Meteotsunamis in the area of the Southern Kuril Islands: observations and numerical modeling

Meteotsunamis are frequent along the coasts of Sakhalin Island and the Kuril Islands, with one or two occurrences typically recorded each year. The most pronounced meteorologically induced long-wave oscillations observed in bays exhibiting strong resonant characteristics—features that are common throughout the Russian Far East. While meteotsunamis generally pose a moderate hazard, their impact can be significant for ports and vessels, although substantially lower compared to seismic tsunamis. The development of the network of tsunami detectors of the Russian Tsunami Warning Service in main ports of the Kuril Islands, as well as the establishment of autonomous bottom pressure recorders of the Institute of Marine Geology and Geophysics of Far Eastern Branch of Russian Academy of sciences in the coastal area of Southern Kuril Islands (mainly in the bays of Shikotan Island) made it possible to record several meteorologically-induced anomalous sea level oscillation similar to tsunamis during 2009‒2020. We examined in detail the event that occurred in the Southern Kuril Islands on October 16, 2011, recorded by six bottom pressure gauges, and accompanied by digital measurements of surface atmospheric pressure at three sites. Dangerous sea-level oscillations, with a maximum trough-to-crest height of approximately 75 cm in Malokurilskaya Bay, were generated by the passage of an atmospheric front characterized by a pressure drop of approximately 6 mbar and an eastward propagation speed of 100 km/h. A similar generation mechanism was responsible for the most significant meteorological tsunami recorded in the Russian Far East, which occurred on October 1, 2018. The trough-to-crest wave height reached approximately 2 meters along the ocean side of Shikotan Island, an amplitude comparable to that of a moderate seismic tsunami. Numerical simulations of long-wave generation induced by atmospheric disturbances demonstrate that a rapidly propagating atmospheric front along the Lesser Kuril Ridge can produce hazardous sea-level oscillations in the bays of Shikotan Island. This effect arises due to the near-resonant relationship between the front's propagation speed and the phase velocity of long ocean waves approaching the island from both its southeastern and northwestern sides. Two additional events are briefly described. The analysis demonstrates that meteotsunami impacts in the Southern Kuril Islands predominantly arise from Proudman resonance, closely matching the propagation speeds of atmospheric fronts and long ocean waves. Our high-resolution numerical modeling approach elucidates critical resonant mechanisms, directional dependencies, and highlights pronounced bay-specific responses, significantly enhancing regional hazard assessment capabilities.