2024年1月1日午後4時10分に発生した2024年能登半島地震（M 7.6）に伴って能登半島北岸に沿って海岸線の顕著な隆起が見られた．とくに輪島市門前町鹿磯周辺では漁港防波堤壁に残された旧汀線を示す海棲生物遺骸の分布高度に基づき3.8～3.9 mの隆起が確認された（宍倉ほか，2024）．

 鹿磯・川河口から黒島・高島を経て藤浜にかけての約4.5 km連続する海岸に沿った浅海底は，2024年能登半島地震に伴って隆起した．写真中央の黒島漁港は完全に干上がっており，少なくとも3 m以上の隆起が確認された．砂浜海岸（写真中央下より）に位置する八ヶ川河口部では浅海底が隆起し．海岸線が150 m程度海側へ前進した．新旧の汀線間には現汀線よりの微高地（明灰褐色部）とその内陸側に伸びる溝状の低地（暗灰褐色部・小水面部）が汀線に並行して認められ，外浜を構成するバーと沿岸トラフ（武田，2017）が隆起したものと考えられる．黒島漁港以南の海岸部にも同様な隆起に伴う外浜部の離水が観察される．

 地震性隆起海岸の例は，岩石海岸に残された波蝕棚やノッチの存在から各地で認識されてきたが，砂浜海岸の隆起例の記載は少なく，また今後の波浪による浸食で長く保存されないと予想されることから，ここに紹介する次第である．

 写真撮影日：2024年5月22日　撮影高度：約300 m．

（八木浩司・佐藤昌人・山田隆二）

 The latest geological and geotectonic aspects of Tokunoshima Island in Central Ryukyus are reviewed. The pre-Quaternary basement geology of the island is two-fold; i.e., the Cretaceous accretionary complex (Amagidake and Omo units) and the high-grade metamorphic unit newly named the Inokawadake metamorphic complex (IMC). The former is correlated with the northern subbelt of the Shimanto belt in SW Japan. The IMC is composed of high-grade metamorphic rocks composed of pelitic–psammitic schists, with minor lenses of serpentinite and “dioritic gneiss” with Paleoproterozoic (ca. 1.8 Ga) zircons. In the southern half of the island, the IMC structurally overlies the Cretaceous AC as a klippe, which is separated probably by a subhorizontal fault. The IMC suffered from high-grade metamorphism up to the amphibolite facies, which is extremely rare in the Shimanto belt. A new geotectonic unit, the Tokunoshima belt, is newly proposed for the area of the IMC, which is limited to a mountainous domain in southern Tokunoshima Island. Based on the youngest detrital zircon U–Pb ages (ca. 60 Ma) from psammitic schists, the metamorphism of the IMC probably occurred in the Paleocene or later. Possible sites for the Paleocene or later heat source may include the San-in (Paleogene batholith) belt in SW Japan on the north and/or an unknown collided island arc system from the south.

 Inoh Tadataka (1745-1818) drew the first Map of Japan based on a scientific survey. The maps forming Inoh's Map are classified into large-scale map (Daizu 1/36000), medium-scale map (Chuuzu 1/216000), and small-scale map (Shouzu 1/432000). Each map forming Inoh's Map was drawn from manuscript maps called Shita-ezu (1/36000), Yosezu (1/36000), Chuuzu-shitazu (1/216000), and Shouzu-shitazu (1/432000). Shita-ezu is a draft map plotted from the results of a survey carried out over one day. Yosezu is a manuscript map created by combining several Shita-ezu. Chuuzu-shitazu is a manuscript map reduced to one-sixth scale from Yosezu. Shouzu-shitazu is a manuscript map reduced to one twelfth from Daizu, which is compiled from a number of Yosezu. Concerning the mapping process used to draft Inoh's Map, a theory of Ohtani, R. (1917) has been most fundamental and influential in studies of Inoh's Map. According to this theory, Shita-ezu was plotted from the results of a daily survey and Yosezu was compiled from several Shita-ezu. Furthermore, he states that for the Tsukitehon, a Daizu manuscript was compiled from several Yosezu, and then Yosezu were graphically reduced and compiled to create Chuuzu, which in turn was reduced to Shouzu. On the other hand, recently, Nogami, M. (2021, 2022) rejected Ohtani's theory and concluded that Inoh's Map was drawn by calculating the coordinates of survey points, and map reduction was also based on calculations. In this study, it is concluded that the process of drawing Inoh's Map is divided into two flows. One is the reduction process from Yosezu to Chuuzu, the other is the reduction process from Yosezu to Daizu and from Daizu to Shouzu. The terminal survey points on Shita-ezu were plotted by calculating coordinates, which means the east-west/south-north component distance on a map. However, the survey points between the terminal survey points were then plotted graphically on Yosezu. It is added that the plotted areas of each Yosezu and each Chuuzu-shitazu correspond. Therefore, after Yosezu was drawn by combining Shita-ezu, Chuuzu-shitazu were drawn sequentially by reducing Yosezu. Regarding Shouzu-shitazu, it is clarified that the framework of the plotted area of Shouzu-shitazu is the same as that of Daizu. Consequently, Shouzu-shitazu were drawn by reducing to one twelfth the area of the same framework as Daizu after the frameworks of Daizu were decided.

 The Mikata Five Lakes and their surrounding lowlands in the northern part of the Kinki district, central Japan, have been formed due to the activity of the Mikata Fault Zone extending north to south along the eastern margin of the lake area. The Nakayama lowland northeast of Lake Mikata is located closest to the fault zone and its detailed subsurface geology may be a key to understanding the late Quaternary activity and structural development of the Mikata Fault Zone. Three new cores drilled in the lowland are analyzed and sedimentary facies analysis, radiocarbon dating, tephra analysis, and sulfur analysis are conducted to establish the chronology and correlation of the core sediments, and to reconstruct paleoenvironmental changes since the Marine Oxygen Isotope Stage (MIS) 6. Based on sedimentary facies and results of the analysis, four sedimentary environments are deduced as follows: 1) fluvial deposition by the Paleo-Hasu River flowing through the lowland during MIS 6, 2) coastal conditions due to marine transgression during MIS 5e, 3) fluvial deposition until MIS 3, and 4) marshy environment after the beginning of MIS 3 at around 50 ka. Isochronous horizons of subsurface sediments in the lowland indicate accumulated deformation due to the activity of the blind fault, the strike of which is evaluated to be WNW–ESE, as opposed to the previous estimation of N–S. The upper limits of marine-influenced deposits during MIS 5e reveal large differences in relative elevation of 71-75 m between Lake Mikata and the Nakayama lowland. This may have been caused by the activity of another blind fault between the two areas. The two blind faults are considered to be the southeastern extension of the Hiruga fault, suggesting the structural development of the Mikata Fault Zone since MIS 6.

 It has become clear that repeating earthquakes (repeaters) prevalently occur not only at plate boundaries but also in the continental crust and subducting slabs, coexisting with regular earthquakes (Nakajima and Hasegawa, 2023). Based on this prevalent occurrence of repeaters, previous research is reviewed and the generation mechanism of inland crustal and intraslab earthquakes and its seismological and tectonic implications are discussed. Furthermore, based on this discussion, an extended fault-valve model for shallow large earthquakes is proposed. Repeaters in the continental crust and subducting slabs are interpreted to occur as repeated slips of isolated asperity patches caused by stress loading due to aseismic slips in the surrounding stable regime, similar to those at plate boundaries. Regular earthquakes are slips of asperity patches due to surrounding aseismic slips as well, which indicates that shallow inland earthquakes and intraslab earthquakes have the same generation mechanism as interplate earthquakes. This suggests that aseismic slips occur extensively and more universally within the continental crust and subducting slabs than was previously recognized, which further suggests that aseismic slips play an important role in tectonics in subduction zones such as deformation of the island-arc crust. High pore fluid pressure is assumed to be the main cause of aseismic slips. The conventional fault-valve model (Sibson, 1986, 1990) is modified for shallow large earthquakes as intermittent aseismic slips (slow slip events) are thought to occur frequently around asperity patches that cause large earthquakes. Thus, aseismic slips also play a fundamental and important role in the earthquake cycle, and are estimated to increase significantly in frequency immediately before large earthquakes. This process helps to enhance the stress applied to asperity patches that cause large earthquakes. The signals of the aseismic slips are thought to be weak, so they have rarely been detected to date. It is important to develop new methods that can detect such weak signals of aseismic slips.

 Since 1907, Chichi-jima, Ogasawara (Bonin) Islands, has been experiencing a drying trend because of an increase in annual mean temperature and a decrease in annual precipitation, which are particularly pronounced during the summer. However, based on precipitation data prior to 1906, annual precipitation may not have decreased consistently but rather may have fluctuated periodically. Data from the Chichi-jima Meteorological Observatory for the period 1969-2022 are used to clarify trends in annual mean temperature and precipitation, as well as the current drying trend status. The annual mean temperature on Chichi-jima has risen since 1907. The annual precipitation has been cyclical, increasing from 1976 to 2014, indicating that the drying trend on Chichi-jima may be diminishing, including in the summer. Increased precipitation in March, September, and October has contributed to the overall increase in annual precipitation. Typhoons are identified that passed within a 500 km radius of the Chichi-jima Meteorological Observatory as having brought precipitation to Chichi-jima. We found that increased precipitation in October was caused by typhoons. The characteristics of October typhoons that are identified, such as a poleward shift of the maximum tropical cyclone intensity and reduced typhoon velocity, are in accordance with those identified in previous studies that examined future changes in typhoons under global warming.

 Drone photogrammetry is carried out with an SfM-MVS analysis to obtain detailed topographic data and to make digital elevation models (DEMs) on a peninsula on the eastern shore of Lake Miwa, Ina City, Nagano Prefecture, where the topographic features and geological boundaries of the Median Tectonic Line are well observed. In the area covering the entire peninsula with several hundred-meter scales, the resolution of the DEMs produced by drone photogrammetry in this study is higher than that of 5-10 m mesh DEMs available free of charge. At the Mizoguchi outcrop on the southern edge of the peninsula, which is exposed on a several tens of meters scale with the clear lithological boundaries of the Median Tectonic Line, DEMs obtained by drone photogrammetry show a higher resolution than a 0.5 m mesh DEM constructed from airborne laser scanning. These results demonstrate the high utility of drone photogrammetry for a topographic analysis of an area within a few hundred meters of scale. In addition, the orientation of the lithological boundary at the Mizoguchi outcrop, estimated based on DEM images, agrees with that measured at the outcrop using a hand-held clinometer. This indicates that an analysis of geological structure using drone photogrammetry is practically feasible. Considering the advantages of cost and portability, it is suggested that drone photogrammetry may be a suitable approach for structural analyses in geological field surveys that require investigations in harsh environments such as steep mountain areas.