Emily K. Desmarais | Search USGS

USGS2006

Earthquakes triggered by silent slip events on Kīlauea volcano, Hawaii

Slow-slip events, or ‘silent earthquakes’, have recently been discovered in a number of subduction zones including the Nankai trough 1, 2, 3 in Japan, Cascadia 4, 5 , and Guerrero 6 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 7, 8 , but tremor is difficult to locate and may be distributed over a broad depth range 9 . Except for some events on the San Andreas fault 10 , 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 K ī lauea 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.

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USGS2006

Corrigendum: Earthquakes triggered by silent slip events on Kīlauea volcano, Hawaii

There was a plotting error in Fig. 1 that inadvertently displays earthquakes for the incorrect time interval. The location of earthquakes during the two-day-long slow-slip event of January 2005 are shown here in the corrected Fig. 1 . Because the incorrect locations were also used in the Coulomb stress-change (CSC) calculation, the error could potentially have biased our interpretation of the depth of the slow-slip event, although in fact it did not. Because nearly all of the earthquakes, both background and triggered, are landward of the slow-slip event and at similar depths (6.5–8.5 km), the impact on the CSC calculations is negligible ( Fig. 2 ; compare with Fig. 4 in original paper). The error does not alter our conclusion that the triggered events during the January 2005 slow-slip event were located on a subhorizontal plane at a depth of 7.5 1 km. This is therefore the most likely depth of the slow-slip events. We thank Cecily J. Wolfe for pointing out the error in the original Fig. 1 .

Hawai'i↗