Journal articles: 'Body wave tomography'

1

Mercier, J. P., M. G. Bostock, J. F. Cassidy, K. Dueker, J. B. Gaherty, E. J. Garnero, J. Revenaugh, and G. Zandt. "Body-wave tomography of western Canada." Tectonophysics 475, no. 3-4 (October 2009): 480–92. http://dx.doi.org/10.1016/j.tecto.2009.05.030.

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Karimpour, Mohammadkarim, Evert Cornelis Slob, and Laura Valentina Socco. "Physically Constrained 2D Joint Inversion of Surface and Body Wave Tomography." Journal of Environmental and Engineering Geophysics 27, no. 2 (June 2022): 57–71. http://dx.doi.org/10.32389/jeeg21-031.

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Joint inversion of different geophysical methods is a powerful tool to overcome the limitations of individual inversions. Body wave tomography is used to obtain P-wave velocity models by inversion of P-wave travel times. Surface wave tomography is used to obtain S-wave velocity models through inversion of the dispersion curves data. Both methods have inherent limitations. We focus on the joint body and surface waves tomography inversion to reduce the limitations of each individual inversion. In our joint inversion scheme, the Poisson ratio was used as the link between P-wave and S-wave velocities, and the same geometry was imposed on the final velocity models. The joint inversion algorithm was applied to a 2D synthetic dataset and then to two 2D field datasets. We compare the obtained velocity models from individual inversions and the joint inversion. We show that the proposed joint inversion method not only produces superior velocity models but also generates physically more meaningful and accurate Poisson ratio models.

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Maupin, Valérie. "Combining asynchronous data sets in regional body-wave tomography." Geophysical Journal International 224, no. 1 (October 5, 2020): 401–15. http://dx.doi.org/10.1093/gji/ggaa473.

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SUMMARY Regional body-wave tomography is a very popular tomographic method consisting in inverting relative traveltime residuals of teleseismic body waves measured at regional networks. It is well known that the resulting inverse seismic model is relative to an unknown vertically varying reference model. If jointly inverting data obtained with networks in the vicinity of each other but operating at different times, the relative velocity anomalies in different areas of the model may have different reference levels, possibly introducing large-scale biases in the model that may compromise the interpretation. This is very unfortunate as we have numerous examples of asynchronous network deployments which would benefit from a joint analysis. We show here how a simple improvement in the formulation of the sensitivity kernels allows us to mitigate this problem. Using sensitivity kernels that take into account that data processing implies a zero mean residual for each event, the large-scale biases that otherwise arise in the inverse model using data from asynchronous station deployment are largely removed. We illustrate this first with a very simple 3-station example, and then compare the results obtained using the usual and the relative kernels in synthetic tests with more realistic station coverage, simulating data acquisition at two neighbouring asynchronous networks.

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Catchings, Rufus D., Michael J. Rymer, and Mark R. Goldman. "San Andreas Fault Exploration Using Refraction Tomography and S-Wave-Type and Fϕ-Mode Guided Waves." Bulletin of the Seismological Society of America 110, no. 6 (July 21, 2020): 3088–102. http://dx.doi.org/10.1785/0120200136.

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ABSTRACT Surface ruptures from the 18 April 1906 M∼7.9 San Francisco earthquake were distributed over an ∼35-meter-wide zone at San Andreas Lake on the San Francisco Peninsula in California (Schussler, 1906). Since ∼1906, the surface ruptures have been largely covered by water, but with water levels at near-historic low levels in 2008–2011, we observed that the 1906 surface ruptures were no longer visible. As a fault imaging test, we acquired refraction tomography and guided-wave data across the 1906 surface ruptures in 2011. We found that individual fault traces, as mapped by Schussler (1906), can be identified on the basis of discrete low-velocity zones (VS and VP, reduced ∼40% and ∼34%, respectively) and high-amplitude guided waves. Guided waves have traditionally been observed as large-amplitude waveforms over wide (hundreds of meters to kilometers) zones of faulting, but we demonstrate that by evaluating guided waves (including Rayleigh/Love- and P/SV-types) in terms of peak ground velocity (PGV), individual near-surface fault traces within a fault zone can be precisely located, even more than 100 yr after the surface ruptures. Such precise exploration can be used to focus paleoseismic trenching efforts and to identify or exclude faulting at specific sites. We evaluated PGV of both S-wave-type and Fϕ-mode-type guided waves and found that both wave types can be used to identify subsurface fault traces. At San Andreas Lake (main fault), S-wave-type guided waves travel up to 18% slower than S body waves, and Fϕ-mode guided waves travel ∼60% slower than P body waves but ∼15% faster than S body waves. We found that guided-wave amplitudes vary with frequency but are up to five times higher than those of body waves, including the S wave. Our data are consistent with the concept that guided waves can be a strong-shaking hazard during large-magnitude earthquakes.

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Tran, Khiem T., Michael McVay, Michael Faraone, and David Horhota. "Sinkhole detection using 2D full seismic waveform tomography." GEOPHYSICS 78, no. 5 (September 1, 2013): R175—R183. http://dx.doi.org/10.1190/geo2013-0063.1.

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We have developed an application of 2D time-domain waveform tomography for detection of embedded sinkholes and anomalies. The measured seismic surface wavefields were inverted using a full-waveform inversion (FWI) technique, based on a finite-difference solution of 2D elastic wave equations and the Gauss-Newton inversion method. The key advantage of this approach is the ability to generate all possible wave propagation modes of seismic wavefields (body waves and Rayleigh waves) that are then compared with measured data to infer complex subsurface properties.The pressure-wave (P-wave) and shear-wave (S-wave) velocities are inverted independently and simultaneously. The FWI was applied to one synthetic and two real experimental data sets. The inversion results of synthetic data showed the useful capability of the waveform analysis in identifying an embedded void. The inversion results of real data sets showed that the waveform analysis was able to delineate (1) an embedded concrete culvert and (2) a complex profile with an embedded void and highly variable bedrock laterally and vertically. An independent invasive test (standard penetration test) was also conducted to verify the seismic test results.

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Zhang, Xin, Corinna Roy, Andrew Curtis, Andy Nowacki, and Brian Baptie. "Imaging the subsurface using induced seismicity and ambient noise: 3-D tomographic Monte Carlo joint inversion of earthquake body wave traveltimes and surface wave dispersion." Geophysical Journal International 222, no. 3 (May 9, 2020): 1639–55. http://dx.doi.org/10.1093/gji/ggaa230.

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SUMMARY Seismic body wave traveltime tomography and surface wave dispersion tomography have been used widely to characterize earthquakes and to study the subsurface structure of the Earth. Since these types of problem are often significantly non-linear and have non-unique solutions, Markov chain Monte Carlo methods have been used to find probabilistic solutions. Body and surface wave data are usually inverted separately to produce independent velocity models. However, body wave tomography is generally sensitive to structure around the subvolume in which earthquakes occur and produces limited resolution in the shallower Earth, whereas surface wave tomography is often sensitive to shallower structure. To better estimate subsurface properties, we therefore jointly invert for the seismic velocity structure and earthquake locations using body and surface wave data simultaneously. We apply the new joint inversion method to a mining site in the United Kingdom at which induced seismicity occurred and was recorded on a small local network of stations, and where ambient noise recordings are available from the same stations. The ambient noise is processed to obtain inter-receiver surface wave dispersion measurements which are inverted jointly with body wave arrival times from local earthquakes. The results show that by using both types of data, the earthquake source parameters and the velocity structure can be better constrained than in independent inversions. To further understand and interpret the results, we conduct synthetic tests to compare the results from body wave inversion and joint inversion. The results show that trade-offs between source parameters and velocities appear to bias results if only body wave data are used, but this issue is largely resolved by using the joint inversion method. Thus the use of ambient seismic noise and our fully non-linear inversion provides a valuable, improved method to image the subsurface velocity and seismicity.

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Clarke, Timothy J. "The complete ordered ray expansion-II. Multiphase body wave tomography." Geophysical Journal International 115, no. 2 (November 1993): 435–44. http://dx.doi.org/10.1111/j.1365-246x.1993.tb01197.x.

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Shomali, Z. Hossein, and Roland G. Roberts. "Non-linear body wave teleseismic tomography along the TOR array." Geophysical Journal International 148, no. 3 (March 27, 2002): 562–74. http://dx.doi.org/10.1046/j.1365-246x.2002.01592.x.

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9

Catheline, Stefan. "Passive elastography: A shear wave tomography of the human body." Journal of the Acoustical Society of America 141, no. 5 (May 2017): 3527. http://dx.doi.org/10.1121/1.4987440.

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10

Stähler, S. C., K. Sigloch, and T. Nissen-Meyer. "Triplicated P-wave measurements for waveform tomography of the mantle transition zone." Solid Earth Discussions 4, no. 2 (July 2, 2012): 783–821. http://dx.doi.org/10.5194/sed-4-783-2012.

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Abstract. Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attemped, due to the mismatch between the complex and bandlimited data and the (ray-theoretical) modeling methods. Here we present a data processing and modeling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that it is possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modeled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body-wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric earth.

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Stähler, S. C., K. Sigloch, and T. Nissen-Meyer. "Triplicated P-wave measurements for waveform tomography of the mantle transition zone." Solid Earth 3, no. 2 (November 7, 2012): 339–54. http://dx.doi.org/10.5194/se-3-339-2012.

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Abstract. Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attempted, due to a mismatch between the complex and band-limited data and the (ray-theoretical) modelling methods. Here we present a data processing and modelling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that is it possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modelled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric Earth.

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Obrebski, Mathias, Richard M. Allen, Fengxue Zhang, Jiatie Pan, Qingju Wu, and Shu-Huei Hung. "Shear wave tomography of China using joint inversion of body and surface wave constraints." Journal of Geophysical Research: Solid Earth 117, B1 (January 2012): n/a. http://dx.doi.org/10.1029/2011jb008349.

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13

Zhou, Bing, Stewart Greenhalgh, and Alan Green. "Nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media." GEOPHYSICS 73, no. 4 (July 2008): D17—D33. http://dx.doi.org/10.1190/1.2910827.

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Crosshole seismic tomography often is applied to image the velocity structure of an interwell medium. If the rocks are anisotropic, the tomographic technique must be adapted to the complex situation; otherwise, it leads to a false interpretation. We propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes. This method is based on a new version of the first-order traveltime perturbation equation. It directly uses the derivative of the phase velocity rather than the eigenvectors of the body-wave modes to overcome the singularity problem for application to the two quasi-shear waves. We applied an iterative nonlinear solver incorporating our kinematic ray-tracing scheme and directly compute the Jacobian matrix in an arbitrary reference medium. This reconstructs the five elastic moduli or Thomsen parameters from the first-arrival traveltimes of the three seismic body waves (qP, qSV, qSH) in strongly and weakly anisotropic media. We conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock, reconstructing a fault embedded in a strongly anisotropic background, and imaging a complicated four-layer model containing a small channel and a buried dipping interface. We compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme, which showed the capability and superiority of the new scheme for crosshole tomographic imaging.

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14

Liang, Xiaofeng, Eric Sandvol, Suzanne Kay, Benjamin Heit, Xiaohui Yuan, Patrick Mulcahy, Chen Chen, Larry Brown, Diana Comte, and Patricia Alvarado. "Delamination of southern Puna lithosphere revealed by body wave attenuation tomography." Journal of Geophysical Research: Solid Earth 119, no. 1 (January 2014): 549–66. http://dx.doi.org/10.1002/2013jb010309.

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15

Barthwal, Himanshu, Frank J. Calixto, and Mirko van der Baan. "3-D attenuation tomography from microseismicity in a mine." Geophysical Journal International 219, no. 3 (August 30, 2019): 1805–17. http://dx.doi.org/10.1093/gji/ggz396.

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SUMMARY We perform 3-D attenuation tomography using microseismic data recorded during an underground mine development. The whole path attenuation parameter t* is obtained by least-squares inversion of P-wave amplitude spectra of the events recorded by 7 monitoring wells each containing 4 3C geophones. The corner frequencies obtained during P-wave spectral inversion of the 488 identified events range from 140 to 220 Hz which are typical for microseismic events with a negative moment magnitude of around –1. The quality factor Q obtained from tomographic inversion varies between 9 and 72 with the event cluster location characterized by a low Q value of 10. Two high Q regions of 30–72 are located at depths of 0.45 and 0.5 km, one between 0–0.15 km east and 0.3–0.5 km north which correlate with the high-grade ore deposit, and another centred around 0.45 km east and 0.25 km north. The high (-low) Q values, in general, correlates with the high (-low) velocities present in the velocity tomography model. A joint interpretation of seismic attenuation and velocity models reveals the heterogeneity present in the mine which aids in delineating the ore body using seismic waves in addition to other measurements such as gravity inversion and direct sampling from drillholes.

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Borisov, Dmitry, Ryan Modrak, Fuchun Gao, and Jeroen Tromp. "3D elastic full-waveform inversion of surface waves in the presence of irregular topography using an envelope-based misfit function." GEOPHYSICS 83, no. 1 (January 1, 2018): R1—R11. http://dx.doi.org/10.1190/geo2017-0081.1.

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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.

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Golos, E. M., H. Fang, H. Yao, H. Zhang, S. Burdick, F. Vernon, A. Schaeffer, S. Lebedev, and R. D. van der Hilst. "Shear Wave Tomography Beneath the United States Using a Joint Inversion of Surface and Body Waves." Journal of Geophysical Research: Solid Earth 123, no. 6 (June 2018): 5169–89. http://dx.doi.org/10.1029/2017jb014894.

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Toney, Liam D., Robert E. Abbott, Leiph A. Preston, David G. Tang, Tori Finlay, and Kristin Phillips‐Alonge. "Joint Body‐ and Surface‐Wave Tomography of Yucca Flat, Nevada, Using a Novel Seismic Source." Bulletin of the Seismological Society of America 109, no. 5 (August 13, 2019): 1922–34. http://dx.doi.org/10.1785/0120180322.

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Abstract In preparation for the next phase of the Source Physics Experiments, we acquired an active‐source seismic dataset along two transects totaling more than 30 km in length at Yucca Flat, Nevada, on the Nevada National Security Site. Yucca Flat is a sedimentary basin which has hosted more than 650 underground nuclear tests (UGTs). The survey source was a novel 13,000 kg modified industrial pile driver. This weight drop source proved to be broadband and repeatable, richer in low frequencies (1–3 Hz) than traditional vibrator sources and capable of producing peak particle velocities similar to those produced by a 50 kg explosive charge. In this study, we performed a joint inversion of P‐wave refraction travel times and Rayleigh‐wave phase‐velocity dispersion curves for the P‐ and S‐wave velocity structure of Yucca Flat. Phase‐velocity surface‐wave dispersion measurements were obtained via the refraction microtremor method on 1 km arrays, with 80% overlap. Our P‐wave velocity models verify and expand the current understanding of Yucca Flat’s subsurface geometry and bulk properties such as depth to Paleozoic basement and shallow alluvium velocity. Areas of disagreement between this study and the current geologic model of Yucca Flat (derived from borehole studies) generally correlate with areas of widely spaced borehole control points. This provides an opportunity to update the existing model, which is used for modeling groundwater flow and radionuclide transport. Scattering caused by UGT‐related high‐contrast velocity anomalies substantially reduced the number and frequency bandwidth of usable dispersion picks. The S‐wave velocity models presented in this study agree with existing basin‐wide studies of Yucca Flat, but are compromised by diminished surface‐wave coherence as a product of this scattering. As nuclear nonproliferation monitoring moves from teleseismic to regional or even local distances, such high‐frequency (>5 Hz) scattering could prove challenging when attempting to discriminate events in areas of previous testing.

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McVey, B. G., E. E. E. Hooft, B. A. Heath, D. R. Toomey, M. Paulatto, J. V. Morgan, P. Nomikou, and C. B. Papazachos. "Magma accumulation beneath Santorini volcano, Greece, from P-wave tomography." Geology 48, no. 3 (December 9, 2019): 231–35. http://dx.doi.org/10.1130/g47127.1.

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Abstract Despite multidisciplinary evidence for crustal magma accumulation below Santorini volcano, Greece, the structure and melt content of the shallow magmatic system remain poorly constrained. We use three-dimensional (3-D) velocity models from tomographic inversions of active-source seismic P-wave travel times to identify a pronounced low-velocity anomaly (–21%) from 2.8 km to 5 km depth localized below the northern caldera basin. This anomaly is consistent with depth estimates of pre-eruptive storage and a recent inflation episode, supporting the interpretation of a shallow magma body that causes seismic attenuation and ray bending. A suite of synthetic tests shows that the geometry is well recovered while a range of melt contents (4%–13% to fully molten) are allowable. A thin mush region (2%–7% to 3%–10% melt) extends from the main magma body toward the northeast, observed as low velocities confined by tectono-magmatic lineaments. This anomaly terminates northwest of Kolumbo; little to no melt underlies the seamount from 3 to 5 km depth. These structural constraints suggest that crustal extension and edifice loads control the geometry of magma accumulation and emphasize that the shallow crust remains conducive to melt storage shortly after a caldera-forming eruption.

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Gao, Lei, Haijiang Zhang, Lina Gao, Chuansong He, Hailiang Xin, and Weisen Shen. "High-resolution Vs tomography of South China by joint inversion of body wave and surface wave data." Tectonophysics 824 (February 2022): 229228. http://dx.doi.org/10.1016/j.tecto.2022.229228.

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Liu, Tianshi, and Haiming Zhang. "Asymptotic analysis for dispersion relations and travel times in noise cross-correlations: spherically symmetric case." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, no. 2218 (October 2018): 20180382. http://dx.doi.org/10.1098/rspa.2018.0382.

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The cross-correlations of ambient noise or earthquake codas are massively used in seismic tomography to measure the dispersion curves of surface waves and the travel times of body waves. Such measurements are based on the assumption that these kinematic parameters in the cross-correlations of noise coincide with those in Green's functions. However, the relation between the cross-correlations of noise and Green's functions deserves to be studied more precisely. In this paper, we use the asymptotic analysis to study the dispersion relations of surface waves and the travel times of body waves, and come to the conclusion that for the spherically symmetric Earth model, when the distribution of noise sources is laterally uniform, the dispersion relations of surface waves and the travel times of SH body-wave phases in noise correlations should be exactly the same as those in Green's functions.

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Mercerat, E. D., and G. Nolet. "Comparison of ray- and adjoint-based sensitivity kernels for body-wave seismic tomography." Geophysical Research Letters 39, no. 12 (June 16, 2012): n/a. http://dx.doi.org/10.1029/2012gl052002.

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23

Pilia, Simone, Hao Hu, Mohammed Y. Ali, Nicholas Rawlinson, and Aiguo Ruan. "Upper mantle structure of the northeastern Arabian Platform from teleseismic body-wave tomography." Physics of the Earth and Planetary Interiors 307 (October 2020): 106549. http://dx.doi.org/10.1016/j.pepi.2020.106549.

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Esteve, Clement, Andrew J. Schaeffer, and Pascal Audet. "Upper mantle structure underlying the diamondiferous Slave craton from teleseismic body-wave tomography." Tectonophysics 757 (April 2019): 187–202. http://dx.doi.org/10.1016/j.tecto.2019.01.012.

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Rawlinson, N., and S. Fishwick. "Seismic structure of the southeast Australian lithosphere from surface and body wave tomography." Tectonophysics 572-573 (October 2012): 111–22. http://dx.doi.org/10.1016/j.tecto.2011.11.016.

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Nakata, Nori, Jason P. Chang, Jesse F. Lawrence, and Pierre Boué. "Body wave extraction and tomography at Long Beach, California, with ambient‐noise interferometry." Journal of Geophysical Research: Solid Earth 120, no. 2 (February 2015): 1159–73. http://dx.doi.org/10.1002/2015jb011870.

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Nurhandoko, Bagus E. B., Syahrul Mubarok, Indriani Sukmana, Fajril Ambia, Budi Sulistyanto, Syafrizal Syafrizal, Y. Wiyanto, and Hussein Rudiyanto. "Characterization of Subsurface Coal Using Seismic Tomography : a Case Study in Muara Enim South Sumatera." Indonesian Journal of Physics 20, no. 2 (November 3, 2016): 41–44. http://dx.doi.org/10.5614/itb.ijp.2009.20.2.5.

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In recent years, coal as well as coal bed methane becomes important energy resources. Therefore, the characterization of coal seam is also important in predicting the quality, porosity and pore’s fluid of CBM’s reservoir. Seismic wave is very important parameter to characterize reservoir’s properties of coal bed methane as well as quality of coal. In this paper, we show methodology to image the subsurface velocity using seismic tomography. It is very useful for characterizing the coal’s seam as well as to detect the position of intrusion body. A case study was carried out in Suban Block, Muara Enim Sumatera. This coal mining block contains igneous rock intrusion which becoming main control of coal’s quality. Coal which is close with intrusion body usually has better quality than far zone. To acquire the data, we used 48 channels of seismic recorder controlled by telemetry for controlling the shot and first break. Then, data are processed by Fresnel interpolated wave-path (FIW) wide-band inversion tomography. The results show that the intrusion body can be imaged clearly and the seam coal can be delineated from well information. The information in well controls are quite match with tomography results.

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Barros, Sámia Valéria dos Santos, Niro Higuchi, Claudete Catanhede do Nascimento, Roberto Daniel de Araújo, and Prof Dr Flávio de São Pedro Filho. "Wave Propagation Technology in Non-destructive assays for Wood Qualifying in Tropical Amazon." International Journal for Innovation Education and Research 7, no. 8 (August 31, 2019): 259–74. http://dx.doi.org/10.31686/ijier.vol7.iss8.1673.

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Non-destructive tests use techniques which allow a body to be evaluated without changing its physical, mechanical and dimensional features and without compromising its future use. Impulse tomography analysis is a non-destructive method which allows a piece of wood to be analyzed by passing mechanical waves through it, allowing researchers to evaluate its qualities in advance and detect the presence of defects. This research reports the assessment of the efficiency of impulse tomography as a technique for identifying defects and the in situ evaluation of tree wood from Amazonian timber species. The data were collected at INPA's Tropical Forestry Experimental Station (ZF-2), located at BR 174, Manaus/AM, in a plot 1 (one) hectare in size, where 7 species were chosen at random. For evaluation, the ARBOTOM pulse tomograph at DAP (diameter at breast height) was used to rapidly capture cross sectional images of the wood. Next, the trees were cut to evaluate cross sections of the wood by eye and samples were taken to determine the density of the wood. The results enabled researchers to detect the presence of distinct zones in the wood by varying the mechanical wave speed indicated by various colour zones revealed in the X-ray. These colour differences are attributable to variations in density related to the different wood substances in the tree. It was found that the wood density and mechanical wave velocity correlated with R² 0.647. The dynamic elastic modulus of the species studied was satisfactory, showing a good degree of resistance. Impulse tomography technique provides complete information and can assist forest managers to make a decision about tree felling that is guided by the assessment of the internal quality of the wood.

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Mercerat, E. Diego, Guust Nolet, and Christophe Zaroli. "Cross-borehole tomography with correlation delay times." GEOPHYSICS 79, no. 1 (January 1, 2014): R1—R12. http://dx.doi.org/10.1190/geo2013-0059.1.

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We evaluated a comprehensive numerical experiment of finite-frequency tomography with ray-based (“banana-doughnut”) kernels that tested all aspects of this method, starting from the generation of seismograms in a 3D model, the window selection, and the crosscorrelation with seismograms predicted for a background model, to the final regularized inversion. In particular, we tested if the quasilinearity of crosscorrelation delays allowed us to forego multiple (linearized) iterations in the case of strong reverberations characterizing multiple scattering and the gain in resolution that can be obtained by observing body-wave dispersion. Contrary to onset times, traveltimes observed by crosscorrelation allowed us to exploit energy arriving later in the time window centered in the P-wave or any other indentifiable ray arrival, either scattered from, or diffracted around, lateral heterogeneities. We tested using seismograms calculated by the spectral element method in a cross-borehole experiment conducted in a 3D checkerboard cube. The use of multiple frequency bands allowed us to estimate body-wave dispersion caused by diffraction effects. The large velocity contrast (10%) and the regularity of the checkerboard pattern caused severe reverberations that arrived late in the crosscorrelation windows. Nevertheless, the model resulting from the inversion with a data fit with reduced [Formula: see text] resulted in an excellent correspondence with the input model and allowed for a complete validation of the linearizations that lay at the basis of the theory. The use of multiple frequencies led to a significant increase in resolution. Moreover, we evaluated a case in which the sign of the anomalies in the checkerboard was systematically reversed in the ray-theoretical solution, a clear demonstration of the reality of the “doughnut-hole” effect. The experiment validated finite-frequency theory and disqualified ray-theoretical inversions of crosscorrelation delay times.

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Nunn, C., S. W. Roecker, F. J. Tilmann, K. F. Priestley, R. Heyburn, E. A. Sandvol, J. F. Ni, Y. J. Chen, W. Zhao, and t. I. Team. "Imaging the lithosphere beneath NE Tibet: teleseismic P and S body wave tomography incorporating surface wave starting models." Geophysical Journal International 196, no. 3 (December 24, 2013): 1724–41. http://dx.doi.org/10.1093/gji/ggt476.

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Shi, Huiyan, Tonglin Li, Rongzhe Zhang, Gongcheng Zhang, and Hetian Yang. "Imaging of the Upper Mantle Beneath Southeast Asia: Constrained by Teleseismic P-Wave Tomography." Remote Sensing 12, no. 18 (September 13, 2020): 2975. http://dx.doi.org/10.3390/rs12182975.

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It is of great significance to construct a three-dimensional underground velocity model for the study of geodynamics and tectonic evolution. Southeast Asia has attracted much attention due to its complex structural features. In this paper, we collected relative travel time residuals data for 394 stations distributed in Southeast Asia from 2006 to 2019, and 14,011 seismic events were obtained. Then, teleseismic tomography was applied by using relative travel time residuals data to invert the velocity where the fast marching method (FMM) and subspace method were used for every iteration. A novel 3D P-wave velocity model beneath Southeast Asia down to 720 km was obtained using this approach. The tomographic results suggest that the southeastern Tibetan Plateau, the Philippines, Sumatra, and Java, and the deep part of Borneo exhibit high velocity anomalies, while low velocity anomalies were found in the deep part of the South China Sea (SCS) basin and in the shallow part of Borneo and areas near the subduction zone. High velocity anomalies can be correlated to subduction plates and stable land masses, while low velocity anomalies can be correlated to island arcs and upwelling of mantle material caused by subduction plates. We found a southward subducting high velocity body in the Nansha Trough, which was presumed to be a remnant of the subduction of the Dangerous Grounds into Borneo. It is further inferred that the Nansha Trough and the Dangerous Grounds belong to the same tectonic unit. According to the tomographic images, a high velocity body is located in the deep underground of Indochina–Natuna Island–Borneo–Palawan, depth range from 240 km to 660 km. The location of the high velocity body is consistent with the distribution range of the ophiolite belt, so we speculate that the high velocity body is the remnant of thee Proto-South China Sea (PSCS) and Paleo-Tethys. This paper conjectures that the PSCS was the southern branch of Paleo-Tethys and the gateway between Paleo-Tethys and the Paleo-Pacific Ocean. Due to the squeeze of the Australian plate, PSCS closed from west to east in a scissor style, and was eventually extinct under Borneo.

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Jung, Hyungyeong, and Sunghwan Moon. "Reconstruction of the initial function from the solution of the fractional wave equation measured in two geometric settings." Electronic Research Archive 30, no. 12 (2022): 4436–46. http://dx.doi.org/10.3934/era.2022225.

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<abstract><p>Photoacoustic tomography (PAT) is a novel and rapidly developing technique in the medical imaging field that is based on generating acoustic waves inside of an object of interest by stimulating non-ionizing laser pulses. This acoustic wave was measured by using a detector on the outside of the object it was then converted into an image of the human body after several inversions. Thus, one of the mathematical problems in PAT is reconstructing the initial function from the solution of the wave equation on the outside of the object. In this study, we consider the fractional wave equation and assume that the point-like detectors are located on the sphere and hyperplane. We demonstrate a way to recover the initial function from the data, namely, the solution of the fractional wave equation, measured on the sphere and hyperplane.</p></abstract>

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Amirbekyan, Abel, and Volker Michel. "Splines on the three-dimensional ball and their application to seismic body wave tomography." Inverse Problems 24, no. 1 (January 25, 2008): 015022. http://dx.doi.org/10.1088/0266-5611/24/1/015022.

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Mercier, Jean-Philippe, Willem de Beer, Jean-Pascal Mercier, and Simon Morris. "Evolution of a block cave from time-lapse passive source body-wave traveltime tomography." GEOPHYSICS 80, no. 2 (March 1, 2015): WA85—WA97. http://dx.doi.org/10.1190/geo2014-0155.1.

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Most underground mines are equipped with microseismic monitoring systems that allow the detection, location, and characterization of microseismic events. Microseismic events can be exploited to understand the rock mass response to mining. However, seismicity provides information only for regions that are seismically active. Although some information on nonseismically active regions can be obtained from point measurements and numerical modeling, these methods suffer from limitations of their own. Passive source traveltime body-wave tomography (passive source tomography [PST]) uses information readily collected by microseismic monitoring systems, namely, the P- and/or S-wave traveltimes and microseismic event hypocenter locations. This technique allowes the simultaneous estimation of the velocity distribution between sensors and microseismic events and the correction of microseismic event hypocenter locations. In this paper, we present an application of time-lapse PST to the Northparkes Mines E26 Lift 2 block cave showing that PST can be used to obtain information on evolution and distribution of seismic velocities, leading to a better understanding of stress distribution and redistribution and of rock mass behavior during the development and production phases. In particular, we found that (1) the magnitude of the velocity perturbation varied through time and appeared to be strongly correlated with the intensity of microseismic activity, the mining rate, and the nature of the mining activity, (2) the velocity models provided information that allowed for the inference of the cave geometry and its evolution through time, (3) the stress distributions inferred from the velocity model were not fully consistent with a widely accepted conceptual stress redistribution model, which may reflect the significant influence of rock mass inhomogeneities and the mining sequence, (4) seismicity was found in regions in which velocity was higher and lower than the background velocity, and (5) there was no obvious correlation between geology and velocity distribution and evolution.

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Boiero, Daniele, and Laura Valentina Socco. "Joint inversion of Rayleigh-wave dispersion and P-wave refraction data for laterally varying layered models." GEOPHYSICS 79, no. 4 (July 1, 2014): EN49—EN59. http://dx.doi.org/10.1190/geo2013-0212.1.

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We implemented a joint inversion method to build P- and S-wave velocity models from Rayleigh-wave and P-wave refraction data, specifically designed to deal with laterally varying layered environments. A priori information available over the site and any physical law to link model parameters can be also incorporated. We tested and applied the algorithm behind the method. The results from a field data set revealed advantages with respect to individual surface-wave analysis (SWA) and body wave tomography (BWT). The algorithm imposed internal consistency for all the model parameters relaxing the required a priori assumptions (i.e., Poisson’s ratio level of confidence in SWA) and the inherent limitations of the two methods (i.e., velocity decreases for BWT).

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LeBlanc, Anne-Marie, Richard Fortier, Michel Allard, Calin Cosma, and Sylvie Buteau. "Seismic cone penetration test and seismic tomography in permafrost." Canadian Geotechnical Journal 41, no. 5 (September 1, 2004): 796–813. http://dx.doi.org/10.1139/t04-026.

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Two high-resolution multi-offset vertical seismic profile (VSP) surveys were carried out in a permafrost mound near Umiujaq in northern Quebec, Canada, while performing seismic cone penetration tests (SCPT) to study the cryostratigraphy and assess the body waves velocities and the dynamic properties of warm permafrost. Penetrometer-mounted triaxial accelerometers were used as the VSP receivers, and a swept impact seismic technique (SIST) source generating both compressional and shear waves was moved near the surface following a cross configuration of 40 seismic shot-point locations surrounding each of the two SCPTs. The inversion of travel times based on a simultaneous iterative reconstruction technique (SIRT) provided tomographic images of the distribution of seismic velocities in permafrost. The Young's and shear moduli at low strains were then calculated from the seismic velocities and the permafrost density measured on core samples. The combination of multi-offset VSP survey, SCPT, SIST, and SIRT for tomographic imaging led to new insights in the dynamic properties of permafrost at temperatures close to 0 °C. The P- and S-wave velocities in permafrost vary from 2400 to 3200 m/s and from 900 to 1750 m/s, respectively, for a temperature range between 0.2 and 2.0 °C. The Young's modulus varies from 2.15 to 13.65 GPa, and the shear modulus varies from 1.00 to 4.75 GPa over the same range of temperature.Key words: permafrost, seismic cone penetration test, vertical seismic profiling, seismic tomography, dynamic properties.

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Koley, Soumen, Maria Bader, Jo van den Brand, Xander Campman, Henk Jan Bulten, Frank Linde, and Bjorn Vink. "Surface and underground seismic characterization at Terziet in Limburg—the Euregio Meuse–Rhine candidate site for Einstein Telescope." Classical and Quantum Gravity 39, no. 2 (January 11, 2022): 025008. http://dx.doi.org/10.1088/1361-6382/ac2b08.

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Abstract We present a detailed characterization of surface and underground seismic noise measured at Limburg in the south of the Netherlands. This location is the Euregio Meuse–Rhine candidate for hosting Einstein Telescope, a future observatory for gravitational waves. Seismic noise measurements were performed with an array of seismometers installed on the surface. Passive seismic methods like beamforming were used to extract the propagation wave types of ambient seismic noise and the Rayleigh-wave dispersion in the region. Subsurface shear-wave models sensitive to depths of 300 m were derived by using the Rayleigh-wave dispersion and ellipticity. Subsurface P-wave velocities to depths of 200 m were obtained from an active seismic survey. Wavepath Eikonal tomography was used on the source-receiver refracted-wave travel-times to obtain a subsurface P-wave velocity model. Both the passive and the active seismic data analysis point to the presence of a layered geology with a soft-soil to hard-rock transition occurring at a shallow depth of about 25 to 40 m. The surface arrays are complemented by two permanent tri-axial seismometers installed on the surface and in a borehole at 250 m depth. Their data are used to interpret the surface-wave and body-wave contributions to the observed seismic noise. We use a cross-correlation analysis and compute the theoretical surface-wave eigenfunctions to understand the contributions of the different wave types at different frequencies. We observe that below 4 Hz in the horizontal component and 9 Hz in the vertical component, the seismic noise at depth is dominantly due to surface waves. Above these frequencies a significant contribution can be attributed to both nearby and far-away body-wave sources. At a depth of 250 m we find that the surface noise power has been damped by up to a factor 104 above about 2 Hz. The Limburg geology with soft-soil on top of hard-rock efficiently damps the anthropogenic noise produced at the surface. This implies that Einstein Telescope’s test masses are shielded from anthropogenic seismic noise and construction at greater depth will not bring significant further improvements in this regard. A body-wave background has been identified that contributes about half of the total underground seismic noise at 250 m depth for frequencies above 4 Hz. It remains to be studied if subtraction schemes for Newtonian noise originating from this body-wave background will be necessary. Finally, we estimate an interferometer downtime of about 3% due to regional and teleseismic earthquakes. We believe this is acceptable as it is comparable to current experience at the LIGO and Virgo interferometer sites.

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Lin, Guoqing, Victor A. Huerfano, and Wenyuan Fan. "Crustal Architecture of Puerto Rico Using Body-Wave Seismic Tomography and High-Resolution Earthquake Relocation." Seismological Research Letters 93, no. 2A (December 1, 2021): 555–66. http://dx.doi.org/10.1785/0220210223.

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Abstract Puerto Rico is a highly seismically active island, where several damaging historical earthquakes have occurred and frequent small events persist. It situates at the boundary between the Caribbean and North American plates, featuring a complex fault system. Here, we investigate the seismotectonic crustal structure of the island by interpreting the 3D compressional-wave velocity VP and compressional- to shear-wave velocity ratio VP/VS models and by analyzing the distribution of the relocated earthquakes. The 3D velocity models are obtained by applying the simul2000 tomographic inversion algorithm based on the phase arrivals recorded by the Puerto Rico seismic network. We find high-VP and low-VP/VS anomalies in the eastern and central province between the Great Northern Puerto Rico fault zone and the Great Southern Puerto Rico fault zone, correlating with the Utuado pluton. Further, there are low-VP anomalies beneath both the Great Southern Puerto Rico fault zone and the South Lajas fault, indicating northerly dipping structures from the southwest to the northwest of the island. We relocate 19,095 earthquakes from May 2017 to April 2021 using the new 3D velocity model and waveform cross-correlation data. The relocated seismicity shows trends along the Investigator fault, the Ponce faults, the Guayanilla rift, and the Punta Montalva fault. The majority of the 2019–2021 Southwestern Puerto Rico earthquakes are associated with the Punta Montalva fault. Earthquakes forming 17° northward-dipping structures at various depths possibly manifest continuation of the Muertos trough, along which the Caribbean plate is being subducted beneath the Puerto Rico microplate. Our results show complex fault geometries of a diffuse fault network, suggesting possible subduction process accommodated by faults within a low-velocity zone.

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Ritsema, J., H. J. van Heijst, J. H. Woodhouse, and A. Deuss. "Long-period body wave traveltimes through the crust: implication for crustal corrections and seismic tomography." Geophysical Journal International 179, no. 2 (November 2009): 1255–61. http://dx.doi.org/10.1111/j.1365-246x.2009.04365.x.

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Singh, Arun, J. P. Mercier, M. Ravi Kumar, D. Srinagesh, and R. K. Chadha. "Continental scale body wave tomography of India: Evidence for attrition and preservation of lithospheric roots." Geochemistry, Geophysics, Geosystems 15, no. 3 (March 2014): 658–75. http://dx.doi.org/10.1002/2013gc005056.

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Simmons, N. A., S. C. Myers, C. Morency, A. Chiang, and D. R. Knapp. "SPiRaL: a multiresolution global tomography model of seismic wave speeds and radial anisotropy variations in the crust and mantle." Geophysical Journal International 227, no. 2 (July 20, 2021): 1366–91. http://dx.doi.org/10.1093/gji/ggab277.

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SUMMARY SPiRaL is a joint global-scale model of wave speeds (P and S) and anisotropy (vertical transverse isotropy, VTI) variations in the crust and mantle. The model is comprised of >2.1 million nodes with five parameters at each node that capture velocity variations for P- and S-waves travelling at arbitrary directions in transversely isotropic media with a vertical symmetry axis (VTI). The crust (including ice, water, sediments and crystalline layers) is directly incorporated into the model. The default node spacing is approximately 2° in the lower mantle and 1° in the crust and upper mantle. The grid is refined with ∼0.25° minimum node spacing in highly sampled regions of the crust and upper mantle throughout North America and Eurasia. The data considered in the construction of SPiRaL includes millions of body wave traveltimes (crustal, regional and teleseismic phases with multiples) and surface wave (Rayleigh and Love) dispersion. A multiresolution inversion approach is employed to capture long-wavelength heterogeneities commonly depicted in global-scale tomography images as well as more localized details that are typically resolved in more focused regional-scale studies. Our previous work has demonstrated that such global-scale models with regional-scale detail can accurately predict both teleseismic and regional body wave traveltimes, which is necessary for more accurate location of small seismic events that may have limited signal at teleseismic distances. SPiRaL was constructed to predict traveltimes for event location and long-period waveform dispersion for seismic source inversion applications in regions without sufficiently tuned models. SPiRaL may also serve as a starting model for full-waveform inversion (FWI) with the goal of fitting waves with periods 10–50 s over multiple broad regions (thousands of kilometres) and potentially the globe. To gain insight to this possibility, we simulated waveforms for a small set of events using SPiRaL and independent waveform-based models for comparison. For the events tested, the performance of the traveltime-based SPiRaL model is shown to be generally on par with regional 3-D waveform-based models in three regions (western United States, Middle East, Korean Peninsula) suggesting SPiRaL may serve as a starting model for FWI over broad regions.

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Liu, Ying, Huajian Yao, Haijiang Zhang, and Hongjian Fang. "The Community Velocity Model V.1.0 of Southwest China, Constructed from Joint Body- and Surface-Wave Travel-Time Tomography." Seismological Research Letters 92, no. 5 (April 21, 2021): 2972–87. http://dx.doi.org/10.1785/0220200318.

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Abstract Southwest China, located at the southeastern margin of the Tibetan plateau, plays an important role for the plateau growth and its material extrusion. It has complicated tectonic environment and strong seismic activities including the 2008 Wenchuan great earthquake. Numerous geophysical studies have been conducted in southwest China. However, a community velocity model (CVM) in this region is still not available, which makes it difficult to have a consistent catalog of earthquake locations and focal mechanisms and a consistent velocity model for simulating strong ground motions and evaluating earthquake hazards. In this study, we aim at building a high-resolution CVM (both VP and VS) of the crust and uppermost mantle in southwest China along with earthquake locations by joint inversion of body- and surface-wave travel-time data. In total, we have assembled 386,958 P- and 372,662 S-wave first arrival times and nearly 8100 Rayleigh-wave dispersion curves in the period band of 5–50 s. A multigrid strategy is adopted in the joint inversion. A coarser horizontal grid interval of 0.5° is first used and then a finer grid interval of 0.25° is used with initial models interpolated from the coarser-grid inverted velocity models. The spatial resolution of both VP and VS models can reach up to 0.5° horizontally and 10 km vertically according to the checkerboard tests. The comparisons of our inverted VP and VS models with those from other studies show general consistency in large-scale features. The inverted models are further validated by P-wave arrival times from active sources and Rayleigh-wave data. In general, our velocity models show two low-velocity zones in the middle-lower crust and a prominent high-velocity region in between them. Our new models have been served as the first version of the CVM in southwest China (SWChinaCVM-1.0) for future studies.

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Blom, Nienke, Alexey Gokhberg, and Andreas Fichtner. "Seismic waveform tomography of the central and eastern Mediterranean upper mantle." Solid Earth 11, no. 2 (April 30, 2020): 669–90. http://dx.doi.org/10.5194/se-11-669-2020.

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Abstract. We present a seismic waveform tomography of the upper mantle beneath the central and eastern Mediterranean down to the mantle transition zone. Our methodology incorporates in a consistent manner the information from body and multimode surface waves, source effects, frequency dependence, wavefront healing, anisotropy and attenuation. This allows us to jointly image multiple parameters of the crust and upper mantle. Based on the data from ∼ 17 000 unique source–receiver pairs, gathered from 80 earthquakes, we image radially anisotropic S velocity, P velocity and density. We use a multi-scale approach in which the longest periods (100–150 s) are inverted first, broadening to a period band of 28–150 s. Thanks to a strategy that combines long-period signals and a separation of body and surface wave signals, we are able to image down to the mantle transition zone in most of the model domain. Our model shows considerable detail in especially the northern part of the domain, where data coverage is very dense, and displays a number of clear and coherent high-velocity structures across the domain that can be linked to episodes of current and past subduction. These include the Hellenic subduction zone, the Cyprus subduction zone and high-velocity anomalies beneath the Italian peninsula and the Dinarides. This model is able to explain data from new events that were not included in the inversion.

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Martin, M., and F. Wenzel. "High-resolution teleseismic body wave tomography beneath SE-Romania - II. Imaging of a slab detachment scenario." Geophysical Journal International 164, no. 3 (March 2006): 579–95. http://dx.doi.org/10.1111/j.1365-246x.2006.02884.x.

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Syracuse, E. M., M. Maceira, H. Zhang, and C. H. Thurber. "Seismicity and structure of Akutan and Makushin Volcanoes, Alaska, using joint body and surface wave tomography." Journal of Geophysical Research: Solid Earth 120, no. 2 (February 2015): 1036–52. http://dx.doi.org/10.1002/2014jb011616.

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Diomidova, Valentina N., Oksana V. Zakharova, Marina A. Safonova, and Olga V. Valeeva. "ANALYSIS OF THE CORRELATIONAL RELATIONSHIP BETWEEN THE RESULTS OF ULTRASOUND ELASTOGRAPHY AND THE VALUES OF THE MEASURED DIFFUSION COEFFICIENT IN ASSESSING UTERINE AND ADNEXAL STRUCTURES IN REPRODUCTIVE AGE WOMEN." Acta medica Eurasica, no. 3 (September 30, 2022): 1–11. http://dx.doi.org/10.47026/2413-4864-2022-3-1-11.

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The purpose of the study. To study the correlational relationship between the results obtained by examining the uterus and ovaries in healthy women of reproductive age using shear wave ultrasound elastography with elastometry and magnetic resonance imaging (MRI) and assessment of the measured diffusion coefficient (MDC) of diffusion-weighted images (DWI). Materials and methods. The study group consisted of 45 healthy women of reproductive age (the average age was 32.9±3.1 years). All of them underwent ultrasound examination with the technology of two-dimensional shear wave elastography with elastometry (Aixplorer, Supersonic Imagine, France) according to the method developed and implemented by us. The MRI of uterine and ovarian structures was performed using the DWI protocol (Excelart Vantage Atlas magnetic resonance tomograph, Toshiba, Japan, 1.5 T), the myometrium and the uterine mucosa in the body and cervix, ovaries were evaluated. In the automatic mode, the MDC of unaltered structures in the uterine body and cervix and their appendages was calculated in the area of interest on ADC-maps. The degree of correlational relationship between the results of ultrasound elastography with elastometry and magnetic resonance tomography with an estimate of the measured diffusion coefficient was calculated. Results. Correlation analysis of the relationship between rigidity and the MDC of uterine and adnexal structures showed a direct inverse relationship between these values and a high degree of connection by Cheddock scale (p = 0.000000). At this, lesser MDC values (mm2 /s) of similar structures of the organs under study corresponded to large quantitative values of the Young's elasticity modulus (kPa) of all uterine and ovarian structures. Conclusion. The obtained data make it possible to optimize the diagnostic algorithm and to supplement the standard protocols for ultrasound and magnetic resonance imaging studies of gynecological organs using two-dimensional shear wave elastography with elastometry and magnetic resonance tomography with an assessment of the measured diffusion coefficient of diffusion-weighted images.

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Yuan, Yanhua O., Ebru Bozdağ, Caio Ciardelli, Fuchun Gao, and F. J. Simons. "The exponentiated phase measurement, and objective-function hybridization for adjoint waveform tomography." Geophysical Journal International 221, no. 2 (February 13, 2020): 1145–64. http://dx.doi.org/10.1093/gji/ggaa063.

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SUMMARY Seismic tomography has arrived at the threshold of the era of big data. However, how to extract information optimally from every available time-series remains a challenge; one that is directly related to the objective function chosen as a distance metric between observed and synthetic data. Time-domain cross-correlation and frequency-dependent multitaper traveltime measurements are generally tied to window selection algorithms in order to balance the amplitude differences between seismic phases. Even then, such measurements naturally favour the dominant signals within the chosen windows. Hence, it is difficult to select all usable portions of seismograms with any sort of optimality. As a consequence, information ends up being lost, in particular from scattered waves. In contrast, measurements based on instantaneous phase allow extracting information uniformly over the seismic records without requiring their segmentation. And yet, measuring instantaneous phase, like any other phase measurement, is impeded by phase wrapping. In this paper, we address this limitation by using a complex-valued phase representation that we call ‘exponentiated phase’. We demonstrate that the exponentiated phase is a good substitute for instantaneous-phase measurements. To assimilate as much information as possible from every seismogram while tackling the non-linearity of inversion problems, we discuss a flexible hybrid approach to combine various objective functions in adjoint seismic tomography. We focus on those based on the exponentiated phase, to take into account relatively small-magnitude scattered waves; on multitaper measurements of selected surface waves; and on cross-correlation measurements on specific windows to select distinct body-wave arrivals. Guided by synthetic experiments, we discuss how exponentiated-phase, multitaper and cross-correlation measurements, and their hybridization, affect tomographic results. Despite their use of multiple measurements, the computational cost to evaluate gradient kernels for the objective functions is scarcely affected, allowing for issues with data quality and measurement challenges to be simultaneously addressed efficiently.

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Jia, Zhuo, and Gongbo Zhang. "Teleseismic Tomography for Imaging the Upper Mantle Beneath Northeast China." Applied Sciences 10, no. 13 (June 30, 2020): 4557. http://dx.doi.org/10.3390/app10134557.

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Tomographic imaging technology is a geophysical inversion method. According to the ray scanning, this method carries on the inversion calculation to the obtained information, and reconstructs the image of the parameter distribution rule of elastic wave and electromagnetic wave in the measured range, so as to delineate the structure of the geological body. In this paper, teleseismic tomography is applied by using seismic travel time data to constrain layered crustal structure where Fast Marching Methods (FMM) and the subspace method are considered as forward and inverse methods, respectively. Based on the travel time data picked up from seismic waveform data in the study region, the P-wave velocity structure beneath Northeast China down to 750 km is obtained. It can be seen that there are low-velocity anomalies penetrating the mantle transition zone under the Changbai volcano group, Jingpohu Volcano, and Arshan Volcano, and these low-velocity anomalies extend to the shallow part. In this paper, it is suggested that the Cenozoic volcanoes in Northeast China were heated by the heat source provided by the dehydration of the subducted Pacific plate and the upwelling of geothermal matter in the lower mantle. The low-velocity anomaly in the north Songliao basin does not penetrate the mantle transition zone, which may be related to mantle convection and basin delamination. According to the low-velocity anomalies widely distributed in the upper mantle and the low-velocity bodies passing through the mantle transition zone beneath the volcanoes, this study suggests that the Cenozoic volcanoes in Northeast China are kindred and have a common formation mechanism.

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Sandoval, Senén, Edi Kissling, and Jörg Ansorge. "High-resolution body wave tomography beneath the SVEKALAPKO array: I.A priorithree-dimensional crustal model and associated traveltime effects on teleseismic wave fronts." Geophysical Journal International 153, no. 1 (April 2003): 75–87. http://dx.doi.org/10.1046/j.1365-246x.2003.01888.x.

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Bergounioux, Maïtine, Xavier Bonnefond, Thomas Haberkorn, and Yannick Privat. "An optimal control problem in photoacoustic tomography." Mathematical Models and Methods in Applied Sciences 24, no. 12 (August 15, 2014): 2525–48. http://dx.doi.org/10.1142/s0218202514500286.

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This paper is devoted to the introduction and study of a photoacoustic tomography model, an imaging technique based on the reconstruction of an internal photoacoustic source distribution from measurements acquired by scanning ultrasound detectors over a surface that encloses the body containing the source under study. In a nutshell, the inverse problem consists in determining absorption and diffusion coefficients in a system coupling a hyperbolic equation (acoustic pressure wave) with a parabolic equation (diffusion of the fluence rate), from boundary measurements of the photoacoustic pressure. Since such kinds of inverse problems are known to be generically ill-posed, we propose here an optimal control approach, introducing a penalized functional with a regularizing term in order to deal with such difficulties. The coefficients we want to recover stand for the control variable. We provide a mathematical analysis of this problem, showing that this approach makes sense. We finally write necessary first-order optimality conditions and give preliminary numerical results.

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Journal articles on the topic 'Body wave tomography'

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