Insights from the 1975 Kīlauea volcano earthquake

The Lower East Rift Zone during the 2018 eruption of Kilauea volcano. Credit: USGS, Matt Patrick

Researchers from the University of Hawaii in the Department of Earth Sciences at Manoa evaluated 120 years of unprecedented data from Kīlauea volcano on the island of Hawaii and discovered, for the first time, century-long patterns of deformation and stress changes. They focused in particular on the 1975 magnitude 7.7 transformative Kalapana earthquake, which also generated a 20-foot tsunami. Their study was recently published in the journal Geophysical Research: Solid Earth.

“Deciphering Kīlauea’s history deepens our understanding of volcanic and seismic hazards,” said lead author Lauren Ward-Young, who conducted this study as part of her doctoral dissertation at the UH Manoa School of Ocean and Earth Sciences and Technology (SOEST). “It provides critical insights into how stress evolves in volcanic systems, guiding our ability to predict and interpret future earthquakes and magmatic events.”

The study highlights the potential dangers of decoupling, a major fault zone beneath Kīlauea volcano where two masses of rock move past each other, constantly pushing the volcano southward and posing the risk of major earthquakes combined with complex volcanic activity within the region.

Young and his colleagues explored the volcano's deformation and pressure changes from 1898 to 2018 by analyzing six different geodetic datasets. Their analysis included 338,396 earthquake observations and more than 15,000 measurements of surface motion, or displacements, to build a computational model that replicates the displacements and stresses observed before, during, and after the Great Kalapana Earthquake of 1975. This model identified key structural features, such as fault levels, fault zones, and magma chambers, That led to these changes.

Regional map of the southeastern part of the Big Island of Hawaii with elevations, bathymetry, and surface fault traces (top panel). Cross section of the AA′ profile shown at the top and approximate predicted locations of major geological features (bottom panel). Credit: Young, et al. (2024) Changing stress and motion

They discovered that the 1975 Kalapana earthquake had dramatically changed the state of stress and deformation in the region. Before 1975, at the site where the big earthquake originated, there was no evidence of slippage, a movement in which two rock masses move past each other.

“This result indicates that the area was most likely frictionally closed and stresses built up slowly over time before rupture,” Young said. “Furthermore, we observed that the southern flank of Kilauea, a geologically active area extending from the volcano's summit toward the coast, experienced larger and more complex displacement before the Kalapana earthquake than afterward.”

Young and colleagues' analysis of Kilauea's concavity found that average slip declined from 10 centimeters per year before the 1975 earthquake, to just four centimeters per year afterward. These differences in slip and stress distributions along the decolliment zone indicate changes in mechanical properties, such as friction, that influence seismic and magmatic activity in the region over time.

Kilauea East Rift Zone eruption. Credit: USGS, N. Deligne Enhancing risk preparedness

“Hawaii communities live alongside active volcanoes and face significant seismic risks,” Young said. “This research enhances risk preparedness and reinforces the University of Hawaii’s commitment to advancing science for the safety and well-being of Hawaii’s people and ecosystems by highlighting important past events.”

The history of Kīlauea provides invaluable insights into the complex relationships between magmatic processes and earthquake cycles. Building on this foundation, Young and her team plan to improve their models by delving deeper into key properties of Kilauea's structural features, such as friction along fault planes, to better understand how stress changes trigger seismic and magmatic activity.

More information: Lauren Ward Yong et al, A Century of Deformation and Stress Change in Décollement Kīlauea, Journal of Geophysical Research: Solid Earth (2024). doi: 10.1029/2024JB028714

Provided by the University of Hawaii at Manoa

Citation: Unveiling a Century of Stress and Deformation: Insights from the 1975 Kilauea Volcano Earthquake (2024, December 2) Retrieved December 2, 2024 from https://phys.org/news/2024-12-unveiling-century-stress-deformation -insights.html

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