Roland Martin

Paul Sabatier University - Toulouse III | UPS Toulouse · Laboratoire Géosciences Environnement Toulouse - UM 97 (UMR 5563 / UMRD 234) - GET

We implement a spectral-element method for 3D time-independent elastoplastic problems in geomechanics. As a first application, we use the method for slope stability analyses ranging from small to large scales. The implementation employs an element-by-element preconditioned conjugate-gradient solver for efficient storage. The program accommodates ma...

In this paper we introduce an image reconstruction technique for imaging permittivity distributions using electrical capacitance tomography, based on global optimization by very fast simulated annealing. Electrical capacitance measurement data are obtained between electrodes placed around the outer wall of an electrically insulating pipe. Such data...

The perfectly matched layer PML absorbing boundary condition has proven to be very efficient from a numerical point of view for the elastic wave equation to absorb both body waves with nongrazing incidence and surface waves. However, at grazing incidence the classical discrete PML method suffers from large spurious reflections that make it less eff...

La Tomografía de Capacitancia Eléctrica (TCE) es una nueva tecnología capaz de lidiar con la complejidad de la medición de flujos bifásicos de gas-aceite, derivando la distribución de componentes en dos planos adyacentes a lo largo de un ducto. Una de sus aplicaciones más prometedoras es la visualización de flujos de gas y aceite. TCE ofrece alguna...

En este trabajo un algoritmo de tipo recocido simulado (SA) altamente optimizado es aplicado a la reconstrucción de imágenes de permitividades a partir de datos de flujos difásicos reales cruzando una sección de un tubo cilíndrico usando tomografía de capacitancia eléctrica (ECT). La ECT proporciona imágenes de baja precisión comparando con otros p...

Plain Language Summary After a quake, the surface of our planet vibrates like the surface of a drum. These vibrations generate sound waves at low frequencies that propagate upward in the atmosphere. These signals from two earthquakes have been recorded by barometers on board a network of long duration high altitude balloons deployed by the Strateol...

It is of particular importance for structural geology, geophysical exploration and also obvious economical purposes to retrieve structures possibly hidden below salt domes. And these domes could trap hydrocarbon or gas. We thus propose a sensitivity analysis of seismic data in salt tectonic areas to identify different wavelengths associated with th...

This contribution reviews the challenges of imaging collisional orogens, focusing on the example of the Pyrenean domain. Indeed, important progresses have been accomplished regarding our understanding of the architecture of this mountain range over the last decades, thanks to the development of innovative passive imaging techniques, relying on a mo...

We investigate numerically some thermo-mechanical conditions for the development of crustal scale diapirism and convection in a heterogeneous continental crust independently from the action of regional tectonics. Here, we consider a hot crust where convection is generated below a melting front, with unmolten and partially molten domains of specific...

We introduce SPECFEM2D-DG, an open-source, time-domain, hybrid Galerkin software modelling the propagation of seismic and acoustic waves in coupled solid–fluid systems. For the solid part, the visco-elastic system from the routinely used SPECFEM2D software is used to simulate linear seismic waves subject to attenuation. For the fluid part, SPECFEM2...

The quantitative integration of geophysical measurements with data and information from other disciplines is becoming increasingly important in answering the challenges of undercover imaging and of the modelling of complex areas. We propose a review of the different techniques for the utilisation of structural, petrophysical, and geological informa...

We introduce SPECFEM2D-DG, an open-source, time-domain, hybrid Galerkin software modeling the propagation of seismic and acoustic waves in coupled solid-fluid systems. For the solid part, the visco-elastic system from the routinely used SPECFEM2D software is used to simulate linear seismic waves subject to attenuation. For the fluid part, SPECFEM2D...

The quantitative integration of geophysical measurements with data and information from other disciplines is becoming increasingly important in answering the challenges of undercover imaging and of the modelling of complex areas. We propose a review of the different techniques for the utilisation of structural, petrophysical and geological informat...

To reduce uncertainties in reconstructed images, geological information must be introduced in a numerically robust and stable way during the geophysical data inversion procedure. In the context of potential (gravity) data inversion, it is important to bound the physical properties by providing probabilistic information on the number of lithologies...

Large impact structures are characterized by peak ring and central uplifts with lateral/vertical mass transport during late formation stages. Here we investigate the Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Seismic reflection surveys in its central sector have shown lack of resoluti...

Energy transmissions from atmospheric pressure perturbations to ground motion take various forms, ranging from wave transmission to compliance effects. These phenomena are of utmost importance when studying airwaves in planetary atmospheres, and concerns particularly infrasound and gravity waves. In November of 2018, the InSight mission deployed on...

The measurements of acoustic waves created by a quake are of great interest for planets with hot and dense atmospheres, like Venus, because surface deployments of seismometers will last only a few hours whereas free flying balloons could fly many days. Infrasound sensors can also be used to constrain sub-surface properties during active seismic exp...

We explore here the benefits of using constraints from seismic tomography in gravity data inversion and how inverted density distributions can be improved by doing so. The methodology is applied to a real field case in which we reconstruct the density structure of the Pyrenees along a southwest-northeast transect going from the Ebro basin in Spain...

Acoustic waves in planetary atmospheres couple into the solid surface, producing ground displacements that can be measured using seismometers. On November 26 2018, the InSight mission successfully landed on Mars. Its objectives include studying Mars' interior using the seismometer SEIS (Seismic Experiment for Interior Structures) and the atmosphere...

Gravitational instabilities exert a crucial role on the Earth dynamics and in particular on its differentiation. The Earth’s crust can be considered as a multilayered fluid with different densities and viscosities, which may become unstable in particular with variations in temperature. With the specific aim to quantify crustal scale polydiapiric in...

3D thermo-mechanical models have been constructed to explore the influence of pre-existing faults on the temporal-spatial distribution of high-grade amphibolite-granulite facies metamorphic rocks during extension. The different dip amounts of three pre-existing faults (refer to the Bole-Nangodi shear zones, the Jirapa shear zone and the Bulenga she...

The integration of petrophysical data and probabilistic geological modelling in geophysical joint inversion is a powerful tool to solve exploration challenges. Models obtained from geologically and/or petrophysically constrained inversions are the result of complex interactions between correspondingly diverse data sets. Therefore, it is important t...

GOCE-derived gravity anomalies are analyzed over the western Mediterranean in order to evaluate the information brings by these satellite observations on the complex lithospheric structure of this region. Free-air and Bouguer anomalies deduced from the latest GOCE model are analyzed and compared with the theoretical response computed from the CRUST...

We introduce a workflow integrating geological modelling uncertainty information to constrain gravity inversions. We test and apply this approach to the Yerrida Basin (Western Australia), where we focus on prospective greenstone belts beneath sedimentary cover. Geological uncertainty information is extracted from the results of a probabilistic geol...

In previous studies, the auxiliary differential equation (ADE) method has been applied to 2-D seismic-wave propagation modelling in viscoelastic media. This method is based on the separation of the wave propagation equations derived from the constitutive law defining the stress-strain relation. We make here a 3-D extension of a finite-difference (F...

The integration of geological modelling, petrophysics and geophysics in a single inversion scheme is a complex and powerful strategy for solving challenges faced in geoscientific resource exploration. Probabilistic geological modelling and geophysical inversion are non-linear processes that show various degrees of sensitivity to uncertainty in inpu...

High-grade (amphibolite–granulite facies) tectono-metamorphic domains in the Sefwi terrane of Ghana are separated from adjacent lower-grade (greenschist facies) greenstone belts by two main shear zones. The high-grade rocks presumably exhumed along the sinistral shear zones during the D2 ENE-WSW transtension (~2073 Ma). To better understand the rol...

The mechanical coupling between solid planets and their atmospheres enables seismically‐induced acoustic waves to propagate in the atmosphere. We numerically simulate this coupled system for two application cases: Active Seismic Experiments (ASE) and Passive Seismic Experiments (PSEs). A recent ASE [Krishnamoorthy et al., 2018] observed the infraso...

In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP³), the InSight lander holds a highly sensitive pressure sensor (PS...

We introduce a workflow integrating geological uncertainty information in order to constrain gravity inversions. We test and apply this approach to data from the Yerrida Basin (Western Australia), where we focus on prospective greenstone belts beneath sedimentary cover. Geological uncertainty information is extracted from the results of a probabili...

We present a new model of the lithosphere and asthenosphere structure down to 300 km depth beneath the Pyrenees from the joint inversion of recent gravity and teleseismic data. Unlike previous studies, crustal correction was not applied on teleseismic data in order (i) to preserve the consistency between gravity data, which are mainly sensitive to...

We exploit the data from five seismic transects deployed across the Pyrenees to characterize the deep architecture of this collisional orogen. We map the main seismic interfaces beneath each transect by depth migration of P-to-S converted phases. The migrated sections, combined with the results of recent tomographic studies and with maps of Bouguer...

The qualitative integration of geological and geophysical data is a useful approach to constrain inversion that aims to improve interpretation and to reduce the geophysical data misfit. Here, we introduce an inversion approach that incorporates probabilistic geological information into geophysical inversion in the absence of the data necessary to d...

In order to improve image reconstructions, different classes of nonlinear inversion algorithms are developed and used in different research topics like imaging processes in oil industry or the characterization of complex porous media or multiphase flows. These algorithms are able to avoid local minima and to reach more adapted minima of a given mis...

The presented work consists in 1) the full-wave modelling of waves in a coupled solid-atmosphere medium, and in 2) the analysis of planetary applications. A software modelling the coupled system between full Navier-Stokes (or compressible Euler) and elastodynamic equations is used as a starting point. The numerical techniques as well as the latest...

A dense seismic network of about 450 three-component (3C) sensors recording continuously for 6 months, from March to October 2017, was deployed in the Mauleon basin which is located in the northern foothills of the western Pyrenees. Three different types of sensors were used: 191 SG-10 3C SERCEL nodes, 197 3C 5 Hz Seismotech short period stations,...

Greenstone belts in the West African Craton (WAC) are separated by several generations of granitoids intruded at ca. 2.18–1.98 Ga. Simultaneous folding and exhumation play an important role in the formation of greenstone-granitoid belts. However, the overall tectonic regime and origin of granitoids remain controversial. In this study, we present th...

High-grade tectono-metamorphic domains in the Sefwi terrane of Ghana are separated from adjacent low-grade greenstone belts by two main shear zones. The high-grade rocks are thought to have been exhumed along sinistral shear zones during the D2 ENE-WSW transtension. To better understand the role boundary conditions and the spatial relationship of f...

The propagation of acoustic and gravity waves in planetary atmospheres is strongly dependent on both wind conditions and attenuation properties. This study presents a finite-difference modeling tool tailored for acoustic-gravity wave applications that takes into account the effect of background winds, attenuation phenomena (including relaxation eff...

We have developed a joint geophysical inversion workflow that aims to improve subsurface imaging and decrease uncertainty by integrating petrophysical constraints and geologic data. In this framework, probabilistic geologic modeling is used as a source of information to condition the petrophysical constraints spatially and to derive starting models...

SPECFEM3D_GEOTECH is an open-source command-driven software for 3D slope stability analysis and simulation of 3D multistage excavation based on the spectral-element method.

We introduce a hybrid Galerkin modeling tool for the non-linear acoustic and gravity waves propagation in planetary atmospheres coupled through topography to a solid medium. We rely on a 2D spectral-element technique to model linear visco-elastic solid media and couple it to a discontinuous Galerkin method for the atmosphere modeled by the fully no...

We image the internal density structure of the Pyrenees by inverting gravity data using an a priori density model derived by scaling a Vp model obtained by full waveform inversion of teleseismic P-waves. Gravity anomalies are computed via a 3-D high-order finite-element integration in the same high-order spectral-element grid as the one used to sol...

We present a hybrid inversion method that allows us to image density distributions at the regional scale using both seismic and gravity data. One main goal is to obtain densities and seismic wave velocities (P and S) in the lithosphere with a fine resolution to get important constraints on the mineralogic composition and thermal state of the lithos...

We present a hybrid inversion method that allows us to image density distributions at the regional scale using both seismic and gravity data. One main goal is to obtain densities and seismic wave velocities (P and S) in the lithosphere with a fine resolution to get important constraints on the mineralogic composition and thermal state of the lithos...

We introduce and test a workflow that integrates petrophysical constraints and geological data in joint geophysical inversion in order to decrease the uncertainty of the results. This workflow uses statistical petrophysical properties to constrain the values retrieved by the geophysical inversion and geological prior information to decrease the eff...

We introduce and test a workflow that integrates petrophysical constraints and geological data in geophysical inversion in order to decrease the effect of non-uniqueness and to improve imaging. This workflow uses petrophysical measurements to constrain the values retrieved by geophysical inversion. Geological modelling is used to define petrophysic...

A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range-dependent and depth-dependent wave speed and density, as well as...

Core Ideas We tested the sensitivity of seismic measurements to water saturation variations. We used ultrasonic techniques to reproduce a small‐scale seismic acquisition setup. Measurements were performed on glass bead layers with varying water levels. Results of 3D numerical modelling were used to validate data at the dry state. Data difference tr...

Imaging the architecture of mountain roots is required to understand the support of topography and for kinematic reconstructions at convergent plate boundaries, but is still challenging with conventional seismic imaging approaches. Here we present a three-dimensional model of both compressional and shear velocities in the lithosphere beneath the we...

We propose a set of local operators to deal with internal discontinuities that do not coincide with collocated Cartesian grids in 2D transversely isotropic media. We use globally optimally accurate operators in order to obtain high accuracy. We derive modified operators by extrapolating wavefields from nearby grid points to the discontinuous point,...

Acoustic and gravity waves propagating in planetary atmospheres have been studied intensively as markers of specific phenomena such as tectonic events or explosions or as contributors to atmosphere dynamics. To get a better understanding of the physics behind these dynamic processes, both acoustic and gravity waves propagation should be modelled in...

Existing 3D geological systems are well adapted to high data-density environments, such as at the mine scale where abundant drill core exists, or in basins where 3D seismic provides stratigraphic constraints, but are poorly adapted to regional geological problems. There are three areas where improvements in the 3D workflow need to be made: in the h...