The Washington continental margin presents both a classic test of submarine paleoseismology, and an opportunity to explore advancement of the field through analysis of sediment dispersal in a heterogeneous system. New and archive core, bathymetric, backscatter and seismic reflection data from the Washington Cascadia margin show that during high-stand conditions, the northernmost canyons, Barkley, Nitinat, Juan de Fuca (JDF), and to some extent Quillayute are relict systems, with little Holocene recharge. The remaining canyons, Quinault, Grays, Guide, and Willapa, are recharged to a varying degrees by northward transport of Columbia River derived sediment. All systems are nonetheless active conduits for turbidity currents during the Holocene, which are weaker and more restricted than their Pleistocene counterparts. Sedimentologic and CT analysis, supported by radiocarbon ages, micropaleontology, and the Mazama ash datum show that the Holocene sedimentary sequence consists of a series of sand to mud turbidites in the active portions of all systems, interbedded with hemipelagic sediment. However, the Pleistocene Astoria and Nitinat fans are largely inactive in the Holocene, with turbidity current activity limited to the proximal parts of the main channels. Within active systems, the turbidite record is modulated by local landsliding and growth of active folds and faults. In the relict systems, the turbidite record begins in the middle canyon reaches, as opposed to the actively recharged systems which have a turbidite record in the more proximal canyon reaches. Deposits in the relict systems increase in thickness and modal grain size downstream, suggesting multiple sources and or entrainment of material along the canyon walls. Hydrodynamic models using Monte Carlo model searches for best fitting flow parameters show the most likely pathways by which Holocene and Pleistocene currents flowed through the complex accretionary wedge to the abyssal plain. Model results, supported by heavy mineral distributions, show that the northern canyon systems (Barkley, Nitinat, JDF, Quillayute) are independent of the southern systems, (Quinault, Guide, Grays, Willapa) during the Holocene, supporting the classic "confluence test". Balancing of sediment volumes required suggests sediment supplied to the slope canyons and abyssal channels in turbidity current events is 2-5 times greater than that supplied by recharge to the canyon heads by external sources. This implies a process that is independent of recharge that scavenges the plentiful relict and hemipelagic sediment supply on the continental slope. Lithostratigraphic correlation and age models suggest similar sequences were deposited in most systems independently, and likely synchronously. The correlated turbidite sequence suggests deposition of similar to 23 Holocene and 16 post Mazama turbidites in most parts of the canyon systems, with only modest variation, mostly attributable to evidence of bypassing and erosion. The best candidate for triggering of these sequences remains great earthquakes, and the sequence correlates well to onshore and other offshore paleoseismologic evidence. The new data, including new cores in northern Oregon, suggest revisions to segmented rupture boundaries. Several partial ruptures (Segment B) likely extended further north to Juan de Fuca Canyon; one event was resolved into two, and one Washington only event was added. Most "Segment C" ruptures were found to extend further northward to the latitude of Astoria Canyon. Mean recurrence times are therefore revised to similar to 434 years for the Washington Coast, and similar to 340 years for the central and northern Oregon coast. Conditional probabilities in the next 50 years also are revised to 10-17% for the Washington coast, and 16-22% for the central and northern Oregon coast. In Cascadia, Sumatra and other locales globally, core siting, spatial sample density, high-resolution analysis of core and regional geophysics and understanding of flow dynamics are critical to capturing a paleoseismic record. Sedimentary records vary across turbidity current systems of varying sediment supply, physiography and sediment sources. Variations in the record will reflect these factors, yet may still present a consistent paleoseismic history. This analysis highlights the importance of a thorough understanding of flow paths, hydrodynamics and the interplay of sedimentation and local tectonics when testing for evidence of earthquakes in the sedimentary record of active margins. (C) 2016 Elsevier B.V. All rights reserved.