Fig. 5: Seismic reflection SPARKER profiles across the Krakatau caldera basin collected in 2017, before the flank collapse, showing the simple basin geometry and lack of landslide debris at the surface.
From: Submarine landslide megablocks show half of Anak Krakatau island failed on December 22nd, 2018
Seismic reflection profiles SS-11C (A), SS-11D (B), and SS-5B (C) show 25–42 m (average 34 m) deposition between 1883 and 1990 within the caldera basin within three regular packages. There is no evidence of mass movements apart from minor, old, buried debris flows (represented by thin-bedded acoustically chaotic facies). Sediments likely from Anak Krakatau initially onlap basement caldera faults and infill irregularities in the basement topography. Basin stratigraphy above an initial sediment package is represented by horizontal planar reflectors.
