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The estimation of crustal structure and thickness is essential in understanding the formation and evolution of terrestrial planets. Initial planetary missions with seismic instrumentation on board face the additional challenge of dealing with seismic activity levels that are only poorly constrained a priori. For example, the lack of plate tectonics on Mars leads to low seismicity, which could, in turn, hinder the application of many terrestrial data analysis techniques. Here we propose using a joint inversion of receiver functions and apparent incidence angles, which contain information on absolute S-wave velocities of the subsurface. Since receiver function inversions suffer from a velocity depth trade-off, we in addition exploit a simple relation that defines apparent S-wave velocity as a function of observed apparent P-wave incidence angles to constrain the parameter space. We then use the Neighborhood Algorithm for the inversion of a suitable joint objective function. The resulting ensemble of models is then used to derive uncertainty estimates for each model parameter. In preparation for the analysis of data from the InSight mission, we show the application of our proposed method on Mars synthetics and sparse terrestrial data sets from different geological settings using both single and multiple events. We use information-theoretic statistical tests as model selection criteria and discuss their relevance and implications in a seismological framework.

The estimation of crustal structure and thickness is essential in understanding the formation and evolution of terrestrial planets. Initial planetary missions with seismic instrumentation on board face the additional challenge of dealing with seismic activity levels that are only poorly constrained a priori. For example, the lack of plate tectonics on Mars leads to low seismicity, which could, in turn, hinder the application of many terrestrial data analysis techniques. Here we propose using a joint inversion of receiver functions and apparent incidence angles, which contain information on absolute S-wave velocities of the subsurface. Since receiver function inversions suffer from a velocity depth trade-off, we in addition exploit a simple relation that defines apparent S-wave velocity as a function of observed apparent P-wave incidence angles to constrain the parameter space. We then use the Neighborhood Algorithm for the inversion of a suitable joint objective function. The resulting ensemble of models is then used to derive uncertainty estimates for each model parameter. In preparation for the analysis of data from the InSight mission, we show the application of our proposed method on Mars synthetics and sparse terrestrial data sets from different geological settings using both single and multiple events. We use information-theoretic statistical tests as model selection criteria and discuss their relevance and implications in a seismological framework.

The assembly of East Asia was closely linked to the closure of the Tethyan oceans. In south-east China, the closure of the Paleo-Tethys ocean led to a continental collision between the South China and North China blocks (SCB and NCB), forming the world renowned (ultra-) high pressure (UHP) metamorphic belt of the Dabie-Sulu Orogen. The region was subsequently reworked by postorogenic extensional processes. These tectonic processes likely have left lithospheric scars identifiable by seismic imaging techniques. Here we characterize seismic structures across the orogen and analyze processes related to the closure of the Paleo-Tethys. Using cutting-edge tomographic approaches and ambient noise dispersion data, we developed a fine-scale crustal shear-wave velocity model beneath key crustal domains in the region. Distinct crustal scale velocity domains are identified, corresponding to the normal Precambrian crust, slow-velocity suture zones and fault systems, and fast-velocity orogens, suggesting a deep root of the corresponding surface geological features. By combining recent models of active-source, gravity and magnetotellurics, characteristic lithospheric deformation patterns such as crustal thrust systems and lithospheric wedges can be inferred, which are attributed to a northward subduction of the SCB lithosphere and the eventual continental collision after the closure of the Paleo-Tethys Ocean.

The first attempts to quantify the width and height of hotspot swells were made more than 30. years ago. Since that time, topography, ocean-floor age, and sediment thickness datasets have improved considerably. Swell heights and widths have been used to estimate the heat flow from the core-mantle boundary, constrain numerical models of plumes, and as an indicator of the origin of hotspots. In this paper, we repeat the analysis of swell geometry and buoyancy flux for 54. hotspots, including the 37 considered by Sleep (1990) and the 49 considered by Courtillot et al. (2003), using the latest and most accurate data. We are able to calculate swell geometry for a number of hotspots that Sleep was only able to estimate by comparison with other swells. We find that in spite of the increased resolution in global bathymetry models there is significant uncertainty in our calculation of buoyancy fluxes due to differences in our measurement of the swells' width and height, the integration method (volume integration or cross-sectional area), and the variations of the plate velocities between HS2-Nuvel1a (Gripp and Gordon, 1990) and HS3-Nuvel1a (Gripp and Gordon, 2002). We also note that the buoyancy flux for Pacific hotspots is in general larger than for Eurasian, North American, African and Antarctic hotspots. Considering that buoyancy flux is linearly related to plate velocity, we speculate that either the calculation of buoyancy flux using plate velocity over-estimates the actual vertical flow of material from the deep mantle or that convection in the Pacific hemisphere is more vigorous than the Atlantic hemisphere. © 2014 Elsevier B.V.