Citation

Talandier J. Nat. Hazards 1993; 7(3): 237-256.

Copyright

(Copyright © 1993, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/BF00662649

PMID

unavailable

Abstract

Since 1964, the Geophysical Laboratory in Tahiti has been charged with the responsibility of issuing tsunami warnings. But this research laboratory is also designed to conduct other missions. One of them is to study an oversee seismicity and volcanism in the South Central Pacific. For this activity the Geophysical Laboratory, which is also the French Polynesia Tsunami Warning Center (Centre Polynésien de Prévention des Tsunamis -- CPPT), processes the data recorded by the Polynesian Seismic Network which includes 21 short-period stations, 4 broad-band three-component long period stations, and 2 tide gauge stations. These stations are, for the most, telemetered to CPPT in Tahiti which is equipped wilh data processing capabilities. At CPPT, Tsunami Warning is based on the measurement of the Seismic Moment through the mantle magnitudeM m and the proportionality of observed tsunami height to this seismic moment. The new mantle magnitude scale,M m, uses the measurement of the mantle of Rayleigh and Love wave energy in the 50-300 s period range and is directly related to the seismic moment throughM m = logM o − 20. Knowledge of the seismic moment allows an estimation of a range of high seas amplitudes for the expectable tsunami. The relation that estimates the tsunami height according to the seismic moment is based on the normal mode tsunami theory but also fits a dataset of 17 tsunamis recorded at Papeete (PPT) since 1958. This procedure is fully automatic: a computer detects, locates and estimates the seismic moment through theM m magnitude and, in terms of moment, gives an amplitude window for the expected tsunami. These-several operations are executed in real time. In addition, the operator can use historical references and, if necessary, acoustic T waves. This automatic procedure, which has been operating at the CPPT since 1986, is certainly transposable and applicable to other tsunami warning centers that issue warnings for earthquakes detected more than 1000 km away, and has significant potential in the regional field.

Language: en