Joint Tomography Research Articles

DG-based joint transmission-reflection traveltime tomography and its application of borehole seismic

Abstract The limitations of the coverage range and density of transmission wave often result in less-than-ideal results in traveltime tomography. In contrast, joint transmission-reflection traveltime tomography can not only recover deep structures that transmission tomography cannot detect but also optimize its inversion results. In this article, we perform joint tomography on borehole seismic (VSP, RVSP and crosswell seismic) data to obtain near-wellbore structures. In the forward part, we solve the factored equation by the discontinuous Galerkin (DG) method to calculate the transmission/reflection traveltime. Due to the large wavefront curvature near the source point, the traveltime errors generated by the numerical simulation will propagate from the source to all the calculation domains. According to the factorization principle, the equation solution is decomposed into two parts to solve the point-source singularity. To further improve the accuracy of solving traveltime, we use the DG method to solve the factored eikonal equation with additive factors (the factored DG method), obtaining second-order accuracy solution. The adjoint-state method is employed in the inversion section to calculate the gradient of the misfit function. And we use the traveltime difference observed inside the model to define the misfit function, which is more suitable for borehole seismic and avoids the influence of surface normal vectors on gradients. Numerical tests applied on models indicate that the joint tomography method has the potential to accurately inverse the seismic structure information near the well and recover the deep underground structure.

Macroscopic Bell state between a millimeter-sized spin system and a superconducting qubit

Entanglement is a fundamental property in quantum mechanics that systems share inseparable quantum correlation regardless of their mutual distances. Owing to the fundamental significance and versatile applications, the generation of quantum entanglement between macroscopic systems has been a focus of current research. Here we report on the deterministic generation and tomography of the macroscopically entangled Bell state in a hybrid quantum system containing a millimeter-sized spin system ( ∼1×1019 atoms) and a micrometer-sized superconducting qubit. The deterministic generation is realized by coupling the macroscopic spin system and the qubit via a microwave cavity. Also, we develop a joint tomography approach to confirming the deterministic generation of the Bell state, which gives a generation fidelity of 0.90±0.01 . Our work makes the macroscopic spin system the largest system (in the sense of atom number) capable of generating the maximally entangled quantum state.

Crustal structure and tectonic boundary characteristics in South China: Constraints from joint tomography of ambient noise and gravity

Crustal structure and tectonic boundary characteristics in South China: Constraints from joint tomography of ambient noise and gravity

The effects of discontinuity topography in the mantle transition zone on global geodynamic observables and mantle heterogeneity

SUMMARYDespite progress in tomographic imaging of Earth's interior, a number of critical questions regarding the large-scale structure and dynamics of the mantle remain outstanding. One of those questions is the impact of phase-boundary undulations on global imaging of mantle heterogeneity and on geodynamic (i.e. convection-related) observables. To address this issue, we developed a joint seismic-geodynamic-mineral physical tomographic inversion procedure that incorporates lateral variations in the depths of the 410- and 660-km discontinuities. This inversion includes S-wave traveltimes, SS precursors that are sensitive to transition-zone topography, geodynamic observables/data (free-air gravity, dynamic surface topography, horizontal divergence of tectonic plates and excess core-mantle boundary ellipticity) and mineral physical constraints on thermal heterogeneity. Compared to joint tomography models that do not include data sensitivity to phase-boundary undulations in the transition zone, the inclusion of 410- and 660-km topography strongly influences the inference of volumetric anomalies in a depth interval that encompasses the transition zone and mid-mantle. It is notable that joint tomography inversions, which include constraints on transition-zone discontinuity topography by seismic and geodynamic data, yield more pronounced density anomalies associated with subduction zones and hotspots. We also find that the inclusion of 410- and 660-km topography may improve the fit to the geodynamic observables, depending on the weights applied to seismic and geodynamic data in the inversions. As a consequence, we find that the amplitude of non-thermal density anomalies required to explain the geodynamic data decreases in most of the mantle. These findings underline the sensitivity of the joint inversions to the inclusion of transition-zone complexity (e.g. phase-boundary topography) and the implications for the inferred non-thermal density anomalies in these depth regions. Finally, we underline that our inferences of 410- and 660-km topography avoid a commonly employed approximation that represents the contribution of volumetric heterogeneity to SS-wave precursor data. Our results suggest that this previously employed correction, based on a priori estimates of upper-mantle heterogeneity, might be a significant source of error in estimating the 410- and 660-km topography.

Feasibility study on joint tomography of refraction and reflection seismic waves for geotechnical purposes: a preliminary result

Many developing regions are subject to infrastructure magnification thus green-sustainable infrastructure has always been a relevant concern for most regulators and engineers. In order to support better urban planning, civil engineering operations, and environmental studies, an ample supply of information regarding the neighbouring environment is a must. This includes the information from the Earth’s subsurface, particularly the mechanical properties of soil and rock, on which the planning or action is executed. Complementarily, geophysical measurements utilizing the active seismic method can effectively provide an accurate approximation of the properties. This method includes generating seismic waves using the non-invasive artificial seismic source which then be collected on the Earth’s surface by a number of detectors called geophones. The recorded seismic waves bring information about the medium through which they propagate. They can provide the mechanical properties of the medium after applying some sequences of data interpretation techniques. Conventionally, this is done using only one type of seismic wave, either the refracted or reflected waves. In this study, we build a new procedure incorporating these two types of seismic waves to refine the inferred model. The result shows a promising improvement of the P-wave velocity model in terms of its resolution.

New Insights Into Potassic Intraplate Volcanism in Northeast China From Joint Tomography of Ambient Noise and Teleseismic Surface Waves

AbstractWudalianchi volcano is one of the youngest volcanic groups among the Cenozoic intraplate volcanoes in Northeast China and is notable for its potassium‐rich basalts. With newly deployed dense broadband seismic stations, we construct a high‐resolution 3‐D S‐wave velocity model of Wudalianchi volcano and its adjacent region, including the Keluo and Erkeshan volcanoes, using ambient noise and teleseismic surface wave tomography. We find a prominent channel‐like low‐velocity body that extends from the Moho to a depth of 100 km directly beneath the Wudalianchi, Erkeshan, and Keluo (WEK) volcanoes. This low‐velocity anomaly suggests that these three volcanoes may be derived from the same mantle magmatic source. Our model also shows that the prominent low‐velocity anomaly is associated with the pervasive low‐velocity anomalies at a depth of 100–200 km, which is interpreted as the asthenosphere. We further find that the lithosphere beneath the WEK volcanoes thickens abruptly from ∼80 to ∼110 km. Combining our results with those of other geophysical studies, we propose a geodynamic scenario for WEK intraplate volcanism. When the background asthenospheric flow in Northeast China encounters sharp changes in lithosphere thickness beneath the WEK volcanoes, it produces locally turbulent flow, promotes asthenospheric upwelling, and finally forms volcanoes.

Joint tomography of multi-cross-hole and borehole-to-surface seismic data for karst detection

Two-dimensional (2D) cross-hole seismic tomography is widely used in karst exploration. However, this method only obtains subsurface geological structures from the profiles of two adjacent wells and cannot acquire geological information from the lateral profile direction. The tomographic imaging area and accuracy are also limited owing to sparse ray density in the near-surface area. This approach is therefore not conducive to the spatial identification and evaluation of subsurface karst structures. To address this problem, we conducted multi-hole combined seismic tomography experiments and obtained high-density and high-quality seismic spatial data using an optimized observation system and acquisition parameters. We propose a new method of joint tomography of multi-cross-hole and borehole-to-surface seismic data. We performed 2D seismic tomography inversion by combining cross-hole data with borehole and surface data based on the theory of seismic tomography, and then used the data fusing from multiple wells based on the theory of kriging method. A pseudo-three-dimensional (3D) spatial velocity field of the experimental site is established. The results show that (1) the combined borehole and surface data provide richer ray-tracing information than the cross-hole dataset alone, (2) the pseudo-3D spatial velocity field and spatial distribution of seismic anomalies (karst) can be obtained using the proposed method, and (3) a comparison with actual borehole logging data verifies the effectiveness and accuracy of the proposed method in obtaining subsurface geological structures and detecting the spatial distribution of karst, which has significant practical and application potential.

Lithospheric structures of and tectonic implications for the central–east Tibetan plateau inferred from joint tomography of receiver functions and surface waves

SUMMARYWe present an updated joint tomographic method to simultaneously invert receiver function waveforms and surface wave dispersions for a 3-D S-wave velocity (Vs) model. By applying this method to observations from ∼900 seismic stations and with a priori Moho constraints from previous studies, we construct a 3-D lithospheric S-wave velocity model and crustal-thickness map for the central–east Tibetan plateau. Data misfit/fitting shows that the inverted model can fit the receiver functions and surface wave dispersions reasonably well, and checkerboard tests show the model can retrieve major structural information. The results highlight several features. Within the plateau crustal thickness is >60 km and outwith the plateau it is ∼40 km. Obvious Moho offsets and lateral variations of crustal velocities exist beneath the eastern (Longmen Shan Fault), northern (central–east Kunlun Fault) and northeastern (east Kunlun Fault) boundaries of the plateau, but with decreasing intensity. Segmented high upper-mantle velocities have varied occurrences and depth extents from south/southwest to north/northeast in the plateau. A Z-shaped upper-mantle low-velocity channel, which was taken as Tibetan lithospheric mantle, reflecting deformable material lies along the northern and eastern periphery of the Tibetan plateau, seemingly separating two large high-velocity mantle areas that, respectively, correspond to the Indian and Asian lithospheres. Other small high-velocity mantle segments overlain by the Z-shaped channel are possibly remnants of cold microplates/slabs associated with subductions/collisions prior to the Indian–Eurasian collision during the accretion of the Tibetan region. By integrating the Vs structures with known tectonic information, we derive that the Indian slab generally underlies the plateau south of the Bangong–Nujiang suture in central Tibet and the Jinsha River suture in eastern Tibet and west of the Lanchangjiang suture in southeastern Tibet. The eastern, northern, northeastern and southeastern boundaries of the Tibetan plateau have undergone deformation with decreasing intensity. The weakly resisting northeast and southeast margins, bounded by a wider softer channel of uppermost mantle material, are two potential regions for plateau expansion in the future.

TX2019slab: A New P and S Tomography Model Incorporating Subducting Slabs

AbstractLarge numbers of earthquakes occur in subduction zones that are marked by dipping, narrow high seismic velocity slabs. The existence of these fast velocity slabs can cause serious earthquake mislocation problems that can bias estimates of seismic travel time residuals. This can affect the recovery of subducting slabs in tomography as well as introduce significant artifacts into lower mantle structure in tomography models. In order to better account for known subducting slabs, we performed a new P and S wave joint tomography inversion incorporating a three‐dimensional thermal model of subducting slabs in the starting model. In addition, velocity and source locations were inverted for simultaneously. Our new P and S models feature higher‐amplitude subducting slabs compared with previous global tomography results. The S to P heterogeneity ratio based on the new tomography model indicates that thermal elastic effects alone cannot explain all the heterogeneities in the lower mantle. Much of the observed abnormal S to P heterogeneity ratio can be explained by anelastic effects, the spin transition, and phase transitions of bridgmanite to post‐perovskite in the lower mantle.

Joint Tomography with Seismic First-break And Reflection under Rugged Topographical Conditions

Seismic travel-time tomography is one of method which can inverse some information of underground medium such as structure, velocity distribution and so on. In order to solve the problem about seismic tomography under rugged topographical conditions. The author develops a new way for seismic tomography by combine LTI method based on hybrid meshes which has high fitting degree for the variable structure underground with LSQR algorithm. Thus, the joint tomography with seismic first-break and reflection under rugged topographical conditions has been achieved. The stability and effectiveness is verified by theoretical model test.

Integrated turning-ray and reflection tomography for velocity model building in foothill areas

A special challenge for land seismic exploration is estimating velocities, in part due to complex near-surface structures, and in some instances because of rugose topography over foothills. We have developed an integrated turning-ray and reflection-tomographic method to face this challenge. First, turning-ray tomography is performed to derive a near-surface velocity-depth model. Then, we combine the near-surface model with the initial-subsurface model. Taking the combined model as starting model, we go through a reflection tomographic process to build the model for imaging. During reflection tomography, the near-surface model and subsurface models are jointly updated. Our method has been successfully applied to a 2D complex synthetic data example and a 3D field data example. The results demonstrate that our method derives a very decent model even when there is no reflection information available in a few hundred meters underneath the surface. Joint tomography can lead to geologic plausible models and produce subsurface images with high fidelity.

Implications of Digital Image Processing in the Paraclinical Assessment of the Partially Edentated Patient

The application of certain digital processing techniques offers the possibility of extra accuracy in the interpretation of paraclinical examinations of this type, with profound implications in the diagnosis as well as in the hierarchy of the treatment plan. The purpose of this study is to identify the type of imaging processing for the identification of pathological elements from orthopantomographies and articular tomographies. A number of 20 orthopantomographies and 15 temporo-mandibular joint tomography have undergone through various image enhancement techniques. Various methods of image enhancement (enhancement) have been used for those procedures whereby it becomes more useful in the following aspects: specific details are highlighted; noise is eliminated; the image becomes more visually attractive. The workings were done in Corel PhotoPaint 7.0, using the automatic procedures available.The choice of a particular type of image enhancement technique has been selected for each type of pathology found in orthopantomographies or articular tomography, providing the best accuracy for an optimal imaging interpretation that underpins a precision diagnosis.Of the most useful imaging processing in the optimization of the orthopantomographic image accuracy the point-to-point transformations are to be noted. The image processing proposed in this article focused primarily on improving the radiological image attributes to highlight specific anatomical structures, and secondly, the contour detection, where it was necessary for the diagnostic purposes as well.

Impact of routine open-mouth osseous temporomandibular joint tomography on diagnosis and therapeutic options

The aim of this study was to evaluate the impact of routine open mouth osseous temporomandibular joint (TMJ) tomography on diagnosis and treatment planning of TMJ conditions. Investigating the need for such images is important to justify the additional radiation exposure imparted by such procedures. The records of patients who underwent closed- and open-mouth osseous TMJ tomography (planar film tomography up to the beginning of 2006; cone beam computed tomography from 2006 onward) were reviewed. Three examiners formulated a diagnosis and treatment plan based on the history, clinical findings, and tomography interpretation reports of closed-mouth images. Then they reviewed the interpretations of the open-mouth images and recorded whether they would change their original diagnosis and/or treatment plan on the basis of the findings. Descriptive analysis of the results was performed. The impact of routine open-mouth imaging on diagnosis and treatment planning was variable among the examiners. Examiners 1, 2, and 3 had a change in diagnosis in 7%, 5%, and 3% of cases, respectively, and a change in treatment plan in 1%, 1%, and 8%, respectively. Routine open-mouth osseous TMJ tomography had a minimal impact on diagnosis and treatment planning of TMJ conditions, which varied according to the treating clinician.

Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography

AbstractIn this paper, we combine active and passive source P wave seismic data to tomographically image the magmatic system beneath Newberry Volcano, located east of the Cascade arc. By using both travel times from local active sources and delay times from teleseismic earthquakes recorded on closely spaced seismometers (300–800 m), we significantly improve recovery of upper crustal velocity structure (<10 km depth). The tomographic model reveals a low‐velocity feature between 3 and 5 km depth that lies beneath the caldera, consistent with a magma body. In contrast to earlier tomographic studies, where elevated temperatures were sufficient to explain the recovered low velocities, the larger amplitude low‐velocity anomalies in our joint tomography model require low degrees of partial melt (∼10%), and a minimum melt volume of ∼2.5 km3. Furthermore, synthetic tests suggest that even greater magnitude low‐velocity anomalies, and by inference larger volumes of magma (up to 8 km3), are needed to explain the observed waveform variability. The lateral extent and shape of the inferred magma body indicates that the extensional tectonic regime at Newberry influences the emplacement of magmatic intrusions. Our study shows that jointly inverting active source and passive source seismic data improves tomographic imaging of the shallow crustal seismic structure of volcanic systems and that active source experiments would benefit from longer deployment times to also record teleseismic sources.

Smile because of Dr Robert Murray Ricketts.

Smile because of Dr Robert Murray Ricketts.

Flow of quantum correlations from a two-qubit system to its environment

The open-system dynamics of entanglement plays an important role in the assessment of the robustness of quantum information processes and also in the investigation of the classical limit of quantum mechanics. Here we show that, subjacent to this dynamics, there is a subtle flow of quantum correlations. We use a recently proposed optical setup, which allows joint tomography of system and environment, to show that the decay of an initial bipartite entangled state leads to the buildup of multipartite entanglement and quantum discord, the latter exhibiting a nonanalytic behavior that signals the emergence of maximal genuine quantum entanglement. The origin of this analyticity is shown to be distinct from similar behavior previously found in bipartite systems. Monogamy relations within the context of open-system dynamics explain this phenomenon.

Multiparameter TTI tomography of P-wave reflection and VSP data

Transversely isotropic models with a tilted symmetry axis (TTI media) are widely used in depth imaging of complex geologic structures. Here, we present a modification of a previously developed 2D P-wave tomographic algorithm for estimating heterogeneous TTI velocity fields and apply it to synthetic and field data. The symmetry-direction velocity [Formula: see text], anisotropy parameters [Formula: see text] and [Formula: see text], and symmetry-axis tilt [Formula: see text] are defined on a rectangular grid. To ensure stable reconstruction of the TTI parameters, reflection data are combined with walkaway vertical seismic profiling (VSP) traveltimes in joint tomographic inversion. To improve the convergence of the algorithm, we develop a three-stage model-updating procedure that gradually relaxes the constraints on the spatial variations of the anisotropy parameters, while the symmetry axis is kept orthogonal to the reflectors. Only at the final stage of the inversion are the parameters [Formula: see text], [Formula: see text], and [Formula: see text] updated on the same grid. We also incorporate geologic constraints into tomography by designing regularization terms that penalize parameter variations in the direction parallel to the interfaces. First, we examine the performance of the regularized joint tomography of reflection and VSP data for two sections of the BP TTI model that contain an anticline and a salt dome. All three TTI parameters in the shallow part of both sections (down to 5 km) are well resolved by the proposed model-updating process. Then, the algorithm is applied to a 2D section from 3D ocean-bottom seismic data acquired at Volve field in the North Sea. The inverted TTI model produces well-focused reflectors throughout the section and accurately positions the key horizons, which is confirmed by the available well markers.

Simultaneous options for cleft secondary deformities

Introduction:So much has been written by so many about secondary procedures in cleft surgery that testify not only the complexity and variable expression of cleft deformity itself but also the need to find methods of primary surgery that will reduce, if not avoid, adverse effects on all the structures and functions involved and affected. It must be the principal aim of cleft surgeon to restore the deformed and displaced regional anatomy to as close to normality as possible, whether or not true hypoplasia exists. The pathogenesis of secondary deformities is related to specific features as: the presence of scar tissues into the cleft basal bone area, that inhibits alveolar growth; scarring of palatal soft tissue, that inhibits growth and causes palatal orientation of dentoalveolar elements; and the exceeding lip tension, that may inhibits maxillary growth along dentoalveolar structures.Materials and Methods:From 2008 to 2011 at the Department of Cranio-Maxillo-Facial Surgery, Santo Spirito Hospital, Rome 25 patients (21 males and 4 females) who had undergone previous surgery for unilateral cleft lip and palate (UCLP) and bilateral cleft lip and palate (BCLP) were enrolled in our study. Diagnosis of deformity was made by means of a cephalometric and photographic analysis (Arnett), gipsometry and a radiological assessment (orthopantomography, lateral and frontal cephalometric X-rays). Moreover, every patient was studied with a temporomandibular joint (TMJ) tomography, TMJ magnetic resonance imaging (MRI) and a computerized gnatography to better evaluate potential TMJ dysfunctions. The surgical procedures adopted simultaneously were: Total or segmental maxillomandibular osteotomies, genioplasty, rhinoplasty, labioplasty, and application of facial prosthesis. Every patient received a postoperative questionnaire to evaluate his/her satisfaction with the surgery performed.Results:The surgical procedures adopted were Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO) in 16 patients (65%) and only Le Fort I osteotomy in 9 patients (35%). A relapse of malformation occurred in 4.5% of cases. Concerning the patient questionnaire, 96% of patients were satisfied with the jaw surgery and favorable for combined surgery, 88% were satisfied with lip-nose surgery, and finally 76% would advise to a friend.Conclusions:Simultaneous correction of the deformities is indicated as to avoid several surgical distresses for the patient, to improve facial aesthetic and function in one surgical step, and to reduce risk of psychological consequences.

Value of 99Tcm-MDP SPECT bone scintigraphy in diagnosis of unilateral condylar hyperplasia of the mandible

Objective To investigate the clinical value of 99Tcm-MDP SPECT scintigraphy in diagnosis of unilateral condylar hyperplasia (UCH) of the mandible.Methods Temporomandibular joint tomography using 99Tcm-MDP SPECT was performed in 56 UCH patients (22 males,34 females,mean age 21.5 y) preoperatively and 10 controls with other diseases (5 males,5 females,mean age 22.6 y).Thirtyone UCH patients received high condylar resection,and the corresponding histopathological results were analyzed.All scintigrams were visually interpreted and supported by semi-quantitative assessment of activity in bilateral using the skull as the reference site.The results of UCH patient and control groups were compared using two-sample and paired t tests.Pearson correlation analysis was also used.Results Affected condyle/parietal bone and affected condyle/bilateral condyles activity ratios (1.66 ±0.63 and 0.59 ±0.44) were significantly higher than those of the contralateral side (1.34 ±0.34 and 0.41 ±0.04 ; t =3.687 and 6.590,respectively,both P ＜ 0.01) and controls (1.12 ± 0.07 and 0.50 ± 0.01,t =6.459 and 4.750,respectively,both P ＜ 0.001).The sensitivity,specificity,positive and negative predictive values for the diagnosis of condylar hyperplasia were 95.2％ (20/21),60.0％ (6/10),83.3％ (20/24),and 6/7.The uptake on scintigraphy was not significantly related to the thickness of the cartilage (respective mean thicknesses of fibrous,proliferative,hypertrophic cartilage layers:(150.5 ± 94.9),(185.2 ±113.6),(167.7±76.9) μm,r=0.46,0.47,-0.12,all P＞0.05).Conclusion 99Tcm-MDPSPECT scintigraphy may be useful for assessment of growth activity of the mandibular condyle and to provide important information for condylar hyperplasia in surgical planning. Key words: Temporomandibular joint diseases; Mandibular condyle; Radionuclide imaging; MDP

Tomography of core-mantle boundary and lowermost mantle coupled by geodynamics

We propose an innovative approach to mapping CMB topography from seismic P-wave traveltime inversions: instead of treating mantle velocity and CMB topography as independent parameters, as has been done so far, we account for their coupling by mantle flow, as formulated by Forte & Peltier. This approach rests on the assumption that P data are sufficiently sensitive to thermal heterogeneity, and that compositional heterogeneity, albeit important in localized regions of the mantle (e.g. within the D″ region), is not sufficiently strong to govern the pattern of mantle-wide convection and hence the CMB topography. The resulting tomographic maps of CMB topography are physically sound, and they resolve the known discrepancy between images obtained from classic tomography on the basis of core-reflected and core-refracted seismic phases. Since the coefficients of mantle velocity structure are the only free parameters of the inversion, this joint tomography–geodynamics approach reduces the number of parameters; nevertheless the corresponding mantle models fit the seismic data as well as the purely seismic ones.