Simultaneous inversion of formation shear‐wave anisotropy parameters from cross‐dipole acoustic‐array waveform data

Geophysics ◽  
1999 ◽  
Vol 64 (5) ◽  
pp. 1502-1511 ◽  
Author(s):  
Xiaoming Tang ◽  
Raghu K. Chunduru
Keyword(s):  
Objective Function ◽  
Shear Wave ◽  
Waveform Inversion ◽  
New Technique ◽  
Dipole Source ◽  
Waveform Data ◽  
Simultaneous Inversion ◽  
Receiver Array ◽  
Acoustic Array ◽  
Anisotropy Parameters

This study presents an effective technique for obtaining formation azimuthal shear‐wave anisotropy parameters from four‐component dipole acoustic array waveform data. The proposed technique utilizes the splitting of fast and slow principal flexural waves in an anisotropic formation. First, the principal waves are computed from the four‐component data using the dipole source orientation with respect to the fast shear‐wave polarization azimuth. Then, the fast and slow principal waves are compared for all possible receiver combinations in the receiver array to suppress noise effects. This constructs an objective function to invert the waveform data for anisotropy estimates. Finally, the anisotropy and the fast shear azimuth are simultaneously determined by finding the global minimum of the objective function. The waveform inversion procedure provides a reliable and robust method for obtaining formation anisotropy from four‐component dipole acoustic logging. Field data examples are used to demonstrate the application and features of the proposed technique. A comparison study using the new and conventional techniques shows that the new technique not only reduces the ambiguity in the fast azimuth determination but also improves the accuracy of the anisotropy estimate. Some basic quality indicators of the new technique, along with the anisotropy analysis results, are presented to demonstrate the practical application of the inversion technique.

Objective-Function Behavior in Acoustic Full-Waveform Inversion

2013 ◽  
Vol 56 (5) ◽  
pp. 685-703
Author(s):  
DONG Liang-Guo ◽  
CHI Ben-Xin ◽  
TAO Ji-Xia ◽  
LIU Yu-Zhu
Keyword(s):  
Objective Function ◽  
Waveform Inversion ◽  
Full Waveform Inversion ◽  
Full Waveform

scholarly journals MM-MRE: a new technique to quantify individual muscle forces during isometric tasks of the wrist using MR elastography

2019 ◽  
Author(s):  
Andrea Zonnino ◽  
Daniel R. Smith ◽  
Peyton L. Delgorio ◽  
Curtis L. Johnson ◽  
Fabrizio Sergi
Keyword(s):  
Shear Wave ◽  
Muscle Force ◽  
Muscle Mechanics ◽  
Neuromuscular Control ◽  
Joint Torque ◽  
New Technique ◽  
Muscle Forces ◽  
Individual Muscle ◽  
Complete Set ◽  
A New Technique

AbstractNon-invasive in-vivo measurement of individual muscle force is limited by the infeasibility of placing force sensing elements in series with the musculo-tendon structures. At the same time, estimating muscle forces using EMG measurements is prone to inaccuracies, as EMG is not always measurable for the complete set of muscles acting around the joints of interest. While new methods based on shear wave elastography have been recently proposed to directly characterize muscle mechanics, they can only be used to measure muscle forces in a limited set of superficial muscles. As such, they are not suitable to study the neuromuscular control of movements that require coordinated action of multiple muscles.In this work, we present multi-muscle magnetic resonance elastography (MM-MRE), a new technique capable of quantifying individual muscle force from the complete set of muscles in the forearm, thus enabling the study of the neuromuscular control of wrist movements. MM-MRE integrates measurements of joint torque provided by an MRI-compatible instrumented handle with muscle-specific measurements of shear wave speed obtained via MRE to quantify individual muscle force using model-based estimator.A single-subject pilot experiment demonstrates the possibility of obtaining measurements from individual muscles and establishes that MM-MRE has sufficient sensitivity to detect changes in muscle mechanics following the application of isometric joint torque with self-selected intensity.

2D Laplace-Domain Waveform Inversion of Field Data Using a Power Objective Function

2013 ◽  
Vol 170 (12) ◽  
pp. 2075-2085 ◽  
Author(s):  
Eunjin Park ◽  
Wansoo Ha ◽  
Wookeen Chung ◽  
Changsoo Shin ◽  
Dong-Joo Min
Keyword(s):  
Objective Function ◽  
Field Data ◽  
Waveform Inversion ◽  
Laplace Domain

3D elastic full-waveform inversion of surface waves in the presence of irregular topography using an envelope-based misfit function

Geophysics ◽  
2018 ◽  
Vol 83 (1) ◽  
pp. R1-R11 ◽  
Author(s):  
Dmitry Borisov ◽  
Ryan Modrak ◽  
Fuchun Gao ◽  
Jeroen Tromp
Keyword(s):  
Surface Wave ◽  
Objective Function ◽  
Surface Waves ◽  
Large Scale ◽  
Body Wave ◽  
Waveform Inversion ◽  
Full Waveform Inversion ◽  
S Wave ◽  
Near Surface ◽  
Full Waveform

Full-waveform inversion (FWI) is a powerful method for estimating the earth’s material properties. We demonstrate that surface-wave-driven FWI is well-suited to recovering near-surface structures and effective at providing S-wave speed starting models for use in conventional body-wave FWI. Using a synthetic example based on the SEG Advanced Modeling phase II foothills model, we started with an envelope-based objective function to invert for shallow large-scale heterogeneities. Then we used a waveform-difference objective function to obtain a higher-resolution model. To accurately model surface waves in the presence of complex tomography, we used a spectral-element wave-propagation solver. Envelope misfit functions are found to be effective at minimizing cycle-skipping issues in surface-wave inversions, and surface waves themselves are found to be useful for constraining complex near-surface features.

User perceptions of different monitor modalities during high-fidelity simulation: Visual-Patient-avatar, Split Screen and Conventional - a qualitative analysis (Preprint)

2021 ◽  
Author(s):  
Samira Akbas ◽  
Sadiq Said ◽  
Tadzio Raoul Roche ◽  
Christoph Beat Nöthiger ◽  
Donat Rudolf Spahn ◽  
...  
Keyword(s):  
Situation Awareness ◽  
Simulation Study ◽  
Vital Signs ◽  
Numerical Data ◽  
New Technique ◽  
High Fidelity ◽  
High Fidelity Simulation ◽  
Care Providers ◽  
Clinical Implementation ◽  
Waveform Data

BACKGROUND Patient safety during anaesthesia is crucially dependent on the monitoring of vital signs. However, the values obtained must also be perceived and correctly classified by the attending care providers. To facilitate these processes, we developed Visual-Patient-avatar- an animated virtual model of the monitored patient, which innovatively presents numerical and waveform data following user-centred design principles. After a high-fidelity simulation study, we analysed participants' perceptions of three different monitor modalities, including this new technique. OBJECTIVE After a high-fidelity simulation study, we analysed participants' perceptions of three different monitor modalities, including this new technique. METHODS This study was a researcher-initiated, single-centre, qualitative study. We asked 92 care providers right after finishing three simulated emergency scenarios about their positive and negative opinions concerning the different monitor modalities. Following qualitative research methods, we processed the field notes obtained and derived main categories and corresponding subthemes. RESULTS We gained a total of 307 statements. Visual-Patient-avatar was the most occurring term in both positive and negative responses. We identified three main categories and divided them into eleven positive and negative subthemes. In assigning the statements to one of the topics, we achieved substantial inter-rater reliability. Most of the statements concerned the design and usability features of the avatar, respectively, the Split Screen mode. CONCLUSIONS This study qualitatively reviewed the clinical applicability of the Visual-Patient-avatar technique in a high-fidelity simulation study and revealed strengths and limitations of the avatar only und Split Screen modality. We received valuable suggestions for improving the design. The requirement of training before clinical implementation was reinforced. The responses regarding the Split Screen suggested that this symbiotic modality generates improved situation awareness combined with numerical data and accurate curves.

Lithospheric structure of the North American Craton constrained by full waveform inversion

2021 ◽  
Author(s):  
Tong Zhou ◽  
Min Chen ◽  
Ziyi Xi ◽  
Jiaqi Li
Keyword(s):  
Shear Wave ◽  
Wave Speed ◽  
Waveform Inversion ◽  
Continental Lithosphere ◽  
Shear Wave Speed ◽  
The North ◽  
Full Waveform ◽  
Radial Anisotropy ◽  
North American Craton ◽  
Superior Craton

<p>Cratonic lithosphere is believed to be rigid and less deformed during a long period of time. However, the detailed structure of Cratons may bring information of the complex formation and assemblage process of the continental lithosphere. Here, we present the seismic radial anisotropic structure of the North American Craton (NAC) constrained by a regional full-waveform inversion (FWI) with 465,422 high-quality frequency-dependent travel time misfit measurements with the shortest period of 15 s from both the body wave and surface wave recordings of 5,120 stations and 160 earthquakes located in the contiguous U.S and surrounding regions. Started from an initial model constructed by combining US.2016 and Crust1.0 in the crust and S40RTS (isotropic) in the mantle, we are able to have the optimized crustal structure in terms of initial waveform similarity and get rid of existing features from other radially anisotropic mantle models.</p><p>Our new model reveals the NAC lithosphere with about +2% voigt shear wave speed anomaly and an average thickness of 200–250 km beneath the Superior Craton, and becomes thinner towards the eastern, the southern, and the southwestern margins with a thickness decreased to 100–150 km. The radial anisotropy manifests a layer of higher horizontal shear wave speed V<sub>SH </sub>(ξ=V<sub>SH</sub><sup>2</sup>/V<sub>SV</sub><sup>2</sup>>1) beneath the core of Superior Craton down to around 160 km, where the higher vertical shear wave speed V<sub>SV </sub>(ξ<1) is observed beneath 160 km. Such radial anisotropy layering is also observed in the margin of continental lithosphere but with shallower depth. The radial anisotropic layer matches the receiver function results of mid-lithosphere discontinuities of the Craton cores, and the lithosphere conductivity result. The radial anisotropy layering observation confirms the two-layered lithosphere structure of the NAC, where the upper layer likely represents the original radial anisotropy fabric related to the cooling of the craton core, while the lower layer might be related to the tectonic processes more recently, e.g., accretion . The lithospheric thinning beneath the NAC margins indicates the deformation of the lithosphere and is likely controlled by the large-scale mantle convection, therefore relates to the further modification process of the NAC.</p>

Towed Marine Dipole Source for Shear Wave Generation

2016 ◽  
Author(s):  
Y. Nagai ◽  
A. Tsuda ◽  
H. Ozasa ◽  
H. Hatanaka ◽  
K. Tanaka ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Generation ◽  
Dipole Source

Full-waveform inversion with borehole constraints for elastic VTI media

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. R553-R563
Author(s):  
Sagar Singh ◽  
Ilya Tsvankin ◽  
Ehsan Zabihi Naeini
Keyword(s):  
Objective Function ◽  
Reservoir Characterization ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Rock Physics ◽  
Anisotropic Media ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Trade Offs ◽  
Vti Media

The nonlinearity of full-waveform inversion (FWI) and parameter trade-offs can prevent convergence toward the actual model, especially for elastic anisotropic media. The problems with parameter updating become particularly severe if ultra-low-frequency seismic data are unavailable, and the initial model is not sufficiently accurate. We introduce a robust way to constrain the inversion workflow using borehole information obtained from well logs. These constraints are included in the form of rock-physics relationships for different geologic facies (e.g., shale, sand, salt, and limestone). We develop a multiscale FWI algorithm for transversely isotropic media with a vertical symmetry axis (VTI media) that incorporates facies information through a regularization term in the objective function. That term is updated during the inversion by using the models obtained at the previous inversion stage. To account for lateral heterogeneity between sparse borehole locations, we use an image-guided smoothing algorithm. Numerical testing for structurally complex anisotropic media demonstrates that the facies-based constraints may ensure the convergence of the objective function towards the global minimum in the absence of ultra-low-frequency data and for simple (even 1D) initial models. We test the algorithm on clean data and on surface records contaminated by Gaussian noise. The algorithm also produces a high-resolution facies model, which should be instrumental in reservoir characterization.

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