FY 1997

Short-term forecasts of inundation during teletsunamis in the eastern North Pacific Ocean

Mofjeld, H.O., F.I. González, and J.C. Newman

In Perspectives on Tsunami Hazards Reduction, G. Hebenstreit (ed.), Kluwer Academic Publishers, 145–155 (1997)

It is found empirically that, at tide gauges in the eastern North Pacific, later waves in a teletsunami are bounded in amplitude by envelopes that can be determined from observations of earlier waves at the same site. This is illustrated using the teletsunamis generated by the 4 October 1994 Shikotan earthquake. The envelopes have the form (t) = A_T in which t is the time since the local onset of the tsunami and _T is the standard deviation of the tsunami-band fluctuations that are observed in a time interval T immediately preceding t. For t 10 hr, T = t+2 hr and T = 12 hr thereafter. Values for the multiplicative factor A = 3.0 and the temporal parameters for T were determined by tuning the envelope to several teletsunamis. In principle, such envelopes can be extrapolated forward in time and added to predictions of background water levels to forecast the maximum elevations of tsunami waves that might occur during the next few hours. However, several issues need to be addressed before such a scheme can be used operationally. These include the choice of inundation thresholds that are appropriate for tsunamis and the spatial distribution of gauges needed to adequately monitor tsunami waves in a region.