Active Faulting of Landforms along the Tuosuhu-Maoniushan Fault and Its Seismotectonic Implications in Eastern Qaidam Basin, China

The fold-and-thrust belt along the northern margin of the Qaidam basin is a typical active tectonic belt located in the northeast Tibetan Plateau. This belt is at a high risk of strong earthquakes with magnitudes larger than 6, as shown by multiple recorded events during 1962–2009. The lack of detailed late Quaternary surficial faulting data and systematic seismotectonic studies has posed difficulties in properly assessing the seismic risks and understanding the ongoing geodynamics in this region. In this study, we mapped the geomorphic features and fault traces from high-resolution satellite images and field investigations of the Tuosuhu-Maoniushan fault (TMF). Field photogrammetry was conducted to obtain deformation measurements using a DJI M300 real-time kinematic (RTK) drone. The TMF displaces the Holocene and late Pleistocene alluvial terraces in the eastern Qaidam basin. This fault dips to the south in the west and central segments (as a boundary of the Denan depression) and to the north in the eastern segment along the piedmont of the Maoniushan Mountains. The vertical slip rate is estimated to be 0.37 ± 0.08 mm/yr, which is similar to that of the active southern Zongwulongshan fault. By integrating our investigations with the previously published studies on deep structures and Cenozoic geology of the region, we propose a deep-seated thrust model for the seismotectonics of the northern margin of the Qaidam basin. The Aimunike, Tuosuhu-Maoniushan, southern Zongwulongshan, and Zongwulong faults, along with many folds, form an active compressional zone. The complex across-strike structures and along-strike segmentation could facilitate the release of strain through earthquakes of magnitude 6–7 in this broad seismotectonics belt, rather than through strong surface-rupturing events resulting from a single mature large fault.

Late Quaternary Marine Terraces and Tectonic Uplift Rates of the Broader Neapolis Area (SE Peloponnese, Greece)

Marine terraces are geomorphic markers largely used to estimate past sea-level positions and surface deformation rates in studies focused on climate and tectonic processes worldwide. This paper aims to investigate the role of tectonic processes in the late Quaternary evolution of the coastal landscape of the broader Neapolis area by assessing long-term vertical deformation rates. To document and estimate coastal uplift, marine terraces are used in conjunction with Optically Stimulated Luminescence (OSL) dating and correlation to late Quaternary eustatic sea-level variations. The study area is located in SE Peloponnese in a tectonically active region. Geodynamic processes in the area are related to the active subduction of the African lithosphere beneath the Eurasian plate. A series of 10 well preserved uplifted marine terraces with inner edges ranging in elevation from 8 ± 2 m to 192 ± 2 m above m.s.l. have been documented, indicating a significant coastal uplift of the study area. Marine terraces have been identified and mapped using topographic maps (at a scale of 1:5000), aerial photographs, and a 2 m resolution Digital Elevation Model (DEM), supported by extensive field observations. OSL dating of selected samples from two of the terraces allowed us to correlate them with late Pleistocene Marine Isotope Stage (MIS) sea-level highstands and to estimate the long-term uplift rate. Based on the findings of the above approach, a long-term uplift rate of 0.36 ± 0.11 mm a−1 over the last 401 ± 10 ka has been suggested for the study area. The spatially uniform uplift of the broader Neapolis area is driven by the active subduction of the African lithosphere beneath the Eurasian plate since the study area is situated very close (~90 km) to the active margin of the Hellenic subduction zone.

Cyclic behavior of late quaternary alluvial soil along Indo-Gangetic Plain: Northern India

The A.D. 1803 and 1934 Bihar-Nepal border earthquake affected Indo-Gangetic Plain with evidences of liquefaction in cities like Patna, Varanasi, Agra, and Delhi in historical past. Recent strong shaking all along the Indo-Gangetic Plains and seismic induced damage to the buildings in Bihar during Mw 7.8 Gorkha earthquake raises the concern for site specific liquefaction potential estimation of alluvial soils. Cyclic triaxial tests were conducted on soil samples from Kanpur, Allahabad, Patna city to know the cyclic behavior, estimate the dynamic soil properties and the effect of relative density, confining pressure and frequency of loading on the cyclic behavior of the soil tested. The test results indicate the cyclic strength of Allahabad soil is less than Patna and Kanpur soil. The Allahabad soil with 80% sand, 10% silt and clay each is more prone to liquefaction than Kanpur soil (82% silt, 16% clay and 2% sand) and Patna soil (10% Kankar, 95% sand, 5% silt). This study indicates soils having sand with silt percentage are more liquefiable than clean sand or silty soil. It can be concluded that the soil of Allahabad and Patna city is more prone to liquefaction than Kanpur soil.