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Tsunami Arrival Detection with High Frequency (HF) Radar
Codar Ocean Sensors, 125 La Sandra Way, Portola Valley, CA 94028, USA
Codar Ocean Sensors, 5 Sunset Trail, Sunset Valley, TX 78745, USA
Codar Ocean Sensors, 1914 Plymouth St., Mountain View, CA 94043, USA
* Author to whom correspondence should be addressed.
Received: 13 April 2012; in revised form: 11 May 2012 / Accepted: 14 May 2012 / Published: 18 May 2012
Abstract: Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no system exists for local detection of an actual incoming wave with a significant warning capability. Networks of coastal high frequency (HF)-radars are now routinely observing surface currents in many countries. We report here on an empirical method for the detection of the initial arrival of a tsunami, and demonstrate its use with results from data measured by fourteen HF radar sites in Japan and USA following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. We compare arrival times at the radars with those measured by neighboring tide gauges. Arrival times measured by the radars preceded those at neighboring tide gauges by an average of 19 min (Japan) and 15 min (USA) The initial water-height increase due to the tsunami as measured by the tide gauges was moderate, ranging from 0.3 to 2 m. Thus it appears possible to detect even moderate tsunamis using this method. Larger tsunamis could obviously be detected further from the coast. We find that tsunami arrival within the radar coverage area can be announced 8 min (i.e., twice the radar spectral time resolution) after its first appearance. This can provide advance warning of the tsunami approach to the coastline locations.
Keywords: radar oceanography; remote sensing; current velocity measurement; tsunami detection
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MDPI and ACS Style
Lipa, B.; Isaacson, J.; Nyden, B.; Barrick, D. Tsunami Arrival Detection with High Frequency (HF) Radar. Remote Sens. 2012, 4, 1448-1461.
Lipa B, Isaacson J, Nyden B, Barrick D. Tsunami Arrival Detection with High Frequency (HF) Radar. Remote Sensing. 2012; 4(5):1448-1461.
Lipa, Belinda; Isaacson, James; Nyden, Bruce; Barrick, Donald. 2012. "Tsunami Arrival Detection with High Frequency (HF) Radar." Remote Sens. 4, no. 5: 1448-1461.