Triggering of the Mw 7.2 Hawaii Earthquake of 4 May 2018 by a Dike Intrusion

Abstract

A Mw 7.2 earthquake struck the south flank of Kilauea, Hawaii, on 4 May 2018, following a period of volcanic unrest. To investigate its relationship with the stress changes induced by prior tectonic and magmatic activity, we model the coseismic slip distribution, preintrusion deformation, and dike intrusion using geodetic, seismic, and tsunami observations. The décollement beneath the south flank was creeping seaward by ~25 cm/year. Diking started on 20 April and led to fissure eruption on 3 May. The magmatic activity and creep resulted in an onshore U‐shaped zone of stress unloading, fringed by an off‐shore zone of stress buildup that apparently guided the 2018 rupture. It takes only 20 to 35 years at the preintrusion rate to accumulate a moment deficit equivalent to the moment that was released in 2018. This event falls short of balancing the moment budget since the 1975 Mw 7.7 earthquake.

The cascading origin of the 2018 Kīlauea eruption and implications for future forecasting

“…An open question regards the role of the May 4 M w 6.9 south flank earthquake in influencing the magnitude of the LERZ eruption. The timing of the earthquake, days after the onset of magma moving into the LERZ 70 , suggests that the intrusion triggered the earthquake by stressing the south flank 37 , as proposed for previous episodes where rift zone intrusions apparently induced strong south flank earthquakes 47 . Did the M w 6.9 earthquake dilate the ERZ and enable higher rates of magma transport?…”

“…1b), imparting extensional stresses on the rift zones and facilitating rift zone magma transport, dike intrusions, and fissure eruptions [30][31][32][33][34] . Likewise, magma injected into the rift zones can produce stresses that trigger south flank motion and earthquakes [33][34][35][36][37] . Thus, the tectonics of the volcano's south flank are tightly coupled with the magmatic system of the ERZ 27,38,39 .…”

“…1a)the largest earthquake in Hawaiʻi in 43 years. The earthquake involved southward displacement of the mobile flank and is thought to be a consequence of stress induced by the ERZ injection 37 . Throughout May, 24 short-lived fissures developed in the LERZ, but activity focused on fissure 8 by the end of that month (Fig.…”

Dyke intrusion and stress-induced collapse of volcano flanks: The example of the 2018 event at Mt. Etna (Sicily, Italy)

“…Earthquake and volcanoes are expression of dramatic changes in the dynamics of the earth interior, connected at a scale that ranges from plate tectonics to local 1,2 . The relation between magmatic intrusions, flank collapses and earthquakes is still an open issue, although evidences at paradigmatic giant strato-volcanoes are progressively elucidating some main aspects [3][4][5][6] .…”

Seismic Evidence for a Shallow Detachment Beneath Kīlauea's South Flank During the 2018 Activity

“…Recent studies have revealed that the 2018 Mw 6.9 earthquake is a thrust event and shares some similar characteristics with the 1975 Mw 7.7 Kalapana earthquake (Bai et al, 2018;Chen et al, 2019;Kehoe et al, 2019;Lay et al, 2018;Liu et al, 2018). Although the 1975 Kalapana earthquake has been attributed to the basal décollement (Owen et al, 1995), it has been argued that additional slip is needed on the Hilina fault to explain ground deformation associated with the earthquake (Cannon et al, 2001).…”