大分県には84ヶ所，総数にして400体ほどのが存在しており，日本全国の8割近くのが集まっているといわれている．これまでの湧水調査の中でには必ずといってよいほど湧水が見られたので，便利な指標として利用していた．従来，の造立は密教との関係を指摘され，深い信仰心から造立されたといわれていたが，水の存在からをみた研究は知られていない．石像文化財保護の観点からみると，に湧水が存在する事は風化が早まる可能性があり好ましい事ではない．にもかかわらず，大分県のに湧水が存在する事は，そこに何か理由があるのではないかと考え，と湧水の悉皆調査を開始した．これまでに54ヶ所のを訪れ，湧水の存在を確認した結果，確実に湧水が存在するものが35ヶ所，湧水跡のみられたものが16ヶ所，存在しないもの3ヶ所となった．未調査のが30ヶ所ほどあるものの，９割以上のに湧水が確認された．しかも湧水のない3ヶ所のは，移動可能な石仏と横穴式墳墓に彫ったであった．従って，調査したには必ず湧水が存在するといってよい．における湧水の存在理由は自然科学的には次のように説明できる．大分県には9万年前に噴火した阿蘇の溶結凝灰岩が大野川流域を中心に堆積し，各地に垂直の懸崖を形成しており，の格好の造立地を提供している．溶結凝灰岩はよい帯水層ともなっているので，多くの湧水が見られる事も確かである．に湧水が存在するその他の理由としては，制作者の硯水(作業の合間にとる水)とへの閼伽水等が考えられる．製作現場での実質的な問題として，飲み水がなければ長期間にわたる製作は不可能といってよいだろう．また，閼伽水は神仏に毎日欠かさず供えるもので，近くに水場がなければならない．閼伽は密教と密接な関係を持つ言葉であり，に塗られている赤い塗料である水銀から作る朱(しゅ，アカ)にも通じている．しかも大分県には水銀産地である事を示す丹生地名が3ヶ所も知られている．このことから，大分県のは密教の影響を強く受け，水の存在に対する感謝の念と実用的な問題から，湧水の存在する場所に造立されたと考えるべきである．また，大分県外でもに湧水が存在する例は多く，海外の(中国のキジルや莫高窟など)にもその例が見られる事は特筆すべきであろう．

抄録全体を表示

  In Iwaki City, Fukushima Prefecture, an important prefectural road (Route 26) was blocked by rock fragments from hill slope at 11:00 pm on August 24, 2019. This slope movement was unique in that typical triggering factors, such as heavy rain or an earthquake, did not occur on the day of the event. We performed an urgent field survey on the slope movement on August 27, 2019. The results are as follows : 1) The slope movement occurred on a hillside slope comprising Miocene tuffaceous sandstone and mudstone. The rocks have well developed joint faces and weathering. 2) Blocks “a” and “b” consisted of surface slope failure landforms. The movement directions of the slope failures were controlled by the geological structure, especially dip and strike. Block “c”, located above Blocks “a” and “b”, consists of subsidence landforms. Interviews with residents revealed that artificial caves existed beneath Block “c”. 3) The slope movement involved the subsidence of Block “c” having been induced by roof falling in the artificial caves. The surface slope failures of Blocks “a” and “b” occurred with the subsidence of Block “c”. Rock-cliff Buddha statues occurred on the slope of Block “a” before the slope movement. Photographic material revealed small bedrock displacements in and around the statues. These geological structures suggested that the stress of internal rocks were triggers of the slope movement August 24, 2019.

抄録全体を表示

Deterioration of the rock-cliff Buddha sculptures (Magaibutsus) in Oita Prefecture, Japan, was evaluated by using portable magnetic susceptibility meter and moisture meter. Investigation was carried out for the Magaibutsus of Sugao, Ogata Miyasako, Inukai, Usuki, Monzen and Oita Motomachi. These Magaibutsus were carved in the rock-cliff of the Aso-4 pyroclastic flow sediments.
There is a tendency that magnetic susceptibility is high (more than 7×10⁻³SI unit) for the non-deteriorated Magaibutsus preserving pigments on the surface, and moisture content for those Magaibutsus is low (less than 3%). On the other hand, deteriorated Magaibutsus have low magnetic susceptibility and high moisture content. The results suggest that the deterioration proceeds in the following order: Ogata Miyasako, Sugao<Inukai, Usuki, Monzen<Oita Motomachi. The relationship between magnetic susceptibility and moisture content reveals that magnetic susceptibility is more sensitive than moisture content to deterioration of the Magaibutsus.
Deterioration of the Magaibutsus seems to be mainly attributable to salt crystallization and freeze-thaw cycle.

抄録全体を表示

Daifukuji Temple rock-cliff Budda sculpture which is located halfway up on the hill near the coast of Tateyama, Chiba Prefecture was carved in 8th century on the Neogene andesitic tuff and tuff breccia alternated bed. It is sheltered by a beautiful wooden construction.
The Neogene andesitic tuff and tuff breccia are composed chiefly of augite, hypersthene, hornblende, plagioclase, and volcanic glass with subordinate amounts of fine-grained magnetite, pyrite (probably biogenic), hematite and limonite.
The surface of Budda sculpture is covered by a thick, up to several mm, crust or scab composed chiefly of minerals such as gypsum, thenardite, epsomite, mirabilite with minor amounts of halite, sylvite, aragonite and copiapite.
Rain water penetrates into the rock of the hill where sculpture is located and the water easily comes out after interaction with rocks and evaporates from the surface of rock-cliff. The water coming out from rock mass has high contents of Ca, Na, Cl, HCO₃ and SO₄ with subordinate amounts of K and Mg.
Gypsum-rich scab or crust was formed by the evaporation of such type of groundwater on the rock-mass surface. The growth of thus formed scabs or crusts and their falling off must be major reasons why the sculpture has been decayed so badly as shown by Fig 4.
Modes of occurrence of gypsum-rich scabs and indoor experiments using bore-hole cores taken from the Neogene volcanogenic sediments mass on which the sculpture was carved indicate that the increase in the thickness of the gypsum-rich scabs is unbelievably fast, probably more than 0.15mm/year.
The repeated cycle of the growth of gypsum-rich scab or crust on the surface of Neogene volcanic sedimentary rock mass and their falling off should be stopped to prevent the forth decay of this Budda sculpture. The best ways to solve this problem are considered to be (1) to minimize the down permeation of groundwater from the top surface through interstitial void and joint of Neogene volcanogenic formation by making open drainage space at the above and/or back side of the rock-cliff sculpture or by covering the top surface of the hill by unpermeable facing and (2) to keep the humidity of the room of rock-cilff sculpture as high as possible to minimize the evaporation of water extracted from the surface of the sculpture.

抄録全体を表示

The group of Buddhist stone images of Oya Hill which is in the suburbs of Utsunomiya City is the oldest one among cave statures in Japan (made in the 9th century). The stone images are carved on the wall surface of the large cave in porous green tuff.
At the present time, the stone images are considerably damaged as a result of active weathering through the centuries.
So the National Commission for Protection of Cultural Properties is intending to repair the damage and to check further deterioration.
The author has made clear that the active weathering is caused by capillary water which derived from the ground water, and has found that the elimination of the ground water is effective for the conservation of the stone images.

抄録全体を表示

Rock-cliff Budda sculptures of Odaka Town, Fukushima Prefecture, Japan were carved about one thousand years ago on the Neogene dacitic tuffaceous sedimentary rocks.
These sculptures have been badly decayed by (1) the formation of scabs composed chiefly of gypsum, epsomite and thenardite with subordinate amounts of kogarkoite, langbeinite, zoherite, hydroglauberite, starkeyite, jurbanite, loeweite, hexahydrite, alunogen, mirabilite, glauberite, syngenite, hemihydrite and sylvite at the surface of the sculptures by the evaporation of groundwater percolated through the voids and joints in the Neogene volcanogenic sedimentary rocks and (2) the exfoliation of the these scabs and near-surface part of Neogene sedimentary rocks, particularly due to the heaving during the freezing-thawing cycle of seeped groundwater in winter season.

抄録全体を表示

Evaporites were observed on a surface of the historical brick in the Museum Meiji-Mura. Aphthitalite (K₃Na(SO₄)₂), thenardite (Na₂SO₄), trona (Na₃H (CO₃)2•2H₂O), and thermonatrite (Na₂CO3•H₂O) were identified as the main component minerals of the evaporites. These evaporates are considered to be formed in these less than a few decades under the humid climate of Japan. Because no sulfur-containing minerals can be found in the plaster nor in the bricks, it is thought that aphthitalite and thenardite were formed by the interaction between bricks and acid rain water with SO₄^2-ion. Experimental results support this idea; rain water-brick interaction has produced sulfate, whereas distilled water-brick interaction has not produced sulfate. To conserve this brick cultural property, it is desirable that roofs and gutters would be improved to prevent bricks from impregnation of rain water.

抄録全体を表示

In the ancient period in Corea, especially both in the Sam Guksidai (6, 7 centuries) and in the Great Silla Period (8, 9 centuries) were produced the most splendid Buddha-images of stones. Many techniques were developed-those of the round, the relief, line engraving, etc.. Up to now, however, we cannot say that we have considered sufficiently the relation between these techniques and modes of Buddha-images. Ancient Corean people had a special belief in the Rock (especially the granite) which they adorated as the constituent of the Earth. The more they were aware of the existence of the God, the more keenly they wished to perceive him in the concrete form. Incidently in the 6th century Buddhism was transmitted to the Corean Peninsula, so they, following the image of Buddha, gave their God a concrete form. They obtained the way to make their God appear in this world. At first the image was formed by line engraving on stone. It corresponded to the way how they felt the existence of God. He was looked at as a shadow-image. Secondly the image was appeared as the carving relief. They wanted a more or less concrete image of their God or Buddha. At last the image was appeared as the complete round sculpture. The God or Buddha, separated from the inner world of the rock or stone, entered into the real existence in this world. And these three stages are found in the remains of the Gulbusa-temple.

抄録全体を表示