At its 13^th session held in Bali, Indonesia during 28 November to 1 December 2022, the Intergovernmental Coordination Group for the Indian Ocean Tsunami Warning and Mitigation System (ICG/IOTWMS) decided to organise an Indian Ocean Wave Exercise (IOWave23) in 2023 and established a Task Team to plan and conduct the exercise.

Objectives: Exercise IOWave23 will simulate Indian Ocean countries being put in a tsunami warning situation and require the National Tsunami Warning Centre (NTWC) and the National and/or Local Disaster Management Offices (NDMOs/LDMOs) in each country to implement their Standard Operating Procedures (SOPs). The exercise will test the preparedness for responding to tsunamis generated by seismic and non-seismic (volcanic) events. In addition to testing the SOPs and communication links at all levels of the warning chain, a primary objective of IOWave23 is to enhance tsunami preparedness at community level. To this end, Exercise IOWave23 will also provide an opportunity for Member States to test the UNESCO-IOC Tsunami Ready programme indicators in communities. Guidelines and associated training resources for the UNESCO-IOC Tsunami Ready Programme can be downloaded online. All IOTWMS Member States are strongly encouraged to conduct the IOWave23 exercise to community level and test the indicators of UNESCO-IOC Tsunami Ready Programme in participating communities.

Dates and Scenarios: Exercise IOWave23 will comprise four scenarios with simulated tsunami waves travelling across the Indian Ocean basin. Member States are invited to participate in one or more events, which will run in real time.

• Scenario 1 starting at 04:00 UTC on Wednesday 4th October 2023: Magnitude ~9 earthquake in the Andaman trench off the west coast of Nicobar Islands, India.
• Scenario 2 starting at 06:00 UTC on Wednesday 11th October 2023: Magnitude ~9 earthquake in the Makran trench of the North-West Indian Ocean.
• Scenario 3 starting at 06:00 UTC (eruption at 05:00 UTC) on Wednesday 18th October 2023: Volcanic eruption of Heard Island in the Kerguelen Islands Region.
• Scenario 4 starting at 02:00 UTC on Wednesday 25th October 2023: Magnitude ~9 earthquake in the Java trench to the south of Java, Indonesia.

The IOWave23 Exercise Manual and Supplements can be downloaded via the links below.

• Exercise Manual
• Exercise Evaluation
• Supplement 1: Andaman Trench
• Supplement 2: Makran Trench
• Supplement 3: Heard Island Volcano
• Supplement 4: Java Trench