The earthquake hazard in the State of Hawaii is among the highest in the United States. The south side of the Island of Hawai‘i is under the greatest threat, as evidenced by the three largest earthquakes that occurred there since 1868 . Strong earthquakes in Hawaii have destroyed buildings, roads, bridges, and utilities. Damage can be locally intensified by water-saturated soils that amplify earthquake ground motions. On steep slopes, intense shaking may cause such soils to fail, resulting in landslides and mudflows. Large offshore earthquakes can displace large volumes of water to form tsunamis, a series of sea waves that can be far more damaging than any of the direct seismic hazards.
Thousands of earthquakes occur every year in Hawaii, most on and around the Island of Hawai‘i. Many of these earthquakes are directly related to volcanic activity; these earthquakes are seldom large enough to cause widespread damage, but they may produce locally extensive ground fractures and subsidence.
Earthquakes that generate the strongest and most damaging ground shaking originate in zones of structural weakness at the base of the volcanoes and in the underlying lithosphere (includes the oceanic crust and upper mantle). For example, the magnitude 7.7 Kalapana earthquake in 1975 occurred at the base of Kīlauea Volcano at a depth of about 8.5 km (5.3 mi), and the magnitude 6.7 Kiholo Bay earthquake in 2006 occurred in the lithosphere at a depth of 29 km (18 mi). These deeper earthquakes also occur beneath and near the other Hawaiian Islands.
The historical earthquake record in Hawaii, which extends from the early 1800's to the present, can be used to estimate likely locations of future damaging earthquakes and the hazard they might pose in terms of ground shaking. These scenarios are used by land managers, government officials, and disaster response personnel to understand and plan for potential damage from and needed response to future earthquakes.
Seismic hazard is often characterized in terms peak ground acceleration (PGA) measured as a percent of Earth's gravitational acceleration (%g). The map to the right depicts the maximum PGA expected over the next 50 years with at least a 2% chance of exceedance. The southeast part of the Island of Hawai‘i has the highest expected ground acceleration at over 100 %g. This amount of acceleration would make it difficult to stand and could topple structures. Engineers use this type of information to develop building codes and design earthquake resistant structures. Non-engineers can use these maps to judge the relative seismic hazard, where high seismic hazards are depicted in warm (red-orange) colors. Learn more about Hawaii's seismic hazard map and the seismic hazard where you live and work.
|SDC||Map Color||Earthquake Hazard||Potential Effects of Shaking*|
|A||White||Very small probability of experiencing damaging earthquake effects.|
|B||Green||Could experience shaking of moderate intensity.||Moderate shaking—Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.|
|C||Yellow||Could experience strong shaking.||Strong shaking—Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built structures.|
|D0||Dark Yellow||Could experience very strong shaking (the darker the color, the stronger the shaking).||Very strong shaking—Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures.|
|E||Red||Near major active faults capable of producing the most intense shaking.||Strongest shaking—Damage considerable in specially designed structures; frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Shaking intense enough to completely destroy buildings.|
|* Abbreviated descriptions from The Modified Mercalli Intensity Scale.|
Three factors determine seismic risk: the level of seismic hazard, the number of people exposed to the hazard, and the vulnerability of property. Individuals, organizations and communities that have assessed their risks and implemented responsible preparedness and mitigation measures are likely to experience fewer casualties, less damage, and less disruption from earthquakes. Learn more at the National Earthquake Hazards Reduction Program (NEHRP).