Seismites as Sedimentary Records of Geological Cataclysms

Abstract

Seismites are soft-sediment deformation structures (SSDS) formed in situ within unconsolidated sedimentary layers due to recurrent seismic shocks. Inserted in the domains of event stratigraphy and paleoseismology, these features record ancient cataclysmic events and regional tectonic dynamics. Passages of seismic body and surface waves elevate pore-fluid pressure, triggering liquefaction and fluidization mechanisms that temporarily reduce the sediment's shear strength. This work presents a comprehensive review of the fundamental concepts, diagnostic criteria, morphogenetic classifications, and field examples of seismites, as well as methods for measuring and correlating these structures with earthquake parameters. Diagnostic recognition requires strict criteria, including zonal stratigraphic confinement ("sandwiched" deformed layers), regional lateral continuity, and cyclical recurrence. Morphogenetic features—such as load casts, flame structures, ball-and-pillow, dish and pillar structures, clastic dikes, and convolute folds—are illustrated using classic field exposures from the Dead Sea Basin (Israel), Northern Kentucky (USA), and the Paris Basin (France). Quantitative assessment of seismites based on deformed layer thickness, structural geometry, and maximum liquefaction radius (𝑅𝑚𝑎𝑥) allows the estimation of local seismic intensity (𝑃𝐺𝐴) and back-calculation of minimum earthquake magnitudes (𝑀𝑤≥5.0−5.5). Ultimately, seismite analysis serves as an essential tool for mapping hidden seismogenic faults, reconstructing basin tectonic histories, and assessing recurrence intervals of catastrophic paleoseismic events.