A fast algorithm for two-point seismic ray tracing

Um, Junho; Thurber, Clifford H.

doi:10.1785/bssa0770030972

Cited by 768 publications

(86 citation statements)

References 6 publications

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“…It is more reliable to invert for Vp and Vp/Vs than Vp and Vs separately when there are fewer high-quality S-arrivals (Eberhart-Phillips, 1986). The procedure starts from determining the calculated arrival times using trial hypocenters, origin times, an initial model of the seismic velocity structure, and the pseudo-bending technique of Um and Thurber (1987) for the ray tracing (Supplementary Figure S2). The residuals between observed and calculated arrival times can be related to perturbations to the velocity structure parameters that are iteratively performed in order to minimize the weighted root-mean-square (RMS) misfit.…”

Section: Methodsmentioning

confidence: 99%

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

et al. 2022

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The Central and East Java region, which is part of the Sunda Arc, has an important role in producing destructive earthquakes and volcanic complexes in Indonesia as a result of the convergence between the Indo-Australian plate that subducts under the Eurasian plate. In this study, the 3-D seismic velocity structure (Vp, Vs, and Vp/Vs) of the crust and upper mantle was determined to reveal the presence of the subducted slab, volcanic sources, and seismogenic features in the Central and East Java region. We have manually re-picked P- and S-arrivals of 1,488 events from January 2009 to September 2017 recorded at 27 stations of the BMKG network. An iterative damped least-squares inversion method was applied to simultaneously calculate both hypocenter relocations and velocity structure beneath this high-risk region to a depth of 200 km. We then compare the tomographic results and seismicity to interpret structural features in the seismic zones. The subducted slab is dipping toward the north, imaged by the high-velocity regions with low Vp/Vs at depths of about 50–100 km. Low-velocity anomalies with high Vp/Vs above the slab at a depth of ∼100 km, imply the possible location of partial melting from slab dehydration. Fluids and melts are ascending to feed the volcanoes i. e., Merapi-Merbabu, Wilis, Pandan, Semeru, Bromo, and Ijen that also have similar low-velocity anomalies at 10–30 km depths, suggesting the presence of the sedimentary basin or magma reservoir. We also have redetermined the hypocenter location of the 2021 (Mw 6.1) Malang earthquake at 8.94oS, 112.45oE, with a depth of 59.7 km. The location error in the x, y, and z directions are 3.08, 6.39, and 11.91 km, respectively. This intraslab event with a thrusting mechanism is located in the high-velocity region and close to the intermediate-depth seismic clusters, which indicates the geometry of the oceanic slab. In the region of 1994 (Mw 7.8) Banyuwangi earthquake, we found a low-velocity anomaly at ∼ 50 km depth that might be associated with the presence of subducting seamount that is more hydrated than the surrounding slab. The slip over this subducting seamount caused the tsunamigenic earthquake.

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Section: Methodsmentioning

confidence: 99%

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

et al. 2022

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“…We applied seismic travel time data for tomography inversion by local tomography software [33]. The local tomography software was modified according to the bending-ray tracing algorithm by [34]. First, we utilized the Goal function [35] to detect the initial locations of the earthquakes.…”

Section: Methodsmentioning

confidence: 99%

Exploring the Rheology of a Seismogenic Zone by Applying Seismic Variation

et al. 2021

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Although the study of spatiotemporal variation of a subsurface velocity structure is a challenging task, it can provide a description of the fault geometry as well as important information on the rheological changes caused by fault rupture. Our main objective is to investigate whether rheological changes of faults can be associated with the seismogenic process before a strong earthquake. For this purpose, a 3D tomographic technique is applied to obtain P- and S-wave velocity structures in central Taiwan using travel time data. The results show that temporal variations in the Vs structure in the source area demonstrate significant spatiotemporal variation before and after the Chi-Chi earthquake. We infer that, before the mainshock, Vs began to decrease (and Vp/Vs increased) at the hanging wall of the Chelungpu fault, which may be induced by the increasing density of microcracks and fluid. However, in the vicinity of the Chi-Chi earthquake’s source area, Vs increased (and Vp/Vs decreased), which may be attributed to the closing of cracks or migration of fluid. The different physical characteristics at the junctional zone may easily generate strong earthquakes. Therefore, seismic velocity changes are found to be associated with a subsurface evolution around the source area in Taiwan. Our findings suggest that monitoring the Vp and Vs (or Vp/Vs) structures in high seismic potential zones is an important ongoing task, which may minimize the damage caused by future large earthquakes.

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“…An alternative class of methods for two-point ray tracing is those based on ray bending. These kinds of approaches follow directly the Fermat's principle, and are based on fixing the two end points of the ray at the required emission and reception points, and perturbing the ray trajectory until the acoustic length along the ray becomes stationary under these perturbations [44,45,47]. In this study, we use the former approach, ray-linking, and calculate the ray path between each pair of emitters and receivers by solving the inverse problem of finding the initial ray direction given the reception point through successive implementations of the ray-tracing algorithm.…”

Section: 41mentioning

confidence: 99%

“…In the bending method, the problem is framed as a two-point boundary value problem. By fixing both end-points of the ray, its trajectory is iteratively computed until the perturbation in the path becomes smaller than a tolerance [48,57,49,41,44,42,47]. In [48] and [57], central finite difference approaches were used for solving a second-order differential equation derived from an Euler Lagrange equation describing the trajectory of the rays (see Sec.…”

Section: Introductionmentioning

confidence: 99%

Refraction-corrected ray-based inversion for three-dimensional ultrasound tomography of the breast

Javaherian

Lucka²,

Cox³

2020

Preprint

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Ultrasound Tomography has seen a revival of interest in the past decade, especially for breast imaging, due to improvements in both ultrasound and computing hardware. In particular, three-dimensional ultrasound tomography, a fully tomographic method in which the medium to be imaged is surrounded by ultrasound transducers, has become feasible. This has led to renewed attention on ultrasound tomography image reconstruction algorithms. In this paper, a comprehensive derivation and study of a robust framework for large-scale bent-ray ultrasound tomography in 3D for a hemispherical detector array is presented. Two ray-tracing approaches are derived and compared. More significantly, the problem of linking the rays between emitters and receivers, which is challenging in 3D due to the high number of degrees of freedom for the trajectory of rays, is analysed both as a minimisation and as a root-finding problem. The ray-linking problem is parameterised for a convex detection surface and three robust, accurate, and efficient ray-linking algorithms are formulated and demonstrated. To stabilise these methods, novel adaptive-smoothing approaches are proposed that control the conditioning of the update matrices to ensure accurate linking. The nonlinear UST problem of estimating the sound speed was recast as a series of linearised subproblems, each solved using the above algorithms and within a steepest descent scheme. The whole imaging algorithm was demonstrated to be robust and accurate on realistic data simulated using a full-wave acoustic model and an anatomical breast phantom, and incorporating the errors due to time-of-flight picking that would be present with measured data. This method can used to provide a low-artefact, quantitatively accurate, 3D sound speed maps. In addition to being useful in their own right, such 3D sound speed maps can be used to initialise full-wave inversion methods, or as an input to photoacoustic tomography reconstructions.

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A fast algorithm for two-point seismic ray tracing

Cited by 768 publications

References 6 publications

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

Exploring the Rheology of a Seismogenic Zone by Applying Seismic Variation

Refraction-corrected ray-based inversion for three-dimensional ultrasound tomography of the breast

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