Russian Academy of SciencesFar East BranchInstitute of Marine Geology & Geophysics

Yu. KorolevYu. KorolevYu. KorolevYu. Korolev

THE RETROSPECTIVE SHORT-TERM THE RETROSPECTIVE SHORT-TERM

TSUNAMI FORECASTTSUNAMI FORECAST

THE RETROSPECTIVE SHORT-TERM THE RETROSPECTIVE SHORT-TERM

TSUNAMI FORECASTTSUNAMI FORECAST

Novosibirsk 200Novosibirsk 20099

24th International Tsunami Symposium of the IUGG Tsunami Commission

From the point of view of tsunami warning services the short-term

forecast should consist in determination of detail features of a tsunami: time

of tsunami attack, the number of waves and waves' heights, time intervals

between them, expected time of tsunami alarm canceling, - for each points

to be warned. The short-term tsunami forecast should be implemented in real-time

mode.

The tsunami alarm should be declared only in those points, in

which tsunamis are to be of actual threat.

Such detail forecast based on magnitude criterion is impossible.

For this reason the acting tsunami warning services, not passing practically

any event, declare up to 80 % of false alarms. It is obvious, that false

tsunami alarms are accompanied by various losses.

Information, on which the forecast working-out is possible, are data

on an ocean level in points, remote from coast. Just open-sea stations

allow to make up an adequate forecast.

One of solutions of the tsunami early warning problem, using sea

level data, is offered.

The approximate solution is based on a known reciprocity principle

of being outcome of a symmetry of Green's function of a wave equation.

The presenting method may be applied to short-term tsunami

forecast regardless of tsunami generation nature. Tsunami sources may

be seismic one, subsea landslide one or others.

),(

),(),(),(

Ms

AsMsAs

T

TTT

А – point near coast to be warned, M – point of level gauge, T – earthquake epicenter

),( MsT - sea level data in М (Laplace transform)

),( AsT

),( MsT

- computed level in А from auxiliary axial source with center in Т (Laplace transform)

-computed level in M from auxiliary axial source with center in Т (Laplace transform)

Basic relation for tsunami estimation –Basic relation for tsunami estimation – method for early tsunami method for early tsunami forecastforecast

The concrete nature of the tsunami source is of no importanceThe concrete nature of the tsunami source is of no importance

Necessary information for computation:Necessary information for computation:Necessary information for computation:Necessary information for computation:

Co-ordinates of earthquake epicenter.Co-ordinates of earthquake epicenter.

Computed level data from auxiliary source in level gauge point and in point Computed level data from auxiliary source in level gauge point and in point to be warned.to be warned.

Tsunami level data in level gauge point.Tsunami level data in level gauge point.

Co-ordinates of earthquake epicenter.Co-ordinates of earthquake epicenter.

Computed level data from auxiliary source in level gauge point and in point Computed level data from auxiliary source in level gauge point and in point to be warned.to be warned.

Tsunami level data in level gauge point.Tsunami level data in level gauge point.

Practically method consists in transfer function creation, allowing

to compute a tsunami waveform in any specific point based on sea level

data. The transfer function is formed during an event.

Practically method consists in transfer function creation, allowing

to compute a tsunami waveform in any specific point based on sea level

data. The transfer function is formed during an event.

The presenting method was applied to retrospective

short-term tsunami forecast in Northern Pacific.

Events of 1996, 2006, 2007 and 2009 were simulated.

The presenting method was applied to retrospective

short-term tsunami forecast in Northern Pacific.

Events of 1996, 2006, 2007 and 2009 were simulated.

The information about earthquakes epicenters

coordinates and ocean level data of BPR’s (first generation

of deep-sea level stations) and data of DART system

stations were used for modeling.

The numerical modeling simulated forecast working-

out in real-time mode.

The information about earthquakes epicenters

coordinates and ocean level data of BPR’s (first generation

of deep-sea level stations) and data of DART system

stations were used for modeling.

The numerical modeling simulated forecast working-

out in real-time mode.

Epicenter co-ordinates 51º33’48”N, 177º37’54”WEpicenter co-ordinates 51º33’48”N, 177º37’54”W

Sea depth in epicenter 176.6 m (on bathymetry data)Sea depth in epicenter 176.6 m (on bathymetry data)

AK-70 097 1751.9 1794.4

AK-71 101 4831.8 4833.6

AK-72 102 4943.1 4706.8

AK-73 103 4872.0 4651.0

WC-67 114 1564.9 1969.4

BPR Point on scheme

Sea depth, real, m Water depth on bathymetry, m

Auxiliary source: diameter 50 km, max amplitude 8 m.Auxiliary source: diameter 50 km, max amplitude 8 m.

1996 Andreanov tsunami.1996 Andreanov tsunami.

P A C I F I C P A C I F I C

ALASKA

102

102

2006 Simushir tsunamiEpicenter co-ordinates 46º48’N, 153º12’E

Auxiliary source: diameter 75 km, max amplitude 10 m.

Sea depth in epicenter 2802.7 m (on bathymetry data).

2006 Simushir tsunamiEpicenter co-ordinates 46º48’N, 153º12’E

Auxiliary source: diameter 75 km, max amplitude 10 m.

Sea depth in epicenter 2802.7 m (on bathymetry data).

2007 Simushir tsunamiEpicenter co-ordinates 46º30’N, 154º24’E

Auxiliary source: diameter 75 km, max amplitude 10 m.

Sea depth in epicenter 6876.8 m (on bathymetry data).

2007 Simushir tsunamiEpicenter co-ordinates 46º30’N, 154º24’E

Auxiliary source: diameter 75 km, max amplitude 10 m.

Sea depth in epicenter 6876.8 m (on bathymetry data).

2009 Simushir tsunamiEpicenter co-ordinates 46º50’18”N, 155º11’18”E

Auxiliary source: diameter 50 km, max amplitude 8 m.

Sea depth in epicenter 6644.7 m (on bathymetry data).

2009 Simushir tsunamiEpicenter co-ordinates 46º50’18”N, 155º11’18”E

Auxiliary source: diameter 50 km, max amplitude 8 m.

Sea depth in epicenter 6644.7 m (on bathymetry data).

2006

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2006

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200721414

2007

21413

200921416

C O N C L U S I O NC O N C L U S I O N

The method of short-term tsunami forecast using level data in a one remote from a coast point:

- permits to estimate a tsunami waveform in a good time at any given ocean point;

- the only seismological information about earthquake epicenter coordinates and time of event is required;

- the tsunami forecast can be executed in real-time mode;

- transfer function can be created during event. No previously computed data base is required;

- the method can be applied in any areas, especially in those which has no beforehand created synthetic mareograms database and in those in which warning system is developing;

- the method can be used by local tsunami warning services, if they can receive sea level information on-line.

Aсknowledgements

Author thanks Vasily Titov for given numerical level data of 1996 Andreanov tsunami and Victor Kaistrenko for useful discussions.

The work was supported by Russian Foundation for Basic Research (grant 08-05-99098) and Far East Branch of Russian Academy of Sciences (grant 06-III-A-07-248).