4. Tsunamis of Volcanic Origin
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Figure 7
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[19] In the Introduction we described the data about volcanic tsunamis in the lakes of New
Zealand and Philippines. One of the known examples of tsunami of volcanic origin in Russia is
eruption of underwater volcano in Lake Karymskoye on 2 January 1996, which lasted 10-20 hours
[Belousov et al., 2000].
The size of the lake is relatively small: its diameter is 4 km and the
depth is 40-70 m. It is shown in Figure 7. Measured runup of tsunami waves is also shown in this
figure. The eruptions were of explosion character and appeared every 5 minutes. Eruption of the
volcano was recorded on video tape, which testifies that velocities of eruption reached 110 m s
-1,
while the elevation of the tsunami source was 130 m with axial symmetry, which propagated in
radial directions with velocities of 20-40 m s
-1. The runup of tsunami wave at the closest coast
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Figure 8
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(approximately 1 km from the crater) exceeded 30 m and caused erosion of the shore (Figure 8).
[20] Karymskoye tsunami confirms the main properties of volcanic tsunami: small size of the source,
very high wave heights near the epicenter, and rapid decay of the height with distance. We note that in
1883, the famous eruption of Krakatau volcano in Soende Strait (Indonesia) led to a runup of the
waves with maximal value equal to 45 m causing 36,000 deaths at the coasts of the strait.
Tsunami waves from this eruption were recorded in many countries. The analysis of pressure
gauge records of this tsunami was made in
[Pelinovsky et al., 2005].
The Karymskoye eruption is weaker than the Krakatau, but however it led to very high waves (30 m)
so that long term hazard of volcanic tsunamis in Kamchatka and Kuril Islands should be specially
calculated.
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