Paleoseismic events and ages revealed by the Lianhuashan trench in the western section of the Tuyouqi of the Daqingshan piedmont fault

Daqingshan piedmont fault is located in the northern margin of Hetao basin and has been active strongly since the Late Quaternary. Previous researchers had conducted extensive research on the characteristics of paleoseismic in this area, but limited by the dating techniques and the fact that there were fewer data available on the same fault profile that can effectively constrain paleoseismic events, and fewer profiles that can reveal more paleoseismic events. This paper explores the excavation of an paleoseismic trench on the east side of Lianhuashan in the western section of Tuyouqi of the Daqingshan piedmont fault, using Optically Stimulated Luminescence data, and combineing with the age data of previous exploration trenches. By using the fault successive limit method, it is found that the western section of the Tuyouqi fault has experienced five paleoseismic events approximately 11500 years ago, with an average recurrence interval of 2260 years. The five paleoseismic events in this section of the fault, from new to old, are 1.28 to 1.42 ka, 3.41 to 3.60 ka, 4.08 to 5.01 ka, 8.26 to 9.32 ka, and 10.70 to 11.30 ka, respectively. The latest event of activity should be the earthquake of 849 AD. Meanwhile, the trench exploration revealed that the fault in this section exhibits a normal fault nature, with an inclination angle between 58 and 77 degrees. According to empirical formula, the potential seismic capacity of the Baotou section, the western section of Tuyouqi, and the western section of Tuzuoqi are around MW6.8～7.1, MW6.8～7.1 and MW7.1～7.2, respectively. The magnitude obtained by the empirical formula in this paper is relatively small, and there may be cascade rupture. In the later stage, it is necessary to conduct a comprehensive evaluation of the risk of the western section of Daqingshan piedmont fault combined with other means

Late Quaternary Slip Rate of the Zihong Shan Branch and Its Implications for Strain Partitioning Along the Haiyuan Fault, Northeastern Tibetan Plateau

International audienceGeometrical complexities such as bends and branches are ubiquitous along strike-slip faults. Understanding strain partitioning between the different fault strands along such sections is key to assessing kinematics and evolution through time of a fault system and related seismic hazards. The Haiyuan fault, one of the longest strike-slip faults of the Tibetan Plateau, has developed a multi-stranded complex fault geometry along the Hasi Shan restraining bend. In this study, we quantified the slip rate of the ∼50-km-long Zihong Shan fault, which is the poorly-known southernmost fault strand of the Hasi Shan restraining bend. We computed high-resolution DEMs and orthophotos to document the offset landforms along this fault using drone surveys. At selected sites with well-preserved offset geomorphic markers, we quantified displaced terraces and channels using microtopography analysis. We dated the abandonment age of these terraces using 10Be cosmogenic depth profiles and OSL dating techniques. It yields a left-lateral slip rate of 1.9 ± 0.6 mm/yr since ∼13 ka, which is similar to the rate of the main Hasi Shan branch that ruptured during the 1920 Haiyuan earthquake. The minimum total horizontal slip rate system summed over the multiple strands of the Haiyuan fault at the Hasi Shan restraining bend is 4.1 ± 0.6 mm/yr, without considering the vertical deformation rate of these fault strands. The rate is thus slightly smaller than, but comparable to, slip-rates determined along the rest of the Haiyuan fault, east and west of the Hasi Shan restraining bend

Discussion on the magnitude or intensity limitation of paleoearthquake events

The magnitude is an important parameter that characterizes the size of earthquakes. However, in paleoearthquake studies, it is difficult to precisely determine the rupture parameters closely related to seismic moment, making it challenging to directly calculate the magnitude of events. Researchers often assume that event sequences consist of characteristic earthquakes with similar magnitudes or use empirical relationships based on known magnitudes of historical earthquakes to estimate magnitudes. However, previous studies have shown that the assumption of characteristic earthquakes is overly simplistic, and magnitude estimation based on empirical relationships is limited by various errors. Therefore, there is a pressing need to explore new methods to improve the reliability of magnitude assessments for ancient earthquake events. In recent years, the successful application of three-dimensional combination trenches has demonstrated that these trenches contain rich deformation information about events, confirming the feasibility of assessing event sizes within trenches. Using the example of the Copper Mine trench on the Altyn Tagh fault, this article utilizes the deformation intensity revealed within the trench, including vertical displacement, deformation zone width, and total tensile strain, to estimate the scale of the event sequence. Data analysis results indicate that the deformation intensity parameters have a certain positive correlation with the relative magnitude, and there is also some correlation among these parameters. Therefore, the information on deformation intensity within the trench can be used to assess the relative magnitude of events, and fully exploring the deformation information within trenches can provide valuable insights and references for the reasonable evaluation of the magnitude of paleoearthquake events. This underscores the importance of considering such information in paleoearthquake research

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

International audienceWell-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

Full-Length Transcriptome Sequencing Reveals the Impact of Cold Stress on Alternative Splicing in Quinoa

Quinoa is a cold-resistant and nutrient-rich crop. To decipher the cold stress response of quinoa, the full-length transcriptomes of the cold-resistant quinoa variety CRQ64 and the cold-sensitive quinoa variety CSQ5 were compared. We identified 55,389 novel isoforms and 6432 novel genes in these transcriptomes. Under cold stress, CRQ64 had more differentially expressed genes (DEGs) and differentially alternative splicing events compared to non-stress conditions than CSQ5. DEGs that were specifically present only in CRQ64 were significantly enriched in processes which contribute to osmoregulation and ROS homeostasis in plants, such as sucrose metabolism and phenylpropanoid biosynthesis. More genes with differential alternative splicing under cold stress were enriched in peroxidase functions in CRQ64. In total, 5988 transcription factors and 2956 long non-coding RNAs (LncRNAs) were detected in this dataset. Many of these had altered expression patterns under cold stress compared to non-stress conditions. Our transcriptome results demonstrate that CRQ64 undergoes a wider stress response than CSQ5 under cold stress. Our results improved the annotation of the quinoa genome and provide new insight into the mechanisms of cold resistance in quinoa

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

International audienceTo better constrain the long-term millennial slip-rate of the Haiyuan fault in its central part, we revisit the site of Daqing (or Sangedun at 102.7°E in Gaudemer et al., 1995). We used terrestrial LiDAR to build a high-resolution DEM and Uncrewed Aerial Vehicle to build an aerial photomosaic with ~0.1 m resolution to survey the offset terraces, their geomorphology and the fault trace. We refine the geomorphological interpretation of the site, measure terrace riser offsets and determine their relation to terrace formation. The well-constrained age of the highest terrace T3 at 13.7 ± 1.5 ka determined from the combination of surface and sub-surface OSL, 14 C, and terrestrial in situ 10 Be cosmogenic radionuclide (CRN) dating, associated with an offset of 88 m, yields a late Pleistocene minimum slip-rate of 6.5 ± 1 mm/yr. The less well constrained offset (9.3 ± 0.6 ka) of terrace T2 yield a maximum slip rate of 7.7 ± 0.6 mm/yr. The smallest offset of a gully incised into T1 of 6.0 ± 0.5 m is potentially associated with the most recent slip event that occurred in the last millennia. The Daqing site provides a well constrained slip rate of the Haiyuan fault that is consistent with geodetic estimates. Overall, the high-resolution topography and precise chronology at the same site makes it possible to reveal the geomorphic complexities of terrace riser offsets and post-depositional evolution, and to show how previous geological rates along the fault were both under-and overestimated

Mapping of Soil Liquefaction Associated with the 2021 Mw 7.4 Maduo (Madoi) Earthquake Based on the UAV Photogrammetry Technology

The 2021 Mw 7.4 Maduo (Madoi) earthquake that struck the northern Tibetan Plateau resulted in widespread coseismic deformation features, such as surface ruptures and soil liquefaction. By utilizing the unmanned aerial vehicle (UAV) photogrammetry technology, we accurately recognize and map 39,286 liquefaction sites within a 1.5 km wide zone along the coseismic surface rupture. We then systematically analyze the coseismic liquefaction distribution characteristics and the possible influencing factors. The coseismic liquefaction density remains on a higher level within 250 m from the surface rupture and decreases in a power law with the increasing distance. The amplification of the seismic waves in the vicinity of the rupture zone enhances the liquefaction effects near it. More than 90% of coseismic liquefaction occurs in the peak ground acceleration (PGA) > 0.50 g, and the liquefaction density is significantly higher in the region with seismic intensity > VIII. Combined with the sedimentary distribution along-strike of the surface rupture, the mapped liquefaction sites indicate that the differences in the sedimentary environments could cause more intense liquefaction on the western side of the epicenter, where loose Quaternary deposits are widely spread. The stronger coseismic liquefaction sites correspond to the Eling Lake section, the Yellow River floodplain, and the Heihe River floodplain, where the soil is mostly saturated with loose fine-grained sand and the groundwater level is high. Our results show that the massive liquefaction caused by the strong ground shaking during the Maduo (Madoi) earthquake was distributed as the specific local sedimentary environment and the groundwater level changed