House destroyed by earthquake in Kalapana on June 25, 1989

Engineers, seismologists, architects, and planners have carefully evaluated seismic hazards related to building construction. They have devised a system of classifying seismic hazards on the basis of the expected strength of ground shaking and the probability of the shaking actually occurring within a specified time. The results are included in the Uniform Building Code (UBC) seismic provisions.

The UBC seismic provisions contain six seismic zones, ranging from 0 (no chance of severe ground shaking) to 4 (10% chance of severe shaking in a 50-year interval). The shaking is quantified in terms of g-force (familiar to race car drivers and astronauts), the earth's gravitational acceleration. The diagram below is a way of describing seismic zonation.

Zonation Based on General Principles

Seismic-hazards analysis combines:

• Earthquake rates known from the historical record
• Information about how strong ground shaking dissipates with increasing distance from the earthquake
• Determination of the probabilities that specified levels of ground motion will occur in a specified time period

Jurisdiction Island 1988 Zone 1997 Zone County of Hawai`i Hawai`i 3 4 County of Maui Maui 2B 2B Kaho`olawe 2B 2B Lana`i 2B 2B Moloka`i 2B 2B City & County of Honolulu O`ahu 1 2A County of Kaua`i Kaua`i 1 1 Ni`ihau 1 1

For an overview of seismic hazards in Hawai`i, see the online USGS publication, Volcanic and Seismic Hazards on the Island of Hawai`i, reprinted in 1997.