Based on a 2 year seismic record from a local network, we characterize the deformation of the seismogenic crust of the Pamir in the northwestern part of the India-Asia collision zone. We located more than 6000 upper crustal earthquakes in a regional 3-D velocity model. For 132 of these events, we determined source mechanisms, mostly through full waveform moment tensor inversion of locally and regionally recorded seismograms. We also produced a new and comprehensive neotectonic map of the Pamir, which we relate to the seismic deformation. Along Pamir's northern margin, where GPS measurements show significant shortening, we find thrust and dextral strike-slip faulting along west to northwest trending planes, indicating slip partitioning between northward thrusting and westward extrusion. An active, north-northeast trending, sinistral transtensional fault system dissects the Pamir's interior, connecting the lakes Karakul and Sarez, and extends by distributed faulting into the Hindu Kush of Afghanistan. East of this lineament, the Pamir moves northward en bloc, showing little seismicity and internal deformation. The western Pamir exhibits a higher amount of seismic deformation; sinistral strike-slip faulting on northeast trending or conjugate planes and normal faulting indicate east-west extension and north-south shortening. We explain this deformation pattern by the gravitational collapse of the western Pamir Plateau margin and the lateral extrusion of Pamir rocks into the Tajik-Afghan depression, where it causes thin-skinned shortening of basin sediments above an evaporitic décollement. Superposition of Pamir's bulk northward movement and collapse and westward extrusion of its western flank causes the gradual change of surface velocity orientations from north-northwest to due west observed by GPS geodesy. The distributed shear deformation of the western Pamir and the activation of the Sarez-Karakul fault system may ultimately be caused by the northeastward propagation of India's western transform margin into Asia, thereby linking deformation in the Pamir all the way to the Chaman fault in the south in Afghanistan.

Models of continental breakup remain uncertain because of a lack of knowledge of strain accommodation immediately before breakup. Our new three-dimensional seismic velocity model from the Main Ethiopian rift clearly images mid-crustal intrusions in this active, transitional rift setting, supporting breakup models based on dike intrusion and magma supply. The most striking features of our velocity model are anomalously fast, elongate bodies (velocity, V p ϳ6.5-6.8 km/s) extending along the rift axis, interpreted as cooled mafic intrusions. These 20-km-wide and 50-km-long bodies are separated and laterally offset from one another in a right-stepping en echelon pattern, approximately mimicking surface segmentation of Quaternary volcanic centers. Our crustal velocity model, combined with results from geologic studies, indicates that below a depth of ϳ7 km extension is controlled by magmatic intrusion in a ductile middle to lower crust, whereas normal faulting and dike intrusion in a narrow zone in the center of the rift valley control extension in the brittle upper crust. This zone is inferred to be the protoridge axis for future seafloor spreading.

34The discharge of the central Himalayan rivers is governed by a strong precipitation seasonality 35 3,6,9,10 ( Fig. 1) with up to 80% of the annual rainfall occurring during the Indian Summer Monsoon 36(ISM) season 3 . The ISM precipitation is the main source for glacier mass accumulation 9 and its spatial 37 distribution is strongly influenced by orographic effects 3 48We investigate the transfer of water within the main catchments of the Nepal Himalayas (Fig. 49 1a) using a daily meteorological and hydrological dataset spanning ~30 years (Table 1). We consider 50 the three main catchments of Nepal (Sapta Koshi, Narayani and Karnali basins), some of their 51 tributaries, and three unglaciated small catchments at the front of the Himalayan range ( Fig. 1a and 52 Table 1). The main catchments drain the entire Himalayan range of Nepal, from the Tibetan Plateau to 53 the Lesser Himalayas. Most of their headwaters are located on the arid Plateau (Fig. 1a) (Fig. 1c). Most of the data considered here come from outlet stations located to the north of 58 the Siwalik foreland. The annual specific discharge of the studied basins is typically on the order of 59 ~10 3 mm yr -1 (Table 1) and their annual hydrograph clearly shows the seasonal impact of the ISM on 60 river discharge, generally peaking in July/August 3,14 (Fig. 1b). Mean annual basin precipitation is 920, 611396 and 920 mm yr -1 in the Sapta Koshi, Narayani and Karnali catchments, respectively. However, 62 precipitation is spatially heterogeneous (Fig. 1a) and is strongly controlled by orography, reaching a 63 maximum between elevations of 2 to 3 km 15,16 . The upper parts of the catchments are glaciated (Fig. 64 1a), covering between 4 and 15 % of the catchment area (Table 1). 66We calculated mean basin-wide daily precipitation rate and use daily discharge measurements 67 to compute specific water discharge for all the studied drainage basins (see Methods). Plots of daily 68 precipitation vs. specific discharge highlight a considerable scatter within the ~30 year dataset ( (Fig. 2a). A 30-day moving average highlights the temporal 74 consistency of the loop from year to year (Fig. 2a, inset). Data scattering results from inter-annual 75 variability, particularly during post-ISM, as illustrated by comparing the data during a strong or a weak 76 ISM year (see Supplementary Fig. S1). The annual anticlockwise hysteresis loop is observed in all 77 studied basins (Fig. 2b), regardless of the geological units, the presence of glaciers or snow cover 78 (Tab. 1). 80Anticlockwise hysteresis loops imply that precipitation is temporarily stored within the 81 catchments and not transferred directly to the river during pre-ISM and ISM seasons, whereas the 82 storage compartment is drained during post-ISM. Glaciers can be directly ruled out as the main 83 contributor to the observed hysteresis effect because the release of water by glacier or snow melt 84 occurs principally during pre-ISM to ISM season 3,13 ( Fig. 3b and S2), which is not consistent with the 85 ant...

Apatite fi ssion-track thermochronology data elucidate the cooling/exhumation history of the Qinling (Qin Mountains), which contain a Paleozoic−Mesozoic orogenic collage north of the Sichuan Basin and northeast of the Tibetan Plateau. In particular, we examine the extent to which the Qinling were affected by the rising plateau. The northern and eastern Qinling show continuous cooling and slow exhumation since the Cretaceous. In contrast, in the southwestern Qinling, rapid cooling initiated at 9−4 Ma, a few million years later than in the eastern Tibetan Plateau. A compilation of major Cenozoic faults in the eastern Tibetan Plateau and the Qinling, and their kinematic and dynamic characterization, shows that deformation in the Qinling has predominantly been strike slip. Active sinistral and dextral strike-slip faults delineate an area of eastward rock fl ow and bound the area of rapid late Cenozoic cooling outlined by apatite fi ssion-track thermochronology. These data can be interpreted to indicate that lower crustal fl ow has been diverted around the Longmen Shan and beneath the southwestern Qinling, causing active plateau uplift in this area. Alternatively, northeastern Tibet may be growing eastward faster in the western Qinling than the entire South China Block is extruding to the east.