Did the 2004 Sumatra–Andaman Earthquake Involve a Component of Tsunami Earthquakes?
Tsunami earthquakes are characterized by (1) slow slip and (2) tsunamis larger than expected from seismic slip. We examine whether the 2004 Sumatra–Andaman earthquake had these features and thus involved a component of tsunami earthquakes. Fitting the effective moment versus frequency curve, we obtain characteristic times τ (Kanamori, 1972) of 70 and 290 sec. The former is on the scaling for normal earthquakes; the latter is longer. In the area off northern Sumatra, by back- projecting the wavefront recorded on the sea surface height (SSH) by the satellite altimetry, we estimate the seaward edge of the fault plane to be located at the deformation front. We then invert the SSH, assuming that the seaward edge of the fault is at this location, and obtain a maximum slip of 40 m, which was estimated to be 15 m previously. This amount of slip, approximately twice the slip estimated seismologically and geodetically, suggests that additional crustal deformation, such as inelastic uplift of the
