Uplift of the 2004 Sumatra‐Andaman earthquake measured from differential hyperspectral imagery of coastal waters

Abstract

We describe a procedure to measure coseismic change of shallow coastal bathymetry using multispectral imagery. This technique is applied to HYPERION hyperspectral images acquired along the shallow coast of the North Andaman Islands to estimate the uplift induced by the Mw 9.15, 26 December 2004, earthquake. Attenuation coefficient of the particularly clear coastal waters is estimated from two preevent images with a 22 cm tide level difference. Various sources of noise on the estimate of the uplift resulting from atmospheric correction, data registration, sensor noise, and fundamental assumption of stationary optical properties of the scene with time are studied. Average uplift over the shallow bathymetry covered by the imagery is 0.85 ± 0.10 m, increasing from south to north from 0.56 ± 0.10 to 1.12 ± 0.10 m. The uplift amplitude is consistent with local field measurements. These data place constraints on the width of the megathrust rupture in the Andaman area, estimated to about 160 km, and on the amount of coseismic slip there estimated to about 10 m.