Geoscience Reference
In-Depth Information
and meteorological phenomena. Moreover, satellite altimetry has been shown and
confirmed experimentally to serve as an effective means for studying deviations of
the vertical slope, the ocean bottom relief and the dynamics of the World Ocean
surface.
Taking into account the prospects of applying satellite altimetry for resolving
the above-indicated broad class of problems, intensive work was initiated during
the period after 1980 for creating a new class of high-precision radio-altimeters
and EAS, to be equipped with them. From the middle of the 1980s till the present
day, seven EAS with high-precision radio-altimeters on board were put into orbit.
During this period the precision in determining the orbit improved from 45 to 5 cm,
while the measurement precision was improved from 1.5 m to 3-6 cm. The latest
models of EAS (JASON-1, ENVISAT-1), put into orbit in 2001 and 2002 provide
for a root-mean-square measurement error within 2 cm.
Original satellite altimetry databases have been created and are regularly up-
dated, which are available for scientific purposes in the Distributed Archive of
physical oceanography of the Jet Propulsion Laboratory of the California Institute
of Technology (PO.DAAC) in the USA and the Center for satellite oceanographic
data storage, control and interpretation (AVISO) in Europe.
An integrated database for satellite altimetry (IDBSA) and a System for automa-
tized satellite altimetry data processing have also been created in the RAS geophys-
ical center (RAS GC) with support of the RFBR. The database includes altimetry
data from satellites GEOIC, GEOSAT, TOPEX/POSEIDON, ERS 1,2, GFO and
JASON for the period from 1985 to 2003. The System for automized data process-
ing, designed in the RAS GC, supports all data formats adopted in foreign centres,
and IDBSA.
The first attempts at applying satellite altimetry data in searching for tsunamis
in the open ocean were evidently made by American specialists in 1994-1999
[Okal et al. (1999)]. They analysed satellite altimetry data, obtained in the experi-
ments TOPEX/POSEIDON, related to several strongest tsunamigenic earthquakes:
the Nicaragua tsunami of September 2, 1992, the Okushiri tsunami of July 12, 1993,
the tsunami of June 2, 1994, on the island Java and the Shikotan tsunami of October
4, 1994. Spectral analysis has only permitted to identify definitively the wave of
the 1992 Nicaragua tsunami.
Tsunami researchers recently developed an improved procedure [Zaichenko et al.
(2005)] of satellite information processing that comprised several stages for the reg-
istration of tsunami waves in the open ocean. At the first stage, the satellite cycle,
corresponding to the tsunamigenic earthquake, was chosen. Then, all the routes of
this cycle covering the Pacific Ocean were selected from the database of the RAS
GC. The satellite circuits preceding the earthquake were further discarded. At
the same time the model, chosen for calculation of the arrival time of the waves,
was applied to calculate the position of the wave front in the case of each tsunami
source. Calculation of the arrival times was based on bathymetric data with a space
resolution of 2 min. Further, for each point of the satellite route comparison was per-
formed of the satellite time, counted from the earthquake origination moment, and
