Crustal Anisotropy in North Taiwan from Shear‐Wave Splitting

Ling-xue, Tai; Gao, Yuan; Fong, Kuo; Lee, En‐Tzu; Shi, Yaolin; Lin, Hsin‐I

doi:10.1002/cjg2.1646

Cited by 9 publications

(11 citation statements)

References 18 publications

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“…In the northeastern study area, the crustal anisotropy of the southern SCB at 4-20 s periods is dominated by NE-SW and NEE-SWW trends (Figure 8C), which is consistent with the NE-SW trend of the surface eastern Sichuan fold belt Xiong et al, 2016). The shear wave splitting of local earthquakes (Tai et al, 2015), Pms anisotropy (Sun et al, 2012), and S-wave azimuthal anisotropy (Zhu et al, 2021) also show the same crustal anisotropy characteristics. Since the Cenozoic, the eastward compressive stress of the TP may have been transmitted to the eastern Sichuan fold belt through the hard SCB, leading to an uplift of the east Sichuan fold belt (1-2 mm/ a) in this area (Shi et al, 2016;Yuan et al, 2018).…”

Section: Constraints On the Western Boundary Between Yangtze Block An...supporting

confidence: 64%

Characteristics of azimuthal anisotropy in SE Tibetan plateau and its relationship with the background of block structure

Liu

Fang

et al. 2023

Front. Earth Sci.

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The southeastern Tibetan Plateau, which includes the Tibetan Plateau, Yangtze Block, and Cathaysia Block, is geotectonically situated in the compound part of the Tethys-Himalayan tectonic domain and the Peninsular Pacific tectonic domain. It is one of the critical regions for studying the scientific problems of plateau material lateral escape, lithosphere deformation, geotectonic properties of blocks, and deep dynamics. In this study, we use ambient noise data recorded by 401 broadband stations to obtain high-resolution short-period (T = 4–32 s) Rayleigh wave azimuthally anisotropic phase velocity maps. These could provide fresh clues for an in-depth understanding of the crust-mantle velocity structure, deformation mechanism, and geotectonic evolution in the southeastern Tibetan Plateau. Within the Simao block, the strikes of the faults and the orientations of the principal compressive stress of the stress field both generally coincide with the fast-wave polarization direction (FPD). The FPD near the Lancangjiang fault zone in the west is in the NE-SW direction, near the Wuliangshan fault zone in the center is near the NS direction, and near the Red River fault zone in the east is the NW-SE direction. We estimate that the compressive stress in the southwest direction of the Tibetan Plateau material has a controlling effect on the crustal deformation of the Simao block, which is likewise blocked by the Lincang granite belt, resulting in strong tectonic deformation. The FPD of the crust in the middle Red River fault zone is NS direction, significantly different from the fault strike. Combining with the seismic activity and GPS results, the depth of 8 km below the surface of the middle Red River fault is completely locked, and we conclude that the anisotropy of the upper crust of the middle part of the Red River fault zone is related to the action of the regional tectonic stress field. Taking into account geochemical and thermochemical results, we speculate that the complex tectonic stress at the junction of the blocks leads to prominent regional characteristics of the FPDs of azimuthal anisotropy in the crust, suggesting that the Shizong-Mile fault zone may be the western boundary between the Yangtze block and the Cathaysia block.

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Section: Constraints On the Western Boundary Between Yangtze Block An...supporting

confidence: 64%

Characteristics of azimuthal anisotropy in SE Tibetan plateau and its relationship with the background of block structure

Liu

Fang

et al. 2023

Front. Earth Sci.

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“…Several recent studies have identified crustal seismic anisotropy across Taiwan due to stress-induced fractures and material fabrics associated with this convergence. Regional stress anisotropy has been inferred using local shear wave splitting [Liu et al, 2004;Tai et al, 2011], surface waves [Lai et al, 2009], and teleseismic shear waves [Huang et al, 2006;Kuo-Chen et al, 2009]. Vertical coherence of mantle and crustal deformation have been interpreted by Rau et al [2000] using teleseismic shear waves and by Kuo-Chen et al [2013] using regional earthquake P waves.…”

Section: Introductionmentioning

confidence: 99%

Terrane‐controlled crustal shear wave splitting in Taiwan

Okaya

Christensen

Ross

et al. 2016

Geophysical Research Letters

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Taiwan is the result of arc‐continent collision associated with the convergence of the Philippine Sea plate with the eastern Eurasian plate continental margin. The locus of deformation is found in eastern Taiwan in the form of mountain building (Central Range) with underlying thickened lithosphere. Rapid tectonic exhumation in the Central Range has uncovered low‐to‐high‐grade metamorphic rocks marked by steep cleavage. We carried out a crustal seismic anisotropy study across Taiwan, producing a database of over 27,000 local earthquake shear wave splitting measurements. Additionally, we carried out rock physics measurements of metamorphic outcrop samples to quantify shear wave rock anisotropy. We produced a map of station‐averaged splitting measurements across Taiwan. Patterns of fast shear wave directions correlate with tectonic terranes produced by plate convergence. Deformation‐related mineral‐preferred orientation in the metamorphic rocks produces a significant amount of the crustal anisotropy in the Taiwan collision zone.

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“…Such interactions have been described by the Anisotropic Poro-Elasticity (APE) model [Crampin and Zatsepin, 1997;Zatsepin and Crampin, 1997]. Nevertheless, deviations from this model are common, with high 𝜑 scattering being attributed to topographic irregularities [Tai et al, 2011], complex tectonics and structures [Kaviris et al, 2021], fluid pathways [Kaviris et al, 2020] and inherent rock fabric [Valcke et al, 2006]. The control of structures over splitting features is also common in interpreting shear-wave splitting, either as the sole cause or by assessing its interplay with the regional stress field [Cochran et al, 2003[Cochran et al, , 2006Peng and Ben-Zion, 2004;Gao et al, 2019;Kaviris et al, 2021;Ortega-Romo et al, 2021].…”

Section: Discussionmentioning

confidence: 99%

Shear-wave splitting perspectives from the intense aftershock sequence of Damasi – Tyrnavos

Κaviris

2023

Annals of Geophysics

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The area of Damasi-Tyrnavos (Thessaloniki, Central Greece), in the vicinity of Larissa, was characterized by low seismic activity during the last decades. Two strong earthquakes of Mw = 6.3 and Mw = 6.0 The area of Damasi – Tyrnavos (Thessaly, Central Greece), in the vicinity of Larissa, was characterized occurred in early March 2021, followed by an intense aftershock sequence, related to WNW-ESE to NW-SE oriented faulting. This sequence was recorded by a dense local seismological network that provided a rich dataset and a unique opportunity to investigate upper crust shear-wave splitting for the first time in the study area. A fully automated technique, employing the eigenvalues method and cluster analysis, was implemented to measure the fast shear-wave polarization direction and the time-delay between the two split-shear-waves. This procedure yielded 655 results of adequate quality grade at 9 stations, after analyzing 1602 events and applying strict selection criteria, including the shear-wave window. The measured directions revealed a complex upper crust anisotropic regime. WNW-ESE to NW-SE, in accordance both with the APE model, being parallel to the local 𝜎 Hmax direction, and the strike of the fault planes. On the other hand, stations at the central part exhibit NNW-SSE and NNE-SSW anisotropy directions. An interesting feature is that the two northern stations are characterized by larger normalized time-delay values, possibly related to the migration of seismicity to the north during the initial stage of the seismic sequence.

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Crustal Anisotropy in North Taiwan from Shear‐Wave Splitting

Cited by 9 publications

References 18 publications

Characteristics of azimuthal anisotropy in SE Tibetan plateau and its relationship with the background of block structure

Characteristics of azimuthal anisotropy in SE Tibetan plateau and its relationship with the background of block structure

Terrane‐controlled crustal shear wave splitting in Taiwan

Shear-wave splitting perspectives from the intense aftershock sequence of Damasi – Tyrnavos

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