Reevaluation of the Late Pleistocene Slip Rate of the Haiyuan Fault Near Songshan, Gansu Province, China

Abstract

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

Systematic Search for Repeating Earthquakes Along the Haiyuan Fault System in Northeastern Tibet

“…We found that the largest slip rate is 6.6 mm/year and the average slip rate is 2.25 ± 2.24 mm/year. Although with large uncertainties, our estimated slip rate is less than the shallow creep rate of~5 mm/year from InSAR observations (Jolivet et al, 2013) and geological rate of 5-9 mm/year (Yao et al, 2019).…”

A New Tectonic Model for the 1927M8.0 Gulang Earthquake on the NE Tibetan Plateau

“…Additionally, the fault planes of the two faults are steep (Li et al, 2013, 2017; Liu‐Zeng et al, 2007). The strain is then partitioned into left‐lateral shearing on the Qilian‐Haiyuan and Xiangshan‐Tianjingshan faults, and Qilian‐Haiyuan fault has a larger late Quaternary slip rate than Xiangshan‐Tianjianshan fault (Guo et al, 2017; Li et al, 2017; Yao et al, 2019; Zheng et al, 2013; Figure 17b).…”

Late Pleistocene slip rate of the central Haiyuan fault constrained from optically stimulated luminescence, 14C, and cosmogenic isotope dating and high-resolution topography

“…Along the Maomao Shan segment, Lasserre et al (1999) determined a slip rate of 12 ± 4 mm/yr, while Yuan et al (1998) estimated lower slip rates of 4.1-5.4 mm/yr. Yao et al (2019) recently reassessed the offsets and age control for sites of Lasserre et al (1999) and updated the slip rate here to 5-8.9 mm/yr over the late Pleistocene -Holocene. Further east, the Haiyuan segment, which ruptured in the 1920 Haiyuan earthquake, was assigned a slip rate of 8 ± 2 mm/yr by Zhang et al (1988b).…”