Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhess-2016-285
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
16 Sep 2016
Review status
A revision of this discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Multiple remote sensing assessment of the catastrophic collapse in Langtang Valley induced by the 2015 Gorkha Earthquake
Hiroto Nagai1, Manabu Watanabe2, Naoya Tomii3, Takeo Tadono1, and Shinichi Suzuki1 1Earth Observation Research Center, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki, 305-8505, Japan
2School of Science and Engineering, Tokyo Denki University, Ishizaka, Hatoyama-machi, Hiki-gun, Saitama, 305-0394, Japan
3Satellite Applications and Operations Center, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki, 305-8505, Japan
Abstract. We demonstrated an assessment of the sediments caused by a catastrophic avalanche, induced by the main shock of the 2015 Gorkha Earthquake in Nepal. Calculation of decreasing coherence and visual interpretation of amplitude images by means of the Phased Array-type L-band Synthetic Aperture Radar-2 (PALSAR-2) have a high potential for delineating the hazardous zone. These delineated outlines area highly consistent with that from a high-resolution optical image of WorldView-3 (WV-3). The delineated sediment collapse areas were estimated as 0.63 km2 (PALSAR-2 coherence calculation), 0.73 km2 (PALSAR-2 visual interpretation), and 1.09 km2 (WV-3), respectively. In the WV-3 image, surface features were classified into 15 segments, with the flowing, scattering, and other characteristics implying different physical properties; the different features suggest sequential collapse from multiple sources. By means of satellite-derived pre- and post-event digital surface models, differences in the surface altitudes of the collapse events estimated the total volume of the sediments as 6229.1 x 103 m3, with an error possibility between 5363.3 x 103 to 7314.8 x 103 m3, most of which are distributed along the river bed and the water stream. Further altitude measurements after ice/snow melting would reveal a contained volume of melting ice and snow, which will contribute to numerical avalanche simulation and source considerations.

Citation: Nagai, H., Watanabe, M., Tomii, N., Tadono, T., and Suzuki, S.: Multiple remote sensing assessment of the catastrophic collapse in Langtang Valley induced by the 2015 Gorkha Earthquake, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-285, in review, 2016.
Hiroto Nagai et al.
Hiroto Nagai et al.
Hiroto Nagai et al.

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We demonstrated an assessment of the sediments caused by a catastrophic avalanche, induced by the main shock of the 2015 Gorkha Earthquake in Nepal. A Japanese space-borne sensor, PALSAR-2, have a high potential for delineating the hazardous zone. Comparison of pre-and-post high-resolution topographic data estimates the avalanche-induced sediment volume as 6299.1 x 103 m3. High-resolution satellite imagery revealed that it has multiple layers of sediment with different physical properties.
We demonstrated an assessment of the sediments caused by a catastrophic avalanche, induced by...
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