The
Kuril-Kamchatka arc extends approximately 2,100 km from Hokkaido,
Japan, along the Kuril Islands and the Pacific coast of the Kamchatka
Peninsula to its intersection with the Aleutian arc near the Commander
Islands, Russia. It marks the region where the Pacific plate subducts
into the mantle beneath the Okhotsk microplate, part of the larger North
America plate. This subduction is responsible for the generation of the
Kuril Islands chain, active volcanoes located along the entire arc, and
the deep offshore Kuril-Kamchatka trench. Relative to a fixed North
America plate, the Pacific plate is moving towards the northwest at a
rate that increases from 75 mm/year near the northern end of the arc to
83 mm/year in the south.
Plate motion is predominantly convergent
along the Kuril-Kamchatka arc with obliquity increasing towards the
southern section of the arc. The subducting Pacific plate is relatively
old, particularly adjacent to Kamchatka where its age is greater than
100 Ma. Consequently, the Wadati-Benioff zone is well defined to depths
of approximately 650 km. The central section of the arc is comprised of
an oceanic island arc system, which differs from the continental arc
systems of the northern and southern sections. Oblique convergence in
the southern Kuril arc results in the partitioning of stresses into both
trench-normal thrust earthquakes and trench-parallel strike-slip
earthquakes, and the westward translation of the Kuril forearc. This
westward migration of the Kuril forearc currently results in collision
between the Kuril arc in the north and the Japan arc in the south,
resulting in the deformation and uplift of the Hidaka Mountains in
central Hokkaido.
The Kuril-Kamchatka arc is considered one of the
most seismically active regions in the world. Deformation of the
overriding North America plate generates shallow crustal earthquakes,
whereas slip at the subduction zone interface between the Pacific and
North America plates generates interplate earthquakes that extend from
near the base of the trench to depths of 40 to 60 km. At greater depths,
Kuril-Kamchatka arc earthquakes occur within the subducting Pacific
plate and can reach depths of approximately 650 km.
This region
has frequently experienced large (M>7) earthquakes over the past
century. Since 1900, seven great earthquakes (M8.3 or larger) have also
occurred along the arc, with mechanisms that include interplate thrust
faulting, and intraplate faulting. Damaging tsunamis followed several of
the large interplate megathrust earthquakes. These events include the
February 3, 1923 M8.4 Kamchatka, the November 6,1958 M8.4 Etorofu, and
the September 25, 2003 M8.3 Hokkaido earthquakes. A large M8.5
megathrust earthquake occurred on October 13, 1963 off the coast of
Urup, an island along the southern Kuril arc, which generated a large
tsunami in the Pacific Ocean and the Sea of Okhotsk, and caused run-up
wave heights of up to 4-5 m along the Kuril arc. The largest megathrust
earthquake to occur along the entire Kurile-Kamchatka arc in the 20th
century was the November 4, 1952 M9.0 event. This earthquake was
followed by a devastating tsunami with run-up wave heights as high as 12
m along the coast of Paramushir, a small island immediately south of
Kamchatka, causing significant damage to the city of Severo-Kurilsk.
On
October 4,1994, a large (M8.3) intraplate event occurred within the
subducted oceanic lithosphere off the coast of Shikotan Island causing
intense ground shaking, landslides, and a tsunami with run-up heights of
up to 10 m on the island.
The most recent megathrust earthquake
in the region was the November 15, 2006 M8.3 Kuril Island event, located
in the central section of the arc. Prior to this rupture, this part of
the subduction zone had been recognized as a seismic gap spanning from
the northeastern end of the 1963 rupture zone to the southwestern end of
the 1952 rupture. Two months after the 2006 event, a great (M8.1)
normal faulting earthquake occurred on January 13, 2007 in the adjacent
outer rise region of the Pacific plate. It has been suggested that the
2007 event may have been caused by the stresses generated from the 2006
earthquake.
More information on regional seismicity and tectonics
