Activation of the Sarychev Peak volcano in 2020–2021 (Matua Isl., the Central Kuril Islands)

This publication, based on remote sensing data, examines the features of the effusive eruption of the Sarychev Peak volcano (Matua Isl., the Central Kuril Islands), which took place from December 2020 till February 2021. On the basis of the analysis of the Sentinel satellite data, it was established that starting from December 2020, the crater of the Sarychev Peak volcano began to fill with lava. As of January 18, 2021, it was completely filled, then lava outpouring through a fissure in the north-northwest part began. A lava flow (length 2 km, width 80–90 m) descended along the bottom of the valley, which cuts the northwestern slope of the volcanic cone. The outpouring of lava was completed by February 7, 2021. The effusive eruption of the Sarychev Peak volcano in 2020–2021 is atypical for the modern stage of eruptive history, characterized mainly by explosive and explosive-effusive type of eruptions.

Shallow-water Ascidians from Matua Island (central Kuril Islands, NW Pacific), part 2

The paper reports several ascidians, previously not known from central group of Kurile Islands, including two new species, Synoicum polyzoinum n. sp. and Aplidium matua n. sp. In order to systematize our knowledge on numerous members of these genera, reported from NW Pacific, we provide an overview of all Synoicum and Aplidium species, known from Far Eastern Seas of Russia, including comments on the species erroneously identified in the past.

CO-SEISMIC GRAVITY GRADIENT CHANGES OF THE 2006–2007 GREAT EARTHQUAKES IN THE CENTRAL KURIL ISLANDS FROM GRACE OBSERVATIONS

GRACE satellites (the Gravity Recovery And climate Experiment) are very useful sensors to extract gravity anomalies after earthquakes. In this study, we reveal co-seismic signals of the two combined earthquakes, the 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands from GRACE observations. We compute monthly full gravitational gradient tensor in the local north-east-down frame for Kuril Islands earthquakes without spatial averaging and de-striping filters. Some of gravitational gradient components (e.g. ΔVxx, ΔVxz) enhance high frequency components of the earth gravity field and reveal more details in spatial and temporal domain. Therefore, co-seismic activity can be better illustrated. For the first time, we show that the positive-negative-positive co-seismic ΔVxx due to the Kuril Islands earthquakes ranges from − 0.13 to + 0.11 milli Eötvös, and ΔVxz shows a positive-negative-positive pattern ranges from − 0.16 to + 0.13 milli Eötvös, agree well with seismic model predictions.

Shallow-water Ascidians from Matua Island (central Kuril Islands, NW Pacific)

Fifteen species of ascidians were identified in the material collected at Matua Island. Two species are new, Botryllus flavus n. sp. and Distaplia matua n. sp. The first species occurs also at Kamchatka waters, while the second is probably an endemic of Kuril Islands. The genus Macrenteron Redikorzev, 1927 is synonymized with Aplidium Savigny, 1816 and a new name Aplidium macrenteron nom. nov. is proposed for its type species.