Tsunami Laboratory
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Institute of Computational Mathematics and Mathematical Geophysics.

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Tsunami General Info

I(Mw) diagram for "red", "green" and "blue" tsunamigenic earthquakes occurred in the Pacific in 1900-1998

Another study (Gusiakov, 2001) was made to investigate the difference between the measured tsunami intensity and the expected intensity calculated on the basis of the moment-magnitude of an event. In the paper (Chubarov, Gusiakov, 1985), the theoretical dependence of the tsunami intensity I on the moment magnitude of an earthquake Mw has been obtained (I = 3.55Mw - 27.1). This formula was obtained on the basis of the coseismic bottom displacement model of the tsunami generation. If we know the actually observed intensity Iobs, we can estimate the difference dI between the observed and the expected tsunami intensity (dI = Iobs - Iexp,).

In this study, we have introduced a formal classification of the Pacific tsunamigenic earthquakes on the basis of their dI parameter. Based on the dI value, we divided all tsunamigenic earthquakes with known I and Mw into the three groups: "red" (dI>1), "green" (-1<=dI<=1), and "blue" (dI <-1). From 293 tsunamigenic events that occurred in the Pacific from 1900 to 1998 and which have both I and Mw values, 90 events fall within the "red" group, 153 are within the "green" group and 50 events are within the "blue" group. The analysis of average magnitudes, source mechanisms, source and water depths, does not indicate to any significant differences between the three selected groups of the Pacific tsunamigenic earthquakes. With a few exceptions, all of these earthquakes are shallow events with typical subduction zone mechanisms; reverse dip-slip or low-angle thrust. However, analysis of their geographical distribution immediately indicates a clear correlation with the climatic and circum-continental zonation in the oceanic sedimentation as described in Lisitsyn (1974, 1988).

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