Fossil tubeworms link coastal uplift of the northern Noto Peninsula to rupture of the Wajima-oki fault in AD 1729

Abstract

The active fault zone on the seafloor off the northern coast of the Noto Peninsula of central Japan is divided into four segments from west to east: Monzen-oki, Saruyama-oki, Wajima-oki, and Suzu-oki. To examine the latest event that occurred in these segments, we investigated the dates and elevations of fossilized intertidal tubeworms along the northern coast of the Noto Peninsula, located on the hanging-wall sides of the faults, using radioactive carbon dating and global positioning measurements. For each fossil, we calculated the difference between the past and present elevation, thereby estimating the elevation of the sea level at the date of the fossil, using a curve for sea level change. This calculation provided us with the elevation change at each site. The radiocarbon dates of the fossils, together with the elevation changes, revealed that the coastal emergence probably occurred between 1600 and 1800 AD. This area of coastal emergence lies adjacent to active faults within the Wajima-oki segment. A model for rectangular faults with three fault planes and a moment magnitude of 6.6 for the Wajima-oki segment reproduced the observed pattern of coastal emergence well. Only one damaging earthquake, that in 1729, is known to have occurred in this part of the northern Noto Peninsula between 1600 and 1800 AD, and there has not been one since 1800 AD. The slip distribution of the earthquake predicted by the model is consistent with the distribution of shaking-related damage documented in 1729. We conclude that rupture of the Wajima-oki segment caused the 1729 earthquake.

Episodic transient deformation revealed by the analysis of multiple GNSS networks in the Noto Peninsula, central Japan

“…Most active faults in the back-arc region of northeastern Japan, including the Noto Peninsula, were formed as normal faults related to the opening of the back-arc before 14 Ma, and they have been reactivated as reverse faults under the compressional stress regime 8 , 9 in terms of inversion tectonics. Several large crustal earthquakes, including the 2007 M w 6.8 Noto Hanto earthquake 10 , 11 and the 1729 M w ~ 6.6 earthquake 12 , occurred around the Noto Peninsula. The location and reverse-fault-type mechanism of these earthquakes suggest that they were caused by the offshore reverse fault system along the northern coast (Fig.…”

“…Focal mechanisms of M w ≥ 6 crustal earthquakes since 1980 are indicated using the Global Centroid Moment Tensor catalog 15 , 16 . The source area of the 1729 M w ~ 6.6 earthquake 12 is indicated. (Inset) Tectonic map of Japan.…”

Late Holocene uplift of the Izu Islands on the northern Zenisu Ridge off Central Japan

“…We therefore make this assumption since there is no reliable way of resolving this ambiguity. This estimation method was also used by Pirazzoli et al (1999), Kitamura et al (2014Kitamura et al ( , 2015Kitamura et al ( , 2016, and Hamada et al (2016).…”

Episodic transient deformation in the Noto Peninsula, central Japan, revealed by the analysis of multiple GNSS networks

“…Focal mechanisms of M w ≥6 crustal earthquakes since 1980 are indicated using the Global Centroid Moment Tensor catalog [51,52] . The source area of the 1,729 M w ~6.6 earthquake [9] is indicated. (Inset) Tectonic map of Japan.…”

“…Most active faults in the back-arc region of northeastern Japan, including the Noto Peninsula, were formed as normal faults related to the opening of the back-arc before 14 Ma, and they have been reactivated as reverse faults under the compressional stress regime [5,6] in terms of inversion tectonics. Several large crustal earthquakes, including the 2007 M w 6.8 Noto Hanto earthquake [7,8] and the 1729 M w ~6.6 earthquake [9] , occurred around the Noto Peninsula. The location and reverse-fault-type mechanism of these earthquakes suggest that they were caused by the offshore reverse fault system along the northern coast (Fig.…”