Multiple remote sensing assessment of the catastrophic collapse in Langtang Valley induced by the 2015 Gorkha Earthquake

摘要: Abstract. The main shock of the 2015 Gorkha Earthquake in Nepal induced numerous avalanches, rockfalls, and landslides Himalayan mountain regions. A major village Langtang Valley was destroyed people were victims a catastrophic avalanche event, which consisted snow, ice, rock, blast wind. Understanding hazard process mainly depends on limited witness accounts, interviews, an situ survey after monsoon season. To record immediate situation to understand deposition process, we performed assessment by means satellite-based observations carried out no later than 2 weeks event. avalanche-induced sediment delineated with calculation decreasing coherence visual interpretation amplitude images acquired from Phased Array-type L-band Synthetic Aperture Radar-2 (PALSAR-2). These outline areas are highly consistent that high-resolution optical image WorldView-3 (WV-3). estimated as 0.63 km2 (PALSAR-2 calculation), 0.73 km2 (PALSAR-2 interpretation), 0.88 km2 (WV-3). In WV-3 image, surface features classified into 10 groups. Our analysis suggests event contained sequence of (1) a fast splashing body air blast, (2) a huge, flowing muddy mass, (3) less mass another source, (4) a smaller amount mass, and (5) splashing without east west sides. By satellite-derived pre- post-event digital models, differences altitudes collapse events total volume sediments 5.51 ± 0.09  ×  106 m3, largest distributed along river floor tributary water stream. findings contribute detailed numerical simulation sequences source identification; furthermore, altitude measurements ice snow melting would reveal snow.