Seismic Wave Arrival
10.0 s
P-wave Velocity: ~6.0 km/s
Flood Surge Arrival
3.7 hrs
13,333.3 s
Early Warning Window
3.7 hrs
222.1 min lead
Geological Rationale: Earthquakes or massive rockslides in steep Himalayan catchments emit high-frequency seismic P-waves (approx 6.0 km/s) and shear S-waves (approx 3.5 km/s). Meanwhile, hyperconcentrated debris flows and flash surges travel down tortuous canyons at 3.0 to 6.5 m/s. This velocity disparity creates a life-saving warning window of dozens of minutes to several hours before downstream flood crests reach settled communities.
Basin & Sensor Calibration
45 km
Distance from upstream landslide/epicenter to nearest broadband seismograph station.
60 km
Sinuous gorge channel length between the dam-break/landslide origin and downstream settlements.
4.5 m/s
Debris-laden flood front speed (typically 3.0 to 6.0 m/s in Melamchi/Indrawati channels).
M 4.2
Minimum ground shaking acceleration required to auto-trigger downstream evacuation alert sirens.
Calculated Timeline Sequence
T + 0.00 s:
Upstream Breach / Rock Avalanche Event
T + 7.50 s:
Seismic P-Wave triggers station & automated alert
T + 13,333.3 s:
Downstream river settlement peak surge arrival