A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis

Regional and Local Patterns of Upper‐Plate Deformation in Cascadia: The Importance of the Down‐Dip Extent of Locking Relative to Upper‐Plate Strength Contrasts

“…Wang et al., 2013). The occurrence of both margin‐wide and local ruptures (Kelsey et al., 2005; Nelson et al., 2021) and the segmentation of rupture during the 1700 event (Wang et al., 2013), is compatible with the coupling heterogeneity we find across the margin. To first order, the location of coupling sub‐regions we infer in our model (Figure 8) correspond to the asperities found for the 1700 event (P.‐L.…”

“…The area of coupling in central Cascadia (from ∼43°N to the ∼47°N), assuming either one or all of the northern locked sub‐regions in our model rupture with a recurrence interval of 400 years (consistent with Nelson et al. (2021)), has the potential to host ∼Mw 8.4–Mw 8.9 megathrust events. If the entire interface modeled here (from the MTJ to 47°N) were to rupture, assuming a 500‐year interval between these margin‐wide events (e.g., Atwater & Hemphill‐Haley, 1997; Kelsey et al., 2005) and continuous slip deficit accumulation, our results suggest Cascadia could host a ∼Mw 9.6 earthquake.…”

“…Paleo‐seismic records including stratigraphic evidence for co‐seismic vertical motions and tsunami inundation including radiocarbon dating of buried organic matter (e.g., Atwater et al., 2004; Kelsey et al., 2005; Nelson et al., 2006; 2021; Priest et al., 2017; Witter et al., 2012, 2013) across Cascadia have been used to estimate the rupture extent of historic Cascadia megathrust events (Kemp et al., 2018; Li & Liu, 2021; Nelson et al., 2021; P.‐L. Wang et al., 2013).…”

“…Paleo-seismic records including stratigraphic evidence for co-seismic vertical motions and tsunami inundation including radiocarbon dating of buried organic matter (e.g., Atwater et al, 2004;Kelsey et al, 2005;Nelson et al, 2006;Priest et al, 2017;Witter et al, 2012Witter et al, , 2013 across Cascadia have been used to estimate the rupture extent of historic Cascadia megathrust events (Kemp et al, 2018;Li & Liu, 2021;Nelson et al, 2021;P.-L. Wang et al, 2013). Evidence from Bradley Lake (e.g., Kelsey et al, 2005) implies that Cascadia can rupture in margin-scale ∼Mw 9.0 ruptures but can also host independent local-scale ∼Mw 8.0 ruptures.…”

Portable optically stimulated luminescence age map of a paleoseismic exposure

“…Radiocarbon ( 14 C) and luminescence ages provide geochronological context to paleoseismic investigations; constrain the timing and rates of sedimentary, pedogenic, and geomorphic processes; and provide the basis for quantifying earthquake timing, recurrence, and fault slip rate (e.g., Weldon et al, 2004;Dolan et al, 2016;Galli et al, 2019;Scharer and Yule, 2020;Nelson et al, 2021). However, substantial uncertainties in these dating methods relate to the depositional and geomorphic setting of the paleoseismic site and the dominant processes of sediment transport and accumulation, pre-depositional age inheritance, and post-depositional modification and soil development that may vary spatially and temporally and in relation to surface ruptures.…”