Article
Geochemistry & Geophysics
Weichen Zhan, Mingwei Zhuang, Qi Qiang Liu, Linlin Shi, Yuefeng Sun, Qing Huo Liu
Summary: It is known that the spectral element method (SEM) is more effective than traditional finite element methods (FEM) for complex geophysical problems. Developing a frequency domain SEM can improve efficiency for narrowband simulations and solve multiphysics coupling problems through different interface types coupling conditions.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
R. Hawkins, M. H. Khalid, K. Smetana, J. Trampert
Summary: The computational cost of full waveform simulation in seismological contexts is high and requires large clusters of computers. We focus on model order reduction (MOR) method, which projects the full waveform system onto a lower dimensional space to reduce computational and memory requirements, at the cost of approximation errors. Inspired by normal mode (NM) theory, we use seismic wave equation eigenmodes for MOR. We demonstrate the application of free body oscillations and Petrov-Galerkin projection in regional scale problems using advanced eigensolvers for MOR, and its potential in future time-critical applications like seismic hazard monitoring.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Enjiang Wang, Lin Zhang, Jose M. Carcione, Jing Ba
Summary: Based on the generalized Biot-Rayleigh model, this study investigates the amplitude and energy reflection coefficients of seismic waves in porous media with penny-shaped inclusions, taking into account the attenuation due to mesoscopic local fluid flow. The results show that the local fluid flow mechanism mainly reduces the reflection coefficients at the gas-water contact and water-porous medium interface. The crack density and aspect ratio also affect the mesoscopic attenuation and relaxation frequency, thereby influencing the reflection coefficients.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Stuart Russell, John F. Rudge, Jessica C. E. Irving, Sanne Cottaar
Summary: The Earth's ellipticity affects the travel times of seismic waves, and current tables of ellipticity coefficients are outdated. We have developed EllipticiPy, a Python package that calculates ellipticity corrections and eliminates the need for pre-calculated coefficient tables. It can also be used for ellipticity corrections on other planets.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geosciences, Multidisciplinary
Ziduo Hu, Jidong Yang, Linghe Han, Jianping Huang, Shanyuan Qin, Jiaxing Sun, Youcai Yu
Summary: The Quaternary loess on the Loess Plateau of China causes strong seismic attenuation, resulting in weak reflections from subsurface exploration targets. To accurately simulate seismic wavefield in this area, a 2D/3D wavefield simulation method using a viscoacoustic wave equation with explicitly expressed quality factor is proposed. Grid deformation is introduced to consider the effect of irregular surface, and a finite-difference scheme based on a fully staggered-grid is adopted to solve the viscoacoustic wave equation. The feasibility and adaptability of the proposed method are demonstrated through numerical experiments and the modeling results show a good performance.
FRONTIERS IN EARTH SCIENCE
(2023)
Article
Geochemistry & Geophysics
Fansheng Xiong, Wen-An Yong
Summary: This work presents a machine-learning-based framework for determining unknown coefficients in seismic wave equations using real data. The trained neural networks incorporate mathematical and physical constraints on the coefficients, resulting in accurate predictions of synthetic and real data.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Armando Espindola-Carmona, Ridvan Oersvuran, P. Martin Mai, Ebru Bozdag, Daniel B. Peter
Summary: Improving the resolution of seismic anelastic models is crucial for understanding the Earth's subsurface structure and dynamics. Seismic attenuation plays a vital role in estimating water content, partial melting, and temperature variations in the Earth's crust and mantle. However, seismic attenuation tomography models tend to have lower resolution compared to seismic wave-speed models.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yder Masson
Summary: This study presents a distributional finite-difference method (DFDM) for simulating the propagation of elastic waves in heterogeneous media in the time domain. DFDM decomposes the modeling domain into multiple elements of arbitrary sizes. When large elements are used, the method is computationally efficient and resembles the finite-difference method. When smaller elements are used, DFDM is more similar to the finite-element or spectral element methods and allows for meshing complicated structures. The proposed algorithm accurately models elastic wave propagation in heterogeneous media and accommodates non-conformal meshes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yann Capdeville
Summary: This work introduces a new method to replace Dirac point sources in seismic wave equations with a smooth source term using the non-periodic two-scale homogenization method, leading to accurate results in both far-source and near-source wavefields. The method has potential significance in solving forward and inverse seismic problems.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Yongming Lu, Wei Zhang
Summary: Traveltime computations are crucial in seismic data processing applications, and a fast and efficient method is developed in this study to solve the issues in anisotropic media. By transforming the quartic slowness equation into a quadratic one, the computational efficiency is greatly improved, making it suitable for calculating first-arrival traveltimes in 3-D VTI media.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Shoji Sekiguchi
Summary: Limiting the number of valid nodes around a reference ray can greatly reduce the calculation time of the shortest-path method. The modified calculation method shows small average traveltime and ray path differences in velocity models. Improved travel time and ray path results can be achieved through iterative calculations and utilizing more neighbor nodes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Jie Dong, Pengfei Cheng, Hanjiang Wen, Wenke Sun
Summary: This study presents a new analytical approach to compute internal co-seismic displacement and strain changes caused by different types of seismic sources, revealing internal deformations are larger than surface deformations. Patterns of deformations near the source are consistent with formulas, and patterns of internal deformations at radial section plane appear symmetrical.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geosciences, Multidisciplinary
T. S. Hudson, J. M. Kendall, J. D. Blundy, M. E. Pritchard, P. MacQueen, S. S. Wei, J. H. Gottsmann, S. Lapins
Summary: Mapping fluid distribution in the crust below Uturuncu volcano using seismic attenuation tomography reveals partially and fully fluid-saturated areas along aligned faults and fractures. Pressure-temperature profiles and conductivity data help identify the likely fluid composition, with shallow regions of dry and H2O/brine-saturated crust, and a deeper supercritical H2O/brine column. These observations provide insights into Uturuncu's transcrustal hydrothermal system and demonstrate the potential application of such methods for mapping crustal fluid pathways and hydrothermal/geothermal systems.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geochemistry & Geophysics
Jose M. Carcione, Davide Gei, Stefano Picotti, Marco A. B. Botelho
Summary: This article analyzes the concepts of instantaneous frequency and quality factor, and their applications and universality in signal spectra. By examining the characteristics of signals in different scenarios, we can better understand the relationship between frequency shifts and signal quality.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Gareth S. O'Brien
Summary: Nonlinear wave propagation is studied in geophysical problems using a numerical method that considers the relationship between local interaction constants and macroscopic nonlinear coefficients, reproducing common features of nonlinear wave propagation. The method is validated through theoretical dispersion properties and numerical results, showing complexity in dynamic and static deformation with the inclusion of nonlinearity.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Luong Duy Thanh, Damien Jougnot, Santiago G. Solazzi, Nguyen Van Nghia, Phan Van Do
Summary: This paper proposes a physically based model for the dynamic streaming potential coupling coefficient (SPCC) by conceptualizing a porous medium as a bundle of tortuous capillaries with different pore size distributions. The dynamic SPCC is found to be a complex function depending on the properties of pore fluid, mineral-pore fluid interfaces, microstructural parameters of porous media and frequency. The proposed model is compared with published data and previous models, and the results show good agreement.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Yu Liu, James Irving, Klaus Holliger
Summary: The proposed approach combines diffraction analysis and inversion of the reflected wavefield to estimate the detailed subsurface velocity structure from common-offset GPR reflection measurements. Testing and validation on synthetic data sets and a field example demonstrate the viability and robustness of the method. Additionally, the efficiency of the method in terms of field effort and computational cost allows for easy extension to 3-D, making it more attractive compared to multi-offset-based GPR velocity estimation techniques.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Gabriel E. Quiroga, J. German Rubino, Santiago G. Solazzi, Nicolas D. Barbosa, Klaus Holliger
Summary: Passive seismic characterization is an environmentally friendly method used to estimate the seismic properties of the subsurface. This study investigates the effects of fracture connectivity on Rayleigh wave velocity dispersion and incorporates wave-induced fluid pressure diffusion effects. The results show that fracture connectivity significantly affects the Rayleigh wave velocity.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geochemistry & Geophysics
J. German Rubino, Nicolas D. Barbosa, Jurg Hunziker, Klaus Holliger
Summary: This study demonstrates for the first time that seismic reflection coefficients are highly sensitive to fracture interconnectivity, and suggests the use of crossplots of AVA coefficients to delineate fractured formations with different levels of fracture interconnectivity.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Gabriel E. Quiroga, J. German Rubino, Santiago G. Solazzi, Nicolas D. Barbosa, Marco Favino, Klaus Holliger
Summary: The presence of gaseous formation fluids in geothermal reservoirs and their effects on seismic velocities are important for geothermal energy production. This study proposes a poroelastic upscaling approach to accurately describe the physical processes in fractured reservoirs and differentiates changes in fracture density from changes in steam saturation using seismic velocity ratio analyses. The study also shows that Rayleigh-wave-based techniques can differentiate changes in fracture density from changes in steam saturation, and including fluid pressure diffusion effects is crucial for reliable detection and characterization of steam in fractured geothermal reservoirs.
Article
Engineering, Chemical
Santiago G. Solazzi, Damien Jougnot, J. German Rubino, Klaus Holliger
Summary: We propose an analytical model to calculate frequency-dependent relative permeability functions for partially saturated porous media, taking into account viscous coupling effects. By considering the oscillatory motion of two immiscible fluid phases and solving the Navier-Stokes equations at the pore scale, we obtain closed analytical expressions for the complex-valued and frequency- and saturation-dependent relative permeability functions. Our results show that viscous coupling effects significantly impact flow characteristics in the viscous and inertial regimes and may induce two critical frequencies in the dynamic relative permeability curves.
TRANSPORT IN POROUS MEDIA
(2023)
Article
Geochemistry & Geophysics
Yanbin He, J. German Rubino, Nicolas D. Barbosa, Santiago G. Solazzi, Marco Favino, Tianning Chen, Jinghuai Gao, Klaus Holliger
Summary: Shear wave splitting is a reliable seismic attribute to characterize fractures in geological formations. This study finds that fracture connectivity significantly impacts the magnitude and polarization of shear wave splitting, resulting in a 90-degree rotation. Additionally, the type of fluid within connected fractures does not affect shear wave splitting.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Natalia N. Salva, Gabriel H. Paissan, Santiago G. Solazzi, J. German Rubino
Summary: This study proposes an analytical approach to compute the phase velocity and attenuation of P-waves traveling through parallel fractures. Numerical analysis shows two manifestations of fluid pressure diffusion in these cases. This approach is important for the remote detection and quantification of pore fluids using seismic waves.
GEOPHYSICAL PROSPECTING
(2023)
Article
Geochemistry & Geophysics
Nicolas D. Barbosa, Victoria A. Jimenez Martinez, Nima Gholizadeh Doonechaly, Tobias M. Mueller, Klaus Holliger
Summary: Fractures in the upper crust have a significant impact on fluid flow and pore pressure distribution. Experimental studies show that the hydraulic response of fractures is period and pressure amplitude dependent, likely related to fracture deformation.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Water Resources
Jonatan Pendiuk, Maria Florencia Degano, Luis Guarracino, Raul Eduardo Rivas
Summary: The practical utility of remote sensing techniques depends on their validation with ground-truth data. Validation requires similar spatial-temporal scales for ground measurements and remote sensing resolution. We propose the use of superconducting gravimeters (SGs) to obtain ground-truth evapotranspiration (ET) data at larger spatial scales. SGs measure gravity acceleration with high resolution within a few hundred meters and provide direct estimates of water mass changes to determine ET without disturbing the soil. Comparing SG data with MODIS-based ET products, this study demonstrates a good agreement at the monthly scale and highlights the potential of SGs for hydrogeological applications.
Article
Geochemistry & Geophysics
Edith Sotelo, Nicolas D. Barbosa, Santiago G. Solazzi, J. German Rubino, Marco Favino, Klaus Holliger
Summary: The aim of this study is to study the reflectivity response of stratified thin layers in seismic reflection studies using their homogenized viscoelastic equivalents. The estimation of the equivalent moduli is inherently affected by the boundary conditions associated with the embedding background. A novel homogenization procedure is proposed to incorporate the appropriate boundary conditions.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)