Damage Mapping of April 2015 Nepal Earthquake Using Small

J-Rapid Final Workshop 21 June, 2016, Kathmandu Inventory mapping of landslides induced by the Gorkha earthquake 2015 and a proposal for hazard mapping of future landslides for making a plan of better reconstruction "Impact on infrastructure by Gorkha earthquake 2015 induced landslides" Masahiro CHIGIRA Masahiro CHIGIRA Professor, Disaster Prevention Research Institute, Professor, Disaster Prevention Research Institute, Kyoto University Kyoto University Vishnu DANGOL Vishnu DANGOL Professor, Department of Geology, Professor, Department of Geology, Tribhuvan University Tribhuvan University Objective 1. to make an inventory mapping on landslides, cracks, and landslide dams induced by the Nepal earthquake and to investigate their formative mechanisms 2. to detect displaced areas of slope surfaces, of which future susceptibility to landslides would be evaluated on the basis of geology, geomorphology, and groundwater conditions. 3. propose a methodology of hazard mapping for earthquake-induced landslides in Nepal. Members (Japan side) 1. Masahiro CHIGIRA (Kyoto Univ.) PI Applied Geology 2. Daisuke HIGAKI (Hirosaki Univ.) Landslide control 3. Hiroshi YAGI (Yamagata Univ.) Landslide susceptibility mapping 4. Akihiko WAKAI (Gunma Univ.) Geotechnical analysis of landslide 5. Hiroshi, P. SATO (Nihon Univ.) Remote sensing 6. Go, SATO (Teikyo Heisei Univ.) Geomorpholoｇy 7. Ching-Ying, TSOU (Hirosaki Univ.) GIS analysis 8. Akiyo YATAGAI (Res. Inst. Humanity and Nature) Meteorology Members (Nepali side) 1. Vishnu DANGOL (Tribhuvan Univ.) PI Applied Geology 2. Smajwal BAJRACHARYA (ICIMOD) Remote sensing 3. Shanmukhesh Chandra AMATYA (DWIDP) Hydrogeology 4. Tuk Lal ADHIKARI (ITECO-Nepal) Geotechnical Field survey • Trishuli River catchment from Trishuli to Syabrubesi (29 October to 1 November, 2015) • Sun Kosi and Bhote Kosi River catchments from Bansaghu to Kodari. (2 to 4 November, 2015) • Budhi Gandaki River catchment from Arughat to Litin (6 and 7 March, 2016) • Dauradi River catchment from Jhulunge Bajar to Barpak (7 and 8 March, 2016) Inventory mapping of landslides Inventory Complied Topographic classification Knickpoint Data Used Note Data contributed by METI and NASA ASTER GDEM <ul style="display: flex;"><li style="flex:1">Slope break </li><li style="flex:1">AW3D DEM of JAXA </li></ul>AW3D DEM derived Constant Vertical Exaggeration Stereoscopic Map (CVES Map) Deep-seated landslide Deep-seated landslide Stereo-pair aerial photos CVES Map Complied by Dr. Go Sato Used for the area not covered by stereo-pair aerial photos Slope failure with scar <ul style="display: flex;"><li style="flex:1">The 2015 </li><li style="flex:1">newly formed scar </li></ul>Pre-earthquake: Google Earth Imagery (Dec. 12, 2014) Complied with the reference inventory of the Japan Landslide Society Earthquakeinduced slope failure enlargement of a preexisting scar Post-earthquake: Google Earth Imagery (May. 3, 2015) & LANDSAT 8 satellite imagery (June 1, 2015/covering the upstream Trishuli River) Pre-existing slope failure not enlarged by the earthquake Presented as points Geological setting of the affected area Higher Himalaya MCT Lesser Himalaya Kathmandu Mapped landslides 6,527 new landslides 558 enlarged landeslides 5,159 (ICIMOD-NELS) Cumulative landslide frequency and the landslide size Data added to Chigira et al. (2010, Geomorphology) What type of landslides occurred? Shallow disrupted landslides in most cases No gigantic landslides like those induced by the 2009 Wenchuan earthquake Bhote Koshi catchment Rockfall 400m fall from a slope break Dadakateri From a river terrace (Kodari) Cracks Mostly have not developed after the quake Cracks on a sharp ridge in Barpak Cracks on debris slopes (Bhote Koshi catchment) Large landslides, which had been continually moving were not reactivated. Dahlan landslide Mica schist Where did they occur? Inner valley Inner valleys (valley in valley) Inner valley Landslides Inner valley development Loosening of the valley wall <ul style="display: flex;"><li style="flex:1">Rapid River incision </li><li style="flex:1">River Incision </li></ul>Valley widening Loosened rock masses have been removed by the shaking Failure within a landslide body Trishuli River Steep infacing-slopes Slate, Bhote Koshi catchment Terrace scarps ghat Along a road Before the EQ Gneiss Landslides & Geology (Bhote Koshi catchment) Schist Malekhu Limestone Benighat Slate Roban phyllite Dhading Dolomite Fagfog Quartzite 4 km Pinkish phyllite Kuncha F. phyllite Number of landslides by each geological zone Occupancy ratio of landslides by each geological zone 500 400 300 200 100 0Landslides are dominating in areas of gneiss, slate, dolomite, quartzite Rare in areas of schist, phyllite Geology & Landslides Landslides and slope angles %Areal ratios of landslides Landslide numbers 100 90 80 70 60 50 40 30 20 10 0 250 200 150 100 50 0Subsequent rainfalls enlarged some landslide scars Large landslide bodies were not reactivated (Trishuli River) The 2015 Earthquakeinduced slope failure newly formed scar enlargement of a pre-existing scar Pre-existing slope failure not enlarged by the earthquake Deep-seated landslide InSAR image to detect small displacements on the order of cm Second (after the EQ) observation Crustal deformation First (before the EQ) observation In the case of LoS shortened, Blue -> Yellow -> Red: The ground was uplifted or close to the satellite 29 <a href="/goto?url=http://vldb.gsi.go.jp/sokuchi/sar/index-e.html" target="_blank">http://vldb.gsi.go.jp/sokuchi/sar/index-e.html </a>Comparing before and after the earethquake Mixture of noise and crustal displacement, But the red circle shows local surface displacement. Blue->Red->Yellow, away from the satellite In the red circle

Damage Mapping of April 2015 Nepal Earthquake Using Small

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