Title of the article: Określenie sejsmicznej struktury płaszcza Ziemi na podstawie rejestracji grawimetrów pływowych

The Project is funded by the National Science Centre, Poland (NCN) via the OPUS 14 research project No. 2017/27/B/ST10/01600.

Duration of the project: 18.06.2018 – 17.06.2021

Financing amount: 513 010,00 zł

Project team:

Principal investigator: dr hab. Monika Wilde-Piórko, email: monika.wilde-piorko@igik.edu.pl

Co-investigator: dr inż. Przemysław Dykowski, mgr inż. Kamila Karkowska, dr Marcin Polkowski, dr Marcin Sękowski

The aim of the project is to determine the seismic structure of the Earth's mantle from the analysis of surface waves generated by earthquakes and recorded by gravimeters used commonly to study the tides of the Earth. Surface waves penetrate the Earth’s interior, more deeper than longer their periods are. Therefore, the speed of the wave propagating along the surface of the Earth depends on its period and the structure of the Earth's interior. The analysis of the signal recorded by instruments allows to determine the dispersion curves of surface waves, from which by inversion methods, the velocity distributions of seismic waves with depth can be estimated for better recognition of the structure of the Earth's interior.

Modern tidal gravimeters record relative global and local changes in gravity without distortions for frequencies lower than 1 mHz. Typical broadband seismometers record the velocities of displacement of the Earth's surface without distortions in the frequency range from 8.3 mHz to 50 Hz. Records of surface waves, with frequencies from 1 to 6 mHz penetrating the Earth's mantle up to a depth of 1000 km, are very distorted by seismometers and very little by gravimeters. In particular, the analysis of superconducting gravimeters, characterized by sensitivity in the frequency domain at the order of nGal (10-11 m/s2), gives a unique opportunity to study long-period surface wave, what previously was unattainable in seismic surveys.

The models of the Earth's mantle obtained as a result of the project will be unique because they will be developed on the basis of records from which the absolute values of the velocity of seismic waves in the Earth's mantle can be calculated. The models of the Earth's mantle obtained from the tomography of first onsets of body waves provide relative information about the velocity distributions. Thus the information about the percent deviations of the velocity values from the applied reference model can be obtained. The research methodology developed in the project could be applied to the surface wave records of any tidal gravimeter, providing that adequate sampling frequency of records (minimum 1 Hz) will be available. The obtained mantle models will allow verification of already existing models, obtained on the basis of other seismic data and methods.