Present-day Crustal Deformation Research Articles

Present-day crustal deformation based on an interpolated GPS velocity field in the collision zone of the Arabia-Eurasia tectonic plates

Present-day crustal deformation based on an interpolated GPS velocity field in the collision zone of the Arabia-Eurasia tectonic plates

Correlation between Strain Rate and Seismicity in Different Tectonic Settings

Abstract Geodetic strain rate characterizes present-day crustal deformation and therefore may be used as a spatial predictor for earthquakes. However, the reported correlation between strain rates and seismicity varies significantly in different places. Here, we systematically study the correlation between strain rate, seismicity, and seismic moment in six regions representing typical plate boundary zones, diffuse plate boundary regions, and continental interiors. We quantify the strain rate–seismicity correlation using a method similar to the Molchan error diagram and area skill scores. We find that the correlation between strain rate and seismicity varies with different tectonic settings that can be characterized by the mean strain rates. Strong correlations are found in typical plate boundary zones where strain rates are high and concentrated at major fault zones, whereas poor or no correlations are found in stable continental interiors with low strain rates. The correlation between strain rate and seismicity is also time dependent: It is stronger in seismically active periods but weaker during periods of relative quiescence. These temporal variations can be useful for hazard assessment.

Present-day crustal deformation based on GPS measurements in southeastern Tibetan Plateau: implications for geodynamics and earthquake hazard

GPS-derived strain rates can provide a tight constraint in understanding tectonic evolution of the Tibetan Plateau and are helpful in seismic hazard assessment. For this purpose, we at first verify the method, proposed by Zhu et al. in 2005 and 2006, for the computation of the strain rates, and found that the approach is reasonable and accurate. Then, based on the updated GPS data, we compute strain rates in southeastern Tibetan Plateau (SETP). The computed results showed that the strain rates in the Sichuan Basin and South China Block are very small, and the high values are largely concentrated along the Sagaing Fault and Xianshuihe-Anninghe-Xiaojiang fault system. In addition, the highest principal strain rates are located around the eastern Himalayan syntaxis (EHS), with the compressive orientations perpendicular to the Main Thrust Belt. In particular, the calculated extensive deformation basically matches the normal faulting earthquakes. In general, the characteristic of the strain rate distribution is in good agreement with the tectonic structures from the geological and geophysical investigations. At last, according to the strain rates, seismicity, and tectonic structures, we estimate five most likely zones for future major earthquakes in SETP. These areas include the Zemuhe Fault, northwestern segment of the Red River Fault, and at the intersection between the Ganzi-Yushu Fault and the Xianshuihe Fault, and at the one between the Zhongdian Fault and Jinshajiang Fault. Consequently, this study is significant in deep understanding of the geodynamics in the Tibetan Plateau and earthquake hazard assessment.

Present-Day Crustal Deformation of the Northwestern Tibetan Plateau Based on InSAR Measurements

In this study, The ENVISAT advanced synthetic aperture radar observations from 2003 to 2010 of a descending track covering an area of 100 km × 300 km were used to map the surface velocity field in northwestern Tibet. The derived line-of-sight (LOS) velocity map revealed that interseismic deformation was mainly located on the Altyn Tagh Fault (ATF) and other four immature subsidiary faults (i.e., Tashikule Fault, Muzitage-jingyuhe Fault, Heishibeihu Fault, and Woniuhu Fault). A 2D elastic screw dislocation model was used to interpret the interferometric synthetic aperture radar (InSAR) velocity profiles, which revealed the following results. (a) The oblique movement is partitioned between left-lateral slip at a rate of 6.3 ± 1.4 mm/y on the ATF and 5.9 ± 2.8 mm/y on the subsidiary faults. The low slip rate of the ATF indicates that the ATF does not drive the northeastward extrusion of material, with most of the extrusion occurring in the eastern interior of the plateau and the four subsidiary faults localizing the oblique convergence partitioned in the west. This can reasonably explain why catastrophic earthquakes and rapid slip do not occur all over along the ATF. (b) Based on the four subsidiary faults accommodating the oblique movement and the traces amalgamation with the EKLF (delineated Bayan Har plate boundary to the northeast), we concluded guardedly that the four subsidiary faults are the evoluting plate boundary of the Bayan Har block to the northwest. (c) The Tanan top-up structure had an uplift rate of ~0.6 mm/y at the south of the Tarim Basin.

Present-day Crustal Deformation in West Sumatra After Series of Sumatran Great Earthquake from 2004-2010

Present-day crustal deformation was an attempt to estimate earthquake potential, yet the presence of postseismic deformation should be carefully identified. Studying crustal deformation in West Sumatra has been important for this purpose since the series of Sumatran Great Earthquake from 2004-2010. This study utilized present-day GNSS data (2017-2021) and pre-2004 GNSS velocities to understand the present-day crustal deformation. Bernese 5.2 was used to process the GNSS data and linear regression was used to calculate present-day velocities. These velocities were transformed into an ITRF2000-based Sundaland plate reference frame and then the velocities were compared to pre-2004 velocities in the same reference frame. The present-day velocities were ranging from 28.4 mm/yr to 58.3 mm/yr in ITRF2014 and from 8.8 to 44.8 mm/yr in the Sundaland plate reference frame. This suggests West Sumatra was located on the Sumatra block of the Sundaland plate. The low velocity difference ( 11.7 mm/yr) with the random vector direction between present-day velocities and pre-2004 velocities shows that there is no postseismic deformation affecting West Sumatra. This proposes the utilization of present-day velocities for earthquake potential estimation in West Sumatra.

The mechanism of the present-day crustal deformation in southeast Tibet: from numerical modelling and geodetic observations

SUMMARY The mechanism of present-day crustal deformation in southeast Tibet remains controversial. 3-D high-precision geodetic data can provide significant clues to analyse the key driving forces. Here, we conduct a series of 3-D finite-element modelling to investigate the influences of gravitational collapse, tectonic extrusion and mid-to-lower crustal flow on crustal deformation in southeast Tibet. The numerical results show that the gravitational collapse leads to predominant N-S extension and surface subsidence in the northern region, and predominant NW-SE compression and uplift in the southern region, which can explain the normal-faulting earthquakes in the interior. The gravity-driven horizontal velocity depends on the upper crustal viscosity, while the vertical velocity is determined by mid-to-lower crustal viscosity. The eastward tectonic extrusion causes slight southeastward rotation and predominant E-W compression in the northern region but has a little effect on the deformation in the southern region. By considering the joint effects of gravitational collapse and tectonic extrusion, we simulate the crustal deformation that reconciles with present-day geodetic observations. Both the two driving forces lead to positive shear strain rates along the major fault zones, with more contributions from the tectonic extrusion of the Tibetan Plateau. Constrained by the 3-D geodetic observations, the numerical results argue against the presence of massive fast mid-to-lower crustal flow from the Tibetan Plateau. Overall, the present-day crustal deformation in southeast Tibet is jointly driven by gravitational collapse and tectonic extrusion, which play distinct roles in shaping the faulting kinematics and regional strain partitioning.

Fault locking of the Qilian–Haiyuan fault zone before the 2022 Menyuan Ms6.9 earthquake and its seismic hazards in the future

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 MS6.9 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 MS6.9 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.

Two-Decade GNSS Observation Processing and Analysis with the New IGS Repro3 Criteria: Implications for the Refinement of Velocity Field and Deformation Field in Continental China

Extensive observation collection, unified and rigorous data processing, and accurate construction of the station motion model are the three essential elements for the accuracy and reliability of the Global Navigation Satellite System (GNSS) velocity field. GNSS data reprocessing not only can weaken the influence of untrue nonlinear site signals caused by imperfect models but also can eliminate the displacement offset caused by frame transformation, solution strategy, and model change. Based on the new repro3 criteria of the International GNSS Service (IGS), we process rigorously GNSS observations of continental China from the period 2000 to 2020 to refine GNSS station secular velocities and analyze the present-day crustal deformation in continental China. The main contributions of this work included the followings. Firstly, the repro3 algorithm and model are used to uniformly and rigorously process the two-decade GNSS historical observations to obtain more reliable GNSS coordinate time series with mm-level precision. Combined with the historical records of major earthquakes in continental China, we build a GNSS time series model considering nonlinear factors (velocity, offset, period, co-seismic/post-seismic deformation) to extract GNSS horizontal velocity field whose root mean square (RMS) mean is 0.1 mm/a. Secondly, the GNSS horizontal grid velocity field in continental China is interpolated using the gpsgridder method (the minimum radius is set to 16, and the Poisson’s ratio is set to 0.5). Estimation and analysis of the crustal strain rate solution lead to the conclusion that the strain degree in West China (the high strain region is mainly located in the Qinghai Tibet Plateau and Tianshan Mountains) is much more intense than that in the east (the main strain rate is less than 5 nstrain/year). In addition, most strong earthquakes in the Chinese mainland occurred on active blocks and their boundary faults with large changes in the GNSS velocity field and strain field. Then, an improved K-means++ clustering analysis method is proposed to divide active blocks using GNSS horizontal velocity field. Furthermore, different relative motion models of different blocks are constructed using the block division results. Among them, the Eurasian block has the lowest accuracy (the RMS of residual velocity in the east and north directions are 5.60 and 9.65 mm/a, respectively), and the China block 7 has the highest accuracy (the RMS mean of relative velocity in the east and north directions are 2.60 and 2.65 mm/a, respectively). More observations (2260+ sites), longer time (20 years), and updated criteria (Repro3) are to finely obtain the GNSS velocity field in continental China, and depict crustal deformation and active block with the gpsgridder and improved K-means++ methods.

Present-day crustal deformation and slip rate along the southern Sagaing fault in Myanmar by GNSS observation

The Sagaing fault in Myanmar runs through the entire country and is responsible for major earthquakes, yet only its northern half has been studied geodetically to date. We analyzed Global Navigation Satellite System (GNSS) data to estimate crustal deformation along the central and southern parts of the Sagaing fault. We used a 2-dimensional dislocation model to estimate slip rate, locking depth and lateral offset between surface fault trace and downdip edge of the locked fault along the Sagaing (SGs), Meiktila (MTLs) and Bago (BGOs) segments of the fault. The estimated slip rate is 16–24 mm/yr with a locking depth of 10–16 km in our analysis for the central to southern segments, which is deeper than the locking depth of northern segment from previous studies. The slip rate is ~23–24 mm/yr in the central part of the Sagaing fault, while it is probably slower (~16 mm/yr) in the southern part of our study area. The predicted maximum shear strain from the optimal model is shifted from the surface fault trace. If the locked part of the fault connects directly from the deeper offset dislocation to the surface fault trace, it may be dipping with inferred values of 71°E for the SGs and 78°W for the MTLs, based on the distance between surface trace and the dislocation line at depth. The estimated potential magnitude of earthquakes for each segment as of 2021 are Mw ~7.3 in SGs, Mw ~7.4 in MTLs and Mw ~7.3 in BGOs, respectively.

Present-day crustal deformation in the northeastern Tibetan Plateau and its correlation with spatiotemporal seismicity characteristics

The Northeastern Tibetan Plateau (NTP) is a typical intraplate region with numerous faults and intense seismicity. This study aimed to enhance our understanding of the spatiotemporal evolution of the region’s seismicity. We first obtained the strain-rate characteristics by establishing a regional kinematic model using global navigation satellite system velocities from 1999 to 2007. Subsequently, we discussed the spatiotemporal evolution of seismicity by analyzing the correlation between the maximum shear-strain rate and earthquakes. Finally, we analyzed seismic hazards in the NTP, while determining regions with high earthquake risk. Our results indicated a complex diffuse deformation pattern owing to tectonic loading and strike- and thrust-fault activity. Higher maximum shear-strain rates primarily accumulated on large strike-slip faults. The NTP was categorized into two domains based on correlation analysis. In regions with the highest 59% maximum shear-strain rates, the correlation between the cumulative strain and seismicity-rate counts was higher than that in other regions. Seismicity in these regions evolved from localization to accumulation, while subsequently returning to the localization stage, and thus may have been influenced by earlier large earthquakes. Seismicity in the remaining 41% of the NTP, i.e., regions with relatively low strain rates, was categorized as being in the localization stage. Our findings revealed the spatiotemporal characteristics of seismicity in the NTP and may contribute to future seismic risk evaluations. Further research should conduct earthquake potential assessments, especially in low strain-state regions.

Present-Day Crustal Deformation in the Southeastern Tibet: Insights from Three-Dimensional Finite-Element Modeling

Present-Day Crustal Deformation in the Southeastern Tibet: Insights from Three-Dimensional Finite-Element Modeling

The migration of the crustal deformation peak area in the eastern Himalayan Syntaxis inferred from present-day crustal deformation and morpho-tectonic markers

The present-day Global Positioning System (GPS) velocity field shows that the Indian Plate is not a complete rigid block, as its northeastern corner has been torn off and clockwise rotating relative to the main part. With the updated GPS velocity data, the Euler vector of the northeastern corner of the Indian Plate relative to the stable main plate is deduced as (89.566 ± 0.06° E, 26.131 ± 0.05° N, 1.34 ± 0.11°/Myr). The peak area of the present-day crustal deformation is located in the Chayu deformation belt with the compressional dilation strain rate over 160 nanostrain/yr. However, the Namche-Barwa Syntaxis with the massive crustal thickening and intense surface erosion is generally considered to be the previous locus of the strongest compressional stress in the Eastern Himalayan Syntaxis over long geological timescales. Thus, there is a discrepancy between the previous and present-day crustal deformation peak areas. We argue the migration of the crustal deformation peak area with a total distance of about 120 km and ascribe it to the variation of stress conditions caused by northeast India's clockwise rotation.

Present-Day Crustal Deformation Within the Western Qinling Mountains and Its Kinematic Implications

The western Qinling Mountains, located between the East Kunlun fault and the West Qinling fault, hold the key to investigating the outward expansion of the Tibetan Plateau. We use up-to-date GPS observations to derive high spatial–temporal resolution crustal velocity and strain rate fields for this region. Our results suggest that a series of NEE-trending faults bounding the eastern margin of the western Qinling Mountains experience right-lateral strike slip with low rates of ~ 1 mm/yr. In addition, our results suggest that crustal deformation of the western Qinling Mountains could be governed by a right-lateral shear zone trending NNE at a rate of ~ 6 mm/yr, producing a clockwise rotation of subblocks: left-lateral and right-lateral strike slip on the NWW-trending and NEE-trending faults, respectively. The eastward extrusion of the Tibetan Plateau along the western Qinling Mountains is limited further east. In contrast, the NNE-ward expansion of the northeastern Tibetan Plateau is the primary motion which extends through the western Qinling Mountains and the Longxi block. The results of this study improve our understanding of the outward expansion of the Tibetan Plateau influenced by the Indian–Eurasian collision.

Present-day crustal deformation revealed active tectonics in Yogyakarta, Indonesia inferred from GPS observations

We investigated the active crustal structure in Yogyakarta, Indonesia, using new and denser Global Positioning System (GPS) data. Deformation rate estimated from five years (2013–2018) of observations on 22 campaign might record broad deformation after the 2006 Mw7.8 Java tsunami earthquake and postseismic transient due to the 2006 Mw6.3 Yogyakarta earthquake. We conducted a decomposition method to obtain a short wavelength feature by removing those postseismic deformations from the observation data. The short wavelength pattern revealed active tectonics indicating a combination of E–W dip-slip motion and N–S left-lateral structure. A large maximum shear strain rate (>0.1 microstrain/yr) was estimated along the Opak fault while a large dilatation rate (<-0.1 microstrain/yr) was estimated around the Bantul Graben. The analysis result indicates important implications for crustal dynamics and assessing future seismic hazards potential in the Yogyakarta region.

Active crustal deformation in southeastern Tibetan Plateau: The kinematics and dynamics

Crustal deformation in southeastern Tibetan Plateau has been attributed to tectonic extrusion and gravitational spreading. Here we analyzed the present-day strain partitioning in this region using GPS data. The results show highly localized shear strain along the Xianshuihe-Anninghe-Xiaojiang strike-slip faults, as expected by the model of tectonic extrusion. However, the localized shear strain along strike-slip faults ends in southern Yunnan and transfers to crustal extension in Yunnan and contraction in Myanmar. We developed three-dimensional visco-elastoplastic finite element models to investigate the causes of the observed crustal deformation. Our results indicate that the present-day crustal deformation in southeastern Tibetan Plateau can be largely explained by gravitational spreading.

Present-day tectonic activity along the central section of the Altyn Tagh fault derived from time series InSAR

The Altyn Tagh Fault (ATF) is a large-scale complex tectonic system. In this study, the present-day crustal deformation of the central section of the ATF (90.8°E−91.58°E) was obtained using 14 images on a descending track acquired between 2007 and 2010 from Advanced Land Observing Satellite (ALOS). To improve the accuracy of the interferograms, ALOS World 3D–30m (AW3D-30)Digital Surface Model (DSM) from the Japan Aerospace Exploration Agency was used in Small Baseline Subset (SBAS) Interferometric Synthetic Aperture Radar (InSAR) processing. The Line of Sight (LOS) deformation map show that there is an obvious zoning feature. With the main ATF as the boundary, the north block is concentrated around −35∼ −60 mm, and the south block is concentrated around −9 ∼ 11 mm. Based on the InSAR velocity map, we inverted for the strike-slip rate and locking depth of the fault using the two-dimensional strike-slip fault buried-dislocation model. The inversion results for the strike-slip rate at three selected cross-section locations perpendicular to the ATF were 6.1 mm/a, 5.3 mm/a and 7.9 mm/a from west to east; the corresponding locking depths were 9.5 km, 6.8 km and 12.3 km from west to east. The location and trend of the fault obtained by inversion are coincides with the Xorkol seismic belt.

An assessment of present-day crustal deformation in the Kumaun Himalaya from GPS observations

The India-Eurasia collision has created high mountains in the Himalayan plate boundary system, which has led to numerous earthquakes in this region and released part of the elastic strain accumulated over years. In this study, the present-day deformation pattern is derived from geodetic mode Global Positioning System (GPS) measurements obtained during 2005–2016 from 16 campaign sites in the Kumaun province of the central Himalaya. GPS derived horizontal velocity vectors are in the range of 1–9 mm/yr and 27–38 mm/yr with respect to stable India and Eurasia reference frames respectively. To understand the interseismic strain partitioning in the study region, we consider the uniform slip dislocation model over the fault in an elastic, isotropic and homogeneous half-space medium. The model indicates the Main Himalayan Thrust (MHT) fault is locked to a depth of ∼20 km and slips at a rate of 17.2 ± 1 mm/yr with a dip angle of ∼7°. This MHT slip rate build-up corresponds to a moment deficit of 8.4 ± 1 × 1018 Nm/yr due to locking of the fault beneath the Kumaun Himalaya. The total seismic strain accumulation of 61 × 10−6 estimated from the geodetic data suggests the possibility of large earthquakes (typically magnitude 8 and above) with the recurrence interval of around 600 years in the Kumaun Himalayan region.

Present-day crustal deformation and geodetic strain in the vicinity of Dholavira - Harappan civilization site, Kachchh, western part of the Indian plate

To understand the geodynamics in the vicinity of Dholavira, a Harappan Civilization Site (HCS), in Kachchh - western India, GPS data from 2009 to 2015 were processed and analyzed. Tectonically, this part of northern Kachchh is in the influence of Island Belt Fault (IBF) and Allah Bund Fault (ABF) and is seismically one of the most active intra-plate regions of India. The motion with respect to Indian plate is used for the estimation of deformation and strain rate while fault associated slip rate has been estimated by inverse modeling of observed site motions. The analysis reveals that the ABF deforms with an average rate of 1.8 mm/yr. However, the segmented IBF has a maximum deformation rate of 2.9 mm/yr towards the Pachham Island and minimum towards the Khadir Island. The computation discloses a maximum seismic moment (M0) of 2.1 × 1024 dyne-cm in this part which corresponds to an earthquake of ≈Mw 6.0. The calculated maximum strain of 0.04 micro-strain/year is low but significant in the intra-plate region. The postseismic deformation, after the Mw 7.7, 2001 Bhuj earthquake is estimated to be low in this part. The reverse along with strike-slip motion of faults builds up stress in the area and accumulating more strain.

Present-day crustal deformation characteristics of the southeastern Tibetan Plateau and surrounding areas by using GPS analysis

The southeastern Tibetan Plateau and surrounding areas comprise a typical tectonic belt in mainland China, characterized by a complex geological background and intense tectonic activity. We study present-day crustal deformation characteristics of this region based on GPS data for the periods 1999–2007 and 2009–2011. We first analyze the variations in crustal motion and strain rate, and then discuss the 3D crustal motion and local sub-block activities, as well as the correlation between the intensity of crustal activity and the strain rate distribution. Finally, we explain the present-day geodynamic characteristics of the region. Our results indicate that the entire region shows overall clockwise motion with respect to the stable Eurasian Plate. The tectonic boundary belts between this region and the South China Block display significant compressional strain, accompanied by associated extensional strain. Relatively high maximum shear strain and the transition zones of the significant plane strain gradients are also mainly concentrated along the Ganzi–Yushu–Xianshuihe, Anninghe–Zemuhe–Xiaojiang, Lijiang–Xiaojinhe, and Red River faults, as well as the western and southern Yunnan Province. 3D crustal velocities further reflect significant differences in tectonic activity between different structural belts. We conclude that the regions showing higher shear strain and the transition zones of the significant plane strain gradients correspond to the areas with frequent earthquakes. According to the crustal deformation and strain characteristics, we infer that the present-day geodynamic setting of the region is related to the ongoing India–Eurasia collision and the associated resistance of the stable Alashan, Ordos, and South China blocks, resulting in the extrusion of the southeastern Tibetan Plateau crustal material with an overall clockwise flow around the Eastern Himalayas and significant compressional strain along the tectonic boundary belts. Furthermore, notable compressional strain and enhanced sub-block motions occurred around the Longmenshan fault area following the Wenchuan earthquake.

Present-day crustal deformation and strain transfer in northeastern Tibetan Plateau

The three-dimensional present-day crustal deformation and strain partitioning in northeastern Tibetan Plateau are analyzed using available GPS and precise leveling data. We used the multi-scale wavelet method to analyze strain rates, and the elastic block model to estimate slip rates on the major faults and internal strain within each block. Our results show that shear strain is strongly localized along major strike-slip faults, as expected in the tectonic extrusion model. However, extrusion ends and transfers to crustal contraction near the eastern margin of the Tibetan Plateau. The strain transfer is abrupt along the Haiyuan Fault and diffusive along the East Kunlun Fault. Crustal contraction is spatially correlated with active uplifting. The present-day strain is concentrated along major fault zones; however, within many terranes bounded by these faults, intra-block strain is detectable. Terranes having high intra-block strain rates also show strong seismicity. On average the Ordos and Sichuan blocks show no intra-block strain, but localized strain on the southwestern corner of the Ordos block indicates tectonic encroachment.