Some supplements to the history of the trilateral cooperation

1. Improvementof interferometric hydrostatic tilt sensor and its application to monitor multiscale geodynamical processes with beyond nanoradian resolutionNKFIH-OTKA reg. numb.: 128527participants:Austria: Bruno Meurers (Univ. Wien), RomanLeonhardt (ZAMG)Finland: HannuRuotsalainen (FGI)Hungary: Judit Benedek (MTA), István Bondár (MTA), Lóránt Földváry (ÓE-MTA), János Kalmár (MTA), Gábor Papp (MTA), Marcell Szántó (ELTE)+ thetechnicalstaff of MTA CSFK GGI

2. Some supplements to the history of the trilateral cooperation mid ‘90s – firstmeetingswith Bruno and Hannu 2012 – 2017 - test of the gravity recording system of MTA CSFK GGI at the Conrad Obs. - moving mass calibrations in Mátyáshegy Gravity Observatory - calibration of LCR and Scintrex gravity meters on the Sopron Gravity Line 2014 – installation of iWT and LTS tilt sensors at the Conrad Obs. 2016 – beginning of stable operation of both tilt measuring instruments 2018 – common research project proposal submitted to NKFIH-OTKA

3. 2. Key questions, goals of the project 1) Can the sensitivity and the long term stability of the instrument be improved by the planned technical modifications? 2) What is the ultimate resolution of this interferometric technology in practice? 3) What are the environmental conditions which are necessary to utilize the increased sensitivity? 4) What kind of auxiliary (co-located, regional, global) data are needed to help the separation andinterpretation of gravitational and geometrical tilts generated by the mass (re)distribution of the Earth and the deformation of its physical surface, respectively? 5) What kind of modelling techniques have to be used to identify and separate “useful” and “disturbing” effects or alternatively local, regional and global influences in the integrated signal? 6) Is there any precursory signature of seismo-tectonic activity in the Mur-Mürz tectonic zone? 7) How the tilt observations can be combined with e.g. superconducting gravity measurements to support the investigation of the global geodynamics of the Earth (e.g. core resonances, free core nutation, etc...)? 8) Is there any method to compare the tilt (long term) tendencies to the change of the gravity potential of the Earth observed by GRACE follow on mission expected to launch in 2018?

4. The main goal of the application of the improved system is to link COBS and theSopronbánfalvaGeodynamical Obs. (SOPGO) for the coordinated local monitoring of tectonic events along both sides of the Mur-Mürz active tectonic zone. These stations could be the core of a regional network extending from the Mediterranean Sea to the Fennoscandian shield to investigate even the change of the flattening of the Earth caused by e.g. global mass redistribution of climate change origin.

5. 3.Expectedresults 1) A new construction of a biaxial, differential, interferometric hydrostatic (water tube) tilt sensor system providing sub-nanoradian resolution of the observed tilts. 2) Long running high resolution time series of tilt processes of different geodynamical origin recorded on the Alpine- and Pannonian sides of the Mur-Mürz tectonic fault system. Their analysis will help the interpretation of the seismo-tectonic activity of this zone and contribute to the research of precursory seismic events. 3) By the analysis of the recorded long term tendencies and its comparison to satellite based global models the feasibility of iWT to monitor and recover either regional or global changes of the gravity field and the shape of the Earth can be investigated. Based on positive results international project proposals to make a N-S transcontinental network of low-cost iWT stations can be formulated which would help the investigation of mass-redistribution related geodynamical processes generated by global environmental changes.

6. 4. Workplan First year (2018 – 2019) Mechanical and optical design of the improved interferometer unit. Its laboratory test either at the Geodetic and Geophysical Institute, Sopron or at the Finnish Geospatial Research Institute, Masala depending on where the circumstances (background noise, technical support, etc...) are better. Selection of new high speed CCD/CMOS cameras needed for imaging the Newtonian fringes at a high frame rate (50 Hz – 100 Hz). Modification of software components according to the specifications of the selected camera and its test with the experimental version of the interferometer. Second year (2019 – 2020) Production of 3 more interferometer units and the other necessary parts (end pots, tubes, mounting platforms, etc...) to make a biaxial, differential tilt sensor system. Installation of the system in the Conrad Observatory (COBS) and its test operation. Preparation of presentation(s) and paper(s) about the technical-methodological achievements and the experience of test operations for e.g. IUGG General Assembly and Journal of Geodynamics, Measurement Science Technology, respectively.

7. 4. Workplan (continued) Third year (2020 – 2021) Continuation of test observations parallel with the Lippmann type biaxial pendulum tilt sensor (LTS), the one-end iWT and the GWR SG025 superconducting gravimeter installed at COBS. Development and optimization of data storage and acquisition system. Improvement of the image processing algorithm with special attention to resolution issues. Correction of hidden hardware and software problems. Installation of the complete system in the Sopronbánfalva Geodynamical Observatory (SOPGO). Installation of a second LTS unit in SOPGO. Fourth year (2021 – 2022) Parallel recording by the instruments operated both in COBS and SOPGO located on the Alpine and Pannonian sides of the Mur-Mürz tectonic fault zone, respectively. Comparison of the results and multispectral analysis of data with special attention to secular tendencies, tidal harmonics and seismic events. Investigation of the methodological questions of the comparison of terrestrial observations and satellite based models of the Earth’s gravity field. Preparation of presentations and papers for IAG-IGETS meeting and Journal of Geodesy, Journal of Geodynamics, etc..., respectively.

8. 5. Participants

9. 6. Project budget 7700 EUR 3500 EUR 1200 EUR 4600 EUR 17000 EUR 3500 EUR 9000 EUR 20400 EUR 3000 EUR 33700 EUR

10. And a new unexpected possibilty: opening to the southern hemisphere Austria, Australia? What is thedifference? Just a fewletter… TPSO – Victor Harbor