Longmenshan Fault Research Articles

Postseismic Deformation of the 2008 Wenchuan Earthquake Illuminates Lithospheric Rheological Structure and Dynamics of Eastern Tibet

AbstractTectonic research of the Tibetan Plateau has long focused on its deformation style and mechanisms. The 2008 Mw7.9 Wenchuan earthquake ruptured the Longmen Shan fault located at the eastern rim of the plateau and excited a viscoelastic response of the lithosphere. We infer a three‐dimensional (3D) rheological structure of eastern Tibet from modeling nine years of postseismic displacements observed by GPS. Our solution provides tight constraints on the lower‐crustal and upper‐mantle steady‐state viscosities of the Songpan‐Ganzi Terrane as (5.0 ± 0.7) × 1018 and (1.3 ± 0.3) × 1019 Pa s, respectively, consistent with a “jelly sandwich” model of Tibet, but not with some crustal channel flow models featuring much lower viscosities. The inferred lower‐crustal and upper‐mantle transient viscosities are (5.0 ± 1.3) × 1017 and (5.0 ± 1.5) × 1018 Pa s, respectively, suggesting nonlinear deformation mechanisms. The adjacent West Qinling and Sichuan blocks feature an order‐of‐magnitude higher rheological strength, which is consistent with the changes in the crustal material properties and interseismic deformation style across the East Kunlun‐Tazang and Longmen Shan faults. Our results enable us to propose a conceptual 3D tectonic deformation model, in which the eastward extrusion of Tibet is absorbed in the Songpan‐Ganzi crust mainly by E‐W shortening and N‐S extension, accommodated through faulting of conjugate strike‐slip faults in the upper crust and distributed shear in the lower crust.

Space-time evolution of Longmenshan fault coupling and moment deficit inverted by multi-source geodetic data

Space-time evolution of Longmenshan fault coupling and moment deficit inverted by multi-source geodetic data

Stress changes associated with the significant first subevent of the 2008 Wenchuan earthquake and implications for the rupture behavior transition

The rupture process of the Wenchuan earthquake demonstrated a transition from thrust-dominated slip to northeastward strike-slip motion along the Longmen Shan Fault Zone. The initial stress has been reported as playing a critical role in this process; however, the stress changes, especially those caused by the significant first subevent of the Wenchuan earthquake are not well understood. Here, we employ a three-dimensional finite element model of the Sichuan-Yunnan region to analyze the stress change caused by the significant first subevent and explore the possible influence on the following ruptures. The results indicate that the auxiliary maximum principal compressive stress (SH) associated with the significant first subevent was horizontal and that the auxiliary stress regime was SH>Sh>Sv, supporting the ongoing regional thrust motion near the southwestern segment of the rupture plane. However, in the northeastern segment, the auxiliary stress regime transitioned to SH>Sv>Sh, demonstrating that the stress changes promoted the transition of the rupture behavior from predominantly thrust motion in the southwest to right-lateral strike-slip motion in the northeastern segment, which was also supported by the dominant shear stress change and the subtle normal stress change along the fault plane in the northeastern segment. In addition, our modeled results also indicate that the orientation of the maximum principal compressive stress changed from SEE to northeastward NEE along the strike of Longmen Shan Fault Zone. This anticlockwise rotation hastened the rupture behavior transition, suggesting that both the initial stress and the stress changes associated with the first subevent jointly controlled the following northeastward rupture of the Mw7.9 Wenchuan earthquake.

Fluid geochemistry and its implications on the role of deep faults in the genesis of high temperature systems in the eastern edge of the Qinghai Tibet Plateau

Deep faults could provide fluent channels for geothermal water uplift so that it is one of the targets for high-temperature hydrothermal exploration in orogenic geothermal belt. In the eastern edge of the Qinghai Tibet Plateau, significant geothermal potential reflected by hot springs, fumaroles, and sinters, are indeed exposed along a series of lithospheric-scale faults, including the Jinshajiang, the Ganzi-Litang and the Xianshuihe faults. However, as the controlling fault of the eastern edge of the plateau, the Longmenshan Fault has few geothermal manifestations. In order to uncover the role of deep faults in the genesis of high-temperature geothermal systems, a comprehensive chemical and isotopic comparison of geothermal fluid between the Xianshuihe-Anninghe Fault and the Longmenshan-Minjiang Fault was investigated in this paper. According to FixAl modeling and cation geothermometric calculations, the reservoir temperatures of geothermal systems along the Longmenshan Fault are lower than 150 °C with circulation depth of geothermal water less than 4 km while those in the Xianshuihe Fault reaches up to 260 °C with geothermal water circulating as deep as 8 km. Compared to the Xianshuihe Fault, the low reservoir temperatures along the Longmenshan Fault are accompanied by two characteristics of geothermal fluid: (1) no distinctive oxygen shift occurs in stable isotopes of geothermal waters; and (2) little mantle-derived volatiles found in the gaseous components. We propose that, extensional fracture systems are locally formed in the strike-slip movement of the Xianshuihe and Anninghe faults, which not only act as conduits for deep-derived geothermal volatiles, such as metamorphic carbon dioxide and mantle helium, but also enhance the heat convection processes, resulting in the formation of high-temperature geothermal systems. In contrast, in the Longmenshan Thrust Fault, the shallow circulation of geothermal water in closed fracture systems accounts for its lower reservoir temperatures. Therefore, deep extensional fault is a crucial element in forming a high-temperature geothermal system in the eastern edge of the Qinghai Tibet Plateau.

Seismic velocity variations over four years (2013 - 2016) along the Longmenshan faults in Sichuan, China

Seismic velocity variations over four years (2013 - 2016) along the Longmenshan faults in Sichuan, China

An anti-fault study of basalt fiber reinforced concrete in tunnels crossing a stick-slip fault

Crossing active faults has proven to cause significant damage in tunnels. In this study, a large–scale plate thrust model stimulating the LongMenShan Fault (LMSF) dislocation was established numerically. The characteristic dislocation curve of the fault generated at the stick-slip incidence was derived. Furthermore, a soil-structure FE model was established with a tunnel structure crossing the LMSF Zone, in which the hanging wall and footwall moved according to the abovementioned dislocation curve. To cope with the serious damage of tunnel caused by fault dislocation, the articulated design was adopted. For discovering an appropriate material to construct the articulated sections and enhance the flexibility of tunnel structure, basalt fiber reinforced concrete (BFRC) was studied by SEM test and mechanical tests. The results showed that basalt fiber could increase the tensile capacity and tenacity of concrete and the 0.5% BFRC was selected as the optimal fiber volume content. By applying the 0.5% BFRC articulated design, the length and width of tunnel cracks generated by fault dislocation decreased by 33.45% and 38.11%, respectively. This study could serve as a reference in the design of fault-crossing tunnel projects.

Present-day movement trends of the major tectonic faults in the Sichuan-Yunnan region based on the constraint of GPS velocity fields

Based on the known fault distribution in Sichuan-Yunnan region (SYR), a rigid Euler rotation model is constructed by using GPS velocities (1998 ~ 2016) after excluding the stations near the fault boundaries and simultaneously a translation-rotation-strain model is constructed by using almost all GPS velocities to calculate three periods strain rate fields (2008.6 ~ 2010.4, 2010.5 ~ 2013.4 and 2013.5 ~ 2016.12) after Wenchuan earthquake. The results show that: (1) the strike-slip activity is the most common trends for the regional faults. The Xianshuihe-Xiaojiang fault, the Lancangjiang-Weixi-Weishan-Wuliangshan fault and the Longmenshan fault are the most active in the whole SYR, and the dislocation rate is more than 15 mm/a, and the trend of activity gradually decreases from the northwest to the southeast. (2) The different activity rates of the faults in the study area indicate that some of the eastward extrusion of the Tibet Plateau is absorbed and adjusted by the inside faults, and it is not a few large strike-slip faults. (3) Through the analysis of three periods’ grid velocity fields, we found that the movement rates of the Bitu section of Lanchangjiang fault, the Northwestern section of Weixi-Weishan fault and the Nujiang fault after Wenchuan earthquake are larger than that after Yushu and Ya’an earthquake, and the difference is about 8 mm/a. Besides, the activity rate of Northwestern section of Longmenshan fault after the Wenchuan earthquake is larger than that after the Ya’an earthquake, although the two epicentres distances are relatively close. (4) The strain rate fields and surface expansion rates show that the high value area is mainly distributed at or around the intersection among some fault zones and its surroundings, and the maximum area is mainly located at some long and deep fault zones such as the Longriba fault, the Longmenshan fault zone, the Ganzi-Yushu fault and the Xianshuihe, and the magnitude is about 35 ~ 50 nanstrain/a. The research should provide fundamental material for the study of crustal stress variation and earthquake prediction in Sichuan-Yunnan region.

GNSS for Quasi-Real-Time Earthquake Source Determination in Eastern Tibet: A Prototype System toward Early Warning Applications

AbstractActive crustal deformation of the Tibetan plateau results in destructive continental earthquakes and is therefore the focus of intense research interest. Increases in the numbers of Global Navigation Satellite System (GNSS) networks and stations deployed in Tibet are allowing for the characterization of crustal deformation during different phases of the earthquake cycle. Here, we present the status of a “seismic + high-rate GNSS” network deployed in eastern Tibet, including its data streams and data processing system, with the goal of supporting quasi-real-time earthquake source determination. Furthermore, we use this network to test a prototype earthquake early warning (EEW) system using data from the 2008 Mw 7.9 Wenchuan earthquake, the 2011 Mw 9.0 Tohoku earthquake, and 2200 synthetic earthquakes with moment magnitudes ranging from 6.5 to 7.5 on the southern Longmen Shan fault and Anninghe fault. The results show that our current methodology could respond to moderate-to-large earthquakes (magnitude 7+) within tens of seconds after the origin time, with implications for EEW applications in China.

GPS time series inversion of the healing process of the middle segment of the Longmenshan fault after the 2008 Wenchuan earthquake

GPS time series inversion of the healing process of the middle segment of the Longmenshan fault after the 2008 Wenchuan earthquake

Discovery of spatial-temporal causal interactions between thermal and methane anomalies associated with the Wenchuan earthquake

Few studies have determined the relationship between the thermal and methane anomalies associated with earthquakes. In this study, National Center for Environmental Prediction (NCEP) air temperature data and Atmospheric Infrared Sounder (AIRS) total column CH4 data were used to extract the thermal anomalies and methane concentration anomalies before 2008 Wenchuan earthquake. The Granger causality test is then used to support or disprove some conjectures that describe the relation between thermal anomalies and methane anomalies The results show that thermal anomalies appeared from May 5 to 14, 2008, and that methane anomalies appeared from May 12 to 28. Spatially, thermal anomalies occurred to the south of the epicentre in the area with the maximum secular block motion before the earthquake, and the methane anomalies occurred along the Longmenshan Fault as well as the south of the epicentre. The Granger causality results indicate that change in crustal stress caused the thermal anomalies, creating the escaping channels for the underground gases, and then lead to the methane anomalies. In terms of the lag of the methane anomalies, the methane anomalies are unlikely to have been the main cause of the thermal anomalies. However, in the area with large block motion before the earthquake and in the surface rupture area, the methane anomalies may have also influenced the local temperature.

Borehole Strain Observations Based on a State-Space Model and ApNe Analysis Associated With the 2013 Lushan Earthquake

YRY-4 borehole strainmeters have been installed in Sichuan Province, China, since 2008, aimed at monitoring the crustal activities associated with earthquakes. In this study, data from six YRY-4 strainmeters at the southwestern endpoint of the Longmenshan fault zone were analysed, to study the relationship of tectonic strain changes with the 2013 Lushan earthquake. We developed a state-space model to remove the strain response due to air pressure, solid tides and the changes in the water level to preferentially isolate non-tectonic disturbances. Strain responses to each influencing factor were estimated using the environmental coefficients computed in the state-space model by an adaptive Kalman filter with measurement noise. The results were consistent with the expected response of the strainmeter systems. The corrected strain considered to originate from underground tectonics provides new insights into the changes in the pre-earthquake strain. Approximate negentropy (ApNe) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${b}$ </tex-math></inline-formula> value were introduced to quantify the probability distribution of the corrected borehole strain and compared with the local seismic activities. The nearest station and two further stations, almost simultaneously recorded short-term ApNe anomalies six to four months before the earthquake. The anomalous region also had a correspondingly low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${b}$ </tex-math></inline-formula> value. Moreover, the anomaly acceleration rates of each station were dependent on the epicentral distances. Further comparison with the strain of random periods illustrated the significance of the extracted anomalies. Our results indicate that the corrected strain may contain seismogenic information and reflect the accelerated strain accumulation of focal areas before the earthquake.

Changes in Tropospheric Ozone Associated With Strong Earthquakes and Possible Mechanism

The index of ozone anomaly (IOA) has been proposed to detect changes in tropospheric ozone associated with strong earthquakes. The tropospheric ozone prior and after the 2008 Wenchuan earthquake has been analyzed using IOA. Atmospheric infrared sounder ozone volume mixing ratio (O3 VMR) at different pressure levels (600, 500, 400, 300, 200 hPa) for an 18-year period 2003–2020 has been considered to identify the unique behavior associated with the strong earthquakes. Our results show distinct enhancement in tropospheric ozone occurred 5 d (7 May 2008) prior to the main event and distributed along the Longmenshan fault zone. An enhancement in IOA has also been observed around the time of the 2013 Lushan and 2017 Jiuzhaigou earthquakes, but with the different emergence time, which indicates that the unusual behavior of tropospheric ozone depends on the tectonic and geological environment, focal mechanism, focal depth, meteorological conditions, and other factors. The location of increased tropospheric ozone indicates the epicenter of earthquakes. The magnitude of earthquake could be one of the important factors affecting the appearance of the anomalous tropospheric ozone. The possible mechanism for the increased tropospheric ozone associated with strong earthquakes is discussed in this article. The quasi-synchronous changes of tropospheric ozone and other parameters in the lithosphere/atmosphere/ionosphere have been found by combining with the other published results related to the Wenchuan earthquake, which show the existence of coupling during the earthquake preparation phase associated with the lithosphere–atmosphere–ionosphere coupling.

GPS observation in Sichuan-Yunnan and its vicinity before and after the Wenchuan earthquake in a decade

Based on the horizontal velocity data observed by GPS during 2004–2007, 2007–2009, and 2011–2017 before, during, and after the Wenchuan earthquake in Sichuan-Yunnan and its vicinity, we analyze evolution features of the tectonic deformation caused by crustal movement in main active fault belts, and its possible influence. We conclude: the Wenchuan earthquake area showed obvious co-seismic thrust and dextral deformation from 2007 to 2009. The earthquake, to a certain extent, promoted tectonic movements on the Gansu-Sichuan boundary, Western Qinling fault zone, Anninghe-Zemuhe fault zone, and southern Xianshuihe fault zone. The vectors and strain filed acquired by GPS during Lushan and Jiuzhaigou earthquakes period may indicate that the southwest segment in the Longmenshan fault zone still has the possibility of larger earthquakes.

Stick-slip nucleation triggering of Wenchuan earthquake

The MS8.0 Wenchuan earthquake occurred on May 12th, 2008 on the steeply reverse fault of the Longmen Shan fault zone, Western China. Catastrophic failure and rupture occurred along the listric sliding surface. Several numerical simulations have been performed to reconfigure the dynamic processes of this strong earthquake. However, few scientific studies on the stick-slip of the listric fault have been conducted. In this study, finite element method is utilized to simulate the instant stick-slip fault responses at the triggering moment. The fault surface is a non-continuous and frictional contact interface. The simulation results demonstrated that the sliding friction and sticking friction interact spatially. This interaction occurred temporarily on swarms of slip patches, rather than the entire fault slipping surface. Stick-slip causes serrated energy release, and transient aseismic slip can occur spontaneously. These tremors propagate from the epicenter upwards to the ground surface. Therefore, they may provide important details on earthquake onset rupture.

Crustal seismogenic structures and deformation styles along the Longmen Shan Fault belt in the eastern Tibetan Plateau inferred from ambient noise tomography

A seismic array comprising 80 broadband stations with ~10–20 km inter-station distances was deployed along the Longmen Shan fault belt (LMSF), the eastern boundary of the Tibetan Plateau. The recorded ambient noise data provided densely distributed inter-station cross-correlated surface waves. A new 3-D crustal S-wave velocity model for the LMSF was constructed by carrying out ambient noise tomography. The inverted model strongly improved data fitting and decreased data misfit compared to the reference (initial) model. The model highlights several crustal structure features. The Baoxing and Pengguan Massifs on the mountain side of the southern-to-middle LMSF exhibit relatively high crustal velocities, probably indicating strong crust. Low crustal velocities that may reflect weak, deformable brittle crust, exist mainly beneath the middle-to-northern segment of the LMSF and partly around the periphery of the Baoxing and Pengguan Massifs in its southern-to-middle segment. Two SW dipping low-velocity (weak) belts approximately perpendicular to the LMSF are imaged respectively around the Wenchuan-earthquake hypocenter in the south and Beichuan in the north. The low velocities in the two belts may focus movement of the eastern Tibetan Plateau relative to the Sichuan Basin (Yangtze Craton), and the uplift of the Tibetan Plateau over long time periods. Based on the velocity and tectonic structures, the young, high topography and thickened crust but low GPS shortening rates around the southern-to-middle LMSF may be due to the dominant effect of vertical crustal deformation caused by the existence of the strong Baoxing and Pengguan Massifs. This would then be in contrast to the characteristic lateral movements due to ductile crustal flow or weak, deformable brittle crust typical of the middle-to-northern LMSF.

Slip rates and paleoearthquakes along the east segment of the Guanggaishan–Dieshan fault zone, West Qinling Range, NW China

The WNW-trending Guanggaishan–Dieshan fault (GDF) is located in the West Qinling Range at a site of tectonic junction between the Tibetan plateau, the Sichuan basin and the Ordos block. Tectonically, this region is bounded by the East Kunlun fault to the southwest, the West Qinling fault to the north, and the Longmenshan fault to the southeast. The activity of the GDF is essentially related with the northeastward expansion of the Tibetan Plateau and associated strain partition between the East Kunlun fault and the West Qinling fault. This study reported the sense of fault movement, rate of fault slip, and the timing of three paleoseismic events on the east segment of the Guanggaishan–Dieshan fault (EGDF) with which no historical earthquake has been documented before. We focused our investigation on three branch faults in the central part of the EGDF using a range of study methods, e.g. structural mapping, paleoseismological trenching, unmanned aircraft vehicle photogrammetry, differential GPS survey, as well as radiocarbon and optically stimulated luminescence dating. Our new results highlighted: (1) the EGDF is dominated by the left-lateral sense of movement with a minor component of dip slip, (2) the range-bounding branch is characterized by a maximum left-lateral slip rate of 0.72 ± 0.34 mm/year and a maximum vertical-slip rate of 0.13 ± 0.03 mm/year, respectively. Kinematics of the EGDF is similar to many other active faults in the West Qinling Range, together they play a joint role in accommodating and transferring the residual left-lateral slip of the East Kunlun Fault. Three paleoseismic events were identified on the range-bounding fault based on two types of event markers: cut-cover relation and colluvial deposition. The ages of the most recent two events are estimated to be 2765–3320 cal. year BP and 12,775–13,005 cal. year BP and the age of the oldest event is as early as 18,495–32,950 cal. year BP. In contrast, there is no compelling evidence to show paleoseismic event along the rest two branches, and further work is needed to demonstrate this.

Detecting Earthquake-Related Anomalies of a Borehole Strain Network Based on Multi-Channel Singular Spectrum Analysis.

To investigate the nonlinear spatio-temporal behavior of earthquakes, a complex network has been built using borehole strain data from the southwestern endpoint of the Longmenshan fault zone, Sichuan-Yunnan region of China, and the topological structural properties of the network have been investigated based on data from 2011–2014. Herein, six observation sites were defined as nodes and their edges as the connections between them. We introduced Multi-channel Singular Spectrum Analysis (MSSA) to analyze periodic oscillations, earthquake-related strain, and noise in multi-site observations, and then defined the edges of the network by calculating the correlations between sites. The results of the daily degree centrality of the borehole strain network indicated that the strain network anomalies were correlatable with local seismicity associate with the earthquake energy in the strain network. Further investigation showed that strain network anomalies were more likely to appear before major earthquakes rather than after them, particularly within 30 days before an event. Anomaly acceleration rates were also found to be related to earthquake energy. This study has revealed the self-organizing pre-earthquake phenomena and verified the construction of borehole networks is a powerful tool for providing information on earthquake precursors and the dynamics of complex fault systems.

Modeling the Spatiotemporal Seismicity Patterns of the Longmen Shan Fault Zone Based on the Coulomb Rate and State Model

AbstractIn the past two decades, three major earthquakes have occurred near the Longmen Shan fault zone, Sichuan, China (the 2008 Mw 7.9 Wenchuan, 2013 Mw 6.6 Lushan, and 2017 Mw 6.5 Jiuzhaigou earthquakes), in response to the continuous collision of the Indian and Eurasian plates, and have produced numerous aftershocks. Recent studies have demonstrated that physics-based aftershock forecasting holds the potential capability to meet the demands of earthquake forecasting. I have successfully modeled the spatiotemporal seismicity of the Longmen Shan fault zone by applying the coulomb rate and state model by including high-quality data products (e.g., source models and receive faults) and optimized rate-and-state parameters in the calculation. I also investigate the roles of secondary triggering of aftershocks and the friction coefficient in seismicity modeling. The findings suggest that the friction coefficient plays an important role in modeling the observed seismicity, and that the secondary triggering of aftershocks in the Longmen Shan fault zone moderately affects the predicted seismicity.

Hydrothermal anomalies of the Earth's surface and crustal seismicity related to Ms8.0 Wenchuan EQ

Hydrothermal anomalies related to the Ms8.0 Wenchuan earthquake (EQ) on May 12, 2009, have been widely reported. However, the reported anomalies have not been associated with multi-geosphere analysis, and space–time analysis with crustal seismicity is lacking. In this paper, the space–time variation of hydrothermal parameters, including soil moisture, soil temperature, near-surface relative humidity (RHsig995) and air temperature (TMPsfc), was first extracted and analyzed with the NCEP-FNL reanalysis dataset. The b-value (a seismic parameter from the Gutenberg–Richter law) was calculated and mapped to unravel the crustal stress and rock rupture. Our results reveal a similar time window for hydrothermal anomalies on April 20 and April 30, 2008, and these anomalies are mainly distributed along the southern and middle parts of the Longmenshan fault zone. The surface temperature anomalies lag behind the humidity anomalies, and the accelerating stress accumulation started since June 2007 and lasted for eight to nine months before the mainshock. The b-value mapping shows a segmented difference along strike of the Longmenshan fault, and that regional stress accumulated mainly in the southern parts of the F2 and F3 faults. We propose the occurrence of a complex coupling process led by crustal stress buildup before the Wenchuan EQ. The anomalies are concentrated in the southern part of the surface rupture zone. The prolonged crustal stress accumulation corresponds to the short intermittent hydrothermal response on the Earth’s surface before the Wenchuan EQ. Our findings reveal new hydrothermal anomalies in the Earth’s surface and atmosphere and explore direct link with seismogenic processes in the crust.

Lithospheric structures of and tectonic implications for the central–east Tibetan plateau inferred from joint tomography of receiver functions and surface waves

SUMMARYWe present an updated joint tomographic method to simultaneously invert receiver function waveforms and surface wave dispersions for a 3-D S-wave velocity (Vs) model. By applying this method to observations from ∼900 seismic stations and with a priori Moho constraints from previous studies, we construct a 3-D lithospheric S-wave velocity model and crustal-thickness map for the central–east Tibetan plateau. Data misfit/fitting shows that the inverted model can fit the receiver functions and surface wave dispersions reasonably well, and checkerboard tests show the model can retrieve major structural information. The results highlight several features. Within the plateau crustal thickness is &amp;gt;60 km and outwith the plateau it is ∼40 km. Obvious Moho offsets and lateral variations of crustal velocities exist beneath the eastern (Longmen Shan Fault), northern (central–east Kunlun Fault) and northeastern (east Kunlun Fault) boundaries of the plateau, but with decreasing intensity. Segmented high upper-mantle velocities have varied occurrences and depth extents from south/southwest to north/northeast in the plateau. A Z-shaped upper-mantle low-velocity channel, which was taken as Tibetan lithospheric mantle, reflecting deformable material lies along the northern and eastern periphery of the Tibetan plateau, seemingly separating two large high-velocity mantle areas that, respectively, correspond to the Indian and Asian lithospheres. Other small high-velocity mantle segments overlain by the Z-shaped channel are possibly remnants of cold microplates/slabs associated with subductions/collisions prior to the Indian–Eurasian collision during the accretion of the Tibetan region. By integrating the Vs structures with known tectonic information, we derive that the Indian slab generally underlies the plateau south of the Bangong–Nujiang suture in central Tibet and the Jinsha River suture in eastern Tibet and west of the Lanchangjiang suture in southeastern Tibet. The eastern, northern, northeastern and southeastern boundaries of the Tibetan plateau have undergone deformation with decreasing intensity. The weakly resisting northeast and southeast margins, bounded by a wider softer channel of uppermost mantle material, are two potential regions for plateau expansion in the future.