Physically consistent modeling of dike induced deformation and seismicity: Application to the 2014 Bárðarbunga dike, Iceland

Abstract

Dike intrusions are often associated with surface deformation and propagating swarms of earthquakes. These are understood to be manifestations of the same underlying physical process, although rarely modeled as such. We construct a physics-based model of the 2014 B\'ar{\dh}arbunga dike, by far the best observed large dike ($> 0.5$ km$^3$) to date. We constrain the background stress state by the total dike deformation, the time-dependent dike pressure from continuous GPS and the extent of the seismic swarm, and the spatial dependence of frictional properties via the space-time evolution of seismicity. We find that the geodetic and earthquake data can be reconciled with a self-consistent set of parameters. The complex spatial and temporal evolution of the B\'ar{\dh}arbunga seismicity can be explained by dike-induced elastic stress changes on preexisting faults, constrained by observed focal mechanisms. In particular, the model captures the segmentation of seismicity, where only the newest dike segment is seismically active. Our results indicate that many features of the seismicity result from the interplay between time-dependent magma pressure within the dike and stress memory effects. The spatial variability in seismicity requires heterogeneity in frictional properties and/or local initial stresses. Modeling suggests that the dike pressure drops during rapid advances and increases during pauses, which primarily causes the segmentation of the seismicity. Joint analysis of multiple data types could potentially lead to improved, physics-based eruption forecasts.

Volcanic Origin of a Long‐Lived Swarm in the Central Bransfield Basin, Antarctica

“…The seismicity can also result from local increment of pore fluid pressure (Sibson, 2000). This long‐lasting volcanic activity is responsible for the significant deformation inferred from GNSS observations, while seismicity is a by‐product of the magmatic activity (Heimisson & Segall, 2020), mainly occurring in limited areas with brittle characteristics and accumulation of stress (Hill, 1977). Our study also illustrates that, beyond the continuous 7 mm/yr extension (Taylor et al., 2008) between the Antarctica Plate and the South Shetland microplate, rapid deformation episodes occurring at the ridge axial volcanic structures plays a main role in modulating the long‐term extension.…”

Aseismic Deformation During the 2014 Mw 5.2 Karonga Earthquake, Malawi, From Satellite Interferometry and Earthquake Source Mechanisms

“…Throughout dike emplacement and surface breach, the seismicity remained at 5‐ to 7‐km depth (Ágústsdóttir et al., 2016), corresponding to around the base of the modeled dike. Meanwhile, the dike opening (maximum at <3‐km depth) occurred aseismically (e.g., Heimisson & Segall, 2020; Woods et al., 2019), indicating the role of shallow, weak crust in accommodating aseismic deformation. In the absence of magmatism, the shallow weakened zones are probably similar to the brittle and fractured limestone units in the upper crust of the L'Aquila fault, where foreshocks and aftershocks to the 2009 M w 6.0 mainshock outlined multiple secondary synthetic and antithetic faults (Chiaraluce et al., 2011).…”

Logarithmic Growth of Dikes From a Depressurizing Magma Chamber

“…A propagating dike typically triggers a propagating swarm of seismicity near the dike tip, which can be inferred from joint interpretation of seismic and geodetic data (Heimisson & Segall, ; Sigmundsson et al, ). Particularly strong evidence for this relationship was established when the seismic swarm of the September 1977 Krafla dike (purple, Figure b) reached the location of a geothermal borehole (Brandsdóttir & Einarsson, ) and a small eruption was produced from the borehole (Larsen & Grönvold, ), thus directly demonstrating the collocation of the advancing seismicity and magma.…”