Streams commonly respond to base-level fall by localizing erosion within steepened, convex knickzone reaches. Localized incision causes knickzone reaches to migrate upstream. Such migrating knickzones dictate the pace of landscape response to changes in tectonics or erosional efficiency and can help quantify the timing and source of base-level fall. Identification of knickzones typically requires individual selection of steepened reaches: a process that is tedious and subjective and has no efficient means to measure knickzone size. We construct an algorithm to automate this procedure by selecting the bounds of knickzone reaches in a χ-space (drainage-area normalized) framework. An automated feature calibrates algorithm parameters to a subset of knickzones handpicked by the user. The algorithm uses these parameters as consistent criteria to identify knickzones objectively, and then the algorithm measures the height, length, and slope of each knickzone reach. We test the algorithm on 1, 10, and 30 m resolution digital elevation models (DEMs) of six catchments (trunk-stream lengths: 2.1–5.4 km) on Santa Cruz Island, southern California. On the 1 m DEM, algorithm-selected knickzones confirm 93% of handpicked knickzone positions (n = 178) to a spatial accuracy of ≤100 m, 88% to an accuracy within 50 m, and 46% to an accuracy within 10 m. Using 10 and 30 m DEMs, accuracy is similar: 88–86% to ≤100 m and 82% to ≤50 m (n = 38 and 36, respectively). The algorithm enables efficient regional comparison of the size and location of knickzones with geologic structures, mapped landforms, and hillslope morphology, thereby facilitating approaches to characterize the dynamics of transient landscapes.

The Pamir‐Tian Shan collision zone in the western Tarim Basin, northwest China, formed from rapid and ongoing convergence in response to the Indo‐Eurasian collision. The arid landscape preserves suites of fluvial terraces crossing structures active since the late Neogene that create fault and fold scarps recording Quaternary deformation. Using geologic and geomorphic mapping, differential GPS surveys of deformed terraces, and optically stimulated luminescence dating, we create a synthesis of the active structures that delineate the timing, rate, and migration of Quaternary deformation during ongoing convergence. New deformation rates on eight faults and folds, when combined with previous studies, highlight the spatial and temporal patterns of deformation within the Pamir‐Tian Shan convergence zone during the Quaternary. Terraces spanning ~130 to ~8 ka record deformation rates between ~0.1 and 5.6 mm/yr on individual structures. In the westernmost Tarim Basin, where the Pamir and Tian Shan are already juxtaposed, the fastest rates occur on actively deforming structures at the interface of the Pamir‐Tian Shan orogens. Farther east, as the separation between the Pamir‐Tian Shan orogens increases, the deformation has not been concentrated on a single structure, but rather has been concurrently distributed across a zone of faults and folds in the Kashi‐Atushi fold‐and‐thrust belt and along the NE Pamir margin, where shortening rates vary on individual structures during the Quaternary. Although numerous structures accommodate the shortening and the locus of deformation shifts during the Quaternary, the total shortening across the western Tarim Basin has remained steady and approximately matches the current geodetic rate of 6–9 mm/yr.

Bending‐moment faults and flexural‐slip faults (FSFs), as two basic fault styles due to bending‐related tangential longitudinal strain, extensively and prominently crop out as surface scarps in the Pamir‐western Kunlun and southern Tian Shan regions, northwestern China. Characteristic geomorphic expression, favorable formation conditions, and the role in folding accommodation of active FSFs have been systematically summarized in our recent studies. Here we investigate similar properties for well‐developed bending‐moment normal fault (BMnF) scarps at four sites. Our study concludes the following: (i) BMnF scarps are relatively sinuous compared to FSF scarps and probably trend obliquely to the fold hinge. A group of BMnF scarps can delineate a single asymmetric graben or create grabens alternating with horsts. (ii) BMnF scarps primarily overlie poorly‐layered conglomerates. The fold's interlimb angle can range from ~160° to <40°, and the folding kinematics can vary from active‐hinge migration to fixed‐hinge rotation. (iii) The fault‐zone width, fault spacing, and efficiency in folding accommodation significantly decrease with (a) thinner conglomerate beds, (b) a smaller interlimb angle, and (c) the transition of the hinge from migrated to fixed. (iv) Different bed lithologies and fold geometries beneath the surface account for the predominance of BMnF scarps on the western Kunlun piedmont and FSF scarps in the Pamir‐Tian Shan convergent zone. (v) Presence of BMnF scarps on the western Kunlun piedmont indicates that ~4 km of fault slip is transferred northward along a detachment at the base of the Cenozoic and is ultimately absorbed by the Mazatagh Thrust in the Tarim Basin.

The Pamir Frontal Thrust along the leading edge of the northern Pamir is characterized by multiple earthquakes with moment magnitudes of 6.5–7.1. Geometric characteristics of the Pamir Frontal Thrust corresponding to these earthquakes and to future seismic hazards, however, remain largely unexplored. This study focuses on the easternmost segment of the Pamir Frontal Thrust, where theM_w6.9 Wuqia earthquake occurred in 1985. Through interpretation of available two‐dimensional seismic reflection profiles and surface mapping data, we develop a three‐dimensional geometric model for the fault plane. Our results illustrate that, at depth, the fault plane is separated by a subhorizontal detachment horizon into upper and lower ramps, and both ramps are significantly segmented, along strike, by transfer faults or lateral ramps as well. Such along‐strike and downdip segmentation of the thrust sheet apparently plays a significant control on seismic rupture process of the Wuqia earthquake and can well explain why the region is characterized by moderate‐magnitude (M_w6.5–7.1) events. Additionally, our study helps quantify key constraints on the Cenozoic deformation and evolution of the northeastern Pamir and, specifically, determines a total shortening of ≤43 km at the Pamir front: accommodating about 15% of the total indentation of the Pamir range into central Asia.

Understanding the evolution of continental deformation zones relies on quantifying spatial and temporal changes in deformation rates of tectonic structures. Along the eastern boundary of the Pamir‐Tian Shan collision zone, we constrain secular variations of rock uplift rates for a series of five Quaternary detachment‐ and fault‐related folds from their initiation to the modern day. When combined with GPS data, decomposition of interferometric synthetic aperture radar time series constrains the spatial pattern of surface and rock uplift on the folds deforming at decadal rates of 1–5 mm/yr. These data confirm the previously proposed basinward propagation of structures during the Quaternary. By fitting our geodetic rates and previously published geologic uplift rates with piecewise linear functions, we find that gradual rate changes over >100 kyr can explain the interferometric synthetic aperture radar observations where changes in average uplift rates are greater than ~1 mm/yr among different time intervals (~10¹, 10^4–5, and 10^5–6 years).