The 2018 Kilauea earthquake may have halted the fault’s slow slide for decades

A 6.9-magnitude earthquake that occurred in 2018 on the south side of Kilauea on the island of Hawaii may have halted episodes of periodic slow slip along a large fault underlying the volcano, according to a new study by scientists at the U.S. Geological Survey.

Since rupture, slow-slip events have ceased on this part of the fault, and it could take nearly 60 years to reconstruct the amount of stress released during the earthquake on these slow-slip spots, the researchers report in the Bulletin of the Seismological Society of America.

The researchers also observed no signs of viscoelastic relaxation — that is, flow of the lower crust and upper mantle in response to stress changes — after the earthquake.

These features of the 2018 earthquake could be useful for understanding and assessing earthquake risk in this part of Kilauea, said Ingrid Johansson and colleagues from the USGS Hawaiian Volcano Observatory.

The May 4, 2018 earthquake occurred amid a massive eruption in the volcano’s eastern rift zone. The earthquake ruptured part of Kilauea’s rift fault, where the volcanic mound meets underlying oceanic crust.

The area is densely equipped with Global Navigation Satellite System (GNSS) stations, which measure changes in ground levels to form a comprehensive picture of how the Earth’s crust moves and deforms before, during and after earthquakes and volcanic eruptions.

Johansson and his colleagues used this data to look at where fault slip occurred during and after the earthquake, and to compare it to slip zones from previous earthquakes and past slow slip events. Compared to the sudden rupture of an earthquake, slow seismic events can release energy over weeks and months.

The 2018 earthquake erupted across patches of fault where slow-slip events have occurred fairly regularly over the past two decades. But these events have not been observed since the 2018 earthquake.

The researchers estimate that the quake may have released nearly 60 years of built-up stress along the fault in these spots, and that the resulting “stress shadow” may prevent these events from happening again for decades.

“Assuming constant loading from creep fault, we calculate this [the slow slip fault regions] “It can remain under stress for 56 years, plus or minus 3 years,” Johansson said.

“However, loading on the fault is closely related to volcanic activity, so a change in volcanic activity could push the fault to emerge from the stress shadow early, and we should not rule out the possibility of continuous rupture at the same location during the projected 56 years,” she added.

One of the events the researchers hoped to study during the 2018 event was post-earthquake viscoelastic relaxation, which provides a unique opportunity to observe deformation of the crust and mantle, they noted.

“Although the 2018 earthquake occurred during the first week of the historic eruption and collapse of the caldera and one day after lava first erupted from a fissure in Leilani Estates, it was a priority to capture the post-earthquake deformation pattern and ensure additional parts of the pavilion were prepared,” Johansson said.

However, Johansson and colleagues found minimal slip on the fault and no signs of viscoelastic deformation.

It’s possible that the fault dip is so shallow that it remains within the brittle upper part of the crust and may not transfer stress to the lower crust and upper mantle to cause deformation, the researchers say.

“Given its rupture zone, it is likely that the 7.7 magnitude Kalapana earthquake in 1975 also remained in the fragile part of the Earth’s crust, as will be the case with future events in this size class,” Johansson said. “However, the 1868 magnitude 7.9 Great Kai Earthquake supposedly ruptured the jaw area all the way below Mauna Loa. If another rupture occurred at that depth, it could put enough stress on the lower crust to generate a rupture.” [viscoelastic] answer.”

The 2018 earthquake originated in the same part of the fault as the 1975 Kalapana earthquake and other historic earthquakes on the southern side of the Kilauea region. Magma seeping through this part of the fault is likely responsible for these previous earthquakes, as this appears to be the case for the 2018 quake.

“This underscores that monitoring volcanic activity is key to understanding pressure buildup and seismic activity on Kilauea’s southern flank, and highlights how magmatic and tectonic processes are connected in Hawaii,” Johansson said.

magazine

Bulletin of the Seismological Society of America

Search method

Observational study

Research topic

Not applicable

Article title

Rupture in a slow-slip fault system during the 2018 6.9 Hawaii Island earthquake followed by modest post-earthquake slip.

Date the article was published

3-February-2026

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