Abstract
Sea-level variation can be induced by periodic tides, stochastic wind, air pressure, and swell. Larger sea-level variation has the potential to cause coastal disasters. In this paper, real-time continuous data obtained by the Xiaoqushan seafloor observatory in the East China Sea were analyzed employing frequency power spectral and tidal harmonic methods to extract the major components and periodicities of sea-level change. The sea-level anomaly (sla) was calculated by subtracting the tidal components from the observed sea level data. In the study period, the correlation between sla and the local north-south wind speed was high with a correlation coefficient of 0.65 at the 95% confidence level. The local wind-induced sea-level anomaly (slawind) was therefore computed through linear fitting. Although slawind is one of the main components of sla, the residual sea-level anomaly (slaresidual) obtained by subtracting slawind from sla is not zero, suggesting that there are other factors besides wind. Detailed analysis of the sea-level data at the time of the 8.8-magnitude Chilean earthquake on February 27, 2010 showed a peak slaresidual value of 0.48 m at around 15:00 on February 28, which was highly coincident with the tsunami arrival time forecast by the Pacific Tsunami Warning Center. The peak slaresidual event is therefore linked with the tsunami induced by the 2010 Chilean earthquake. This is the first time that a tsunami has been detected using real-time continuous data recorded by a seafloor observatory in the sea off China. Such observations are expected to improve tsunami forecast models and promote the development of a tsunami warning system and a seafloor observatory network in the East China Sea.
Highlights
Background of the Xiaoqushan seafloor observatory2.1 Background dataFigure 2 presents the wind speed, sea-water temperature and sea level from April 2009 to August 2010
We focus on the record of the tsunami induced by the Chilean earthquake that occurred on February 27, 2010 [3] to detect the maximum sea-level variations and provide a theoretical basis for the construction a future seafloor observatory and tsunami warning system [11]
Besides the data obtained by the acoustic Doppler current profiler (ADCP) and CTD detector, sea-surface data and weather measurements were collected from the Xiaoqushan weather station several hundred meters from the Xiaoqushan seafloor observatory
Summary
The experimental station of the East China Sea seafloor observatory was deployed near Xiaoqushan Island at the mouth of Hangzhou Bay (30.5 N, 122.2 E, Figure 1). The Xiaoqushan seafloor observatory came into operation on April 20, 2009. The Xiaoqushan seafloor observatory has been equipped with one 1200 kHz acoustic Doppler current profiler (ADCP) and one conductivitytemperature-depth (CTD) detector, which were deployed about 0.8 m above the seafloor. The CTD detector was set to measure the sea-water temperature, salinity and turbidity near the seafloor every 1 min. Besides the data obtained by the ADCP and CTD detector, sea-surface data and weather measurements were collected from the Xiaoqushan weather station several hundred meters from the Xiaoqushan seafloor observatory. Wind and air temperature were measured by an anemometer and thermometer installed 60 m above the ground at the weather station
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