Lay, Thorne and Kanamori, Hiroo and Ammon, Charles J. and Hutko, Alexander R. and Furlong, Kevin and Rivera, Luis (2009) The 2006–2007 Kuril Islands great earthquake sequence. Journal of Geophysical Research B, 114 . Art. No. B11308 . ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20091216-091310767
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The southwestern half of a ∼500 km long seismic gap in the central Kuril Island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007. The nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate, trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries. The intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades (notably an M_S 7.2 event on 16 March 1963), leading to speculation that the interplate fault was seismically coupled. This issue was partly resolved by failure of the shallow portion of the interplate megathrust in an M_W = 8.3 thrust event on 15 November 2006. This event ruptured ∼250 km along the seismic gap, just northeast of the great 1963 Kuril Island (M_w = 8.5) earthquake rupture zone. Within minutes of the thrust event, intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture, with the larger events having normal-faulting mechanisms. An unusual double band of interplate and intraplate aftershocks developed. On 13 January 2007, an M_W = 8.1 extensional earthquake ruptured within the Pacific plate beneath the seaward edge of the Kuril trench. This event is the third largest normal-faulting earthquake seaward of a subduction zone on record, and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture. The 13 January 2007 event produced stronger shaking in Japan than the larger thrust event, as a consequence of higher short-period energy radiation from the source. The great event aftershock sequences were dominated by the expected faulting geometries; thrust faulting for the 2006 rupture zone, and normal faulting for the 2007 rupture zone. A large intraplate compressional event occurred on 15 January 2009 (M_w = 7.4) near 45 km depth, below the rupture zone of the 2007 event and in the vicinity of the 16 March 1963 compressional event. The fault geometry, rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations. The occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault. This great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events. Future seismic failure of the remainder of the seismic gap appears viable, with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention.
|Additional Information:||© 2009 American Geophysical Union. Received 30 December 2008; accepted 18 August 2009; published 24 November 2009. We thank the developers of GMT and SAC and the global and transportable seismic network operators who have constructed a superb open data access network for seismic research and monitoring. Ed Garnero and Christine Houser provided algorithms used for computing aspherical model travel time corrections for tomography models. We thank M. Raeesi and Y. Fujii for prepublication copies of their papers and Gavin Hayes, Daniel McNamara, and Phil Cummins for comments and discussions of the events. We thank Roland Bergmann and an anonymous reviewer for their helpful comments. The facilities of the IRIS Data Management System were used to access the data used in this study. Supported by NSF grants EAR0453884 and EAR0635570 (T.L.) and USGS Award 05HQGR0174 (C.J.A.).|
|Subject Keywords:||earthquake doublet; central Kuril seismic gap; outer rise faulting|
|Official Citation:||Lay, T., H. Kanamori, C. J. Ammon, A. R. Hutko, K. Furlong, and L. Rivera (2009), The 2006–2007 Kuril Islands great earthquake sequence, J. Geophys. Res., 114, B11308, doi:10.1029/2008JB006280.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||05 Jan 2010 18:55|
|Last Modified:||26 Dec 2012 11:39|
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