Search Results (3)

The location of the main boundary fault of the Yadong-Gulu Rift (YGR) shifts from the east side in the southern segment to the west side in the northern segment. The Nyemo Graben Group (NGG) connects the southern and northern segments of the YGR and provides clues for understanding the migration of boundary fault locations along the YGR. However, the NGG has received very little attention. In this study, we map the geometry of the Pabu normal fault, which is the boundary fault of the westernmost graben in the NGG, using high-resolution remote sensing images. We then utilized a digital elevation model (DEM) with a spatial resolution of 1 m. Morphometric parameters such as scarp height, width, and slope were obtained from elevation profiles in three typical deformation regions. Our results reveal a fault segment approximately 3 km long that links the southern and northern segments of the Pabu Fault. Each fault segment could be a major segment. Furthermore, based on regional tectonic activity, the Pabu Fault has the potential to produce an earthquake with a magnitude of around M 6.7. Full article

We applied teleseismic tomography to investigate the 3D P-wave velocity (Vp) structure of the crust and upper mantle at depths of 50–400 km beneath the Yarlung–Tsangpo suture (YTS), by using 6164 P-wave relative travel-time residuals collected from 495 teleseismic events recorded at 20 three-component broadband seismograms. A modified multi-channel cross-correlation method was adopted to automatically calculate the relative arrival-time residuals of all teleseismic events, which significantly improved the efficiency and precision of the arrival-time data collection. Our results show that alternating low- and high-Vp anomalies are visible beneath the Himalayan and Lhasa blocks across the YTS, indicating that strong lateral heterogeneities exist beneath the study region. A significant high-Vp zone is visible beneath the southern edge of the Lhasa block at 50–100 km depths close to the YTS, which might indicate the rigid Tibetan lithosphere basement. There exists a prominent low-Vp zone beneath the Himalayan block to the south of the YTS extending to ~150 km depth, which might be associated with the fragmentation of the underthrusting Indian continental lithosphere (ICL) and induce localized upwelling of asthenospheric materials from the upper mantle. In addition, significant low-Vp anomalies were observed beneath the Yadong–Gulu rift and the Cona–Sangri rift extending to ~300 km depth, indicating that the tearing of the subducted ICL might provide pathways for the localized asthenospheric materials upwelling, which contributes to the widespread distribution of north–south trending rifts and geothermal activities in southern Tibet. Full article

Most current crustal deformation models do not account for topographic effects, crustal lateral variations, and complex fault geometries. To overcome these limitations, we apply finite element models constrained by interferometric Synthetic Aperture Radar (InSAR) images of co-seismic displacements to the 2008 M_w 6.3 Dangxiong earthquake that occurred in Yadong–Gulu rift, southern Tibet. For mountainous plateau environments, InSAR observations are advantageous for studying crustal deformation and crustal medium structure. We evaluate the effect of topography and variations in Poisson’s ratio and elastic moduli on estimation of coseismic deformation from InSAR observations. The results show that coseismic surface displacements are more sensitive to variations in Young’s modulus than to variations in topography and Poisson’s ratio. Therefore, with constant Poisson’s ratio and density, we change the Young’s modulus on each side of the fault to obtain the model that best fits the observations. This is attained when the Young’s moduli in the eastern and western sides of the fault were 2.6 × 10¹⁰ Pa and 7.8 × 10¹⁰ Pa, respectively. The result is consistent with previous field surveys that the medium on either side of the fault is different. Full article