Bayesian Gaussian Mixture Linear Inversion for Geophysical Inverse Problems     

Dario Grana  Torstein Fjeldstad  Henning Omre 《Mathematical Geosciences》2017,49(4):493-515

A Bayesian linear inversion methodology based on Gaussian mixture models and its application to geophysical inverse problems are presented in this paper. The proposed inverse method is based on a Bayesian approach under the assumptions of a Gaussian mixture random field for the prior model and a Gaussian linear likelihood function. The model for the latent discrete variable is defined to be a stationary first-order Markov chain. In this approach, a recursive exact solution to an approximation of the posterior distribution of the inverse problem is proposed. A Markov chain Monte Carlo algorithm can be used to efficiently simulate realizations from the correct posterior model. Two inversion studies based on real well log data are presented, and the main results are the posterior distributions of the reservoir properties of interest, the corresponding predictions and prediction intervals, and a set of conditional realizations. The first application is a seismic inversion study for the prediction of lithological facies, P- and S-impedance, where an improvement of 30% in the root-mean-square error of the predictions compared to the traditional Gaussian inversion is obtained. The second application is a rock physics inversion study for the prediction of lithological facies, porosity, and clay volume, where predictions slightly improve compared to the Gaussian inversion approach.  相似文献   

Seismic source characterization of the Alpine foreland in the context of a probabilistic seismic hazard analysis by PEGASOS Expert Group 1 (EG1a)   总被引：1，自引：0，他引：1  

Stefan M. Schmid  Dario Slejko 《Swiss Journal of Geoscience》2009,102(1):121-148

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Guidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project     

Sebastiano Foti  Fabrice Hollender  Flora Garofalo  Dario Albarello  Michael Asten  Pierre-Yves Bard  Cesare Comina  Cécile Cornou  Brady Cox  Giuseppe Di Giulio  Thomas Forbriger  Koichi Hayashi  Enrico Lunedei  Antony Martin  Diego Mercerat  Matthias Ohrnberger  Valerio Poggi  Florence Renalier  Deborah Sicilia  Valentina Socco 《Bulletin of Earthquake Engineering》2018,16(6):2367-2420

Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V_S,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.  相似文献   

Optimal design and seismic performance of tuned mass damper inerter (TMDI) for structures with nonlinear base isolation systems          下载免费PDF全文

Dario De Domenico  Giuseppe Ricciardi 《地震工程与结构动力学》2018,47(12):2539-2560

The tuned mass damper inerter (TMDI) couples the classical tuned mass damper (TMD) with an inerter, a mechanical device whose generated force is proportional to the relative acceleration between its terminals, thus providing beneficial mass‐amplification effects. This paper deals with a dynamic layout in which the TMDI is installed below the isolation floor of base‐isolated structures in order to enhance the earthquake resilience and reduce the displacement demand. Unlike most of the literature studies that assumed a linearized behavior of the isolators, the aim of this paper is to investigate the effectiveness of the TMDI while accounting for the nonlinearity of the isolators. Two nonlinear constitutive behaviors are considered, a Coulomb friction model and a Bouc‐Wen hysteretic model, representative of friction pendulum and of lead‐rubber‐bearing isolators, respectively. Optimal design is based on the stochastic dynamic analysis of the system, by modeling the base acceleration as a Kanai‐Tajimi filtered stationary random process and resorting to the stochastic linearization technique to handle the nonlinear terms. Different tuning criteria based on displacement, acceleration, and energy‐based performance indices are defined, and their implications in a design process are discussed. It is proven that the improved robustness of the TMDI reduces its performance sensitivity to the tuning frequency and to the earthquake frequency content, which are well‐known shortcomings of TMD‐like systems. This important feature makes the TMDI particularly suitable for nonlinear base‐isolated structures that are affected by unavoidable uncertainties in the isolators' properties and that may experience changes of isolators effective stiffness depending on the excitation level.  相似文献   

Rock physics modelling and inversion for saturation-pressure changes in time-lapse seismic studies     

Xiaozheng Lang  Dario Grana 《Geophysical Prospecting》2019,67(7):1912-1928

Time-lapse seismic data are generally used to monitor the changes in dynamic reservoir properties such as fluid saturation and pore or effective pressure. Changes in saturation and pressure due to hydrocarbon production usually cause changes in the seismic velocities and as a consequence changes in seismic amplitudes and travel times. This work proposes a new rock physics model to describe the relation between saturation-pressure changes and seismic changes and a probabilistic workflow to quantify the changes in saturation and pressure from time-lapse seismic changes. In the first part of this work, we propose a new quadratic approximation of the rock physics model. The novelty of the proposed formulation is that the coefficients of the model parameters (i.e. the saturation-pressure changes) are functions of the porosity, initial saturation and initial pressure. The improvements in the results of the forward model are shown through some illustrative examples. In the second part of the work, we present a Bayesian inversion approach for saturation-pressure 4D inversion in which we adopt the new formulation of the rock physics approximation. The inversion results are validated using synthetic pseudo-logs and a 3D reservoir model for CO₂ sequestration.  相似文献   

Oxygen in the Earth's core: a first-principles study     

Dario Alf  G. David Price  Michael J. Gillan 《Physics of the Earth and Planetary Interiors》1999,110(3-4):191-210

First-principles electronic structure calculations based on DFT have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to account for the inferred density in the outer core, to probe the stability of the liquid against phase separation, to interpret the bonding in the liquid, and to find out whether the viscosity differs significantly from that of pure liquid iron at the same conditions. It is shown that the required concentration of oxygen is in the region 25–30 mol%, and evidence is presented for phase stability at these conditions. The Fe/O bonding is partly ionic, but with a strong covalent component. The viscosity is lower than that of pure liquid iron at Earth's core conditions. It is shown that earlier first-principles calculations indicating very large enthalpies of formation of solid solutions may need reinterpretation, since the assumed crystal structures are not the most stable at the oxygen concentration of interest.  相似文献   

Stormwater plume detection by MODIS imagery in the southern California coastal ocean     

Nikolay P. Nezlin  Paul M. DiGiacomo  Dario W. Diehl  Burton H. Jones  Scott C. Johnson  Michael J. Mengel  Kristen M. Reifel  Jonathan A. Warrick  Menghua Wang 《Estuarine, Coastal and Shelf Science》2008

Stormwater plumes in the southern California coastal ocean were detected by MODIS-Aqua satellite imagery and compared to ship-based data on surface salinity and fecal indicator bacterial (FIB) counts collected during the Bight'03 Regional Water Quality Program surveys in February–March of 2004 and 2005. MODIS imagery was processed using a combined near-infrared/shortwave-infrared (NIR-SWIR) atmospheric correction method, which substantially improved normalized water-leaving radiation (nLw) optical spectra in coastal waters with high turbidity. Plumes were detected using a minimum-distance supervised classification method based on nLw spectra averaged within the training areas, defined as circular zones of 1.5–5.0-km radii around field stations with a surface salinity of S < 32.0 (“plume”) and S > 33.0 (“ocean”). The plume optical signatures (i.e., the nLw differences between “plume” and “ocean”) were most evident during the first 2 days after the rainstorms. To assess the accuracy of plume detection, stations were classified into “plume” and “ocean” using two criteria: (1) “plume” included the stations with salinity below a certain threshold estimated from the maximum accuracy of plume detection; and (2) FIB counts in “plume” exceeded the California State Water Board standards. The salinity threshold between “plume” and “ocean” was estimated as 32.2. The total accuracy of plume detection in terms of surface salinity was not high (68% on average), seemingly because of imperfect correlation between plume salinity and ocean color. The accuracy of plume detection in terms of FIB exceedances was even lower (64% on average), resulting from low correlation between ocean color and bacterial contamination. Nevertheless, satellite imagery was shown to be a useful tool for the estimation of the extent of potentially polluted plumes, which was hardly achievable by direct sampling methods (in particular, because the grids of ship-based stations covered only small parts of the plumes detected via synoptic MODIS imagery). In most southern California coastal areas, the zones of bacterial contamination were much smaller than the areas of turbid plumes; an exception was the plume of the Tijuana River, where the zone of bacterial contamination was comparable with the zone of plume detected by ocean color.  相似文献   

Characterisation and modelling of marine dissolved organic matter interactions with major and trace cations     

Yoann Louis  Cédric Garnier  Véronique Lenoble  Dario Omanović  Stéphane Mounier  Ivanka Pižeta 《Marine environmental research》2009,67(2):100-107

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3D geoelectric tomography and archaeological applications1     

Paolo Mauriello  Dario Monna  Domenico Patella 《Geophysical Prospecting》1998,46(5):543-570

Following a previous paper in which the principles of a 3D ground-surface tomographic processing of self-potential data were established, we extend the method to active source geoelectric surveying. The main purpose of the new tomographic approach is to obtain a physical image reconstruction of the induced electric charges distributed over buried resistivity discontinuities. The information is produced in a probabilistic sense, as the mathematical formulation underlying the method treats only the intrinsic physical nature of the generated electric field underground and the method of its ground-surface detection, independently of the geometry of the unknown structures. In practice, a 3D tomography is realized by cross-correlating a set of distributed electric-field ground-surface data with a scanning function, representing a unit positive point charge located anywhere in the lower half-space. The resolution of the method is tested on the synthetic response of a 3D structural simulation of an archaeological target, consisting of an infinitely resistive prismatic body immersed in a half-space, including surface inhomogeneities and layering. Finally, the field response of a 3D structure consisting of a hypogeal dromos-chamber tomb inside the Sabine Necropolis at Colle del Forno, close to Rome, is presented and discussed.  相似文献   

ISO-LWS Observations of the NGC7129 Star Forming Region     

Elisabetta Tommasi  Dario Lorenzetti  Teresa Giannini  Brunella Nisini  Francesco Palla 《Astrophysics and Space Science》1998,261(1-4):187-190

We present far-infrared observations of the surroundings of the Herbig Be star LkHα234 in NGC7129, obtained with the Long Wavelength Spectrometer on board of the Infrared Space Observatory. [CII]158μm, [OI]63μm and [OI]146μm lines are detected everywhere in the mapped region and their intensity ratios are consistent with the model predictions of a photodissociation region. The spatial distribution of the emission features indicates the presence of a peak which does not coincide with the position of LkHα234, but is more likely associated with another nearby Herbig star, namely BD+65°1637; the far-ultraviolet field intensity and the density derived from our observations are fully consistent with this hypothesis. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献