Hydroisostasy as a geodynamic phenomenon was discovered along investigation sea level changes of the World Ocean as result of intakes water to glaciers during Glacial period and releasing back during Interglacials. The water loads under sea level changes influenced the change of solid Earth shape and make the contribution to the vertical Earth crust movement along shorelines areas. A vertical shorelines movements are critical issue of the longtime living infrastructure coast facilities design with the overflooding and overdrainage forecast. The main method of hydroisostasy phenomenon investigation is remain the digital simulation. The global character of phenomenon require simulation involving all planet volume and detail accounting of the lithosphere and mantle layers features for each region which is forced to use 3-D modeling with high resolution and require big computing resources.Finite element method with ability to assign boundary conditions allow to use local-regions models with enough resolutions and take into accounts local lithosphere and mantle features without involving big computing resources.One of the free software packs with open code and possibility applying FEM for geodynamics simulations is — ELMER, software designed and supported by Finland CSC — IT CENTER FOR SCIENCE LTD.The trial applying of ELMER software packs for modeling hydroisostasy phenomenon for Earth interior conditions close to Deryugin depression in Okhotsk sea in this study has done. A plausible and encouraging result obtained for continuation of research in more detail.

Rustam F. Bulgakov, Candidate of Geographic Sciences, Researcher Laboratory of Coastal Geosystems Institute of Marine Geology and Geophysics FEB RAS. 1B, Nauka street, Yuzhno-Sakhalinsk, 693022, Russia. e-mail: r.bulgakov@imgg.ru

1. Bulgakov R.F., Senachin V.N. Marine terraces and hydroisostasy influence on the vertical movements of the Sakhalin. Geosystems of Transition Zones. 2019;3(3):277–286. DOI:10.30730/2541-8912.2019.3.3.277-286 [in Russian].
2. Rodnikov A.G., Sergeyeva N.A., Zabarinskaya L.P. The deep structure of the Deryugin basin (Sea of Okhotsk). Geology of the Pacific Ocean. 2002;21(4):3–8 [in Russian].
3. Clark J.A., Farrell W.E., Peltier W.R. Global Changes in Postglacial Sea Level: A Numerical Calculation. Quaternary Research. 1978;9(3):265–287. DOI: 10.1016/0033-5894(78)90033-9.
4. Getting Started with Abaqus/CAE. Dassault Systèmes, 2016. Available at: http://130.149.89.49:2080/v2016/books/gsa/default.htm (accessed 29.04.2021).
5. Mitrovica J.X., Peltier W.R. On post-glacial geoid subsidence over the equatorial oceans. Journal of Geophysical Research: Solid Earth. 1991;96(B12):20053–20071. DOI: 10.1029/91JB01284.
6. Peltier W.R. The Impulse Response of a Maxwell Earth. Reviews of Geophysics. 1974;12(4):649–669. DOI: 10.1029/RG012i004p00649.
7. Peltier W.R., Farrel W.E., Clark J.A. Glacial isostasy and relative sea-level: A global finite element model. Tectonophysics. 1978;50(2–3):81–110. DOI: 10.1016/0040-1951(78)90129-4.
8. Råback P., Malinen M., Ruokolainen J., Pursula A., Zwinger T. Elmer Models Manual. Espoo: CSC – IT Center for Science; 2019. – Available at: http://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerModelsManual.pdf (accessed 05.03.2020).
9. Spada G. The theory behind TABOO. Golden: Samizdat Press; 2003. 108 p. Available at: https://github.com/danielemelini/TABOO/blob/master/DOC/TABOO-theory.pdf (accessed: 05.03.2020).
10. Spada G., Antonioli A., Boschi L., Brandi V., Cianetti S., Galvani G., Giunchi C., Perniola B., Piana Agostinetti N., Piersanti A., Stocchi P. TABOO, User Guide. Golden: Samizdat Press; 2004. 120 p. Available at: https://github.com/danielemelini/TABOO/blob/master/DOC/TABOO_User_Guide.pdf (accessed 05.03.2020).
11. Spada G., Melini D., Galassi G., Colleoni F. Modeling sea level changes and geodetic variations by glacial isostasy: the improved SELEN code.  arXiv:1212.5061 [physics.geo-ph]. 2012. Available at: http://arxiv.org/abs/1212.5061 (accessed 22.04.2021).
12. Spada G., Stocchi P. SELEN: A Fortran 90 program for solving the “sea-level equation”. Computers & Geosciences. 2007;33(4):538–562. DOI:10.1016/j.cageo.2006.08.006.
13. Spada G., Stocchi P. The sea level equation, theory and numerical examples. Roma: Aracne; 2006. 96 p.
14. Zwinger T., Nield A.G., Ruokolainen J., King M.A. A new open-source viscoelastic solid earth deformation module implemented in Elmer (v8.4). GeoscientificModelDevelopment. 2020;13(3):1155–1164. DOI: 10.5194/gmd-13-1155-2020.