Explore the vast range of titles available.

Using seismic data of about one year recorded by 18 broadband stations of ASCENT project, we obtained 2547 receiver func- tions in the northeastern Tibetan Plateau. The Moho depths under 14 stations were calculated by applying the H-x domain search algorithm. The Moho depths under the stations with lower signal-noise ratio （SNR） were estimated by the time delay of the PS conversion. Results show that the Moho depth varies in a range of -40--60 kin. The Moho near the Haiyuan fault is vague, and its depth is larger than those on its two sides. In the Qinling-Qilian Block, the Moho becomes shallower gradually from west to east. To the east of 105~E, the average depth of the Moho is 45 km, whereas the west is 50 km or even deeper. Combining our results with surface wave research, we suggest a boundary between the Qinling and the Qilian Mountains at around 105~E. S wave velocities beneath 15 stations have been obtained through a linear inversion by using Crust2.0 as an ini- tial model, and the crustal thickness that was derived by H-x domain search algorithm was also taken into account. The results are very similar to the results of previous active source studies. The resulting figure indicates that low velocity layers devel- oped in the middle and lower crust beneath the transition zone of the Tibet Block and western Qinling, which may be related to regional faults and deep earth dynamics. The velocity of the middle and lower crust increases from the Songpan Block to the northeastern margin of Tibetan Plateau. Based on the velocity of the crust, the distribution of the low velocity zone and the composition of the curst （Poisson＇s ratio）, we infer that the crust thickening results from the crust shortening along the direc- tion of compression.

Based on the polarization analysis of teleseismic data,SKS （SKKS） fast-wave directions and delay times between fast and slow shear waves were determined for each of the 111 seismic stations from both permanent and temporary broadband seismograph networks deployed in the Ordos Block and its margins.Both the Silver and Chan and stacking analysis methods were used.In this way,an image of upper mantle anisotropy in the Ordos Block and its margins was acquired.In the western and northern margins of the Ordos Block,the fast-wave directions are consistently NW-SE.The fast-wave directions are mainly NWW-SEE and EW in the southern margin of the Ordos Block.In the eastern margin of the Ordos Block,the fast-wave directions are generally EW,although some run NEE-SWW or NWW-SEE.In the Ordos Block,the fast-wave directions trend near N-S in the north,but switch to near EW in the south.The delay time between fast and slow waves falls into the interval 0.48-1.50 s,and the average delay time at the stations in the Ordos Block is less than that in its margins.We suggest that the anisotropy of the stable Ordos Block is mainly caused by ＂fossil＂ anisotropy frozen in the ancient North China Craton.The NE-trending push of the northeastern margin of the Tibetan Plateau has caused NW-SE-trending lithospheric extension in the western and northern margins of the Ordos Block,and made the upper mantle flow southeastwards.This in turn has resulted in the alignment of the upper mantle peridotite lattice with the direction of material deformation.In the southern margin of the Ordos Block,the collision between the North China and Yangtze blocks resulted in the fast-wave direction running parallel to the collision boundary and the Qinling Orogen.Combining this with the APM and velocity structure of the Qinling Orogen,we propose that eastward-directed asthenospheric-mantle channel flow may have occurred beneath the Qinling Orogen.In the eastern margin of the Ordos Block,the complex anisotropic characteristics of the Fenhe Graben and Taihang Orogen may be caused by the interaction of western Pacific Plate subduction,regional extensional tectonics,and the orogeny.For station YCI,the apparent splitting parameters （the fast-wave directions range from 45° to 106° and the delay times range from 0.6 to 1.5 s） exhibit systematic variations as a function of incoming polarization with a periodicity of π/2.This variation can be best explained by a two-layer anisotropic model （φlower=132°,δtlower=0.8 s,φupper=83°,δtupper=0.5 s）.The upper layer anisotropy beneath station YCI can again be attributed to ＂fossil＂ anisotropy frozen in the ancient North China Craton.The lower layer anisotropy is affected by the tectonic activity of the western Ordos Block.The NW-SE trending extension caused by the NE trending push of the northeastern margin of the Tibetan Plateau affected the deformation of the lower anisotropic layer beneath station YCI.By comparing the fast-wave directions with GPS velocity directions,we see that the crust and upper mantle possibly have vertically coherent deformation in the margins of the Ordos Block,whereas the internal deformation characteristics of the Ordos Block are complex and require further study.

Snowline change and snow cover distribution patterns are still poorly understood in steep alpine basins of the Qilian Mountainous region because fast changes in snow cover cannot be observed by current sensing methods due to their short time scale. To address this issue of daily snowline and snow cover observations, a ground- based EOS 7D camera and four infrared digital hunting video cameras （LTL5210A） were installed around the Hulugou river basin （HRB） in the Qilian Mountains along northeastern margin of the Tibetan Plateau （38°15′54″N, 99°52′53″E） in September 2011. Pictures taken with the EOS 7D camera were georeferenced and the data from four LIL521oA cameras and snow depth sensors were used to assist snow cover estimation. The results showed that the time-lapse photography can be very useful and precise for monitoring snowline and snow cover in mountainous regions. The snowline and snow cover evolution at this basin can be precisely captured at daily scale. In HRB snow cover is mainly established after October, and the maximum snow cover appeared during February and March. The consistent rise of the snowline and decrease in snow cover appeared after middle part of March. This melt process is strongly associated with air temperature increase.

Heavy summer rainfall induces significant soil erosion and shallow landslide activity on the loess hillslopes of the Xining Basin at the northeast margin of the Qinghai-Tibet Plateau. This study examines the mechanical effects of five native shrubs that can be used to reduce shallow landslide activity. We measured single root tensile resistance and shear resistance, root anatomical structure and direct shear and triaxial shear for soil without roots and five root- soil composite systems. Results show that Atriplex canescens （Pursh） Nutt. possessed the strongest roots, followed by Caragana korshinskii Kom., Zygophyllum xanthoxylon （Bunge） Maxim., Nitraria tangutorum Bobr. and Lycium chinense Mill. Single root strength and shear resistance relationships with root diameter are characterized by power or exponential relations, consistent with the Mohr- Coulomb law. Root mechanical strength reflects their anatomical structure, especially the percentage of phloem and xylem cells, and the degree and speed of periderm lignifications. The cohesion force of root- soil composite systems is notably higher than that of soil without roots, with increasing amplitudes of cohesion force for A. canescens, C. korshinskii, Z. xanthoxylon, N. tangutorurn and L. chinense of 75.9%, 75.1%, 36.2%, 24.6% and 17.0 % respectively. When subjected to shear forces, the soil without root samples show much greater lateral deformation thanthe root-soil composite systems, reflecting the restraining effects of roots. Findings from this paper indicate that efforts to reduce shallow landslides in this region by enhancing root reinforcement will be achieved most effectively using A. canescens and C. korshinskii.

The third terrace of the Yellow River was well developed in Xunhua basin in the north-east margin of the Tibetan Plateau. The terrace was formed at ca 75 ka as dated by the optically stimulated luminescence (OSL) method. On the basis of grain size, magnetic susceptibility and palynological data, six episodes of the climatic change were identified in Xunhua basin; they include very warm and humid period during 120–114 ka, cool and dry period during 114–105 ka, warm and humid period during 105–98 ka, gradually cooling period during 98–85 ka, warm and humid period during 85–75 ka, very cold and dry period during 75–63 ka. The six stages of climatic change recorded in Xunhua basin correspond to the marine oxygen isotope stages (MIS) of 5e, 5d, 5c, 5b, 5a and 4, respectively.