Preliminary Event Detection of Earthquakes Using the Cascadia Initiative Data

Abstract

Online Material: Table of station locations. Along the northwestern coast of North America, the Cascadia subduction zone (CSZ) produces a range of slip behavior along the plate boundary megathrust zone, from great earthquakes to episodic slow slip and tremor downdip of the seismogenic zone (e.g., Ghosh et al. , 2010, 2012; McCausland et al. , 2010; Beroza and Ide, 2011; Wech and Creager, 2011; Ide, 2012). At the CSZ, the Juan de Fuca plate subducts beneath the North American plate at ∼2.5–4 cm/yr (Fig. 1) (e.g., McCaffrey et al. , 2007). Figure 1. Tectonic setting of Cascadia subduction zone (CSZ), highlighted by the box in the inset figure. The Juan de Fuca, Gorda, and Explorer plates (labeled JdF, GP, and Expl., respectively) subduct beneath the North American plate. Convergence vectors from McCaffrey et al. (2007) are shown at various locations along the boundary. Estuarine evidence for coseismic subsidence and tsunami inundation, as well as deep‐sea turbidites as indicators of earthquake shaking, suggest that multiple great earthquakes have occurred, both as partial and full ruptures of the entire margin (e.g., Satake and Atwater, 2007; Williams et al. , 2011; Goldfinger et al. , 2012). It is estimated that 18 ruptures have occurred in the last 9800 yrs (Goldfinger et al. , 2003). These events have an average recurrence interval of 600 yrs, with the individual intervals ranging from 215 to 1488 yrs (Goldfinger et al. , 2003). The most recent great rupture, constrained by the orphan tsunami in Japan and tree‐ring data, occurred in 1700 (e.g., Satake et al. , 1996; Satake and Atwater, 2007). Tsunami simulations of the event indicate the entire along‐strike extent of the CSZ ruptured in an earthquake of M w 8.7–9.2, with 600–1000 km of the coast dropping 1–2 m below sea (e.g., Satake et al. , 1996, 2003; Goldfinger et al. , 2003 …