A small earthquake on the Armenia–Georgia border

On the afternoon of 1 November, at 14:41 local time, a small earthquake occurred at the Armenia–Georgia border, about 45 kilometres north of Gyumri. It was a weak event that most people would not have noticed, but six of our stations recorded it and located the epicentre just across the border, in the Ninotsminda municipality of Georgia.

The European-Mediterranean Seismological Centre (EMSC) placed the same earthquake about 5 km further south, inside Armenia, in the Ashotsk community of Shirak province. The difference is small for an event of this size, but here it decides on which side of the border the epicentre lies. Our solution relies on CHARNET stations only 35 to 52 km away: Saghik, Gyumri and Gyulagarak.

The record below follows the waves as they move away from the epicentre. At Saghik, 35 km away, the S-wave arrived 4.4 seconds after the P-wave; at Byurakan, 98 km away, the gap was 11.6 seconds; at Nerkin Jorja, 200 km away in the south, it had grown to 24 seconds. The longer the gap between the two waves, the farther the earthquake.