Dispersive tsunami of the 2010 Chile earthquake recorded by the high-sampling-rate ocean-bottom pressure gauges

Abstract

Cabled ocean-bottom pressure gauges deployed offshore Japan recorded the pressure change associated with the 2010 Chile earthquake tsunami over a wider frequency range than that of coastal tide gauges or hydrophones. Although it was difficult to recognize the dispersive features in the original records, the spectrograms clearly showed wave dispersion. A low-frequency tsunami (∼1 mHz) arrived after an elapsed time of 24 hr from the earthquake origin time, while a high-frequency tsunami (∼9 mHz) arrived after an elapsed time of 48 hr. The arrival times can be explained by assuming a constant water depth of 4 km. However, the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations. Cabled ocean-bottom pressure gauges deployed offshore can record broadband tsunami signals reflecting the wide-wavenumber-range spatial spectrum for sea-bottom deformation caused by the earthquake. © 2010 by the American Geophysical Union.