FLANK SPREADING AT KĪLAUEA LEADS TO PERIODIC DIKE INTRUSIONS: A TEMPLATE FOR OTHER RIFT ZONES?

Intrusions are common in east rift zone of Kīlauea Volcano. These intrusions often occur as 5-10 km long planar dikes that extend from depths of 2-3 km up to the surface, and sometimes erupt as fissures. Between 1983 and 2018, dikes in Kīlauea’s upper and middle East Rift Zone (ERZ) repeatedly affected the same segments of the rift and intruded at regular intervals of ∼8 (upper ERZ) or ∼14 yr (middle ERZ). The interval between intrusions correlates with the slip rate of the adjacent mobile flank, and failure (intrusion) occurs when the shallow rift accumulates ~1-5 MPa of tension. Kīlauea’s active magmatic system also has the potential to influence the recurrence of dikes, but the occurrence of intrusions was neither advanced nor delayed during magma supply variations -- for example during a magma supply surge between 2003 and 2007. The 2018 fissure eruption occurred in an area of the volcano that had not erupted since 1955. This lower ERZ eruption site is about 40 km east of the summit magma system and is also adjacent to a part of the mobile flank that slides at a slower rate than regions closer to the summit. Although the rates of flank sliding and tensional stress accumulation in the shallow rift were both lower than in the upper parts of the rift zone, flank sliding models suggest that a similar magnitude of tension (~1-5 MPa) accumulated in the lower ERZ between the 1955 and 2018 eruptions. This work highlights the importance of including both intrusive and extrusive activity in rift eruption hazard analyses. It also suggests that dike occurrence at other rift zones, and more generally at rifting plate boundaries, may be influenced by the tectonic extensional processes.