Sat Dec 21 01:50:00 UTC 2024: ## Silent Earthquake Detected Off Hawke’s Bay Coast

**Wellington, NZ** – GeoNet scientists are monitoring a slow-slip earthquake (SSE) currently underway near Hawke’s Bay. This “silent” earthquake, unfolding over weeks rather than seconds, is not felt by people and doesn’t register on standard seismographs. Instead, it’s detected by GPS instruments tracking millimetre-level ground movement.

The SSE, which began in early December, shows approximately 4cm of eastward and 1cm of southward movement in GNSS stations north of the Mahia Peninsula, with several centimeters of displacement also observed between Wairoa and Tolaga Bay. This represents one to two years’ worth of typical plate movement compressed into three weeks.

This event occurs along the Hikurangi Subduction Zone, where the Australian and Pacific tectonic plates meet. Slow-slip events are common in this area, with the last reported event occurring in June 2023. While these events relieve stress on the plate boundary, they can also increase stress elsewhere, potentially triggering smaller, felt earthquakes.

Researchers are utilizing a network of approximately 50 offshore sensors—part of an international collaboration—to study the SSE. These sensors, deployed annually for nearly a decade, collect geodetic, seismic, and oceanographic data to improve understanding of the subduction zone. GeoNet will release more detailed information in the new year.

The public is reminded of earthquake safety protocols: Drop, Cover, and Hold. For strong earthquakes or long, weak tremors near the coast, immediately evacuate to high ground to avoid potential tsunamis. Further information on earthquake preparedness is available from the National Emergency Management Agency (NEMA) and the Natural Hazards Commission Toka Tū Ake.

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