 |
| Titel |
Large-scale slope failure and active erosion occurring in the southwest Ryukyu fore-arc area |
| VerfasserIn |
T. Matsumoto, M. Kimura, M. Nakamura, T. Ono |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1561-8633
|
| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 1, no. 4 ; Nr. 1, no. 4, S.203-211 |
| Datensatznummer |
250000225
|
| Publikation (Nr.) |
 copernicus.org/nhess-1-203-2001.pdf |
|
|
|
|
|
| Zusammenfassung |
| The
southwestern Ryukyu area east of Taiwan Island is an arcuate boundary
between Philippine Sea Plate and Eurasian Plate. The topographic features
in the area are characterised by (1) a large-scale amphitheatre off
Ishigaki Island, just on the estimated epicentre of the tsunamigenic
earthquake in 1771, (2) lots of deep sea canyons located north of the
amphitheatre, (3) 15–20 km wide fore-arc basin, (4) 15–20 km wide flat
plane in the axial area of the trench, (5) E-W trending half grabens
located on the fore-arc area, etc., which were revealed by several recent
topographic survey expeditions. The diving survey by SHINKAI6500 in the
fore-arc area on a spur located 120 km south of Ishigaki Island was
carried out in 1992. The site is characterised dominantly by rough
topography consisting of a series of steep slopes and escarpments. A part
of the surface is eroded due to the weight of the sediment itself and
consequently the basement layer is exposed. The site was covered with
suspended particles during the diving, due to the present surface sliding
and erosion. The same site was resurveyed in 1997 by ROV KAIKO, which
confirmed the continuous slope failure taking place in the site. Another
example that was observed by KAIKO expedition in 1997 is a largescale mud
block on the southward dipping slope 80 km south of Ishigaki Island. This
is apparently derived from the shallower part of the steep slope on the
southern edge of the fan deposit south of Ishigaki Island. The topographic
features suggest N-S or NE-SW tensional stress over the whole study area.
In this sense, the relative motion between the two plates in this area is
oblique to the plate boundary. So, the seaward migration of the plate
boundary may occur due to the gravitational instability at the boundary of
the two different lithospheric structures. This is evidenced by a lack of
accretionary sediment on the fore-arc and the mechanism of a recent
earthquake which occurred on 3 May 1998 in the Philippine Sea Plate 250 km
SSE of Ishigaki Island. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|