Fujita et al. Progress in Earth and Planetary Science
https://doi.org/10.1186/s40645-020-00365-9(2020) 7:53

Progress in Earth andPlanetary Science

RESEARCH ARTICLE

Open AccessMillennial paleotsunami history at Minna
Island, southern Ryukyu Islands, Japan
Ryosuke Fujita1*, Kazuhisa Goto2,3, Yasufumi Iryu1 and Tomoya Abe4

Abstract
Huge tsunami waves have repeatedly bombarded the southern end of the Ryukyu Islands (Miyako and Yaeyama
Islands, southwestern Japan) at several-hundred-year intervals. Therefore, clarifying the islands’ paleotsunami history isimportant for risk assessment. Nevertheless, discrepancies of paleotsunami histories exist among regional studies oftsunami boulders and sandy tsunami deposits. Radiocarbon ages of tsunami boulders indicate that tsunami events of
the last 2400 years have occurred every 150–400 years, most recently the historical 1771 Meiwa tsunami. Sandy tsunami
deposits at Yaeyama Islands show that four tsunami events of the last 2000 years struck the islands at approximately
600-year intervals. Sandy tsunami deposits of the Miyako Islands have been studied only rarely. Therefore, studying
sandy tsunami deposits in the Miyako Islands is crucially important for clarifying the paleotsunami history of this region.
We conducted a trench survey on Minna Island, located among the westernmost Miyako Islands, which revealed two
sandy tsunami deposits under a coral tsunami boulder transported by the 1771 tsunami. The upper tsunami deposit
was likely deposited by the 1771 tsunami, as inferred from stratigraphic correlation to the tsunami boulder. However,the lower tsunami deposit was probably deposited 700–1000 years ago, which is consistent with the age range of thepaleotsunami reported for Yaeyama Islands. Because sandy tsunami deposits found in this and earlier studies are thickand deposited at high elevation and far inland, these are useful markers of large tsunami events similar to the 1771
event. However, the reported tsunami boulders of various sizes are deposited along the coast and reefs: they can beformed not only by large tsunami events but also by small ones. It is noteworthy that each tsunami deposit is coarse
and thick (40–48 cm) relative to the island elevation (about 12 m maximum, 7 m above the mean sea level at the studysite). By assuming that tsunamis have affected this region repeatedly during the past few thousand years at around600-year intervals, tsunamis might have been important geomorphic agents for building up small reef-surroundedislands such as Minna Island.
Keywords: 1771 Meiwa tsunami, Geomorphology, Minna Island, Paleotsunami history, Radiocarbon age, Tsunami
boulder, Tsunami deposit

1 Introduction
Understanding paleotsunami history based on the geological record is important for long-term tsunami risk
assessment. Meter-sized boulders are one such example(e.g., Goto et al. 2010a). Many boulders transported anddeposited by paleotsunamis are observed along theshorelines of the Miyako and Yaeyama Islands of thesouthern Ryukyu Islands in southwestern Japan (Fig. 1,* Correspondence: r.trackandfield@gmail.com
1
Department of Earth Science, Graduate School of Tohoku University,
Aramaki-Aza-aoba, 6-3, Aoba-ku, Sendai 980-8578, Japan
Full list of author information is available at the end of the article

Goto et al. 2010a, b, 2019). Some of these boulders,called tsunami boulders, comprise coral rocks(Kawana and Nakata 1994; Omoto 2012; Araoka et al.
2013). From the radiocarbon ages of tsunami boulders, Araoka et al. (2013) inferred statistically thateight tsunamis had struck these islands at 150–400year intervals during the last 2400 years. The latest
event was the Meiwa tsunami in 1771. Numericalanalyses (Hisamatsu et al. 2014) and residual magnetism measurements of tsunami boulders (Sato et al.
2014) further indicated that more than three hugetsunamis as large as the 1771 Meiwa tsunami,© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 2 of 15

Fig. 1 Study area maps: a Ryukyu arc and trench; b Miyako Islands and Yaeyama Islands; c Miyako Islands

including the 1771 event, are likely to have affectedto the Miyako and Yaeyama Islands during the last2000 years.
Historical and geological records of the 1771 Meiwa
tsunami indicate that the maximum runup height was
about 30 m along the eastern coast of Ishigaki Island andthat 12,000 people were killed (e.g., Goto et al. 2010a,
2012a). Although many historical and geological lines ofevidence remain in the Miyako and Yaeyama Islands(Araoka et al. 2010; Goto et al. 2010a, 2012a), the tsunami source remains controversial. The hypotheticalsources include (1) an interplate earthquake plus submarine landslide (Imamura et al. 2008), (2) tsunami
earthquake along the Ryukyu trench (Nakamura 2009),
and (3) a single massive landslide near the trench axis
(Okamura et al. 2018).

Table 1 Representative paleotsunami history in Miyako and Yaeyama Islands
Study

Recurrence(years)

Tsunami age(cal years BP)

Study area

Type of tsunami
deposits

Araoka et al. (2013)

150–400

250–50450–250
650–450
1050–650
1250–1050
1550–1250
1850–1550
2300–2050

Miyako Islands
Yaeyama Islands

Boulder

Kawana and Nakata (1994)

500–1000

150
600–450
1150–950
2450–1900
3700
4400–4300

Miyako Islands

Boulder
Sand

Omoto (2012)-

A.D. 1771–B.C. 252

Miyako Islands

Boulder

Okinawa Prefecture Gusukube Town
Board of Education (2004)-

A.D. 1771

Miyako Islands

Sand

Kugai (2011)-

Nakaza et al. (2013)

A.D. 1771

Miyako Islands

Sand

A.D. 1771

Miyako Islands

Sand

Ando et al. (2018)

630

248
920–620
1670–1250
2700–1670

Yaeyama Islands

Yamamoto (2008) and Yamamoto
et al. (2009)-

750–200

Yaeyama Islands

BoulderSand

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Although sandy tsunami deposits are used frequently to elucidate the paleotsunami histories along
the coast of Japan (e.g., Minoura et al. 2001; Ishimura
and Miyauchi 2015; Kitamura 2016; Inoue et al. 2017;
Shimada et al. 2019), few have been reported from
the Miyako and Yaeyama Islands because of the small
number of surveys (Table 1). Detailed paleotsunami
studies of the islands conducted by Ando et al. (2018)
and by Kitamura et al. (2018a) have specifically examined sandy deposits.
Ando et al. (2018) identified three sandy tsunami deposits (T-I, T-II, and T-IV) and tsunami boulders (T-III
that located stratigraphically between T-II and T-IV)
from an excavated trench at a ranch on the east coast of
Ishigaki Island, Yaeyama Islands. These deposits (T-I toIV) were deposited respectively in AD 1771 (Meiwa tsunami), at 920–620 cal. year BP, at 1670–1250 cal. year
BP, and at 2700–2280 to 1670–1250 cal. year BP. Andoet al. (2018) interpreted that the tsunami events which
formed deposits T-II and IV were of similar size to the1771 tsunami. Kitamura et al. (2018b) used molluscan
assemblages in sandy tsunami deposits at the artificial
trench reported by Ando et al. (2018). They assessed theinfluences of local topographic features on the local tsunami size. They also estimated the local sizes of two

Page 3 of 15

tsunamis that occurred before the 1771 event as being
equivalent to the 1771 tsunami.
Results presented in Table 1 present discrepancies of
paleotsunami histories that exist between studies of tsunami boulders and sandy tsunami deposits in this region.
The tsunami recurrence interval estimated from tsunami
boulders is far shorter than that estimated from sandy
tsunami deposits. The dearth of evidence from the
Miyako Islands prevents elucidation of the paleotsunami
history in this region. Further study of sandy tsunami
deposits is important to resolve this discrepancy. As described herein, we conducted a paleotsunami survey in
Minna Island of the Miyako Islands (Figs. 1 and 2). According to historical documentation, the 1771 Meiwa
tsunami completely inundated this island (Kato 1989),
which is located far from the estimated tsunami source(i.e., southeast of Ishigaki Island). Therefore, paleotsunami evidence of the island is expected to be a key to ascertaining whether powerful tsunami events equivalent
to the 1771 Meiwa tsunami occurred repeatedly andstruck the South Ryukyu Islands.

2 Geological setting
Minna Island, located on the western end of Miyako
Islands, 7 km north of Tarama Island (Fig. 1c), is about

Fig. 2 Aerial photograph of Minna Island: the red line shows an actual route of Ground-Penetrating Rader (GPR) survey; the black line shows the
projected line used to depict cross-sectional subbottom profile in Fig. 3

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

2.5 km2, with approximately 12 m above mean sea level(amsl) maximum elevation. Coral reefs with averagewidth of approximately 500 m surround the whole island(Fig. 2a). Approximately 70% of the island has elevation
lower than 5 m amsl. Today, most lowlands are used as
pastureland (Yazaki 1977). The Ryukyu Groups consistof reef limestone (Iryu et al. 2006) with tens of meters
thickness, constituting the basement rock of this island.
The island is covered with dune sand and 7–11 m thicksoil (Yazaki 1977).
An emerged shoreline, indicated by erosional notches,
benches, and beach rocks, occurs at an elevation of 1.5
m along the coast of Tarama Island, immediately southof Minna Island (Fig. 1). Based on 14C dates of a coraland a tridacnine shell, Pirazzoli et al. (1984) reported
continuous and gradual sea-level fall for the last 4000
years. Similarly, based on 14C dates of corals and coralline algae, along with geomorphological observations,
Konishi and Matsuda (1980) showed that the presentday reef crest of Kabira Reef, Ishigaki Island (Fig. 1), exposing 60 cm above the mean low tide level represent arelic of a salient ridge grown between 1500 and 3000
year BP, when the sea level stood at least 1.5 m higher
than at present. This view was supported by evidence
from Yamano et al. (2001), who studied the anatomy of
Kabira Reef, showing that a stable sea level between
6000 and 2000 year BP was followed by a relative sealevel fall because of tectonic uplift associated with thetilting of Ishigaki Island (Kawana 1986, 1989). This
tectonic movement occurred at 1700–2700 year BP (centered at 2000–2400 year BP) throughout the Ryukyu
Islands.
We consider that Minna and Tarama islands havebeen uplifted since the late Middle Pleistocene, as indicated by the occurrence of upper Middle and upper
Pleistocene reef limestones offlapping the main body of
the Ryukyu Group (Iryu et al. 2006). The occurrence ofthe reef crest, subaerially exposed at the low tide, suggests tectonic uplift occurring in these islands at approximately 2000–2400 year BP, as reported throughout
the Ryukyu Islands.
A 33-ton tsunami boulder made of Porites sp. is located at elevation of 7 m amsl and 350 m inland fromthe present beach inferred as being of 1771 Meiwa tsunami origin based on radiocarbon dating results (AD1515–1814 (2σ); Kato 2000; Goto et al. 2010c). Although
the ground surface of this island might have been disturbed to make pastureland, presence of the 1771 Meiwa
tsunami boulder suggests that at least the ground beneath the boulder has not been disturbed by human activities since the 1771 tsunami. Recent studies
conducted after the 2011 Tohoku-oki tsunami revealed
that tsunami-transported sand layers are usually formed
below the boulder deposits because sands are moved

Page 4 of 15

and deposited faster than the boulders (Goto et al.
2012b; Yamada et al. 2014), although this is not always
the case (e.g., Yawsangratt et al. 2009). Therefore, sandy
deposits can be expected to have originated by the 1771
Meiwa tsunami or older events are preserved below thisboulder. We therefore decided to dig a trench immediately beneath this boulder.

3 Methods/experimental
A field survey was undertaken during 18–22 April 2017.
We first excavated a 115 cm-deep trench beneath theboulder. After description, we took 115 bulk sediment
samples consecutively at 1 cm intervals. Additionally, we
took marine shell and coral fragments from possible tsunami deposits for radiocarbon dating.
We also conducted a survey using ground-penetratingradar (GPR, SIR-3000; GSSI Inc., Nashua) along theroute presented in Fig. 2b to identify cross-sectional subsurface structures. The data were processed by an analytical method using software (RADAN7; GSSI Inc.,
Nashua) referred from a report by Takeda et al. (2018).
Using a “Pick” module with REFLEXW software (Sandmeier Geophysical Research, Karlsruhe), strong reflectors were detected from GPR profiles. Global Navigation
Satellite System (GNSS) topographic measurement (Promark 120; Geosurf Corp., Tokyo) was also applied to
produce a cross-sectional profile near the survey trench
and to correct the elevation of the GPR profile.
For grain size analysis, we removed organic matter(e.g., plant roots) with 10 wt% H2O2. Additionally, to investigate grain size composition and major components
of sand grains at our study site, we removed the mud
component (< 63 μm) by wet sieving. Grains generally of> 2 mm were removed by hand picking. Then, we measured the grain size distribution of residual samples
using a settling tube method with STube software (Naruse 2005). Results were compiled using software(GMT5, SOEST; University of Hawaii) to estimate thegrain size distribution with volume percentage. For peak
splitting, the Gaussian distribution was applied to every
peak graph using software (ORIGIN 2015; Origin Lab,
Massachusetts). Although we removed mud and gravelcomponents, a few might have been left in the residue.
To illustrate vertical change of grain size distribution,
we calculated statistical values (mean size, median size,and sorting) using data ranging from − 1 to 4 phi,
whereas data out of this range were not used. Mean andmedian grain sizes and sorting were calculated using the
moment method (Folk 1966).
The tsunami deposit itself is usually a mixture of redeposited sediment from various sources. Therefore, radiocarbon dating is better conducted using organic matterin sediments immediately above and below the deposit(Sawai 2012). However, at our study site, this approachFujita et al. Progress in Earth and Planetary Science(2020) 7:53

is not useful because the site is located in a subtropicalregion. Sediments above and below the possible tsunami
deposit comprise sand-sized carbonate grains; moreover,they have been disturbed considerably by vegetation.
The possible tsunami deposit in our site includes many
coral and mollusk fragments. Therefore, some specimens
which retain their original mineralogy and in which no
diagenetic product (e.g., marine cements) is observed arehighly likely to have been killed by the tsunami andtherefore represent the tsunami age. We analyzed
ages of such samples taken directly from the possible
tsunami deposit.
Before 14C dating, we checked whether samples
retained the original mineralogical composition of marine shells or skeleton (aragonite), using X-ray diffraction(XRD) analysis with X’pert-MPD (PW3050; Philips Co.,
Amsterdam) X-ray diffractometry and using observationof coral skeletons and a marine shell done with scanning

Page 5 of 15

electron microscopy (SEM, VE-8800; Keyence Co.,
Osaka) at the Department of Earth Science, Graduate
School of Science, Tohoku University. 14C ages were
measured using an accelerator mass spectrometer at
Beta Analytic Inc. in Miami, USA. The Marine13 dataset(Reimer et al. 2013) with CALIB 7.1 software (Stuvier
and Reimer, 1993; Stuiver et al. 2020) was adopted to
calculate the calibrated ages. A local reservoir correction(ΔR = – 36 ± 78; Hirabayashi et al. 2017) for the Central
Ryukyus was used for this study.

4 Results
4.1 Topography and GPR profile

Figure 3a portrays a cross-sectional profile produced
from GNSS and GPR profile measurements. From thebeach to 100 m inland, the elevation increases steeply to
6.5 m amsl and forms sand dunes. Over 100 m from theFig. 3 Topography and GPR profile around the tsunami boulder: a profile along the GPR lines in Fig. 2b; b processed subbottom profile withinterpretation. Blue dots and lines show strong reflectors in the GPR survey section. White arrows indicate reflectors that are parallel to theground surface. Yellow arrowheads indicate reflectors that are parallel to the beach slope

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

beach to the boulder/trench site, the elevation is roughly
constant at about 5–7 m amsl.
A processed GPR profile (Fig. 3b) shows some clear
successive reflectors. First, several reflectors that are parallel to the present beach slope are observed from 50 to
350 m from the beach. Another reflector, which is parallel to the ground surface, is also observed at about 50
cm below the ground from 50 to 150 m and from 350 to
500 m from the beach. A clear reflector expected to correspond to the boundary between the sand deposit andthe underlying reef limestone was not detected up to 7
m depth.
4.2 Trench description

The 1771 Meiwa tsunami boulder at the trench site, whichis 3.7 m long, 3.1 m width, and 2.3 m height (Fig. 4a), is
made of a massive coral of Porites sp. The present boulder
orientation is similar to its original living position.

Page 6 of 15

Based on the color and grain size, sediments in the
115 cm deep trench are classified into five layers fromthe bottom to the top (Figs. 4b-d and 5): layer 1 (L1, 0–
27 cm above the trench bottom) consisting of darkbrown medium-grained sand, layer 2 (L2, 27–60 cm
above the trench bottom) of dark brown mediumgrained to coarse-grained sand, layer 3 (L3, 60–67 cm
from the trench bottom) of dark brown medium-grained
sand, layer 4 (L4, 67–95 cm from the trench bottom) of
yellowish brown medium to very coarse sand, and layer
5 (L5, 95–115 cm from the trench bottom) of darkbrown medium sand. The boundaries of the respective
layers are generally clear. However, the boundary between L2 and L3 is not clearly visible to the naked eye
while we established the boundary in the field based on
the difference of grain size. The boulder is deposited
directly on top of L4, whereas L5 is not observed immediately beneath the boulder (Fig. 4b, c). Visually,

Fig. 4 Outcrop photographs: a tsunami boulder composed of Porites sp. at 7 m elevation; b trench below the boulder; c relation among thetsunami boulder, L4 and L5; d stratigraphy of the trench from L1 to L5. It is noteworthy that the boulder is deposited not on L5, but on L4

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 7 of 15

Fig. 5 Logs of lithology and grain size. Colors of the lithologic log roughly correspond to the actual color of L1 to L5 (see also Fig. S1): m, medium
sand; c, coarse sand; v.c., very coarse sand. Mean and median grain sizes and sorting are shown

sedimentary structures in each layer are not clear. Most
sediment constituent materials are bioclastic grainstone.
The grains of the respective layers are composed
mainly of foraminiferal tests such as Calcarina sp. andMarginopora sp. with bioclasts of corals, coralline algae,
bivalves, and gastropods (Fig. S1). The grains in L2 andL4 are well preserved. Several-millimeter-sized tocentimeter-sized bivalves, gastropods, and corals arecommonly found from the lower part of L2 and L4.
4.3 Grain size

Figure 5 shows vertical changes in grain size distribution
together with statistical mean and median grain sizes
and sorting of each layer in the trench. The grain size
distribution in L1 has a mode at around 1.5 phi. It rarely
contains grains of < 0 phi or > 2.5 phi. It also shows normal grading.
In L2, the grain size distribution changes abruptly inthe middle part at 48 cm above the trench bottom (Fig.
5). The lower part (27–48 cm above the trench bottom)
shows a bimodal grain size distribution with modes at 0
phi and 1.4 phi (Fig. 6c). The grain size distribution in
the upper part (48–60 cm above the trench bottom) israther similar to that of underlying layer 1, with a modearound 1.5 phi (Fig. 6a, b). Mean and median grain sizes
respectively show inverse grading and normal grading in
the lower and upper parts of L2. Although sorting is
moderate in the lower part, it decreases toward the top.
The grain size distribution of L3 and L5 has a mode ataround 1.5 phi. These layers show a similar grain size
distribution, which is apparent also in mean and mediangrain sizes and sorting. The grain size distribution of L4,

which resembles that of L2, is divisible into lower andupper parts with a boundary at around 88 cm above thetrench bottom (Fig. 5). The lower part is characterized
by inverse grading with moderate sorting. However, theupper part is characterized by normal grading trend withwell sorting.
Figure 7 presents a comparison of statistical values(mean vs. sorting, median vs. sorting). Mean and mediangrain size in L3 and L5 were 1.2–1.6 phi with sorting of
0.55–0.75 phi. The upper parts of L2 and L4 show similar trends to those of L3 and L1. In contrast, the lower
parts of L2 and L4 have different trends: mean grainsize, 0.6–1.25 phi; median grain size, 0.6–1.3 phi; andsorting, 0.6–0.95 phi. Overall, the lower parts of L2 andL4 were coarser and poorer sorted than other layers.
4.4 Radiocarbon dating

We selected two coral samples for radiocarbon dating of
L4: Acropora sp. 1 and Acropora sp. 2. Both samples are
the least abraded among the samples taken from L4 (Fig. 8
a and b). The respective calibrated dates (2σ) are 787–1170
cal AD (Acropora sp. 1) and 244–632 cal AD (Acropora sp.
2) (Table 2).
We selected disarticulated marine shells of bivalve(Atactodea striata) and coral (Palauastrea ramosa) samples, both of which were the least abraded among thesamples taken from L2 (Fig. 8c, d). Atactodea striata is abivalve living in intertidal zone sand (Kondo et al. 2001).
Palauastrea ramosa is a branching coral typically living
around the equatorial Pacific. The respective calibrated
dates (2σ) are 947–1281 cal AD (A. striata) and 1028–
1327 cal AD (P. ramosa) (Table 2).

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 8 of 15

Fig. 6 Averaged grain size distribution of each layer: black squares, original data; blue lines, overall distribution against grain size; green lines,
larger peaks; red lines, smaller peaks. These lines were produced by ORIGIN software

5 Discussion
5.1 Identification of tsunami deposits

Trench observations and grain size analyses clarified that
sedimentary features of L2 and L4 are significantly different from other layers. For example, in the case of L4,
the color (yellowish brown) is brighter than those ofunderlying L3 and overlying layer L5 (dark brown) (Fig.
4d, S1). Moreover, the layer is divided by a sharp boundary from L3 (Fig. 4c, d). The lower part of L4 is poorersorted and coarser than L3 which is well-sorted andfiner throughout the layers (Figs. 5 and 7). L4 yields
abundant well-preserved bioclasts of corals, coralline
algae, bivalves, and gastropods as large as pebble sized,
although reworked fragments of them were also observed. These bioclasts are likely to be composed ofgrains originated from various sources such as a shallow
part of fringing reefs (shallow lagoon and upper forereef
slope), beach, or sand dunes. By contrast, L3 and L5 include fewer sand-sized bioclasts than L4 does.

Similarly, the grain composition of L2 seems clearly
different from those of underlying L1 and overlying L3(Figs. 5 and 7) in that the former includes abundant
shallow marine bioclasts of corals, coralline algae, bivalves, and gastropods, although L2 is dark brown, as is
L1 (Fig. 4d, S1). In addition, L2 is composed mainly ofpoorer-sorted and larger bioclasts than those of L1 or L3(Figs. 5 and 7). Therefore, it is highly probable that the
sediments in L2 originate from a similar environment tothat of L4.
The lower parts of L2 and L4 show a bimodal grain
size distribution with modes at 0 phi and 1.5 phi (Fig.
6c) and moderately sorted (sorting: 0.7–0.9 phi) (Fig. 5).
In contrast, grain size distributions of the upper parts of
L2 and L4 and other layers L1, L3, and L5 show a single
peak (1.5 phi) (Fig. 6a, b) and are well-sorted (sorting:
0.6–0.7 phi) (Fig. 5). These differences are characterized
by the amount of coarse-grained bioclasts (− 1 to 1 phi).
Moreover, median (or mean) grain sizes of L2 and L4

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 9 of 15

Fig. 7 Statistical values of grain size: a, mean grain size versus sorting; b, median grain size versus sortingshow inverse grading trends in the lower parts and thennormal grading trends toward the upper parts (Fig. 5).
Although a combination of inverse to normal grading
trends was rarely observed in the steady sedimentary
processes, it was often observed in deposits formed byhigh-energy water-related events such as tsunami events(e.g., Naruse et al. 2010, 2012; Moore et al. 2011). Therefore, it is highly likely that high-energy flows formed L2and L4. Because this island has no river, flooding can beruled out. The deposits could only have been formed bycoastal waves such as tsunami and storm waves.
Our study site was located 350 m distant from thebeach at 7 m amsl elevation (Fig. 3). The coastal areaaround the study site was surrounded by coral reefs ofapproximately 500 m width from the shoreline to thereef edge (Fig. 2). Goto et al. (2013) studied the distributions of storm wave boulders (> 1 m on the long axis) on
coral reefs at many islands of the Ryukyu Islands including Minna Island, which revealed that distribution of theboulders transported by the storm waves was limited to
300 m distance from the reef edge. Numerical simulationof storm waves at the eastern coast of Ishigaki Island(Hongo et al. 2012; Watanabe et al. 2016) demonstrated
that the storm-wave velocity near the shoreline is remarkably low. Consequently, it is highly unlikely thatstorm waves can transport sediments up to elevation of
7 m amsl with more than 850 m distance from the reefedge. Minna Island is well known from historical records(e.g., Kato 1989; Goto et al. 2010b) to have been inundated completely by the 1771 Meiwa tsunami. Numerical modeling further suggests that effects of the 1771
Meiwa tsunami on the Miyako and Yaeyama Islands
were remarkable (Goto et al. 2010a, b, 2019). This point

was confirmed further by the presence of a Porites boulder of 1771 Meiwa tsunami origin at our study site atelevation of 7 m amsl (Kato 2000; Goto et al. 2010c).
Both L2 and L4 are observed just beneath this boulder.
Because the tsunami waves had sufficient energy totransport the huge boulder to the site, it is evident thatthe tsunami also had the capability to transport finersand to pebble-sized grains. Consequently, L2 and L4
are regarded as having been formed by tsunami waves.
It is noteworthy that L1, L3, and L5 also consist of
sandy sediments composed of bioclasts of reef organisms(Fig. S1). Their sources and sedimentation processes
must be considered. Actually, the grain sizes and compositions of these three layers closely resemble those of
the upper parts of L2 and L4 in that they have a single
mode at 1.5 phi (Fig. 6) and include bioclasts of reef organisms. One possible origin of sands in L1, L3, and L5
might be blown sand because the grain size is generally
small. However, the grain size of blown sand is wellknown to be finer than 1 phi (e.g., Inokuchi 1980; Goosemann et al. 2018; Lämmel et al. 2018), whereas L1, L3,
and L5 all include considerable amounts of grains larger
than 1 phi (Fig. 5). Therefore, blown sand is unlikely to
be a source of these layers.
Alternatively, L3 and L5 might have been originallythe topmost parts of L2 and L4 (equal to tsunami deposits), respectively, but they might then have beenaltered through a long-term pedogenic process after
the tsunami events. In fact, the topmost part of thetsunami deposit is well known to be disturbed by bioturbation and reworking processes after the tsunami
event. Soils originate from sand particles of the topmost part of the tsunami deposit (e.g., Goto et al.

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 10 of 15

2012c; Szczuciński 2012). Considering the similaritiesof the grains between the upper part of L2 and L3,
and the upper part of L4 and L5, respectively, this interpretation is the most likely to be true. This interpretation is further supported by the observed factthat L5 is lacking immediately beneath the 1771 tsunami boulder (Fig. 4b, c). This feature is explainable
by the fact that no vegetation could have grownunder the boulder. The upper part of L4 includes nocoarser materials, although a minor amount ofcoarser materials is observable in L5. Similar grain
size variation is sometimes reported also in the modern and paleotsunami deposits, and is inferred because of tsunami backwash or posttsunami local
sediment reworking (e.g., Komatsubara et al. 2008;
Takashimizu et al. 2012); both interpretations can beapplicable to explain the grain size variation of theupper part of L4 and L5 found in our case.
If the interpretations presented above are correct, then
L3 and L5 should be considered respectively as parts of
L2 and L4. Therefore, we infer that two tsunami deposits
exist at our study site with 40 cm thickness (L2 plus L3)
and 48 cm thickness (L4 plus L5). We dug the trenchwith only 115 cm depth. For that reason, we were unable
to observe the underlying deposits of L1. It remains uncertain whether L1 is the topmost part of an older tsunami deposit, or not.
Tsunami deposit thicknesses estimated in this study(40 cm and 48 cm) are remarkably thicker than those reported in earlier works (e.g., Szczuciński 2012; Richmond et al. 2012). Nevertheless, our study site is distantfrom the shoreline, probably for the following threemajor reasons, all of which are related to the specificsedimentary environment around Minna Island.
Fig. 8 Samples for radiocarbon dating: a Acropora sp. from L4; b
Acropora sp. from L4; c Atactodea striata from L2; d Palauastrea
ramosa from L2; e SEM image of P. ramosa from L2. These samples
are composed exclusively of aragonite. Their external morphologies
exhibit a good state of preservation(1) Minna and the nearby Tarama islands wereconnected on the plateau at the shallow sea.
Similarly to the present setting, abundant sands andgravels could have been deposited on the shelfduring the past few hundred years. In addition,
most of the island is rimmed by dunes. Therefore,
abundant source sediments should have been
available elsewhere, ranging from the shallow sea
including reefs to the dunes.
(2) The island is low and flat with only a smallterrestrial area. Given such a setting, tsunami waves

Table 2 Radiocarbon ages of bioclasts collected from the trench wall
SampleBeta ID Conventional radiocarbon age (years BP) Calibrated age (cal years AD (2σ)) Median (cal years AD) d13C (‰)

Layer 4 Acropora sp. 1

541257 1380 ± 30

787–1170

982

0.68

Acropora sp. 2

541258 1920 ± 30

244–632439

1.61

481330 1260 ± 30

947–1281

1112

1.9

Palauastrea ramosa 481331 1170 ± 30

1028–1327

1190

− 0.5

Layer 2 Atactodea striata

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

are likely to have inundated from multiple
directions, as reported in the case of the 1992
Flores tsunami that struck Indonesia (Minoura et al.
1997). Based on historical records and the
distribution of tsunami boulders at Tarama Island,
Kawana (2004) reported that, during the 1771
Meiwa tsunami, the tsunami waves probably
inundated the island from multiple directions
because of wave diffraction. One can readily
imagine that similar diffraction of tsunami waves
occurred at Minna Island because the island shaperesembles that of Tarama Island. If multidirectional
inundation occurred, tsunami deposit thickness
might be exaggerated several fold because of
sediment transport from multiple directions.
(3) Minna Island has poor soil development. For thatreason, coastal vegetation is low. Therefore, it islikely that tsunami was not attenuated duringonshore inundation. Hence, the sediment transportcapacity was maintained as high. This interpretation
is emphasized further by the fact that even meterlong large boulders were transported at our studysite (elevation of 7 m amsl).
Together with the three reasons above related to thespecific environment of the Minna Island, grain composition constitutes an additional one. Since deposits
are composed mostly of calcareous bioclasts that havelower density than silicate minerals such as quartz andfeldspar; the former can be expected to have beentransported easier than the latter. Calcareous bioclastsalso show irregular shape; hence the rate of spacefilling of the tsunami deposit can be low. These effects
can also contribute to increased total thicknesses of thetsunami deposits at our site.

Page 11 of 15

5.1.1 Age of paleotsunami at Minna Island

Regarding the older tsunami deposit (L2 plus L3), theradiocarbon ages of the marine shell and the coral areconsistent at around 920–670 cal BP (Table 2, Fig. 9).
We used samples taken directly from L2 for dating.
Therefore, our result should be regarded as the limiting
maximum age: the actual tsunami event might be younger (but older than A.D. 1771). The samples used forradiocarbon dating retained their original mineralogy
with no diagenetic alteration. Their surface textures(e.g., corallites and septa of P. ramosa) were well preserved (Fig. 8e). Therefore, it is most likely that they
were alive immediately before the tsunami event. However, as in the case of L4, more radiocarbon results ofsamples from L2 must be acquired to support accurate
estimation of the age of tsunami occurrence.
The calibrated age of the paleotsunami event estimated in this study (920–670 cal BP) partly overlaps
with the age of event II (920–620 cal BP) reported byAndo et al. (2018) and event 4 (1050–650 cal BP) reported by Araoka et al. (2013) (Fig. 9). Ando et al.
(2018) and Kitamura et al. (2018a, b) studied a sandy
tsunami deposit at Ishigaki Island and inferred thatevent II was an event as large as the 1771 Meiwa tsunami. Therefore, one can reasonably infer that older tsunami deposits at our site were formed by the same
event.
The radiocarbon ages of the two samples taken fromL4 are considerably older than those of L2. A tsunami
can transport sediments elsewhere from the reef, beach,and sand dune during propagation. Abundant old samples of up to 4000 years old at most can be buried in thereef sediments in the Ryukyu Islands (Yamano et al.
2001; Fujita et al. 2015). Therefore, it is likely that the
samples selected for radiocarbon dating of L4 were old

Fig. 9 Interpretation of paleotsunami histories: green lines, this study; blue lines, Ando et al. (2018); pink lines, Araoka et al. (2013); yellow lines,
Kawana and Nakata (1994). The age of L4 is not estimated by radiocarbon ages but by deposition orderFujita et al. Progress in Earth and Planetary Science(2020) 7:53

reef sediments: the obtained ages were much older than
the actual tsunami age.
Based on our present limited dataset, one possible interpretation is that L4 was formed by the pre-1771 tsunami that might correspond to the tsunami event 2 or 3
of Araoka et al. (2013) (Fig. 9). However, it is uncertain
whether these events are comparably large when measured next to the 1771 Meiwa tsunami (e.g., Araoka
et al. 2013; Ando et al. 2018). Historical documents suggest that Minna Island was inundated completely by the1771 Meiwa tsunami (Kato 1989), suggesting that thetsunami was very large at this island. Because the 1771
Meiwa tsunami boulder is deposited directly on L4 (Fig.
4c), one can consider that the boulder was deposited
simultaneously to the deposition of L4 plus L5. As described above, sand-sized and gravel-sized sediments arewell known to be transported and deposited earlier thanboulders because of their size and weight differences(Goto et al. 2012b; Yamada et al. 2014); deposition of L4
plus L5 and overlying tsunami boulders is explainable bytheir similar sedimentary processes. For Minna Island,
we infer that the 1771 Meiwa tsunami transported sandand gravel and formed a sheet-like layer on land. Subsequently, a large Porites boulder was transported and deposited on the sandy and gravelly layer by the sametsunami. Therefore, L4 plus L5 can be interpreted stratigraphically as being of 1771 Meiwa origin. However, toconfirm the origin of L4 plus L5, several radiocarbon
dates must be measured in future work; then the youngest age which is taken can be regarded as representing
the actual tsunami age.
It is noteworthy that our study at Minna Island was
conducted at a high elevation protected by wide coral
reefs. Therefore, only large tsunamis, equivalent to the1771 Meiwa tsunami, would be able to leave a thick sandsheet. Our results suggest that at least two large tsunamis struck the Miyako Islands at possibly A.D. 1771
and during A.D. 1000–1300, although we cannot fully
exclude the possibility that the upper tsunami deposit(L4 plus L5) was formed by a different tsunami thattransported the 1771 tsunami boulders: one more large
tsunami struck the area in the intervening period. In either case, considering our results along with those ofearlier studies (Kawana and Nakata 1994; Omoto 2012;
Araoka et al. 2013; Hisamatsu et al. 2014; Ando et al.
2018; Kitamura et al. 2018a, b), we conclude that large
tsunamis repeatedly struck both the Miyako andYaeyama Islands. Consequently, the hypothesis that the1771 Meiwa tsunami was the only extraordinary event of
the past (Nakaza et al. 2013) is less likely.
Results reported by Ando et al. (2018) and those obtained from the present study indicate that an interval ofa tsunami event that is sufficiently powerful to lead to
sandy tsunami deposit formation far inland is about 600

Page 12 of 15

years. In contrast, Araoka et al. (2013) reported that therecurrence interval of a tsunami event that is sufficiently
powerful to transport meter-scale boulders on the coastof the Miyako and Yaeyama Islands is about 150–400
years, which is far shorter than the interval estimatedfrom sandy tsunami deposits. This discrepancy is probably explained by the fact that smaller tsunami boulders(1–2 m diameter) can be deposited even by small tsunamis (Araoka et al. 2013), although no possible sourceof small tsunami event able to transport 1–2 m–sizedboulders has been discussed so far in this area. Large
tsunamis forming thick sandy tsunami deposits far inland at high elevations rarely occur, which in turn suggests that the combined paleotsunami histories
estimated from studies of boulders and sandy tsunami
deposits will elucidate separate recurrence intervals of
tsunami events of different sizes.
Several source models for the 1771 Meiwa tsunami
have been proposed: intraplate earthquake plus submarine landslide (Imamura et al. 2008; Miyazawa et al.
2012), tsunami earthquake along the Ryukyu Trench(Nakamura 2009), and large slope failure near the trenchaxis (Okamura et al. 2018). Although our study is notconclusive on this issue, results suggest that either
model can explain the repeated generation of both small
and large tsunamis. Further careful paleotsunami research must be conducted with numerical modeling toconstrain these tsunami source models.
5.1.2 Tsunami as a geomorphic agent of small reef island

Large tsunami waves can drastically change the coastal
topography of small islands with circumjacent reefs(Kench and Brander 2006; Kench et al. 2008; Paris et al.
2009). As the GPR profile of our site shows (Fig. 3b), nostrong reflector exists from the ground surface (approximately 7 m amsl elevation) to 0 m amsl at our trench site
except for a strong reflector at 50 cm depth, which corresponds to the base of L4. This result implies that thebasement Ryukyu Group might be located below elevation of 0 m amsl and that sediments of about 7 m thickness from the ground surface are probably composed ofsand. Indeed, Yazaki (1977) pointed out that the dunesand thickness at Minna Island is at least 7 m.
The coral reefs at Minna Island were probably constituted in their present form around 5000 years ago(Omoto 2004). Here, we assume that sufficient sediments exist at the source region among tsunami events.
This assumption is probably valid because approximately
250 years have passed since the 1771 tsunami and because the present sediment production in the source region at the beach and the reefs is very high at thisisland. Therefore, a-few-hundred-year tsunami interval issufficiently long for the accumulation of thick sedimentsin the source region. If one assumes that large tsunamis

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Page 13 of 15

struck repeatedly during this period with a 600-year
interval, then eight or more tsunamis might have inundated Minna Island during the last 5000 years. If eachtsunami formed sediments with 40–50 cm thickness,then the sediments would reach 3.2–4.0 m thickness. Although many other processes such as tsunami erosion,
crustal movement, relative sea level change, dune formation, blown sand, and pedogenic processes should also
be considered, we infer that tsunami waves can be an
important geomorphic agent for the formation of reefsurrounded small islands such as Minna Island in thisregion, where tsunamis frequently exert their effects inshort intervals.

Authors’ contributions
RF, KG, YI, and TA conducted field surveys, collected samples and data, andparticipated in discussion during the research. RF mainly performedexperiments and wrote the manuscript. KG proposed the study topic andconceived and designed the study. YI conducted identification of carbonate
samples and assisted in the interpretation of XRD/SEM results. TA provided
geological information of Minna Island and conducted statistical analysis ofgrain size. All authors read and approved the final manuscript.

6 Conclusions
We discovered two sandy tsunami deposits on Minna Island. The younger tsunami deposit is likely to have been
formed by the 1771 Meiwa tsunami, whereas the older
one was probably formed by a tsunami at around 920–
670 cal BP. However, several more samples must be
dated to provide more accurate tsunami age assessment.
Our results indicate that at least two tsunamis (the 1771
Meiwa tsunami and an older one comparable to the1771 event) are likely to have hit not only the Yaeyama
Islands but also the Miyako Islands during the last 1000
years. This finding presents important implications elucidating the paleotsunami history of the Miyako andYaeyama Islands, whether large tsunamis occurred periodically or not. Indeed, this region shows high risk of
low-frequent but powerful tsunami events.
It is also likely that the tsunami waves repeatedlytransported and deposited thick sands on land. In fact,
these sedimentation events might have contributed to
the geomorphological development of Minna Island in
the late Quaternary. Therefore, we infer that tsunami
waves can be one important agent forming and modifying the geomorphology of small reef-encircled islands.

Competing interests
The authors declare that they have no competing interest.

7 Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s40645-020-00365-9.
Additional file 1: Fig. S1. Close-up photographs of sands in L1–L5

Abbreviations
amsl: above the mean sea level; GPR: Ground-Penetrating Rader; XRD: X-Ray
Diffraction; SEM: Scanning Electron Microscopy

Acknowledgments
We thank an area land owner for his kind help with our study and thank K.
Miyagi for his cooperation with our field survey. We also thank D. Yamaguchi
and S. Sato for identification of coral and molluscan samples and T. Ishizawa
for his advice of the radiocarbon dating. We also thank K. Ikehara and two
anonymous reviewers for their valuable suggestions and comments.

Funding
This research was partly supported by research funding from JSPS KAKENHI
Grant Numbers (JP15H05220) and by the Ministry of Education, Culture,
Sports Science and Technology (MEXT) of Japan, under its The Second
Earthquake and Volcano Hazards Observation and Research Program(Earthquake and Volcano Hazard Reduction Research).
Availability of data and materials
Please contact the corresponding author with data requests.

Author details
Department of Earth Science, Graduate School of Tohoku University,
Aramaki-Aza-aoba, 6-3, Aoba-ku, Sendai 980-8578, Japan. 2International
Research Institute of Disaster Science, Tohoku University, Aramaki-aza-Aoba,
468-1, Aoba-ku, Sendai 980-8572, Japan. 3Department of Earth and Planetary
Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033,
Japan. 4Geological Survey of Japan, National Institute of Advanced Industrial
Science and Technology, Central 7, Higashi 1-1-1, Tsukuba 305-8567, Japan.
1

Received: 29 January 2020 Accepted: 20 August 2020

References
Ando M, Kitamura A, Tu Y, Ohashi Y, Imai T, Nakamura M, Ikuta R, Miyairi Y,
Yokoyama Y, Shishikura M (2018) Source of high tsunamis along thesouthernmost Ryukyu trench inferred from tsunami stratigraphy.
Tectonophysics 722:265–276
Araoka D, Inoue M, Suzuki A, Yokoyama Y, Edwards H, Cheng H, Matsuzaki H, Kan
H, Shikazono N, Kawahata H (2010) Historic 1771 Meiwa tsunami confirmedby high-resolution U/Th dating of massive Porites coral boulders at Ishigaki
Island in the Ryukyus, Japan. Geochem Geophys Geosyst 11. Q06014, https://doi.org/10.1029/2009GC002893
Araoka D, Yokoyama Y, Suzuki A, Goto K, Miyagi K, Miyazawa K, Matsuzaki H,
Kawahata H (2013) Tsunami recurrence revealed by Porites coral boulders inthe southern Ryukyu Islands, Japan. Geology 41:919–922. https://doi.org/10.
1130/G34415.1
Folk RL (1966) A review of grain-size parameters. Sedimentology 6:73–93. https://doi.org/10.1111/j.1365-3091.1966.tb01572.x
Fujita K, Asami R, Takayanagi H, Iryu Y (2015) Carbonate sedimentation inseagrass beds on Ishigaki-jima, Ryukyu Islands, southwestern Japan. Island
Arc 24:263–279. https://doi.org/10.1111/iar.12112
Goosemann EA, Catling DC, Som SM, Altermann W, Buick R (2018) Eolianite grain
size distributions as a proxy for large changes in planetary atmosphericdensity. J Geophys Res 123:2506–2526. https://doi.org/10.1029/2018JE005723
Goto K, Hongo C, Watanabe M, Miyazawa K, Hisamatsu A (2019) Large tsunamis
reset the growth of massive corals. Prog Earth Planet Sci 6:14. https://doi.org/
10.1186/s40645-019-0265-2
Goto K, Kawana T, Imamura F (2010a) Historical and geological evidence ofboulders deposited by tsunamis, southern Ryukyu Islands, Japan. Earth Sci
Rev 102:77–99. https://doi.org/10.1016/j.earscirev.2010.06.005
Goto K, Miyagi K, Imamura F (2013) Localized tsunamigenic earthquakes inferredfrom preferential distribution of coastal boulders on Ryukyu Islands, Japan.
Geology 41:1139–1142. https://doi.org/10.1130/G34823.1
Goto K, Miyagi K, Kawamata H, Imamura F (2010b) Discrimination of boulders
deposited by tsunamis and storm waves at Ishigaki Island, Japan. Mar Geol
269:34–45. https://doi.org/10.1016/j.margeo.2009.12.004
Goto K, Miyagi K, Kawana T (2010c) Discovery of the large Porites boulders by
the 1771 tsunami at Tarama and Minna Islands, Japan. Res Rep Tsunami Eng
27:97–102

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

Goto K, Miyazawa K, Adaniya A, Kakihana S, Kugai M, Shimabukuro A, Masaki J,
Matsushima S, Miyagi K (2012a) Reconsideration of the run-up height of the1771 Meiwa tsunami II – Sakishima Islands. Res Rep Tsunami Eng 29:129–146
Goto K, Sugawara D, Ikema S, Miyagi T (2012b) Sedimentary processes associatedwith sand and boulder deposits formed by the 2011 Tohoku-oki tsunami at
Sabusawa Island, Japan. Sediment Geol 282:188–198. https://doi.org/10.1016/
j.sedgeo.2012.03.017
Goto K, Takahashi J, Fujino S (2012c) Variations in the 2004 Indian Ocean tsunami
deposits thickness and their preservation potential, southwestern Thailand.
Earth Planet and Space 64:923–930. https://doi.org/10.5047/eps.2011.08.019
Hirabayashi S, Yokoyama Y, Suzuki A, Miyairi Y, Aze T (2017) Short-term
fluctuations in regional radiocarbon reservoir age recorded in coral skeletonsfrom the Ryukyu Islands in the North-Western Pacific. J Quat Sci 32:1–6.
https://doi.org/10.1002/jqs.2923
Hisamatsu S, Goto K, Imamura F (2014) Local paleo-tsunami size evaluation using
numerical modelling for boulder transport at Ishigaki Island, southern Japan.
Episodes 37:265–276. https://doi.org/10.18814/epiiugs/2014/v37i4/006
Hongo C, Kawamata H, Goto K (2012) Catastrophic impact of typhoon waves oncoral communities in the Ryukyu Islands under global warming. J Geophys
Res 117:G02029. https://doi.org/10.18814/epiiugs/2014/v37i4/006
Imamura F, Goto K, Okubo S (2008) A numerical model for the transport of aboulder by tsunami. J Geophys Res 113:C01008. https://doi.org/10.1029/
2007JC004170
Inokuchi M (1980) Grain size distribution of sediment in transit. Geophys Rev
Japan 53:769–780. https://doi.org/10.4157/grj.53.769
Inoue T, Goto K, Nishimura Y, Watanabe M, Iijima Y, Sugawara D (2017) Paleotsunami history along the northern Japan trench: evidence from Noda
Village, northern Sanriku coast, Japan. Prog Earth Planet Sci 4:42. https://doi.
org/10.1186/s40645-017-0158-1
Iryu Y, Matsuda H, Machiyama H, Piller WE, Quinn TM, Mutti M (2006) An
introductory perspective on the COREF project. Island Arc 15:393–406.
https://doi.org/10.1111/j.1440-1738.2006.00537.x
Ishimura D, Miyauchi T (2015) Historical and paleo-tsunami deposits during thelast 4000 years and their correlation with historical tsunami events in
Koyadori on the Sanriku coast, northeastern Japan. Prog Earth Planet Sci 2:16.
https://doi.org/10.1186/s40645-015-0047-4
Kato Y (1989) Yaeyama seismic tsunami (1771) in the Miyako Islands recorded in
the newly found archives “Otoiai-gaki”. Bull Coll Sci Univ Ryukyus 47:153–158
Kato Y (2000) Tsunamiisi stones at Miyako-Minna-Jima Island, the Ryukyu Islands.
Hist Earthquakes 16:203–205
Kawana T (1986) Holocene crustal movement in and around the Sekisei Lagoon
in Okinawa Prefecture, Japan: Earth Monthly 9:129-134. (in Japanese, original
title translated)
Kawana T (1989) Quaternary crustal movement in the Ryukyu Islands. Earth
Monthly 11:618-630. (in Japanese, original title translated)
Kawana T (2004) Holocene tsunami boulders in Tarama and beach rock in Kur
Islands, the Ryukyus, Japan: implication of diffraction of waves. Bull Faculty
Edu Univ Ryukyus 64:1–7
Kawana T, Nakata T (1994) Timing of late Holocene tsunamis originated aroundthe southern Ryukyu Islands, Japan, deduced from coralline tsunami
deposits. J Geol Soc Japan 103:352–376. https://doi.org/10.5026/jgeography.
103.4_352
Kench PS, Brander RW (2006) Wave processes on coral reef flats: implication forreef geomorphology using Australian case studies. J Coastal Res 221:209–
224. https://doi.org/10.2112/05A-0016.1
Kench PS, Nichol SL, Smithers SG, McLean RF, Brander RW (2008) Tsunami as agentsof geomorphic change in mid-ocean reef islands. Geomorph 95:361–383
Kitamura A (2016) Examination of the largest-possible tsunamis (level 2 tsunami)
generated along the Nankai and Suruga troughs during the past 4000 years
based on studies of tsunami deposits from the 2011 Tohoku-oki tsunami.
Prog Earth Planet Sci 3:12 https://doi.org/10.1186/s40645-016-0092-7
Kitamura A, Ito M, Ikuta R, Ikeda M (2018a) Using molluscan assemblage from
paleotsunami deposits to evaluate the influence of topography on themagnitude of late Holocene mega-tsunamis on Ishigaki Island, Japan. Prog
Earth Planet Sci:41. https://doi.org/10.1186/s40645-018-0200-y
Kitamura A, Ito M, Sakai S, Yokoyama Y, Miyairi Y (2018b) Identification of tsunami
deposits using a combination of radiometric dating and oxygen-isotope
profiles of articulated bivalves. Mar Geol 403:57–61. https://doi.org/10.1016/
margeo.2018.04.003
Komatsubara J, Fujiwara O, Takada K, Sawai Y, Aung TT, Kamataki T (2008)
Historical tsunamis and storms recorded in a coastal lowland, Shizuoka

Page 14 of 15

prefecture, along the Pacific coast of Japan. Sedimentol 55:1703–1716.
https://doi.org/10.1111/j.1365-3091.2008.00964.x
Kondo Y, Yokogawa K, Shiratsuchi T (2001) Substrate preferences and burrowing
ability of Donacidae and Mesodesmatidae (Bivalvia) on beaches ofSouthwest Japan. Venus 60(1/2):57-69. doi: 10.18941/venus.60.1-2_57
Konishi K, Matsuda S (1980) Relative fall of sea level within the past 3000 year.
Trans Proceed Paleontol Soc Japan. NS 117:243-246. doi: https://doi.org/10.
14825/prpsj1951.1980.117–243
Kugai M (2011) Foraminifera sedimentation discovered in Tomori-Motojima andSunagawa-Motojima. Bull Miyakojima City Mus 15:65–75
Lämmel M, Meiwald A, Yizhaq H, Tsoar H, Katra I, Kroy K (2018) Aeolian sandsorting and megaripple formation. Nature Phys 14:759–765. https://doi.org/
10.1038/s41567-018-0106-z
Minoura K, Imamura F, Sugawara D, Kono Y, Iwashita T (2001) The 869 Jogan
tsunami deposit and recurrence interval of large-scale tsunami on the Pacificcoast of Northeast Japan. J Nat Dis Sci 23:83–88
Minoura K, Imamura F, Takahashi T, Shuto N (1997) Sequence of sedimentation
processes caused by the 1992 Flores tsunami: evidence from Babi Island.
Geology 25:523–526
Miyazawa K, Goto K, Imamura F (2012) Re-evaluation of the 1771 Meiwa tsunami
source model, southern Ryukyu Islands, Japan. In: Yamada Y, Kawamura K,
Ikehara K, Ogawa Y, Urgeles R, Mosher D, Chaytor J, Strasser M (eds)
Advances in natural and technological hazards research, submarine mass
movements and their consequences, vol 31. Springer, Heidelberg, pp 497–
506. https://doi.org/10.1007/978-94-007-2162-3_44
Moore A, Goff J, McAdoo BG, Fritz HM, Gusman A, Kalligeris N, Kalsum K, SusantoA, Suteja D, Synolakis CE (2011) Sedimentary deposits from the 17 July 2006
western Java tsunami, Indonesia: use of grain size analyses to assess tsunami
flow depth, speed, and traction carpet characteristics. Pure Appl Geophys
168:1951–1961
Nakamura M (2009) Fault model of the 1771 Yaeyama earthquake along the
Ryukyu trench estimated from the devastating tsunami. Geophys Res Lett 36:
L19307. https://doi.org/10.1029/2009GL039730
Nakaza E, Iribe T, Tokuhisa R, Miyazato N, Inagaki K (2013) Historical andprehistorical tsunamis in the Ryukyu Islands estimated through tsunami
depositions. J Japan Soc Civil Eng B3 (Ocean Eng) 69:515–520. https://doi.
org/10.2208/jscejoe.69.I_515
Naruse H (2005) Usage and advantages of an application program “STube” forsettling tube grain-size analysis. J Sedim Soc Japan 62:55–61. https://doi.org/
10.4096/jssj1995.62.55
Naruse H, Arai K, Matsumoto D, Takahashi H, Yamashita S, Tanaka G, Murayama M(2012) Sedimentary features observed in the tsunami deposits at
Rikuzentakata City. Sediment Geol 282:199–215 https://doi.org/10.1016/j.
sedgeo.2012.08.012
Naruse H, Fujino S, Suphawajruksakul A, Jarupongsakul T (2010) Features andformation processes of multiple deposition layers from the 2004 Indian
Ocean tsunami at ban Nam Kem, southern Thailand. Island Arc 19:399–411.
https://doi.org/10.1111/j.1440-1738.2010.00732.x
Okamura Y, Nishizawa Y, Fujii Y, Yanagisawa H (2018) Accretionary prism collapse:
a new hypothesis on the source of the 1771 giant tsunami in the Ryukyu arc,
SW Japan. Sci Rep 8:13620. https://doi.org/10.1038/s41598-018-31956-8
Okinawa Prefecture Gusukube Town Board of Education (2004) Rep. TomoriMotojima remains. Rep. Tomori-Motojima remains, 78p
Omoto K (2004) Radiocarbon ages and isotope fractionations of beachrock
samples collected from the Nansei Islands, southernwest Japan. Radiocarbon
46:539–550. https://doi.org/10.1017/S0033822200035591
Omoto K (2012) Distribution of coral boulders beached by huge tsunamis andcalibrated radiocarbon ages of fossil Porites sp. of Maibahabama, SE of Miyako
Island, Okinawa prefecture. J Geography (Chigaku Zasshi) 121:1043–1051
Paris R, Wassmer P, Sartohadi J, Lavigne F, Barthomeuf B, Desgages E, Grancher
D, Baumert P, Vautier F, Brunstein D, Gomez C (2009) Tsunamis asgeomorphic crises: lessons from the December 26, 2004 tsunami in Lhok
Nga, West Banda Aceh (Sumatra, Indonesia). Geomorphology 104:59–72.
https://doi.org/10.1016/j.geomorph.2008.05.040
Pirazzoli PA, Kawana T, Montaggioni LF (1984) Late Holocene sea-level changes
in Tarama Island, the Ryukyus, Japan. Ear Sci (Chikyu Kagaku) 38:113-118. doi:
https://doi.org/10.15080/agcjchikyukagaku.38.2_113
Reimer PJ, Bard E, Bayliss A, Beck JW, Blackwell PG, Bronk Ramsey C, Buck CE,
Cheng H, Edwards RL, Friedrich M, Grootes PM, Guilderson TP, Haflidason H,
Hajdas I, Hatté C, Heaton TJ, Hoffmann DL, Hogg AG, Hughen KA, Kaiser KF,
Kromer B, Manning SW, Niu M, Reimer RW, Richards DA, Scott EM, Southon

Fujita et al. Progress in Earth and Planetary Science(2020) 7:53

JR, Staff RA, Turney CSM, van der Plicht J (2013) IntCal13 and Marine13
radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 55:
1869–1887
Richmond B, Szczuciński W, Chagué-Goff C, Goto K, Sugawara D, Witter R, Tappin
DR, Jaffe B, Fujino S, Nishimura Y, Goff J (2012) Erosion, deposition andlandscape change on the Sendai coastal plain, Japan, resulting from themarch 11, 2011 Tohoku-oki tsunami. Sediment Geol 282:27–39
Sato T, Nakamura N, Goto K, Kumagai H, Nagahama H, Minoura K (2014)
Paleomagnetism reveals the emplacement age of tsunamigenic coral
boulders in Ishigaki Island, Japan. Geology 42:603–606. https://doi.org/10.
1130/G35366.1
Sawai Y (2012) Study on paleotsunami deposits in geologic stratum. J Geol Soc
Japan 118:535–558. https://doi.org/10.5575/geosoc.2012.0063
Shimada Y, Fujino S, Sawai Y, Koichiro T, Matsumoto D, Momohara A, Saito-Kato
M, Yamada M, Hirayama E, Suzuki T, Chagué C (2019) Geological record ofprehistoric tsunamis in Mugi town, facing the Nankai trough, western Japan.
Prog Earth Planet Sci 6:37. https://doi.org/10.1186/s40645-019-0279-9
Stuiver M, Reimer PJ (1993) Extended 14C data base and revised CALIB 3.0 14C
age calibration program. Radiocarbon 35:215–230
Stuiver M, Reimer PJ, Reimer RW (2020) CALIB 7.1 [WWW program] at http://calib.
org, accessed 2020-5-28
Szczuciński W (2012) The post-depositinal changes of the onshore 2004 tsunami
deposits on the Andaman Sea coast of Thailand. Nat Hazards (Dordr) 60:115–
133. https://doi.org/10.1007/s11069-011-9956-8
Takashimizu Y, Urabe A, Suzuki K, Sato Y (2012) Deposition by the 2011 Tohokuoki tsunami on coastal lowland controlled by beach ridges near Sendai,
Japan. Sediment Geol 282:124–141
Takeda H, Goto K, Goff J, Matsumoto H, Sugawara D (2018) Could tsunami risk be
underestimated using core-based reconstructions? Lessons from ground
penetrating radar. Earth Surf Process Land 43:808–816. https://doi.org/10.
1002/esp.4282
Watanabe M, Goto K, Imamura F, Hongo C (2016) Numerical identification oftsunami boulders and estimation of local tsunami size at Irabuma reef ofIshigaki Island, Japan. Island Arc 25:316–332. https://doi.org/10.1111/iar.12115
Yamada M, Fujino S, Goto K (2014) Deposition of sediments of diverse sizes by
the 2011 Tohoku-oki tsunami at Miyako City, Japan. Mar Geol 358:67–78.
https://doi.org/10.1016/j.margeo.2014.05.019
Yamamoto M (2008) Trace of earthquake and tsunami in Ishigaki Island, Yaeyamaarchipelago. Archaeol J 577:9–14
Yamamoto M, Souda T, Kawana T (2009) Trace of earthquake and tsunami in
Ishigaki Island. Archeol Q 106:91–92
Yamano H, Kayanne H, Yonekura N (2001) Anatomy of a modern coral reef flat: arecorder of storms and uplift in the late Holocene. J Sedim Res 71:295–304.
https://doi.org/10.1306/082900710295
Yawsangratt S, Szczuciński W, Chaimanee N, Jadgodziński R, Lorenc S, Chatprasert
S, Saisuttichai D, Tepsuwan T (2009) Depositional effects of 2004 tsunami andhypothetical paleotsunami near Thap Lamu navy base in Phang Nga
Province, Thailand. Polish J Environ Stud 18:17–23
Yazaki K (1977) Geology of the Taramashima District. Quadangle Series, Scale 1:
50,000, Miyako-jima (19) no. 5, Geological Survey of Japan, Kawasaki

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.

Page 15 of 15