Recent geodynamic regime of the Eurasia – North American interplate boundary: Evidences from seismology of Arctic
نویسندگان
چکیده
The paper considers seismological evidences on a geodynamic regime in the Arctic segment of the interplate boundary between Eurasian and North American lithosphere plates. A scope of earthquakes occurred in the Mon, Knipovich and Gakkel mid-ocean ridge belts (MORB) has been made, and distribution of doublecouple (DC) and non-double-couple (NDC) sources has been evaluated. As revealed, the DC events, caused by shearing tectonic movements, prevail among earthquakes in all MORBs. In the Arctic MORBs with ultra low speed of spreading the NDC earthquakes, caused by normal rifting or volcanic eruptions, are responsible for 9 % seismic energy release only, whereas in the Mon Ridge (North Atlantic spreading belt with the average speed of extension about 3 cm per annum) their contribution is 5 times higher. Thus, the seismological data give evidences that the Arctic segment of the interplate boundary between Eurasian and North American lithosphere plates belongs recently to the transform geodynamic type, and only in the North Atlantics (within the Mon Ridge) a divergent type is still alive. Аннотация. Выполнен анализ тензоров сейсмических моментов землетрясений, зарегистрированных в ХХ веке в Арктическом сегменте пограничной области, разделяющей Евразийскую (ЕА) и СевероАмериканскую (СА) литосферные плиты. Показано, что сейсмически активные зоны сосредоточены в срединно-океанических хребтах (СОХ) Мона, Книповича и Гаккеля. Источники сейсмической эмиссии представлены двумя типами: DC (сдвиговых тектонических движения) и NDC с доминированием растяжения (раздвиги, области сферического расширения над вулканическими очагами). В Арктических хребтах Гаккеля и Книповича, характеризующихся средней скоростью спрединга 0,5-2 см в год, на долю землетрясений типа NDC приходится всего 9 % энергетической разрядки, тогда как в СОХ Северной Атлантики, имеющих скорость расширения около 3 см в год, их вклад в пять раз выше. Это различие может свидетельствовать о том, что Арктический сегмент области сочленения ЕА и СА плит в настоящее время находится в режиме трансформной границы, обеспечивающей вращение ЕА плиты против часовой стрелки, а дивергентный режим межплитного раздела сохраняется лишь в хребте Мона.
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