Multiple-grid model parametrization for seismic tomography with application to the San Jacinto fault zone

Tong, Ping; Yang, Dinghui; Huang, Xueyuan

doi:10.1093/gji/ggz151

Cited by 38 publications

(54 citation statements)

References 51 publications

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“…In earthquake relocation

boldX

is a vector containing the hypocenter parameters, i.e., the origin time

t_{s}

and location coordinates

(r_{s}, θ_{s}, ϕ_{s})

of each regional earthquake, where s denotes the source index and r,

θ

and

ϕ

represent the depth, latitude and longitude, respectively. For both regional and teleseismic traveltime tomography,

boldX

Section: Methodsmentioning

confidence: 99%

“…For both regional and teleseismic traveltime tomography,

boldX

represents the relative model perturbations on discrete grid nodes (Tong et al., 2019). The sensitivity matrix A can be computed when the ray paths of the P‐waves are available (Rawlinson et al., 2010; Tong et al., 2019; Zhao et al., 1992). To trace the ray paths emitted from one earthquake, we first compute the traveltime field in a 3‐D velocity model by solving the eikonal equation (Rawlinson & Sambridge, 2005; Sethian & Popovici, 1999).…”

Section: Methodsmentioning

confidence: 99%

“…In this section, we discuss the results of checkerboard tests to assess the imaging resolution. A grid approach is used to parameterize the model space (Jiang et al., 2009; Tong et al., 2019). The grid spacing in the horizontal direction is approximately 1.2°, while the nodes of the inversion grid in the vertical direction are located at depths of 15, 60, 120, 200, 300, 450, 600 and 800 km.…”

Section: Checkerboard Resolution Testmentioning

confidence: 99%

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The Geometry of the Subducted Slab Beneath Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

Liu

Suardi

Xu³

et al. 2021

JGR Solid Earth

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Sumatra is located on the western margin of Sundaland (Figure 1). According to plate reconstruction, Sumatra has been situated at its current location since the Late Jurassic (Hall, 2012). With the closure of the Neotethys Ocean, the intra-oceanic Woyla Arc accreted onto the western margin of Sundaland, forming present-day Sumatra (Advokaat et al., 2018; Hall, 2012, 2015) during the Late Cretaceous. Subduction beneath Sumatra was minimal from the Late Cretaceous to the Early Eocene, and Australia remained close to Antarctica during this period (Hall, 2012). Based on magnetic and deep-sea drilling data, the subduction of the Indo-Australian plate beneath Sumatra commenced at about 45 Ma when Australia separated from Antarctica (Hall, 2012). At that time, oblique subduction began in the Sumatra subduction zone (Beaudry & Moore, 1985; Sclater & Fisher, 1974). Studies on the deposition of sediment offshore of northern Sumatra and in the vicinity of the Sunda Strait indicate that rapid subduction may have begun in the early Miocene (∼20 Ma) (Beaudry & Moore, 1985; Malod et al., 1995). The convergence rate may have peaked in the Pliocene, as was inferred from the intense andesitic volcanism during that period; a high rate of convergence has characterized this subduction zone ever since (Hochstein & Sudarman, 1993). At present, the rate of oblique convergence in the Sumatra subduction zone is approximately 7.2 mm/yr in the south and decreases to 5.2 mm/yr in the north (Figure 1) (Sieh & Natawidjaja, 2000). Moreover, unlike the oblique subduction at the Sumatra trench, the subduction occurring in western Java is normal to the trench axis (Figure 1); consequently, there is an abrupt transition from normal subduction to oblique subduction at the Sunda Strait (Malod et al., 1995). As pointed out by Malod et al. (1995), this abrupt transition is governed by the convergence motion of the Indo-Australian and Southeast Asian plates.

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“…In earthquake relocation

boldX

is a vector containing the hypocenter parameters, i.e., the origin time

t_{s}

and location coordinates

(r_{s}, θ_{s}, ϕ_{s})

of each regional earthquake, where s denotes the source index and r,

θ

and

ϕ

represent the depth, latitude and longitude, respectively. For both regional and teleseismic traveltime tomography,

boldX

Section: Methodsmentioning

confidence: 99%

“…For both regional and teleseismic traveltime tomography,

boldX

Section: Methodsmentioning

confidence: 99%

Section: Checkerboard Resolution Testmentioning

confidence: 99%

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The Geometry of the Subducted Slab Beneath Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

Liu

Suardi

Xu³

et al. 2021

JGR Solid Earth

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“…The entropy‐satisfying FMM algorithm, which combines upwind schemes with a fast sorting technique (Hassouna & Farag, ), can calculate the first arrivals in strong heterogeneous media with high accuracy (Rawlinson et al, ; Rawlinson & Sambridge, ). Considering that the derivatives

\frac{\partial normalΔ T_{ij}}{\partial r_{i}}

\frac{\partial normalΔ T_{ij}}{\partial θ_{i}}

\frac{\partial normalΔ T_{ij}}{\partial ϕ_{i}}

, and

\frac{\partial normalΔ T_{ij}}{\partial t_{i}}

have different units, the gradient of the traveltime difference Δ T ij were nondimensionalized by changing

\frac{\cos α}{v}

\frac{r \cos β}{v}

\frac{r \sin θ \cos γ}{v}

, and −1 to

\frac{D \cos α}{vT}

\frac{r \cos β}{vT}

\frac{r \sin θ \cos γ}{vT}

, and

- \frac{D}{vT}

, respectively (Tong et al, ). In this study, D and T are set to be 1,000 km and 1 s, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…It is obvious that the debate on the morphology of the slab beneath northern Sumatra is still ongoing. To resolve this dispute, we apply an eikonal equation‐based traveltime tomography method (Liu et al, ; Tong et al, ) to image the crust and mantle structure beneath northern Sumatra by inverting high‐quality regional and teleseismic traveltime data from the Agency for Meteorology, Climatology and Geophysics of Indonesia (BMKG). After relocating the regional earthquakes in an initial 3‐D model, the regional data are utilized to image the structures of the crust and uppermost mantle.…”

Section: Introductionmentioning

confidence: 99%

Slab Morphology Beneath Northern Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

et al. 2019

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An eikonal equation-based tomography method is used to invert the high-quality regional and teleseismic traveltime data recorded by 26 broadband seismic stations in northern Sumatra, following which we obtain the P and S wave velocity structures of the crust and mantle down to a depth of 800 km. The results of both P and S wave tomography clearly show that the Indo-Australian oceanic plate continuously penetrates downward beneath northern Sumatra and the maximum penetration depth varies approximately from 400 km at the northern tip of Sumatra to about 800 km around the southern boundary of our study area. Significant slab folding or bending reported in the literature as the main feature of the subducted slab beneath northern Sumatra is not found in our results. Instead, our tomographic images demonstrate only a less curved slab that mimics the shape of the Sunda Trench and volcanic arc and generally extends over depths from 120 to 450 km. P wave tomography shows broad and pronounced low-velocity anomalies beneath the island of Sumatra in the lower crust and uppermost mantle. Our model also reveals a slab tear approximately at 120-km depth, which has been documented in previous studies and considered to be related to the eruption of the Toba supervolcano.

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Choosing optimal model parameterization for improving the accuracy of refraction seismic tomography

Chernyshov

Duchkov

Koulakov

2022

Near Surface Geophysics

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Seismic ray tomography is a popular tool for reconstructing seismic velocity models from traveltime data. Here we study how the model parameterization affects the resolution and accuracy of the tomographic inversion for the near-surface model building. In particular, we consider the weighting of the elements of the model perturbation vector based on the values of the initial velocity model. When the model parameters are defined in terms of velocities, then the tomographic-inversion resolution is better for the shallow part but degrades for the deeper part of the model. The opposite is true when the model parameters are defined in terms of slowness values. This effect is associated with the method of forming the tomographic matrix. When linearizing the tomography problem for different model parameters, the matrix elements have different weight coefficients. This affects the inversion results and can lead to large errors. We suggest a new parameterization (in-between the velocity and the slowness) that provides better quality of the tomographic inversion and balanced resolution between the shallow and deeper part of the model. The good performance of this new parameterization is confirmed by a series of synthetic tests and one real-data example.

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Multiple-grid model parametrization for seismic tomography with application to the San Jacinto fault zone

Cited by 38 publications

References 51 publications

The Geometry of the Subducted Slab Beneath Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

The Geometry of the Subducted Slab Beneath Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

Slab Morphology Beneath Northern Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

Choosing optimal model parameterization for improving the accuracy of refraction seismic tomography

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