Changes of gross gamma-ray intensity in a submarine spring system due to a distant earthquake event on 30th of March 2019 at Itea, Greece

A medium resolution underwater in-situ gamma-ray spectrometer (GeoMAREA) was deployed in the submarine spring (Kiveri) for continuous monitoring of the gross gamma-ray intensity enriched in groundwater. The gross gamma-ray intensity was elaborated for earthquake study using the Rayleigh Probability Distribution Function. Gross γ-ray intensity had increased gradually since 10 days before the earthquake (Itea, 30/3/2019), in which the Rayleigh probability distribution gave weak and strong anomalies 52 h 20 min and 7 h 20 min before the earthquake, respectively. The anomaly of gross gamma-ray intensity was observed for short period of time which was returned to pre-earthquake values after the earthquake.