USGS Records 6.9 Magnitude Earthquake Near Macquarie Island, No Tsunami Threat Detected

A formidable earthquake, with a magnitude of 6.9 as registered by the U.S. Geological Survey (USGS), impacted the Macquarie Island region in the Southern Ocean at 22:10 UTC on July 28, 2025. The depth reported by the agency was 31 kilometers (19.2 miles). The earthquake's epicenter was situated approximately 1,436 kilometers (892 miles) southwest of Bluff, in New Zealand's Southland region, placing it in a remote section of the ocean between Australia, New Zealand, and Antarctica. Despite the strength of the tremor, no tsunami warnings were issued, as the Pacific Tsunami Warning Center (PTWC) indicated that the earthquake did not meet the criteria that would generate a tsunami threat.

This seismic event was accompanied by several aftershocks, including ones measuring M5.4 at 22:20 UTC, M5.1 at 22:59 UTC, and a shallow M5.4 at 00:21 UTC on July 29. Notably, it follows a series of earthquakes, including two shallow M6.2 tremors recorded in the same region on July 25 and 26, aligning with the seismic activity this area is known for due to the tectonic interactions of the Australian and Pacific Plates. These interactions have historically resulted in regular occurrences of earthquakes measuring above M6.5.

The USGS issued a Green alert concerning potential fatalities and economic losses, reflecting a low probability of casualties and infrastructural damage. This assessment stems from the area's sparse population and the construction resilience of buildings against seismic events. The dominant vulnerable building types remain informal structures and unreinforced brick masonry constructions.

In tracking regional seismicity, prior quakes included a notable M6.2 tremor west of Macquarie Island at 11:22 UTC on July 25, which also reported a depth of 10 kilometers (6.2 miles) without generating a tsunami threat. On July 26, another earthquake of magnitude M6.2 occurred at a similar depth at 16:15 UTC. Both of these earlier earthquakes similarly prompted a Green alert and underscored the resilience of the structures in proximity to the epicenters.

The seismic activity aligns with the region’s historical pattern, where tectonic dynamics frequently contribute to moderate to strong earthquakes. The continued occurrence of such events reinforces the necessity for ongoing monitoring by geological agencies to enhance prediction accuracy and mitigate potential risks associated with future seismic disturbances.