On resolution and uniqueness in anisotropic crosshole traveltime tomography

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1184-1189 ◽  
Author(s):  
Paul R. Williamson
Keyword(s):  
Velocity Field ◽  
Radon Transform ◽  
P Wave ◽  
Traveltime Tomography ◽  
Slice Theorem ◽  
Spatial Frequencies ◽  
Specific Calculations ◽  
Dc Component ◽  
Spatially Varying ◽  
Spatial Support

The inclusion of anisotropy in P-wave traveltime tomography has been undertaken by several authors and in all cases some loss of resolution and uniqueness compared to the isotropic problem was observed. The origin of this problem is analysed for straight‐ray tomography using the Radon transform and the projection slice theorem. This analysis shows that the separation of the anisotropy from the isotropic velocity field can only be guaranteed for the dc component. Resolution at higher spatial frequencies depends upon the spatial support of the object, that is the separation of the holes in crosshole work, and the range of ray angles available. Specific calculations in the crosshole case suggest that even in media known to be horizontally stratified, it will probably be difficult to estimate spatially varying elliptical anisotropy at wavelengths less than a few times smaller than the hole separation, and Thomsen’s parameter, delta at wavelengths less than the hole separation itself. These results broadly agree with the empirical observations in the literature.

A reality check on full-wave inversion applied to land seismic data for near-surface modeling

2022 ◽  
Vol 41 (1) ◽  
pp. 40-46
Author(s):  
Öz Yilmaz ◽  
Kai Gao ◽  
Milos Delic ◽  
Jianghai Xia ◽  
Lianjie Huang ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Data ◽  
Surface Modeling ◽  
P Wave ◽  
Borehole Data ◽  
Near Surface ◽  
Traveltime Tomography ◽  
Wave Inversion ◽  
Full Wave ◽  
Elastic Inversion

We evaluate the performance of traveltime tomography and full-wave inversion (FWI) for near-surface modeling using the data from a shallow seismic field experiment. Eight boreholes up to 20-m depth have been drilled along the seismic line traverse to verify the accuracy of the P-wave velocity-depth model estimated by seismic inversion. The velocity-depth model of the soil column estimated by traveltime tomography is in good agreement with the borehole data. We used the traveltime tomography model as an initial model and performed FWI. Full-wave acoustic and elastic inversions, however, have failed to converge to a velocity-depth model that desirably should be a high-resolution version of the model estimated by traveltime tomography. Moreover, there are significant discrepancies between the estimated models and the borehole data. It is understandable why full-wave acoustic inversion would fail — land seismic data inherently are elastic wavefields. The question is: Why does full-wave elastic inversion also fail? The strategy to prevent full-wave elastic inversion of vertical-component geophone data trapped in a local minimum that results in a physically implausible near-surface model may be cascaded inversion. Specifically, we perform traveltime tomography to estimate a P-wave velocity-depth model for the near-surface and Rayleigh-wave inversion to estimate an S-wave velocity-depth model for the near-surface, then use the resulting pairs of models as the initial models for the subsequent full-wave elastic inversion. Nonetheless, as demonstrated by the field data example here, the elastic-wave inversion yields a near-surface solution that still is not in agreement with the borehole data. Here, we investigate the limitations of FWI applied to land seismic data for near-surface modeling.

Integration of surface-based tomographic models for zonation and multimodel guided extrapolation of sparsely known petrophysical parameters

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. EN43-EN53 ◽  
Author(s):  
Barbara Hachmöller ◽  
Hendrik Paasche
Keyword(s):  
Cluster Analysis ◽  
Field Data ◽  
Spectral Cluster ◽  
P Wave ◽  
Fuzzy Membership ◽  
Geophysical Model ◽  
Natural Gamma ◽  
Refraction Seismic ◽  
Spatially Varying ◽  
Membership Information

We integrate the information of multiple tomographic models acquired from the earth’s surface by modifying a statistical approach recently developed for the integration of cross-borehole tomographic models. In doing so, we introduce spectral cluster analysis as the new core of the model integration procedure to capture the spatial heterogeneity present in all considered tomographic models and describe this heterogeneity in a fuzzy sense. Because spectral cluster algorithms analyze model structure locally, they are considered relatively robust with regard to systematically and spatially varying imaging capabilities typical for geophysical tomographic surveys conducted on the earth’s surface. Using a synthetic aquifer example, a fuzzy spectral cluster algorithm can be used to integrate the information provided by 2D tomographic refraction seismic and DC resistivity surveys. The integrated information in the fuzzy membership domain is then used to derive an integrated zonal geophysical model outlining the major structural units present in both input models. We also explain how the fuzzy membership information can be used to identify optimal locations for sparse logging of additional target parameters, i.e., porosity information in our synthetic example. We demonstrate how this sparse porosity information can be extrapolated based on all tomographic input models. The resultant 2D porosity model matches the original porosity distribution reasonably well within the spatial resolution limits of the underlying tomographic models. Consecutively, we apply this approach to a field data base acquired over a former river channel. Sparse information about natural gamma radiation is available and extrapolated on the basis of the fuzzy membership information obtained by spectral cluster analysis of 2D P-wave velocity and electrical resistivity models. This field data shows that the presented parameter extrapolation procedure is robust, even if the locations of target parameter acquisition have not been optimized with regard to the fuzzy membership information.

Inverse source problem based on two dimensionless dispersion-current functions in 2D evolution transport equations

2016 ◽  
Vol 24 (6) ◽  
Author(s):  
Adel Hamdi ◽  
Imed Mahfoudhi
Keyword(s):  
Velocity Field ◽  
Point Source ◽  
Time Dependent ◽  
Inverse Source Problem ◽  
Two Dimensional ◽  
Reaction Equation ◽  
Advection Dispersion ◽  
Dispersion Tensor ◽  
Spatially Varying ◽  
Dependent Point

AbstractThe paper deals with the nonlinear inverse source problem of identifying an unknown time-dependent point source occurring in a two-dimensional evolution advection-dispersion-reaction equation with spatially varying velocity field and dispersion tensor. The

Iterative P-wave velocity inversion using Markov chain Monte Carlo method

2020 ◽  
Author(s):  
Hyunggu Jun ◽  
Hyeong-Tae Jou ◽  
Han-Joon Kim ◽  
Sang Hoon Lee
Keyword(s):  
Wave Velocity ◽  
Seismic Data ◽  
Velocity Structure ◽  
Low Frequency ◽  
P Wave ◽  
Velocity Analysis ◽  
Seismic Section ◽  
Traveltime Tomography ◽  
P Wave Velocity ◽  
Frequency Components

<p>Imaging the subsurface structure through seismic data needs various information and one of the most important information is the subsurface P-wave velocity. The P-wave velocity structure mainly influences on the location of the reflectors during the subsurface imaging, thus many algorithms has been developed to invert the accurate P-wave velocity such as conventional velocity analysis, traveltime tomography, migration velocity analysis (MVA) and full waveform inversion (FWI). Among those methods, conventional velocity analysis and MVA can be widely applied to the seismic data but generate the velocity with low resolution. On the other hands, the traveltime tomography and FWI can invert relatively accurate velocity structure, but they essentially need long offset seismic data containing sufficiently low frequency components. Recently, the stochastic method such as Markov chain Monte Carlo (McMC) inversion was applied to invert the accurate P-wave velocity with the seismic data without long offset or low frequency components. This method uses global optimization instead of local optimization and poststack seismic data instead of prestack seismic data. Therefore, it can avoid the problem of the local minima and limitation of the offset. However, the accuracy of the poststack seismic section directly affects the McMC inversion result. In this study, we tried to overcome the dependency of the McMC inversion on the poststack seismic section and iterative workflow was applied to the McMC inversion to invert the accurate P-wave velocity from the simple background velocity and inaccurate poststack seismic section. The numerical test showed that the suggested method could successfully invert the subsurface P-wave velocity.</p>

scholarly journals SEISMIC TRAVELTIME TOMOGRAPHY IN THE DOM JOÃO FIELD, RECÔNCAVO BASIN, BRAZIL

2015 ◽  
Vol 33 (1) ◽  
pp. 89
Author(s):  
Naiane Pereira de Oliveira ◽  
Amin Bassrei
Keyword(s):  
Reservoir Characterization ◽  
New Technologies ◽  
Real Data ◽  
Seismic Inversion ◽  
P Wave ◽  
Gradient Algorithm ◽  
High Rate ◽  
Traveltime Tomography ◽  
Sonic Log ◽  
High Resolution Images

ABSTRACT. Tomography was incorporated in Exploration Geophysics with the intention of providing high-resolution images of regions in Earth’s subsurface that are characterized as potential reservoirs. In this work, seismic traveltime tomography in the transmission mode was applied to real data from the Dom João Field, Recôncavo Basin, State of Bahia, Brazil. This basin represents a landmark of oil exploration in Brazil and has been intensively studied since the 1950’s. Today, the Recôncavo Basin is still the principal oil producer in the State of Bahia, but there is a demand for new technologies, especially for mature fields, to improve hydrocarbon recovery. Acoustic ray tracing for the computation of traveltimes was used for forward modeling, and the conjugate gradient algorithm with regularization through derivative matrices was used as the inverse procedure. The estimated tomograms were consistent with available data from a sonic log near the acquisition area in terms of the layer geometry, as well as the P-wave velocity range. The results showed that traveltime tomography is feasible for the characterization of reservoirs with a high rate of vertical change, similar to the Dom Jo˜ao Field.Keywords: traveltime tomography, seismic inversion, regularization, reservoir characterization, Recˆoncavo Basin.RESUMO. A tomografia foi incorporada na Geofísica de Exploração justamente para fornecer imagens de alta resolução de regiões do interior da Terra, consideradas como potenciais reservatórios. Neste trabalho aplicamos a tomografia sísmica de tempos de trânsito no modo de transmissão em dados reais do Campo de Dom João, Bacia do Recôncavo, Estado da Bahia, Brasil. Esta bacia representa um marco da exploração de petróleo no Brasil e vem sendo exaustivamente estudada desde a década de 1950. Embora haja uma demanda por novas tecnologias, em especial para campos maduros, com o propósito de se aumentar a recuperação de hidrocarbonetos, a Bacia do Recôncavo é ainda a principal produtora do Estado da Bahia. Para o procedimento da modelagem direta foi utilizado o traçado de raios acústicos e para o procedimento inverso foi utilizado o algoritmo do gradiente conjugado com regularização através de matrizes de derivadas. Os tomogramas estimados foram consistentes com os dados provenientes do perfil sõnico de um poço próximo ao levantamento tomográfico analisado, tanto em termos de geometria de camadas, como também na faixa de velocidades da onda P. Os resultados mostraram que a tomografia de tempos de trânsito é viável para a caracterização de reservatórios com elevada taxa de variação vertical, que é o caso do Campo de Dom João.Palavras-chave: tomografia de tempos de trânsito, inversão sísmica, regularização, caracterização de reservatórios, Bacia do Recôncavo.

scholarly journals 3D P-wave velocity image beneath the Pannonian Basin using traveltime tomography

2019 ◽  
Vol 54 (3) ◽  
pp. 373-386 ◽  
Author(s):  
Máté Timkó ◽  
István Kovács ◽  
Zoltán Wéber
Keyword(s):  
Wave Velocity ◽  
Pannonian Basin ◽  
P Wave ◽  
Traveltime Tomography ◽  
P Wave Velocity ◽  
Velocity Image

scholarly journals P Wave Teleseismic Traveltime Tomography of the North American Midcontinent

2019 ◽  
Vol 124 (2) ◽  
pp. 1725-1742 ◽  
Author(s):  
Trevor A. Bollmann ◽  
Suzan Lee ◽  
Andrew W. Frederiksen ◽  
Emily Wolin ◽  
Justin Revenaugh ◽  
...  
Keyword(s):  
North American ◽  
P Wave ◽  
Traveltime Tomography ◽  
The North

Heterogeneous modification and reactivation of craton margin in northeast Asia: insight from teleseismic traveltime tomography of the Korean Peninsula

2020 ◽  
Author(s):  
Jung-Hun Song ◽  
Seongryong Kim ◽  
Junkee Rhie
Keyword(s):  
Upper Mantle ◽  
High Velocity ◽  
Korean Peninsula ◽  
Velocity Structure ◽  
Northeast Asia ◽  
Continental Collision ◽  
P Wave ◽  
Mantle Dynamics ◽  
Traveltime Tomography ◽  
Yeongnam Massif

<p>Margins of craton lithosphere are prone to ongoing modification process. Marginal tectonism such as slab subduction, continental collision, and mantle dynamics significantly influence properties of lithosphere in various scales. Thus, constraints on the detailed properties of craton margin are essential to understand the evolution of continental lithosphere. The eastern margin of the Eurasian plate is a natural laboratory that allows us to study the strong effects from multiple episodes of continental collision and subduction of different oceanic plates since their formation. Extensive reworking and destruction of the cratonic lithosphere mainly occurred in eastern China during the Mesozoic to Cenozoic, which leaves distinct geochemical and geophysical signatures. Specifically, the Korean Peninsula (KP) is known to consist of Archean–Proterozoic massifs (e.g., Gyeonggi, Yeongnam Massif) located in the forefront in northeast Asia, where current dynamics in the upper mantle and effects due to nearby subducting slabs are the most significant.</p><p>Here we present, for the first time in detail, 3-D velocity structure of KP by teleseismic body wave traveltime tomography. Detailed P-wave and S-wave images of the crust and upper mantle were constructed by approximately 5 years of data from dense arrays of seismometers. We newly found a thick high-velocity body beneath the southwestern KP with a thickness of ~150 km, which is thought as a fragment of lithospheric root beneath the Proterozoic Yeongnam Massif. Also, we found low velocities beneath the Gyeonggi Massif, eastern KP margin, and Gyeongsang continental arc-back-arc system, showing significant velocity contrasts (dlnVp of ~4.0% and dlnVs of ~6.0%) to the high-velocity structure. These features indicate significantly modified regions. In addition, there was a clear correlation of the upper mantle low-velocity anomalies and areas characterized by Cenozoic basaltic eruptions, high heat flow, and high tomography, suggesting that there are close associations between mantle dynamics and recent tectonic reactivation.</p><p>The presence of a remnant cratonic root beneath the KP and contrasting lithospheric structures across the different Precambrian massifs suggests highly heterogeneous modification along the Sino-Korean craton margin, which includes the KP and North China Craton. A striking localization of lithosphere modification among the different Precambrian massifs within the KP suggests that the structural heterogeneity of the craton margin is likely sharp in scale and thickness within a confined area. We suggest that intense interaction of upper mantle dynamics and inherent structural heterogeneities of a craton margin played an important role in shaping the current marginal lithosphere structure in northeast Asia.</p>

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