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Article

Structural Deformation Style and Seismic Potential of the Maoyaba Fault, Southeastern Margin of the Tibet Plateau

by
Xianbing Zhang
1,2,3,
Ning Zhong
1,2,*,
Xiao Yu
1,2,4,
Guifang Yang
3 and
Haibing Li
5
1
Key Laboratory of Active Tectonics and Geological Safety, Ministry of Natural Resources, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
2
Research Center of Neotectonism and Crustal Stability, China Geological Survey, Beijing 100081, China
3
School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
4
School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
5
Key Laboratory of Deep-Earth Dynamics, Ministry of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2025, 17(7), 1288; https://doi.org/10.3390/rs17071288
Submission received: 14 February 2025 / Revised: 15 March 2025 / Accepted: 17 March 2025 / Published: 4 April 2025
(This article belongs to the Special Issue Advances in Geological Hazard Characterization and Assessment: Merging Remote Sensing with Direct Surveys)
Browse Figures
Versions Notes

Abstract

:
The southeastern margin of the Tibet Plateau represents one of the most seismically active zones in China and serves as a natural laboratory for investigating the uplift dynamics and lateral expansion mechanisms of the plateau. The Litang fault zone (LTFZ) lies within the northwest Sichuan sub-block on the southeastern margin of the Tibet Plateau, running almost parallel to the Xianshuihe fault zone and forming a V-shaped conjugate structure system with the Batang fault zone (BTFZ). The Maoyaba fault (MYBF) is a significant component of the northwestern part of the LTFZ, exhibiting activity in the late Quaternary. It triggered the ancient Luanshibao landslide and caused the Litang earthquake in 1729 AD, demonstrating intense seismic activity. Employing high-resolution remote sensing interpretation, field surveys, UAV photogrammetry, and UAV LiDAR, this study further examines the geometric distribution and kinematic properties of the MYBF, as well as paleoearthquake events recorded by the fault scarps. Combined with the geometric distribution and kinematic properties of the Hagala fault (HGLF) and Zimeihu fault (ZMHF), this study discusses the late Quaternary structural deformation style and seismic potential of the MYBF. The MYBF could produce earthquakes of approximately Mw 6.7 ± 0.3, with an average co-seismic slip of about 0.68 m and an average recurrence interval of strong earthquakes since the late Quaternary ranging from 0.9 to 1.1 ky. The likelihood of surface rupture earthquakes occurring in the near future is low; however, the expansion of the HGLF could induce moderate to strong earthquakes in the MYB area. The variation in the local tectonic stress field, which is influenced by the Litang–Batang V-shaped structure system and lithological differences, results in the formation of an extensional horsetail structure in the northwestern segment of the LTFZ. Both the HGLF and ZMHF remain active faults. Under the influence of nearly north–south tensile stress, these faults and the Litang–Batang V-shaped structure system collectively regulate the movement of regional crustal material.

1. Introduction

The southeastern margin of the Tibet Plateau has developed a complex fault system and experiences frequent strong earthquakes [1,2]. It is located in the oblique convergence zone between India and Eurasia and serves as a key area for regulating and absorbing the lateral extrusion/extension of the plateau [1,2]. It is also an ideal experimental field for testing the evolution mechanism model of the Tibet Plateau. The Litang fault zone (LTFZ) is situated on the southeastern margin of the Tibet Plateau and runs almost parallel to the Xianshuihe fault zone (Figure 1a,b). The LTFZ is a significant active fault zone accommodating material extrusion from the Tibet Plateau to the southeast [3,4,5]. The Maoyaba fault (MYBF) is a branch fault northwest of the LTFZ. The MYBF has well-developed faulted landforms, is highly active in the late Quaternary [3,5,6], and is considered the seismogenic fault of the 1729 AD Litang earthquake [7]. The Luanshibao landslide in the Maoyaba (MYB) basin has attracted considerable attention, as its cause can be related to the strong earthquake triggered by the MYBF at 5.2 ± 0.2 ky [8]. At present, unstable slopes are present in the Piedmont of the MYB basin, and fault activity can further affect slope stability [9,10]. The Sichuan–Tibet transportation corridor, currently under construction, passes through the highly active LTFZ, posing risks related to strong earthquakes and landslide geological disasters [11,12,13]. Therefore, studying the late Quaternary activity of the MYBF is of great significance for understanding the structural deformation mechanisms of the southeastern margin of the Tibet Plateau and ensuring the safe operation of major national projects.
There are differing views on the MYBF’s late Quaternary activity. First, previous studies have varied interpretations of the geometric structure and kinematic characteristics of the MYBF. Some studies indicate that the fault is primarily characterized by vertical movement [5], whereas others argue that it predominantly exhibits left-lateral strike–slip motion [3,6,7]. The segmented kinematic characteristics of the MYBF remain insufficiently studied. Second, paleoearthquakes on the MYBF, as revealed by previous trench investigations, are mainly dated to the Holocene [6,7,15]. The lack of a longer paleoearthquake history affects the assessment of its seismic potential. Third, existing studies do not sufficiently discuss the late Quaternary structural deformation characteristics and formation mechanisms of the MYBF. To investigate the late Quaternary deformation style and seismic potential of the MYBF, this study employed high-resolution remote sensing interpretation, field surveys, unmanned aerial vehicle (UAV) photogrammetry, and UAV LiDAR scanning methods. These methods systematically constrain the geometric kinematics of the MYBF, Hagala fault (HGLF), and Zimeihu fault (ZMHF), as well as the paleoearthquakes recorded by the MYBF scarps. Notably, UAV photogrammetry and LiDAR scanning can generate decimeter resolution DEM, which can provide key spatial constraints for the geometric kinematic characteristics and offsets measurement of the MYBF. This study aims to investigate the structural deformation style of the MYBF and provide scientific support for hazard risk assessment of active fault zones in national major projects, such as the Sichuan–Tibet transport corridor.

2. Geological Setting

Several active blocks are mainly developed on the southeastern margin of the Tibet Plateau, including the Ma’erkang block, the Sichuan–Yunnan block, the Baoshan–Pu’er block, and the Myitkyina–Ximeng block [14,16]. The Sichuan–Yunnan block is mainly cut and enclosed by the Ganzi–Yushu fault zone, Xianshuihe fault zone (XSHFZ), Xiaojiang fault zone, Honghe fault zone, and Jinshajiang fault zone [14]. Taking the Lijiang–Xiaojinhe fault zone as the boundary, the Sichuan–Yunnan block can be further divided into two sub-blocks: Northwestern Sichuan and Central Yunnan (Figure 1a; [14]). As the eastern boundary of the Sichuan–Yunnan block, the XSHFZ maintains a left-lateral strike–slip rate of up to 8–13.4 mm/a [17,18]. The overall strike of the XSHFZ is 130–170°, presenting an arc convex towards the NE direction (Figure 1b). The Batang fault zone (BTFZ) is one of the northwest boundary fault zones of the northwest Sichuan sub-block, with an NNE orientation [14,19]. Since the late Quaternary, the BTFZ has been highly active, with a right-lateral slip rate of about 2–4 mm/a [20], and it is the seismogenic structure of the 1870 AD Batang M71/4 earthquake [19].
The LTFZ is an active fault zone within the northwest Sichuan sub-block [3], dominated by the left-lateral strike–slip movement, with a slip rate of about 2.3–5.0 mm/a since the late Quaternary [3,4,5,21]. The LTFZ is highly active and triggered the Litang M71/4 earthquake in 1948 AD [22]. From NW to SE, the LTFZ is mainly composed of the Cuopuhu fault (CPHF), the MYBF, the Gaocheng fault (GCF), the Kangga–Dewu fault (KDF), and the Shawan fault (SWF) [3,5,21], in addition to the Zheqingma fault (ZQMF) and Lamagou fault (LMGF) between the Litang and MYB basins (Figure 1c). In terms of geometric kinematics, the LTFZ and BTFZ form a V-shaped conjugate strike–slip fault system with an angle of about 80° and facing south [4,23,24]. In addition to these two important seismogenic structures (LTFZ and BTFZ), moderate to strong earthquakes frequently occur in the northern foothills of the Genie Mountains, on the southwest side of the MYB basin (Figure 1c). The region experienced the Batang strong earthquake swarm in 1989 AD, with four earthquakes of Ms6.0–6.7, four earthquakes of Ms5.0–5.9, and 19600 earthquakes of Ms1.0 or above occurring within six months, causing severe losses in the Litang–Batang region [4].
The MYB area is located in the southern part of the Yidun island arc, where Triassic sedimentary and metamorphic rocks are well developed (Figure 2a). The main rock bodies in the MYB area are Indosinian granites and diorites, with the Ganzi–Litang ophiolite mélange to the east (Figure 2a). The Quaternary deposits are mainly found in the MYB basin and the southern foot of Haizi Mountain. The MYB basin is approximately a parallelogram, about 20 km long from east to west and about 9 km wide from north to south (Figure 2a). The basin is higher in the northwest and lower in the southeast, with an average altitude of about 4000 m. The Litang River originates from the northern foot of the Genie Mountain, flows through the MYB, Litang, Kangga, and Mula basins, and enters the deep valley south of Mula (Figure 1c). The Litang River generally exhibits three levels of river terraces within the MYB basin, with heights above the river level of 1–2 m, 2–8 m, and 6–12 m, respectively (Figure 2c,d). Large late Pleistocene alluvial fans developed in the southern part of the MYB basin (Figure 2a), constituting the T3 terrace of the Litang River and its tributaries. Outwash fans are well developed on the northeastern margin of the MYB basin, having mainly formed since the H2 event [5]. Well-developed moraines are present at the southern foot of Haizi Mountain, with the exposure age of cosmogenic nuclides on moraine ridges 15 km from the modern glacier, ranging between 15 and 22 ky [25].

3. Methods and Materials

First, Map World, 21st Century AT, Google Earth, and Copernicus DEM were utilized to interpret high-resolution remote sensing. Map World, 21st Century AT, and Google Earth are sub-meter optical satellite remote sensing images that complement and corroborate each other. The Copernicus DEM, released by the European Space Agency, has a resolution of 30 m, an absolute elevation accuracy of LE90 better than 4 m, and an absolute plane accuracy of CE90 better than 6 m [26]. Compared to other open-source DEMs, the Copernicus DEM presents the most detailed topographic information [27,28], and provides quantitative data such as elevation and slope for optical remote sensing images.
Second, based on the observation points obtained from remote sensing interpretation, a field investigation was conducted using the tracing and crossing method to verify the geomorphic phenomena. For the observation points of typical fault landforms, a small quadrotor UAV (model: DJI-Phantom3 Professional) was used in conjunction with photogrammetry and structure-from-motion (SfM) technology [29] to generate high-resolution DEMs over a small area. In addition, a large six-rotor UAV (model: FEIMA-D20), equipped with LiDAR (model: DV-LIDAR20), was utilized to obtain a large-scale high-resolution DEM at the northeastern margin of the MYB basin (Figure 3a). The basic parameters of the DEM (data acquired in June and September 2021 and May 2023) are shown in Table 1, with a resolution of approximately 0.2 m.
Third, based on the high-resolution DEM, the Spatial Analyst tool in ArcGIS was utilized to generate a hillshade map, aiding in identifying the active fault trace [30]. For the measurement of fault scarps, the method of Zheng et al. [31] was applied to determine the height and error of the fault scarps. Finally, combined with the focal mechanism (https://www.globalcmt.org/, accessed on 16 April 2023) and the 2009–2019 earthquake relocation catalog of the north–south seismic belt in China (https://www.ief.ac.cn/1068/info/2020/21375.html, accessed on 23 November 2023), an analysis of the seismogenic structure was conducted.

4. Results

4.1. Geometric Structure and Kinematic Characteristics of the MYBF

Based on the fault strike and kinematic properties, the MYBF can be divided into five subsegments: the Xiaomaoya segment (M-F1), the northern margin of the MYB segment (M-F2), the southern margin of the MYB segment (M-F3), the northeastern margin of the MYB segment (M-F4), and the Duoli segment (M-F5) (Figure 2a). The characteristics of each subsegment are described as follows.

4.1.1. M-F1

The M-F1 is located at the northwest end of the MYBF, controlling the northern boundary of the Xiaomaoya basin and extending from the southern foot of Haizi Mountain to the MYB basin, with an overall strike of about 128° (Figure 2a). North of Muye, the fault cuts through the outwash fan (Figure 4a,b), forming a fault scarp with a height of about 11 m (Figure 4c), resulting in a left-lateral offset of approximately 38 m in the Mulong River (Figure 4b). This indicates that the M-F1 is primarily a left-lateral strike–slip fault with a normal fault component.

4.1.2. M-F2

The M-F2 forms a right-stepping en echelon pattern with the M-F1 (Figure 2a). In contrast to the M-F1, M-F2 trends nearly east–west, with an overall strike of approximately 89°. The M-F2 controls the northern boundary of the MYB basin, extending from Heni to Jinqing, with a total length of approximately 9 km (Figure 2a). A fault scarp has developed at the Dongyu River terrace, a tributary of the Litang River in Jinqing. Trenches reveal fault occurrences of 185°/65° and 164°/66° [15], respectively. High-resolution DEM shows that the Dongyu River has developed three river terraces with no apparent horizontal offset (Figure 4d), indicating that the M-F2 is a normal fault. The terrain profile of the upper and lower walls of the fault is well fitted, and the height of the fault scarp at the T1 and T2 terraces is 2.7 and 6.9 m, respectively (Figure 4e).

4.1.3. M-F3

The M-F3 exhibits an overall trend nearly consistent with that of the M-F2 and controls the southern boundary of the MYB basin. Fault scarps are only developed in some sections, with an overall strike of about 88° (Figure 2a). A trench shows that the latest surface rupture earthquake in the M-F3 occurred after 1428 ± 43 AD [6], indicating that the M-F3 is a Holocene active fault. The strip topographic profile exhibits that the average altitude and topographic relief in the north of the MYB basin are higher than in the south (Figure 2b). This also implies that the activity of the M-F3 is weaker than that of the M-F2 in the late Quaternary.

4.1.4. M-F4

There is a striking change of approximately 27° between the M-F4 and M-F2, extending from the east of Jinqing to the vicinity of Duoli, with a total length of approximately 21 km (Figure 2a). The geometric shape of the M-F4 is tortuous, with significant variations in strike (ranging from 80° to 160°), and small pull-apart stepovers are developed (Figure 2a). The fault cuts through a series of outwash fans, forming high fault scarps and fault triangles (Figure 3a,b). The northernmost end of the M-F4 is located east of Jinqing and is characterized by a horsetail structure (Figure 5a,b) spreading towards the MYB basin in the east–west direction and connecting with the M-F2. South of Luanshibao, the M-F4 has cut through the outwash fan, resulting in a left-lateral offset of the moraine ridge by approximately 9 m (Figure 5c,d). North of Huguoduo, a pull-apart stepover with a width of approximately 1 km has developed. Multiple fault scarps are present within the stepover, and the gully does not exhibit significant horizontal offset after crossing the fault scarps (Figure 5e,f). Southeast of the Huguoduo stepover, the gully formed on the outwash fan exhibits an apparent left-lateral offset (Figure 5f). The topographic profile of the fault scarp indicates that the scarp height is approximately 14.3 m (Figure 5g). These faulted landforms demonstrate that M-F4 is an oblique–slip fault, exhibiting both left-lateral strike–slip and normal fault motion components.

4.1.5. M-F5

The M-F5 is located in the southeast of the MYB basin and is separated from the M-F4 by the Duoli restraining bend (Figure 2a). Based on remote sensing interpretation and field surveys, branch faults have developed in the M-F5 (Figure 6a,b). The main fault extends along the Litang River valley. Near Tieqiao, the left-lateral strike–slip movement of the fault offsets the ridge, forming water-retaining bulges and sag ponds (Figure 6c). Branch faults are distributed along the hillside on the right bank of the Litang River. Linear landforms with well-defined extensions are visible in remote sensing images (Figure 6a,b), and one branch fault appears as an upward-facing fault scarp (Figure 6d). The earthquake surface rupture zone has developed on the hillside north of Tieqiao. High-resolution DEM indicates that the elliptical extrusion bulges are arranged in a right echelon pattern, exhibiting characteristics of shear rupture (Figure 6e,f). The edge of the collapse pit is offset by approximately 3.1 m (Figure 6f). The earthquake surface rupture zone indicates that the Duoli restraining bend formed by the main fault has been breached. South of Tieqiao, the fault has cut through the alluvial–proluvial fan covering the T1 terrace, forming an upward-facing fault scarp and a sag pond, causing left-lateral offsets of the fan edge and gully by 26 and 9 m, respectively (Figure 6g,h). These faulted landform features indicate that the left-lateral strike–slip characteristics of the M-F5 are significant.

4.2. Offset Cluster Characteristics of the MYBF

Based on the high-resolution DEM of the M-F2 and M-F4, combined with the fault scarp height measurement method [31], the offset values of 91 fault scarps were obtained (Figure 7a). The results indicate that the offset values range between 0.57 and 24.77 m with the maximum value observed at the Huguoduo stepover (Figure 7b). This suggests that since the late Quaternary, the strain partitioning in the pull-apart stepover has been regulated through coordinated slip along a series of secondary normal faults. A total of 64 offset values falls within the range of 0.57–9.66 m, accounting for 70% of the total (Figure 7b). The heights of these 64 fault scarps were converted into a normal distribution function, with the offset value as the mean and the error value as the standard deviation. The sum of these normal distribution functions was calculated to obtain the cumulative offset probability density (COPD). The results show that the peak values of COPD are 0.66, 1.35, 2.70, 3.48, 3.81, 4.54, 5.86, 6.91, 7.69, and 9.16 m. Except for 0.66, 1.35, and 2.70 m, the offset values corresponding to the other peaks are relatively low (Figure 7c).

4.3. Geometric Distribution and Kinematic Property of the HGLF

In addition to the NW-trending LTFZ, a series of nearly EW-striking tensile faults have also developed in the MYB area [4]. The northern foot of Genie Mountain, located southwest of the MYB basin, is seismically active. The epicenters of the 1989 Batang strong earthquake swarm were arranged in a nearly east–west linear pattern (Figure 8a). In 2016, Ms4.9 and Ms5.1 earthquakes occurred successively in this area. Yi et al. [32] indicated that the seismogenic fault responsible for these earthquakes was the HGLF, which has a nearly east–west strike, based on focal mechanism analysis. The focal mechanisms of the Batang strong earthquake swarm are similar to those of the 2016 earthquakes (Figure 8a), indicating that the seismogenic fault of the Batang strong earthquake swarm can also be the HGLF. Remote sensing interpretation reveals the development of a near east–west linear landform at the northern foot of Genie Mountain (Figure 8b,c), with clearly defined faulted micro-landforms (Figure 8d,e), which can represent the late Quaternary active trace of the HGLF. Earthquake relocation results indicate that small earthquakes of 1.0 ≤ M < 3.0 are predominantly concentrated near these linear landforms, while earthquakes in the southern region are sparse (Figure 8a,f), confirming that these linear landforms correspond to fault traces. Accordingly, the HGLF is likely an active fault that reaches the surface, dips northward, and exhibits a kinematic property of normal faulting. The geometric and kinematic characteristics of the HGLF exhibit similarities to those of the M-F2 and M-F3 segments of the MYBF.

4.4. Geometric Distribution and Kinematic Properties of the ZMHF

The main body of Haizi Mountain consists of the Rongyicuo monzogranite body. Remote sensing images indicate that fault triangles at the southern foot of Haizi Mountain are well developed, with a clearly defined basin–mountain boundary (Figure 9a). A nearly east–west fault scarp, approximately 16.4 m in height, is present on the moraine platform near Yae (Figure 9c), with well-developed fault triangles extending along its direction (Figure 9a). The gully exhibits an overfall at the fault scarp, with a height of approximately 9.9 m, but no significant horizontal offset (Figure 9a,c). The linear landform east of Zimeihu Lake is prominent, with a fault scarp height of approximately 5 m, and the moraine ridge along this feature does not exhibit a noticeable horizontal offset (Figure 9e–g). These faulted landforms indicate that the ZMHF is primarily characterized by vertical movement. The fault cuts through moraine deposits dated to 15–22 ky [25], confirming its classification as an active fault. Small earthquakes are infrequent in the middle of the ZMHF but occur more frequently at both ends (Figure 9a). The profile shows that small earthquakes are primarily concentrated south of the fault trace (Figure 9b), indicating that the vertical movement of the ZMHF is typical of normal faulting. The ZMHF is a normal fault that dips southward, with an active age likely dating back to the late Pleistocene. The geometric and kinematic characteristics of the ZMHF also resemble those of the M-F2 and M-F3 segments of the MYBF, suggesting that they may share similar genetic mechanisms.

5. Discussion

5.1. Paleoearthquakes Recorded by the Fault Scarps of the MYBF

The peak value of COPD is typically utilized to identify the offset magnitude of a single earthquake event and the cumulative offset of multiple earthquake events, facilitating the exploration of paleoearthquake events and fault slip behaviors [33,34,35,36]. Among these, the peak value of the minimum offset represents the offset of the most recent event, whereas the other peaks indicate the cumulative offset of previous earthquake events. The COPD of vertical offset values of the MYBF exhibited significant peaks at 0.66 m, 1.35 m, and 2.70 m. The values 0 m, 0.66 m, and 1.35 m constitute an arithmetic sequence with an average difference of approximately 0.68 m, while 2.70 m is nearly four times the integer value of 0.68 m. Therefore, 0.68 m could represent the vertical co-seismic offset of the MYBF. The fault scarp heights of T1 and T2 terraces in the northern part of Jinqing are approximately 2.7 and 6.9 m, respectively (Figure 4e), and the recorded number of surface rupture earthquake events is 4 and 10, respectively.
Litang River flows from the MYB basin to the Litang basin through Duoli Valley, with the distance between the centers of these two basins being approximately 40 km (Figure 1c). It was determined that the Litang River primarily forms four levels of river terraces within the Litang basin by integrating Copernicus DEM, topographic profiles, the 1:200000 geological map of Litang, and previous studies [37,38]. The heights above the river level of the T1–T3 terraces are approximately 3–4 m, 6–8 m, and around 11 m, respectively (Figure 10a,b), which correspond to the heights above the river level of the terraces in the MYB basin (Figure 2c,d). The abandoned ages of river terraces in the MYB and Litang basins are comparable. The height above the river level of the T4 terrace in the Litang basin is approximately 28 m (Figure 10b), and the terrace profile reveals fluvial and lacustrine sediments. Wei et al. [37] suggested the existence of a large, outflow-type palaeolake in the Litang basin, with the T4 terrace potentially representing an erosion residual platform of fluvial and lacustrine sediments.
Previous studies excavated many trenches and conducted corresponding dating analyses in the Litang basin, providing reference data for determining the abandoned age of the geomorphic surface in the region. The field survey identified that the Bingzhan trench (29.97913°N, 100.21120°E; [39]) and Gaocheng trench 2 (29.96438°N, 100.22642°E; [40]) are located on terraces T1 and T2 of Litang River, respectively (Figure 10b). The Bingzhan trench reveals that U1–U3 layers are fluvial deposits, the U4 layer is a clay layer formed after terrace abandonment, the U5 layer is an earthquake-filling wedge, the U6–U7 layers consist of topsoil, and the AMS 14C result for the U2-1 layer is 4620 ± 40 y BP (Figure 10c; [39]). Xu et al. [3] determined the thermoluminescence (TL) age of a fine sand sample taken from 45 cm below the surface of the T1 terrace scarp in the northeastern part of Qudeng (Cunge) to be 6.63 ± 0.54 ky. These findings indicate that the abandoned age of the T1 terrace is after 4620 ± 40 y BP and is approximately around this age. For Gaocheng trench 2, a location distant from the fault within the trench, where the formation developed gently, was selected to define the terrace abandonment age. The U0–U1 layers predominantly consist of sand layers with well-developed bedding, the U2b layer is a palaeosol layer, and the U3a layer is a gravel layer with large particle size and moderate roundness, possibly indicative of proluvial facies sedimentation. The U3b–U4 layers form a palaeosol layer close to the surface (Figure 10d). The U0–U1 layers in this trench represent fluvial facies. The U2b palaeosol layer overlaying them can be utilized to determine the abandoned age of the T2 terrace, which is 9550 ± 30 y BP (Figure 10d; [40]). Xu et al. [3] obtained a TL age of 10.62 ± 0.81 ky for a greenish-grey sandy clay layer at the T1/T2 terrace of Jinchanggou River (a tributary of Litang River) at a depth of 0.4 m below the ground surface. This further supports the conclusion that the abandoned age of terrace T2 of Litang River is approximately 9550 y BP.
The height of the fault scarp of the Huguoduo north outwash fan is approximately 14.34 m (Figure 5g), with about 21 surface rupture earthquake events recorded. The results of exposure age indicate that the abandonment age of the outwash fan is approximately 21.7 ± 4.2 ky (Figure 5h; [5]). Therefore, since 4620 y BP, 9550 y BP, and 21.7 ky, the average recurrence period of the MYBF is 0.87 ky, 1.05 ky, and 0.97 ky, respectively. Based on the number of surface rupture earthquakes recorded by fault scarps and the abandonment age of geomorphic surfaces, the average recurrence period of the MYBF earthquakes is approximately 0.9–1.1 ky, which aligns with the recurrence period obtained by predecessors through trench studies [6].

5.2. Characteristics and Formation Mechanism of Structure Deformation in MYB Area

As mentioned above, the M-F2 is dominated by normal faults, M-F4 is characterized by both left-lateral strike–slip and normal fault motion components, and M-F5 is dominated by left-lateral strike–slip motion. From the M-F5 to M-F2, the strike of the fault gradually shifts from NW to EW, the left-lateral strike–slip component decreases, and the normal fault component increases. This pattern is consistent with the characteristics of a horsetail structure at the tail end of a strike–slip fault [41]. Therefore, the MYBF and ZQMF constitute the extensional horsetail structure at the northwest end of the LTFZ (Figure 1c).
Changes in the local tectonic stress field can raise the formation of the horsetail structure. The LTFZ and BTFZ have exhibited a commensurate strike–slip rate since the late Quaternary, forming a V-shaped conjugate strike–slip fault system (Figure 1c). This system provides the MYB area with a tectonic stress field characterized by nearly east–west compression and nearly north–south tension [4,23]. GPS data and focal mechanisms also reflect these characteristics of the tectonic stress field [2,4,42]. Therefore, it is believed that the formation of the V-shaped conjugate strike–slip fault system can directly cause the development of the horsetail structure.
The location of the change in strike and kinematic properties of the MYBF roughly coincides with the Granite/Triassic boundary. For example, at the lithological transition, the strike of M-F4 and M-F2 shifts to near east–west, and their kinematic properties change to a normal faulting regime (Figure 11a). Previous studies have shown that lithology plays a crucial role in fault styles due to the varying mechanical properties of rocks [43,44]. Similarly, rock mechanics can also influence the geometric distribution of faults. For instance, Li [45] found that the bedrock affects the geometry of the FDM-HYZ fault on the northeastern margin of the Tibet Plateau. As the northwest extension of the LTFZ cuts through the granite rock body, it enters an area dominated by the Triassic (Lanashan Formation: limestone, shale, lithic sandstone) (Figure 11). Compared to granite, limestone, shale, and lithic sandstone generally have a higher Poisson’s ratio and lower compressive and tensile strength [46]. This indicates that under nearly north–south tensile stress, tensile fractures are more likely to develop in the Triassic (Figure 12b). In addition, lithological changes can lead to stress redistribution during the propagation of the MYBF, resulting in the conversion of shear stress into nearly north–south tensile stress. This process further facilitates the expansion of tensile fractures in the MYBF direction (Figure 12b). These tensile fractures contribute to stress release, and as they continue to propagate, they gradually form the current horsetail structure characteristics (Figure 12). Accordingly, the V-shaped structural system and lithological variations in Litang–Batang have jointly influenced changes in the local tectonic stress field, leading to the development of the horsetail structure at the northwest end of the LTFZ. The MYB basin is an extensional fault basin formed by the conversion of the left-lateral strike–slip component of the LTFZ into a nearly north–south tensile component, along with the superposition of nearly north–south tensile stress (Figure 12c). The BTFZ did not form a large Quaternary basin [4], which can be attributed to the relatively uniform rock mechanical properties near the BTFZ.
Similarly, the development of the HGLF and ZMHF is also a response to the regional tectonic stress field. Comparing the geometric distribution of the fault and the 1:250,000 geological map indicates that ZMHF and HGLF are both distributed near the contact part of the rock body (Figure 2a). The contact part of the rock body is always a weak zone with poor mechanical properties, which constitutes a basement pre-existing structure. Analog modeling reveals that basement pre-existing structures play a significant role in controlling the formation and evolution of faults [47]. Therefore, after the formation of the Litang–Batang V-shaped structural system, under the influence of tensile stress, the regional crust in the MYB area extended in a nearly north–south direction, leading to the development of tensile fractures in rocks with weak mechanical properties. This process gradually resulted in the formation of a series of near east–west faults, such as the HGLF and ZMHF (Figure 12). Under the traction of plastic deformation of low-viscosity materials in the middle and lower crust [48,49], a series of near east–west normal faults developed in the rigid upper crust. Together with the LTFZ and BTFZ, these faults have adjusted the southeast movement of regional crustal materials.

5.3. Seismic Potential in the MYB Area

Based on the Average Displacement–Moment Magnitude empirical formula for normal faults [50], and considering the estimation of a vertical co-seismic offset of 0.68 m, the MYBF could generate an Mw 6.7 ± 0.3 surface rupture earthquake without accounting for cascade rupturing. It is worth mentioning that because the MYBF segments M-F4 and M-F5 possess a certain left-lateral strike–slip component, the moment magnitude obtained in this study using empirical formula may result in an underestimation. The Tieqiao trench revealed that the most recent surface rupture earthquake on the MYBF occurred after 1576 AD and can correspond to the Litang earthquake in 1729 AD recorded in the historical earthquake catalog [7]. The elapsed time since the surface rupture earthquake of the MYBF is approximately 295 years, which is shorter than the average recurrence period of 0.9–1.1 ky. Therefore, the likelihood of a surface rupture earthquake occurring in the near future on the MYBF is low. However, the frequent moderate–strong earthquakes in the MYB area in recent years indicate that the near east–west extensional fault is the primary seismogenic structure. GPS results further reveal that the current crustal stress state in the Litang–Batang area is dominated by near north–south tension [2,42]. In recent decades, the HGLF has experienced frequent moderate–strong earthquakes, and such seismic activity can contribute to further extension of the fault. The profile indicates that there are mainly two earthquake clusters at depths of 0–5 km and 10–15 km in the MYB basin (Figure 8g). The upper cluster of seismogenic faults can correspond to the nearly east–west segment of the MYBF, while the lower cluster of seismogenic faults can correspond to the HGLF (Figure 8g). This indicates that the HGLF can extend into the lower part of the MYB basin. Under the influence of nearly north–south tensile stress, the MYB basin can be at risk of moderate–strong earthquakes. The unstable slopes in the northeast margin of the basin are well developed and are in proximity to major traffic arteries [9,10]. Attention should be given to mitigating the risk of landslides, collapses, and other disasters induced by earthquakes.

6. Conclusions

This study systematically employs remote sensing interpretation, field surveys, UAV photogrammetry, and LiDAR scanning to constrain the structural deformation style and seismic potential of the MYBF. This study presents the most detailed geometric distribution of the MYBF at present. Using high-resolution remote sensing imagery and small earthquake clusters, the geometric and kinematic characteristics of the ZMHF and HGLF are constrained for the first time. The main conclusions are as follows: (1) the average recurrence period of strong earthquakes on the MYBF since the late Quaternary is 0.9–1.1 ky. (2) The MYBF could produce earthquakes of approximately Mw 6.7 ± 0.3, and the possibility of surface rupture earthquakes occurring in the near future is low. However, the expansion of the HGLF can lead to moderate, strong earthquakes in the MYB area. (3) The variation in the local tectonic stress field, caused by the Litang–Batang V-shaped structure system and lithological differences, results in the formation of the extensional horsetail structure in the northwest segment of the Litang fault zone. The MYB basin is a tensional fault basin at the fault’s termination. (4) The HGLF and ZMHF are active faults. They collectively regulate the movement of regional crustal material under the influence of nearly north–south tensile stress, along with the Litang–Batang V-shaped structure system. This study provides a new perspective for understanding the tectonic deformation mechanism of the MYBF and provides scientific support for seismic hazard mitigation and disaster reduction in the MYB area and the safe construction of major national projects.
Although the high-resolution DEM of the MYBF was obtained in this study, the structural deformation characteristics of the MYB area were qualitatively described only in terms of the geometric structure and kinematic properties of the fault. This study did not obtain the abandoned age of the geomorphic surface and did not analyze the late Quaternary slip rate of the MYBF. Quantitative slip rate may better constrain the crustal deformation model in the MYB area. In addition, there are few studies on the influence of lithology on fault mode or seismic fracture behavior. In the future, the effect of lithological changes on stress distribution may be further discussed in combination with numerical simulation or analog modeling.

Author Contributions

X.Z.: writing—original draft, software, methodology, investigation, visualization, formal analysis, and data curation; N.Z.: writing—review and editing, validation, supervision, project administration, methodology, investigation, funding acquisition, formal analysis, and conceptualization; X.Y.: investigation and writing—review and editing; G.Y.: resources and supervision; and H.L.: methodology and supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the National Natural Science Foundation of China (42177184) and the China Geological Survey (DD20221816).

Data Availability Statement

The earthquake source mechanism solution was derived from https://www.globalcmt.org/ (accessed on 16 April 2023); and the relocate earthquake catalog was sourced from https://www.ief.ac.cn/1068/info/2020/21375.html (accessed on 23 November 2023).

Acknowledgments

Acknowledgments to the China Earthquake Networks Center, National Earthquake Science Data Center, and Institute of Earthquake Forecasting, China Earthquake Administration for providing the earthquake catalog. The acquisition and processing of UAV LiDAR data were assisted by the team led by Xiujun Dong from Chengdu University of Technology; Xiwei Xu from China University of Geosciences (Beijing) provided suggestions for revisions of the manuscript. We would like to express our gratitude together. We thank the reviewers and editors for their help in improving this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Active faults map of Tibet Plateau (modified from [3]); (b) structural diagram of the northwest Sichuan sub-block (modified from [14]); (c) seismotectonic map of the Litang–Batang area. The green earthquake points are from Historical Earthquake Catalog of China (http://data.earthquake.cn, accessed on 19 September 2023), time range: –1969. The pink earthquake points are from the earthquake catalog of China Network (http://data.earthquake.cn, accessed on 10 January 2023), time range: 1970–2008. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China (https://www.ief.ac.cn/1068/info/2020/21375.html, accessed on 23 November 2023), time range: 2009–2019. Abbreviations: NSSB = northwest Sichuan sub-block; CYSB = Central Yunnan sub-block; GYFZ = Ganzi–Yushu fault zone; XSHFZ = Xianshuihe fault zone; ZMFZ = Zemuhe fault zone; LMFZ = Longmenshan fault zone; BTFZ = Batang fault zone; DDFZ = Deqin–Zhongdian–Daju fault zone; LXFZ = Lijiang–Xiaojinhe fault zone; JSJF = Jinshajiang fault zone; YNXF = Yunongxi fault; LTFZ = Litang fault zone; CPHF = Cuopuhu fault; MYBF = Maoyaba fault; ZQMF = Zheqingma fault; LMGF = Lamagou fault; GCF = Gaocheng fault; KDF = Kangga–Dewu fault; ZMHF = Zimeihu fault; HGLF = Hagala fault.
Figure 1. (a) Active faults map of Tibet Plateau (modified from [3]); (b) structural diagram of the northwest Sichuan sub-block (modified from [14]); (c) seismotectonic map of the Litang–Batang area. The green earthquake points are from Historical Earthquake Catalog of China (http://data.earthquake.cn, accessed on 19 September 2023), time range: –1969. The pink earthquake points are from the earthquake catalog of China Network (http://data.earthquake.cn, accessed on 10 January 2023), time range: 1970–2008. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China (https://www.ief.ac.cn/1068/info/2020/21375.html, accessed on 23 November 2023), time range: 2009–2019. Abbreviations: NSSB = northwest Sichuan sub-block; CYSB = Central Yunnan sub-block; GYFZ = Ganzi–Yushu fault zone; XSHFZ = Xianshuihe fault zone; ZMFZ = Zemuhe fault zone; LMFZ = Longmenshan fault zone; BTFZ = Batang fault zone; DDFZ = Deqin–Zhongdian–Daju fault zone; LXFZ = Lijiang–Xiaojinhe fault zone; JSJF = Jinshajiang fault zone; YNXF = Yunongxi fault; LTFZ = Litang fault zone; CPHF = Cuopuhu fault; MYBF = Maoyaba fault; ZQMF = Zheqingma fault; LMGF = Lamagou fault; GCF = Gaocheng fault; KDF = Kangga–Dewu fault; ZMHF = Zimeihu fault; HGLF = Hagala fault.
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Figure 2. (a) Geometric distribution map of active faults and regional geological map in the MYB area; (b) strip topographic profile of the MYB basin; (c,d) topographic profile of river terraces in the MYB basin. The geological map was modified from the 1:250,000 Xinlong geological map. The topographic profile data are sourced from Copernicus DEM.
Figure 2. (a) Geometric distribution map of active faults and regional geological map in the MYB area; (b) strip topographic profile of the MYB basin; (c,d) topographic profile of river terraces in the MYB basin. The geological map was modified from the 1:250,000 Xinlong geological map. The topographic profile data are sourced from Copernicus DEM.
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Figure 3. (a) High-resolution DEM hillshade on the northeast margin of the MYB Basin; (b) division of geomorphic units in the northeastern margin of the MYB Basin.
Figure 3. (a) High-resolution DEM hillshade on the northeast margin of the MYB Basin; (b) division of geomorphic units in the northeastern margin of the MYB Basin.
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Figure 4. (a) DEM of north of Muye; (b) faulted landform map of north of Muye; (c) measurement of fault scarp height of north of Muye; (d) DEM and faulted landform map of north of Jinqing; (e) measurement of fault scarp height of Jinqing north.
Figure 4. (a) DEM of north of Muye; (b) faulted landform map of north of Muye; (c) measurement of fault scarp height of north of Muye; (d) DEM and faulted landform map of north of Jinqing; (e) measurement of fault scarp height of Jinqing north.
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Figure 5. (a,b) DEM and faulted landform map of Jinqing east; (c,d) DEM and faulted landform map of Luanshibao south; (e,f) DEM and faulted landform map of Huguoduo north; (g) measurement of fault scarp of Huguoduo north; (h) exposure age of Huguoduo north outwash fan (Source: [5], the asterisk (*) indicates outliers and should be removed).
Figure 5. (a,b) DEM and faulted landform map of Jinqing east; (c,d) DEM and faulted landform map of Luanshibao south; (e,f) DEM and faulted landform map of Huguoduo north; (g) measurement of fault scarp of Huguoduo north; (h) exposure age of Huguoduo north outwash fan (Source: [5], the asterisk (*) indicates outliers and should be removed).
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Figure 6. (a,b) Remote sensing image and geometric distribution of M-F5; (c,d) photos of typical faulted landforms of the M-F5; (e,f) characteristics of DEM hillshade and shear rupture in the surface rupture zone of the M-F5; (g,h) DEM and faulted landform map of Tieqiao south.
Figure 6. (a,b) Remote sensing image and geometric distribution of M-F5; (c,d) photos of typical faulted landforms of the M-F5; (e,f) characteristics of DEM hillshade and shear rupture in the surface rupture zone of the M-F5; (g,h) DEM and faulted landform map of Tieqiao south.
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Figure 7. (a) Distribution of vertical offset measurement points of the MYBF; (b) distribution map of vertical offset measurement value of the MYBF; (c) vertical offset COPD of the MYBF.
Figure 7. (a) Distribution of vertical offset measurement points of the MYBF; (b) distribution map of vertical offset measurement value of the MYBF; (c) vertical offset COPD of the MYBF.
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Figure 8. (a) Geometric distribution of the HGLF and distribution of small earthquakes; (b,c) linear landform of the HGLF revealed by hillshade map; (d,e) linear microtopography revealed by optical remote sensing images; (f,g) spatial distribution characteristics of small earthquakes. The pink earthquake points are from the earthquake catalog of China Network, time range: 1970–2008. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China, time range: 2009–2019.
Figure 8. (a) Geometric distribution of the HGLF and distribution of small earthquakes; (b,c) linear landform of the HGLF revealed by hillshade map; (d,e) linear microtopography revealed by optical remote sensing images; (f,g) spatial distribution characteristics of small earthquakes. The pink earthquake points are from the earthquake catalog of China Network, time range: 1970–2008. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China, time range: 2009–2019.
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Figure 9. (a) Geometric distribution of the ZMHF and distribution of small earthquakes; (b) spatial distribution characteristics of small earthquakes around the ZMHF; (c,e) linear microtopography revealed by optical remote sensing images; (d,f,g) scarp height measurement of the ZMHF. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China, time range: 2009–2019.
Figure 9. (a) Geometric distribution of the ZMHF and distribution of small earthquakes; (b) spatial distribution characteristics of small earthquakes around the ZMHF; (c,e) linear microtopography revealed by optical remote sensing images; (d,f,g) scarp height measurement of the ZMHF. The red earthquake points are from the 2009–2019 earthquake relocation catalog of the North–South seismic belt in China, time range: 2009–2019.
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Figure 10. (a) Copernicus DEM hillshade of the Litang basin (the yellow lines in the figure indicate the geomorphological interpretation boundaries); (b) geomorphic unit division based on hillshade (the basin boundary is delineated by the yellow line in (a); the topographic profile locations are marked in (a,b), with data sourced from the Copernicus DEM); (c) Bingzhan trench stratigraphic unit (modified from [39]); (d) Gaocheng trench 2 stratigraphic unit (modified from [40]).
Figure 10. (a) Copernicus DEM hillshade of the Litang basin (the yellow lines in the figure indicate the geomorphological interpretation boundaries); (b) geomorphic unit division based on hillshade (the basin boundary is delineated by the yellow line in (a); the topographic profile locations are marked in (a,b), with data sourced from the Copernicus DEM); (c) Bingzhan trench stratigraphic unit (modified from [39]); (d) Gaocheng trench 2 stratigraphic unit (modified from [40]).
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Figure 11. (a) Geometric distribution and lithological distribution of the MYBF; (b–d) photos of bedrock fault and lithology of the MYBF. The geological map was modified from the 1:250,000 Xinlong geological map.
Figure 11. (a) Geometric distribution and lithological distribution of the MYBF; (b–d) photos of bedrock fault and lithology of the MYBF. The geological map was modified from the 1:250,000 Xinlong geological map.
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Figure 12. Simplified model of structural deformation characteristics and formation mechanism in the MYB area. (a) structural style of the MYB area prior to the formation of the V-shaped structural system; (b) structural style of the MYB area during the early-stage formation of the V-shaped structural system; (c) current structural style of the MYB area: development of horsetail structures and East-West trending faults.
Figure 12. Simplified model of structural deformation characteristics and formation mechanism in the MYB area. (a) structural style of the MYB area prior to the formation of the V-shaped structural system; (b) structural style of the MYB area during the early-stage formation of the V-shaped structural system; (c) current structural style of the MYB area: development of horsetail structures and East-West trending faults.
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Table 1. High-resolution DEM parameters obtained from the UAV of the MYBF.
Table 1. High-resolution DEM parameters obtained from the UAV of the MYBF.
No.LocationArea (km2)Point CloudsResolution (m)DateMethod
1NE margin of MYB basin35.001246890380.2018 June 2021UAV + LiDAR
2North of Muye0.20348268130.082 September 2021UAV + SfM
3North of Jinqing0.4771972410.2430 May 2023UAV + SfM
4East of Jinqing0.48106264960.2225 June 2021UAV + SfM
5South of Duoli0.55169465150.1823 June 2021UAV + SfM
6South of Tieqiao0.2260442700.2423 June 2021UAV + SfM
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Zhang, X.; Zhong, N.; Yu, X.; Yang, G.; Li, H. Structural Deformation Style and Seismic Potential of the Maoyaba Fault, Southeastern Margin of the Tibet Plateau. Remote Sens. 2025, 17, 1288. https://doi.org/10.3390/rs17071288

AMA Style

Zhang X, Zhong N, Yu X, Yang G, Li H. Structural Deformation Style and Seismic Potential of the Maoyaba Fault, Southeastern Margin of the Tibet Plateau. Remote Sensing. 2025; 17(7):1288. https://doi.org/10.3390/rs17071288

Chicago/Turabian Style

Zhang, Xianbing, Ning Zhong, Xiao Yu, Guifang Yang, and Haibing Li. 2025. "Structural Deformation Style and Seismic Potential of the Maoyaba Fault, Southeastern Margin of the Tibet Plateau" Remote Sensing 17, no. 7: 1288. https://doi.org/10.3390/rs17071288

APA Style

Zhang, X., Zhong, N., Yu, X., Yang, G., & Li, H. (2025). Structural Deformation Style and Seismic Potential of the Maoyaba Fault, Southeastern Margin of the Tibet Plateau. Remote Sensing, 17(7), 1288. https://doi.org/10.3390/rs17071288

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