Joint‐Rupture Pattern and Newly Generated Structure of Fault Intersections on the Northern Margin of the Linhe Basin, Northwestern Ordos Block, China.

The activity of major active faults around the Ordos Block is of great interest to seismologists, as at least four M ≥ 8 earthquakes have been recorded. However, the Linhe Basin, which has the thickest Cenozoic sediments, has no record of large earthquakes. Does this basin have the structural conditions required for large earthquakes? The northern boundary fault of the Linhe Basin is composed of the NE‐striking Langshan piedmont fault (LPF), E‐W‐striking western section of the Seertengshan piedmont fault (WSPF), and NW‐striking eastern section of the Seertengshan piedmont fault (ESPF). Based on large‐scale active fault mapping, this article analyzes data from 23 trenches, using an unmanned aerial vehicle to measure the faulted landform, and combines these data with Quaternary dating methods to acquire the paleoearthquake sequences of the LPF, WSPF, and ESPF. Furthermore, this article explores their rupture modes and discusses the structural evolution of two intersection points. Through paleoseismic comparison, seven trenches revealed historical earthquakes from 7 BC, with a common magnitude of M 8.1. The trenches also revealed seven paleoseismic events since the Holocene, which conformed to the periodic model with a period of 1.37 ± 0.11 ka. The elapsed time since the latest event (2.0 ka) has exceeded the earthquake recurrence period; thus, the area is currently at risk of an M 7.4–8.0 earthquake. The NE‐striking LPF and E‐W‐striking WSPF are connected by two left‐stepping small fault segments. The E‐W‐striking WSPF and NW‐striking ESPF are connected by a large triangular relay ramp. Key Points: Seven trenches revealed 7 BC historical earthquakes, with a calculated magnitude of M 8.1Since the elapsed time of the latest event (2.0 ka) has exceeded the recurrence period, the Linhe Basin is at risk of an M 7.4–8.0 earthquakeThe western section and the eastern section of the Seertengshan piedmont fault are connected by a large triangular relay ramp [ABSTRACT FROM AUTHOR]