New USGS Model Shows Earthquake Hazard Probability for Hawaii Islands
Hawaiʻi Island is likely to experience damaging ground shaking from an earthquake in the next century a new study from the U.S. Geological Survey indicates.
According to the study, damaging ground shaking is likely to occur on Hawaiʻi Island as there is active volcanic activity. However, the neighbor islands are likely to experience such earthquakes as well, particularly Maui and Lanaʻi.
This updated ground-shaking model, published online in the journal Earthquake Spectra, shows a 90% chance that the 345,000 people on the islands of Hawai’i and Maui could experience damaging levels of shaking during the next 100 years. A lower but significant chance of damaging shaking is expected across Oahu; within the southeastern portion of the island near Honolulu there is a greater than 50% chance of damaging shaking occurring during this period (Figure 1).
Levels of shaking on the southernmost islands are comparable to shaking levels expected across portions of coastal California.
“The previous hazard model was developed over 20 years ago and since that time we have experienced several large earthquakes, volcanic eruptions, and have collected deformation, soil, and strong motion data that can be used to improve this forecast,” said Mark Petersen, USGS research geophysicist and lead author of the publication. “We collaborated with scientists and engineers across Hawaii and the rest of the U.S. to build these models. The new seismic hazard maps can be used to update building codes and other planning documents which should improve seismic safety across Hawai’i.”
Hawai’i is a seismically active state, as indicated by the thousands of earthquakes recorded each year by the USGS Hawaiian Volcano Observatory. Damaging ground shaking has occurred over the decades, with two magnitudes 6.7+ earthquakes in 2006 and 2018 and most recently a magnitude 5.2 earthquake on July 5, 2021, that was felt by more than 1,300 people and a magnitude 6.2 earthquake on Oct. 10, 2021, that was felt by more than 3,500 people.
Earthquakes are often associated with volcanic activity and, therefore, monitoring current volcanic activity is important as it could lead to large earthquakes. Kīlauea began erupting at the summit on Sept. 29, 2021. Earlier this week, HVO officials reported a pause in the eruption.
Ground shaking is forecasted to be highest near the active volcanos of Kīlauea and Mauna Loa in the southernmost portion of the Island of Hawai‘i. Here magmatic activity pushes the crust outward toward the ocean along a nearly horizontal fault located about 6 miles beneath the surface. Large earthquakes occurred on this zone in 1868, 1975, 2018 and 2021.
The 2018 earthquake was followed by a volcanic sequence that included numerous seismogenic collapses of Kīlauea volcano’s summit crater floor. These provided data that helped define the shaking levels predicted by the model.
“Repeated collapses of the volcanic caldera may have also caused damaging ground shaking during the 2018 volcanic eruption, so a new model was developed to evaluate this risk,” Petersen said.