Evidence for coseismic and aseismic uplift in the last 1000 years in the focal area of a shallow thrust earthquake on the Noto Peninsula, west‐central Japan

Abstract

Raised shorelines on the Noto Peninsula on the western coast of central Japan suggest a millennial history of recurrent uplift. Emergence of the coastline by up to 50 cm was recently recorded in association with a moderate earthquake (Mw 6.7) on 25 March 2007. The shoreline uplift is indicated by the displacement of sessile organisms such as calcareous tubeworms, which can also be examined as indicators of past shifts in shoreline level. Three levels of pre‐2007 paleo‐shorelines are thus identified on this stretch of the Japan Sea coast. The lowest of these, dated at AD 1720–1950, tilts northward away from the likely source of a pair of ca. M 6.4 earthquakes in 1892, which occurred in a different area to the 2007 earthquake. The middle paleo‐shoreline, dated at AD 1430–1655, records a 30–40 cm emergence that may be aseismic. The high paleo‐shoreline, dated at AD 1025–1235, records a coseismic uplift of 50 cm and is limited to the area raised coseismically in 2007. The most recent event preceding the 2007 earthquake thus appears to have occurred approximately 1000 years ago.