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| Titel |
Landslide induced by the Typhoon Morakot in Shiaolin village, Taiwan |
| VerfasserIn |
Chingying Tsou, Masahiro Chigira, Zhengyi Feng |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034854
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| Zusammenfassung |
| Typhoon Morakot induced Shiaolin landslide, which killed 439 people in the south of Taiwan
on 9 August 2009 (National Disasters Prevention and Protection Commission, 2009). The
cumulative rainfall reached to 1676.5 mm in about 3 days, when the Shiaolin landslide
occurred. That was about one day after the peak of rainfall intensity. The landslide occurred
on a dip slope, which is underlain by late Miocene to early Pliocene sedimentary rocks
consisting of silt shale, massive mudstone, and sandstone. These beds, which trend NW-SE
and dip at 20-25Ë to SW, are located on the east limb of a syncline trending NNE-SSW and
plunging to SSW.
The landslide was 3 km long, 0.8 to 1.5 km wide, with an apparent friction angle of 14Ë .
It started as a slide upslope and transformed into debris avalanche downslope. The source
area was the upper third of the landslide and is divided into major southern part and the minor
northern part, which are separated by E-W trending joints. Interpretation of topography
before the landslide suggests that the source area showed hummocky surface, which is
indicative of the gravitational slope deformation before the event. In addition, water coming
out from the source area precipitated calcite on the stream bed, indicating that calcite
contained in the rocks is once dissolved by the groundwater. This dissolution should have
occurred also before the landslide and deteriorated the rocks, which are gravitationally
deformed.
The debris avalanche was a large bulk of mostly rock debris deriving from the southern
major part. The start time of the landslide was close to 06:16 AM and the end time of the
landslide was estimated to 06:17 AM with a velocity of 24.4 to 34.9 m/s, which is estimated
from the information of eyewitness and the seismic record of this landslide. The
seismic record is further processed and analyzed. The results indicate that the major
frequency content of the landslide vibration was near 0.9 Hz. The debris avalanche
crossed the flat terraces below the source area and pushed out or buried the village
below the terrace. It buried the narrow river channel with about 80 m width and then
ran up the opposite slope, making a 60 m high landslide dam, which breached at
07:00 AM, on 9 August (Shieh et al., 2009) and flooded the village area. The debris
consisted of fragments of mudstone, shale and sandstone, and interestingly they
had clayey materials at the bottom. These clayey materials had no swelling clay
minerals and is assumed to have played an important role for the transportation. |
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