Fault frictional parameters and material properties revealed by slow slip events at Kilauea volcano, Hawai‘i

Abstract

We categorize slow slip events at Kilauea Volcano into two distinct families based on GPS measurements of the surface displacement patterns. An event correlation filter confirms that “eastern” and “western” families are statistically distinguishable, with the western family notably self‐similar. The western family exhibits quasi‐periodicity with regular repeat times, while eastern family events are aperiodic or have complicated periodicity. If the decollement is the source fault for both families of events, it must have varying frictional properties at the ~10 km scale of separation. The temporal slip and spatial scaling behavior are consistent with a simplistic rate‐ and state‐dependent frictional formalism provided that the characteristic slip distance for state evolution, Dc, is of the order of millimeters rather than the 10–100 µm typically found in lab studies, and the shear rigidity is around 2 GPa, consistent with fault gouge material.

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

“…Yellow rectangle outlines the 1989 M 6.1 rupture area (Hooper et al, ). The black contour lines show the source area of Mw ~5.4–5.8 slow slip events (Foster et al, ).…”

Effect of pore pressure buildup on slowness of rupture propagation

“…The effective normal stress σ eff exerts important controls on the shear strength and physical properties in rocks [e.g., Jaeger et al , ; Foster et al , ]: where σ n is the normal stress, α is a poroelastic parameter, and P f is the pore fluid pressure [ Rice and Cleary , ]. For shear strength, α is ~1.…”

The Rupture Process of the 2018 Mw 6.9 Hawaiʻi Earthquake as Imaged by a Genetic Algorithm‐Based Back‐Projection Technique

“…This segment occurs 5–10 km offshore where both background seismicity and aftershocks are sparse (Figure a). In addition, this region of the décollement experiences slow slip events (Brooks et al, ; Foster et al, ; Montgomery‐Brown et al, , ; Poland et al, ; Segall et al, ; Syracuse et al, ). Modeling results have shown that the failure of velocity‐weakening patches with dimensions close to the critical nucleation dimension can produce these slow slip events (Kato, ).…”

“…The location of Segment 4 would also suggest that stress accumulation on the décollement is not completely relieved by the slow slip events. The path of Segment 4 is near the boundary between patches of periodic and aperiodic slow slip behavior (Foster et al, ). If this boundary region represents a zone of reduced slow slip between the northern and southern slow slip patches (Figure a), then one would expect a high rate of stress accumulation in the absence of stable sliding, possibly explaining the propagation of this rupture into this region.…”