The Role of Holocene Relative Sea-Level Change in Preserving Records of Subduction Zone Earthquakes

Eustasy and glacio- and hydro-isostatic adjustment are the main drivers of regional variability of Holocene relative sea-level (RSL) records. These regional variations in Holocene RSL influence the preservation of coastal wetland stratigraphic records of prehistoric earthquakes along subduction zone coasts. The length and completeness of prehistoric earthquake records is intrinsically linked to the accommodation space provided by gradually rising (<3 mm/year) Holocene RSL. In near-field regions that were located beneath northern hemisphere ice sheets (e.g., western Vancouver Island), RSL fall from a mid-Holocene highstand has limited prehistoric earthquake records to the last 1 ka. In intermediate field regions (e.g., southern Washington and central Oregon), gradual RSL rise over the last ∼7 ka has preserved widespread records of prehistoric earthquakes. In far-field regions (e.g., Sumatra, Chile, and Japan), fragmentary stratigraphic evidence of prehistoric earthquakes has been preserved only during periods of gradual RSL rise prior to a mid-Holocene highstand, or during the last 1–3 ka, when RSL was within 2 m of modern sea level, and thus within the tidal frame.