Kilauea's slow earthquakes studied by SOEST researchers

University of Hawaiʻi at Mānoa
Ben Brooks, (808) 956-7864
School of Ocean and Earth Science and Technology
Posted: Jun 26, 2006

HONOLULU — Kilauea volcano‘s mobile south flank periodically experiences "slow earthquakes"—anomalous earthquakes that are too slow to generate damaging shaking or to be felt by Hawaiʻi‘s residents—according to a study published in the June 30 issue of Earth and Planetary Science Letters.

A team led by Assistant Researcher Ben Brooks of the School of Ocean and Earth Science and Technology (SOEST) at the University of Hawaiʻi at Mānoa used surface motion data from a Global Positioning System network partnership between UH, the USGS Hawaiian Volcano Observatory (HVO), Stanford University, and the Center for the Study of Active Volcanoes, whose daily operations are overseen by HVO. The team identified three new slow earthquakes at the portion of Kilauea‘s southeast flank known as the ʻHilina Slump‘—a massive submarine landslide that moves oceanward at average rates of 6-10 cm per year. Along with a fourth previously recognized event, the slow earthquakes have equivalent magnitudes between 5.5-5.8, and since 1998, they have periodically occurred every 25.5 months.

In addition to helping to understand the mechanical conditions in which earthquakes may or may not occur, the new observations have important implications for characterizing tsunami hazards in the Hawaiian islands and throughout the Pacific Basin. Catastrophic failure of the submarine landslides comprising the steep flanks of ocean island volcanoes, such as those in Hawaiʻi, are little understood but a potentially devastating source of tsunami.

"It‘s not clear yet whether these slow earthquakes make the Hilina Slump more or less likely to fail catastrophically," says Brooks. "We still must be able to answer some fundamental questions about their occurrence such as ʻat what depth do they occur?‘ and ʻhow does the deformation we observe onshore translate to the offshore portion of the slump?‘"

To this end, Brooks and colleagues from Woods Hole Oceanographic Institute and Scripps Institute of Oceanography have begun to attempt to measure surface motions of the seafloor itself.

"Getting accurate measurements on the seafloor is a much bigger logistical challenge that requires some technological development," says Brooks. "But we‘re getting there and hopefully soon we‘ll be able to shed much more light on the whole process of volcano flank collapse and slow earthquakes."

Other researchers involved in the study are James Foster, Neil Frazer, and Cecily Wolfe of SOEST (UH Mānoa); Michael Bevis of Ohio State University; and Mark Behn of the Woods Hole Oceanographic Institution.

About the School of Ocean and Earth Science and Technology, University of Hawaiʻi at Mānoa

The School of Ocean and Earth Science and Technology (SOEST) was established by the Board of Regents of the University of Hawaiʻi in 1988. SOEST brings together in a single focused ocean, earth sciences and technology group, some of the nation‘s highest quality academic departments, research institutes, federal cooperative programs, and support facilities to meet challenges in the ocean and earth sciences. Scientists at SOEST are supported by both state and federal funds as they endeavor to understand the subtle and complex interrelations of the seas, the atmosphere, and the earth. For more information, visit

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