Deep-focus earthquakes: spatial patterns, possible causes and geodynamic consequences

• Published in: Geodynamics & Tectonophysics
• Main Authors: A. N. Didenko, M. I. Kuzmin, А. Н. Диденко, М. И. Кузьмин
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Institute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch 2018
• Subjects: рециклинг вещества; focal mechanism; transit zone of the upper mantle; phase transition; Japanese and Kuril-Kamchatka island arcs; morphology of slabs; substance recycling; фокальный механизм; транзитная зона верхней мантии; фазовый переход; Японская и Курило-Камчатская островные дуги; морфология слэбов; Kamchatka
• Online Access: https://www.gt-crust.ru/jour/article/view/632; https://doi.org/10.5800/GT-2018-9-3-0378

The spatial analysis was conducted to analyze the positions of earthquakes hypocenters in the transit zone of the upper mantle and the focal mechanisms of the strongest earthquakes in the subduction slabs of theOkhotskSeasegment of the Kuril-Kamchatka island arc and theJapanSeasegment of the Japanese island arc. It revealed a significant difference in the morphology of these slabs, as well as in the positions of the earthquake hypocenters relative to the active and stagnating parts of the slabs and the forces that caused the earthquakes. Based on the seismic data presented in the article, it is confirmed that there are two types of subduction of the oceanic lithospheric plates in the mantle. The article discusses relationships between the subduction and various geological processes at the upper–lower mantle boundary. It considers possible causes (including those related to phase transitions) of deep-focus earthquakes, in case of which splitting of the oceanic lithospheric plates takes place at depths near the upper–lower mantle boundary. Subduction of the oceanic lithospheric plates and their splitting predetermine a possibility for the crustal elements to penetrate into the lower mantle and deeper into the D″ layer, wherein new plumes arise and transport the deep magma together with the recycled substance into the crust. Deep-focus earthquakes are a necessary link in the mechanism providing for the recycling of chemical elements in the crust – mantle – D″ layer system and thus leading to the formation of a wide range of mineral deposits. Пространственный анализ положения гипоцентров землетрясений в транзитной зоне верхней мантии и фокальных механизмов сильнейших из них в субдукционных слэбах охотоморского сегмента Курило-Камчатской и япономорского сегмента Японской островной дуги показал существенное различие в морфологии этих слэбов, в положении гипоцентров землетрясений относительно активной и стагнирующей части слэбов и сил, вызывающих эти землетрясения. Приведенные в работе сейсмические данные ...