Abstract. We present new radar-based techniques for efficient identification of surface changes generated by lava and pyroclastic flows, and apply these to the 1996 eruption of Manam Volcano, Papua New Guinea. Polarimetric L-and P-band airborne synthetic aperture radar (SAR) data, along with a C-band DEM, were acquired over the volcano on 17 November 1996 during a major eruption sequence. The Lband data are analyzed for dominant scattering mechanisms on a per pixel basis using radar target decomposition techniques. A classification method is presented, and when applied to the L-band polarimetry, it readily distinguishes bare surfaces from forest cover over Manam volcano. In particular, the classification scheme identifies a post-1992 lava flow in NE Valley of Manam Island as a mainly bare surface and the underlying 1992 flow units as mainly vegetated surfaces. The Smithsonian's Global Volcanism Network reports allow us to speculate whether the bare surface is a flow dating from October or November in the early part of the late-1996 eruption sequence. This work shows that fully polarimetric SAR is sensitive to scattering mechanism changes caused by volcanic resurfacing processes such as lava and pyroclastic flows. By extension, this technique should also prove useful in mapping debris flows, ash deposits and volcanic landslides associated with major eruptions.
Many eruptions of Mt. Baekdusan volcano have been recorded in the historical literatures, and there were unrest precursors in 2002. Based on the geological survey results, it has been recognized that Mt. Baekdusan's Plinian eruptions had caused ashfall, followed by the occurrence of pyroclastic flows, which were caused by the collapse of eruption column. Therefore, we simulated the range of the impacts of pyroclastic flows, which were caused by small eruptions from a specific crater. Based on the simulation results, it can be interpreted that, when the pyroclastic flows are caused by the eruption column collapse from an eruption with less than VEI 3, the impacts will range from the outer rim of the caldera to the mountain slope 7 km at the maximum distance. Furthermore, it is interpreted that, when the eruption column occurs by the crater located inside the caldera, most will be deposited inside the caldera and what overflows will be deposited thickly mostly in the north valley, the upper stream region of Erdaobaihe.
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