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# Active faults, earthquake hazards and associated geodynamic processes in continental China

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... Strong earthquakes (M S > 7) often occur at the boundary of active blocks in the mainland (Deng et al., 2003;Xu, 2006;Zhang et al., 2013). The North Qinling Fault, an active fault located at the boundary between the North China Block and the South China Block (i.e., first order blocks in Chinese mainland), can produce strong earthquakes (Figure 1). ...
... The GPS data used in this study come from Wang and Shen (2020). Our study mainly considered data from campaign and continuous GPS sites included in the Crustal Movement Observation Network of China (CMONOC) I and Zhang et al. (2013). ...
... The North Qinling Fault is a major structure in a boundary zone characterized by active tectonic blocks (i.e., the North China Block and the South China Block) in mainland China (Figure 2, Zhang et al., 2013), and separates the Weihe Basin from the Qinling Mountains. We collected evidence that the North Qinling Fault is the most active and largest structure in the Weihe Basin, and it subjects the area to a high earthquake hazard. ...
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The North Qinling Fault, located at the boundary of the North China Block and the South China Block, represents an important tectonic structure between the Weihe Basin and the Qinling Mountains, and controls the subsidence and expansion of the Weihe Basin. This fault has been highly active and has caused strong earthquakes since the Holocene and in a pre-seismic stage currently, as indicated by the many paleoearthquake traces found along it. To determine the present-day activity and seismic potential of the North Qinling Fault, by inverting GPS data, we produced fault locking depth, slip rate, and regional strain fields maps; moreover, based on seismicity, we produced a seismic b-value map. Combining this information with modern seismicity, we were able to comprehensively analyze the seismic potential of different fault segments. Our inversion of GPS data showed that the slip rate of the western segment of the fault (Qingjiangkou–Xitangyu) and the correspondent locking depth are 1.33 mm/a and 13.54 km, respectively, while the slip rate of the middle segment (Xitangyu–Fengyukou) and the correspondent locking depth are 0.45 mm/a and 8.58 km, respectively; finally, the slip rate of the eastern segment (Xitangyu–Daiyu) and the correspondent locking depth are 0.36 mm/a and 21.46 km, respectively. The locking depths of the western and middle segments of the fault are shallower than 90% of the seismic cutoff depth, while the locking depth of the eastern segment of the fault is similar to 90% of the seismic cutoff depth, indicating that “deep creep” occurs in the western and middle segments, while the eastern segment is locked. Modern small earthquakes have involved the western and middle segments of the fault, while the eastern segment has acted as a seismic gap with weak seismicity, characterized by a higher shear strain value and a lower b-value. These characteristics reflect the relationship between the locking depth and seismicity distribution. The results of our comprehensive analysis, combined with field geological surveys, show that the eastern segment of the North Qinling Fault has a strong seismic potential and is presently locked.
... geodetic and seismological observations that manifest little extension across these structures (He et al., 2003;P. Zhang et al., 2013). ...
... The deformation within this block is negligible; whereas seismicity across the boundaries is frequent and several strong earthquakes have occurred across its margins (P. Zhang et al., 2013). Seismic activity occurring across the block boundaries is mainly strike-slip faulting events, despite several events along the southwestern edge showing shortening motions (P. ...
... Seismic activity occurring across the block boundaries is mainly strike-slip faulting events, despite several events along the southwestern edge showing shortening motions (P. Zhang et al., 2013). ...
... These two earthquakes occurred in the southeastern edge and in high-altitude hinterland of the eastern Tibetan Plateau respectively (Fig. 1a), and both caused human casualties and property damage, triggering earthquake emergency response efforts. The occurrence of strong earthquakes at different sites within 5 h of each other indicates continuous tectonic movements and violent seismic activity on the Tibetan Plateau under the collisional convergence between the Indian and Eurasian continental plates [3]. Observations of crustal motion expose clockwise rotational deformation in the eastern Tibetan Plateau along the axis of the eastern Himalayan syntaxis [2,4]. ...
... Observations of crustal motion expose clockwise rotational deformation in the eastern Tibetan Plateau along the axis of the eastern Himalayan syntaxis [2,4]. Furthermore, studies combining tectonic and historical seismic data with numerical simulations reveal that the shear effect of the eastward flow of crustal material within the Tibetan Plateau leads to active sinistral strike-slip faulting in the northern part of the plateau and dextral strike-slip faulting in the south [1,3,5]. The source mechanisms of these two events (Fig. S1 online) suggest that both earthquakes occurred in response to the strain induced by the current crustal deformation, which is consistent with the above deformation pattern of the Tibetan Plateau. ...
... To study the Maduo earthquake source process, due to the lack of near-source seismic records, we used far-field P and SH waveforms and coseismic line-of-sight (LOS) displacements obtained from the ESA Sentinel satellites. First, the basic parameters of the seismogenic fault, including the hypocenter, strike, dip and rake angle, were determined using the focal mechanism ( Fig. 1a) combined with the tectonic background and active fault information [3]. Then, a more accurate geometric model of the fault was constructed by using coseismic deformation images (InSAR). ...
... China is located in the southeast of the Eurasian plate. Due to the continuous collision and pushing between the Indian plate and the Eurasian plate in the southwest, a strong deformation area with a width of thousands of kilometers is formed in mainland China, and it also affects the hinterland of Central Asia, Southeast Asia, and Eastern China [1][2][3][4]. The unique tectonic background has made China one of the countries with the most severe seismic disasters in the world, and has also made the formation and evolution of tectonic deformation a hot spot in earth science research. ...
... There have been one earthquake of a magnitude greater than seven and six earthquakes of a magnitude greater than six since 1967. The focal mechanism solutions show that the earthquakes at the north and south sides of the Tianshan Mountains are mainly thrust, and the earthquakes in the Tianshan Mountains are mainly strike-slip, which is consistent with the others research results [4,51]. The nodal plane is approximately parallel to the extension direction of the Tianshan block, and the principal compressive stress axis is almost perpendicular to the Tianshan block, corresponding to the north-south shortening and the east-west extension. ...
... However, the strong stress that results in the north-south contraction of the Tarim "rigid body" is clearly not caused by the compression of the Pamir Plateau in the west. For a rigid block on a spherical surface, its motion can be described by the rotation around the Euler pole; that is, the rate of motion inside the block increases regularly with the increase of the radius of rotation [4]. Combined with the difference of baseline length change between the east and the west part of the southern Tianshan fault zone, it is inferred that the Qinghai-Tibet Plateau compacts the Tarim block northward and causes it to rotate clockwise, which is one of the leading factors to the deformation of the Tianshan Mountain, and is also the main cause of the occurrence of strong earthquakes and tectonic deformation in this area. ...
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In this paper, we propose a method for the analysis of tectonic movement and crustal deformation by using GNSS baseline length change rates or baseline linear strain rates. The method is applied to daily coordinate solutions of continuous GNSS stations of the Crustal Movement Observation Network of China (CMONOC). The results show that: (a) The baseline linear strain rates are uneven in space, which is prominent in the Tianshan, Sichuan-Yunnan, Qinghai-Tibet Plateau, and Yanjing areas, with a maximum value of 1 × 10−7 a−1, and about two orders smaller in the South China block, the Northeast block, and the inner area of the Tarim basin, where the average baseline linear strain rates are 1.471 × 10−9 a−1, 2.242 × 10−9 a−1, and 3.056 × 10−9 a−1, respectively; (b) Active crustal deformation and strong earthquakes in the Xinjiang area are mainly located in the north and south sides of the Tianshan block; the compression deformations both inside the Tarim block and in the southern Tianshan fault zone are all increasing from east to west, and the Tarim block is not a completely “rigid block”, with the shrinkage rate in the west part at about 1~2 mm/a; (c) The principal directions of crustal deformation in the Xinjiang, Tibet, and Sichuan-Yunnan regions are generally in the north—south compression and east—west extension, indicating that the collision and wedging between the Indian and Eurasian plates are still the main source of tectonic movements in mainland China.
... Continuous GPS observational data can be used to extract crustal deformation information, to analyse crustal displacement, stress, strain field and other dynamic characteristics (Qu et al., 2019;Zhao et al., 2015;Zhang et al., 2013b). Wang and Shen (2020) processed GPS observational data from mainland China over the past 25 years in detail and obtained the long-term rates of the stations and a solution with high spatial resolution and consistent rates, which can reveal the rotation of the southeastern boundary of the Tibetan Plateau and the internal deformation of the South China Block. ...
... Continental geology has revealed internal structures at multiple scales within plates, and the lithospheric composition has vertical and horizontal variations (Xia et al., 2018;Chen et al., 2001;Zhang et al., 2013a;Zhang et al., 2013b). The tectonic forces generated by relative motions between plates or blocks can be transmitted to intraplate regions, causing the intraplate lithosphere to accumulate tectonic stress. ...
... GPS-based space observational methods can now monitor large-scale crustal deformation. Therefore, the use of high-precision, high-resolution GPS velocity data, combined with geological and geophysical observations, can more comprehensively characterize the current crustal deformation characteristics (Zhao et al., 2015;Zhang et al., 2013b). In this paper, using the latest GPS velocity data (Wang and Shen, 2020) and considering the geological requirements of intraplate earthquakes in the South China Block, we chose Taiwan as a reference point and recalculated the GPS velocities (Fig. 5). ...
Article
The relationship between intraplate earthquakes and intraplate deformation is one of the great conundrums faced by plate tectonics theory. In particular, large earthquakes are more common in Eurasia than in other continents around the world. Formed by the Neoproterozoic collision of the Cathaysia Block and the Yangtze Craton along the Jiangnan Orogenic Belt, the South China Block is well known for its relative stability in the Cenozoic era. However, numerous intraplate earthquakes have occurred in the Yangtze Craton and their mechanism is not well known. Incomplete understanding of the deep geological structure and deep-shallow coupling mechanism has led to two hypotheses about the nature and origin of intraplate earthquakes in the area: the far-field effects of plate subduction and the internal deformation of intraplate lithosphere. In this paper we attempt to provide a new perspective to the intraplate earthquake mechanism in the South China Block. In doing so, we have collected and reviewed multi-source and multi-scale high-precision geophysical data to improve the interpretation of the South China Block at depths from 1000 km to 1 km. The data interpretations help clarify the coupling relationship between the lithospheric structures and intraplate earthquakes in the South China Block. This paper emphasizes the strong structural heterogeneity in the South China Block. In plan view, the block is a mosaic structure formed by the assembly of various continental micro-blocks along several weak zones since the Neoproterozoic. In cross section, the structures of different units are segmented by detachment faults. For our analysis, we have used a three-layer model to describe the coupling of the asthenosphere-lithosphere, lithospheric mantle-crust and within the crust in the South China Block. The three cascade effects are coupled to form an intraplate earthquake triggering mechanism in the Yangtze Craton. The subduction effects of the Pacific Plate and the blocking by the Yangtze Craton are considered to cause a large-scale stress concentration in the Huaying Mountain fold-and-thrust belt; combined with three sets of detachment layers as internal factors, this stress results in numerous small-magnitude intraplate earthquakes occurring in the stable craton. This paper suggests that the deep structures can control the shallow tectonic processes and the plate tectonic responses and that the lithospheric strength can affect the triggering of intraplate earthquakes.
... There are no large-scale active faults developed within Ordos Block. It has good integrity and no records of earthquakes with a magnitude greater than M6 (Research Group of Active Fault System around Ordos Massif, 1988;Zhang et al., 2013), indicating the block is internally stable. However, there are series of large faulted basins controlled by active normal faults developed along the Ordos Block margin (Figure 1). ...
... However, there are series of large faulted basins controlled by active normal faults developed along the Ordos Block margin (Figure 1). A large number of studies have shown that regional tectonic activity and strong earthquakes mainly occur on active crustal block boundaries (Zhang et al., 2003;Zhang et al., 2004;Zhang et al., 2013;Zheng et al., 2020). According to historical data, more than 10 earthquakes with M ≥ 7 have occurred around the Ordos Block, including five earthquakes with M ≥ 8 (Research Group of Active Fault System around Ordos Massif, 1988;Jiang et al., 2000;Zhang et al., 2003). ...
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The Zhuozishan West Piedmont Fault (ZWPF) is an active normal fault in the northwestern corner of the Ordos Block. Studying the recurrence characteristics of paleoearthquakes is useful for understanding the regional seismic hazard potential. In this study, paleoseismic trench and optically stimulated luminescence (OSL) dating methods are used to determine the temporal sequence of paleoearthquakes. Severn earthquakes were constrained to be E7 (73.4 ± 12.9 ka to 75.3 ± 10.6 ka), E6, (63.7 ± 7.4 ka to 64.4 ± 8.2 ka), E5 (53.2 ± 7.0 ka to 58.7 ± 6.5 ka), E4 (42.6 ± 6.3 ka to 47.7 ± 5.8 ka), E3 (31.0–3.4 ka to 31.3 ± 3.4 ka), E2 (26.1 ± 2.7 ka to 28.1 ± 3.8 ka) and E1 (15.8 ± 1.9 ka to 20.2 ± 2.6 ka). The recurrence interval of strong earthquakes in the ZWPF is roughly constrained to be 8.1–14 ka, with magnitudes of Mw 7.0–7.4 that ruptured the entire fault. Based on the timing of the latest earthquake event, the elapsed time approached or exceeded the recurrence interval revealed from paleoearthquakes. Hence, we suggest that the northwestern corner of the Ordos Block has a significantly high seismic hazard potential and that the occurrence of a strong earthquake should not be underestimated.
... ± 42.6°E, which approximately corresponds to the horizontal principal compressive stress in the CRSC. At the surface, continuous deformation observations (i.e., GPS) demonstrate that the entire South China block moved in a direction of N110°-130°E as a whole, at a speed of 8-11 mm/a and without significant differential movements within the block (Molnar and Gipson 1996;Shen et al. 2000;Zhou et al. 2000;Calais et al. 2003;Zhang et al. 2013), indicating that the South China block may be a relatively rigid block with a uniform motion. Consequently, there appears to be a coupled crust in the CRSC with vertically consistent stress orientations. ...
... Moreover, the S Hmax directions of the two samples with similar depths agree with each other very well. Overall, the averaged S Hmax direction of all samples is N43° ± 19°W, which agrees with previous findings (Gao et al. 2009;Lin et al. 2009;Zhang et al. 2013) and is generally consistent with the subduction direction of the Philippine Sea plate towards the Eurasian plate. Byerlee (1978) compiled an extensive dataset of laboratory friction measurements derived from natural joints in rocks, failure discontinuities in triaxial compression tests and artificial joints with various roughness, concluding that friction is nearly independent of the rock type and deriving the frictional coefficient, μ, of 0.6-1.0, ...
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The in-situ stress state in the shallow crust of the coastal region of Southeastern China (CRSC) remains poorly understood. We conducted anelastic strain recovery measurements in a 2 km deep geothermal borehole to investigate the in-situ stress state. Four high-quality granite core samples were employed to successfully estimate the full stress tensors. The results show that the maximum principal stress σ1 is nearly vertical, implying an extensional shallow crust that is controlled by normal faulting. From ~1865 to ~1959 m in depth, the maximum and minimum horizontal principal stresses (SHmax and Shmin) are 36.1–48.7 MPa and 34.0–38.5 MPa, respectively. Based on the paleomagnetic analysis, the orientation of the maximum horizontal compressive stress SHmax is determined as N43° ± 19°W and aligned with the subduction direction of the Philippine Sea plate. According to the compiled stress data, the SHmax orientations in the CRSC rotate counterclockwise towards the Chinese mainland, which are consistent with those of the earthquake focal mechanisms and regardless of earthquake type, indicating a heterogeneous stress field dominancy in the CRSC. Our findings manifest that there is a lower horizontal compressive stress state in the upper crust in the study region. We also discussed the possible influence of in-situ stress on wellbore stability and fracture propagation in hot dry rock exploration and further quantitatively analyzed the reactivation possibility of natural fractures under different injection pressures. This study will provide scientific data for geodynamic research, fault seismicity, and geothermal development in the region in the future.
... The Chinese mainland is divided into several active tectonic blocks by boundary fault zones. Large magnitude earthquakes occur frequently along these boundaries, implying that there is a link between the two [1][2][3][4][5][6][7][8]. Therefore, it is critical to understand the formation mechanism and occur-rence of such earthquakes along active tectonic block boundaries, based on their long recurrence cycles and exceedingly destructive characteristics [9][10][11]. ...
... As long as there are trenches at the end of the fault segment, the rupture will be penetrated, even if there is no trench in the middle segment. 4 Lithosphere ...
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Tectonic belts along active tectonic block boundaries comprise one or more active faults; along which, large earthquakes recur. Therefore, it is important to establish the recurrence behavior of large earthquakes along such boundary zones for studying their characteristics and developments. Many paleoearthquake studies make it possible to investigate the recurrence behavior of large earthquakes along the northern boundary of the Ordos block (NBOB). Based on the previous studies, data from 52 trenches were collected to reconstruct prehistoric earthquakes using an improved multiple trench constraining method. This method is based on paleoearthquake indicators and trench location distribution to constrain the rupture time and length, thereby reducing the selection bias of fixed rupture length to construct additional rupture scenarios. The results suggest that the NBOB comprises four normal faults (from west to east): the Langshan Piedmont Fault (LPF), Sertengshan Piedmont Fault (SPF), Wulashan Piedmont Fault (WPF), and Daqingshan Piedmont Fault (DPF); along which, six, seven, eight, and six paleoearthquakes have occurred within approximately 15,000 yr, respectively. In addition, recurrence behaviors of the individual faults exhibit remarkable periodicity. The regional fault network along the NBOB reveals clustered characteristics with six clusters propagating either westward or eastward and a recurrence time of approximately 1,300 yr. Large earthquake events have occurred along the LPF, WPF, and DPF according to the most recent cluster; however, earthquakes were absent along the SPF, and no evidence of large earthquakes was observed along the NBOB after the 849 CE earthquake. Thus, we discuss the possibility of occurrence of large earthquakes along the SPF after the 849 CE earthquake based on earthquake recurrence and cluster migration behavior. Additional research is required to assess the potential risk of the occurrence of a large earthquake along the SPF in the future.
... Moreover, the modern Tarim Basin, termed the "walled basin" by Carroll et al. (2010), is surrounded by the Cenozoic uplift of mountain ranges such as the Tian Shan, West-Kunlun and Altyn and represents seismically active zones of rejuvenated intraplate deformation that began as early as the Permian (Hendrix et al., 1992;Carroll et al., 1995;Wartes et al., 2002). Modern seismicity in response to north-south shortening triggered by the ongoing collision between the Tibetan Plateau and the Indian subcontinent continues to be focused within the basin-bounding active mountain ranges, whereas the basin interiors are relatively aseismic and typically experiencing minor deformation (e.g., Zhang et al., 2013b) ( Figure 1A). ...
... Neil and Houseman (1997) proposed a simplified rheological model for the Tarim Basin and Tian Shan where the lithospheric temperature may positively affect the mechanical strength of the lithosphere. As dominated by the thermal state and structure, the lateral variation in crustal rheology structure may provide crucial constraints on understanding the intra-or inter-block deformation mechanism (Neil and Houseman, 1997;Zhang et al., 2013b), which can be expressed by the CPD and Curie/Moho offset that alter the crust-scale thermal regime and compositional structure ( Figure 8). ...
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The lateral distribution of the magnetic layer beneath the Tarim Craton and its environs was estimated from spectral analysis using the newest high-resolution aeromagnetic dataset of mainland China, which is enlarged by EMAG2. As a proxy, the Curie point depth (CPD) provides a comprehensive view of a crust-scale thermal regime, accounted for the depth at which magnetite becomes paramagnetic, and the correspondence of the CPD with the tectonic regime indicates that the CPD is useful for delineating the regional crustal thermal structure. Furthermore, lateral variations in CPD provide useful insights into the lithospheric thermal state of the Tarim Craton and its surrounding areas and can be related to ancient and active tectonics, such as geothermal activity, seismicity, and mineral-petroleum generation. In the Tarim interior, the NW domain covering the Bachu Uplift and its surrounding areas corresponds to the minimum magnetic CPD signature geometry of this area, which is most likely linked to the Permian Tarim plume-lithosphere interaction. In contrast, the other domains are characterized by large CPD values (up to 50 km), which are floored by a Precambrian basement without the Permian magmatism modification. Moreover, the estimated CPD values are consistent with surface heat flow measurements with an inverse correlation, which can assist in identifying the potential area for mineral deposits and hydrocarbon fields. Earthquakes are mostly concentrated in the gradient and transition zones of the Curie surface, suggesting that these abrupt variation domains in the crustal thermal structure act as a secondary mechanism for earthquake generation.
... Frozen ground covers all the regions along the Qinghai-Tibet (QT) Railway, as shown in Fig. 1(a) [40]. Besides, the QT plateau is one of the most active seismic regions in China and has a large number of active faults, as shown in Fig. 1 (b) [41]. Earthquakes occur frequently in QT Plateau, i.e., the 2001 Ms 8.1 Central Kunlun Earthquake [42] and the 2010 Ms 7.1 Yushu Earthquake [43]. ...
... Frozen ground and active fault distributions in Qinghai-Tibet Plateau. (a) Frozen ground distribution[40] (b) Active fault distribution[41]. ...
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Ground seasonal freezing and thawing in cold regions can alter boundary conditions of bridge pile foundations and influence their seismic behaviors. This article describes a test apparatus with a custom-designed cooling system for investigating the seismic behavior of pile foundations in seasonally frozen ground. Two 1/8-scale models of a reinforced concrete bridge pier with pile foundations were fabricated for conducting quasi-static tests under unfrozen and frozen conditions. Test observations and data were used to analyze failure characteristics of pile foundation subjected to cyclic lateral loading under the two conditions and reveal the frozen soil effects. It was found that ground freezing greatly enhanced the loading carrying capacity while partly weakened the deformation capacity of the pile-soil system. It is not easy to fail if upper layer soil was frozen, and the frozen soil layer shifted the pile failure zone upward compared with the unfrozen condition. The strength degradation was obvious in the pile-soil system under frozen condition due to the fracture of the steel bar. Furthermore, the pile foundation in frozen soils exhibited more stable and reliable energy dissipation than the pile foundation in unfrozen soils under large seismic load, which was attributed to the severe damage of the pile foundation in frozen soils. A simplified force–displacement model was proposed for the pile-soil system under unfrozen and frozen conditions based on the testing results. These results can provide references for seismic design of reinforced concrete pile foundations in cold regions.
... Rapid assessment of damage to buildings after an earthquake is essential for emergency response, rescue operations, and postdisaster reconstruction [1]. China accounts for 7% of the world's land area and is responsible for about 33% of the world's continental earthquakes, resulting in more than 50% of the global earthquake death toll [2][3][4][5][6][7]. After a devastating earthquake, the seismic rating of a building's structural type plays a critical role in casualties. ...
... An important extension of this application is the use of TLS to scan seemingly safe buildings after an earthquake to ensure that there are no significant deformations that may not be visually detectable [27]. 2 Advances in Civil Engineering e raw data collected by TLS on the building surface mainly include X/Y/Z spatial location information (columns 1-3), reflected intensity (column 4), RGB information (columns 5-7), and X/Y/Z normal line information (columns 8-10) ( Figure 2). e instrument's supporting software can view the seismic information such as cracks, shedding, and tilt deformation of the wall data collected, but the quantitative analysis is insufficient to meet the needs of the industry technical analysis. ...
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Earthquake disasters can have a serious impact on people’s lives and property, with damage to buildings being one of the main causes of death and injury. A rapid assessment of the extent of building damage is essential for emergency response management, rescue operations, and reconstruction. Terrestrial laser scanning technology can obtain high precision light detection and ranging (LiDAR) point cloud data of the target. The technology is widely used in various fields; however, the quantitative analysis of building seismic information is the focus and difficulty of ground-based LiDAR data analysis processing. This paper takes full advantage of the high-precision characteristics of ground-based LiDAR data. A triangular network vector model (TIN-shaped model) was created in conjunction with the alpha shapes algorithm, solving the problem of small, nonvisually identifiable postearthquake building damage feature extraction bias. The model measures the length, width, and depth of building cracks, extracts the amount of wall tilt deformation, and labels the deformation zone. The creation of this model can provide scientific basis and technical support for postearthquake emergency relief, assessment of damage to buildings, extraction of deformation characteristics of other structures (bridges, tunnels, dams, etc.), and seismic reinforcement of buildings. The research data in this paper were collected by the author’s research team in the first time after the 2013 Lushan earthquake and is one of the few sets of foundation of LiDAR data covering the full range of postearthquake building types in the region, with the data information mainly including different damage levels of different structural types of buildings. The modeling analysis of this data provides a scientific basis for establishing the earthquake damage matrix of buildings in the region.
... The intense extrusion of materials from the Qinghai-Tibet plateau is responsible for the complex and extremely active crustal activity in this area. The present-day crustal tectonic stresses and crustal activity, both featuring clockwise rotation around the Eastern Himalayan syntaxis, gave rise to a number of large active structure zones, which include the Longmenshan structure belt and the Xianshuihe-Xiaojiang fault system, as well as many medium and other size active fault systems within them (Wang EC et al., 1998;Zhang PZ et al., 2013). Among these faults, the most active ones are typically found on the boundary of the Sichuan-Yunnan block, where the highest activity can be in the range of 10-15 mm/a (Zhang PZ et al., 2004, 2013. ...
... The present-day crustal tectonic stresses and crustal activity, both featuring clockwise rotation around the Eastern Himalayan syntaxis, gave rise to a number of large active structure zones, which include the Longmenshan structure belt and the Xianshuihe-Xiaojiang fault system, as well as many medium and other size active fault systems within them (Wang EC et al., 1998;Zhang PZ et al., 2013). Among these faults, the most active ones are typically found on the boundary of the Sichuan-Yunnan block, where the highest activity can be in the range of 10-15 mm/a (Zhang PZ et al., 2004, 2013. Boundaries of the secondary blocks are mostly home to medium-sized faults with fault activity rate mostly distributed in the 0.5 -2.0 mm/a range Shen ZK et al., 2005). ...
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The Yangtze River Economic Belt (YREB) spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and present-day crustal deformation. Active faults and seismic activity are important geological factors for the planning and development of the YREB. In this paper, the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings, using both remote-sensing data and geological survey results. The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed. The main active fault zones in the western YREB, together with the neighboring regional active faults, make up an arc fault block region comprising primarily of Sichuan-Yunnan and a “Sichuan-Yunnan arc rotational-shear active tectonic system” strong deformation region that features rotation, shear and extensional deformation. The active faults in the central-eastern YREB, with seven NE-NNE and seven NW-NWW active faults (the “7-longitudinal, 7-horizontal” pattern), macroscopically make up a “chessboard tectonic system” medium-weak deformation region in the geomechanical tectonic system. They are also the main geological constraints for the crustal stability of the YREB.
... The collision of the Indian-Eurasian plate in the west and the subduction of the Pacific plate in the east have caused frequent strong earthquakes and serious earthquake disasters in China's Mainland (Zhang et al., 2013;Zhou et al., 2017). Therefore, it is a basic national policy of China to actively carry out earthquake prevention and disaster reduction, including earthquake monitoring and prediction, and minimize earthquake risk. ...
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This paper mainly introduces the application and progress of the time-varying gravity in earthquake research in the Chinese Mainland. Since the Xingtai earthquake in 1966, China has begun mobile gravity monitoring, trying to explore the relationship between gravity changes and seismic activities. The gravity changes before and after the Haicheng M S7.3 earthquake in 1975 and the Tangshan M S7.8 earthquake in 1976 were observed. In 1981, a high-precision metal spring gravimeter was introduced to carry out high-precision mobile gravity observation in the key earthquake monitoring areas in western Yunnan. The gravity anomaly changes near the epicenters of the Lijiang M S7.0 earthquakes in 1996 were observed. In 1998, a high-precision absolute gravity survey was introduced to carry out the overall scale gravity field monitoring in the Chinese Mainland, and the large-scale gravity change information before Wenchuan M S8.0 and Yutian M S7.3 earthquakes in 2008 was obtained, and the effective prediction opinions were given. After the Wenchuan M S8.0 earthquake in 2008, the integration of the national network and the regional network accelerated, forming the whole gravity observation network in the Chinese Mainland, which made a relatively successful medium-term prediction for a series of earthquakes with M S6.0 or above (such as Lushan M S7.0, Menyuan M S6.4, and Jiuzhaigou M S7.0) in recent years and played an important role in the study of the earthquake mechanism and earthquake prediction level in China. Finally, the existing problems in time-varying gravity monitoring in China are pointed out, and the prospect of earthquake research using time-varying gravity monitoring data is put forward.
... With the development of the active tectonic block theory for strong earthquake preparation in the past two decades, the previous study concluded that the strong earthquakes in the Chinese mainland are controlled by the motion and deformation of the active tectonic block. Such motion and deformation made the strong seismicity in the Chinese mainland have characteristics as follows: widely distributed, strong in the west and weak in the east, alternating dynamic and static, and zonation (Zhang et al.,2003;Zhang et al., 2004;Zhang et al., 2013). The primary tectonic deformations and strong earthquakes in the Chinese mainland occurred in active tectonic block boundary zones, and a few lower magnitude strong earthquakes occurred inside the continuously deformed tectonic blocks. ...
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The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland. Based on the strong earthquake recurrence model, the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault, which are adopted from relevant studies such as seismological geology, geodesy, and historical earthquake records. Based on the long-term predictions of large earthquakes throughout the world, this paper proposes a comprehensive judgment scheme based on the fault segments with seismic gap, motion strongly locked, sparse small-moderate earthquakes, and apparent Coulomb stress increase. This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland. The present loading rate of each fault is first constrained by geodetic observations; the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake.
... During the late stage of Himalayan evolution in the Pliocene, the east-west compressional tectonic stress changed to an approximately north-south direction, causing the NNW to NW trending faults to change motion to dextral strike-slip or normal faulting components (Cui et al., 2006). suggest that the unmapped fault on which the Yangbi sequence occurred was originally on a NW trending sinistral strike-slip, reactivated with dextral strike-slip motion due to resistance of the Lanping-Simao block to north-south expulsion of Tibetan Plateau material to the southeast (Wang & Shen, 2020;Zhang et al., 2013). According to Wang et al. (2008), the WQW fault has a relatively low strike-slip slip rate of 1-3 mm/yr, and a very low slip rate is expected for the fault that ruptured in 2021 as there was very little activity in the fault zone and no mapped surface trace prior to this event. ...
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The 2021 MW 6.0 Yangbi, Yunnan strike‐slip earthquake occurred on an unmapped crustal fault near the Weixi‐Qiaoho‐Weishan Fault along the southeast margin of the Tibetan Plateau. Using near‐source broadband seismic data from ChinArray, we investigate the spatial and temporal rupture evolution of the mainshock using apparent moment‐rate functions (AMRFs) determined by the empirical Green's function (EGF) method. Assuming a 1D line source on the fault plane, the rupture propagated unilaterally southeastward (∼144°) over a rupture length of ∼8.0 km with an estimated rupture speed of 2.1 km/s to 2.4 km/s. A 2D coseismic slip distribution for an assumed maximum rupture propagation speed of 2.2 km/s indicates that the rupture propagated to the southeast ∼8.0 km along strike and ∼5.0 km downdip with a peak slip of ∼2.1 m before stopping near the largest foreshock, where three bifurcating subfaults intersect. Using the AMRFs, the radiated energy of the mainshock is estimated as ∼1.6×1013J $1.6\times {10}^{13}\,\mathrm{J}$. The relatively low moment scaled radiated energy ER/M0 ${E}_{R}/{M}_{0}$ of 1.5 × 10⁻⁵ and intense foreshock and aftershock activity might indicate reactivation of an immature fault. The earthquake sequence is mainly distributed along a northwest‐southeast trend, and aftershocks and foreshocks are distributed near the periphery of the mainshock large‐slip area, suggesting that the stress in the mainshock slip zone is significantly reduced to below the level for more than a few overlapping aftershock to occur.
... The high mountainous areas of China are prone to landslides due to active tectonic movement, complex geological environment, diverse climate types, and intense human activities [1,2]. In 2020, China experienced 4810 landslides, resulting in more than 117 dead or missing, and more than 717 million USD in economic losses. ...
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Landslides have been frequently occurring in the high mountainous areas in China and poses serious threats to peoples’ lives and property, economic development, and national security. Detecting and monitoring quiescent or active landslides is important for predicting risks and mitigating losses. However, traditional ground survey methods, such as field investigation, GNSS, and total stations, are only suitable for field investigation at a specific site rather than identifying landslides over a large area, as they are expensive, time-consuming, and laborious. In this study, the feasibility of using SBAS-InSAR to detect landslides in the high mountainous areas along the Yunnan Myanmar border was tested first, with fifty-four IW mode Sentinel-1A ascending scenes from 12 January 2019 to 8 December 2020. Next, the Yolo deep-learning model with Gaofen-2 images captured on 5 December 2020 was tested. Finally, the two techniques were combined to achieve better performance, given each of them has intrinsic limitations on landslide detection. The experiment indicated that the combination could improve the match rate between detection results and references, which implied that the performance of landslide detection can be improved with the fusion of time series SAR images and optical images.
... When an active fault is locked, it continuously accumulates energy under the action of stress. When it exceeds its stability limit, an earthquake occurs and releases energy, which then enters the next seismic cycle (Wallace et al., 2004;Zhang et al., 2013a;Qiu and Qiao, 2017). To analyze the seismic hazards of the Qilian-Haiyuan fault zone in the future, we studied the seismic hazards of each segment of the fault on the basis of the data of the fault locking degree and occurrence of small earthquakes. ...
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By using GPS-derived velocities of 2015–2021 and a negative dislocation program, we inverted the locking degree and slip rate deficit in the Qilian–Haiyuan fault zone, and combined with the distribution of small earthquakes in the fault, we studied the characteristics before the 2022 Menyuan M S 6.9 earthquake and analyzed the future seismic hazards of each segment within this fault zone. The regional crustal deformation pattern is discussed with regard to the fault slip rate and regional strain rate field. The preliminary results show that before the earthquake, the seismogenic fault was strong locked, with a high locking depth, the slip rate deficit was large, and the distribution of small earthquakes was relatively few, these characteristics are closely related to the occurrence of strong earthquakes, according to the aftershock relocation results, further, it is believed that the earthquake may link the Lenglongling and Tuolaishan faults into a large strike-slip fault. The Jinqianghe fault, the Lenglongling fault, and the eastern segment of the Tuolaishan fault are strongly locked, with high locking depth and large slip rate deficit, combined with the occurrence of small earthquakes and the locking degree before the 2022 Menyuan M S 6.9 earthquake, indicate that the eastern segment of the Tuolaishan fault is highly likely to have strong earthquakes in the future, which requires further attention. In addition, the strike-slip rate of the Qilian–Haiyuan fault zone is mainly between 3.9 and 4.3 mm/yr, the overall movement of the fault is consistent, and the compressional rate gradually decreases from 2.9 mm/yr in the western segment to 1 mm/yr in the eastern segment; the fault compressional rate may be related to the crustal shortening (formation basin and uplift mountain). Therefore, the present-day crustal deformation in the northeastern margin of the Tibetan Plateau is mainly distributed in the shortened region of the crust on the Qilian Shan area and left-lateral strike-slip localized on the Qilian–Haiyuan fault zone.
... By the movement mode, faults can be categorized into three types: normal, reverse and strike-slip faults. Abundant literature exists for the rupture problems of normal and reverse faults (e.g., Zhang et al. 2013;Liu et al. 2015;Kiani 2016a, b;Ahmadi et al. 2018;Cai et al. 2019;Tali et al 2019). Limited results have been reported for problems of the strike-slip faults, especially for tunnel projects (Milad et al. 2020). ...
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The current paper evaluates the response of a tunnel subjected to strike-slip fault rupture with experimental and numerical approaches. Some state-of-art techniques were adopted in the analysis. A new formula containing sodium silicate was used for the similar material. Endoscope technique was used in the model test to log the crack propagating inside the tunnel. And hybrid discrete–continuous modeling was introduced to perform a sophisticated numerical investigation. Two small-scale model tests were carried out, in which the interaction of the tunnel with the fault rupture, the deformation pattern, and the strain evolution and crack propagation in the tunnel liner were observed. The model tests indicate that the failure of the tunnel mainly resulted by the faulting-induced circular cracks concentrated in the vicinity of the shear zone and longitudinal cracks at the passive side portion. Then, the hybrid DEM-FDM model was constructed and calibrated based on the experimental data, with which the response and mechanism of the tunnel subjected to strike-slip fault rupture were numerically investigated to identify the influences of some important factors. The longitudinal and transverse deformation profiles of the tunnel were found to be dominated by the rock mass condition and the buried depth of the tunnel. And the tunnel’s design factors have significant effects on the stress and failure mode of the liner. For a soft or thin tunnel liner, the failure zones were more concentrated. The tunnel would fail in a ‘shear’ mode. In contrast, for a hard or thick liner, the magnitude of the tensile strain is less, yet the tension failure area is larger. The tunnel would fail in a ‘squeeze’ mode. Based on the obtained results, suggestions on the design of tunnel liner against the strike-slip fault rupture were proposed.
... The slip rate is a very important kinematic parameter of active faults and an important index for evaluating the seismic risk of faults. It refers to the velocity of fault dislocation over a certain period of time and represents the long-term and average activity level of the fault (Zhang et al., 2013;Zhang et al., 2017). It can be used to quantitatively compare the relative activity of different fault zones or the same fault zone in different periods and is also a very important parameter for seismic risk evaluation. ...
Article
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The slip rate is a fundamental kinematic parameter of active faults. Traditional methods using fault scarps or trenches may produce inaccurate estimates of a fault's vertical slip rate. A normal fault's vertical slip rate requires constraints from the hanging wall and footwall. Here, the vertical slip rate at each measuring point along the fault was calculated by the joint constraints of terraces in the footwall and boreholes in the hanging wall. Nine measuring points were selected along the Sertengshan piedmont fault. The vertical slip rates of this fault since 65 and 12 ka were 0.74-1.81 and 0.86-2.28 mm/a, respectively. Four measuring points were selected along the Wulashan piedmont fault. The vertical slip rates of this fault since 60 and 12 ka were 2.14-3.11 and 1.84-2.91 mm/a, respectively. Seven measuring points were selected along the Daqingshan piedmont fault; the vertical slip rates were 2.5-3.88 and 1.78-2.83 mm/a since 58 and 11 ka, respectively. Analysis of the slip rates, the elapsed time since the last palaeoearthquake and the mean recurrence interval of palaeoearthquakes on each fault segment on the northern margin of the Hetao Basin suggests that the Langshankou and Hongqicun segments of the Sertengshan piedmont fault are at higher risk of earthquakes than the other segments. Among the fault segments of the Wulashan piedmont fault, the Baotou segment is at the highest seismic risk. The seismic risk of the Tuyouxi segment of the Daqingshan piedmont fault should not be ignored, and the Tuzuoxi, Bikeqi and Hohhot segments have high seismic risk. Based on the findings and a dynamic model of the formation and evolution of the Ordos block, it is concluded that the depositional centre of the Hetao Basin has tended to migrate from west to east. The vertical force generated by deep material movement is the dominant factor leading to a greater vertical slip rate in the eastern portion of the northern margin of the Hetao Basin. The modern stress field in the Hetao Basin results in an increase in the vertical slip rate of active faults from west to east along the northern margin of the basin.
... The basin is a large marine-continental depositional compound basin after experiencing multistage tectonic activities (Xu et al., 2013;Wu et al., 2018;He et al., 2019;Xu et al., 2021). After the initial continental crustal evolution in the Archean, the Tarim Craton was developed during the Proterozoic and Paleozoic by the accretion of the Kunlun, Qaidam, Tarim block, and the Central/South Tian Shan block (Charvet et al., 2007;Lin et al., 2013;Zhang C.-L et al., 2013;Zhang P. Z et al., 2013;Li et al., 2018), and by the extensional activities from the Neoproterozoic to Ordovician (Dong et al., 2016;Zhu et al., 2017;Ren et al., 2018;Wu et al., 2018). A lot of important basement structures such as the Bachu, Tanan, Tazhong, Tadong, Tabei, Kalpin, and Kuruk Tagh basement-cored uplifts were established during the late Proterozoic and the early Paleozoic (Gao and Fan, 2014;Tang et al., 2014;Lin et al., 2015;Liu et al., 2015;Zhu et al., 2017;Wu et al., 2018). ...
Article
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The property of the magnetic basement and the faults in the basement is significant for structural evolution, the Phanerozoic deposition, and oil resource exploration of the Tarim Basin. Based on the newly acquired aeromagnetic and industry seismic data, we mapped the distribution of basement faults by applying magnetic gradient-processing methods such as the horizontal gradient derivative, the first vertical derivative, the tilt derivative, and the upward continuation method. The dips of basement faults were confirmed and the susceptibilities of basement blocks were obtained by forward modeling of five profiles using the constraint of sedimentary strata depth and Moho topography. On the basis of comprehensive analysis of the magnetic anomalies, the distribution and inclination of basement faults, and susceptibilities differentiation obtained by forward modeling and field measurement, the property of the basement faults and their implication were discussed and interpreted. Our results show that the origin of the Central Highly Magnetic Anomaly Belt is highly magnetic Archean metamorphic rocks. The weakly magnetic Southeastern Domain and highly magnetic Central Tadong Domain assembled along the Tadong South Fault during the Paleoproterozoic. The Paleozoic Cherchen Fault is just an interior fault in the weakly magnetic Southeastern Domain although it presents a large vertical fault displacement. Considering the prominent variation of strikes of the Tadong North Fault system, and the moderately magnetic anomalies in the Northeastern Mangal Domain corresponding to the center of Neoproterozoic deposition, it is likely that the basement of the Northeastern Mangal Domain modified by the Neoproterozoic rifting could be originally the same as the basement of Central Highly Magnetic Anomaly Belt.
... As indicated inFig. 8, the main fractures identified in this paper are largely consistent with the ones previously identified by other people(Zhang et al. 2013). As seen inFig. ...
... mm/yr is accommodated by the hinterland active structures ( Figure 10). GPS measurements reveal that the crustal shortening rate across the eastern Tian Shan is~3-5 mm/yr [9,66]. Therefore, active structures within the range roughly accom-modate~28-45% of the total convergence across the segment of the eastern Tian Shan (86°-89°E). ...
Article
The deformation pattern and slip partitioning related to oblique underthrusting of the Tarim Basin in the eastern Tian Shan orogenic belt are not well understood because interior deformation images are lacking. The Baoertu fault is an E-W−striking, ∼350-km-long reactivated basement structure within the eastern Tian Shan. In this study, we quantify its late Quaternary activity based on interpretations of detailed high-resolution remote sensing images and field investigations. Three field observation sites along an ∼80-km-long fault segment indicate that the Baoertu fault is characterized by sinistral thrust faulting. Based on surveying of the displaced geomorphic surfaces with an unmanned drone and dating of the late Quaternary sediments using radiocarbon and optically stimulated luminescence (OSL) methods, we estimate a late Quaternary left-lateral, strike-slip rate of 1.87 ± 0.29 mm/yr and a N−S shortening rate of 0.26 ± 0.04 mm/yr for this fault. The lithospheric Baoertu fault acts as a decoupling zone and accommodates the left-lateral shearing caused by the oblique underthrusting of the Tarim Basin. In the eastern Tian Shan orogenic belt, the oblique convergence is partitioned into thrust faulting across the entire range and sinistral slip faulting on the high-dip basement structure within the orogen. This active faulting pattern in the eastern Tian Shan of sinistral shearing in the center and thrust faulting on both sides can be viewed as giant, crustal-scale positive flower structures.
... The uplifts of the Tibetan Plateau and neotectonic activities in the upper reach of the YR have not only significantly influenced river formations and geomorphological evolution but are also closely related to geological disasters in the basin (Peng et al., 2004;Xu et al., 2017). The northeastern Tibetan Plateau is characterized by strong tectonic deformations, densely distributed active faults, and frequent earthquakes (Wang, 2002;Zhang P Z et al., 2013;Lan et al., 2016). In these geological and tectonic backgrounds, the upper and middle reaches of the YR cut through the Jishi Gorge and continuously extended toward the interior of the plateau (Craddock et al., 2010), forming the typical basinmountain coupling system that can represent the macrotectonic pattern of the upper and middle reaches. ...
Article
The Yellow River Basin (YRB) is characterized by active geological and tectonic processes, rapid geomorphological evolution, and distinct climatic diversity. Correspondingly, major disasters in the YRB are characterized by varied types, extensive distributions, and sudden occurrences. In addition, major disasters in the YRB usually evolve into disaster chains that cause severe consequences. Therefore, major disasters in the YRB destroy ecologies and environments and influence geological and ecological safety in the basin. This paper systematically reviews research on geological and surface processes, major disaster effects, and risk mitigation in the YRB, discusses the trends and challenges of relevant research, analyzes the key scientific problems that need to be solved, and suggests prospects for future research based on the earth system science concept. Themes of research that should be focused on include geological, surface and climatic processes in the YRB and their interlinking disaster gestation mechanisms; formation mechanisms and disaster chain evolutions of giant landslides in the upper reach of the YRB; mechanisms and disaster chain effects of loess water-soil disasters in the middle reach of the YRB; occurrence patterns and amplifying effects of giant flood chains in the lower reach of the YRB; and risk mitigations of major disasters in the YRB. Key scientific problems that need to be solved are as follows: how to reveal the geological, surface and climatic processes that are coupled and interlinked with gestation mechanisms of major disasters; how to clarify the mutual feedback effects between major disasters and ecology; and how to develop a human-environmental harmony-based integrated risk mitigation system for major disasters. Prospects for future studies that follow the earth system science concept include the following: highlighting interdisciplinary research to reveal the interlinked disaster gestation mechanisms of the geology, surface and climate in the YRB in the past, present, and future; forming theories to clarify the regional patterns, dynamic mechanisms, and mutual-feedback effects between disaster chains and ecology in the YRB on land and in rivers in the region; solving technological bottlenecks to develop assessment models and mitigation theories for integrated risks in the YRB by following the human-environment harmony concept; and finally, establishing a demonstratable application pattern characterized by “whole-basin coverage” and “zonal controls”, thereby guaranteeing ecological and geological safety in the basin and providing scientific support for ecological conservation and high-quality development of the YRB.
... Since the late Quaternary, the Sichuan-Yunnan block has experienced strong tectonic movement and is one of the most seismically active areas within and surrounding the Tibetan Plateau ( Figure 1; Deng et al., 2003;X. Li et al., 2016;Luo et al., 2014;Wang, Ran, et al., 2017;Wang et al., 2013;Wang, Tian, & Liang, 2017;Wen et al., 2007Wen et al., , 2008Wen & Yi, 2003;Xu, Cheng, et al., 2003;Xu, Wen, et al., 2003;Zhang et al., 2013;Zhang, Wang, et al., 2003). ...
Article
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Intra‐block faults generally attract less attention because little slip occurs on them. However, some of them can host strong earthquakes and thus their faulting behaviors are also significant for assessing seismic risk and understanding crustal deformation patterns. The Xigeda fault is one of the intra‐block faults in the southeastern Tibetan Plateau and has generated two M > 6 earthquakes in the past 70 years. Nevertheless, little is known about its faulting behavior, seismic hazard, and tectonic role. Focusing on this problem, we conducted field investigations, trench excavations, and shallow seismic exploration to characterize its fault activity. Our work reveals that the Xigeda fault slips left‐laterally at a rate of 0.8–1.6 mm/yr with a thrust component through high‐resolution landforms measuring and sample dating. The paleoseismic investigations determine the latest surface rupturing event along the Xigeda fault occurred between 1580 CE and 1970 CE, which is further determined as the 1732 earthquake with a reevaluated magnitude of 7.0–7.5. Therefore, the Xigeda fault is confirmed to be active in the Holocene and can generate M ≥ 7.0 earthquakes. Moreover, the Xigeda fault, along with the Yuanmou fault, makes up the shortage of slip rates between the Anninghe and Zemuhe faults and plays an important role in partitioning the slip along the Xianshuihe‐Xiaojiang fault system and accommodating the crustal deformation in the Sichuan‐Yunnan block. Additionally, our work suggests a crustal deformation pattern for the southeastern Tibetan Plateau that most of the crustal deformation within tectonic blocks is still expressed by slipping along significant intra‐block faults.
... The Sichuan-Yunnan region, located toward the southeastern boundary of the Tibetan plateau, is one of the regions with severe tectonic and seismic activities in China ( Fig. 1) Zhang et al., 2013). Extrusion between the Eurasian and Indian plates forces the Tibetan plateau to continue to move in an east-south-southeast direction (Yin and Harrison, 2000), whereas the adjacent Huanan block is relatively stable and resists the escaping movement of the plateau as a rigid barrier (Zhang et al., 2010). ...
Article
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As one of the most seismically active regions in China, the Sichuan–Yunnan area is dominated by active faults and frequent strong earthquakes. Unexpected large earthquakes occurring in this area have caused substantial damage and casualties, necessitating comprehensive analysis of the reoccurrence patterns of strong earthquakes. This analysis was conducted using historical and instrumental earthquake records, and paleoearthquake data. Strong earthquakes occurring in the fault zones did not follow the characteristic earthquake distribution but instead migrated among the fault zones of one active block, resembling typical continental earthquake characteristics. Thus, it would be more appropriate to discuss the reoccurrence of earthquakes for an entire active block rather than a single fault. These results might help in improving reoccurrence models in probabilistic seismic hazard assessments.
... The NNE-trending convergence and compression of the Indian plate toward the Eurasian plate causes the crustal material in the central Tibetan Plateau to move eastward and westward [38][39][40]. The plateau is blocked by the rigid Sichuan Basin to the east, causing the crustal material in the southeastern part of the plateau to move southeastward along the XXFS (Figure 1 [41,42]). The XJFZ is an important part of the XXFS. ...
Article
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The temporal slip behavior of a fault from displaced landforms when there are no chronological data remains poorly understood. The southern segment of the Xiaojiang fault zone (XJFZ) plays an important role in accommodating the lateral extrusion of the SE Tibetan plateau. However, there are few reports on the evolution of the offset landforms and slip behavior of the fault due to the dense vegetation in the region. Here, offset landforms along the Jianshui fault (JSF) in the southern segment of the XJFZ are systematically interpreted and measured using high-resolution satellite imagery, field investigations, and airborne lidar. The risers on the right banks of three stream channels feature similar left-lateral offset characteristics near the town of Dongshanzhai. The left-lateral offsets consist of multiple inflections produced by seismic events, and the offset of each event is similar. These inflections are distributed downstream in a stair-stepped manner. The newly formed inflections are located close to the fault, and the earlier formed ones are eroded by flowing water and migrate downstream. The difference between the amount of downstream erosion of two adjacent inflections varies. Assuming the stream’s long-term erosion rate remains steady, the estimated time intervals between seismic events are different. Combined with the cumulative offset probability density calculation for 92 offsets, the JSF is considered to show a nonperiodic characteristic earthquake recurrence pattern. We also propose a multistage offset evolution model of the stream channel riser. This provides a new way to analyze the seismic recurrence pattern of the fault over a relative time scale.
... mm/yr is accommodated by the hinterland active structures ( Figure 10). GPS measurements reveal that the crustal shortening rate across the eastern Tian Shan is~3-5 mm/yr [9,66]. Therefore, active structures within the range roughly accom-modate~28-45% of the total convergence across the segment of the eastern Tian Shan (86°-89°E). ...
Article
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Investigation on the kinematics and deformation rates about active fault interior of the Tian Shan can provide significant information for strengthening our understanding on the present tectonic evolution of this range. The Baoertu Fault (BETF) is a major E-W striking active structure within the eastern Tian Shan and separates the south and central Tian Shan. But its kinematics and slip rates in the late Quaternary have never been systematically reported before. Based on interpretations of remote sensing images, drone photography, and detailed field investigations, we propose that the BETF is characterized by left-lateral strike-slip faulting with a thrust component and provides the first late Pleistocene slip rate for this fault. At the northern margin of the Kumishi Basin, combining offset reconstructions of displaced alluvial fan surfaces with the terrestrial cosmogenic nuclide (TCN) exposure age dating, we calculate an average sinistral slip rate of 0.65±0.16 mm/yr and average vertical slip rate of 0.07±0.01 mm/yr for the BETF since 95-106 ka. The differential movement eastward between the central Tian Shan block and Yanqi-Kumishi Basin block is likely the dominant driver of the left-lateral slip of the BETF. Synthesizing other quantitative data in eastern Tian Shan, we suggest that the hinterland active faults or folds, including the BEFT, roughly accommodate ~28-45% of the total N-S convergence across the eastern Tian Shan.
... The fault system acts as the eastern boundary of the Chuan-Dian block on the southeastern margin of the Tibetan Plateau and plays a key role in accommodating the lateral extrusion of the block and clockwise rotation around the eastern Himalayan syntaxis (e.g., [1][2][3][4][5]). The tectonic deformation and seismicity of the XJFZ have been intense since the late Quaternary, and the fault zone forms a vital part of the north-south seismic belt [6][7][8]. The XJFZ is approxi-mately 400 km long and can be generally divided into three segments (Figure 1(a), [9][10][11]). ...
Article
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The Xiaojiang fault zone (XJFZ) is an important part of the Xianshuihe-Xiaojiang fault system, acting as the eastern boundary of the Chuan-Dian block on the southeastern margin of the Tibetan Plateau and accommodating the lateral extrusion of the block. The faulting activity and paleoseismic history on the southern segment of the XJFZ remain poorly understood. Here, trench excavations and radiocarbon dating revealed that four recent surface-rupturing paleoearthquakes have occurred on the Jianshui fault (JSF) in the southern segment of the XJFZ since ~15370 yr BP. The ages of these events, labeled E4-E1 from oldest to youngest, are limited to the following time ranges: 15360-12755, 10845-6900, 1455-670, and 635-145 yr BP, respectively. The most recent event E1 was most likely the 1606 Jianshui earthquake. These events appear to occur unregularly in time. The time interval between the last two events is 726±235 yr, and the average recurrence interval for all four events is 4589±3132 yr. The deformed strata show that the JSF is characterized kinematically by transtension, which likely respond to the apparent change in the direction of clockwise rotation of the Chuan-Dian block around the eastern Himalayan syntaxis. Combined with the analysis of the neighboring NW-striking faults, our study suggests that the south-southeastward motion of the Chuan-Dian block is likely to be firstly accommodated in part by the right-lateral shear and dip-slip motions of the Qujiang and Shiping faults and continues across the Red River fault zone, then is transmitted southward along the Dien Bien Phu fault. Therefore, the southern segment of the XJFZ plays a dominant role in the tectonic deformation of the southeastern Chuan-Dian block, with a high seismic hazard.
... Paleoearthquake refers to the earthquake event that has been recorded geologically while unrecorded in human history, whose recurrence interval ranges from hundreds to tens of thousands of years. Through studying paleoearthquakes, researchers can understand more about the mechanism of earthquakes, and make effective predictions to reduce the loss of life and property (Zhang et al. 2013;Peng et al. 2017). ...
Article
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Paleoseismic offsets are important parameters for evaluating fault activity. With the development and popularization of unmanned aerial vehicles (UAVs) and structure-from-motion (SfM) photogrammetry, more and more low-cost mini-UAVs have been used for geoscience studies like active faults and paleoearthquakes. In this study, we take the Gebi ridge in the middle of the Altyn Tagh fault (ATF) in western China as an example of using the control-free images acquired by a mini-UAV and SfM to measure paleoseismic offsets. The measurement accuracies of the control-free images acquired by a mini-UAV were evaluated, and then the horizontal offsets of the land surface caused by paleoearthquakes were measured. After comparing the total number and anomalies of paleoearthquake events identified by UAV-based photos with those revealed by geological trenches nearby, the following conclusions can be drawn. (1) Although the absolute positioning accuracy of the control-free image from the mini-UAV and SfM is poor, the accuracy of relative horizontal measurement is acceptable. (2) Without the help of ground control points (GCPs), the accuracy of relative vertical measurement for aerial images is not sufficient to measure vertical offset. (3) Oblique photography can improve not only the accuracy of paleoseismic landform mapping but also flight safety. (4) Up to 11 paleoearthquakes have been identified through paleoseismic offset measurements using control-free images in the study area. And both the total number and the anomalies of paleoearthquakes are consistent with the geological evidence in nearby geological trenches. By taking into account the above factors, it can be concluded that it is feasible to measure the horizontal offset of the land surface caused by paleoearthquakes using control-free images from mini-UAVs and SfM.
... For instance, the Altyn Tagh fault zone, Haiyuan fault zone, the North Tien Shan fault zone, the Kunlun fault zone, the Xiaojiang fault zone, the Red River fault zone and the Shan Xi fault zone, and the Zhang-Bo fault zone are all located in the area with high difference value in Figure 8. The strong earthquake is mainly along the vast fault zone which often constitutes a block boundary [47]. This shows that the fault area has a large strain difference, which affects the occurrence of earthquakes. ...
Article
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We used the interpolation method of two-dimensional vector velocity field data based on Green’s function to conduct coupled interpolation with a Poisson’s ratio of 0.5 for 1966 horizontal velocity field data from 1999 to 2017 and obtained the uniform velocity field and strain rate field with a grid of 1°. The main results are as follows: the eastern Himalayan structure as the center, the eastern Lhasa block, the eastern Qiangtang block, the Sichuan-Yunnan block, and the Burma block form a strong deformation rate zone of continuous deformation in the fan-shaped region, which has been a strong deformation rate zone for earthquakes of magnitude 7 or higher in continental China since 1963. Besides, the eastward movement of crustal material in the Tibetan Plateau is blocked by the stable South China block. Therefore, the direction of crustal material movement is deflected, which gradually forms a clockwise rotation motion system centered on the eastern Himalayan structure. Finally, our research shows that the influencing factors of strong earthquakes include velocity change, non-uniform strain distribution, accumulation of larger strain, and the difference of the second strain rate invariant. Strong earthquakes are closely related to the difference in energy accumulation in space.
... Geological data, gravity anomaly, satellite gravity full-tensor gradient and other boundary 314 identification methods are used for boundary identification in East Asia, as shown in Fig. 8. As 315 indicated in Fig. 8, the main fractures identified in this paper are largely consistent with the ones 316 previously identified by other people (Zhang et al. 2013). China is located in the southeast of the 317 Plate, Philippine Plate and Pacific Plate. ...
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China is located in the southeast of the Eurasian Plate and is subject to the effects of subducting, squeezing and collision by the Pacific Plate to the east, Philippine Plate to the southeast and Indian Ocean Plate to the southwest. It has exceptional geotectonic structure. Based on the satellite gravity data with high precision, high resolution and ample geophysical information, combined with geological data, by using satellite gravity potential field and its full tensor gradient, this paper studies the distribution characteristics of gravity anomalies and the identification of tectonic boundaries in China and surrounding regions. Results suggest that the Bouguer gravity anomaly in eastern China reduces gradually from east to west, mostly in the direction of NNE; in the western, it reduces gradually in a wave mode from north to south, mainly in the directions of NW and NWW. In general, the stress field reduces gradually from west to east, and the tectonic of stress field in western China is complex. The maximum principal compressive stress in Xinjiang exists in SN direction and that in Qinghai-Tibet Plateau mostly changes gradually from NNE to SSE; the change in eastern China is relatively simple, and the maximum principal compressive stress direction gradually changes from NE to WE and then to SE. In addition to the above study results, by comprehensively referencing the previous studies by other people and by using the boundary identification methods based on the satellite gravity full-tensor gradient data and its combinations, we update the extension route of Red River fault zone and deduce the tectonic unit boundary between the North China and South China active tectonic block regions. This paper identifies in China and surrounding regions 6 primary active tectonic blocks, 22 secondary active tectonic blocks, 3 tertiary active tectonic blocks and the 20 active tectonic block boundary zones constituted of deformation belts and active tectonic belts with various geometric structures and width variations. The results of this study can improve the understanding of gravity anomalies and boundary structures in China and surrounding regions, and provide certain geophysical supports for geological structure analysis and crustal dynamic process.
... The South China Block in southeastern China is an important tectonic unit of the East Asian continent bounded by the Qinling-Dabie Fold System on the north, the Bayan Har Block on the northwest and the Pacific Plate on the southeast (Zhang et al., 2013). It is generally accepted that the South China Block was formed by the amalgamation of the Yangtze Craton in the northwest and the South China Fold System in the southeast during the early Neoproterozoic (Zhu et al., 2005) (Figure 1). ...
Article
The detailed lithospheric structure of South China is the basis for the understanding of tectonic processes of eastern China. Specifically, two essential issues in the study of lithospheric structure are the thermal and compositional structures, which are usually derived from either geophysical or geochemical observations. However, inversions from single geophysical or geochemical datasets have certain limitations, making it necessary to develop joint inversions of geophysical, geochemical and petrological datasets. In this paper, through thermodynamic simulation and probabilistic inversion, we inverted multiple datasets including topography, geoid height, surface heat flow and surface wave dispersion curves for the 3D lithospheric thermal and compositional structure of South China. The results reveal a thin (< 100 km) and flat LAB beneath the South China Fold System Block and the lower Yangtze Craton. Also, we found that the lithospheric mantle is primarily composed of saturated peridotite, indicating that the ancient refractory lithospheric mantle has been replaced by new materials. The dominant dynamic mechanism for lithospheric thinning in eastern South China may be the flat subduction of ancient Pacific slab, while thermal erosion may have also played a significant role. In contrast, the LAB depth beneath the Sichuan Basin is much thicker (> 200 km), suggesting that the thick and cold craton lithospheric roots are retained. There may exist a discontinuous interface beneath the Sichuan Basin, with the saturated lower layer thicker than the refractory upper layer. As a result, the lithospheric mantle of the Sichuan Basin and surrounding regions is mainly composed of saturated and transitional peridotite.
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The 21 May 2021 Mw 7.4 Maduo earthquake ruptured a 170 km long immature strike-slip fault within the eastern Tibetan plateau. Based on pixel correlation of pre- and postevent Sentinel-2 optical satellite images (band 8; pixel = 10 m), we determine the coseismic horizontal displacement and deformation-zone width at the surface. These results, compared with the on-fault slip from geological measurements, document that <20% of the fault displacement is localized on the fault plane, whereas as high as >80% of the fault displacement occurred as off-fault deformation (OFD), over a mean deformation-zone width of 835 m (ranging from 60 to 1670 m). The OFD% of the Maduo earthquake is significantly larger than the OFD% (28%–64%) of all other (eight in total) previously documented earthquakes occurring on immature strike-slip faults, amongst which five earthquake faults have a structural maturity (cumulative displacement) even lower than the Maduo earthquake fault. These observations may be explained by that (1) the fault maturity is not the only factor controlling the behavior of OFD or the degree of strain localization during an earthquake, or that (2) the calculated OFD includes some elastic deformation due to fault slip reduction in the shallow depth. Our results have an implication that the seismic hazard assessment of immature strike-slip faults is more challenging than previously thought.
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The slip rates of active faults in the northeastern Tibetan Plateau (NETP) require clarification to understand the lateral expansion of the Tibetan Plateau and assess the seismic hazards in this region. To obtain the continuous slip rates of active faults at the NETP, we constructed a three-dimensional (3D) numerical geomechanics model that includes a complex 3D fault system. The model also accounts for the physical rock properties, gravity fields, fault friction coefficients, initial stress, and boundary conditions. Following this, we present the long-term kinematics of NETP based on the horizontal and vertical velocities and fault slip rates acquired from the model. The fault kinematic characteristics indicate that the Laohushan, middle–southern Liupanshan, and Guguan–Baoji faults, as well as the junction area of the Maxianshan and Zhuanglanghe faults, are potential hazard areas for strong earthquakes. However, as these faults are currently in the stress accumulation stage, they are unlikely to cause a strong earthquake in the short term. In contrast, it is likely that the Jinqiangshan–Maomaoshan fault will generate a earthquake with a surface-wave magnitude (MS) of 7.1–7.3 in the coming decades. In addition, the velocity profiles across the NETP imply that the plate rotation is the primary deformation mechanism of the NETP even though the intra-block straining and faulting are non-negligible.
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The uplift of the Qinghai–Tibet Plateau (TP) strongly influences climate change, both regionally and globally. Surface observation data from this region have limited coverage and are difficult to obtain. Consequently, the vertical crustal deformation velocity (VCDV) distribution of the TP is poorly constrained. In this study, the VCDV from the TP was inverted by using data from the gravity recovery and climate experiment (GRACE). We were able to obtain the vertical crustal movement by deducting the hydrological factors, based on the assumption that the gravity signal detected by GRACE is mainly composed of hydrological factors and vertical crustal movement. From the vertical crustal movement, we inverted the distribution of the VCDV across the TP. The results showed that the VCDV of the southern, eastern, and northern TP is ~1.1 mm/a, ~0.5 mm/a, and −0.1 mm/a, respectively, whereas that of the region between the Qilian Haiyuan Fault and the Kunlun Fault is ~0.0 mm/a. These results are consistent with the distribution of crustal deformation, thrust earthquakes and faults, and regional lithospheric activity. The hydrology, crustal thickness, and topographic factors did not change the overall distribution of the VCDV across the TP. The influence of hydrological factors is marked, with the maximum differences being approximately −0.4 mm/a in the northwest and 1.0 mm/a in the central area. The results of this study are significant for understanding the kinematics of the TP.
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Based on field investigations, interpretations of high‐resolution UAV images, and analyses of available InSAR data, we mapped the fault geometry and surface ruptures of the 2021 Mw 7.4 Maduo earthquake that occurred on a low‐activity strike‐slip fault within the Tibetan Plateau. The results indicate that (a) the earthquake activated a fault that is ∼161 km long and has complicated structural geometry; (b) the surface rupture occurs over a distance of 148 km, but is separated into three distinct segments by two large gaps (38 and 20 km, respectively); (c) within the surface‐rupture segments, the horizontal and vertical displacements are typically 0.2–2.6 m (much lower than the InSAR‐based slip maximum of 2–6 m at depth) and ≤0.4 m, respectively. The two large gaps of the Maduo surface rupture represent the two largest surface‐rupture discontinuities of strike‐slip earthquakes ever documented, and coincide with structurally complicated fault portions and near‐surface soft sediments.
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On August 8, 2017, an MW 6.5 earthquake occurred in Jiuzhaigou County, Sichuan Province, China, on the eastern margin of the Qinghai–Tibet Plateau. This study investigates the coseismic deformation field and fault model with ascending and descending Sentinel-1 synthetic aperture radar (SAR) images, aftershock distribution, and elastic half-space dislocation model. The regional fault slip pattern is then quantitatively examined using the boundary element method. The results show that the ascending and descending interferometric synthetic aperture radar (InSAR) coseismic deformation fields display an overall NNW–SSE trend, with more significant deformation on the southwest side of the fault. The coseismic fault geometry is divided into NW and SE sub-faults with strikes of 162.1° and 149.3°, respectively. The coseismic fault slip is dominated by a left-lateral strike-slip movement with an average rake of −2.31°, mainly occurring at a depth of 0–13.04 km with a shape of an approximately inverted triangle. The fault slip features two peak slip zones, with a maximum of 1.39 m. The total seismic moment is 6.34 × 10¹⁸ N m (MW 6.47). The boundary element calculation quantitatively indicates that the regional fault slip pattern may be mainly attributable to the changing strike and dip. The strike changes from NNW–SSE to nearly NS direction, and the dip gradually decreases from the Jiuzhaigou earthquake fault in the north to the Huya fault in the south. With these characteristics, the Huya and the Jiuzhaigou earthquake faults form the eastern boundary of the Minshan uplift zone and accommodate the accumulated deformation.
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At the beginning of the 21st century, the ‘active tectonic block model’, described by hierarchical crustal tectonic blocks, was proposed to explain the distribution of continental earthquakes in China. The blocks, as well as the block boundary zones, were determined by geological, geophysical, and geodetic observations. The model, indicating that large earthquakes, especially great earthquakes, occur mainly in the boundary zones, plays an important role in seismic hazard assessment and earthquake forecast in China. The model has been tested by the seismicity in continental China in the past 20 years. Meanwhile, with new data accumulating and new technology emerging, it is possible to update the model into a new version, e.g., from 2D to 3D by considering deep structures such as crustal channel flow, and from a kinematic model to a dynamic one by computational geodynamics. The updated model could also be applied to broader continental regions for international collaborative and comparative studies.
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The Litang fault is a left-lateral secondary shear zone in the Sichuan-Yunnan active block that accommodates the tectonic deformation associated with the eastward extrusion of the upper crust of the Tibetan Plateau. Based on 1: 50 000 geological mapping of active faults, the Litang fault consists of three geometric segments, the Cuopuhu, Damaoyaba, and Litang segments, in the west of Litang, which are divided by the of Haizi Mountain uplift and the wide-angle bending and branching of the fault near Jinchanggou. This study also identifies the surface rupture of the A.D. 1890 earthquake, which is distributed intermittently along the ∼28 km long Damaoyaba segments and ∼25 km long Litang segments. The maximum horizontal displacement is 4.1 m along Damaoyaba segments, and 4 m along Litang segments. The rupture involves typical left-lateral shear movement. The two ruptures are divided by discontinuous segments or gaps that are ∼18 km long; thus, the total surface rupture is approximately 71 km long. The estimated moment magnitude was Mw7.3±0.1. A comprehensive analysis of data obtained from 5 trenches excavated along the Damaoyaba and Litang segments and the trench data by Xu et al. (2005) identifies age constraints of the 4 most recent paleoseimic events occurred B.C. 1468±54–1340±25, B.C. 52±25–A.D. 76±47, A.D. 1115±90, and A.D. 1890, respectively. The recurrence intervals are 1 415±80, 1 104±104, and 775±90 a, which are consistent with quasi-periodic earthquake recurrence behavior. The average recurrence interval is 1 098±112 a.
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The Liupanshan Basin constitutes a major portion of the northern North-South tectonic belt. The Lower Cretaceous strata in the Liupanshan Basin recorded the tectono-sedimentary evolution processes of this area and are pivotal for understanding the original sedimentary appearance of the Liupanshan Basin. In this work, we present a study of provenance and tectono-sedimentary evolution of the Liupanshan Basin during the Early Cretaceous. Integrated-paleocurrent directions, gravel clast compositions, and detrital zircon U-Pb isotopic analysis of the Lower Cretaceous Sanqiao and Heshangpu formations were applied to determine the provenance. The gravel clast compositions of Sanqiao Formation conglomerates (mainly including magmatic rocks, metamorphic rocks and limestones) display various features in different places, revealing different rock components of source areas. The paleocurrent directions of the Sanqiao and Heshangpu formations suggest that the sediments were transported from the basin margin to the center. Detrital zircons of two samples from the Huoshizhai Section (northwestern Liupanshan Basin) yield a dominant unimodal distribution from 420 to 500 Ma, suggesting a single-sourced provenance. Based on the above analyses, comparing to the magmatic records in the Qilian-Qinling orogenic belt, the detritus of the Sanqiao and Heshangpu formations were mainly from the proximal metamorphic and magmatic rocks of the Qilian-Qinling orogenic belt and the limestones of the archaic uplift. Combined with sedimentary characteristics, we concluded that the Liupanshan Basin experienced multi-stage evolution history: (1) the early rifting extension stage (Sanqiao Period), (2) the middle spanning and depression stage (Heshangpu-Early Naijiahe Period), and (3) the late extinction stage (Late Naijiahe Period). The evolution of Liupanshan Basin is closely related to that of Ordos Basin and it is further associated with tectonic transition of the northern North-South tectonic belt.
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The Xianshuihe Fault Belt (XSF), along which the syntectonic Zheduoshan batholith was emplaced, has great significance for the reconstruction of the tectonic framework in the eastern margin of the Tibetan Plateau. In this contribution, formation process and evolution of the XSF are discussed based on the structural deformation in the field and the geochronology of Zheduoshan batholith. The results show that the XSF current arc‐shaped protrusion to the north‐east probably was formed by a fracture of the clockwise rotation compression that extended northward to the periphery with the eastern Himalayan tectonic syntaxis as the centre. It is a complex fault belt formed by the superposition of multi‐stage structures. In the early‐stage formation and evolution of the XSF, the Oligocene‐Miocene migmatite zone and Miocene granites of the Zheduoshan batholith were emplaced. Among them, the lower limit of the XSF's initial activity time was not less than 47 Ma that was limited by the Zircon U–Pb geochronology of migmatite zone formed under the compression system. During the emplacement of Miocene granites, the XSF underwent a process from compression to sinistral strike‐slip, and the geochronology indicates that the onset of the XSF sinistral strike slip should not be less than 14 Ma. After syntectic magmatism, the XSF also experienced the shear deformation (from ductile to brittle) with sinistral kinematics. 40Ar‐39Argeochronology results show that the ductile shear deformation mainly occurred around 5.5–3.2 Ma and accompanied a staged and differential uplift from north to south. It extended to the south along the weak crustal zone of Anninghe, Daliangshan, Xiaojiang, and other faults, forming the Xianshuihe–Anninghe–Xiaojiang sinistral strike‐slip fault system on the eastern margin of the Tibetan Plateau, and large‐scale sinistral strike slip began around 5 Ma. Our new insights lay a foundation for understanding and dissecting the formation and evolution of the Tibetan Plateau eastern margin.
Chapter
In order to estimate the velocity results of crustal movement in Southwest China, the coordinate time series of 54 GNSS fiducial stations of CMONOC in the area from 2011 to 2018, are selected in this paper. The velocities and uncertainties about the GNSS coordinate time series are obtained and compared by two methods, i.e. Maximum Likelihood Estimation (MLE) and Median Interannual Difference Adjusted for Skewness (MIDAS). And the experimental results suggest that the area of Southwest China has a trend of southeast-ward movement in the horizontal direction under the framework of ITRF2014. The average velocity in the E direction is 34.44 ± 0.25 mm/a, and the mean value in the N direction is −12.26 ± 0.19 mm/a, the results are obtained by the MLE method under the optimal noise model of each station. While the corresponding results of the MIDAS method in the E and N directions are 34.41 ± 0.24 mm/a, −12.33 ± 0.20 mm/a, respectively. In the U direction, the velocity uncertainty of each station is large, the stations differ widely in movement direction and velocity magnitude. Furthermore, the results between the MLE method and the MIDAS method are slightly different in the U direction. In general, the results obtained by the two methods are not much different, the MIDAS method is resistant to offsets and seasonality, with fast computation speed, and this approach is more robust than the MLE approach.
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