M 8.1 - east of the Kuril Islands

Tectonic Summary

The January 13, 2007, M 8.1 Kuril Islands earthquake occurred as the result of shallow normal faulting within the lithosphere of the Pacific plate. The epicenter of this event lies just east of the Kuril Trench, which marks the sea-floor expression of the plate boundary between the Pacific plate and the Okhotsk microplate (which is in turn part of the broader North America plate). Focal mechanism solutions indicate that rupture occurred on either an east-striking or southwest-striking, moderately dipping normal fault. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the southwest-striking fault. At the location of the earthquake, the Pacific plate moves northwest relative to the Okhotsk plate at a velocity of about 90 mm/yr, subducting at the Kuril Trench and becoming progressively deeper to the northwest, remaining seismically active to a depth of 680 km.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Normal-faulting events of the size of the January 13, 2007, earthquake are typically about 150x50 km (length x width); modeling of this earthquake implies similar dimensions, predominantly surrounding and down-dip of the hypocenter.

The location of the January 13th earthquake lies approximately 95 km east-southeast of a M 8.3 earthquake that occurred on November 15, 2006. Immediately following that 2006 event, aftershocks began occurring in the epicentral region of this subsequent January 13, 2007, earthquake, leading up to this rupture 2 months later. The November 15th earthquake is the largest event to have occurred in the central Kuril Islands since the early 20th century. The central Kuril Islands commonly experience one or more events of M 6+ in a decade. A central Kuril Islands earthquake in 1915 is estimated to have had a magnitude of about 8. To the southwest, the southern Kuril Islands chain experienced a M 8.5 earthquake in 1963. To the northeast, a M 9 earthquake occurred offshore of Kamchatka in 1952. No damage or casualties have been recorded in association with these earthquakes.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)