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.
Well-constrained fault slip rates are important for understanding strain partitioning within a fault system and the associated seismic hazard. The Haiyuan fault is a significant active strike-slip fault in the northeast margin of the Tibetan Plateau with ongoing controversy over its late Pleistocene slip rate. Previous work by Lasserre et al. (1999) suggested a slip rate of 12 ± 4 mm/year, which is higher than recent geodetically determined rates on adjacent fault sections. We reanalyze and reevaluate the slip rates benefiting from new high-resolution airborne Light Detection and Ranging data at their two sites, located north of the Songshan village. Based on this data, we revise field-mapped offset constraints. At the Majia Wan site, we document a sinistral displacement of 130 ± 10 m of the crest and 93 ± 15 m of the base of T1/T2 terrace riser, respectively. At the Xuanma Wan site, the offset of T4/T1′ terrace riser is updated to be 68 +3 / −10 m. Combining new geochronology dates, we assess the abandonment age of T2 as 26.0 ± 4.5 ka and T1 as 9,445 ± 30 year. These data suggest a slip rate between 5.0 +1.5 / −1.1 and 8.9 +0.5 / −1.3 mm/year since~26 ka, based on the upper terrace and lower terrace reconstruction, respectively. Our reevaluation supports that apparent slip rate discrepancies in northern Tibet possibly share a systematic bias due to the use of lower-terrace reconstruction to interpret the age of offset.
Key Points:• Slip rate of the Haiyuan fault near longitude 37°is determined to be between 5.0 and 8.9 mm/year over the last~26 ka • Lower bound in geologic slip rate is similar to geodetic strain rate Supporting Information:• Supporting Information S1• Data Set S1
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