A case of paleoseismic evidence of normal fault capable of triggering an M>8 earthquake − study on Sertengshan range-front fault, north margin of Hetao Basin, China
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Abstract
The Sertengshan Range-front Fault (SRF) and Langshan Range-front Fault (LRF) constitute a normal fault system on the northern boundary of the Linhe Depression in its northwest, and an investigation of the LRF–SRF is significant for understanding the seismic activities of normal faults. We set four trenches at three study sites to reveal paleo-earthquakes in the western segment of the SRF (W-SRF) in this system, and established 5 surface rupture events along W-SRF since the Late Pleistocene. By integrating paleoseismic data from 27 trenches on multiple fault segments, we reconstructed the paleoseismic sequence for the LRF–SRF region since 15 ka, and identified 10 paleoseismic events with corresponding rupture segments and magnitudes. The slip rates at the three study sites decreased gradually from the west to east on the W-SRF, by comparing with previous studies, further evidencing that the tectonic activities of the two faults have gradually synchronized. Besides, based on the timing of the latest paleoseismic event (1.88−2.03 ka BP), earthquakes of > M 8 surface ruptures of >200 km can occur in the northwestern Ordos Block and its seismic behavior revealed the seismogenic possibility of normal faults triggering an M > 8 earthquake.
雪腾山岭前断裂(SRF)和兰山岭前断裂(LRF)构成了临河凹陷西北部北缘的正断层系统,对兰山岭前断裂-SRF的研究对于了解正断层的地震活动具有重要意义。我们在三个研究地点设置了四条沟槽,揭示了该系统中SRF(W-SRF)西段的古地震,并确定了自晚更新世以来沿W-SRF的5次地表破裂事件。通过整合多个断层段上 27 个沟槽的古地震数据,我们重建了自 15 ka 以来 LRF-SRF 地区的古地震序列,并确定了 10 个古地震事件及其相应的断裂段和震级。与之前的研究相比,三个研究地点的滑动速率在西-南断裂带上由西向东逐渐减小,进一步证明两条断层的构造活动逐渐同步。此外,根据最近一次古地震事件(1.88-2.03 ka BP)发生的时间,鄂尔多斯地块西北部可能发生 M 8 级地表断裂 200 km,其地震行为揭示了正常断层引发 M 8 级地震的可能性。
期刊介绍:
The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.