Time‐evolving seismic tomography: The method and its application to the 1989 Loma Prieta and 2014 South Napa earthquake area, California

Tong, Ping; Yang, Dinghui; Li, Dongzhuo; Liu, Qinya

doi:10.1002/2017gl072785

Cited by 23 publications

(27 citation statements)

References 38 publications

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“…Travel paths of seismic body waves in complex media can be efficiently and accurately determined by numerically solving the Eikonal equation, which is essential for the robustness of ray‐based seismic tomography methods (Liu et al., 2018; Rawlinson et al., 2010; Tong et al., 2017). In the present Eikonal equation‐based seismic anisotropic tomography study, first, an initial isotropic layered model that honors the Moho geometry is constructed by inverting all the picked P‐wave arrival times in the study area.…”

Section: Methodsmentioning

confidence: 99%

Crustal Rotation and Fluids: Factors for the 2019 Ridgecrest Earthquake Sequence?

Tong

Yao

Liu

et al. 2021

Geophysical Research Letters

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P‐wave azimuthal anisotropic tomography reveals that the July 6, 2019 Mw 7.1 Ridgecrest earthquake occurred in a region with clockwise crustal rotation. The rotation together with the sinistral slip on the Garlock Fault is a response to the northwest‐trending, dextral shear within the Eastern California Shear Zone due to the relative motion between the Pacific and North America Plates. The hypocentral area of the Ridgecrest mainshock is characterized by a sharp lateral velocity contrast which has a reversal in contrast polarity at about 5 km depth. We find high Vp/Vs ratio structures covering the rupture zones of the Mw 6.4 foreshock and the Mw 7.1 mainshock, which may indicate the existence of fluids in the fault zones. We speculate that fluids and crustal rotation may have played important mechanical roles in causing the 2019 Ridgecrest earthquake sequence.

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Section: Methodsmentioning

confidence: 99%

Crustal Rotation and Fluids: Factors for the 2019 Ridgecrest Earthquake Sequence?

Tong

Yao

Liu

et al. 2021

Geophysical Research Letters

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“…In each iteration, we adjust the damping factor

η

to restrict the maximal relative location/velocity perturbation below a prescribed value (such as 1%). The essential rule of this strategy (establishing a prescribed value) is to steadily evolve the model toward the final optimal model (Liu et al., 2018; Tong et al., 2017). To determine the optimal prescribed value, we conduct a series of tomographic inversions with different prescribed values.…”

Section: Methodsmentioning

confidence: 99%

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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“…(b1)-(b4) are the results of the adjoint-state traveltime tomography (ATT) method. Tomographic images in (c1)-(c4) are produced by the eikonal ray-based traveltime tomography method(Tong et al, 2017(Tong et al, , 2019. (d1)-(d4) are extracted from the SCEC Community Velocity Model (CVM-H 15.1.0)(Shaw et al, 2015).…”

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confidence: 99%

Adjoint‐State Traveltime Tomography: Eikonal Equation‐Based Methods and Application to the Anza Area in Southern California

Tong

2021

JGR Solid Earth

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Seismic traveltime tomography is one of the primary and routine techniques to estimate subsurface material properties. It has been contributing significantly to the understanding of heterogeneous structures and dynamic processes in the Earth's interior ever since the pioneer work of Aki and Lee (1976). Various seismic traveltime tomography methods are rooted in different mathematical physical models. In principle, we can categorize them into three major types: Ray-based traveltime tomography, wave equation-based traveltime tomography, and eikonal equation-based traveltime tomography.Ray tracing is the key ingredient for seismic traveltime tomography methods based on ray theory (e.g., Aki & Lee, 1976;Thurber, 1983;Zhao et al., 1992). During the past few decades, plenty of seismic ray tracing techniques have been developed, including the widely used two-point ray tracing methods (e.g.,

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Time‐evolving seismic tomography: The method and its application to the 1989 Loma Prieta and 2014 South Napa earthquake area, California

Cited by 23 publications

References 38 publications

Crustal Rotation and Fluids: Factors for the 2019 Ridgecrest Earthquake Sequence?

Crustal Rotation and Fluids: Factors for the 2019 Ridgecrest Earthquake Sequence?

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

Adjoint‐State Traveltime Tomography: Eikonal Equation‐Based Methods and Application to the Anza Area in Southern California

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