Valerie Locher, Rebecca E. Bell, Parastoo Salah, Robert Platt, Cédric M. John

Giant earthquakes (MW ≥ 8.5) along subduction margins pose great hazards to coastal societies. While it is generally accepted that geological margin properties play a role, the controls on giant earthquake occurrence remain undetermined. Their long intermittence times and the comparatively short earthquake record obscure any correlations between margin properties and seismicity.
This work presents a new approach to relating margin properties to seismicity. We apply Principal Component Analysis (PCA) to a set of margin properties to “fingerprint” margins by assigning them a PCA profile, which we compare to giant earthquake occurrence . This approach reduces bias from the short earthquake record as seismicity is not used as a PCA input feature. Using Kernel-PCA, a non-linear PCA variant, we uncover non-linear patterns in margin properties, and suggest that links between these properties and seismicity are non-linear., which helps explain why they have previously been hard to establish.
PCA clusters identify “active and moderate” and “quiet and extreme” margins (following Ide, 2013). We argue that margin segments with “quiet and extreme” PCA profiles, but no giant earthquakes since 1900, should be considered as hazardous as those that have ruptured in giant earthquakes recently.