Interseismic strain accumulation of the 2022 Ms 6.8 Luding earthquake (Tibet) and discussion of the seismogenic mechanism

On September 5, 2022, a Ms 6.8 earthquake struck the Xianshuihe fault zone, a large-scale left-lateral strike-slip fault zone on the southeastern margin of the Tibetan Plateau, filling the Moxi seismic gap and resulting in significant economic losses and casualties. To clarify the seismogenic process and mechanism of this earthquake, we conducted a comprehensive and in-depth analysis on the stress–strain accumulation characteristics preceding the Ms 6.8 Luding earthquake based on the Global Positioning System (GPS) data and focal mechanism solutions. Our results reveal that the epicenter area of the Luding earthquake underwent long-term NWW-SEE directed compression and NEE-SWW directed tension, and gradually accumulates strain energy predominantly through shear deformation, with a sinistral shear strain rate of 3.4 × 10⁻⁸/a, which is associated with regional tectonic movement. Additionally, the focal area of the Luding earthquake exhibited a high accumulation of strain energy prior to the rupture, with a maximum locking depth of approximately 15.6 km. The Moxi section, where the Luding earthquake occurred, is likely approaching the late stage of its seismogenic cycle. The tectonic stress analysis further confirms that the mainshock of the Luding earthquake was primarily triggered by tectonic shear stress. These findings suggest that the Ms 6.8 Luding earthquake was a normal release of strain energy accumulated on a NW-striking strike-slip fault, mainly driven by the regional tectonic stress field resulting from the India-Eurasia plate convergence and the resistance from the rigid Sichuan Basin.