Recent plate tectonics of the Arctic Basin and of northeastern Asia

Abstract

The recent tectonics of the Arctic Basin and northeastern Asia are considered as a result of interaction between three lithospheric plates: North-America, Eurasia and Spitsbergen. Seismic zones (coinciding in the Norway-Greenland basin with the Kolbeinsey, Mohns and Knipovich ridges, and in the Arctic Ocean with the Gakkel Ridge) clearly mark the boundaries between them. In southernmost Svalbard (Spitsbergen), the secondary seismic belt deviates from the major seismic zone. This belt continues into the seismic zone of the Franz Josef Land and then merges into the seismic zone of the Gakkel Ridge at 70°–90°E. The smaller Spitsbergen plate is located between the major seismic zone and its secondary branch. Within northeastern Asia, earthquake epicenters with magnitude over 4.5 are concentrated within a 300-km wide belt crossing the Eurasian continent over a distance of 3000 km from the Lena estuary to the Komandorskye Islands. A single seismic belt crosses the northern sections of the Verkhoyansky Ridge and runs along the Chersky Ridge to the Kolymo-Okhotsk Divide. To compute the poles of relative rotation of the Eurasian, North-American and Spitsbergen plates we use 23 new determinations of focal-mechanism solutions for earthquakes, and 38 azimuths of slip vectors obtained by matching of symmetric mountain pairs on both sides of the Knipovich and Gakkel ridges; we also use 14 azimuths of strike-slip faults within the Chersky Ridge determined by satellite images. The following parameters of plate displacement were obtained: Eurasia/North America: 62.2°N, 140.2°E (from the Knipovich Ridge section south of the triple junction); 61.9°N, 143.1°E (from fault strikes in the Chersky Ridge); 60.42°N, 141.56°C (from the Knipovich section and from fault strikes in the Chersky Ridge); 59.48°N, 140.83°E, α = 1.89 · 10 −7 deg/year (from the Knipovich section, from fault strikes in the Chersky Ridge and from the Gakkel Ridge section east of the triple junction). The rate was calculated by fitting the 2′ magnetic lineations within the Gakkel Ridge). North-America/Spitsbergen: 70.96°N, 121.18°E, α = −2.7 · 10 −7 deg/year from the Knipovich Ridge section north of the triple junction, from earthquakes in the Spitsbergen fracture zone and from the Gakkel Ridge section west of the triple junction). Eurasia/Spitsbergen: 70.7°N, 25.49°E, α = −0.99 · 10 −7 deg/year (from closure of vector triangles).