Problems of Engineering Seismology: article

Structural-lithological diagnostics of seismogenic convolutions in lacustrine complexes
E.S. Gorbatov
Schmidt Institute of Physics of the Earth, Russian Academy of Sciences
Journal: Problems of Engineering Seismology
Tome: 50
Number: 2
Year: 2023
Pages: 111-128
UDK: 550.394.4; 551.243.3; 551.312.48
DOI: 10.21455/VIS2023.2-5
Keywords: convolutions, seismites, seismic liquefaction, sediment tendency to liquefaction, density stratification of sediments, diagnostic features, lacustrine complexes, seismic hazard, stable and active regions, platforms and orogens
Аnnotation: In order to develop criteria for seismites, we compared 58 two-layer convolute folds in the Cenozoic lacustrine complexes of 11 regions of Eurasia and typified these structures according to the parameters “tendency to liquefaction” (light/heavy) and “density stratification” (unstable/stable) related to the dispersion of deformed sediments: type A – light, unstable (for example, sand on silt), B – light, stable (silt on sand), C – heavy, unstable (gravel on clay), D – heavy, stable (clay on gravel). In the considered series of convolution types, the sensitivity of sedimentary systems to dynamic impacts decreases, so type A structures can be formed almost spontaneously, D formed only as a result of a strong vibration load. It has been established that structures of types A, B, C are present in stable platform regions, in order of decreasing prevalence, and structures of types D, В, А, С are present in active orogenic regions, which corresponds to low and high levels of paleoseismicity in these regions. Thus, the presence of type D convolutions in sedimentary complexes (participation in the deformation of clays in the upper layer or gravel-pebble deposits in the lower layer) serves as a reliable criterion for a high level of seismic activity (M > 6.0) during their accumulation, and their absence with the predominance of type A – relatively low (M < 5.5). The revealed regularity can be used to assess the seismic hazard and analyze the trends of seismic regimes in the series of deformation events in sedimentary strata.