The 26 December 2004

The 26 December 2004, Mw9.0 (Ms8.8) Great Asian mega-thrust earthquake off the west coast of Northern Sumatra, requires special comment: The linear dimension of its source is about 1000-1300 km, i.e., about the diameter of Circles of Investigation used in the Global Test of M8 to predict M8.0+ earthquakes. The source length of the earthquakes predicted in the time interval 1985-2003 is usually between 150 and 400 km. Therefore, since the logic of our methodology suggests that the area of investigation should be about 5-10 times larger than the target earthquake size, it would be naive to expect monitoring designed for either M8.0+ or M7.5+ earthquakes to predict the 26 December 2004 event. According to the M8 algorithm predictions we were not expecting any M8.0+ or M7.5+ events in the Indian Ocean during the second half of 2004. If on July 1, 2004 someone had been sufficiently ambitious to extend application of the M8 algorithm into the uncalibrated magnitude range targeting M9.0+ earthquakes, he or she would have diagnosed Time of Increased Probability in advance of the 2004 Great Asian Quake. The M8 computer code run with the target earthquake magnitude threshold of 9.0 and the radius of CI’s of 3000 km establishes a current alarm. The figure below shows on the left the CI #34, centered at (3.00N, 97.00E), its zoom to 3000-km radius, along with the epicenter and first aftershocks of the 26 December 2004, Mw9.0, while on the right – the magnitude, location, and the values of the M8 functions versus time. As can be seen the current TIP expires by December 2005.