A Systemic Risk Framework for Multi-Hazard Assessment in the Sunda Strait, Indonesia

Extending across Sumatra and Java, the Sunda Strait was selected due to its history of multiple interrelated hazards, including subduction earthquakes (Mw >7.5) and volcanic flank collapses such as the 2018 ~0.2–0.3 km³, The Anak Krakatau event generated local tsunamis (Syamsidik et al., 2020) and landslides triggered by both earthquakes and volcanic collapses. Historically, catastrophic volcanic tsunamis on the strait have been rare but significant, with the 1883 Krakatau eruption producing a region-wide tsunami, highlighting the potential for extreme cascading events. These overlapping hazards produce cascading impacts that exceed those of isolated events, particularly in high-risk areas such as the Ujung Kulon and Lampung areas. This study develops an integrated risk framework to quantify these interactions and deliver practical risk reduction measures.

The approach evaluates interacting hazards using hazard mapping, vulnerability analysis, PSHA/PTHA modeling, multi-hazard scenario testing, risk optimization, and institutional coordination. By combining hazard, exposure, vulnerability, and resilience/adaptive capacity data, it estimates expected losses and systemic risk. Expanded monitoring network, including new infrasound stations and adaptive evaluation, enhances accuracy and supports real-time management, making it particularly effective in Indonesia’s densely populated, multi-hazard regions.

Seismic hazards in the Sunda Strait are modeled using PSHA with ground-motion prediction equations, including 10% probability in 50 years (PGA ≈ 0.26 g; return period ≈ 475 years), based on Megathrust (plate boundary), Subduction Zone, Sumatra Fault, Lampung Microplate, Krakatau area, and Central Sunda Strait Zone. All hazards, including tsunamis like the 2018 Anak Krakatau event (triggered by side collapses producing waves up to 13 m high along Sumatra and Java coasts; Lavigne et al., 2019), volcanic activity, and landslides are integrated to develop comprehensive exceedance probability maps for the region.

The study quantifies interdependent hazards, identifies high-risk areas like Krakatau and surrounding areas, and provides probabilistic estimates of losses, casualties, and infrastructure exposure under compound scenarios. Critical monitoring gaps are emphasized, reinforcing the need for enhanced observational networks. The framework integrates hazards, exposure, and vulnerabilities to deliver practical recommendations for better monitoring, zoning, drills, and resilient infrastructure. While focused on the Sunda Strait, it is scalable across Indonesia, supporting real-time PTHA updates, pilot studies, and adaptive management to improve preparedness and inform regulatory decisions.