![Page 1: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/1.jpg)
Modeling typhoon- and earthquake-induced landslides in a
mountainous watershed using logistic regression
Kang-Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu
Geomorphology 89 (2007) 335–347
報告者 :蔡雨澄指導教授 :李錫堤報告日期 :2011/06/09
![Page 2: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/2.jpg)
Introduction
![Page 3: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/3.jpg)
• Landslides occur when unstable rock and soil masses
on slopes are disturbed by earthquakes, intense storms,
human activities such as road construction, or a
combination of these factors.
• Many researchers have used logistic regression to predict probabilities of landslide occurrence by analyzing the functional relationships between the instability factors and the past distribution of landslides.
![Page 4: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/4.jpg)
We used landslides triggered by a typhoon in 1996 and a major earthquake in 1999 to build a typhoon-induced model and an earthquake-induced model, respectively.
![Page 5: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/5.jpg)
Study area and Data
![Page 6: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/6.jpg)
Area:92km2
Elevation:770~2850m
Slope:0° ~77°
Hoshe basin
Topographic map (left) and oblique aerial photograph (bottom right) of the study area
![Page 7: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/7.jpg)
Geological map of the study area
Four Miocene lithologic formationsHoshe (Hs) FormationNanchuang (Nc) FormationKueichulin (Kcl) FormationT Terrace
Two sets of strike–slip faultsWNW NNE
Climate: subtropicalMean annual temperature:16°CMean annual precipitation:2300mm
![Page 8: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/8.jpg)
Chi-Chi earthquake 1999 /9/21, magnitude of 7.6
epicenter: about 60 km to the northwest of the study area
![Page 9: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/9.jpg)
![Page 10: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/10.jpg)
Wetness index: ln(a/tan β) a: contributing area tan β:slope
![Page 11: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/11.jpg)
Distribution of landslides triggered By typhoons and earthquake.
![Page 12: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/12.jpg)
Methods- logistic regression
![Page 13: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/13.jpg)
The logit model from a logistic regression has the following form:
y: dependent variable xi: the i-th explanatory variablea: constant a bi: the i-th regression coefficiente: error term.
The logit of y is the natural logarithm of the odds:
p: the probability of the occurrence of yp/(1−p): the odds
To convert logit(y) back to the probability p, it can be rewritten as:
![Page 14: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/14.jpg)
•The numbers of landslide cells for each event are as follows: Herb:783 Chi-Chi:4213 Toraji: 6294 Mindulle: 2161 Haitang:1146
•Random sample: 500 landslide cells and 500 stable cells for developing each model
•Ran logistic regression analysis in the Statistical Package of Social Sciences (SPSS)
![Page 15: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/15.jpg)
Results and Validation
![Page 16: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/16.jpg)
![Page 17: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/17.jpg)
Typhoon Earthquake
ROC 0.717 0.758
Area concordance 76.9 74.5
(Overlapped landslide area /Total landslide area on digital map)*100%
![Page 18: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/18.jpg)
![Page 19: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/19.jpg)
LL = (distance to channel)/(slope length)
distance to channel
slope length)
![Page 20: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/20.jpg)
![Page 21: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/21.jpg)
Conclusion
![Page 22: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/22.jpg)
Typhoon-triggered landslides tended to be near stream channels and earthquake-triggered landslides were more likely to be near ridge lines.
A major earthquake such as the Chi-Chi earthquake could still affect the spatial location of typhoon-triggered landslides 6 years after the event.
By covering both types of landslides in a natural experiment, this study takes a step closer to understanding one of the most destructive natural hazards.
![Page 23: Kang- Tsung Chang , Shou-Hao Chiang, Mei-Ling Hsu Geomorphology 89 (2007) 335–347](https://reader035.vdocuments.site/reader035/viewer/2022062723/56813e51550346895da83e88/html5/thumbnails/23.jpg)
Thank for your attention!