[HDS10-P03] Detectability of seismic wave from the assumed landslide of the 1998
Keywords:tsunami by landslide, seismic record, the 1998 Papua New Guinea tsunami
The PMG seismic station is located at a distance of 900 km from the source area of the 1998 tsunami event. We checked the seismic record obtained at PMG with band-pass filters of various pass bands from 0.2 s to 50 s. However no distinct phase was recognized 10 minutes after the seismic wave from the earthquake Mw 7.0. This was already pointed out by Synolakis et al.(2002). Seismic data at JAY station is archived at Ocean Hemisphere Project Data Management Center of ERI. The JAY station was located at a distance of 150 km from the source area. No distinct phase was recognized at JAY, either.
Watts et al. (2003) estimated the landslide which could caused the 1998 tsunami at the length of 4.5km, the width of 5km, and the thickness of 760m (half ellipsoid). The mass was considered to have slumped on a slope of 12 degree dip with characteristic time of 32 s and acceleration of 0.36m/s2. The slump-supporting force should have changed during the landslide. Rough estimation of the force change is density (2.15X103kg/m3) X volume of the mass (9 km3) X the initial acceleration (0.36m/s2). It turn out to be 7X1012N. Synthetic wave due to the force was calculated with the method of Takeo (1985). The amplitude of the synthetic wave was no more than the amplitude of the coda wave of the preceding seismic event. Detection of seismic wave from submarine landslide can not be anticipated after a seismic event. An alternative measure would be monitoring of off-shore tsunami gauges.
We used seismic data archived in IRIS and Ocean Hemisphere Project Data Management Center of ERI. We used a program developed by Takeo (1985).