A Lack of Dynamic Triggering of Slow Slip and Tremor Indicates That the Shallow Cascadia Megathrust Offshore Vancouver Island Is Likely Locked

Jeffrey J. McGuire, John A. Collins, Earl Davis, Keir Becker, Martin Heesemann

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Great subduction zone earthquakes vary considerably in the updip extent of megathrust rupture. It is unclear if this diversity reflects variations in interseismic strain accumulation owing to the limited number of subduction zones with seafloor monitoring. We use a borehole seismic-geodetic observatory installed at the updip end of the Cascadia fault offshore Vancouver Island to show that the megathrust there does not appear to slip in triggered tremor or slow-slip events when subjected to moderate dynamic stress transients. Borehole tilt and seismic data from recent teleseismic M7.6–8.1 earthquakes demonstrate a lack of triggered slow slip above the Mw 4.0 level and an absence of triggered tremor despite shear-stress transients of 1–10 kPa that were sufficient to trigger tremor on the downdip end of the interface. Our observations are most consistent with a model in which the Cascadia fault offshore Vancouver Island is locked all the way to the trench.

Original languageEnglish (US)
JournalGeophysical Research Letters
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

tremors
slip
boreholes
subduction zone
earthquakes
borehole
earthquake
tilt
shear stress
trench
rupture
seismic data
observatories
seafloor
observatory
actuators
monitoring

Keywords

  • Cascadia subduction zone
  • seafloor geodesy
  • seismic tremor

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

A Lack of Dynamic Triggering of Slow Slip and Tremor Indicates That the Shallow Cascadia Megathrust Offshore Vancouver Island Is Likely Locked. / McGuire, Jeffrey J.; Collins, John A.; Davis, Earl; Becker, Keir; Heesemann, Martin.

In: Geophysical Research Letters, 01.01.2018.

Research output: Contribution to journalArticle

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AU - Heesemann, Martin

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