High-frequency Seismic Signals in Antarctica Triggered by the 2010 Mw8.8 Maule, Chile Earthquake

Passing seismic waves from distant, large earthquakes are known to nearly instantaneously trigger shallow microearthquakes and deep tectonic tremor. Remotely triggered seismic activity mostly occurs in tectonically active regions, and is generally considered to represent shear failure on critically stressed fault planes. Here we conduct a systematic search of triggered seismic activity in Antarctica following the 2010 Mw 8.8 Maule, Chile earthquake. We apply a 5 Hz high-pass filter to broadband seismograms recorded by both permanent and temporary networks, and identify high-frequency (~5 - 20 Hz) events during large-amplitude teleseismic waves. We use an automatic picking algorithm to detect all possible bursts that occurred within 6 hours before and after the Maule mainshock. We then compute a statistical parameter that measures pre- and post-trigger activity, to confirm the triggering significance. We also visually examine the records to rule out the possibility that high-frequency signals could be caused by clipping, steps or other nonlinear instrumental noise. Out of the 42 Antarctic stations examined, 14 show statistically significant increase of high-frequency seismic signals during the surface wave arrivals. Most of the high-frequency signals occurred during and immediately after the long-period Rayleigh waves. The triggered events show diverse patterns, including very short duration high frequency bursts and relatively long duration tremor-like signals. The best triggering signal is recorded at POLENET station HOWD located near the Howard Nunataks. Burst-like seismic signals were principally associated with volumetric strain changes caused by the arrival of compressional P and the Rayleigh surface waves, suggesting that these events may be triggered by the dynamic opening of cracks. Although we were unable to locate these triggered events with single station recordings, polarization analysis revealed that those events likely occurred with 1-2 km of the station, at a shallow incidence angle plausibly indicative of surface crevassing. A more exhaustive study of this phenomenon for other large earthquakes and in other polar regions may yield important information regarding the stress state of glacier systems and potential interaction between tectonic and glacier systems.