Triggered Seismic Events along the Eastern Denali Fault in Northwest Canada Following the 2012 Mw 7.8 Haida Gwaii, 2013 Mw 7.5 Craig, and Two Mw>8.5 Teleseismic Earthquakes

Abstract

We conduct a systematic search for remotely triggered seismic activity along the eastern Denali fault (EDF) in northwest Canada, an intraplate strike‐slip region. We examine 19 distant earthquakes recorded by nine broadband stations in the Canadian National Seismograph Network and find that the 2012 M w 7.8 Haida Gwaii and 2013 M w 7.5 Craig, Alaska, earthquakes triggered long duration (>10 s), emergent tremor‐like signals near the southeastern portion of the EDF. In both cases, tremor coincides with the peak transverse velocities, consistent with Love‐wave triggering on right‐lateral strike‐slip faults. The 2011 M w 9.0 Tohoku‐Oki and 2012 M w 8.6 Indian Ocean earthquakes possibly triggered tremor signals, although we were unable to locate those sources. In addition, we also identify many short‐duration (<5 s) bursts that were repeatedly triggered by the Rayleigh waves of the 2012 M w 7.8 Haida Gwaii earthquake. Although we were unable to precisely locate the short‐duration (<5 s) events, they appear to be radiating from the direction of the Klutlan Glacier and from a belt of shallow historical seismicity at the eastern flank of the Wrangell–St. Elias mountain range. The fact that these events were triggered solely by the Rayleigh waves suggests a different source mechanism as compared with triggered tremor observed along the EDF and other plate boundary regions. Online Material: Description of Rayleigh‐wave polarization detection; figures of spectograms, S ‐wave amplitudes, polarization analysis, and static stress changes; tables of earthquake catalogs and velocity model; and animations of tremors and bursts.