gravity anomalies and segmentation of the continental margin offshore west africa the free air edge effect anomaly at passive continental margins provides constraints on the thermal and mechanical properties of the lithosphere in extensional regions like many margins the edge effect high offshore gabon west africa is located at the shelf break in the region of maximum sediment thickness gabon differs however from other margins in that the edge effect low is displaced from over the continental rise to the slope the origin of the low has been investigated by backstripping the sediments at the margin we have used the backstrip to calculate the amount of crustal thinning assuming airy isostasy such a model implies zero strength during rifting alternatively this amount of crustal thinning can be explained by a strong margin and a depth of necking that exactly balances the upward and downward forces that act on the crust during rifting we have developed a method which takes into account variations in the strength during rifting and the depth of necking to compute the thinning directly from the sediment backstrip the backstrip and the crustal thinning have been used to calculate the rifting gravity anomaly differences between the backstrip and the present day water depth give the geometry of the sediment load and hence the contribution to the gaavity anomaly of sedimentation by comparing the combined rifting and sedimentation anomaly to the observed free air gravity anomaly we have been able to constrain the flexural rigidity and equivalent elastic thickness te of the lithosphere during and after rifting the best fitting model is one in which the low is caused by a 125 km wide zone of relatively thin i e 15 km continental crust which was weak i e 0 te 10k during rifting and has remained so since then we speculate that the weak zone extends for 350 400 km along strike of the gabon margin and that passive margins may be highly segmented as regards their long term strength

fault reactivation and rift localization northeastern gulf of aden margin 1 the gulf of aden and the sheba spreading ridge gulf of aden forms the southern boundary of the arabian plate its orientation 075 e and its kinematics about 030 e divergence are interpreted as the result of an oblique rifting in this contribution a field study in the northeastern gulf of aden allows us to confirm the oligo miocene synrift directions of extension and to precise the normal fault network geometry the synrift extensions are 020 e and 160 e possibly in this chronological order the normal faults strike 070 e 090 e and 110 e the results show that some characteristics are consistent with oblique rifting analogue models while some others are not especially fault reactivation of mesozoic structures is shown to have occurred significantly at the beginning and during rifting these data are therefore compared to analogue models of oblique reactivation and this comparison demonstrates that fault reactivation played a key role during the early stage of the gulf of aden rifting finally scenarios of the lithospheric evolution during the eastern gulf of aden opening preexisting weaknesses in the lithosphere or not are discussed to better constrain the deformation history of the northern margin especially we show that rift localization processes may imply stress rotations through time

oblique convergence during the cimmerian collision evidence from the triassic aghdarband basin ne iran abstract the lower middle triassic aghdarband basin ne iran consists of a strongly deformed arc related marine succession deposited along the southern margin of eurasia in a highly mobile tectonic context this basin is a key area for the study of the cimmerian events as the triassic units show severe deformations which occurred short time after the collision of iran with eurasia and were sealed by the middle jurassic succession in this work we document the structural setting and evolution of this area based on detailed mesoscopic structural analyses of faults and folds paleostress reconstruction and revision of the triassic stratigraphy the triassic sequences are deeply involved in a n verging thrust stack interacting with an important left lateral transpressional fault zone characterized by strike slip faults vertical folds and high angle reverse faults generating intricate positive flowers systematic folds asymmetry indicates that they developed in a left lateral transpressional zone coeval to thrust imbrication to the south due to a marked strain partitioning the extent of the transpressional zone shows that important left lateral movements developed parallel to the belt during the cimmerian collision in response to oblique convergence between iran and eurasia inversion of triassic syn sedimentary faults possibly inherited from palaeozoic structures of the kopeh dagh basement and favouring strain partitioning is suggested by unconformities significant differences in the sedimentary successions repeated olistoliths scarp related coarse breccias and rapid tectonic drowning occurring especially along the northern tectonic boundary of the basin paleostress analyses point to a complex stress pattern showing a 45 rotation of the stress field along the left lateral fault system related to a complete deformation partitioning in two domains respectively characterized by pure reverse dip slip and strike slip motions the main direction of compression possibly oriented ne sw in present days coordinates favoured the development of large shear zones disrupting the eastern portion of the cimmerian orogen

anatomy structural evolution and slip rate of a plate boundary thrust the alpine fault at gaunt creek westland new zealand minimum slip rates calculated for plate vector parallel slickenside trends in cataclasite on the sole of the alpine fault at gaunt creek westland new zealand range from 18 to 24 mm yr between half and two thirds of the total relative motion between the pacific and australian plates is being accommodated by movement on a single structure the alpine fault during the past 14 ka the leading edge of the alpine fault has changed from a moderately southeast dipping oblique reverse fault to a shallowly dipping thrust the hanging wall pacific plate is composed of a gradational sequence from basal gouge through pseudotachylite bearing cataclasite to progressively more coherent schist derived mylonite which has been faulted against subhorizontally bedded fluvio glacial gravel in the footwall australian plate during uplift the hanging wall sequence has been internally sheared and imbricated producing duplex structures and retrogressively veined and altered by pervasive hydrothermal fluid flow erosion of the exhumed fault zone produced angular cataclasite and mylonite derived talus fan breccias building a west dipping apron beneath the fault scarp wood fragments from near the base off the talus breccias have been 14 c dated at 12 650 90 yr b p progressive tectonic shortening resulted in 180 m of overthrusting of a schist derived nappe across an irregular talus fan surface composed of its own erosional debris the structural history of the alpine fault at gaunt creek illustrates the importance of the interaction between fault induced topography and erosion and the control these processes exert on the continued tectonic geometric and geomorphic evolution of the fault zone

regional seismic wave propagation lg and sn and pn attenuation in the arabian plate and surrounding regions an edited version of this paper was published by blackwell publishing copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02246 x http atlas geo cornell edu middleeastnorthafrica publications al damegh2004 htm

why did arabia separate from africa insights from 3 d laboratory experiments abstract we have performed 3 d scaled lithospheric experiments to investigate the role of the gravitational force exerted by a subducting slab on the deformation of the subducting plate itself experiments have been constructed using a dense silicone putty plate to simulate a thin viscous lithosphere floating in the middle of a large box filled with glucose syrup simulating the upper mantle we examine three different plate configurations i subduction of a uniform oceanic plate ii subduction of an oceanic continental plate system and iii subduction of a more complex oceanic continental system simulating the asymmetric africa eurasia system each model has been performed with and without the presence of a circular weak zone inside the subducting plate to test the near surface weakening effect of a plume activity our results show that a subducting plate can deform in its interior only if the force distribution varies laterally along the subduction zone i e by the asymmetrical entrance of continental material along the trench in particular extensional deformation of the plate occurs when a portion of the subduction zone is locked by the collisional process the results of this study can be used to analyze the formation of the arabian plate we found that intraplate stresses similar to those that generated the africa arabia break up can be related to the neogene evolution of the northern convergent margin of the african plate where a lateral change from collision mediterranean and bitlis to active subduction makran has been described second intraplate stress and strain localization are favored by the presence of a weakness zone such as the one generated by the afar plume producing a pattern of extensional deformation belts resembling the red sea gulf of aden rift system

crustal geometry of the northeastern gulf of aden passive margin localization of the deformation inferred from receiver function analysis summary here we use receiver function analysis to retrieve crustal thickness and crustal composition along the 35 my old passive margin of the eastern gulf of aden our aims are to use results from the 3 d seismic array to map crustal stretching across and along the aden margin in southern oman the array recorded local and teleseismic events between 2003 march and 2004 march seventy eight events were used in our joint inversions for vp vs ratio and depth the major results are 1 crustal thickness decreases from the uplifted rift flank of the margin towards the sheba mid ocean ridge we found a crustal thickness of about 35 km beneath the northern rift flank this value decreases sharply to 26 km beneath the post rift subsidence zone on the salalah coastal plain this 10 km of crustal thinning occurs across a horizontal distance of less than 30 km showing a localization of the crustal thinning below the first known rifted block of the margin 2 a second rift margin transect located about 50 km to the east shows no thinning from the coast to 50 km onshore the lack of crustal thickness variation indicates that the maximum crustal stretching could be restricted to offshore regions 3 the along strike variations in crustal structure demonstrate the scale and longevity of the regular along axis rift segmentation 4 extension is still observed north of the rifted domain 70 km onshore from the coast making the width of margin larger than first expected from geology 5 the crust has a felsic to normal composition with a probably strong effect of the sedimentary layer on the vp vs ratio comprised between 1 67 and 1 91

cooperative inversion of geophysical data geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters both seismic and potential field model responses can be influenced by the adjustment of the parameters of the rock properties the objective of this cooperative in version is to obtain a model which is consistent with all available surface and borehole geophysical data al though inversion of geophysical data is generally non unique and ambiguous we can lessen the ambiguities by inverting all available surface and borehole data this paper illustrates this concept with a case history in which surface seismic data sonic logs surface gravity data and borehole gravity meter bhgm data are ad equately modeled by using least squares inversion and a series offorward modeling steps the traditional analysis of various geophysical data sets has been termed integrated interpretation such analysis has traditionally involved much processing modeling and subjec tive interpretation in order to develop a geologic model which is consistent with various surface and borehole geophysical data a method which automates some of the above pro cedures is least squares inversion this procedure perturbs an initial set of model parameters in order to fit the observed data least squares inversion is described in many papers in cluding those of jackson 1972 wiggins 1972 jupp and vozoff 1975 and lines and treitel 1984 this inversion technique could also be termed automated iterative mod eling in terms of modeling different geophysical data sets there are many possible approaches which allow inversion of a given data set and it is doubtful whether one single recipe will prove suitable for all problems nevertheless by jointly invert ing various types of geophysical observations we may lessen the extent of some of the ambiguities inherent in individual data sets lafehr 1984 gives a germane discussion of several reasons for this type of coordinated geophysical effort in the present study we define cooperative inversion as the esti mation of a subsurface model which is consistent with various independent geophysical data sets in the case discussed in this paper these data sets include surface and borehole observa tions of the seismic and gravity responses in our definition cooperative inversion may include either joint inversion or sequential inversion

seismic tomography constrained by bouguer gravity anomalies applications in western washington tomographic inversions for velocity variations in western washington indicate a high correlation with surface geology and geophysical measurements including gravity observations by assuming a simple linear relationship between density and velocity birch s law it is possible to calculate the gravity field predicted from the velocity perturbations obtained by local tomographic inversion while the predicted gravity matches observations in parts of the model the overall correlation is not satisfactory in this paper we suggest a method of constraining the tomographic inversion to fit the gravity observations simultaneously with the seismic travel time data the method is shown to work well with synthetic data in 3 dimensions where the assumption of birch s law holds strictly if the sources of the gravity anomalies are assumed to be spatially localized integration can be carried out over a relatively small volume below the observation points and sparse matrix techniques can be applied we have applied the constrained inversion method to western washington using 4 387 shallow earthquakes to depths of 40 0 km 36 865 raypaths convering a 150 250 km region and found that the gravitational constraints may be satisfied with minor effect on the degree of misfit to the seismic data

crustal structure of the arabian plate new constraints from the analysis of teleseismic receiver functions an edited version of this paper was published by elsevier science copyright 2005 elsevier science see also http dx doi org 10 1016 j epsl 2004 12 020 http atlas geo cornell edu saudiarabia publications al damegh 202005 htm

cenozoic extension in coastal dhofar southern oman implications on the oblique rifting of the gulf of aden a detailed analysis of fault populations that affect the paleocene to early miocene sedimentary succession of southern dhofar allows the definition of a time sequence of paleostresses and the reconstruction of the rifting history of the eastern gulf of aden two distinct phases of n20j and n160j trending extensions took place during the deposition of the synrift dhofar group from late priabonian 35 ma to middle burdigalian 18 ma a period of tectonic instability preceded these events marked by normal and strike slip faulting as early as the mid eocene the two main directions of extension also recorded in southern yemen developed respectively oblique and normal to the n75e trend of the gulf of aden an anticlockwise succession of the two episodes from n20 to n160 only established in yemen accounts for the observed synrift fault pattern which is consistent with the type and geometry of faults predicted in analogue models of oblique rifting a latest phase of ns compression marked by strike slip faulting may represent a far echo of the arabia eurasia collision d 2002 elsevier science b v all rights reserved

interaction of mantle plumes and migrating mid ocean ridges implications for the galapagos plume ridge system we investigate the three dimensional interaction of mantle plumes and migrating mid ocean ridges with variable viscosity numerical models numerical models predict that along axis plume width w and maximum distance of plume ridge interaction xmax scale with q u where q is plume source volume flux and u is ridge full spreading rate both w and xmax increase with buoyancy number b which reflects the strength of gravitational versus plate driven spreading scaling laws derived for stationary ridges in steady state with near ridge plumes are consistent with those obtained from independent studies of ribe 1996 in the case of a migrating ridge the distance of plume ridge interaction is reduced when a ridge migrates toward the plume because of the excess drag of the faster moving leading plate and enhanced when a ridge migrates away from the plume because of the reduced drag of the slower moving trailing plate given the mildly buoyant and relatively viscous plumes investigated here the slope of the lithospheric boundary and thermal erosion of the lithosphere have little effect on plume flow from observed plume widths of the galapagos plume migrating ridge system our scaling laws yield estimates of galapagos plume volume flux of 5 16 106km3 m y 1 and a buoyancy flux of 2 103 kg s 1 model results suggest that the observed increase in bathymetric and mantle bouguer gravity anomalies along cocos plate isochrons with increasing isochron age is due to higher crustal production when the galapagos ridge axis was closer to the plume several million years ago the anomaly amplitudes can be explained by a plume source with a relatively mild temperature anomaly 50 100 c and moderate radius 100 200 km predictions of the along axis geochemical signature of the plume suggest that mixing between the plume and ambient mantle sources may not occur in the asthenosphere but instead may occur deeper in the mantle possibly by entrainment of depleted mantle as the plume ascends from its source

from rifting to spreading in the eastern gulf of aden a geophysical survey of a young oceanic basin from margin to margin a geophysical survey in the eastern gulf of aden between the alula fartak 52 e and the socotra 55 e transform faults was carried out during the encens sheba cruise the conjugate margins of the gulf are steep narrow and asymmetric asymmetry of the rifting process is highlighted by the conjugate margins horst and graben in the north and deep basin in the south two transfer fault zones separate the margins into three segments whereas the present day sheba ridge is divided into two segments by a transform discontinuity therefore segmentation of the sheba ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading extensive magma production is evidenced in the central part of the western segment anomaly 5d was identified in the northern and southern parts of the oceanic basin thus confirming that seafloor spreading in this part of gulf of aden started at least 17 6 ma ago

lithospheric structure of a nascent spreading ridge inferred from gravity data the western gulf of aden the aden spreading ridge somalia arabia plate boundary does not connect directly to the red sea spreading ridge it propagates toward the east african rift through the afar depression where the presence of a hot spot has been postulated from seismological and geochemical evidence the spreading direction n37 e is highly oblique to the overall trend n90 e of the ridge we present and interpret new geophysical data gathered during the tadjouraden cruise r v l atalante 1995 in the gulf of aden west of 46 e these data allow us to study the propagation of the ridge toward the afar and to discuss the processes of the seafloor spreading initiation we determine the lithospheric structure of the ridge using gravity data gathered during the cruise with the constraint of available refraction data a striking bouguer anomaly gradient together with the identification of magnetic anomalies defines the geographical extent of oceanic crust the inversion of the bouguer anomaly is performed in terms of variations of crustal thickness only and then discussed with respect to the expected thermal structure of the mantle lithosphere which should depend not only on the seafloor spreading but also on the hot spot beneath east africa our results allow us to define three distinct lithospheric domains in the western gulf of aden east of 44 45 e the lithosphere displays an oceanic character thermal subsidence recorded for the last 10 ma and constant crustal thickness between 43 30 e and 44 10 e the lithosphere is of continental type but locally thinned beneath the axial valley the central domain defined between 44 10 e and 44 45 e is characterized by a transitional lithosphere which can be seen as a stretched continental crust where thick blocks are mixed with thinned crust it displays en echelon basins that are better interpreted as extension cells rather than accretion cells

upper mantle structure beneath the arabian peninsula and northern red sea from teleseismic body wave tomography implications for the origin of cenozoic uplift and volcanism in the arabian shield upper mantle structure between 150 and 400 km depth is imaged beneath the arabian shield and northern red sea by modeling p and s traveltime residuals from teleseismic events recorded on the saudi arabia national digital seismic network the 1995 1997 saudi arabian passcal experiment and three permanent stations rayn eil and mrni relative traveltime residuals were obtained using a multichannel cross correlation method and inverted for upper mantle structure using vandecar s inversion method the resulting images reveal a low velocity region 1 5 for the p model and 3 for the s model trending nw se along the western side of the arabian shield and broadening to the northeast beneath the makkah madinah nafud volcanic line we attribute the low velocities to a mantle thermal anomaly that could be as large as 330 k and that is associated with the cenozoic uplift of and volcanic centers on the shield our tomographic images are not consistent with models invoking separate mantle upwellings beneath the northern and southern regions of the shield and instead favor single plume or superplume models we also find little evidence for low velocities beneath the northern red sea suggesting that there might not be a geodynamic link between rifting in the red sea and plateau uplift and volcanism in the shield

evidence of partial melting beneath a continental margin case of dhofar in the northeast gulf of aden sultanate of oman summary gravity data and p wave teleseismic traveltime residuals from 29 temporary broad band stations spread over the northern margin of the gulf of aden dhofar region oman were used to image lithospheric structure we apply a linear relationship between density and velocity to provide consistent density and velocity models from mid crust down to about 250 km depth the accuracy of the resulting models is investigated through a series of synthetic tests the analysis of our resulting models shows 1 crustal heterogeneities that match the main geological features at the surface 2 the gravity edge effect and disparity in anomaly depth locations for layers at 20 and 50 km 3 two low velocity anomalies along the continuation of socotra hadbeen and alula fartak fracture zones between 60 and 200 km depth and 4 evidence for partial melting 3 6 per cent within these two negative anomalies we discuss the presence of partial melting in terms of interaction between the sheba ridge melts and its along axis segmentation

propagation of rifting along the arabia somalia plate boundary the gulfs of aden and tadjoura the localization and propagation of rifting between arabia and somalia are investigated by assessing the deformation geometry and kinematics at different scales between the eastern gulf of aden and the gulf of tadjoura using bathymetric magnetic seismological and structural evidence large scale southwestward propagation of the aden ridge markedly oblique to the arabia somalia relative motion vector began about 30 myr ago between the error and sharbithat ridges it was an episodic process with stages of rapid propagation mostly at rates 10 cm yr interrupted by million year pauses on transverse discontinuities coinciding with rheological boundaries between different crustal provinces of the arabia somalia plate the longest pause was at the shukra el sheik discontinuity 45 e where the ridge tip stalled for 13 myr between 17 and 4 ma west of that discontinuity rifting and spreading took place at an azimuth n25 10 e and rate 1 2 0 3 cm yr different from those of the global arabia somalia motion vector n39 1 73 cm yr implying an additional component of movement n65 10 e 0 7 0 2 cm yr due to rotation of the danakil microplate at shukra el sheik the typical oceanic ridge gives way to a narrow wsw trending axial trough resembling a large fissure across a shallow shelf this trough is composed of about eight rift segments which result from normal faulting and fissuring along n110 n130 e trends all the segments step to the left southwestward mostly through oblique transfer zones with en echelon normal faults only two segments show clear significant overlap there is one clear transform the maskali fault between the obock and tadjoura segments the latter segment which encroaches onland is composed of two parallel subrifts iboli ambabbo that propagated northwestward and formed in succession the most recent southwestern subrift ambabbo represents the current tip of the aden ridge we propose a mechanical model in which the large scale propagation of the ridge followed a wsw trending zone of maximum tensile stress while the small scale propagation of its nw trending segments was dictated by the orientation of that stress oblique propagation was a consequence of passive lithospheric necking of the arabia somalia plate along its narrow section in map view between socotra and the kink of the red sea ethiopian rift above the afar plume individual ridge segments oriented roughly perpendicular to plate motion like lithospheric cracks were forced to jump southward because of confinement within the necking zone self sustaining plate scale necking may explain why the aden ridge did not connect with the red sea through bab el mandeb but continued straight into afar

pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the arabian eurasian and african plates an edited version of this paper was published by blackwell publishing in geophysical journal international copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02355 x http atlas geo cornell edu middleeastnorthafrica publications al lazki2004 htm

reappraisal of the arabia india somalia triple junction kinematics abstract we propose alternative kinematics for the arabia india somalia triple junction based on a re interpretation of seismological and magnetic data the new triple junction of the ridge ridge ridge type is located at the bend of the sheba ridge in the eastern gulf of aden at 14 5 n and 56 4 e the owen fracture zone arabia india boundary is connected to the sheba ridge by an ultra slow divergent boundary trending n80 e 10 marked by diffuse seismicity the location of the arabia india rotation pole is constrained at 14 1 n and 71 2 e by fitting the active part of the owen fracture zone with a small circle the finite kinematics of the triple junction is inferred from the present day kinematics since the inception of the accretion 15 18 ma ago the sheba ridge has probably receded 300 km at the expense of the carlsberg ridge which propagated northwestward in the gulf of aden while an ultra slow divergent plate boundary developed between the arabian and indian plates the overall geometry of the new triple junction is very similar to that of the azores triple junction

structure and evolution of the eastern gulf of aden conjugate margins from seismic reflection data the gulf of aden is a young and narrow oceanic basin formed in oligo miocene time between the rifted margins of the arabian and somalian plates its mean orientation n75 e strikes obliquely 50 to the n25 e opening direction the western conjugate margins are masked by oligo miocene lavas from the afar plume this paper concerns the eastern margins where the 19 35 ma breakup structures are well exposed onshore and within the sediment starved marine shelf those passive margins about 200 km distant are non volcanic offshore during the encens sheba cruise we gathered swath bathymetry single channel seismic reflection gravity and magnetism data in order to compare the structure of the two conjugate margins and to reconstruct the evolution of the thinned continental crust from rifting to the onset of oceanic spreading between the alula fartak and socotra major fracture zones two accommodation zones trending n25 e separate the margins into three n110 e trending segments the margins are asymmetric offshore the northern margin is narrower and steeper than the southern one including the onshore domain the southern rifted margin is about twice the breadth of the northern one we relate this asymmetry to inherited jurassic cretaceous rifts the rifting obliquity also influenced the syn rift structural pattern responsible for the normal faults trending from n70 e to n110 e the n110 e fault pattern could be explained by the decrease of the influence of rift obliquity towards the central rift and or by structural inheritance the transition between the thinned continental crust and the oceanic crust is characterized by a 40 km wide zone our data suggest that its basement is made up of thinned continental crust along the southern margin and of thinned continental crust or exhumed mantle more or less intruded by magmatic rocks along the northern margin abstract from author

post rift volcanism and high heat flow at the ocean continent transition of the eastern gulf of aden a high heat flow 900 mw m 2 has been observed over a volcanic structure at the ocean continent transition in the eastern gulf of aden oman margin the anomaly is superposed to a progressive increase of heat flow across the margin and can be interpreted either by 1 heat refraction 2 fluid discharge or 3 cooling magma the two first explanations cannot be ruled out definitely by modelling analysis but require unlikely thermal conductivity or permeability values the third one implies that the latest activity of the volcano was about 100 000 years old and therefore continued c 18 ma after the break up of africa and arabia this potential mechanism is consistent with other lines of evidence of post rifting activity in the gulf of aden and could invalidate the conventional assumption that rifted margins become passive after the break up of continents

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology 1 the question of plate boundary forces and deep versus shallow asthenospheric uplift has long been debated in intracontinental rift areas particularly in the baikal rift zone asia which is colder than other continental rifts as previous gravity and teleseismic studies support the dominance of opposing mechanisms in the baikal rift we reconsidered both data sets and jointly inverted them this more effective approach brings insight into location of the perturbing bodies related to the extension in this region our new joint inversion method allows for inverting the velocity density relationship with independent model parametrization we obtain velocity and density models that consistently show 1 crustal heterogeneities that coincide with the main tectonic features at the surface 2 a faster and denser cratonic mantle nw of lake baikal that we relate to the thermal contrast between old and depleted archean siberian platform and paleozoic orogenic belt sayan baikal belt 3 three dimensional topographic variations of the crust mantle boundary with well located upwarpings and 4 the lithosphere asthenosphere boundary uplift up to 70 km depth with a nw dip our resulting velocity and density models support the idea of a combined influence of lithospheric extension and inherited lithospheric heterogeneities for the origin of the baikal rift zone index terms 1234 geodesy and gravity regional and global gravity anomalies and earth structure 7218 seismology lithosphere and upper mantle 8122 citation tiberi c m diament j deverchere c petit mariani v mikhailov s tikhotsky and u achauer deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology