Sediment Transport Modeling Based on Geological Data for Holocene
Coastal Evolution: Wave Source Estimation of Sandy Layers on the Coast
of Hidaka, Hokkaido, Japan
Abstract
Sediment transport modeling (STM) is a potentially effective tool for
estimating the magnitude of tsunamis and earthquakes without historical
records. However, applying STM to prehistorical tsunamis is challenging
because of many uncertainties in topography and roughness. In the coast
of Hidaka, Hokkaido, Japan, there is potential to conduct STM even in
the absence of historical records because of the comprehensive
geological data that reveal the coastal evolution during the Holocene in
addition to tsunami sediment surveys. The tsunami deposits in Hokkaido
suggest the presence of events on a larger scale than historical
tsunamis; particularly the 17th-century tsunami had multiple potential
wave sources other than a Kuril Trench earthquake, inhibiting its
magnitude estimation. In this study, we applied STM to paleotsunamis in
the coast of Hidaka, where the wave source is unknown and there are
comprehensive geological data. The modeling
parameters—paleotopography, roughness, grain size, initial sand
source, sea level, and beach ridge height—were estimated using data
obtained from geological surveys and sensitivity tests. The modeling of
a tsunami induced by a Kuril Trench earthquake reproduced the sediment
distributions and sedimentary structures of the observed sand layers
better than that of the extreme storm and volcanic tsunami. The paring
down wave sources of the sand layer implies that a wider rupture zone in
the Kuril Trench is less likely. This case study provides information on
the parameters that geologists and modelers should consider when
applying STM to paleotsunamis.