High-resolution seismic studies of shallow lake Kandrykul (republic of Bashkortostan, Russia).

Seismoacoustic studies are used to solve a wide range of different tasks, such as studying the bottom of water bodies and bottom sediments, detecting sunken objects, designing various structures (pipelines, port facilities, etc.), estimating the thickness of sapropel deposits, calculating their reserves, etc. In terms of paleoclimatic studies, the importance of such studies is increasing. The study of sediments of continental water bodies allows to get preliminary information about climate changes in the region with a very high resolution. Seismoacoustic profiling allows remote characterization of lake sediments stratigraphy due to the recordings of acoustic waves reflected from the lake bottom and underlying layers. Seismoacoustic studies were conducted to detect bottom sediments and choose the best place for core sampling in Lake Kandrykul (Republic of Bashkortostan, Russia). 

Continuous seismic profiling was applied based on the principle of central beam, which enables remote investigation of the lake bottom structure owing to the recording of acoustic waves reflected from the lake bottom. On this basis, it is possible to establish borders between sediment layers of different physical properties. The seismoacoustic profiling was carried out using specialized complex, designed and manufactured on the base of Kazan Federal University. The complex includes: a source of elastic waves, a receiver, a seismic station, a laptop, a GPS-receiver, an inflatable boat, an electric motor, and power supply elements. The complex enables us to get seismic acoustic sections with vertical resolution at least 15 cm; depth study of various types of lake sediments at least 15 m; geodetic positioning system within several meters. It also provides the digital recording of information. As a source of elastic waves an inductive oscillator "boomer" was used. A storage battery was used as a source of electric power. The GPS receiver was used to coordinate profiles and boat location.

There were obtained 6 high resolution seismic sections. The total length of the profiles was more than 16 km. According to seismic data the depth of the lake is 15 meters. The thickness of bottom sediments is more than 7 m, which indicates the great age of the lake. Thus, the lake is suitable for studying climate changes in the past for this region. On the seismic section, it is clearly seen the moment of the lake formation, when the lake layered sediments began to accumulate.

This study was funded by the Russian Foundation for Basic Research under the grant #20-05-00833. Part of the study was funded with the subsidy allocated to the KFU in context of state assignment # 671-2020-0049.