 |
| Titel |
Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones |
| VerfasserIn |
P. E. Keken, S. Kita, J. Nakajima |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1869-9510
|
| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 2 ; Nr. 3, no. 2 (2012-11-07), S.355-364 |
| Datensatznummer |
250000993
|
| Publikation (Nr.) |
 copernicus.org/se-3-355-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| The cause of intermediate-depth (>40 km) seismicity in subduction zones
is not well understood. The viability of proposed mechanisms, which include
dehydration embrittlement, shear instabilities and the presence of fluids in
general, depends significantly on local conditions, including pressure,
temperature and composition. The well-instrumented and well-studied
subduction zone below Northern Japan (Tohoku and Hokkaido) provides an
excellent testing ground to study the conditions under which
intermediate-depth seismicity occurs. This study combines new finite element
models that predict the dynamics and thermal structure of the Japan
subduction system with a high-precision hypocenter data base. The upper plane
of seismicity is principally contained in the crustal portion of the
subducting slab and appears to thin and deepen within the crust at depths
>80 km. The disappearance of seismicity overlaps in most of the region
with the predicted phase change of blueschist to hydrous eclogite, which
forms a major dehydration front in the crust. The correlation between the thermally predicted blueschist-out boundary and the disappearance of
seismicity breaks down in the transition from the northern Japan to Kurile
arc below western Hokkaido. Adjusted models that take into account the
seismically imaged modified upper mantle structure in this region fail to
adequately recover the correlation that is seen below Tohoku and eastern
Hokkaido. We conclude that the thermal structure below Western Hokkaido is
significantly affected by time-dependent, 3-D dynamics of the slab. This
study generally supports the role of fluids in the generation of
intermediate-depth seismicity. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|