Tsunami Detection using Multi-frequency Beam-Forming HF Radar

We discuss a new multi-frequency beam-forming HF radar design for robust detection and tracking of tsunami waves from 200 km distances, providing continuous coverage of the tsunami approach to shore. The method works by mapping ocean currents at long range using traditional HF radar method of radial Bragg line Doppler shift measurement, then continuously looking for anomalous Doppler shift patterns and extremely high values due to the large orbital wave of the tsunami wave crest sequence. We discuss issues determining coverage quality improvement achievable using a multi frequency radar (MFR) in order to assure robust long range coverage. These issues include diurnal and seasonaly changes in noise character due to ionospheric conditions, and the effect of local wind speed and sea state providing a sufficiently good sea echo signal at long range. Multiple frequency utilization assures this higher quality at no design cost compared to existing single frequency HF radars, using the ISR digital radar design.