Numerical analysis of Seismic and Hydrobiological data around lake Mavrovo in the period Jul.2020-Nov.2021

Two moderate earthquakes with magnitude ML5.0 happened on 11th of November 2020 near the Mavrovo lake in northwestern Macedonia. The lake is an artificial lake with a dam built between 1947 and filled by 1953. Its maximum length is 10km, width is 5km and the depth is 50m. Given its water volume, it is possible that geological factors causing earthquakes could also affect the hydrobiological characteristics of the flow system surrounding the lake.

A list of 180 earthquakes registered by the local stations with magnitudes equal or greater than ML1.7 was analysed in terms of temporal and spatial distribution around the lake. No specific clustering of events was noticed in the foreshock period from July 2020. In the aftershock period, the most numerous events lasted about a month after the main events. However, there was another period of increased seismicity during March 2021, followed by gradual decrease onwards. The distribution of epicentres was mainly along the terrain of Radika river and a few smaller tributaries to the lake system.

A comparative analysis was done with the dataset collected by the program run at the department of Biology at the Faculty of Natural Sciences, University UKIM in Skopje. Environmental investigations in Europe have shown stress reactions of hydrobionts in respect to water temperature and heavy metal pollution, for example the influence of radioactive radiation. Earthquake-induced seismic changes most often affect the chemical-physical properties of water quality and temperature stratification, i.e., mixing of water masses. In our research, we analyse for the first time the relationship between the seismological activities in the Jul 2020-Nov 2021 period in details and a possible impact to environment thru the population of macrozoobenthos from Mavrovo Lake.