Dear tsunami colleagues:
I previously reported the Mt value for the Indian
Ocean Tsunami of December 26, 2004.  At that time, five
station data were available in the Indian Ocean.  Now nine
data are available, and the Mt is recalculated. 
This isthe second report dated January 27, 2005.
(1) For determining Mt we use formula, Mt = log H2 + log X + 5.55
(Ref. Abe, K., Phys. Earth Planet. Inter., 27, 194-205, 1981)
Mt: Tsunami magnitude
H2: Maximum crest-to-trough amplitude on tide gage record in m
X: Distance from epicenter to station along the shortest oceanic
     path in km


H2(m)  X(km)  Mt
Vishakapatnam, India    2.4 2070 9.3
Tuticorin, India  2.1 2100 9.2
Kochi, India 1.3 2400 9.0
Cocos Is., Australia 0.5 1820 8.5
Hillarys, Australia  0.9 4600 9.2
Hanimaadhoo, Maldive 2.2 2500 9.3
Male, Maldive 2.1 2500 9.3
Gan, Maldive 1.4 2500 9.1
Diego Garcia, Chagos A 0.8 2700 8.9

The average is 9.09, then Mt=9.1.  Note that this Mt
value is consistent with Mw=9.0 of the Harvard solution.

(2) Giving the Mt value, we can simply estimate run-up heights at
near-source distances by using the relation, Mt = 2log Hm + 6.6
(Ref. Abe, K., J. Seismol. Soc. Japan. 52, 369-377, 1999).
Here Hm is the maximum value of the local-mean run-up height
in m and the logarithmic mean of heights is taken over a distance
of about 40 km along the coast.  The maximum height Hmax is
estimated by 2Hm.
Giving Mt=9.1, we obtain Hm = 18m and Hmax = 36m.  These rough
estimate seems consistent with the in-situ measurements made at
Banda Aceh by the Tsuji's International Tsunami Survey Team.

(3) The known events with Mt=9.0 and greater are as follows
(Ref. Abe, K., J. Geophys. Res., 84, 1561-1568, 1979):

1837 Valdivia, Chile 9.3
1841 Kamchatka 9.0
1868 Arica, Chile 9.0
1877 Iquique, Chile 9.0
1846 Aleutians 9.3
1952 Kamchatka 9.0
1957 Aleutians 9.0
1960 Chile 9.4
1964 Alaska 9.1
2004 Sumatra, Indonesia 9.1

Yours sincerely,
Abe, K.
ERI, Tokyo Univ.  January 27, 2005


Dear Dr. Gusiakov and tsunami colleagues:
Dr. Gusiakov asked me if I estimated the Mt value for the Indian
Ocean Tsunami of December 26, 2004 and then I tried to do it. Five
station data are now available in Indian Ocean.

A formula is Mt = log H2 + log X + 5.55
(Ref. Abe, K., Phys. Earth Planet. Inter., 27, 194-205, 1981)
Mt: Tsunami magnitude
H2: Maximum crest-to-trough amplitude on tide gage record in meter
X: Distance from epicenter to station along the shortest oceanic path
in km


St H2(m) X(km) Mt
Vishakapatnam, India 2.4 2070 9.3
Tuticorin, India 2.1 2100 9.2
Kochi, India 1.3 2400 9.0
Cocos Is., Australia 0.5 1820 8.5
Hillarys, Australia 0.9 4600 9.2

The average is 9.0, then Mt=9.0. Note that this Mt
value is consistent with Mw=9.0 of the Harvard solution.

The tsunami events with Mt=9.0 and greater are as follows (Abe, K.,
J. Geophys. Res., 84, 1561-1568, 1979):

1837 Valdivia, Chile 9.3
1841 Kamchatka 9.0
1868 Arica, Chile 9.0
1877 Iquique, Chile 9.0
1946 Aleutians 9.3
1952 Kamchatka 9.0
1957 Aleutians 9.0
1960 Chile 9.4
1964 Alaska 9.1
2004 Sumatra, Indonesia 9.0


Yours sincerely,
Abe, K.
ERI, Tokyo Univ.

----------------------------------------------------------
Katsuyuki ABE, Earthquake Research Institute, Tokyo Univ.,
Yayoi 1-1-1, Bunkyo-ku, Tokyo, JAPAN 113-0032
Phone: +81-3-5841-5706, Fax: +81-3-5841-8262