The geodynamic meaning of the great Sumatran earthquake: Inferences from short time windows

Abstract

The difference between the value of seismic moment computed using the surface wave data and the value derived from the normal modes of the Earth requires reinterpretation of the focal mechanism of the Great Sumatran Earthquake (TU=26 December 2004 - 00h 58m, Lat=3.3°N, Lon=95.8°E, H=30 km, M=9.3) based on the second conjugate – near vertical CMT fault plane solution. The displacement of the Earth’s instantaneous rotation pole – observed at ASI of Matera, Italy –, the seismic data (USGS) in the two days following the main shock, the high frequency P-wave radiation, the geomorphologic data, and the satellite data of uplift/subsidence of the coasts (IGG) converge toward this interpretation. A thorough revision or a complete overcoming of the subduction concept is then needed.