Based on field investigations, interpretations of high‐resolution UAV images, and analyses of available InSAR data, we mapped the fault geometry and surface ruptures of the 2021 Mw 7.4 Maduo earthquake that occurred on a low‐activity strike‐slip fault within the Tibetan Plateau. The results indicate that (a) the earthquake activated a fault that is ∼161 km long and has complicated structural geometry; (b) the surface rupture occurs over a distance of 148 km, but is separated into three distinct segments by two large gaps (38 and 20 km, respectively); (c) within the surface‐rupture segments, the horizontal and vertical displacements are typically 0.2–2.6 m (much lower than the InSAR‐based slip maximum of 2–6 m at depth) and ≤0.4 m, respectively. The two large gaps of the Maduo surface rupture represent the two largest surface‐rupture discontinuities of strike‐slip earthquakes ever documented, and coincide with structurally complicated fault portions and near‐surface soft sediments.
Surface rupture in the 2019 Ridgecrest, California, earthquake sequence occurred along two orthogonal cross faults and includes dominantly left-lateral and northeast-striking rupture in the Mw 6.4 foreshock and dominantly right-lateral and northwest-striking rupture in the Mw 7.1 mainshock. We present >650 field-based, surface-displacement observations for these ruptures and synthesize our results into cumulative along-strike displacement distributions. Using these data, we calculate displacement gradients and compare our results with historical strike-slip ruptures in the eastern California shear zone. For the Mw 6.4 rupture, we report 96 displacements measured along 18 km of northeast-striking rupture. Cumulative displacement curves for the rupture yield a mean left-lateral displacement of 0.3–0.5 m and maximum of 0.7–1.6 m. Net mean vertical displacement based on the difference of down-to-the-west (DTW) and down-to-the-east (DTE) displacement curves is close to zero (0.02 m DTW). The Mw 6.4 displacement distribution shows that the majority of displacement occurred southwest of the intersection with the Mw 7.1 rupture. The Mw 7.1 rupture is northwest-striking and 50 km long based on 576 field measurements. Displacement curves indicate a mean right-lateral displacement of 1.2–1.7 m and a maximum of 4.3–7.0 m. Net vertical displacement in the rupture averages 0.3 m DTW. The Mw 7.1 displacement distributions demonstrate that maximum displacement occurred along a 12-km-long portion of the fault near the Mw 7.1 epicenter, releasing 66% of the geologically based seismic moment along 24% of the total rupture length. Using our displacement distributions, we calculate kilometer-scale displacement gradients for the Mw 7.1 rupture. The steepest gradients (∼1–3 m/km) flank the 12-km-long region of maximum displacement. In contrast, gradients for the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes are <0.6 m/km. Our displacement distributions are important for understanding the influence of cross-fault rupture on Mw 6.4 and 7.1 rupture length and displacement and will facilitate comparisons with distributions generated remotely and at broader scales.
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.
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