Reflection signature of seismic and aseismic slip on the northern Cascadia subduction interface

LDEO Publication: 
Publication Type  Journal Article
Year of Publication  2003
Authors  Nedimovic, M. R.; Hyndman, R. D.; Ramachandran, K.; Spence, G. D.
Journal Title  Nature
Volume  424
Issue  6947
Pages  416-420
Journal Date  Jul 24
ISBN Number  0028-0836
Accession Number  ISI:000184318400040
LDEO Publication Number  6457
Key Words  southern vancouver-island; de-fuca plate; zone; earthquake; mantle; constraints; lithoprobe; records; margin; crust

At the northern Cascadia margin, the Juan de Fuca plate is underthrusting North America at about 45 mm yr(-1) (ref. 1), resulting in the potential for destructive great earthquakes(2,3). 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)(4) occurred before instrumental recording. Thermal and deformation studies 5 indicate that, off southern Vancouver Island, the interplate interface is presently fully locked for a distance of approximate to 60 km downdip from the deformation front. Great thrust earthquakes on this section of the interface (with magnitudes of up to 9)(4,5) 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(6). 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.


704BTTimes Cited:22Cited References Count:31

URL  <Go to ISI>://000184318400040
DOI  Doi 10.1038/Nature01840