Abstract.Measurements of surface displacements using

Observations of relative motion in a geodetic network in Ladakh, India, and across southern Tibet indicate slow shear on the Karakorum fault, rapid east-west extension across the whole of southern Tibet, and constant arc-normal convergence between India and southern Tibet along the Himalayan arc. Measurements of ten campaign-style and six permanent sites with global positioning system (GPS) precise geodesy provide these bounds on the style and rates of the large-scale deformation in the Tibet-Himalaya region. Divergence between sites at Leh, Ladakh, India, and Shiquanhe, western Tibet, as well as slow relative motion among sites within the Ladakh network, limit right-lateral slip parallel to the Karakorum fault to only 3.4 ± 5 mm/yr. This low rate concurs with a recent estimate of 3-4 mm/yr for Late Holocene time, but disagrees with the much higher rate of 30-35 mm/yr that has been used to argue for plate-like behavior of the Tibetan Plateau. Convergence between Ladakh and the Indian subcontinent at 18.8 ± 3 mm/yr at 224° ± 17° (1σ) differs little from estimates of convergence across the central segment of the Himalaya. Finally, lengthening of the baseline between Leh, Ladakh, and Lhasa (in southeastern Tibet) at 17.8 ± 1 mm/yr or between Leh and Bayi (farther to the southeast) at 18 ± 3 mm/yr, is consistent with an extrapolation of rates of east-west extension of the Tibetan Plateau based both on shorter GPS baselines (e.g., Lhasa-Simikot) and on diverging slip vectors of earthquakes in the Himalaya. We interpret these results to indicate that Tibet behaves more like a fl uid than like a plate.

No abstract

The Shuttle Radar Topography Mission (SRTM) Digital Terrain Elevation Data (DTED) are used with the consensus view that it has a minimum vertical accuracy of 16 m absolute error at 90% confidence (Root Mean Square Error (RMSE) of 9.73 m) world-wide. However, vertical accuracy of the data decreases with increase in slope and elevation due to presence of large outliers and voids. Therefore, studies using SRTM data “as is”, especially in regions like the Himalaya, are not statistically meaningful. New data from ~200 high-precision static Global Position System (GPS) Independent Check Points (ICPs) in the Himalaya and Peninsular India indicate that only 1-arc X-Band data are usable “as is” in the Himalaya as it has height accuracy of 9.18 m (RMSE). In contrast, recently released (2014–2015) “as-is” 1-arc and widely used 3-arc C-Band data have a height accuracy of RMSE 23.53 m and 47.24 m and need to be corrected before use. Outlier and void filtering improves the height accuracy to RMSE 8 m, 10.14 m, 14.38 m for 1-arc X and C-Band and 3-arc C-Band data respectively. Our study indicates that the C-Band 90 m and 30 m DEMs are well-aligned and without any significant horizontal offset implying that area and length computations using both the datasets have identical values.