Magnitude 5.7 Strong Earthquake Recorded Near 180 km NW of Hihifo, Tonga

Seismologists have recorded a magnitude 5.7 earthquake in the Pacific region, with the epicentre located 180 km NW of Hihifo, Tonga. The event occurred at 14:41 UTC on Wednesday, September 23, 2026 and originated at a depth of 10.0 km.

Seismic Context for the Pacific region

The Pacific Ocean basin is ringed by the world's most active subduction zones, collectively known as the Ring of Fire. This region produces approximately 90% of the world's earthquakes and the great majority of its major tsunamis.

Pacific island nations face unique challenges: small land areas, limited evacuation options, and direct exposure to both strong shaking and tsunami inundation. The Pacific Tsunami Warning Center (PTWC) in Honolulu monitors the entire Pacific basin and issues alerts to member nations.

About This Event

At a focal depth of 10.0 km, this is classified as a shallow earthquake (0–70 km). Shallow events are typically the most damaging: the seismic energy has less distance to travel before reaching the surface, resulting in stronger and more abrupt ground shaking at the epicentre.

In terms of felt effects, a magnitude 5.7 earthquake is typically capable of causing significant damage, particularly to older or poorly built structures. Strong earthquakes cause severe shaking that is difficult to stand through. Duration can reach 30–60 seconds. Widespread damage to ordinary buildings is common; even some well-built structures may sustain damage. Strong ground motion can trigger landslides, liquefaction of saturated soils, and rupturing of underground infrastructure.

Understanding the Magnitude Scale

Earthquake magnitude is measured on a logarithmic scale — meaning each whole-number increase corresponds to roughly 32 times more energy released and approximately 10 times greater ground motion amplitude. A magnitude 5.7 event therefore releases significantly more energy than its number alone might suggest to the casual observer.

The energy released by a magnitude 5.7 earthquake is approximately the equivalent of a large mining explosion or small nuclear device. This is 32 times more energy than a magnitude 4.7 event — the logarithmic nature of the magnitude scale means each whole number increase represents about 32 times more energy.

This magnitude class poses a serious threat to older and poorly constructed buildings. Collapse is possible in the most vulnerable structures. Modern seismically designed buildings are expected to remain standing, though repair or demolition may be necessary after inspection.

What to Do After an Earthquake

Understanding the type of building you live or work in is one of the most important steps in earthquake preparedness. Older unreinforced masonry buildings and soft-storey apartment buildings are significantly more vulnerable than modern reinforced concrete or steel-frame structures. If you have concerns, consult a structural engineer.

Fasten heavy furniture — bookshelves, water heaters, cabinets — to walls using earthquake straps. Store breakable items on lower shelves and heavy items closest to the floor. These simple steps significantly reduce the risk of injury from falling objects.

Staying Informed

Coastal communities throughout the Pacific should treat any strong earthquake as a potential tsunami warning and move inland or to elevated ground without waiting for an official alert.

QuakeWatch publishes real-time earthquake data sourced from the USGS global catalog — covering every detected seismic event worldwide, 24 hours a day. Visit our live map to see this and all other recent earthquakes, or explore our guide to earthquake magnitude for a deeper understanding of what these numbers mean in practice.

Building Codes and Earthquake Resilience

One of the most effective tools against earthquake damage is modern building codes that specify how structures must be designed and constructed to withstand seismic forces. Countries with active fault zones have developed increasingly sophisticated seismic design standards over the past 50 years. However, the gap between modern code-compliant buildings and older existing structures remains a critical challenge in earthquake risk reduction worldwide. Building retrofit programmes and public awareness campaigns are key components of any national earthquake preparedness strategy.