Crisis hazard assessment for snow-related lahars from an unforeseen new vent eruption: the 2018 eruption of Kusatsu-Shirane volcano, Japan

Earth, Planets and Space

Table 1 Observed and estimated parameter values of tephra, snow, water, and time duration for lahar simulations

	Scenario A: rain-on-snow	Scenario B: snow-slurry lahar	Scenario C: snowmelt lahar
Fluid phase
Water input [m]	0.4	0.31	0
Water input by instantaneous snowmelt [m]	0.15	0	0.73
Solid phase
Snow [m]	0	0.58	0
Tephra [m]	1	0.5	1.5
Total volume [m³]	36,500	87,200	17,500
Solid volume fraction	0.65	0.78	0.67
Angle of repose [°]	33.6	36.3	33.6
Peak flow (Clay-rich flow) [m³/s]	76	150	42	Qp = 0.0188 V^0.790 (Pierson 1998)
Peak flow (Granular flow) [m³/s]	49	96	28	Qp = 0.0135 V^0.780 (Pierson 1998)
Time duration (Clay-rich flow) [s]	966	1160	828	2 V/Qp
Time duration (Granular flow) [s]	1494	1810	1271	2 V/Qp