 |
| Titel |
Characterising the Japan Trench subduction margin in the vicinity of the 2011 Tohoku earthquake using seismic reflection data |
| VerfasserIn |
Yu Ting Kwok, Rebecca Bell, Kimihiro Mochizuki |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250154456
|
| Publikation (Nr.) |
 EGU/EGU2017-19555.pdf |
|
|
|
|
|
| Zusammenfassung |
| Using a suite of 2D pre-stack time migrated seismic reflection profiles, collected between
2000 and 2014, we characterise the structure of the Japan Trench subduction margin in the
region of high, shallow slip in the 2011 Tohoku earthquake (between latitudes 37oN and
39oN). In order to convert our interpretations of margin structure from time to depth we have
developed a velocity model using published pre-stack depth migrated data and accompanying
velocity models, new ocean bottom seismometer velocity analysis and well log
data.
We observe that significant variations in margin characteristics exist from North to South
across the study area. To the north of 38.2oN the accretionary prism has a taper angle of >4o
and is c. 30 km wide and c. 3 km thick. Between 37.5oN and 38.2oN the taper angle
reduces (c. 3.5o) and the wedge is somewhat narrower and considerably thinner (c.
2 km). To the south we observe that the taper angle, wedge width and thickness
begin to increase up to similar magnitudes seen in the northern part of the study
area.
At 38.2oN three crossing seismic reflection profiles reveal that the décollement becomes
locally shallower by 1.5 km over a region measuring 20 km along-strike and 20 km down-dip.
The location of this local décollement upwarping also corresponds with a local indentation in
the deformation front by 2 km. These observations may be indicative of previously unknown
subducted relief, potentially a seamount or large horst block, in the zone of high, shallow
2011 Tohoku earthquake slip.
The region of localised wedge narrowing, thinning, décollement shallowing and wedge
taper reduction correlates with the location of maximum slip of > 50 m during the 2011
Tohoku earthquake. We therefore suggest a negative correlation between wedge thickness and
earthquake slip at this subduction margin. We speculate that the slip in this area may have
been enhanced, in part, due to reduced overburden stresses on the décollement. |
|
|
|
|
|
|