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Objective The North China Plain (NCP) is one of the most populated and economically developed areas in China and is a region with a high level of seismic hazards. Studying the Quaternary activity of the faults and the seismogenic mechanism of the large earthquakes in NCP is conducive to exploring the seismogenic pattern of intraplate earthquakes and reducing the damage caused by seismic hazards. The Liaocheng-Lankao fault (LLF) is an important buried deep major fault in the south-central part of the NCP. The activity of the LLF and its relationship with the 1937 Heze M 7.0 earthquake is still highly controversial. Methods In this study, the activity of the Liaocheng-Liaokao fault is finely studied by combining shallow seismic exploration, drilling, and Quaternary dating methods. Results Shallow seismic reflection profile ZF-2 reveals that the strata below 145 m are obviously displaced, and the strata above 145 m are disturbed. The Bachengsi drilling profile reveals 16 sets of marker layers and three west-dipping normal faults Fa, Fb, and Fc; they form a "compound Y" structure in the profile, of which Fa displaces the bottom boundary of the Holocene (burial depth of approximately 38.9 m) and is an early Holocene active fault. It also reveals four paleoseismic events since the Late Pleistocene, with vertical displacement of 1.2±0.2 to 3.7±0.2 m for a single event. Based on the stratigraphic offsets in the boreholes, the average vertical slip rate of this fault is calculated to be about 0.1±0.05 mm/a for the early Late Pleistocene and 0.35±0.04 mm/a for the late Late Pleistocene-middle Holocene. The fitted age-depth curves by the test results of seven 14C samples and four OSL samples can be divided into two segments. Within the depth range of 0 to 86.0 m (approximately 21 to 0 ka), the age and depth of the strata conform to the formula y=(253.69±16.56)x+(924.72±681.36), from which the average deposition rate of this section is calculated to be 3.94±0.26 mm/a. Within the depth range of 102.9 to 145.4 m (approximately 128 to 59 ka), the age and depth of the strata conform to the formula y=(1470.67±259.91)x+(-95061.92±30190.73), from which the average deposition rate of this section is calculated to be 0.68±0.12 mm/a. The vertical slip rate of the LLF and the sedimentation rate of the Dongpu Sag have increased significantly since the late Late Pleistocene. The intensity lines of the Heze M 7.0 earthquake show an asymmetric butterfly shape. Conclusion The 1937 Heze M 7.0 and M 6\begin{document}${\raise0.7ex\hbox{$3$} \!\mathord{\left/{\vphantom {3 4}}\right.}\!\lower0.7ex\hbox{$4$}} $\end{document} earthquakes formed "Z" -shaped ground fissure zones, which can be divided into three sections: the southeastern section (section A), the middle section (section B), and the northwestern section (section C). The long axis of the intensity lines and the distribution of the surface rupture of the 1937 Heze M 7.0 coincide with the NNE-striking Xiaoliu-Xieyuanjie and NWW-striking Dongming-Chengwu faults in location and striking. The analysis of the intensity lines, surface rupture distribution, focal mechanism solution of the 1937 Heze M 7.0 earthquake and M 6\begin{document}${\raise0.7ex\hbox{$3$} \!\mathord{\left/{\vphantom {3 4}}\right.}\!\lower0.7ex\hbox{$4$}} $\end{document} earthquakes, and regional stress implies that the Xiaoliu-Xieyuanji fault and the Dongming-Chengwu fault are the seismogenic faults of the 1937 Heze M 7.0 earthquake. The LLF, as the deep major fault in the region, controlled the accumulation of stress, stimulated the earthquake with its deep movement, and reduced the effect of the seismic energy westward, acting as the regional seismic controlling fault of the 1937 Heze M 7.0 earthquake. Significance This article proposes a method for fine detection of the localization, structure, latest activity age, sliding rate, and paleoseismic sequences of the buried fault and also proposes a pattern of seismicity in which seismogenic faults do not coincide with the regional seismic controlling fault. It provides new insights into the characterization of seismicity within the NCP and can provide the geological basis for urban and rural planning, high-speed railway design, and earthquake prevention and disaster reduction project construction in this region.

The Sichuan-Yunnan block is a tectonically active region in China, with frequent large earthquakes occurring in and around it. Despite most earthquakes being concentrated along boundary faults, intraplate faults also have the potential to generate damaging earthquakes. Remote sensing makes it possible to identify these potential earthquake source faults. During an active fault investigation in the Liangshan area, a distinct lithological boundary named Caimashui fault was found. The geometric distribution and kinematic parameter of the fault is crucial for assessing seismic hazards and understanding the deformation pattern within the Sichuan-Yunnan block. The Caimashui fault is mapped with remote sensing interpretation, a field survey, and UAV measurement. Through trenching and Quaternary dating, the Late Quaternary active characteristics of the fault are studied. The fault is a Holocene active dextral strike-slip fault with a reverse component, exhibiting a dextral strike-slip rate of ~0.70 ± 0.11 mm/a. Paleoseismic investigation shows that the last surface rupture event of the Caimashui fault occurred later than 4150 ± 30a BP, with a magnitude of M ≥ 7.0. The fault may act as a secondary splitting fault, absorbing the deformation caused by various sinistral strike-slip rates of the boundary faults and the potential energy from the counterclockwise rotation of the Central Yunnan micro-block. [ABSTRACT FROM AUTHOR]

Long paleoearthquake series are crucial for understanding the recurrence patterns of active faults and evaluating the seismic hazards of faults. In this study, the first semiquantitative evaluation of paleoearthquake events from trenches was applied to normal faults, and classification criteria for identifying paleoearthquakes in trenches on normal faults are proposed to demonstrate the feasibility of semiquantitative evaluations of paleoearthquake events on normal faults. In this study, 72 paleoearthquake trench sites on normal faults around the world were analyzed, and the main indicators for identifying paleoearthquakes on normal faults include the presence of vertical offset (VO), collapse wedge (CW), fissure (FIS), buried paleosol (BP), angular unconformity (AU), upward termination (UT), and sand liquefaction (LF) features. To describe and apply this semiquantitative evaluation method for paleoearthquake events on normal faults, 33 trenches for paleoearthquakes on a fault system in the northern margin of the Hetao Basin were comprehensively analyzed to determine Holocene paleoearthquake events on the Sertengshan, Wulashan, and Daqingshan piedmont faults, and the reliability of paleoearthquake events is discussed. The integrity of the paleoearthquake events obtained was tested by the displacement limit method. The Holocene paleoearthquake recurrence on the three faults was quasiperiodic; the coefficients of variation (COVs) were 0.44, 0.58, and 0.4. Plain Language Summary: In this study, 72 paleoearthquake trench sites on normal faults around the world are analyzed, and summarized the main indicators for identifying paleoearthquakes on normal faults. Classification criteria for identifying paleoearthquakes in trenches on normal faults are proposed. Using the faults of the northern margin of the Hetao Basin as an example, this study described a semiquantitative evaluation method for normal fault paleoearthquake events, and discussed the reliability of paleoearthquake events. The integrity of the paleoearthquake events obtained was tested by the displacement limit method. Combining with studies on the reliability and integrity of paleoearthquake events, we argue that it is feasible to apply semiquantitative evaluations of paleoearthquake events from trenches to paleoearthquake research on normal faults. Key Points: Semiquantitative evaluation of paleoearthquake identification from trenches to normal faults is applied for the first timeClassification criteria are proposed for identifying paleoearthquakes in trenches on normal faultsThis study demonstrates the feasibility of semiquantitative evaluation of paleoearthquake events on normal faults [ABSTRACT FROM AUTHOR]