New analysis of tsunami deposits paints a clearer picture of Sanriku's
past

Date:
February 3, 2022
Source:
Tohoku University
Summary:
The Sanriku Coast - which includes present day Iwate and parts
of Aomori and Miyagi - has been prone to tsunamis throughout its
history. Analyses of tsunami deposits along the coast, however,
haven't always provided conclusive findings. Now, a research
team has utilized a new radiocarbon dating method to clarify the
region's tsunami history and better understand the frequency at
which these disasters occur.



FULL STORY ==========================================================================
A research group comprising members from Tohoku University, Hokkaido
University and the University of Tokyo have developed a high-resolution radiocarbon dating method that can accurately date tsunami deposits,
offering a vital window into past disasters and enabling scientists to
better understand how frequently tsunamis occur.


========================================================================== Tsunami deposits offer scientists important information on tsunamis
that struck before records began. They reveal the frequency and size
of tsunamis. But sometimes the sediment has been washed away or is
incomplete.

The 2011 Great East Japan Earthquake and Tsunami thrust the Tohoku
region into the international spotlight. Yet the area has been prone to earthquakes and tsunamis throughout its history.

Still, scientists are divided on what tsunamis reached the Sanriku
Coast -- the stretch of northeastern coastline along present day Iwate
and parts of Aomori and Miyagi. Inconclusive data rendered scientists
unable to determine whether sediments from the Sanriku Coast belong to
the 1611 Keicho Oshu Tsunami or the 1454 Kyotoku Tsunami.

Tohoku University assistant professor Takashi Ishizawa, who led the
research group, and his team applied their radiocarbon dating method to
a village situated in Iwate Prefecture.

"The village of Noda is strategic for two reasons," says
Ishizawa. "Tsunami deposits formed between the 14th and 17th centuries
have been preserved there, and Noda has inland areas where only giant
tsunamis are capable of inundating." Analyzing the data, in addition to comparing the tsunami records from the surrounding area, the researchers determined that sediment belonged to the 1611 Keicho Oshu Tsunami,
not the 1454 Kyotoku Tsunami.

Moreover, they found the prevalence of giant tsunamis since the 1611
Keicho Oshu Tsunami occurred at intervals between 100 to 200 years.

Ishizawa and his team are looking to apply this method to other locations, including the Sendai Plain to reconstruct a more reliable history of
tsunamis along the entire Japan Trench.

========================================================================== Story Source: Materials provided by Tohoku_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Takashi Ishizawa, Kazuhisa Goto, Yuichi Nishimura, Yosuke Miyairi,
Chikako Sawada, Yusuke Yokoyama. Paleotsunami history along
the northern Japan trench based on sequential dating of the
continuous geological record potentially inundated only by large
tsunamis. Quaternary Science Reviews, 2022; 279: 107381 DOI:
10.1016/j.quascirev.2022.107381 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220203103012.htm

--- up 8 weeks, 5 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)