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Outline
Seismically triggered soft-sediment deformation structures (SSDSs) in the lacustrine sediments serve as reliable stratigraphic records for studying paleoearthquake events in tectonically active regions. Load and ball-and-pillow structures, as common types of SSDSs, are generally attributed to gravitational instability caused by an inverse density gradient between adjacent sedimentary layers. However, their formation mechanisms and the quantitative relationship between their development and seismic intensity remain poorly constrained.
This study employs the multiphase-flow numerical simulation approach implemented in ANSYS Fluent to simulate the formation of load and ball-and-pillow structures in saturated sand–clay layers under different peak ground accelerations (PGAs; 0.125g, 0.25g, 0.5g, and 0.8g) and varying physical properties, including density, dynamic viscosity and layer thicknesses). The effects of sediment physical properties on the development of these deformation structures and their relationship with seismic intensity were investigated.
The results show that as the PGA increases, load and flame structures develop earlier at the sand–clay interface and progressively evolve from small load structures into larger-scale load and ball-and-pillow structures. Under the same PGA, a larger density contrast, a smaller dynamic viscosity contrast, and a thicker overlying sand layer result in greater deformation and larger-scale development of load and ball-and-pillow structures.
The morphologies of the load and ball-and-pillow structures produced by the numerical simulations are highly consistent with those observed in lacustrine sediments in the Tashkorgan area. This agreement supports the proposed mechanical mechanism of their formation and provides a quantitative basis for understanding the development of SSDSs under different seismic and sedimentary conditions.
This finding verifies the seismic trigger of SSDSs in this region and provides a new technological insight into the study of SSDSs and paleoearthquakes.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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