High‐resolution topographic data sets have now become increasingly available, which allows for remotely measuring and analyzing offset features and their associated slip distributions at a very high resolution along a fault, hence providing important insights into the fault behavior. The West Helanshan Fault is a Holocene active right‐lateral strike‐slip fault located at the junction of the Tibetan Plateau, Alashan, and Ordos blocks. In this study, a 2‐m‐resolution DEM of the West Helanshan Fault was built from the WorldView‐3 stereo satellite images (0.5 m). Combined with the high‐resolution topography acquired from the Unmanned Aerial Vehicle (UAV) images based on the Structure from Motion (SfM) method, a total of 180 lateral offsets and 201 vertical displacements were acquired along ~50 km of the fault. By statistical analysis of the offset observations and constructing the cumulative slip profiles, we conclude that large paleoearthquakes have produced characteristic slip accumulation along the fault with a right‐lateral slip of ~3 m and a vertical slip of ~1 m, rupturing at least two segments of the fault simultaneously, which corresponds to a moment magnitude ofM_w7.1 ~ 7.5. The cumulative slip profiles suggest that the fault has likely propagated northward over its lifetime, and the south segment may be the most mature section of the fault where larger coseismic slip of earthquake ruptures may occur. The ratio of lateral to vertical displacement has remained constant (~3:1) through multiple successive events, indicating that the fault has maintained the same kinematic style over the last few thousands of years.

Strong earthquake activity along fault zones can lead to the displacement of geomorphic units such as gullies and terraces while preserving earthquake event data through changes in sedimentary records near faults. The quantitative analysis of these characteristics facilitates the reconstruction of significant earthquake activity history along the fault zone. Recent advancements in acquisition technology for high-precision and high-resolution topographic data have enabled more precise identification of displacements caused by fault activity, allowing for a quantitative assessment of the characteristics of strong earthquakes on faults. The 1920 Haiyuan earthquake, which occurred on the Haiyuan fault in the northeastern Tibetan Plateau, resulted in a surface rupture zone extending nearly 240 km. Although clear traces of surface rupture have been well preserved along the fault, debate regarding the maximum displacement is ongoing. In this study, we focused on two typical offset geomorphic sites along the middle segment of the Haiyuan fault that were previously identified as having experienced the maximum displacement during the Haiyuan earthquake. High-precision geomorphologic images of the two sites were obtained through unmanned aerial vehicle (UAV) surveys, which were combined with light detection and ranging (LiDAR) data along the fault zone. Our findings revealed that the maximum horizontal displacement of the Haiyuan earthquake at the Shikaguan site was approximately 5 m, whereas, at the Tangjiapo site, it was approximately 6 m. A cumulative offset probability distribution (COPD) analysis of high-density fault displacement measurements along the ruptures indicated that the smallest offset clusters on either side of the Ganyanchi Basin were 4.5 and 5.1 m long. This analysis further indicated that the average horizontal displacements of the Haiyuan earthquake were approximately 4–6 m. Further examination of multiple gullies and geomorphic unit displacements at the Shikatougou site, along with a detailed COPD analysis of dense displacement measurements within a specified range on both sides, demonstrated that the cumulative displacement within 30 m of this section of the Haiyuan fault exhibited at least five distinct displacement clusters. These dates may represent the results of five strong earthquake events in this fault segment over the past 10,000–13,000 years. The estimated magnitude, derived from the relationship between displacement and magnitude, ranged from M_w 7.4 to 7.6, with an uneven recurrence interval of approximately 2500–3200 years.

Fault scarps preserve important information about past earthquakes on a fault, and thus can be applied to investigate the fault slip histories and rupture patterns. In this study, the morphology of fault scarps was used to constrain the paleoseismicity of the Wulashan Piedmont Fault located on the northern margin of the Ordos Block based on high-resolution LiDAR topography. We constructed the vertical displacement distribution of the fault through measuring the heights of a large number of scarp profiles extracted on different geomorphic surfaces along the fault. Through statistical analysis of the dense collection of vertical displacement dataset, a total of seven paleoseismic events were identified which followed a characteristic slip pattern with an average slip of ∼1.0 m. We further detected slope breaks in the fault scarp morphology to quantify the number of paleoearthquakes that occurred on the scarps, and discriminated at least five individual surface-breaking events. Both the number and slip of paleoearthquakes recognized from the morphology of fault scarps were in good agreement with previous paleoseismic trenching records. Based on the empirical scaling relationship between moment magnitude and rupture parameters, a moment magnitude ofM_w6.7–7.5 was determined for the paleoearthquakes occurred on the fault. With the fault slip rate derived by previous studies, we estimated an average recurrence interval of 1.3–1.8 kyr for the paleoseismic events, which is very close to the elapsed time since the most recent earthquake, indicating a high potential seismic hazard on the Wulashan Piedmont Fault.

A study of tonalite−trondhjemite−granodiorite (TTG) suite and sanukitoids emplaced at different ages in the Archean can constrain the transition of early Earth’s tectonic regime, which remains a subject of debate. In this contribution, we report a systematic investigation of an early Neoarchean and late Neoarchean TTG-sanukitoid association from the eastern North China Craton based on mineralogical, petrological, and geochemical evidence. The geochemical features of the 2.7 Ga TTG rocks studied suggest that their magma was primarily generated by partial melting of garnet-amphibolite and eclogite. Moreover, they are characterized by relatively low values of MgO, Mg^#, Cr, and Ni, and zircon ɛ_Hf(t) that varies mostly with evolved signature, which suggests that the primary magma of the TTGs was generated in a setting of thickened lower crust. The 2.5 Ga high-K calc-alkaline granitoids studied show an affinity to Archean sanukitoids. Their representative major and trace elemental and isotopic features suggest that they were derived from partial melting of mantle wedge metasomatized by subducted fluids and slab- and sediment-derived melts, followed by varying degrees of mineral fractional crystallization. The eastern North China Craton may have developed a continental marginal arc system in the late Neoarchean attached to another craton in the global Kenorland supercontinent, which might have eventually resulted in its final cratonization. The distinct tectonic settings of the two types of granitoids may indicate a transition of the tectonic regime from vertical in the early Neoarchean to horizontal at the end of the late Neoarchean. Moreover, the low δ¹⁸O values found in this study as well as those in other areas of the globe suggest that they were probably related to cold climatic conditions and/or elevated latitudes or altitudes.