Sedimentary Records of Liquefaction: Implications From Field Studies

• Published in: Journal of geophysical research. Earth surface 2023-08, Vol.128 (8), p.n/a
• Main Authors: Świątek, Szymon, Belzyt, Szymon, Pisarska‐Jamroży, Małgorzata, Woronko, Barbara
• Format: Article
• Language: English
• Subjects: concave down structures; concave up structures; Deformation; Earthquakes; Grain size; Granulometry; Injection; injection and loading; Laboratory experimentation; Laboratory experiments; Liquefaction; liquefaction‐prone sediments; Quaternary; Samples; Sand; Sediment; Sediments; Seismic activity; Shear strength; Silt; Size distribution; soft‐sediment deformation structures; Statistical analysis; Statistical tests; Structures; textural features
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1029/2023JF007152

The susceptibility of grains in sediment to the liquefaction process causes the development of deformation structures. Some sediments undergo liquefaction, others do not. There is a group of sediments especially prone to liquefaction, which was proven during laboratory experiments. However, the field results are often slightly different from those obtained experimentally because of many unpredictable factors influencing the course of the liquefaction process. For this reason, we tested 144 samples of unconsolidated Quaternary‐age sediments, collected from eight study sites in Germany, Lithuania and Latvia, which have been liquefied. We also present some new dating results. These samples were divided into two groups of soft‐sediment deformation structures: concave up (e.g., injection structures) and concave down (e.g., load casts, pseudonodules). The granulometry of all deformation types was statistically evaluated, which allowed identifying textural differences between sediment contained in concave up and concave down structures. We suggest that the mobilization of silt fraction is responsible for the further deforming process. We also confirm that the maximum content of clay in sediment prone to liquefaction cannot exceed 14%, but only with a significant content of coarser fractions (silt and sand). Moreover, we identified two separate zones of the specific grain size in which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third “transitional zone” where all forms occur. The “transitional zone” is separated from the concave up structures and concave down structures zones by two “gap zones” in which no liquefied sediments were observed. Plain Language Summary Liquefaction is a process of temporary loss of shear strength of water‐saturated sediments, during which the solid‐state sediment behaves like a plastic mass or a viscous solid. It can be triggered in natural conditions by numerous factors, including waving, rapid sedimentation, earthquakes and the fall of meteorites. Sandy silt and silty sand are commonly known as the most liquefaction‐prone sediments, but the specific granulometric features are still insufficiently characterized. We analyzed 144 samples of unconsolidated Quaternary‐age sediments deposited in lacustrine, shallow marine and fluvial environments, which were liquefied. We divided all liquefaction‐induced soft‐sediment deformation structures into active and passive concave up (e.g