Disentangling factors controlling earthquake-triggered soft-sediment deformation in lakes

In-situ soft sediment deformation structures (SSDS) are commonly used as paleoseismic indicators in marine and lacustrine sedimentary records. Earthquake-related shear can deform the shallow subsurface through Kelvin-Helmholtz instability. The SSDS related to instability have been quantify shaking strength of past earthquakes. However, relative importance i) lithology physical properties, ii) potential basal surfaces (e.g. clastic deposits), iii) slope angle, iv) seismic peak ground acceleration) for remains poorly studied. Lake Riñihue (south-central Chile) is chosen a natural laboratory disentangling effect aforementioned factors because composition background varies downcore volcanogenic deposits abundant within sequence. A previous study at lake identified 25 intervals induced by historical earthquakes varying rupture extent 17 cores taken angles ranging from ~0.2° ~4.9° (i.e. 16 sites 1 basin site). Our shows that mostly occurs directly above 72 % intervals), suggesting promote earthquake-induced strain softening, liquefaction or water film formation. Deformation thickness increases with higher strong positive correlation). Additionally, corresponds stratigraphic depth youngest preceding deposit, but steeper stratigraphically older function surface. Therefore, we suggest primarily regulated gravitational stress angle) secondarily deposits. strongest caused almost exclusively highest degrees folds intraclast breccia) well largest spatial SSDS, resulting numbers investigated cores. Thinner given strength, seismically-induced energy acts more effectively on thinner deforming sequences. degree controlled modulated We infer not reliable indicator this relies many preconditioning independent strength. On other hand, be good proxy also settings lithotypes intercalated event deposits, provided multiple studied avoid under- overestimation