Establishing the Inundation Distance and Overtopping Height of Paleotsunami from the Late-Holocene Geologic Record at Open-Coastal Wetland Sites, Central Cascadia Margin

Abstract

are tested by marine diatom and bromine anomalies. These tracers are being used to extend paleotsunami flooding records to include low-velocity inundation distances.

Distribution and sedimentary characteristics of tsunami deposits along the Cascadia margin of western North America

“…Witter and Kelsey, 1996;Hutchinson et al, 2000). Plant detritus may also be disseminated throughout the deposit (Schlichting, 2000). At Kanim Lake, plant material coarsens and increases in abundance towards the base of the deposit .…”

“…This is not true run-up because it does not occur at maximum inundation but does give an indication of elevations reached by the tsunami. The maximum barrier elevation overtopped by a Cascadia tsunami is 8 m at Long beach Peninsula, Washington (Schlichting, 2000). Coastal uplift or subsidence that occurred during the time between deposition and elevation measurements of the deposit or barrier may have a significant effect on run-up determinations from paleotsunami deposits.…”

“…On Long Beach Peninsula, Washington, erosional scarps in barrier dunes, delineated using groundpenetrating radar, were used in conjunction with estimates of coseismic subsidence to estimate paleoshorelines (Schlichting, 2000). The maximum inland extent of deposits from the 1700 tsunami was 800 m from the present shoreline but 300 m from a subsurface erosional scarp interpreted as the paleoshoreline.…”

“…The maximum inland extent of deposits from the 1700 tsunami was 800 m from the present shoreline but 300 m from a subsurface erosional scarp interpreted as the paleoshoreline. (Schlichting, 2000;Peterson et al, 2002). The distance from the modern shoreline to the maximum inland extent of deposits from an event that occurred 1100 years ago was 1500 m from the present shoreline and 1000 m from the erosional scarp correlated with the paleoshoreline at the time of this event (Schlichting, 2000).…”

Sediment characterisation of the 26 December 2004 Indian ocean tsunami in Andaman group of islands, bay of Bengal, India

“…For example, in Cascade, paleotsunami deposits are identified as being anomalous sand layers in low energy marsh or lacustrine environments (Atwater 1987;Clague et al 2000). There is additional information which indicates a seaward source of sediments, such as microfossils (Hemphill-Haley 1995a; or geochemical signature (Schlichting 2000), which also useful for determining that a deposit was formed by a tsunami. Generally tsunamis are classified into three categories, distant (>750 km from the source), regionals (100-750 km from the source), and local (<100 km from the source).…”