Seismic evidence for catastrophic slab loss beneath Kamchatka

• Published in: Nature (London) 2002-08, Vol.418 (6899), p.763-767
• Main Authors: LEVIN, Vadim, SHAPIRO, Nikolal, PARK, Jeffrey, RITZWELLER, Michael
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Earthquakes, seismology; Exact sciences and technology; Internal geophysics; Marine; Solid-earth geophysics, tectonophysics, gravimetry
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature00973

In the northwest Pacific Ocean, a sharp corner in the boundary between the Pacific plate and the North American plate joins a subduction zone running along the southern half of the Kamchatka peninsula with a region of transcurrent motion along the western Aleutian arc. Here we present images of the seismic structure beneath the Aleutian-Kamchatka junction and the surrounding region, indicating that: the subducting Pacific lithosphere terminates at the Aleutian-Kamchatka junction; no relict slab underlies the extinct northern Kamchatka volcanic arc; and the upper mantle beneath northern Kamchatka has unusually slow shear wavespeeds. From the tectonic and volcanic evolution of Kamchatka over the past 10 Myr (refs 3-5) we infer that at least two episodes of catastrophic slab loss have occurred. About 5 to 10 Myr ago, catastrophic slab loss shut down island-arc volcanic activity north of the Aleutian-Kamchatka junction. A later episode of slab loss, since about 2 Myr ago, seems to be related to the activity of the world's most productive island-arc volcano, Klyuchevskoy. Removal of lithospheric mantle is commonly discussed in the context of a continental collision, but our findings imply that episodes of slab detachment and loss are also important agents in the evolution of oceanic convergent margins.