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Contribution of seismic oscillations to ocean-bottom pressure records at the 2011 Tohoku earthquakeтезисы доклада
- Авторы: Matsumoto H., Nosov M., Kolesov S., Inoue S., Kaneda Y.
- Сборник: 26th International Tsunami Symposium, Gocek/Turkey and Rhodes/Greece
- Тезисы
- Год издания: 2013
- Место издания: Turkey
- Первая страница: 117
- Последняя страница: 117
- Аннотация: The dynamic water pressure under the seismic vibrations varies by properties of the ocean-bottom sediment’s permeability, refraction and reflection characteristics of seismic waves at the layers’ structure, deployed water depth and their dynamic response etc. This is why observed water pressure recorded by the ocean-bottom gauges are complicated during large earthquakes in any case, and the applicability of sophisticated analyses is limited by the uncertainties associated with the ocean-bottom behavior and parameter determination under the dynamic conditions. Entire water pressure fluctuations have been recorded during the mega-thrust 2011 Tohoku, Japan earthquake (Mw9.0) by two ocean-bottom pressure gauges of the JAMSTEC cabled observatory in the intermediate field, i.e., approximately 400 km north from the tsunami source. Here we suggest a range of analysis methodologies in the simplified assumptions in which the dynamic response of water layers depends on frequency bands applying the incident seismic waves. In the present study, the observed water pressure have been analyzed by the time-frequency processing, and followed by comparing to the ocean-bottom seismometers nearby. As a result, acoustic resonances of water layer have been apparently involved by the incident seismic waves even in the intermediate field. The present study implies that the water pressure during the 2011 Tohoku earthquake are dominated by the ocean-bottom acceleration and velocity for the intermediate- and the high-frequency ranges, respectively, and its boundary fairly coincides to the fundamental acoustic resonant frequency. In the low frequency range, on the other hand, water pressure is independent on the bottom oscillations. Using these frequency characteristics of water pressure response, tsunami would be extracted from the observed water pressure. Although more sophisticated methods should be justified for the quantitative interpretations of the dynamic water pressure subjected to seismic vibrations, our simple method is adequate in the practical use for early tsunami detection.
- Добавил в систему: Носов Михаил Александрович