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The 9 June 94 Bolivian Deep Earthquake: An exceptional event in an extraordinary subduction zone
Author(s) -
Kirby Stephen H.,
Okal Emile A.,
Engdahl E. Robert
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl01802
Subject(s) - geology , subduction , seismology , slab , induced seismicity , transition zone , mantle (geology) , thickening , slab window , seismic moment , seismic tomography , geophysics , oceanic crust , tectonics , fault (geology) , chemistry , polymer science
We investigate the physical setting of the Bolivian shock based on the history of the subducting Nazca plate, intraslab seismicity, deep seismic moment release, and seismic tomography. South America has two broad regions of reverse arc curvature. Subduction constrained to this unique geometry produces slab kinking contortions that may cause unusual slab thickening as they sink to the bottom of the transition zone and encounter resistance to penetration into the lower mantle. Such contortions are observed at intermediate depths “upstream” from the slab source regions of both the great 1970 Colombian and 1994 Bolivian events. Thickening helps explain how the Nazca slab accommodates large seismic source dimensions at depths of 625–650 km.