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Data from: Frictional segmentation within a multi-detachment system: Implications for deep seismicity in the southern Sichuan basin, China

An, Mengke1; Huang, Rui2; Chen, Jianye3; Ma, Dongdong4; Zhong, Zhen5; Liu, Ziyu5; Xu, Zhengyu6; Derek, Elsworth7

Published Jun 05, 2026 on Dryad. https://doi.org/10.5061/dryad.0000000k6

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Jun 05, 2026 version files 2.31 MB

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Abstract

Induced seismicity in the southern Sichuan Basin exhibits a distinctive bimodal depth distribution, with a shallow cluster at 2–3 km associated with shale gas stimulation and a deeper cluster at 5–6 km broadly within Cambrian evaporite-bearing detachments. In such deeper depths (5–6 km), the mechanisms governing deeper earthquake clusters remain poorly constrained due to the limited likelihood of direct fluid migration. Here, we investigate the frictional behavior of evaporite-rich gouges composed of dolomite, gypsum, and halite mixtures in double-direct shear and then evaluate their potential role in controlling deeper fault stability within a multi-detachment system. The experimental results demonstrate systematic compositional controls on both fault strength and stability. Frictional strength varies nonlinearly with composition, with mixed dolomite–evaporite gouges exhibiting the highest strength at intermediate evaporite content. Pure dolomite gouges exhibit only stable sliding and velocity-strengthening behavior, compared to dynamic stick-slip instability in evaporite-bearing mixtures and enhanced velocity-weakening with increasing evaporites. The transition from velocity-strengthening to weakening behavior occurs at a critical evaporite content of ~40 vol.%. These mechanically heterogeneous assemblages therefore combine a capacity for rapid and high stress accumulation with frictional instability and thus yield conditions favorable for earthquake nucleation. In contrast, pure gypsum- and halite-rich gouges, although strongly velocity-weakening, are mechanically weak and less prone to accumulate elastic strain energy over geological timescales. These observations suggest that mechanically heterogeneous dolomite–evaporite intervals may be susceptible to unstable slip under transient stress perturbations and thus host deeper earthquakes within a multi-detachment system.