從海洋噪訊中重建水體特徵函數

在21世紀因為數個劇烈地震產生的海嘯已經帶來了嚴重的損失。為了減少自然災害帶來的損失，必須發展海嘯預警系統。現今有兩種主要的方法監測海嘯，一個是DART(Deep-ocean Assessment and Reporting of Tsunami)系統另一個是透過COMCOT(Cornell Multi-grid Coupled Tsunami model)軟體進行數值模擬。DART是透過海嘯儀連接浮標可以提供即時偵測的資訊，而COMCOT是主要是透過淺水波方程式模擬海嘯傳遞行為來預估到時。以上的兩種方法都需要很高的成本且沒辦法有效的預測近岸所產生的海嘯。從噪訊地震學中任意測站對記錄的連續資料互相關結果可以近似於測站間的格林函數得到了啟發。近年來，已經有許多透過噪訊資料進行互相關的研究且得到很好的結果。模擬上，Saito和Kawahara將模擬噪訊源所激發的海洋訊號傳遞至兩側站的結果進行互相關，發現其結果會近似於水體的的格林函數。而本研究將會驗證實際海洋噪訊互相關函數結果可否建立可信的水體特徵函數，如果可行，將可以有效的減少近域海嘯帶來的傷亡及破壞。

關鍵字

環境噪訊；互相關函數；海嘯預警系統；淺水波理論；海洋噪訊

並列摘要

In the 21st century, several huge tsunamis, triggered by immense earthquakes, have occurred and have caused catastrophic damages. To reduce natural disaster losses, the development of the Tsunami Warning System (TWS) is necessary. Nowadays, there are two major ways to monitor tsunamis. One is Deep-ocean Assessment and Reporting of Tsunami (DART) which uses the tsunameter connected with the buoy which can provide the real-time detection of the tsunami. Another is Cornell Multi-grid Coupled Tsunami model (COMCOT) which adopts scenario approaches to estimate the potential arrivals and wave height of the tsunami once the earthquake happened using the shallow water equation. These methods are expensive and can not forecast the local tsunami effectively. Inspiration by ambient noise seismic interferometry involving the cross-correlation of continuous signals at different receivers which can be used to retrieve the Green’s functions between any pair of stations. There are many promising results that have been demonstrated in recent years. In scenario, Saito and Kawahara retrieved the tsunami Green’s function from the cross-correlation of ocean waves which were excited by simulated noise source. The object of this work is to prove whether the technique can be used to obtain the eigenfunction of the water mass in reality. If it is feasible, the valid nearshore tsunami warning can save more lives and reduce damage.

並列關鍵字

Ambient Noise ； Cross-correlation Function ； Tsunami Warning System ； Shallow Water Equation ； Oceanic Noise

參考文獻

1. Saito, Tatsuhiko, and Jun Kawahara. "Retrieval of long-wave tsunami Green’s function from the cross-correlation of continuous ocean waves excited by far-field random noise sources on the basis of a first-order Born approximation." Earth, planets and space 64.1 (2012): 43-48. DOI: 10.5047/eps.2011.08.020

Google Scholar

2. Abdolali, Ali, Usama Kadri, and James T. Kirby. "Effect of water compressibility, sea-floor elasticity, and field gravitational potential on tsunami phase speed." Scientific reports 9.1 (2019): 1-8. DOI: 10.1038/s41598-019-52475-0

Google Scholar

3. Kubo, Rep. "The fluctuation-dissipation theorem." Reports on progress in physics 29.1 (1966): 255. DOI: 10.1088/0034-4885/29/1/306

Google Scholar

4. Claerbout, Jon F. "Synthesis of a layered medium from its acoustic transmission response." Geophysics 33.2 (1968): 264-269. DOI: 10.1190/1.1439927

Google Scholar

5. Lobkis, Oleg I., and Richard L. Weaver. "On the emergence of the Green’s function in the correlations of a diffuse field." The Journal of the Acoustical Society of America 110.6 (2001): 3011-3017. DOI: 10.1121/1.1417528

Google Scholar

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從海洋噪訊中重建水體特徵函數

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