Evidence of crustal ‘channel flow’ in the eastern margin of Tibetan Plateau from MT measurements

Zhao, Guosong; Chen, Xiaobin; Wang, Lifeng; Wang, Jijun; Tang, Ji; Wan, ZhanSheng; Zhang, Jihong; Zhan, Yan; Xiao, Qibin

doi:10.1007/s11434-008-0081-3

Cited by 39 publications

(37 citation statements)

References 41 publications

(51 reference statements)

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“…On the basis of the electric structure derived from MT profiles crossing the LMSf, in conjunction with geologic and other geophysical studies [4,5,7,13,[15][16][17]20,22,31,[35][36][37][38][39][40][41][42][43][44][45], we have suggested that the HCL in the crust of the SGb of the eastern Tibetan Plateau is a layer of low viscosity that is susceptible to deformation or flow, commonly called "channel flow" [16,17,31,[35][36][37][38][39][40][41][42][43]. The existence of this layer is of great significance for studies of the deformation and dynamics of the eastern Tibetan Plateau.…”

Section: Hcl and Crustal Deformationmentioning

confidence: 99%

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Deep structure beneath the southwestern section of the Longmenshan fault zone and seimogenetic context of the 4.20 Lushan M S7.0 earthquake

et al. 2013

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Magnetotelluric measurements were carried out along two profiles across the middle and southwestern sections of the Longmenshan fault zone (LMSf) from 2009 to 2011, after the 2008 Wenchuan M W 7.9 earthquake. The former profile crosses the Wenchuan event epicenter and the latter one crosses 2013 Lushan M S 7.0 event epicenter. The data were analyzed using advanced processing techniques, including phase tensor and two-dimensional inversion methods, in order to obtain reliable 2-D profiles of the electrical structure in the vicinity of the two earthquakes. A comparison of the two profiles indicates both similarities and differences in the deep crustal structure of the LMSf. West of the southwestern section, a crustal high conductivity layer (HCL) is present at about 10 km depth below the Songpan-Garzê block; this is about 10 km shallower than that under the middle section of the LMSf. A high resistivity body (HRB) is observed beneath the southwestern section, extending from the near surface to the top of upper mantle. It has a smaller size than the HRB observed below the middle section. In the middle section, there is a local area of decreased resistivity within the HRB but there is absence of this area. The 2013 Lushan earthquake occurred close to the eastern boundary of HRB and the Shuangshi-Dachuan fault, of which the seismogenic context has both common and different features in comparison with the 2008 Wenchuan event. On a large scale, the 2013 Lushan earthquake is associated with the HCL and deformation in the crust including HCL of the eastern Tibetan Plateau. In order to assess seismic risk, it is important to consider both the stress state and the detailed crustal structure in different parts of the LMSf.

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Section: Hcl and Crustal Deformationmentioning

confidence: 99%

“…For both the 2008 and 2013 earthquakes, the details of earthquake occurrence and rupture depend on the structure and rheology of crust and lithospheric mantle beneath the LMSf and adjacent areas [16,17]. The LMSf lies on the southeastern boundary of the Songpan-Garzê block (SGb) of the eastern Tibetan Plateau.…”

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confidence: 99%

Deep structure beneath the southwestern section of the Longmenshan fault zone and seimogenetic context of the 4.20 Lushan M S7.0 earthquake

et al. 2013

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“…Together with GPS measurement data across the eastern margin of the Tibetan plateau [Shen et al, 2005;Gan et al, 2007], they suggest a slow convergence between the eastern Tibetan plateau and the Sichuan basin. As the eastward movement of the Tibetan plateau is obstructed by the strong lithosphere of the Sichuan basin, the crust of the Longmen Shan is significantly thickened [Zhao et al, 2008;Lou et al, 2009;Liu et al, 2009;Wang et al, 2009] and the mountain is greatly elevated. Although the occurrence of the Wenchuan Ms 8.0 earthquake is attributed to thrusting of the Longmen Shan fault belt, some questions remain unclear.…”

Section: Introductionmentioning

confidence: 99%

Seismic structure of the Longmen Shan region from S‐wave tomography and its relationship with the Wenchuan Ms 8.0 earthquake on 12 May 2008, southwestern China

Huang

et al. 2010

Geophysical Research Letters

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[1] Using arrival time data, we determined seismic structure of the Longmen Shan by S-wave tomography and studied its relations with the Ms 8.0 earthquake in Wenchuan, southwestern China. Our results suggest that the Longmen Shan fault belt is a rheologic boundary between the eastern Tibetan plateau and the Sichuan basin, and the deep crust of the entire Longmen Shan is significantly thickened by ductile deformation. The upper structure of the eastern Tibetan plateau is cored by the high-velocity Pengguan massif. Its collision with the Sichuan basin is the most direct reason for the seismic ruptures on the Longmen Shan fault belt north of Wenchuan, while the lack of earthquakes south of Wenchuan is related to the weakness of the crust. Therefore, The Ms 8.0 earthquake occurred in a strongly heterogeneous region. The variations in the crustal structure largely controlled the initial rupture of the Ms 8.0 earthquake and aftershock activity. Citation: Xu, Y., Z. Li, R. Huang, and Y. Xu (2010), Seismic structure of the Longmen Shan region from S-wave tomography and its relationship with the

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“…Within the middle-lower crusts at the eastern end, the low-density material crossed the weakened Panxi tectonic structure to reach the Daliangshan tectonic region. Zhao (2008) interpreted the MT data and postulated that the low-density, the high-conductivity material might be the channel flow of the middle-lower crusts.…”

Section: Apparent Density Structurementioning

confidence: 99%

“…The QTP's eastern margin is the focus of studies on eastward lateral extrusion of the former's crustal material (Tapponnier et al, 1982). Over the years, researchers have produced tomographic imaging results for the QTP's crust-mantle structure (Wang, 2007;Wu et al, 2009;Wang et al, 2005;Zhang et al, 2012), as well as geophysical detection results on a semi-molten, lowvelocity, and high-conductivity layer in the region's middle and lower crust (Sun et al, 2003;Zhao et al, 2008;Wang et al, 2009Wang et al, , 2013Wang et al, , 2014. With these results as the basis, Royden et al (1997) proposed a lower-crustal channel flow model to explain the rapid uplift movements at the QTP's eastern margin.…”

Section: Introductionmentioning

confidence: 99%

Deep physical structure and geotectonic implications of the eastern margin of the Qinghai–Tibet Plateau

Jun¹,

Wang²,

Qin³

et al. 2016

Earth sci. res. j.

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The eastern margin of the Qinghai-Tibet Plateau (QTP) is the focus of studies on eastward lateral extrusion of the latter's crustal material. This study aims to explore the structural response of the QTP's eastern crust-mantle to the extrusion, and the basis for the latter's geological structure. Data on the long-period magnetotelluric sounding of cross-tectonic units and Bouguer gravity were used to determine the physical structure of the crust-mantle at the plateau's eastern margin. The findings are as follows: (i) the apparent density structure indicates the large presence of a low-density material in the middle-lower crusts of the Songpan and Sichuan-Yunnan blocks at the QTP's eastern margin. On the other hand, the Yangtze cratonic block (Sichuan Basin) contains a material with a significantly higher density. To the west of the Longmenshan-Panxi tectonic zones, and along the lower crust at 40-50 km depth, is an obvious low-density zone aligned in a northeast-southwest orientation. (ii) The electrical structural model spanning Songpan block-Longmenshan tectonic zone-Yangtze block reveals three distinct electrical structural units along the cross-section bounded by the Longmenshan tectonic zone. The first is the Songpan block, which has high and low resistivity at the superficial layer and middle-lower crusts, respectively. Next is the Yangtze craton, which has a low and relatively higher resistivity at the superficial layer and middle-lower crusts, respectively. The third is the Longmenshan transitional tectonic zone, whose shallow layer and deep structure are characterized by an electrical structure with a thrust nappe towards the east, and a high-conductivity material extending to the lithospheric mantle, respectively. (iii) The apparent density and electrical structures indicate that the Panxi tectonic zone has a weakened structure in the lower crust; and (iv) physical properties of the QTP's deep structure show that its eastern margin may contain a middle-lower crustal fluid material with the attributes of high conductivity and low density. Its distribution is interrelated to the uplift mechanism and deep seismogenic activities at the QTP's eastern margin. El margen oriental del altiplano Qinghai-Tíbet (QTP, del inglés Qinghai-Tibet Plateau) es el área de la extrusión lateral hacia el Este de material cortical. Este trabajo se enfoca en explorar la respuesta estructural de las capas superiores en el altiplano y las bases para su estructuracón geológica. Se utilizó información magnetotelúria y anomalías de Bouguer para determinar la respuesta geofísica de las capas superiores en el margen occidental del altiplano. Dentro de los principales resultados se tiene: (i) la distribución de la densidad aparente indica la presencia de material de baja densidad en las capas medias y bajas de los bloques Songpan y Sichuan-Yunnan en el Este del QTP. Por otro lado, el bloque cratónico Yangtze (en la cuenca Sichuan) contiene material con una mayor densidad. Al oeste de las zonas tectónicas Longmeshan-Panxi, y a lo largo...

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Evidence of crustal ‘channel flow’ in the eastern margin of Tibetan Plateau from MT measurements

Cited by 39 publications

References 41 publications

Deep structure beneath the southwestern section of the Longmenshan fault zone and seimogenetic context of the 4.20 Lushan M S7.0 earthquake

Deep structure beneath the southwestern section of the Longmenshan fault zone and seimogenetic context of the 4.20 Lushan M S7.0 earthquake

Seismic structure of the Longmen Shan region from S‐wave tomography and its relationship with the Wenchuan Ms 8.0 earthquake on 12 May 2008, southwestern China

Deep physical structure and geotectonic implications of the eastern margin of the Qinghai–Tibet Plateau

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