Complex hazard cascade culminating in the Anak Krakatau sector collapse

Area of Science:

• Volcanology
• Geophysics
• Natural Hazards

Background:

• Volcanic islands are prone to flank instability and sector collapses.
• Sector collapses can trigger devastating tsunamis, as seen at Anak Krakatau.

Purpose of the Study:

• To investigate the precursor processes leading to the Anak Krakatau sector collapse and tsunami.
• To understand the hazard cascade and improve early detection of flank instability.

Main Methods:

• Utilized multiparametric ground-based and space-borne data.
• Analyzed seismic signals, thermal anomalies, and surface deformation.

Main Results:

• Anak Krakatau showed precursory thermal anomalies and increased surface area before collapse.
• A gradual seaward flank motion was detected on a dipping décollement.
• A small earthquake preceded the flank collapse by two minutes, triggering a fatal tsunami.

Conclusions:

• The Anak Krakatau event highlights a complex hazard cascade initiated by flank instability.
• Understanding precursor processes is crucial for early warning systems for volcanic flank collapses.