THE ML 5.5, 5 FEBRUARY 2022 EARTHQUAKE NEAR THE OIL AND GAS FIELD ON THE SHELF OF NORTHEASTERN SAKHALIN ISLAND

Abstract

On 5 February, 2022 at 21:18 UTC (February 6 at 08:18 local time), an earthquake of local magnitude ML = 5.5 with a hypocenter in the upper crust occurred on the shelf of northeastern Sakhalin. The earthquake was caused by slip on the Piltun-Chaivinsky fault, which until recently was not considered a seismogenic source. The studied earthquake located in the area with Coulomb stress increment caused by the catastrophic 1995 Neftegorsk earthquake is most likely tectonic in origin. The accumulated tectonic stress associated with static stresses, triggered by the strongest earthquake in the northeast of the island, caused east-dipping reverse fault displacements. The focal mechanism of the earthquake is characterized by near-horizontal compression axes oriented sublatitudinally. The authors pioneered in collecting and analyzing instrumental data on strong ground motions near an earthquake, which are of value for engineering seismology. The macroseismic data incorporating the information received from local residents via the Internet were analyzed. Findings of the study are of practical relevance, since each year economic activities related to the subsoil development are expanding and intensifying. The present knowledge of active geological structures of the Sakhalin shelf contributes to the reassessment of seismic hazard in gas and oil producing areas.