本計畫為建立台灣近海海域的海嘯預警系統，我們依據海嘯波可以被表示成單位海嘯的線性組合之原理來建立此系統，所謂單位海嘯即在特定的單位平方面積中，產生一公尺高的海底地形變化所造成的海嘯波，在此計畫中，單位平方面積的邊長為0.25度。我們將掃描北緯18度、27度以及東經118度、125度海域中所有單位海嘯，模擬各單位海嘯的傳播，並紀錄到達各潮位站的波形以建立資料庫。我們採用(COMCOT)來進行海嘯波的模擬。 以此方式建立的海嘯預警系統有兩大優點： 1.將海嘯模擬中最費時的傳播過程計算，事先算好存成資料庫，使得此系統可達成近海海嘯預警所需的時效性。 2.單位海嘯的比重係數可根據每個地震求得，使得此系統可準確預測各個地震所造成的海嘯波警所需的時效性。 ; The active seismic activities around Taiwan suggest the necessity of a nearfield tsunami warning system in Taiwan. To build the system, we adopt the principle that tsunami waves can be expressed as a linear combination of unit tsunamis (Lee et al., 2005). Here, the unit tsunamis are the tsunami waves initiated by a source of a square box with 0.25° in dimension and 1 meter high seafloor displacement. We scan over the region bounded by 18°N, 27°N, 118°E, and 125°E to simulate the propagations of unit tsunamis of all box sources. The time evolution of unit-tsunami waves thus calculated for currently existing tidal stations are stored in database. Simulation of tsunami propagation is done using COMCOT (Liu et al., 1998). Since the Central Weather Bureau in Taipei is able to report the location, depth and ML of earthquakes in the region within minutes, it takes no time to calculate the seafloor displacements of the earthquake by converting ML to MW and adopting in situ empirical focal mechanisms (Okada, 1986). Accordingly, the coefficients of unit tsunamis for each source box are derived and used to synthesize the tsunami waves of the earthquake for certain tidal stations. Merits of this approach are two folds. (1) By calculating the time consuming part of wave propagation in advance, the warning system is able to do rapid forecasting for nearfield tsunamis. (2) By determining the coefficients on an event by event basis, the system is flexible to cover all scenario earthquakes with a reasonable size of database. ; 研究期間 9801 ~ 9812
