News
Climate Change to Double Tsunami Strike Power for 3 Vulnerable Mascarene Islands
Coastal communities across the Mascarene Islands face an amplified threat from tsunamis as rising sea levels act as a “risk multiplier,” experts have warned. While climate change does not directly trigger underwater earthquakes, the resulting higher sea levels allow tsunami waves to penetrate further inland, inundating previously safe areas and threatening vital infrastructure on low-lying islands like Mauritius and Rodrigues.
Seismic Contrast
Researcher Murughen Sadien highlights a stark contrast in seismic activity across the Indian Ocean. The north-west region, specifically the Sumatra-Andaman subduction zone, remains the primary engine for catastrophe. It was here that the 2004 Mw 9.1–9.3 earthquake triggered a global disaster affecting 14 countries.
In contrast, the south-west Indian Ocean—surrounding Mauritius, Rodrigues, and Madagascar—experiences more “moderate” seismic activity, typically ranging between Mw 5 and 6.5.
The Mechanics of a Wave
According to Mr Sadien, the danger lies in the physical movement of the seabed.
- Subduction Zones: In areas like Sumatra, tectonic plates slide under one another, creating massive vertical shifts that displace entire columns of water.
- Intraplate Seismicity: Near the Mascarenes, movements are primarily horizontal, which significantly limits their ability to generate local tsunamis.
However, the threat of “distant” tsunamis remains. While the 2004 event hit the Mascarenes with moderate intensity, archival records in Madagascar and Rodrigues suggest unusual wave activity has occurred in the past, even if historical data remains sparse.
Climate Change as a Catalyst
Addressing the link between the environment and geology, Mr Sadien clarified that climate change does not influence the frequency of deep tectonic earthquakes.
“Climate change acts as a ‘risk multiplier’,” he explained. “A higher sea level reduces the natural safety margin of our coastlines, increasing the probability of extreme submersion during rare but destructive events.”
Furthermore, extreme weather such as cyclones can weaken the islands’ natural defences.
The degradation of mangroves and coral reefs, combined with soil saturation from heavy rains, makes infrastructure more vulnerable to collapse if even a moderate tremor were to strike.
Emergency Response Protocols
To mitigate these compounding risks, the Mauritius Meteorological Services (MMS) operates a sophisticated multi-stage warning system:
| Level | Action |
| Seismic Info Bulletin | Issued for detected quakes with no immediate threat. |
| Watch / Advisory | Potential threat; maritime activities restricted; evacuation prep begins. |
| Tsunami Warning | Immediate threat confirmed; coastal evacuation and NEOC activation. |
| Final Bulletin | Issued only when the threat has definitively passed. |
The MMS coordinates with regional service providers to analyse sea-level sensors and coastal gauges, ensuring that alerts are maintained for several hours to account for successive wave fronts.
The Myth of Ocean Pressure
The research, led by doctoral candidate Murughen Sadien at the Université des Mascareignes and the University of Mauritius, clarifies a common misconception: rising sea levels do not significantly trigger major earthquakes.
Fault lines are typically located several kilometres deep, where the immense pressure of shifting tectonic plates far outweighs the minor weight changes caused by a few metres of rising water.
However, at a local level, such variations can act as a “triggering moment” for shallow faults that are already close to breaking point.
A “Climate-Seismic” Strategy
The study advocates for a multidisciplinary approach that treats climate change and tectonic threats as a single, complex challenge.
- Compounding Factors: Extreme rainfall can saturate soil, increasing the likelihood of landslides during even moderate tremors.
- Vulnerability: Rising sea levels and coastal erosion degrade natural protections like reefs, leaving islands more exposed to both storm surges and tsunamis.
- Volcanic Risks: The research also models underwater and coastal landslides, specifically those that could be triggered by the active Piton de la Fournaise volcano, which could generate local tsunamis.
Prediction vs. Preparation
Despite advancements in geophysical modelling, the report confirms that earthquakes remain fundamentally unpredictable.
Science cannot yet pinpoint the exact date, time, or magnitude of a future event.
Furthermore, research in the Indian Ocean faces significant hurdles. Current terrestrial networks struggle to detect underwater quakes accurately without a higher density of seabed seismometers and oceanic GPS stations.
This “data gap” leaves many active fault segments along mid-ocean ridges poorly understood.
Building Resilience
In the absence of exact predictions, the focus has shifted to community resilience. Murughen Sadien emphasises that education and practical drills, such as the biennial “IOWAVE” exercise, are the most effective tools for saving lives.
Residents are urged to follow a three-step safety protocol:
- Before: Secure heavy furniture, identify safe zones, and prepare emergency kits.
- During: “Drop, Cover, and Hold”—take shelter under sturdy furniture and protect the head.
- After: Check for injuries and avoid coastal areas until any tsunami threat is cleared by official bulletins.
“These measures are particularly crucial for small islands,” says Mr Sadien, noting that geographical isolation and limited infrastructure make rapid, informed community response a necessity for survival.
Source: Defi Media
