Kurume History Walks
M i n od a n s oNo.1 The Mino Faults 水縄断層

The Mino Faults (Mino danso) mark the northern border of the Mino Mountains with cliffs and pass throughthe cities of Kurume and Ukiha. It is about 20 kilometers long and is composed of ten minor faults that run
diagonally or parallelly.
These dextral normal faults with the north-dipping side are estimated to move averagely 10 centimeters to1 meter per a thousand years. These fault scarps show the continuous dissection induced by a steep-sided valley.
The Mino Faults were designated a National Natural Monument on July 28th, 1997.

Rough positions

The Mino Faults

Location of the Mino Faults

1Kurume History Walks / No.1 The Mino Faults

Fault-drilling research on the Yamakawa-Yamada Remains
In October 1993, we found several outcrops, many cracks, the lithospheric flexures and the traces of theliquefaction phenomenon and the sand boil phenomenon, as a result of the drilling research under the directionof Professor Matsuda Tokihiko (faculty of Science, Kyushu University; professor emeritus of Tokyo University),
Dr. Sangawa Akira (senior researcher in Agency of Industrial Science and Technology of the Ministry ofInternational Trade and Industry), Prof. Chida Noboru (faculty of Education, Oita University).
We also verified the four events: the first happened about twenty-five thousand years ago, before theaccumulation of the AT volcanic ash layer by an eruption of the Aira caldera of Kagoshima, and the other threetimes after that.
In conclusion, we defined the Mino Faults to be the source of the Tsukushi no Kuni Earthquake mentioned
in the article Dec. 678 CE of “The Chronicles of Japan (Nihon Shoki)”, comparing other following facts that wefound, and the materials and the traces of remains in Chikugo province.
- In the deposit that filled the cracks caused by the last event, a Haji pottery (unglazed earthenware of the 3rd
to the 12th century) was discovered.
- The upper layer that covers the above-mentioned included the artifacts of the Kamakura period (1185-1333).

Yamakawa-Maeda Remains(The faults run along the edge of a mountain)

Slippage of the black humus layer and the orange AT
volcanic ash layer.

This crack in which a Haji pottery was unearthed is theconclusive evidence that was the source of theTsukushi no Kuni Earthquake.

A humus layer that normally accumulates horizontally wasgreatly deflected.

2
Kurume History Walks / No.1 The Mino Faults

The Tsukushi no Kuni Earthquake in 678“This month, in Tsukushi Province, the earth moved exceedingly. The earth fissured
two jou (an old Japanese unit : one jou is equal to three meters) in width, more than three
thousand jou (nine thousand meters) in length. Many farmhouses in each village collapsedand broke down. At that time , a peasant house had been upon a hill. In the evening whenthe earth moved, the hill crumbled down and the house moved away. However, the house
did not get damaged at all. The inhabitants did not know that the hill fell and their house
moved. Then only after the dawn, they got hugely surprised. ”

This article is from “The Chronicles of Japan” which tells that in December 678 in Tsukushi Province(Tsukushi no Kuni, today’s Chikuzen and Chikugo Province), there was a huge earthquake that caused heavydamage. The fault-drilling investigation, mentioned in the previous page, revealed that the seismic center was
the Mino Faults and that it was the latest activity — it occurs in about 8000-12000 years intervals.
At the ruins of Chikugo Province of which Kurume takes part, the cracks and the traces of theliquefaction phenomenon and the sand boil phenomenon were found in great numbers. They proved that it
was as large as the Kobe Earthquake in 1995. Moreover, this earthquake is the oldest that is mentioned in awritten record, and of which the occurrence year is known.
Traces in the city

The trace of the liquefaction phenomenon and the sandboil phenomenon at the remains of ancient facilities of thenational administration and the military (Chikugo Kokufu inAikawa)

The clay wall was re-rammed after the collapse due to theliquefaction (Kamitsu Dorui Ato in Kamitu)

The sinking due to the crack (Shindo Remains in MiiHatazaki)

The cracks (black lines) tear a pit dwelling house and a bowl
turned down on the floor in the Yayoi period (1000 BCE300) (Higashigarasu remains in Yasutake)【 Descriptions of terms 】-3Kurume History Walks / No.1 The Mino Faults

Active fault: The fault is considered to be repeating the movement through the late Quaternary Period fromthe last hundreds of thousands of years to the present time, and to become again active in the future.
Fault types:

N o rmal f aul t ( inc l ine d f aul t)

R ev ers e d f aul t ( inc l ine d f au l t)

L ef t-late r al f au l t

Ri gh t-l ate r al f au l t

Seismic Intensity Scale (Shindo) : The scale used in Japan to categorize the intensity of local groundshaking caused by earthquakes. Each observation site judges it by bodily sensation, state of shaking objects
and damage, and so on. The scale is divided into ten classes from 0–4, lower/upper 5, lower/upper 6, and 7.
Seismic magnitude scale : It describes the overall size of an earthquake evaluated according to the recordof the seismometer. It is indicated by M, in general. Each unit of magnitude represents a nearly 30-foldincrease in the seismic energy of an earthquake so that an earthquake of M7 is equivalent to one thousand
earthquakes of M5.
Liquefaction phenomenon and sand boil phenomenon: When a sand layer with high water content is

hit by a large earthquake, it becomes squishy (Liquefaction). Furthermore, if upon the sand layer there is aclayey layer that functions as the lid, the water, and the sand tear the clayey layer, and these spurt out to thesurface (Sand boil). When the Niigata Earthquake occurred in 1964, some high-rising buildings broke down orleaned.
Hibikinada Sea
Suonada Sea
Genkainada Sea

Kokurahigashi
Fault Zone

FukuchiyamaFaults Zone
Umi Fault

Nishiyama Faults ZoneKego Faults Zone
Hygatoge-Okasagi
Faults Zone

Cultural Properties Protection Department
Mino Faults Zoneof Kurume
Address 15-3 Jonan Kurume Fukuoka Japan830-8520
Tel 0942-30-9225
Ariakekai Sea

Date of revision: March 8th, 2013
Translated in May 2020

Main active faults in Fukuoka (Red lines)-4Kurume History Walks / No.1 The Mino Faults