Earthquakes triggered by silent slip events on Kīlauea volcano, Hawaii

Abstract

Slow-slip events, or 'silent earthquakes', have recently been discovered in a number of subduction zones including the Nankai trough in Japan, Cascadia, and Guerrero in Mexico, but the depths of these events have been difficult to determine from surface deformation measurements. Although it is assumed that these silent earthquakes are located along the plate megathrust, this has not been proved. Slow slip in some subduction zones is associated with non-volcanic tremor, but tremor is difficult to locate and may be distributed over a broad depth range. Except for some events on the San Andreas fault, slow-slip events have not yet been associated with high-frequency earthquakes, which are easily located. Here we report on swarms of high-frequency earthquakes that accompany otherwise silent slips on Kīlauea volcano, Hawaii. For the most energetic event, in January 2005, the slow slip began before the increase in seismicity. The temporal evolution of earthquakes is well explained by increased stressing caused by slow slip, implying that the earthquakes are triggered. The earthquakes, located at depths of 7-8 km, constrain the slow slip to be at comparable depths, because they must fall in zones of positive Coulomb stress change. Triggered earthquakes accompanying slow-slip events elsewhere might go undetected if background seismicity rates are low. Detection of such events would help constrain the depth of slow slip, and could lead to a method for quantifying the increased hazard during slow-slip events, because triggered events have the potential to grow into destructive earthquakes.

Scaling Relationships of Source Parameters for Slow Slip Events

“…Slow slip events, which represent the transient release of strain over the duration of days toweeks, occur downdip of the transition zone between the locked seismogenic zone and the free-slipping zone on the plate interface, and fluids are thought to be critical for its occurrence (e.g., Obara, 2002;Rogers and Dragert, 2003). Slow earthquakes have also been reported in other tectonic environments such as the San Andreas fault (Linde et al, 1996) and Hawaii (Segall et al, 2006;Montgomery-Brown et al, 2009). Although several hypotheses have been proposed to explain these events (e.g., Ito et al, 2007;Schwartz and Rokosky, 2007;Brodsky and Mori, 2007;Ide, 2008;Liu and Rice, 2009;Ando et al, 2010;Hawthorne and Rubin, 2010;Ide, 2010;Liu and Rubin, 2010;Peng and Gomberg, 2010;Shibazaki et al, 2010), the physical mechanisms are still not fully understood.…”

“…There are two sources for the dataset used in this study: source parameters inferred directly from the slip distributions of Schmidt and Gao (2010) for the Cascadia subduction zone and source parameters reported in the literature for other subduction zones (e.g., Obara et al, 2004;Brown et al, 2005;Douglas et al, 2005;Hirose and Obara, 2005;Wallace and Beavan, 2006;Ito and Obara, 2006;Hirose and Obara, 2006;CorreaMora et al, 2008CorreaMora et al, , 2009Hirose and Obara, 2010;Sekine et al, 2010; see references in Ⓔ Table S1, available in the electronic supplement to this paper). Additionally, we also include documented aseismic slip on the San Andreas fault (Linde et al, 1996) and Hawaii's south rift zone (Segall et al, 2006;Montgomery-Brown et al, 2009). In this study, we attempt to focus on a specific type of slow slip phenomenon in order to ensure that we are studying a consistent underlying process.…”

An Overview of Geodetic Volcano Research in the Canary Islands

“…The smoothness and spatial distribution of our geodetic results (Figure 14) suggests that the detachment fault is slow stablesliding at depth beneath the western flank of the edifice in the on-and offshore region close to the shoreline, on a fault segment with creeping friction properties. This behaviour is likely steadystate, or might be punctuated by unobserved slow-slip events, in the transition zone between 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 frictionally different segments of the developing fault surfaces (Brooks et al, 2006;Segall et al, 2006). Only during eruptions, the slip assumption of homogeneity can be accepted.…”

Statistic analysis of swarm activities around the Boso Peninsula, Japan: Slow slip events beneath Tokyo Bay?

“…Slow slip events, SSE, are another kind of the swarm driving mechanism. Recently, SSE induced swarms have been discovered in various geological environments, such as near the San Andreas Fault, California (Lohman and McGuire, 2007), beneath Kilauea volcano (Montgomery-Brown et al, 2008), Hawaii (Segall et al, 2006), and in subduction zones in Japan (Ozawa et al, 2007;NIED, 2007) and New Zealand (Reyners and Bannister, 2007).…”