Following the 1988-1995 major activity, a series of magmatic eruptions began on November 25, 2014 at the Nakadake first crater of Aso Volcano in central Kyushu, southwestern Japan, continuing until May 3, 2015. The 2014-2015 eruptive activity at Nakadake first crater was dominated by continuous ash emissions from a vent 20-30 m across formed near the center of the crater, although strombolian eruptions were recognized immediately after the activity began.
(Photograph & Explanation: Yasuo MIYABUCHI; January 13, 2015)
A tsunami caused by the Great East Japan Earthquake on March 11, 2011, devastated coastal areas of Sanriku in northeastern Japan. Because Sanriku had been damaged repeatedly by tsunamis in the past, local governments and residents attempted to protect coastal communities by building large tide embankments, raising the ground, and relocating houses to higher ground. Geographical studies on the disaster mainly focus on the vulnerability of regional communities to disasters and on measures taken to reduce hazard risks. Recently, geographers have begun to use the concept of resilience to examine the process of reconstruction. This study examines factors that contribute to the high level of resilience of a local community impacted by the Great East Japan Earthquake in March 2011 by presenting the case of the Moune district of Kesennuma City, Miyagi Prefecture. An adaptation process model of local communities is proposed to examine a local community impacted by a disaster. Three time-series phases consider the pre-disaster period, evacuation and refugee period directly after the disaster, and the planning period of the group relocation project. Resilience in the context of geography is an adaptation process in which a local community is reconstructed after a disaster to achieve a new phase of low vulnerability. The Moune district is examined from interviews and document surveys carried out from 2012 through 2016. It is suggested that resilience functioned successfully: people in the local community quickly agreed to resettle to a new residential quarter on higher ground and the resettlement project was completed successfully. The social capital formed in the context of local history and community based on the traditional culture and the economy contributed to forming a high level of resilience to the tsunami disaster. Geographical studies on resilience may facilitate an accurate understanding of tsunami-prone areas.
Shinjima (Moeshima) Island in Kagoshima Bay, southern Kyushu, Japan is noteworthy in volcanology, paleontology, and palaeo-environmental studies, because the island emerged from the bay bottom during volcanic activity at Sakurajima in 1780 AD. As a result, Holocene and late-Pleistocene deposits of the bay including muddy deposits, a thick pyroclastic flow deposit, and prominent molluscan shell beds occur on this island. Several tephras included in the bay deposits are critical for deriving their precise chronology. The chronology of those tephras was constructed on the basis of their identification using both refractive indices and major element compositions of constituent glass shards, as well as stratigraphic features in the field. Tephras identified in sediments from younger to older are Sakurajima-Taisho (Sz-Ts)-/P1, Sakurajima-Sueyoshi(Sz-Sy)-/P11, Yonemaru, Sakurajima-Uwaba(Sz-Ub)-/P12, Sakurajima-Takatoge3 (Sz-Tk3)-/P13, Sakurajima-Satsuma (Sz-S)-/P14, and Shinjima pyroclastic flow deposit. The Shinjima pyroclastic flow deposit, which differs stratigraphically between northern and southern areas of Shinjima Island, is the same tephra in the two areas, and is estimated to be c. 13,000 cal BP in age. The pumice clasts of Sz-Sy/P11 provided a suitable environment for the habitat of a prominent shell bed (Moeshima Shell Bed) composed mainly of Neopycnodonte musashiana. Sz-Ub/P12, Sz-Tk3/P13, and associate secondary deposits of Sz-S/P14 indicate that the deposit was formed in the last 13,000 cal BP. The chronology of the deposits of Shinjima Island is based on the findings of stratigraphic positions and ages of those tephras, and 14C ages obtained in this study, and will play an important role when examining the palaeo-environmental history of Kagoshima Bay since the last deglaciation.
Several volcaniclastic deposits discovered at the foot of the eastern wall of Aso caldera, central Kyushu, southwestern Japan, are divided into two types: lahar deposits (Lh1-Lh5 in descending order), which contain abundant subangular to subrounded lithic clasts ( 3.5 m in diameter) set in a sandy to silty matrix, and debris avalanche deposits (DA1 and DA2), which include numerous plastically deformed fragments of tephra (ash and scoria) and soil layers in a homogenous silty to clay matrix. DA2, which underlies a paleosol dated at 5.4 ka (calibrated 14C age), is the largest volcaniclastic deposit observed in the section (more than 2.5 m thick and about 70 m wide). Because the debris avalanche deposits display no evidence that they were transported by water, they are likely to have originated from landslides triggered by intense earthquakes. Tephra chronology and 14C-dating on paleosols along the succession suggest that lahars occurred once over 900 years (6.3-5.4 ka), three times over 1400 years (5.4-4 ka), once over 400 years (4-3.6 ka) and twice (including the 2012 lahar) in the last 3600 years. This evidence indicates that the lahars occurred at an interval of 400-1800 years. In contrast, two debris avalanche deposits exist in the same succession spanning the last 6300 years. Including landslides and associated debris avalanches triggered by the 2016 Kumamoto earthquake (Mj 7.3), landslides generating debris avalanches in the Aso caldera occurred at least three times in the last 6300 years. This may suggest the frequency of large earthquakes triggering debris avalanches in the central Kyushu region, which has many active faults.
The transformation of Kusatsu Onsen spa resort in Gunma prefecture, at the margins of the Tokyo metropolitan area, is elucidated. The use of the Internet by the accommodation industry is analyzed based on the dependence of the area on travel agencies in both information distribution and supply and demand phases. These specifically identify the possibilities and limits of region-led tourism development. The results are as follows. Many accommodations at Kusatsu Onsen independently use travel agencies in the information distribution phase. On the other hand, in the supply and demand phase, both dependence on and independence from travel agencies are confirmed. Through the use of the Internet in the accommodations, the possibility of promoting region-led tourism development at Kusatsu Onsen is increasing as a whole in the information distribution phase. This possibility in the supply and demand phase is due more than ever to the management conditions and management abilities of the each accommodation. Using the Internet as an opportunity, each accommodation tries to overcome the disadvantages of its management conditions and create tourism services. Individual tourists with diverse and advanced tourism demand gather at spa resorts at the margins of the Tokyo metropolitan area. The area responds to tourism demand in the Tokyo metropolitan area, given changing relations of dependence between travel agencies and the areas they serve against the backdrop of the development of personal travel and information socialization. On the other hand, local organizations are attempting to form the functions of travel agencies; however, they are not succeeding. Accommodation owners call for organizations to act as the cores of local networks to promote the management and marketing activities of each accommodation. As described above, at Kusatsu Onsen, a situation is created for continuously providing non-daily life services to the tourism market in the Tokyo metropolitan area, and local accommodations and organizations produce tourism resources independently. In the information distribution phase, the accommodations and local organizations form an environment where each can effectively communicate its own attractions, and the possibility of region-led tourism development is widely acknowledged. On the other hand, in the supply and demand phase, such a possibility can be somewhat recognized. Some accommodations have a trend of great dependence rather than a tendency of becoming independent of travel agencies, and it is also difficult for local organizations to play the roles of a travel agency. These factors suggest the limits of region-led tourism development.
To reconstruct the already lost tectonic framework of the Early-Middle Paleozoic arc-trench system, U–Pb ages of zircons are analyzed using LA-ICPMS from mid-Paleozoic arc-related granitoids and sandstones in the Kurosegawa belt, SW Japan, particularly from western-central Kochi prefecture in Shikoku where the belt attains the greatest width with the greatest variations of rock types. Dated samples include Yokokurayama granite, Ohira quartz diorite, basal sandstone of Lower Silurian Gomi Formation above the Yokokurayama granite, and basal conglomerate/overlying sandstone of Upper Devonian Ochi Formation from the Yokokurayama lenticular body in western Kochi prefecture, as well as Konomori quartz diorite from the Konomori lenticular body in Kochi city. The samples of Yokokurayama granite yield many zircons of ca. 451-439 Ma (latest Ordovician to earliest Silurian) U–Pb ages, whereas Konomori quartz diorite have only one grain, plotted on Concordia curve, of ca. 382 Ma (Late Devonian). The former ages confirm Ordovician–Silurian arc magmatism in Japan, whereas the latter identify late Devonian magmatism for the first time. The unconformably-covering sandstone of the Gomi Formation naturally contains abundant detrital zircons of almost identical ages to the underlying granite. The basal conglomerate of the Ochi Formation contains detrital zircons from Ordovician–Silurian granitoids and also some Mesoproterozoic (1400-1200 Ma) ones, suggesting an intimate link between Paleozoic Japan and the South China block. These new zircon ages from the Kuroseagawa belt suggest that a unique magmatism occurred in the forearc of Paleozoic Japan to emplace I-type granitoids in shallower crust, possibly by the subduction of a young oceanic plate. This further suggests that the Silurian mid-arc domain changed into a forearc setting with significant tectonic erosion/removal of preexisting fore-arc crust.
The development of observational, theoretical, and experimental studies on seismology in Japan from 1945 to 1965 is described. Damage caused by the Fukui earthquake in 1948 and its nature was surveyed from different perspectives. This survey later became the model for comprehensive surveys of major earthquakes. After the Fukui earthquake, observations on micro-earthquakes were carried out with sensitive electromagnetic seismographs. These studies confirmed the Gutenberg-Richter's formula and the Ishimoto-Iida's formula for small earthquakes. Explosion seismic observations have also been conducted by the Research Group for Explosion Seismology since 1950, and crustal structures in Japan have been precisely inferred from those observations. The Earth's interior was investigated by analyzing the attenuation of body waves in the 1950s, and surface waves and free oscillations of the Earth also began to be used to investigate the Earth's interior in the 1960s. Studies on earthquake mechanisms attracted great attention from seismologists worldwide in the 1950s. The elasticity theory of dislocations was applied to the earthquake mechanism and Takuo Maruyama's sophisticated mathematical theory was suggested by Hirokichi Honda's hypothesis of a pair of couples, i.e., that force system type II at the foci of earthquakes corresponds to earthquake faults. Furthermore, Keiiti Aki's studies in the 1960s on the earthquake mechanism using Love and Rayleigh waves strongly supported the double-couple source mechanism. During this period, not only studies analyzing waveforms of earthquakes but also statistical studies on the characteristics of earthquake occurrence were conducted actively. Some seismologists, such as Chuji Tsuboi, examined time, space, and magnitude distributions of earthquakes and discussed the energy of earthquakes. Experimental studies on the mechanical properties of rocks under high pressures and temperatures began in the second half of the 1950s. Magnitude-frequency relations of elastic shocks accompanying fractures were discussed comparing the statistical nature of earthquakes. Besides, the Earthquake Prediction Research Project was launched at the initiative of seismologists in the 1960s.
The travertine terraces of the Bora coast, at the southeastern part of Miyako Island, Okinawa Prefecture have been designated and notified as a new natural monument by the Ministry of Education, Culture, Sports, Science and Technology and Agency for Cultural Affairs. They are distributed in a small area, ca. 70 m (long) × 30 m (wide), and lie between the low-tide level and 6 m a.s.l. Their diameters are between 10 cm (minimum) and 6 m (maximum), while the relative heights among rimstone pools are between 1 cm and 1 m. The terrestrial laser scanner (TLS) technique is an effective method for drawing precise contour maps and expressing complex small-scale topography. In addition, it is cheaper and less time consuming than producing a map with a total station. To express the characteristics of the travertine terraces, precise contour maps are drawn with 2.5 cm and 20 cm contour intervals using a TLS (VZ-400) and software programs. Information is provided for readers who need to draw a precise contour map successfully with TLS and software programs. The principle and application of the terrestrial laser scanning method are described in the text. Large-scale precise contour maps and photographs of travertine terraces are also presented.