Hawaii’s Big Island Shaken by 4.2 Magnitude Earthquake

A 4.2-magnitude earthquake came offshore of the southern coast of the Big Island on Tuesday morning, reminding residents of the region's geologic crisis. The earthquake was powerful enough to be felt throughout parts of the island, but authorities quickly assured that there had been no tsunami warning and no damage was expected. It is one of a series of earthquakes that continue to afflict the region, especially in and around active volcanic regions.

Here, we'll explore what happened, why Hawaii is susceptible to such quakes, the contribution of nearby volcanoes like Kīlauea and Mauna Loa, and what citizens can do to be prepared for such quakes in the future.

What Occurred: Overview of the May 28 Earthquake

At 9:37 a.m. local time, May 28, 2025, the U.S. Geological Survey (USGS) recorded a magnitude-4.2 earthquake approximately 5 miles southeast of Pāhala, along the coast of Ka'u. The quake was approximately 20 miles beneath the seafloor, depths typical of tectonic activity related to volcanic processes.

• Magnitude: 4.2
• Depth: 20 miles
• Location: Off the Big Island's southern coast, close to Pāhala
• Felt Reports: About 40 residents felt slight shaking
• Tsunami Hazard: None
• Damage: None to infrastructure or buildings reported

Although the earthquake itself did not result in any major disruption, it was felt because it was preceded by a series of small tremors days prior, telling of the geologic restlessness of the island.

Why is Hawaii so seismically active?

The Hawaiian Islands sit above a hotspot in the Earth's mantle and thus are among the most volcanically active sites on the planet. Hawaiian earthquakes are generally due to volcanic activity, shifting magma, or tectonic movement deep below the island.

Major Reasons for Earthquakes in Hawaii

Here are some reasons that could be some of the reasons for the earthquake.

• Magma Movement: Movement of magma in fissures beneath the Earth can cause rocks to fracture, generating tremors.
• Tectonic Stress: The Big Island's mass and the movements of oceanic crust cause quakes.
• Volcanic Eruptions: Eruptions of active volcanoes such as Kīlauea or Mauna Loa tend to follow seismic swarms.

The USGS reported that seismic swarms have been occurring by Pāhala since 2019, with reports as early as the 1960s. The trends aren't new, but are closely monitored for any sign of acceleration.

The Role of Kīlauea and Mauna Loa

Though the earthquake was close to two of Hawaii's most active volcanoes, Kīlauea and Mauna Loa, scientists say the quake did not directly impact their activity.

• Kīlauea Volcano: Continued to be active last week, with minor eruptions and steam releases emanating from the Halemaʻumaʻu crater.
• Mauna Loa: No abnormal activity. It is stable at the moment.

Both volcanoes lie within the broader landscape of the Big Island. The earthquake itself on Tuesday did not impact volcanic activity, but it occurred in a known hotspot for energy related to the subsurface movement of magma.

Recent Earthquake Activity: Trend or an Anomaly?

The 4.2 earthquake is only one in a sequence of small earthquakes, also known as a seismic swarm. Swarms persist for days or weeks and are monitored closely for evidence of a pending eruption.

Recent earthquake magnitudes in the region:

• 1.5 – 2.3: Certain events of the past few days
• 4.2: Tuesday morning main event
• Seismic activity observed since the 1960s

While this particular event is not a sign of a forthcoming eruption, the normal activity is a reminder that Hawaii's geologic processes are constantly in motion beneath the surface.

Survival in an Earthquake Zone

No damage was reported, residents and tourists must be prepared for seismic activity. The Hawaiian Islands have a system in place to manage larger earthquakes and eruptions, but personal preparation remains key.

Hawaii Earthquake Safety Tips for Residents

Here are some tips for residents to keep them safe:

• Be updated: Take updates from the Hawaii Emergency Management Agency and USGS.
• Secure Your Home: Move bookshelves, appliances, and heavy furniture to the walls.
• Ready a Go-Bag: Water, food, flashlight, first aid kit, and essential documents.
• Learn Evacuation Paths: Especially if you live near the coast or volcanoes.
• Practice Earthquake Drill: "Drop, Cover, and Hold On" can be a lifesaver when a big earthquake strikes.

Conclusion

Tuesday's off-shore quake off the Big Island was a gentle but unmistakable reminder of Hawaii's dynamic geology. Though it did no damage and posed no threat of a tsunami, it is another notch on the belt of the ongoing string of quakes that scientists are keeping watch on closely. With volcanoes erupting nearby as we speak and centuries of seismic record, preparedness is not just a precautionary step, it's a way of life for those who live on the beautiful but dynamic Hawaiian Islands.