selenophysical parameter inversion in the lunar southern hemisphere highland based on mutant particle swarm optimization abstract selenophysical parameters can be estimated based on admittance between gravity and topography especially high precision grail gravity and lola topography data these parameters include load ratio between subsurface and surface loads crustal thickness crustal density and effective elastic thickness considering non negligible membrane stress the lunar lithosphere is best modeled as a thin and elastic spherical shell taking into account of the nonlinearity of the governing equation of the shell and premature convergence of pso we introduced an updated algorithm of mpso which considers a self adaptive inertia weight and a mutation operator as commonly used in genetic algorithms ga results indicate that mpso is relatively more flexible in the choice of tuning parameters than the general algorithm of pso a low mutation probability of 0 005 is found to promote globally optimized convergence and a low value of 0 002 is employed in parameters estimation for 20 areas in southern hemisphere highland using the updated algorithm of mpso it is found that a well constrained crustal density for most of the studied regions is less than or equal to the mean crustal density 2550 kg m 3 of the entire lunar highland the relatively small crustal density is likely a result of high porosity of southern hemisphere crust the elastic thickness at studied locations far from mare basins is found to be around 7 km corresponding to the thickness at the stage of formation of highland formed from the crystallization of ancient ferroan anorthosite a large elastic thickness is on the contrary discovered surrounding mare basins the ancient lunar lithosphere developed quite thick as the moon becoming cool and it was able to elastically support new loads during the formation of mare basins the difference of elastic thickness indicates the development of lithospheric thickness at the distinct lunar evolutionary history

gravity field of the moon from the gravity recovery and interior laboratory grail mission spacecraft to spacecraft tracking observations from the gravity recovery and interior laboratory grail have been used to construct a gravitational field of the moon to spherical harmonic degree and order 420 the grail field reveals features not previously resolved including tectonic structures volcanic landforms basin rings crater central peaks and numerous simple craters from degrees 80 through 300 over 98 of the gravitational signature is associated with topography a result that reflects the preservation of crater relief in highly fractured crust the remaining 2 represents fine details of subsurface structure not previously resolved grail elucidates the role of impact bombardment in homogenizing the distribution of shallow density anomalies on terrestrial planetary bodies

palaeoseismology review of the state of the art abstract historical seismicity provides only a partial indication of the seismotectonic character i e earthquake potential of a given region even in italy where a relatively long historical record exists available catalogues are generally unsatisfactory for this purpose fortunately strong earthquakes often leave geological evidence herein referred to as seismites that are mainly related to surface faulting folding or other deformation and occasionally to secondary ground failures e g landslides liquefaction features etc these features may be preserved and therefore palaeoseismological studies may detect and date them thereby permitting extension of knowledge beyond the local historical threshold up to 2000 years in the most fortunate cases this paper provides a summary of criteria which may aid in the identification of areas suitable for palaeo earthquake investigation historical seismicity and the presence of well developed tectonic geomorphic features are recognized as the most reliable criteria for identifying active faulting however lack of these characteristics cannot be considered conclusive evidence for lack of activity palaeoseismological techniques aim at identifying not only the obvious effects of surface faulting such as offset of young geologic units but also the more subtle tectonic or non tectonic features including liquefaction structures gravity features and coseismic uplift and or subsidence finally we discuss some questions that pertain to palaeoseismicity evaluation techniques among these are the reliability of the quaternary dating techniques the evaluation of the seismic energy released minimum magnitude and principally the unequivocal identification of a seismic origin for the considered geological structures

very preliminary reference moon model abstract the deep structure of the moon is a missing piece to understand the formation and evolution of the earth moon system despite the great amount of information brought by the apollo passive seismic experiment alsep the lunar structure below deep moonquakes which occur around 900 km depth remains largely unknown we construct a reference moon model which incorporates physical constraints and fits both geodesic lunar mass and polar moment of inertia and love numbers and seismological body wave arrivals measured by apollo network data in this model the core radius is constrained by the detection of s waves reflected from the core in a first step for each core radius a radial model of the lunar interior including p and s wave velocities and density is inverted from seismic and geodesic data in a second step the core radius is determined from the detection of shear waves reflected on the lunar core by waveform stacking of deep moonquake apollo records this detection has been made possible by careful data selection and processing including a correction of the gain of horizontal sensors based on the principle of energy equipartition inside the coda of lunar seismic records and a precise alignment of sh waveforms by a non linear inversion method the very preliminary reference moon model vpremoon obtained here has a core radius of 380 40 km and an average core mass density of 5200 1000 kg m 3 the large error bars on these estimates are due to the poorly constrained s wave velocity profile at the base of the mantle and to mislocation errors of deep moonquakes the detection of horizontally polarized s waves reflected from the core and the absence of detection of vertically polarized s waves favour a liquid state in the outermost part of the core all these results are consistent within their error bars with previous estimates based on lunar rotation dissipation williams et al 2001 and on lunar induced magnetic moment hood et al 1999

paleoseismology along the 1980 surface rupture of the irpinia fault implications for earthquake recurrence in the southern apennines italy the irpinia fault was the source of the ms 6 9 1980 irpinia earthquake and produced the first unequivocal historical surface faulting in italy trenching of the 1980 fault scarp at piano di pecore a flat intermontane basin about 5 km south of the 1980 instrumental epicenter provides the first data on earthquake recurrence intervals slip per event and slip rate on a major normal fault in the southern apennines fault zone the trenches exposed evidence of four pre 1980 paleoearthquakes that occurred during the past 8600 years a best estimate average recurrence interval is 2150 years although the time interval between individual events varies by as much as a factor of 2 each paleo earthquake is similar to the 1980 surface rupture in amount of slip and style of deformation which suggests that the 1980 event is characteristic for the irpinia fault slip per event values average 61 cm the net vertical displacement of 2 12 2 36 m since 8600 cal year b p observed in the trenches gives a vertical slip rate of 0 25 0 35 mm yr a dip slip rate of 0 29 0 40 mm yr and an extension rate of 0 14 0 20 mm yr although fault behavior data are only available for the irpinia fault they provide a starting point for evaluating earthquake recurrence and rates of deformation in southern apennines they suggest that 1 fault specific earthquake recurrence intervals based on the historical seismic record overestimates the occurrence of large magnitude m7 earthquakes and 2 the holocene rate of extension across the apennines is 1 mm yr the 1980 earthquake and the paleoseismologic observations show that repeated and localized surface faulting occurs in southern apennines and leaves subtle but distinct geomorphic evidence that can be detected with detailed and careful investigation

an improved lunar gravity field model from selene and historical tracking data revealing the farside gravity features 1 a new spherical harmonic solution of the lunar gravity field to degree and order 100 called sgm100h has been developed using historical tracking data and 14 2 months of selene tracking data from 20 october 2007 to 26 december 2008 plus 30 january 2009 the latter includes all usable 4 way doppler data collected which allowed direct observations of the farside gravity field for the first time the new model successfully reveals farside features in free air gravity anomalies which are characterized by ring shaped structures for large impact basins and negative spots for large craters sgm100h produces a correlation with selene derived topography as high as about 0 9 through degree 70 comparison between sgm100h and lp100k one of the pre selene models shows that the large gravity errors which existed in lp100k are drastically reduced and the asymmetric error distribution between the nearside and the farside almost disappears the gravity anomaly errors predicted from the error covariance through degree and order 100 are 26 mgal and 35 mgal for the nearside and the farside respectively owing to the 4 way doppler measurements the gravity coefficients below degree and order 70 are now determined by real observations with contribution factors larger than 80 percent with the selene farside data coverage it is possible to estimate the gravity field to degree and order 70 without applying any a priori constraint or regularization sgm100h can be used for global geophysical interpretation through degree and order 70

constraints on the martian lithosphere from gravity and topography data localized spectral admittances of the large martian volcanoes are modeled by assuming that surface and subsurface loads are elastically supported by the lithosphere in order to model the case where the load density differs from that of the crust a new method for calculating gravity anomalies and lithospheric deflections is developed the modeled gravity anomalies depend upon the elastic thickness crustal thickness load density and crustal density and these parameters were exhaustively sampled in order to determine their effect on the misfit between the observed and modeled admittance function we find that the densities of the martian volcanoes are generally well constrained with values of 3200 100 kg m 3 which is considerably greater than those reported previously these higher densities are consistent with those of the martian basaltic meteorites which are believed to originate from the tharsis and elysium volcanic provinces the crustal density is constrained only beneath the elysium rise to be 3270 150 kg m 3 if this value is representative of the northern lowlands then pratt compensation is likely responsible for the approximately 6 km elevation difference between the northern and southern hemispheres the elastic thicknesses of the major martian volcanoes when subsurface loads are ignored are found to be the following elysium rise 56 20 km olympus mons 93 40 km alba patera 66 20 km and ascraeus mons 105 40 km we have also investigated the effects of subsurface loads allowing the bottom load to be located either in the crust as dense intrusive material or in the mantle as less dense material we found that all volcanoes except pavonis are better modeled with the presence of less dense material in the upper mantle which is indicative of either a mantle plume or a depleted mantle composition an active plume beneath the major volcanoes is consistent with recent analyses of cratering statistics on olympus mons and the elysium rise which indicate that some lava flows are as young as 10 30 myr as well as with the crystallization ages of the shergottites of which some are as young as 180 myr

internal structure of the moon inferred from apollo seismic data and selenodetic data from grail and llr the internal structure of the moon is important for discussions on its origin and evolution however the deep structure of the moon is still debated due to the absence of comprehensive seismic data this study explores lunar interior models by complementing apollo seismic travel time data with selenodetic data which have recently been improved by gravity recovery and interior laboratory grail and lunar laser ranging llr the observed data can be explained by models including a deep seated zone with a low velocity s wave velocity 2 9 0 5 km s and a low viscosity 3 1016 pa s the thickness of this zone above the core mantle boundary is larger than 170 km showing a negative correlation with the radius of the fluid outer core the inferred density of the lowermost mantle suggests a high tio2 content 11 wt which prefers a mantle overturn scenario

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

fault generated mountain fronts in the central apennines central italy geomorphological features and seismotectonic implications the morphotectonic framework of the central apennines is given by faulted blocks bounded by normal faults mostly trending nw se nnw sse and ne sw which cut previous compressive structures such a structural setting is consistent with the lbcal mechanisms of the earthquakes which often occur in this area in this paper three lithologically different normal fault generated mountain fronts are analysed in order to assess the relations between their geomorphic features and active tectonics they border the norcia depression sibillini mts umbria the amatrice ampotosto plateau laga mts lazio and the fucino basin marsica mts abruzzi the norcia depression is bounded by a n20 w trending normal fault to the east and by a parallel antithetic fault to the west the main fault has a 1000 m throw and gives rise to a wide fault escarpment characterized by l sharp slope breaks due to low angle gravity faults 2 important paleolandslides and 3 several fault scarplets on the piedmont belt affecting quaternary deposits the amatrice ampotosto plateau is delimited by the western slope of mt gorzano which runs along a n20 w trending normal fault having a 1500m throw minor parallel faults dislocate quaternary landforms large scale massmovements also occur here e the fucino basin was struck by th e 1915 avezzano earthquake 0 xi mcs which produced extensive surface faulting along two parallel nw trending normal fault escarpments on the eastern border of the basin there is paleoseismrc evidence including buried gravity graben in late glacial gravels and tectonic dip slip striations on holocene calcitic crusts covering bedrock normal fault planes these data suggest that active extensional tectonics plays a major role in the slope morphogenesis of the central apennines and they indicate the importance of geomorphic analysis in seismic zonation of this area

segmentation and configuration of subducted lithosphere in italy an important control on thrust belt and foredeep basin evolution the apennine foredeep basin system located on continental crust consists of four roughly parallel basin segments each containing a flexural outer rise and an inner trough that deepens continuously toward the thrust belt flexural modeling of subsidence data across the basin indicates that this foredeep basin results mainly from deep subsurface loads acting on the subducted slab from within the subduction zone rather than from the topographic load of the apennine mountains the geometry of the four basin segments observed within the apennine foredeep is thus inferred to reflect subduction of segmented lithosphere where each lithospheric segment corresponds to a segment of the foredeep basin beneath the basin and in the foreland the lithosphere is continuous segmentation occurs only at depth beneath the thrust belt this pattern olf segmentation of the subducted lithosphere at depth is reflected in the large scale geometry of the outer part of the apennine thrust belt and appears to control it similarly the pattern of segmentation also appears to control the position of the eastern limit of back arc type extension in western italy these relations strongly suggest a genetic relation between subduction zone processes foredeep basin geometry and thrust belt evolution in which the configuration of the subducted lithosphere largely controls the large scale surface deformation observed in the apennine system

fault plane solutions and seismicity of the italian peninsula abstract a new fault plane solution map of the italian peninsula is presented in this paper the earthquakes analyzed are included in the period 1905 1980 with magnitudes ranging 4 7 75 earthquakes are located in the crust while 31 are related to the deep and intermediate zone of the calabrian arc the large seismic events of the italian peninsula are generally associated with normal faulting while strike slip motion is mostly related to small earthquakes located along lateral segments of the mountain chain the deep and intermediate earthquakes of the tyrrhenian sea indicate predominant down dip compression and strike slip motion at the boundaries of this benioff zone this last is interpreted as a remnant of a subduction zone active since oligocene extending to 500 km depth with a very small lateral size about 300 km the present tectonics of this benioff zone is strongly conditioned by the lateral bending more so than the gravitational sinking process the coexistence of thrust and normal faulting motion associated to the earthquakes within a few tens of kilometers of each other seems to be explained by the strong lateral inhomogeneities of the crustal rocks present in this region more so than to the depth of the seismogenetic zone and the nature of the faulting process

shtools tools for working with spherical harmonics geophysical analyses are often performed in spherical geometry and require the use of spherical harmonic functions to express observables or physical quantities when expanded to high degree the accuracy and speed of the spherical harmonic transforms and reconstructions are of paramount importance shtools is a time and user tested open source archive of both fortran 95 and python routines for performing spherical harmonic analyses the routines support all spherical harmonic normalization conventions used in the geosciences including 4p normalized schmidt seminormalized orthonormalized and unnormalized harmonics along with the option of employing the condon shortley phase factor of 21 m data on the sphere can be sampled on a variety of grid formats including equally spaced cylindrical grids and grids appropriate for integration by gauss legendre quadrature the spherical harmonic transforms are proven to be fast and accurate for spherical harmonic degrees up to 2800 several tools are provided for the geoscientist including routines for performing localized spectral analyses and basic operations related to global gravity and magnetic fields in the python environment operations are very simple to perform as a result of three class structures that encompass all operations on grids spherical harmonic coefficients and spatiospectral localization windows shtools is released under the unrestrictive bsd 3 clause license

sequence stratigraphy basin dynamics and petroleum geology of the miocene from eastern tunisia on the eastern margin of tunisia miocene limestones marl and siliciclastic deposits crop out poorly and are lacking in age diagnostic faunal content the biostratigraphic and lithostratigraphic subdivisions of these series are not clearly defined a regional study of subsurface sequences of this margin cap bon gulf of hammamet and sahel by means of sequence stratigraphy and subsurface structural analyses permits the identification of seven third order sedimentary sequences of inferred langhian to messinian age the boundaries of which are characterized by downlap and onlap toplap relationships these sequences include turbidites sands and sandstones deposited in connection with eustatic sea level changes and tectonic movements of east west and south north deep se ted faults due to the alpine and atlassic paroxysm stratal sequences are organized around miocene syndepositional grabens half grabens platforms and folds occurring inside and outside of regional tectonic corridors the geodynamic evolution of miocene basins has led to the deposition of turbiditic black argillaceous source rocks and sandstone and carbonate reservoirs that present new miocene petroleum targets the basin subsidence in response to the alpine atlassic orogeny has permitted the maturation of miocene source rocks oil generation and the formation of oil traps stratigraphic pinch outs and structural enclosures on the flanks of folds and on the borders of grabens

isostatic compensation of the lunar highlands the lunar highlands are isostatically compensated at large horizontal scales but the specific compensation mechanism has been difficult to identify with topographic data from the lunar orbiter laser altimeter and gravity data from the gravity recovery and interior laboratory we investigate support of highland topography poor correlation between crustal density and elevation shows that pratt compensation is not important in the highlands using spectrally weighted admittance we compared observed values of geoid to topography ratio gtr with those predicted by isostatic models observed gtrs are 25 8 7 5 5 7 m km for the nearside highlands and 39 3 5 7 6 2 m km for the farside highlands these values are not consistent with flexural compensation of long wavelength topography or airy isostasy defined under an assumption of equal mass in crustal columns instead the observed gtr values are consistent with models of airy compensation in which isostasy is defined under a requirement of equal pressures at equipotential surfaces at depth the gravity and topography data thus reveal that long wavelength topography on the moon is most likely compensated by variations in crustal thickness implying that highland topography formed early in lunar history before the development of a thick elastic lithosphere

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

structural and stratigraphic perspectives on the uplift and erosional history of djebel cherichira and oued grigema a segment of the tunisian atlas thrust front

viscoelastic deformation of lunar impact basins implications for heterogeneity in the deep crustal paleo thermal state and radioactive element concentration 1 diverse geological characteristics found for the three major lunar provinces i e the feldspathic highlands terrane fht the south pole aitken terrane spat and the procerallum kreep terrane pkt strongly suggest their distinctly different thermal histories quantitative differences among these provinces in their early thermal histories and crustal radioactive element concentrations however are highly unknown one of the few observables that retain a record of the ancient lunar thermal structure is the viscoelastic state of impact basins this study investigates the long term evolution of basin structures using global lunar gravity field data obtained by kaguya tracking and derives constraints for 1 the paleo thermal state of impact basins and for 2 crustal column averaged radioactive element concentrations for each province our calculation results indicate that impact basins in the central anorthositic region of the fht i e the fht an require a very cold interior dt dr 20 k km 1 on the surface this result strongly suggests that the deep portion of the thick farside highlands crust is highly depleted in radioactive elements th 0 5 ppm indicating that the th rich spa basin floor crust is clearly different from the lower crust underneath the fht an and cannot be accounted for by simple exposure of the lower crust our analysis also indicates that the observed basin structure allows as high as 6 ppm of column averaged th concentration in the crust inside the pkt these results indicate that radioactive element concentrations deep in the crust probably vary greatly region by region similarly to those observed on the surface

the neogene structural evolution of the western margin of the pelagian platform central tunisia abstract the deformation front of the atlas mountains in central tunisia is a structure termed the north south axis to the west of kairouan the north south axis consists of ne sw to nne ssw trending folds and thrusts a main decollement thrust in triassic evaporites has been mapped with secondary detachment of out of sequence thrusts in tertiary rocks and backthrusts at the base of the tertiary and in upper cretaceous sediments the upper cretaceous and tertiary sediments are backfolded in the hangingwalls of the backthrusts which are in turn folded in the se verging anticlines the backthrusts are roof thrusts to passive roof duplexes and imply the extensive development of thin skinned blind se verging thrusts a similar structural style is seen further west in the tunisian atlas but major nw verging backthrusts are not exposed adjacent to the pelagian platform the thrust structures are affected by later strike slip faults the thin skinned thrusting at the deformation front is middle miocene in age and was synchronous with africa europe collision the north south axis is therefore interpreted as the frontal structure of a collision related thrust belt the thrust belt is underlain by a nw se to e w trending middle jurassic to early cretaceous rift basin with probable mid cretaceous to oligocene post rift fill the ne sw trending thrust belt is detached from nw se to e w trending syn rift basement faults but changes in thrust belt geometry across the syn rift faults indicate that basement structures have compartmentalized the thrust belt the later strike slip faulting resulted from the reactivation of the syn rift basement faults in the post collisional framework of the thrust belt

grail gravity constraints on the vertical and lateral density structure of the lunar crust we analyzed data from the gravity recovery and interior laboratory grail mission using a localized admittance approach to map out spatial variations in the vertical density structure of the lunar crust mare regions are characterized by a distinct decrease in density with depth while the farside is characterized by an increase in density with depth at an average gradient of 35 kg m 3 km 1 and typical surface porosities of at least 20 the apollo 12 and 14 landing site region has a similar density structure to the farside permitting a comparison with seismic velocity profiles the interior of the south pole aitken sp a impact basin appears distinct with a near surface low density porous layer 2 3 times thinner than the rest of the farside this result suggests that redistribution of material during the large sp a impact likely played a major role in sculpting the lunar crust

constraining the timing of alluvial fan response to late quaternary climatic changes southern tunisia the evolution of the oued es seffaia alluvial fan during the last 50 000 years is analyzed in the light of chronometric data derived from ams radiocarbon and optical dating techniques these ages have enabled the temporal constraint of the distalward progression of the intersection point the upper limit of the locus of deposition which has resulted in the telescopic segmentation of the fan comparison of these data with the late quaternary climatic history of the maghreb highlights several problems of interpretation due both to our limited knowledge of regional palaeoclimates and of the response of dryland fluvial systems to climate changes however our data provide some evidence to suggest that fan incision and formation of telescopic segments occurs in response to changes from arid to less arid conditions supporting the conclusions of some of the work from other areas

crustal structure gravity anomalies and flexure of the lithosphere in the vicinity of the canary islands summary simple elastic plate models have been used to calculate the flexure of the lithosphere caused by volcanic loading at the canary islands and sediment loading at the moroccan continental margin by comparing the calculated flexure to observations based on seismic refraction and free air gravity anomaly data constraints have been placed on the long term 106 years elastic thickness of the lithosphere te the best fit between the calculated and observed flexure in the vicinity of the canary islands is for te 20 km this value of te also explains seismic reflection data in regions that flank the island provided that the lithosphere underlying the moroccan margin is sufficiently weak te 5 km for sediment loading to contribute little to the island flexure a backstripping study in which gravity data are used to constrain the value of te supports the suggestion that the lithosphere underlying the moroccan margin like its conjugate at the baltimore canyon trough is weak although sediment loading at the moroccan margin appears therefore to have exerted little influence on the structure of the canary islands there is evidence that island flexure may have influenced the stratigraphic development of the moroccan margin especially in the region of the slope anticline a te of 20 km is about 15 km lower than would be expected on the basis of the thermal age of the oceanic lithosphere that underlies the canary islands similar low values have been reported from oceanic islands in the pacific superswell region of french polynesia where they have been attributed to re heating of the lithosphere by one or more hotspots a general e w age progression of the volcanic rocks suggests that the canary islands were also generated by a hotspot they lack however the topographic swell and gravity geoid high which usually accompanies these features one possibility is that the low te values are the result of a pre existing weakness in the oceanic crust a te of 20 km is large enough however for a significant part of the mantle to still be involved in the support of the island loads a more likely explanation is thermal weakening by a hotspot which has been localized enough to reduce te but not to produce a swell or gravity geoid high irrespective of its cause the low te suggests that oceanic lithosphere does not necessarily progressively increase its strength with age so that even 140 ma old lithosphere is vulnerable and can in some regions be significantly weakened by later thermal and mechanical processes

the terminology of structures in thrust belts abstract a review of structures and geometric relationships recognized in thrust belts is presented a thrust is defined as any contractional fault a corollary being that thrusts must cut up section in their transport direction flats are those portions of a thrust surface which were parallel to an arbitrary datum surface at the time of displacement and ramps are those portions of thrusts which cut across datum surfaces ramps are classified on the basis of their orientation relative to the thrust transport direction and whether they are cut offs in the hangingwall or footwall of the thrust lateral variations in the form of staircase trajectories are joined by oblique or lateral ramps which have a component of strike slip movement an array of thrusts which diverge in their transport direction may form by either of two propagation models these are termed piggy back propagation which is foreland directed and overstep propagation which is opposed to the thrust transport direction an array of thrust surfaces is termed an imbricate stack and should these surfaces anastamose upwards a duplex will result the fault bounded blocks are termed horses a duplex is bounded by a higher roof thrust and a lower floor thrust the intersection of any two thrust planes is termed a branch line thrusts can be classified on the basis of their relationship to asymmetric fold limbs which they cut a further classification arises from whether a particular thrust lies in the hangingwall or footwall of another one the movement of thrust sheets over corrugated surfaces or the local development of thrust structures beneath will fold higher thrust sheets these folds are termed culminations and their limbs are termed culmination walls accommodation of this folding may require movement on surfaces within the hangingwall of the active thrust these accommodation surfaces are termed hangingwall detachments and they need not root down into the active thrust this category of detachment includes dip slip hangingwall drop faults which are developed by differential uplift of duplex roofs and out of the syncline thrusts which develop from overtightened fold hinges back thrusts as well as forming as hangingwall detachments may also form due to layer parallel shortening above a sticking thrust or by rotation of the hangingwall above a ramp

lateral variations of lunar crustal thickness from the apollo seismic data set seismic waves generated by meteoroid impacts have been detected by the apollo lunar seismic network these waves are sensitive to the crustal structure beneath both the seismic stations and the impact sites we use a markov chain monte carlo algorithm in order to invert for lateral variations of crustal thickness on the moon the inversion uses travel times of seismic waves originating from multiple meteoroid impact locations previous seismic investigations constrained the crustal thickness solely for apollo stations 12 14 and 16 whereas our approach enables to estimate the crustal thickness at locations far from the apollo network and to build a first crustal thickness map based on seismic data here we compare our crustal thickness estimates based on seismic travel times to those based on inversions of the topography and gravity field both methods turn out to be coherent in the sense that highland sites possess a thicker crust than mare sites

measurements of the elastic thickness under ancient lunar terrain abstract the part of a planet s gravity that is coherent with its topography provides information about the deflection of its crust after loading and hence the resistance of its lithosphere to bending at the time the load was emplaced we used observed line of sight accelerations from lunar prospector together with the accelerations we would have expected if anomalies in the gravity field were only caused by topography to estimate the admittance and coherence between topography and gravity over several regions of the lunar nearside we then compared our estimates to what we would expect if the lithosphere behaved as a floating elastic plate or shell assuming a linear relationship between topography and gravity we found in the region surrounding the southern highland crater clavius that the data can be modeled using a thin plate with t e 12 5 km and uncorrelated loads at the surface and base of the upper crust a spherical shell model with surface loading is less satisfactory to fit the admittance adequately requires topography with wavelengths over 400 km to be formed when t e 1 km and the remainder when t e 7 5 km by contrast the apparent lack of compensation around the youngest giant impact basins requires a plate with t e 80 km or a shell with t e 25 km our results indicate the thickness of the lunar lithosphere increased from 12 km in the pre nectarian to 25 km in the nectarian

subsurface geodynamics and petroleum geology of transform margin basins in the sahel of mahdia and el jem eastern tunisia 1 geophysical structural and seismic stratigraphic analysis of the mahdia sahel of tunisia based on seismic data and sedimentologic and microtectonic field measurements reveals a dynamic basin formation from the aptian to the quaternary seismic structural and isopach mapping of seismic horizons of cretaceous and cenozoic megasequences shows the partition of the mobile graben depocenter and carbonate and siliciclastic platform basins these basins are limited by synsedimentary restrictions along strike slip faults oriented east west and north south the interplay of these wrench faults in regional transtension and transpression during the cretaceous and cenozoic induced the synchroneous opening and closing of the graben and platform basins producing large accumulatio s of black shales and turbidites and reef oolite and carbonate platform deposits this was associated with the dragging rotation and blocking of dekakilometer size blocks assimilated to lithospheric microplates these movements were accompanied by volcanism and triassic salt intrusions along the bordering active faults in the east west trending and north south trending corridors in these basins sequential inversion of basin subsidence and the superposition of rhombic basins and wrench depocenters created migrating depocenters and provided the conditions in rapidly subsiding areas for source rock maturation and later hydrocarbon migration into stratigraphic and tectonic traps the tunisian sahel domain at the northern border of the african plate is characterized by tectonic mecha isms which provide a model for tectono sedimentary basin evolution in a wrench context

discordant 14c ages from buried tidal marsh soils in the cascadia subduction zone southern oregon coast peaty tidal marsh soils interbedded with estuarine mud in late holocene stratigraphic sequences near coos bay oregon may have been submerged and buried during great m 8 subduction earthquakes smaller localized earthquakes or by nontectonic processes radiocarbon dating might help distinguish among these alternatives by showing that soils at different sites were submerged at different times along this part of the cascadia subduction zone but comparison of conventional 14c ages for different materials from the same buried soils shows that they contain materials that differ in age by many hundreds of years errors in calibrated soil ages represent about the same length of time as recurrence times for submergence events 150 500 yr this similarity precludes using conventional 14c ages to distinguish buried soils along the southern oregon coast accelerator mass spectrometer 14c ages of carefully selected macrofossils from the tops of peaty soils should provide more precise estimates of the times of submergence events

hangingwall strain a function of duplex shape and footwall topography abstract the concept of piggy back thrust tectonics implies that foreland is progressively accreted onto a developing thrust sheet during duplex formation lateral shape changes in duplexes in the hangingwall of a thrust and corrugations in the footwall will fold higher thrust sheets to give culminations and depressions balancing of parts of high level thrust sheets with lower sheets and foreland requires a sequence of extensional and compressional strains orientated normal to the thrust transport direction culmination walls will be sites of strike parallel extension subsequent adjacent culminations will compress early culmination walls which will result in a sequence of irrotational strains examples of this geometry are given from the moine thrust zone of northwest scotland the model allows a re examination of strains and hangingwall evolution in some thrust sheets in the helvetic and external zones of the alps

the origin of lunar mascon basins high resolution gravity data from the gravity recovery and interior laboratory spacecraft have clarified the origin of lunar mass concentrations mascons free air gravity anomalies over lunar impact basins display bull s eye patterns consisting of a central positive mascon anomaly a surrounding negative collar and a positive outer annulus we show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool we used a hydrocode to simulate the impact and a self consistent finite element model to simulate the subsequent viscoelastic relaxation and cooling the primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy the lunar thermal gradient at the time of impact the crustal thickness and the extent of volcanic fill

density and porosity of the lunar crust from gravity and topography 1 newly obtained gravity and topography data of the moon combined with a lithospheric flexure model that considers both surface and subsurface loading are used to place constraints on the density of the upper crust from a localized spectral admittance analysis subsurface loads are found to be relatively unimportant in the highlands and when subsurface loads are neglected the best fitting bulk densities for a number of highland regions are found to vary from 2590 to 2870 kg m 3 with a mean value of 2691 kg m 3 crustal rock densities estimated from geochemical considerations and global iron and titanium abundances imply somewhat greater densities which we interpret as porosity affecting the gravity derived bulk density estimates the average porosity in the upper few kilometers of crust is calculated to be about 7 7 which is consistent with porosity estimates of impact fractured meteorites and terrestrial impact craters

diapirism in northern tunisia abstract the diapirs of northern tunisia composed mainly of evaporitic triassic material are the result of a complex evolution initiated by local basement movements of nne ssw faults which at the end of the early cretaceous this first uplift occurring during a period without any folding of the sedimentary series is purely halokinetic such diapiric activity remained in active progress throughout the cretaceous and early tertiary causing local disturbance in the related series and then during the alpine atlas orogeny the diapiric structures underwent deformation according to their position in the orogenic area

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

geometry and kinematics of the south atlas front algeria and tunisia abstract the south atlas front is the structural boundary between the sahara platform and the atlas mountains it is frequently indicated as a foreland dipping monocline known as the sahara flexure earlier work generally considered that such a cover structure resulted from direct inversion of basement faults this assumption is not applicable to the studied area which is situated close to the algeria tunisia border our study demonstrates a thin skinned style characterised by ramp related folds ten parallel balanced cross sections give an interpretation for the south atlas front from negrine to gafsa about 100 km along strike the geometry at depth of each cross section is defined by forward modelling of each individual anticline the depth to detachment is defined using the geometric characteristics of the fault propagation folds well exposed along the deformation front in all sections the modelling is consistent with basal decollements located within cretaceous stratigraphic levels lateral changes of the tectonic style accommodated by tear faults are observed they seem related to lateral variations in the efficiency of the based decollement faults inducing either a jump of the decollement to another level or the development of en echelon folds the modelling predicts small rotations of cover sheets separated by large scale tear faults

late quaternary climatic reconstruction for the maghreb north africa abstract the paleoclimatic evolution of the maghreb since 40 000 yr b p is not yet known in great detail for that purpose data from more than 35 sites have been collected although only about 11014c dates and a few prehistoric remains can be used to correlate these data however the sites are well distributed over the maghreb and the convergent results from paleosoils paleolakes alluvian or eolian deposits pollen analysis etc induce one to draw up a certain pattern in climatic evolution for the period between 40 000 and 20 000 yr b p the data are still fragmentary but are concordant in indicating wetter environments generalized as far as the northern sahara the effect of dropping temperatures on the increasing water budget and soil moisture is not yet clear but rainfall could have been more regular and more abundant as a consequence of the shifting of middle latitude cyclone paths towards the south in both summer and winter the environmental indicators show that between about 20 and 18 000 yr b p rainfall progressively became more irregular however proofs of aridity in the south maghreb and the northern sahara is evident only for the period between 12 10 000 yr b p at that time the saharan high pressure belt was reinforced and well established at higher latitudes than at present this dry climate lasted more or less until the thermal optimum after 6000 yr b p there is some evidence that the climate became wetter again but the environmental conditions were rather different from those of before 20 000 yr b p for instance the middle holocene dark humic sois are the result of a pedogenesis different from that of the late pleistocene reddish paleosoils for the last two millennia it is not easy to distinguish between a natural trend towards aridification and desertification through man s intervention

isostasy of the moon from high resolution gravity and topography data implication for its thermal history 1 the lunar prospector line of sight acceleration data after terrain correction have been inverted to the high resolution bouguer gravity anomalies of the lunar nearside lithospheric thicknesses of the early moon were investigated by comparing the gravity anomalies of craters and impact basins of various dimensions the lithosphere was already thick enough to support craters with diameters up to 300 km in the pre nectarian and nectarian periods degree of isostatic compensation of larger impact basins suggested lithospheric thickness of 20 60 km at that time which depended more on localities rather than age differences

role of membrane stresses in the support of planetary topography the principal purpose of this paper is to examine whether membrane stresses can support topographic loads on planetary elastic lithospheres it is found that the ability of a spherical shell to support loads through membrane stresses is determined by the nondimensional parameter ed gr2 where d is the thickness of the elastic lithosphere is the density difference between the mantle and crust and r is the radius of the planetary body when this parameter is large membrane stresses can fully support topographic loads without flexure and when it is small the influence of membrane stresses can be neglected solutions of the equation governing the behavior of a spherical shell are obtained for a topographic load expressed in terms of spherical harmonics spherical harmonic expansions of the measured gravity and topography for mars and the moon are compared with the theory it is found that for mars the support of topography is primarily due to membrane stresses for n 8 and for the moon for n 17 for mars the data for 4 n 7 give 0 5 for the moon the data have considerable scatter that is attributed to the mascons but generally correlate with 0 5 if bending stresses are neglected the governing equation for the deflection of the spherical shell is legendre s equation a general solution is obtained for an axisymmetric load this solution is applied to the tharsis region on mars the 60 65 compensation of this region requires that 0 6 the well defined fracture pattern surrounding the tharsis region is attributed to tensional membrane stresses

lake levels and climate for the last 30 000 years in the fucino area abruzzo central italy a review abstract lake fucino was in a closed basin that was drained in 1875 a review of published data as well as new geological and geomorphological studies are used to define changes in lake level over the last 30 000 years the changes are summarized as follows 1 a general rise of level between 33 000 and 18 000 20 000 yr b p 2 a general lowering between 18 000 20 000 and 7500 6500 yr b p 3 a rise between 6000 5000 yr b p 4 a lowering between 5000 2800 yr b p 5 a rise between 2800 2300 yr b p 6 lower between 2300 1800 yr b p 7 very low levels in the 16th century and 8 a rise during the 1750 1861 period of the so called little ice age lake level fluctuations are attributed to climatic variations in particular there is a clear link between fluctuations and changes in seasonal insolation produced by the orbital parameters of the earth precession of the equinoxes and obliquity of the ecliptic and average annual rainfall the fluctuations of lake levels do not seem to have been influenced significantly by tectonic movements affecting the fucino plain or by karst drainage pits present along the periphery

trench investigations of the 1915 fucino earthquake fault scarps abruzzo central italy geological evidence of large historical events earthquake hazard analyses in italy are mainly based on historical seismic catalogs however the completeness of the italian catalog which spans more than 2000 years progressivcly decreases going back in time in the fucino basin historical research has not produced evidence of large earthquakes before the january 13 1915 event m s 7 0 33 000 people killed this event generated surface faulting along at least two parallel quaternary normal faults bounding the eastern side of the basin the celano gioia and parasano cerchio faults over an end to end length of about 23 km with a downthrow of 30 90 cm toward southwest to improve geological aspects of the seismic history of this area we trenched onc of the coseismic scarps along the celano gioia fault at a trench site near the village of san benedetto de marsi the fault traverses the area formerly covered by the fucino lake drained for farming in 1875 a d the evidence collected in the trenchcs suggests at least two large events in historical times before 1915 radiocarbon dates constrain the age of event b between the 6th and the 9th centuries a d possibly coinciding with the cvent felt in rome in 801 a d molin arid guidoboni 1989 event a probably occurred after the 10th ccntury a d and almost certainly before the 1349 a d earthquake because historical studies show 1 that event a was not produced during the earthquake sequence that occurred in central italy in 1349 a d molin and guidoboni 1989 and 2 that the post 1349 seismic catalog can be regarded as complete for surface faulting earthquakes surface displacements determined for events a and b compared to the 1915 surface faulting indicate that m 6 5 earthquakes were associated with each rupturc these obscrvations suggest that the return period for large earthquakes in the fucino basin is shorter than that indicated by the historical record alone the fucino example clearly shows that thc cxceptionally long historical record in italy is still inadequate for a comprehcnsive seismic hazard characterization

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

first order kinematic elements in tunisia and the pelagian block abstract the effects of post collisional deformation in tunisia and the pelagian block are shown to be pervasively distributed over wide areas major structural provinces of the peri mediterranean mountain chains or localized in narrow belts major structural boundaries a redefinition and reinterpretation of the tell and atlas provinces the north south axis and the gafsa tozeur belts in tunisia and the rift zone in the strait of sicily help to understand both the tectonic significance of distinctive structural associations which in the past were thought to be not compatible with the kinematics of the europe africa system in neogene time and their role as first order kinematic elements during the post collisional deformation history of the central mediterranean region

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

structural evolution of djebel debadib anticline a clue to the regional tectonic style of the tunisian atlas djebel debadib is a northeast trending anticline in the tunisian atlas near el kef tunisia the core of the anticline consists of a deformed triassic gypsum matrix breccia containing clasts of supratidal dolomite terrigeneous clastic rocks and ophites metabasites locally low grade metasedimentary rocks occurring as clasts in the evaporite may represent fragments of basement rock plucked from salt subcrop during deep seated flowage the multiply deformed triassic rocks are juxtaposed against cretaceous or younger rocks and jurassic and neocomian strata are not present in outcrop these characteristics have been cited in many studies to suggest a history of diapirism to explain both the internal structure of the triassic rocks and the contact relations with the younger rocks a previously unreported unconformity developed on the triassic rocks and overlain by aptian albian strata indicates that an important period of piercement occurred during the early cretaceous for the djebel debadib diapir from the mid cretaceous to the late eocene the continental margin of northern tunisia was a regional basin in which a thick sequence of carbonate rocks was deposited beginning in late oligocene time sandy clastic sediments accumulated on the older carbonate rocks above a regional unconformity and during the middle miocene atlas orogeny numerous northeast southwest folds deformed the rocks of the tunisian trough including the diapiric triassic masses these folds commonly boxlike in geometry were extensively faulted during the late miocene and pliocene a four phase tectonic model is recognized for the tunisian atlas 1 early mesozoic rifting of the north african continental margin 2 diapiric emplacement of the late triassic liassic evaporites into overlying strata beginning in the early cretaceous 3 folding of the cover strata in response to regional compression culminating in the middle miocene atlas orogeny 4 the development of transvers grabens during late orogenic normal faulting latest miocene to recent a major regional decollement is not considered necessary to account for the shortening of the sedimentary cover during the middle miocene deformation rather the principal driving mechanism of regional crustal shortening was the reactivation of early mesozoic normal faults as reverse faults that displaced basement rocks this model implies that the small amount of shortening recorded in the tunisian atlas involved active shortening and structural thickening of basement and the concurrent deformation of the sedimentary cover

out of sequence thrusts out of sequence thrusts oost are those thrusts which do not obey the foreland propagating or in sequence deformation style they include both isolated thrusts which develop hindward of the thrust front and sequences of break back thrusts which propagate from the foreland to the hinterland two end members of a series of oost types are recognized 1 older in sequence thrusts which are reactivated along their entire length and 2 completely new thrusts which propagate through already deformed thrust sheets between the two end members are thrusts composed partially of reactivated in sequence thrust sequences and partially of new entirely out of sequence segments oosts can be initiated for a variety of reasons including 1 keeping the orogenic wedge at critical taper 2 break back sequences from the suture zone in the overriding plate 3 ramping to overcome a sticking point which inhibits in sequence thrust propagation and 4 during simultaneous displacement along two stacked thrusts culminations which bow up segment of the upper thrust may be chopped through to permit continued displacement on the upper thrust many different types of thrust behavior including gravity sliding plucking and derivation of isolated horses from ramps may mimic some of the characteristics of oosts consequently it may be difficult to conclusively prove an oost origin for a complex thrust geometry

density and lithospheric thickness of the tharsis province from mex mars and mro gravity data 1 radio science tracking of mars express mars experiment and mars reconnaissance orbiter produced high resolution martian gravity data applying localized spectral analysis on the new gravity data sets we study the surface density and lithospheric elastic thickness in the tharsis province the gravity signal is predicted with geophysical models either including bottom loading top bottom model or taking into account the loading history top top model volcanic shields are mainly composed of high density lava but their construction could have begun with lower density lava with the exception of ascraeus mons which has a top of lower density buoyant bottom loading may have been present in the form of a mantle plume under olympus mons the elastic thickness was much larger at olympus mons than at other volcanoes suggesting large spatial variations of heat flux during the hesperian alternatively small elastic thicknesses could be artifacts reflecting the presence of very localized high density crustal intrusions beneath the volcanoes thaumasia highlands were probably supported by a mantle plume at the time of formation in valles marineris top bottom models predict low densities and large elastic thicknesses in conflict with the basaltic rock composition and hesperian age of the valley dense mafic dikes underlie the western part of the valley the top top model serves to test another scenario in which the trough is formed with sedimentary infilling removed much later by erosion the elastic thickness increasing in between at the large volcanoes the relation between gravity and topography is anisotropic probably because of density variations

long wavelength topographic relaxation for self gravitating planets and implications for the time dependent compensation of surface topography the support of planetary surface topography is controlled by the thickness of the elastic lithosphere and thus has implications for the thermomechanical structure of shallow planetary interiors previous analyses of the support of long wavelength topography have generally utilized elastic formulations which preclude consideration of the time evolution of lithospheric stresses and thermal state here we formulate a viscoelastic model for the support of topography on a spherical planet our stress relaxation model employs a multilayer linear viscoelastic rheology and includes the effect of self gravitation in these models we approximate internal rheology with an olivine flow law and we estimate the internal thermal structure assuming simple conductive cooling we analyze how relief at the surface and internal density interfaces evolves with time in response to a surface or internal load our analysis demonstrates that crustal compensation is strongly dependent on planetary radius with a tendency for a large terrestrial planet like earth to reach complete airy isostasy at long wavelengths within a time scale controlled by the mantle viscosity the correlation of degree of compensation with planetary radius is consistent with previous work turcotte et al 1981 which showed that membrane stress can support significant long wavelength gravity anomalies applied to the moon the degree of compensation associated with loading of 100 ma lithosphere is less than 0 3 and the load love numbers are greater than 0 6 for all harmonics including degree 2 even after 109 years of relaxation this conclusion does not change significantly even with a moderately low viscosity for the crust the tendency for a small body like the moon to support long wavelength stresses may be relevant in understanding the anomalously large degree 2 terms in the lunar shape the results also suggest that major impact basins would not be compensated throughout lunar geological history 4 b y even if the surfaces on which the basins were initially formed were relatively young i e 100 300 ma the fact that the south pole aitken basin is largely compensated suggests that the lateral variations in thermal and or mechanical structure induced by impact processes play significant roles in the compensation of this structure

scattering attenuation profile of the moon implications for shallow moonquakes and the structure of the megaregolith abstract we report measurements of the attenuation of short period seismic waves in the moon based on the quantitative analysis of envelope records of lunar quakes our dataset consists of waveforms corresponding to 62 events including artificial and natural impacts shallow moonquakes and deep moonquakes recorded by the four seismometers deployed during apollo missions 12 14 15 and 16 to quantify attenuation and distinguish between elastic scattering and inelastic absorption mechanisms we measure the time of arrival of the maximum of energy t max and the coda quality factor q c the former is controlled by both scattering and absorption while the latter is an excellent proxy for absorption consistent with the strong broadening of seismogram envelopes in the moon we employ diffusion theory in spherical geometry to model the propagation of seismic energy in depth dependent scattering and absorbing media to minimize the misfit between predicted and observed t max for deep moonquakes and impacts we employ a genetic algorithm and explore a large number of depth dependent attenuation models quantified by the scattering quality factor q sc or equivalently the wave diffusivity d and the absorption quality factor q i the scattering and absorption profiles that best fit the data display very strong scattering attenuation q sc 10 or equivalently very low wave diffusivity d 2 km2 s in the first 10 km of the moon these values correspond to the most heterogeneous regions on earth namely volcanic areas below this surficial layer the diffusivity rises very slowly up to a depth of approximately 80 km where q sc and d exhibit an abrupt increase of about one order of magnitude below 100 km depth q sc increases rapidly up to approximately 2000 at a depth of about 150 km a value similar to the one found in the earth s mantle by contrast the absorption quality factor on the moon q i 2400 is about one order or magnitude larger than on earth our results suggest the existence of an approximately 100 km thick megaregolith which is much larger than what was previously thought the rapid decrease of scattering attenuation below this depth is compatible with crack healing through viscoelastic mechanisms using our best attenuation model we invert for the depth of shallow moonquakes based on the observed variation of t max with epicentral distance on average they are found to originate from a depth of about 50 km 20 km which suggests that these earthquakes are caused by the failure of deep faults in the brittle part of the moon

structures and tectonics of tunisia abstract in the tunisian atlas nothing is known about the nature of the acoustic basement and in the saharan cratonic part only a few deep exploration wells have reached the precambrian below a thick unfolded palaeozoic sequence north of the craton a major set of faults w e or wnw ese represents the southern limit of palaeo tethys thick sequences of marine late carboniferous and permian were developed below the jeffara and chott jerid triassic evaporites are thick below the tunisian atlas which has enabled detachment of the cover from the basement and folding into plis de couverture structures large diapiric intrusions are known especially in the northwestern sillon tunisien tunisian trough from east to west there is a progressive variation from the stable platform on the eastern side to the unstable shelf of western tunisia between these a zone of tectonic instability named the north south axis corresponds to a deep fault system that acted as a positive suture characterized by tilted blocks gaps in sedimentation and reduced or condensed sequences in the north the unstable shelf of western tunisia grades to the deep furrows where the sediments now forming the tellian and numidian nappes were deposited these nappes overthrust the autochthonous foreland during the miocene orogeny the main folding took place in the pliocene and early pleistocene recent tectonic activity occurs along the main fault zones

on the ages of humid holocene and late pleistocene phases in north africa remarks on late quaternary climatic reconstruction for the maghreb north africa by p rognon discussion sur l article de rognon p paru en 1987 dans palaeogeogr palaeoclimatol palaeoecol vol 58 p 11 34

ancient selenophysical structure of the grimaldi basin constraints from grail gravity and lola topography abstract the grimaldi impact basin is located near the western limb of the moon and lies to the southwest of the oceanus procellarum a clearly visible positive gravity anomaly exists in its low lying inner wall implying a subsurface mass concentration beneath the crater exploration of this basin could extend our meaningful and fundamental understanding of giant impact processes as well as the structure of mare basins craters limited by the low resolution of previous gravity field models it was once impossible to explore the structure beneath grimaldi the recent high resolution gravity data from the gravity recovery and interior laboratory mission make it possible to break through this barrier prior to our investigation of the selenophysical structure around crater grimaldi we developed a flexure model that includes surface and subsurface loads a localized admittance analysis was performed by combining high resolution gravity data with the high resolution topography data obtained from lunar orbiter laser altimeter within 2 std error constraints we estimated the best fit parameters over grimaldi as well as two other places in its neighborhood all the predicted admittances show a goodness of fit with their corresponding observations the large load ratio 9 2 found at the grimaldi is an indirect mirror of the dominant subsurface load consistent with its large positive gravity anomaly in its low lying floor not only the crustal thickness of 48 km but also the crustal density of 2500 kg m 3 found around grimaldi shows a great accordance with the recent results of grail given the best fit parameters of f bc and c the elastic thickness te is found to be around 28 km over grimaldi taking into account the best fit values in its neighborhood a regional elastic thickness of 30 km could be roughly concluded around grimaldi which is completely in the previous ranges 20

subsurface structures of large volcanic complexes on the nearside of the moon a view from grail gravity abstract the lunar nearside large volcanic complexes such as the rumker hills aristarchus plateau and marius hills are likely sites of intense and sustained magmatic activity these volcanic complexes recently proposed to be shield volcanoes are generally located at regionally high elevations and some feature relatively well localized positive gravity anomalies applying localized spectral analyses on high resolution gravity data obtained from the gravity recovery and interior laboratory grail mission and topography data returned from the lunar reconnaissance orbiter lro spacecraft we study the subsurface structures of these volcanic complexes the gravity signal is predicted using a thin elastic lithospheric model that considers both surface and subsurface loads best fit crustal and load densities show that the topographic highs of rumker hills marius hills gardner and kepler are mainly composed of material that has a density of more than 2850 kg m 3 which is consistent with that of emplaced igneous rocks both the aristarchus plateau and hortensius have relatively lower crustal and surface load densities with mean values around 2550 kg m 3 which are well consistent with the average bulk density of the lunar highland crust these results together with evidence of multiple volcanic edifices on the surface suggest that the shallow crusts of the rumker hills marius hills gardner and kepler are mainly composed of dense intrusive extrusive magmatic units and those of the aristarchus plateau and hortensius are mainly composed of low density materials with only small amounts of superimposed volcanic material to further constrain the subsurface structures beneath these volcanic complexes we analyze the bouguer gravity anomalies for these regions results show that dense materials that might be solidified intrusions exist beneath rumker hills marius hills gardner and prinz but no substantial dense materials have been detected beneath the aristarchus plateau hortensius kepler or cauchy the different subsurface structures among these large volcanic complexes suggest that the volcanism style at the lunar nearside is different from each other even for those formed at the same geological time

tectonic framework of disturbed belt of west central montana the disturbed belt of west central montana consists of a zone of laramide late cretaceous early tertiary convex eastward thrusts and folds that include the major eldorado lombard overthrust that has brought precambrian rocks of the belt supergroup eastward over paleozoic and mesozoic strata most of the disturbed belt is east of and structurally below the eldorado lombard overthrust deformed rocks range in age from middle precambrian proterozoic or y to early tertiary this part of the disturbed belt forms a salient that extends eastward into the foreland and is bounded on the north by thrusts having a left lateral component of movement and on the south by folds characterized by right lateral shift deformation is most intense in the western part of the disturbed belt and dies out eastward where gentle folds merge with structures of the rocky mountain foreland this salient appears to be underlain by an eastward yielding decollement fault that merges with tear thrusts on the north and dies out in the subsurface beneath the folds marking the eastern and southern margins of the disturbed belt deformation resulted from piling up of imbricate thrusts and folds where the major eldorado lombard overthrust sheet of the cordilleran orogene moved upward and onto the foreland margin thus the strata of the disturbed belt have been crumpled and deformed independently of the basement rocks with crustal shortening above the decollement hydrocarbon exploration in this area should be guided by the tectonic features described in subsequent sections of this paper thrusts in the western part of the disturbed belt have displacements of several miles and may conceal structures beneath the thrusts but in the eastern part of the area thrusts have smaller displacements and probably do not conceal major structures below some anticlines are broken by subsidiary thrusts resulting in offset axial surfaces at depth also many folds have inclined axial surfaces and the fold axes therefore will migrate with depth

hillslope gradient particle size relations evidence for the formation of debris slopes by hydraulic processes in the mojave desert this study is concerned with debris slopes free of superincumbent cliffs or basal stream channels and developed on closely jointed and or mechanically weak rocks in the mojave desert analyses of the relation between hillslope gradient s and mean particle size bar d reveal that the slope coefficient of the relation varies with debris slope plan form and where plan form is constant the intercept varies with rock type a theoretical model is developed which shows that the observed pattern of variation in the slope of the s bar d relation with plan form is consistent with the debris slopes being formed by and adjusted to hydraulic processes debris slopes in the mojave desert appear to lie along a continuum at one end are debris slopes underlain by closely jointed and or mechanically weak rocks such as those examined in this study that are transport limited well adjusted to present hydraulic processes and exhibit a strong relationship between s and bar d at the other end are debris