Reference GNSS Stations for Warning on Possibility of Upcoming Earthquake in Zagreb

Distances between permanent GNSSS stations in positional systems are usually short between 30 km and 80 km. So calculated distances between the GNSS stations from their position coordinates calculated by processing collected GNSS data with Bernese software will be very well determined. The first time we determined that two days before earthquake in Kraljevo 2010 were shortening of sides between the GNSS referent stations, that this was a compression of the Earth’s crust two days before the earthquake. This effect was also confirmed on the Earthquakes Dreznica 2013, Skopje 2016 and Zagreb 2018 and that after compression two or several days after the earthquake occurs. However, they can also enable geophysicists to determine warn of possible earthquakes. On the end it was suggested that in the Control Center of CROPOS is required to establish a department for determination of compression in Earth crust based on GNSS measurement of the reference GNSS stations. This compression is possible to determine by "The method of daily changing the distance between GNSS permanent referent stations". After determination compression in Earth crust and using other geophysical methods will be probably possible to warn to upcoming earthquakes.