TSUNAMI EARLY DETECTION:ENHANCED RESOLUTION OF HF OCEANOGRAPHIC RADAR

[摘要] HF Oceanographic radar is an equipment, for instantaneously sensing velocity distribution of sea surface current. It has awide field of view, which extends approximately ±45° in direction and beyond 50km in distance. There are highexpectations that the radar observation of Tsunami will become a new road path for preventing disasters. In this paper, wedescribe a method to enhance the resolutions of radar in both time and current. At first, resolutions required for tsunamiobservation are estimated by simulating a Tokachi-oki earthquake tsunami (2003). Here it is pointed out that traditionaldata processing indicates inadequate resolutions for tsunami early detection. Secondly, two techniques are proposed toachieve the necessary resolutions. Short-time Fourier transform (STFT), in place of normal FFT, enhances the timeresolution of Doppler analysis. Further, zero-padding technique improves the current resolution, by interpolation of datawithin the frequency domain. Finally, by means of simulation, it is verified that these proposed techniques give improvedresolutions in both time and current.

[学科分类] 建筑学

[关键词] Tsunami;Surface flow;HF Radar;Sea echo;Doppler shift;FFT;STFT;Zero-padding;Peak detection