## 3 Results
### Edge Recognition on Wavelet Transform Details
In the Himalayas, crustal discontinuities are more evident near the KF and southern segments of the ALAP, and they are cut by the MCT and eastern SNF. The distribution of areas with maximum THDs obviously decreases in eastern Tibet. Only very limited discrete maximum values are found near the EHS and the NW segment of the NJF. The spatial distribution characteristics of the THD values at depths of 85 km (Figure 8) and 136 km (Figure 9) are significantly different from those in the overlying crust. This difference can also be identified in Figure 2. Previous research confirmed that the average lithospheric thickness of the study area is 85 km [13]. Thus, the tectonic depths corresponding to Figures 8 and 9 should be the bottom of the lithosphere and the top of the upper mantle. In Figure 8, the areas with maximum THDs are mainly distributed along the eastern and western margins of Tibet. The discontinuity along the Herat fault (HF) and RE in southern Pamir indicates the leading edge of the Indian plate. The discontinuities along the KKF, KF, ATF and XSDF are still evident at current depths, which indicates that these faults are major fracture structures that cut deep into the lithosphere. The lithospheres between the Himalayan tectonic zone and the EHS are obviously separated by the SNF. The areas with maximum THDs of eastern Tibet exhibit significant material discontinuities in the EHS. Combined with Figure 2g, a continuous high positive gradient belt protrudes  
Figure 6: Distributions of the total horizontal derivatives at 10 km depth. The faults’ names are listed here. Altryn Tag fault (ATF), Apalong fault (ApIF), Chaman fault (CF), Gaoligong fault (GlgF), Herat fault (HF), Haiyuan fault (HyF), Jiali fault (JIF), Talas-Fergana fault (TF), Karakash fault (KKF), Karakorum fault (KF), Kashgar-Yecheng transfer system (KYS), Nujiang fault (NJF), Nantinghe fault (NthF), Søgaing fault (SF), Sørez-Karakul fault (SKF), Xianshuihe fault (XshF); Burmese fold belt (BFB), Longmenshan thrust (LmsT), Main Central thrust (MCT), Main Frontal thrust (MFT), Pamir thrust system (PTS), Qilian Nanshan thrust (QNT), Southern Tian Shan thrust (STT); normal faults and extensional structures: Gurla-Mandhata detachment (GM), Søngri-Nacuo fault (SNF), Yadong-Gulu fault (YGF); Anyimaqen-Kunlun-Muztagh suture zone (AMS), Bangonghu-Nujiang suture zone (BNS), Jinshaiang suture zone (JS), Rushan-Pshart suture zone (RE), Shyok suture zone (SSZ), Yalu-Zangbo suture zone (YZYS). into the negative anomalies and separates the negative anomalies into several discrete segments. The source depth in Figure 9 corresponds to the upper mantle in the study area. The spatial distributions of the maximum THD at this depth show significant differences between the Pamir Plateau and Tibetan Plateau. The tectonic discontinuities in the Pamir Plateau are much more significant than those in the Tibetan Plateau. In detail, the lithospheric discontinuities of the Pamir Plateau are mainly distributed north of the MFT and extend northeastward to the southern Tian Shan thrust (STT), KYS and KKF, which form the western boundary of the Tarim basin and indicate the existence of structural discontinuities between the two major tectonic units. Such a pattern of maximum values exhibits the leading-edge characteristics of the subducting Indian plate. In the Tian Shan range, the maximum THDs are mostly distributed west of the TF, which is also revealed by the spatial distribution of the Bouguer gravity anomalies shown in Figure 2g. In addition, the Tajik-Afghan basin and the Tarim basin are relatively intact compared with the Pamir Plateau. On the Tibetan Plateau, the pattern of maximum values is approximately elliptical; the major axes are consistent with the directions of regional tectonic structures and display evident clockwise rotation near the EHS. The most significant characteristic of eastern Tibet is that the maximum values form a gradient belt that is distributed along the Gaoligong fault (GlgF) and Sagaing fault (SF).