Himalayan Geology, Vol. 44 (2), 2023, pp. 15-24, Printed in India

Genesis of soft sediment deformation structures: An innovative experimental approach to

reproduce seismites under natural conditions

SOUMYADIP BANERJEE, SUBHAJIT SINHA*

Dept. of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata - 700019, India

*Email (Corresponding author): ssgeol@caluniv.ac.in

Abstract: Deformation in the sediment layers before consolidation is induced by a variety of processes. Many experimental studies have tried to replicate the generation of soft-sediment deformation structures under laboratory conditions, yet complete natural simulation is essentially excluded owing to the constraints of parameters in the experimental setup.

In the present study, a new experimental setup has been designed to reproduce soft-sediment deformation structures while keeping most of the natural parameters intact. The experiment was carried out in natural condition, on a sea beach, using a mechanical vibrator for generation of tremors. A satisfactory result was obtained with formation of prominent deformation structures like sagging and sand blasting, apart from various water escape structures. Conspicuously, tremors induced deformation into two separate layers of sediment with no sign of deformation in the sediment layer sandwiched between them. Another important observation was that the intensity of deformation in the same layer lessened with reduction in water content. The fluid in a sediment layer is thus postulated as a key factor for generating the soft-sediment deformation structures. Less water hinders deformation, and more water induces fluidization. This is a prototype experiment performed at its first stage; more sophisticated follow-up work is needed with state-of-the-art facilities.

Index term: Geosciences (primary index term), Sedimentary (tertiary index term)

Keywords: Soft-sediment deformation structures, beach, earthquake, vibration, water escape passage, experiment