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- Title
Reflection signature of seismic and aseismic slip on the northern Cascadia subduction interface.
- Authors
Nedimovic, Mladen R.; Hyndman, Roy D.; Ramachandran, Kumar; Spence, George D.
- Abstract
At the northern Cascadia margin, the Juan de Fuca plate is underthrusting North America at about 45 mm yr[SUP-1] (ref. 1), resulting in the potential for destructive great earthquakes[SUP2,3]. The downdip extent of coupling between the two plates is difficult to determine because the most recent such earthquake (thought to have been in 1700)[SUP4] occurred before instrumental recording. Thermal and deformation studies[SUP5] indicate that, off southern Vancouver Island, the interplate interface is presently fully locked for a distance of ∼60 km downdip from the deformation front. Great thrust earthquakes on this section of the interface (with magnitudes of up to 9)[SUP4,5] have been estimated to occur at an average interval of about 590 yr (ref. 3). Further downdip there is a transition from fully locked behaviour to aseismic sliding (where high temperatures allow ductile deformation), with the deep aseismic zone exhibiting slow-slip thrust events[SUP6]. Here we show that there is a change in the reflection character on seismic images from a thin sharp reflection where the subduction thrust is inferred to be locked, to a broad reflection band at greater depth where aseismic slip is thought to be occurring. This change in reflection character may provide a new technique to map the landward extent of rupture in great earthquakes and improve the characterization of seismic hazards in subduction zones.
- Subjects
BRITISH Columbia; CANADA; SUBDUCTION zones; SEISMIC reflection method; EARTHQUAKES; JUAN de Fuca Marine Trail (B.C.)
- Publication
Nature, 2003, Vol 424, Issue 6947, p416
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature01840