The contribution presents two geophysical projects to investigate the Siberian part of the Arctic Ocean and adjacent continental margin First project bases on high-resolution multichannel seismic reflection lines collected in 1998, 2008 and 2014 in the Siberian part of the Arctic Ocean. The data provide an insight into the sedimentary cover and crustal surface of the Lomonosov Ridge and adjacent Laptev Sea in which in turn depositional and tectonic processes are documented. Part of the study was to develop a new seismostratigraphic model for the East Siberian part of the Arctic via the incorporation of drill site data to the seismic. Another aim is to propose suitable drilling locations for the upcoming IODP708 project (ACEXII) on the Lomonosov Ridge. Further we intend to tie in our data with seismic profiles of Russian colleagues to improve stratigraphic models and, thus to enhance our understanding of the tectonic development of East Siberian Sea and Margin. The second project comprises investigations of the seismicity and the lithospheric structure of the SW Lena Delta, which is part of the Laptev Sea Rift System. The distribution and kinematics of active fault zones might also help to better understand regional emissions of gases with deep origin at the surface and the seafloor. In 2016 we installed 12 seismological stations in the Lena delta to study the local seismicity along the southern part of the Olenek Fault Zone and 13 stations in an array SE of Tiksi to study the regional seismicity of the Laptev Sea. This work is carried out in a cooperation of various Russian and German institutions.