**5. The 2020 Zagreb earthquake**

The Croatian geodesy journal *Geodetski list* [7] provides a brief overview of the earthquakes that occurred in Zagreb and its surroundings in the past, as well as of the latest earthquakes, which occurred on the 22nd of March 2022, and had magnitudes of 5.4 and 5.0, respectively. These earthquakes, which caused extensive damage to more than 25,000 buildings, occurred 140 years after the great earthquake that devastated Zagreb in 1880.

We chose four reference stations (**Figure 5**) from which GNSS satellite signals were received 24 hours a day. The signals were processed in the Geodetic Administration with the Bernise program package. With the help of these measurements, the daily changes in length were determined. We presented them graphically in **Figure 6**.

#### **Figure 5.**

*Crops reference stations for the analysis of daily distance changes before and after the earthquake the Zagreb earthquake on March 22, 2020.*

#### **Figure 6.**

*Daily changes in distances (the Zagreb earthquake on March 22, 2020) [7].*


#### **Table 1.**

*A list of earthquakes that have been analyzed.*

**Figure 6** shows that the Earth's crust was compressed on March 20th, 2020, which meant the earthquake would occur in 2 days. Since approximately half a day is spent on the calculation, this means that an earthquake could be announced one and a half days before.

A similar elongated quadrangle with diagonals was used in the analysis of the Kraljevo [4], Drežnica [5], and Zagreb [7] earthquakes (**Table 1**).
