Plate data: Bird (2003), PB2002, converted by Hugo Ahlenius, Nordpil (ODC-By 1.0). Land: Natural Earth (India POV).
The Okhotsk Plate covers the Sea of Okhotsk, the Kamchatka Peninsula, Sakhalin, the Kuril Islands, Hokkaido and northern Honshu. On this map Sapporo and Tokyo both sit on it.1 Early 14-plate models such as NUVEL-1 placed this whole region on the North American Plate, as a slender arm reaching across the Bering Sea (Bird 2003).
Bird points out the problem with that arm: unless the forces on both sides balanced well, it would show strong faulting at its narrow neck, in the northern Sea of Okhotsk and northern Kamchatka. The name Okhotsk plate was possibly first used by Savostin and others in 1982 and 1983. Seno and others (1996) showed that a separate Okhotsk plate fits earthquake slip data significantly better, and estimated its motion relative to North America at 8 mm per year. Thrust earthquakes along the eastern coast of northern Kamchatka also show North America converging with a separate Okhotsk Plate.
How fast it moves is still uncertain. DeMets (1992) used 256 slip vectors from the highly seismic Kuril Trench and concluded that any motion between the Okhotsk and North American Plates is no faster than 5 mm per year. Bird considers the Seno rates in doubt because they neglect or underestimate the motion between the Eurasian and Amur Plates, so he adopts the pole position of Cook and others (1986) and, in his own words rather arbitrarily, assigns the boundary a rate of 3 mm per year.
Its longest boundary on this map is the convergent edge with the Pacific Plate at the Kuril Trench.2 Seno and others defined the plate as reaching south to central Honshu, so major earthquakes in the eastern Japan Sea occur on its western boundary, with the Eurasian or Amur Plate. On this map that western edge with the Amur Plate is convergent along its whole length.2
Okhotsk Plate in numbers
Measured from its PB2002 outline, the Okhotsk Plate covers about 3.0 million km², or 0.6% of the
Earth's surface. That makes it number 15 by area of the 52 plates in the model.
It spans from 34°N to 65°N and from 138°E to 171°E.
Its edge is about 9,460 km long, mostly convergent:
12.1%divergentDivergent boundary. Plates pull away from each other and new crust forms between them. Source (1,148 km)
, 70%convergentConvergent boundary. Plates move toward each other and crust is destroyed as one plate dives under another. Source (6,618 km)
and 17.9%transformTransform boundary. Plates slide horizontally past each other. Crust is neither made nor destroyed. Source (1,694 km)
.
Countries whose main landmass sits on this plate: Japan. Countries that straddle a boundary
are listed under the plate that holds the center of their largest landmass.
Along its boundaries it moves a mean 3.2 cm/yr relative to its neighbors, fastest against the Pacific Plate. Bird (2003)
Neighboring plates Neighbors. Plates that share a boundary with this plate. Most plate movement happens along these narrow zones between plates. Source
The Okhotsk Plate shares a boundary with 5 plates in PB2002, longest shared edge first.
The longest, about 3,016 km, is with the Pacific Plate; the shortest, about 313 km, is with the Philippine Sea Plate.
