## 3 Results
### Edge Recognition on Wavelet Transform Details  
Discontinuities in lithospheric materials and active fault distributions at different depths can be clearly recognized by the maximum values of the THD. The THD values (THDs) of the boundary zone between the Indian plate and Eurasian plate are higher than those of the surrounding crust in Figure 3. In the Pamir Plateau, the maximum values are \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Number of Orders** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline
**Field depth (km)** & 0.5 & 2.5 & 6.5 & 10 & 17 & 85 & 136 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The estimates of approximate field source depths. Figure 2: Wavelet decomposition of Bouguer gravity anomalies. (**a**–**g**) are the 1 st- to 7 th-order wavelet transform details. (**h**) is the 7 th-order wavelet approximation. mainly distributed along its boundary structures, such as the Kashgarr-Yeshgar transfer system (KYS), KF, SSZ and western segment of the Pamir thrust system (PTS). The global maximum values are mostly located in front of Nanga Parbat of the WHS. In addition, the Pamir Plateau can be divided into two subunits by the N-S-trending Sarez-Karakul fault (SKF). In western Pamir, the maximum values are more obvious than those in the east, which indicates that the crust in western Pamir is much more broken than the eastern crust. On the Tibetan Plateau, the maximum THD values are mainly distributed within the Himalayan tectonic zone south of the KF and YZYS. The THD values over the Gurlad-Mandhata detachment (GM) and along a series of N-S-trending normal faults, such as the Sangri-Nacuo fault (SNF) and YGF, are much higher than those of the crust of the immediate neighborhood. On the eastern boundary of the Tibetan Plateau, the intersection position of the Apalong fault (ApIF) and JIF in the EHS as well as the NjF and Xianshihe (XshF) also exhibit evident material discontinuities, which indicate the presence of structural discontinuities along the abovementioned structures. The Qilian-Nanshan fault (QNT) on the northeastern margin of the Tibetan Plateau appears in Figure 4. Tectonic discontinuities in western Pamir become more significant and widespread. In the mid-Himalayas, the material discontinuities are still concentrated on the GM and N-S normal faults. On the eastern boundary of the Tibetan Plateau, crustal discontinuities along the JIF between the YZYS and Apalong fault (ApIF) are significant. Figure 3: Distributions of the total horizontal derivatives at 0.5 km depth. The faults’ names are listed here. Altryn Tagh 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), Sagaging fault (SF), Sarez-Karakul fault (SKF), Xianshuie 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), Sangri-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). The NJF, AnhF, XshF and Longmenshan thrust (LmsT) become more evident than in the shallower crust. The crustal discontinuities of the Tian Shan range are still not evident except in Aksu, China in Figure 5. The area with maximum THDs in western Pamir is significant, and the gradient belt extends farther southward into the Hindukush area. The discontinuities near the WHS are mostly limited to the south of the Rushan Pshart suture zone (RE). The discontinuities between the Pamir Plateau and the Tarim basin become indistinct.