We investigated interactions between structural deformation and surface processes in the Longmen Shan fold‐and‐thrust belt and the adjacent western Sichuan foreland basin (WSFB) in the eastern margin of the Tibetan Plateau. The discrete‐element modeling (DEM) method was used to study the influences of the various mechanical properties of the detachments and syn‐tectonic erosion/deposition on the structural evolution of the Longmen Shan and WSFB. DEM simulations demonstrated two stages of surface processes during the Late Cenozoic profoundly influenced thrusting sequences and strain localization in the hinterland and foreland portions of the Longmen Shan. Models indicate that the fold‐and‐thrust belt lacking surface processes propagate in a forward‐breaking manner, whereas those with surface processes develop following an out‐of‐sequence thrusting pattern. We infer that large‐scale erosion propagation from the Sichuan Basin westward to the Tibetan Plateau since Late Cenozoic caused the Longmen Shan hinterland to reach a subcritical wedge state. Tectonic activity retreats to the edge of Plateau, enhancing the rapid uplift of the Longmen Shan and inhibiting the propagation of substantial shortening deformation to the foreland basin. The foreland thrust belt slides stably along the shallow detachment, causing the initiation and growth of the Longquan fault in the leading front. These results explain why both the Longmen Shan hinterland and the western Sichuan foreland thrust belts are currently in a state of simultaneous seismic activity. Our findings offer important implications regarding the seismic potentials of other fold‐and‐thrust belts that interact with dynamic surface processes.

Structural deformation affects surface processes and the consequent distribution of tectonic stress and structural deformation patterns via crustal isostasy. The associated processes and mechanisms are widely concerned topics in tectonic geomorphology. In this study, we discuss the interaction between tectonic deformation and surface processes in fold‐and‐thrust belts by sandbox experimental modeling. The tectonic deformation patterns under different conditions are studied, including the occurrence of detachment and the different crustal shortening rates. Furthermore, we discussed the influence of surface erosion and sedimentation on the spatial distribution, morphology, amplitude, and process of tectonic deformation. The results show that the occurrence of plastic detachment links the interaction of surface erosion and tectonics such as deformation patterns. Thin‐skinned structures develop when plastic detachment occurs, thus amplifying surface processes. In turn, the erosion and deposition affect the position and morphology of new structures as well as the lateral propagation and connection of isolated structures. Different shortening rates lead to different propagation distances and structure arrangements. These different tectonic conditions result in diverse drainage evolution and the specific processes of surface erosion and deposition. In general, structural development is controlled by both endogenic forces and surface erosion and deposition processes. The physical properties of detachments and crustal shortening rates play an important role in linking deep tectonic activity and surface processes. These results are comparable to natural examples, such as the fold‐and‐thrust belts along the Tianshan Mountains, thus providing new clues for understanding the mechanism of the interaction between endogenic tectonic activity and surface processes.

The 17 June 2018 $MJMA$ 6.1 (⁠$Mw$ 5.5) Osaka earthquake exhibits a large non–double‐couple component (⁠$∼26%$⁠), and its aftershock sequence shows a complicated spatial pattern. To better understand the ruptured faults, we relocate the earthquake sequence using P and S arrival times and waveform cross correlations and calculate the focal mechanisms of all $MJMA≥2.5$ (⁠$Mw≥2.3$⁠) earthquakes within three months after the mainshock using P‐wave first‐motion polarities and S/P amplitude ratios. Relocated aftershocks image several faults, the northeast‐striking strike‐slip fault, the north‐northwest‐striking reverse fault, and at least two small northwest‐striking features. P‐wave first motions of the mainshock indicate nearly a pure thrust mechanism. We deduce that the earthquake sequence started from a north‐northwest‐striking reverse fault and propagated to a northeast‐striking strike‐slip fault. The aligned strike‐slip aftershocks occurring in the vicinity of the northeast‐striking strike‐slip fault delineates the growth of several newly formed or reactivated northwest‐striking Riedel shears that are conjugated to the northeast‐striking strike‐slip fault.