Yes, Oahu does experience earthquakes. While these seismic events occur on the island, they are generally less frequent and less severe compared to those felt on other Hawaiian islands, particularly the Big Island.
Understanding Oahu’s Seismic Activity
Earthquakes on Oahu are typically minor to moderate in magnitude. Most seismic events across the Hawaiian Islands are small, often below magnitude 3.0. On Oahu, very few felt earthquakes occur annually.
When earthquakes are felt on Oahu, they are often perceived as mild shaking or rattling, sometimes described as a brief jolt. Historical data suggests that earthquakes with a Modified Mercalli Intensity of V or greater in Honolulu occur approximately every 125 to 158 years. Significant damage from local earthquakes on Oahu is uncommon.
Sources of Earthquakes in Hawaii
Earthquakes in the Hawaiian Islands stem from two primary geological processes: volcanic activity and tectonic forces. Volcanic earthquakes are directly linked to magma movement within active volcanoes, primarily Kilauea and Mauna Loa on the Big Island. These shifts can generate thousands of small earthquakes daily.
Even though these volcanic quakes originate on the Big Island, their energy can travel through the earth and be felt across the entire state, including Oahu, particularly for larger events. The immense weight of the Hawaiian Islands also creates tectonic stresses. This weight causes the Pacific Plate’s lithosphere to bend or “flex,” triggering flexural earthquakes. Some of these occur in the upper mantle and extend northward to islands like Oahu.
Another source of tectonic earthquakes involves stress release along fault lines, some located beneath and within volcanoes. These range from minor events to powerful flank earthquakes along a deep décollement fault, which separates the volcanic edifice from the underlying oceanic crust. Large-scale events, like the M6.7 earthquake in 2006 centered off the Big Island, can cause widespread effects such as power outages on Oahu.
Preparing for Seismic Events
While large, damaging earthquakes are less common on Oahu, preparedness is prudent.
During an Earthquake
The recommended safety action during an earthquake is “Drop, Cover, and Hold On.” This involves dropping to the ground, taking cover under a sturdy table or desk, and holding on until the shaking stops. If no sturdy furniture is available, crouch in an inside corner of a room and protect your head and neck.
Securing Your Home
Securing heavy items within your home can prevent injuries. Anchor tall bookcases and other top-heavy furniture to wall studs and block the rollers of heavy appliances. Ensure hanging items are securely fastened and positioned where they will not fall on people.
Outdoor and Tsunami Safety
If an earthquake occurs while outdoors, move to a clear area away from buildings, power lines, and trees. If driving, safely pull over to the side of the road, avoiding bridges, power lines, and overpasses, and remain in your vehicle until the shaking subsides. In coastal areas, a strong earthquake could generate a local tsunami. If near the shore and feeling strong shaking, immediately move to higher ground, at least 100 feet above sea level or one mile inland, without waiting for an official warning.
Emergency Supplies
Creating an emergency kit with at least 14 days of food, water, and other essentials is recommended. This kit should be easily accessible and include items like first-aid supplies, medications, and important documents.