ground penetrating radar survey with its capability for estimating the depth and shape of buried objects is particularly suitable with an electromagnetic induction survey the disturbed soil in the grave shaft can sometimes be detected as a change in electrical conductivity both of these surveys also can locate large metal objects these surveys have limitations at some sites the radar cannot profile deeply enough at others the soil strata are so complex that graves cannot be distinguished a conductivity survey can be degraded by metallic trash and other small objects in the topsoil it can give the best results where the earth is distinctly stratified results from nine surveys are illustrated here the sites are all in the u s a and the gra

tectonic history of the syria planum province of mars we attribute most of the development of extensive fractures in the tharsis region to discrete tectonic provinces within the region rather than to tharsis as a single entity one of these provinces is in syria planum faults and collapse structures in the syria planum tectonic province on mars are grouped into 13 sets based on relative age areal distribution and morphology according to superposition and fault crosscutting relations and crater counts we designate six distinct episodes of tectonic activity in the following chronologic order stage i is an early to late noachian deformation forming mostly east west structures fault set ia some large volcanoes also formed faults were produced possibly by flexural uplift also arcuate north trending grabens set ib indicate that faulting is transitional to the next stage stage ii is late noachian to early hesperian radial faulting centered in syria planum possibly due to isostatic uplift in late noachian set iia to early hesperian set iib time stage iii is early to late hesperian faulting tangential to syria planum that was related to local centers of uplift sets iii1 iii3 on the periphery of syria planum stage iv is a late hesperian graben formation that was circumferential to syria planum set iva caused either by collapse associated with eruption of magma or by flexure of the lithosphere due to volcanic loading in association with volcanism minor faulting occurred producing an oval pattern of faults in southwest syria planum set ivbl and a radial pattern south of the planum set ivb2 that apparently rejuvenated buried stage ii faults stage v is a late hesperian to early amazonian development of grabens and troughs of noctis labyrinthus and western valles marineris set v that was probably instigated by local uplift exposure of groundwater or ground ice zones may have produced further collapse and trough enlargement stage vi is early amazonian northwest trending faulting in noctis fossae set vil perhaps due to tharsis monies centered tectonism and north northwest normal faulting along the eastern side of the claritas rise set vi2 that was due to tectonic subsidence the duration of tectonic activity in the syria planum province was perhaps 2 3 b y photoclinometric topographic profiles across 132 grabens and fault scarps show that syria planum grabens have widths average of 2 5 km and most range from 1 to 6 km similar to lunar grabens but the martian grabens have slightly higher side walls average about 132 m and gentler wall slopes average of 9 and range of 2 25 than lunar grabens 93 m high and 18 slopes scarp degradation on mars has progressed through quakes impact shaking and dry slope processes the lower slopes may be due to mars higher gravity estimates of the amount of extension for individual grabens range from 20 to 350 m most estimates of the thickness of the faulted layer range from 0 5 to 4 5 km average is 1 5 km this thickness range corresponds closely to the 0 8 to 3 6 km range in depth for pits troughs and canyons in noctis labyrinthus and along the walls of valles marineris we propose that the predominant 1 to 1 5 km values obtained for both the thickness of the faulted layer and the depths of the pits troughs and theater heads of the canyons reflect the initial depth to the water table in this region as governed by the depth to the base of ground ice maximum depths for these features may indicate lowered groundwater table depths and the base of ejecta material

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

oblique rifting at tempe fossae mars this work shows the results of a structural study of the faults observed at the tempe rift northeastern tharsis region mars a new detailed map of faults and fault systems was used to geometrically characterize the fracture architecture of the tempe rift and to measure fault length displacement and spacing data to analyze the spatial distribution of fault centroids and to investigate the fractal nature of fault trace maps a comparison with analog models and the use of conventional techniques of fault population analysis show that the tempe rift was most probably generated under sinistral oblique rifting processes which highlights the importance of the presence of inherited fractures in the tectonic evolution of the noachian crust the angle between the extension direction and the rift axis varies along the tempe rift ranging from 50o 60o at its central southern part to 66o 88o to the southwest fault scaling relationships are similar to those found at midocean ridges on earth with exponential fault length frequency distributions localized inhomogeneous deformation generated weakly interacting faults spanning the entire thickness of the mechanical layer this thickness decreased from southwest to northeast along the rift along with distance from the central part of the tharsis dome

ground penetrating radar survey of a prehistoric site in southern italy abstract in this paper we present and discuss the results of a ground penetrating radar gpr study carried out in an area of southern italy where a karst cave with prehistoric remains was found the aim of the study involved the imaging of the subsurface stratigraphy both inside and outside the cave in order to assist archaeologists in an excavation programme the survey grid comprised 18 intersecting gpr profiles problems associated with the use of the gpr within a cave environment are highlighted and the data processing sequence designed to extract useful geo archaeological signatures is described interpretation of the radar sections was controlled by the excavation of two trenches inside and outside the cave allowing detailed outlining the complex stratigraphy and the reconstruction of palaeolithic and neolithic subsurface horizons

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

middle archaean gold deposits in the north shaw coongan greenstone belt australia the relative timing of events responsible for gold mineralisation abstract gold deposits of the mid archaean east pilbara granitoid greenstone terrane australia are unique because they characterise metallogenic evolution of the early earth in the north shaw coongan greenstone belt quartz sulphide lodes within shear and fault zones are host to gold mineralisation detailed field mapping of crosscutting structures at the sharks well mining centre and blue bar mine in the coongan greenstone belt and at the north shaw mining centre in the north shaw greenstone belt have established a relative chronology for gold deposits the results suggest that the accepted classification of regional gold mineralisation in terms of two events may need modification the sharks well mining centre is hosted by meta basalt to andesite and carbonatised quartz chlorite schist of the mt ada basalt warrawoona group ca 3 49 3 31 ga the gold bearing quartz sulphide lodes are principally situated in the shark gully shear zone the lodes and veins formed early in d1 local and prior to development of cleavage and folds gold occurs in nw trending fractures that cut across the quartz lodes and veins suggesting syn to post d1 gold mineralisation the maximum relative age of gold mineralisation at the mining centre is constrained by the age of the duffer formation which is stratigraphically younger than the mt ada basalt and dated at 3471 3463 ma the blue bar mine is hosted by quartz fuchsite schist of the central coongan shear zone which trends northerly and dips steeply eastward the mine consists of a single brecciated gold bearing quartz lode that is unconformably overlain by scree breccia and in turn by the mount roe basalt of the fortescue group ca 2 7 ga the maximum relative age of gold mineralisation at the mine is constrained by the age of the euro basalt at 3395 3325 ma while the minimum relative age is constrained by the mount roe basalt at ca 2 7 ga the north shaw mining centre consists of several gold bearing quartz lodes including the auroria and eldorado lodes as well as a number of historic gold workings alluvial and shaft mining on the plains adjacent to the shaw river the mining centre is located on the contact margin of the north shaw suite of the shaw granitoid complex the host rocks consist of contact metamorphosed basalt andesite and hornblende amphibolites five stages of local deformation are recognised in the rocks of the mining centre d1 macroscopic folding of the north shaw greenstone belt about a northerly trending fold axis d2 nne trending foliation and folds d3 development of a ne trending disjunctive cleavage folds and conjugate kinks d4 development of faults and master joints during emplacement of dykes of the black range suite d5 formation of the wnw trending callina fault zone the fault zone crosscuts mafic dykes of the black range suite which places constraints on the minimum relative age of gold mineralisation in the fault zone based on crosscutting structural relationships the relative and absolute chronology of the gold deposits in the north shaw coongan greenstone belt indicates they are not all of the same age the crosscutting structural relationships justify a review of the currently accepted event 1 or 2 classification of huston et al econ geol 97 2002 691 two new events one at 3325 2774 ma and one younger than 2 7 ga also affected the mafic and ultramafic rocks of the warrawoona group

critical taper wedge mechanics of fold and thrust belts on venus initial results from magellan fold and thrust belts exist on venus at the margins of crystal blocks such as plateaus tesserae and coronae and as ridge belts within the plains these fold belts display a number of key features that are consistent with their formation by critical taper wedge mechanics a mechanics that is well known for fold and thrust belts and accretionary wedges on earth for example an analysis of fold geometry at the toe of the artemis chasma fold belt indicates fault bend folding above a regionally extensive decollement horizon at a depth of about 1 5 km near surface deformation on venus is interpreted to be brittle and is anticipated to be dominated by cohesive strength in the upper 1 2 km critical taper wedge mechanics under anticipated venus conditions suggests that brittle wedges should have maximum surface slopes in the range 10 20 which is similar to some estimated slopes in the steep parts of the fold belts the low taper toes of fold belts may be cohesion dominated toes on either brittle or plastic decollement horizons once the base of the wedge undergoes the brittle plastic transition the surface slope is expected to flatten to near horizontal in qualitative agreement with many topographic profiles of fold and thrust belts on venus the estimated depth of the brittle plastic transition is uncertain based on rock mechanics data but is expected to be close enough to the surface to be affected by the atmospheric temperature gradient the relief of fold belts measured between the toe of the wedge and the flat crest displays a remarkable linear dependence on absolute elevation figure 15 ranging from 6 km for maxwell montes at an elevation of 10 km to a few hundred meters at the lowest planetary elevations 0 to 2 km this remarkable phenomenon appears to reflect an absolute elevation dependence of the depth of the brittle plastic transition possibly controlled by an isostatic coupling of elevation lithospheric thickness and geothermal gradient

new radar derived topography for the northern hemisphere of mars earth based radar altimetry data for the northern equatorial belt of mars 6 s 23 n have recently been reduced to a common basis corresponding to the 6 1 mbar reference surface a first look at these data indicates that the elevations of tharsis elysium and lunae planum are lower by 2 5 km than has been suggested by previous estimates these differences show that the required amount of tectonic uplift or constructional volcanism for each area is less than has been previously envisioned atmospheric or surficial conditions are suggested which may explain the discrepancies between the radar topography and elevations measured by other techniques the topographies of chryse planitia syrtis major and valles marineris are also described

plate tectonic models for indian ocean intraplate deformation abstract the equatorial region of the conventionally defined indo australian plate has long been recognized as containing a type example of intense intraplate deformation we trace the development of tectonic models for the area to illustrate techniques for the analysis of such deformation the identification of anomalous seismicity near the ninetyeast and chagos laccadive ridges demonstrated the existence of the deformation focal mechanisms from recent and historic earthquakes showed strike slip motion occurring along the ninetyeast ridge seismic moment data allowed the rate to be estimated similar studies showed north south tension in the chagos bank region and north south compression in the region between the ninetyeast and chagos ridges global plate motion studies indicated non closure of the indian ocean triple junction suggesting the conventional plate geometry was inadequate for a rigid plate description of the area gravity and marine geophysical data indicated intense north south compressional deformation south of the bay of bengal these observations are reconciled by a plate motion model in which australia and india lie on distinct plates divided by a boundary that intersects the central indian ridge near the equator in this model arabia usually considered a separate plate has negligible motion relative to india the resulting euler vector for australia relative to indo arabia lies just east of the central indian ridge and predicts approximately 0 5 1 5 cm yr compression in the central indian basin and 1 5 2 cm yr strike slip motion along the northern ninetyeast ridge consistent with the seismological and geophysical data in contrast to conventional oceanic plate boundaries the boundary deformation is distributed over a wide zone this diffuse nature may reflect either the boundary s recent inception or slow rate of motion analysis of seismicity and deformation in the boundary zone should offer insights into the mechanics of its development and its implications for the evolution of plate boundaries

tharsis dome mars new evidence for noachian hesperian thick skin and amazonian thin skin tectonics a photogeological reconnaissance of viking mosaics and images of the tharsis dome has been carried out fifteen new areas of transcurrent faulting have been located which together with other structures previously detected support a model in which the thaumasia plateau the southeastern part of the tharsis dome is proposed to be an independent lithospheric block that experienced buckling and thrust faulting in late noachian or early hesperian times as a result of an e w directed compression evidence is presented that this stress field rather than the tharsis uplift was decisive in the inception of valles marineris which we consider a transtensive dextral accident the buckling spacing permits us moreover to tentatively reconstruct a martian hesperian lithosphere similar in elastic thickness to the mean present terrestrial oceanic lithosphere thus supporting the possibility of a restricted lithospheric mobility in that period tharsis lithosphere was again subjected to shear stresses in amazonian times a period in which important accidents such as strike slip faults wrinkle ridges and straight and sigmoidal graben were formed under a thin skin tectonic regime while the lithosphere as a mechanical unit had become too thick and strong to buckle the possible causes of those stresses and especially their relationships to a putative period of plate tectonics are discussed

ground penetrating radar monitoring of a controlled dnapl release 200 mhz radar a controlled release of tetrachloroethylene was performed in a saturated natural sandy aquifer to evaluate the effectiveness of various geophysical techniques for detecting and monitoring dense nonaqueous phase liquids dnapls in the subsurface tetrachloroethylene typical of most dnapls has a low relative dielectric permittivity 2 3 which contrasts with the high relative permittivity 80 of the pore water it displaces making it a potential target for detection by ground penetrating radar gpr gpr data were acquired using 200 mhz antennas radar sections collected at different times over the same spatial location clearly show the changes induced by the movement of dnapl in the subsurface temporal changes can be examined through the evolution of a radar data trace collected at a single spatial location normal moveout analysis of common midpoint cmp data demonstrates induced changes in electromagnetic em wave velocities of up to 30 percent caused by the presence of dnapl the distribution o

integrated near surface geophysical survey of the cathedral of mallorca abstract this paper describes an integrated near surface geophysical study carried out in order to obtain high resolution images of the shallow subsurface under and around the cathedral of mallorca the study was a part of a global project focused on determining the state of the building structure and on evaluating the cathedral s dynamical behaviour natural frequencies and vibration modes ground penetrating radar gpr and the capacitively coupled resistivity method were used to obtain 2d images of the shallow subsurface refraction microtremor array measurements remi were also used to characterize the rock and soil properties and several invasive boreholes provided detailed and exact information on the stratigraphy the information from the geophysical data was used to determine a final model of the ground with indications of the most likely vulnerable zones as a part of this final model gpr profiles enabled us to delineate the superficial ground structure and to detect some archaeological features electrical resistivity imaging data were in good agreement with the gpr results and showed shallow major changes in the soil and rock under the filling materials the refraction microtremor array remi results indicate the existence of compacted soils in different areas probably corresponding to old filled zones in good correlation with gpr and resistivity profiles in the most superficial part of the ground

localization of bedding plane slip and backthrust faults above blind thrust faults keys to wrinkle ridge structure a mechanically based model for wrinkle ridge development is developed that combines wrinkle ridge morphologies regional topographic offsets suggestive of subsurface thrust faults and folding of near surface layers this model provides explicit relationships between observed morphologic elements characteristic of wrinkle ridges and plausible mechanisms in the subsurface a key component that is absent in previous qualitative fault based scenarios for these structures as developed in this paper wrinkle ridges are the surface expression of anticlines that grow above a blind thrust fault as a result of both flexural slip folding of near surface strata and the nucleation and growth of echelon arrays of backthrust faults calculations of displacements both horizontal shortening and vertical uplift and coulomb stress change related to slip along blind thrust faults in the model demonstrate physically important spatial inhomogeneities in these quantities with revealing and useful implications 1 the ratio of shortening due to folding at the surface to the shortening due to faulting at depth is characteristically small for coupled wrinkle ridge blind thrust fault systems and decreases with increasing fault depth the depth of the blind thrust fault s upper tip thus profoundly influences the surface strains 2 folding and uplifted topography forming the topographic ridge are produced above the area of the slipping blind thrust fault plane horizontal and vertical deformation at the surface extend over several ridge widths or a total of at least 50 km for a 10 km wide ridge implying that topographic profiles and geologic studies must extend sufficiently far from the wrinkle ridge to fully characterize the surface deformation 3 calculations of coulomb stress changes suggest that fault slip can localize both bedding plane slip in overlying strata and new backthrust faults that propagate upward to become wrinkles on the trailing side of the ridge initiation of bedding plane slip in association with slip along the blind thrust fault likely determines whether the resulting surface structure becomes a wrinkle ridge or a lobate scarp wrinkle ridge spacing may also be related to stress changes associated with slip along the underlying blind thrust fault

evidence for an ancient impact basin in daedalia planum mars geologic mapping has provided observations that some features on mars are morphologically similar to lunar imbrium sculpture materials these grooved features occur in clustered sets of a dozen or more are spaced 1 to 10 km apart and are unlike other linear martian features such as yardangs faults ancient valley networks and mass wasting features we propose that they represent impact materials from an ancient basin the orientations of these features were plotted as lines on a schmidt net and the density of the resulting intersections suggests a likely source area at approximately 26 0 125 0 or roughly the center of daedalia planum numerous features geologic materials and earth based radar data indicate that a basin with a diameter of approximately 4500 km with an early noachian age is centered at this location four interior rings with diameters of 1100 1500 2200 and 3200 km and an exterior ring with a diameter of approximately 6400 km were found the rings are spaced with a ratio of 2 0 1 which is similar to the basin ring spacing on the other terrestrial planets both concentric and infrequently radial basin related faults were recognized including claritas fossae gordii dorsum and the thaumasia graben faults or zones of weakness related to the basin rings may have influenced the position of the mangala valles source area and arsia mons based on the location and morphology of early hesperian to early amazonian volcanics composing daedalia planum the daedalia basin may also have extensive deep seated interior faults capable of extruding mare materials to the surface

periodic instabilities during compression or extension of the lithosphere 1 deformation modes from an analytical perturbation method we argue that the plastic rheology of the lithosphere rather than its recoverable elastic properties is responsible for the systematic development of periodic instabilities during compression or extension we use a linear perturbation model with analytical solutions to calculate the instability modes for various rheologies the growth of such periodic instabilities is enhanced by the highly nonlinear stress strain rheologies encountered in the brittle layers of the lithosphere on the contrary ductile layers deforming according to high temperature creep flow laws tend to inhibit these instabilities for oceanic domains we assume that the only brittle layer is the upper part of the lithosphere in compression the only valid instability is a buckling whose wavelength is around 4 times the thickness of the brittle layer calculated wavelengths and growth rates are consistent with observations available for the indian ocean for continental domains a reasonable assumption is the existence of two plastic layers one in the upper crust the other in the upper mantle for moho temperatures between 450 c and 600 c in compression and extension two instabilities develop a long wavelength instability involving the whole lithosphere coupling mode and a short wavelength instability involving the crust and controlled by the upper brittle layer intrinsic crustal mode in compression the coupling mode is a whole lithosphere buckling with a wavelength about 4 times the thickness of the active lithosphere the two plastic layers plus the intermediate ductile layer in extension the coupling mode is a boudinage of opposite phase in the two plastic layers and a folding of the intermediate ductile layer the intrinsic crustal mode is a crustal buckling in compression crustal boudinage in extension neither deflects the moho the intrinsic crustal mode is favored by an increase in thermal gradient and by a decrease in strength of the ductile lower crust

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers

orientation and origin of ridges in the lunae palus coprates region of mars numerous wrinkle ridges similar in appearance to lunar mare ridges occur on volcanic plains units surrounding the tharsis region of mars where they are oriented circumferential to the center of the plateau by analogy with lunar mare ridges and from morphologic evidence such as the smooth slopes of arches these features are interpreted to result primarily from compressional folding of the volcanic plains although the uppermost ridge may represent faulting of the near surface materials east of the tharsis region ridges are best developed in the lunae palus and coprates quadrangles where they can be used to indicate the degree of compressional stress occurring there comparison of ridge orientations in these quadrangles to a tharsis center at 1 n 122 w indicates that more than 60 of the total length of ridges is orthogonal to a normal from this center non orthogonal ridges are seen to have general northerly orientations after removal of the tharsis orthogonal population trends of graben in surrounding terrain indicate that non orthogonal ridges are not greatly affected by regional scale structures comparison of the frequency of orthogonal and non orthogonal ridges further suggests that loading due to the tharsis plateau was effective in producing compressional features as far as 4000 km from the center of the load additional sources for compressional stress are necessary to account for ridge systems at greater distances from the tharsis plateau

coldspots and hotspots global tectonics and mantle dynamics of venus magellan radar images and altimetry data and pioneer venus gravity data of major highlands and lowlands on venus are examined with the objective of relating these tectonic and volcanic landforms to convection within venus mantle two roughly circular lowlands atalanta and lavinia planitiae are bowl shaped depressions which contain compressional tectonic features and lack hotspot related features such as coronae and shield volcanoes they are identified as surface expressions of young mantle coldspots or regions of mantle downwelling highlands can be divided into two distinct groups volcanic rises and plateau shaped highlands volcanic rises are domical circular to elongate regions characterized by volcanic construction extensional tectonism large positive gravity and geoid anomalies centered on the highlands and large apparent depths of compensation volcanic rises include beta bell atla and western eistla regiones and are identified as surface expressions of large mantle hotspots or plumes plateau shaped highlands are steep sided elevated regions that range from circular alpha regio to elongate or irregular ovda regio tellus regio in shape their surfaces are dominated by complex ridged terrain rather than the shield volcanoes and flows that dominate volcanic rises most plateau shaped highlands contain compressional structures some of which commonly lie along their margins and have small gravity and geoid anomalies and small apparent depths of compensation compared to volcanic rises plateau shaped highlands which include those mentioned above and western ishtar terra thetis regio and phoebe regio are identified as surface expressions of mantle coldspots or regions of downwelling the highland coldspot features are elevated as a consequence of crustal thickening crustal thickening is absent or minor at lowland coldspots the importance of mantle downwelling in the tectonic deformation of venus suggests that its mantle like the mantle of earth is strongly heated from within the major venusian hotspots attest to the existence of large mantle plumes carrying heat upward from the planet s core

the origin of large local uplift in extensional regions large localized uplift is commonly observed in continental regions undergoing extension these observations can be modelled by planar high angle normal faulting of an elastic upper crust overlying an inviscid lower crust isostasy provides the necessary driving force the model quantifies the role of flexural rigidity density variations in the crust and erosion and deposition of sediment

layering stratigraphy of eastern coprates and northern capri chasmata mars abstract distinct competent layers are observed in the slopes of eastern coprates chasma part of the valles marineris system on mars our observations indicate that the stratigraphy of coprates chasma consists of alternating thin strong layers and thicker sequences of relatively weak layers the strong competent layers maintain steeper slopes and play a major role in controlling the overall shape and geomorphology of the chasmata slopes the topmost competent layer in this area is well preserved and easy to identify in outcrops on the northern rim of coprates chasma less than 100 m below the southern ophir planum surface the volume of the topmost emplaced layer is at least 70 km 3 and may be greater than 2100 km 3 if the unit underlies most of ophir planum the broad extent of this layer allows us to measure elevation offsets within the north rim of the chasma and in a freestanding massif within coprates chasma where the layer is also observed rim outcrop morphology and elevation differences between ophir and aurorae plana may be indicative of the easternmost extent of the topmost competent layer these observations allow an insight into the depositional processes that formed the stratigraphic stack into which this portion of the valles marineris is carved and they present a picture of some of the last volcanic activity in this area furthermore the elevation offsets within the layer are evidence of significant subsidence of the massif and surrounding material

claritas rise mars pre tharsis magmatism claritas rise is a prominent ancient noachian center of tectonism identified through investigation of comprehensive paleotectonic information of the western hemisphere of mars this center is interpreted to be the result of magmatic driven activity including uplift and associated tectonism as well as possible hydrothermal activity coupled with its ancient stratigraphy high density of impact craters and complex structure a possible magnetic signature may indicate that it formed during an ancient period of mars evolution such as when the dynamo was in operation as tharsis lacks magnetic signatures claritas rise may pre date the development of tharsis or mark incipient development since some of the crustal materials underlying tharsis and older parts of the magmatic complex respectively could have been highly resurfaced destroying any remanent magnetism here we detail the significant characteristics of the claritas rise and present a case for why it should be targeted by the mars odyssey mars reconnaissance orbiter and mars express spacecrafts as well as be considered as a prime target for future tier scalable robotic reconnaissance