Land use change of Kitakyushu based on landscape ecology and Markov model

Based on four phases of TM images acquired in 1990, 1995, 2000 and 2005, this paper took Kitakyushu in Japan as a case study to analyze spatial change of land use landscape and corresponding effects on environmental issues guided by landscape ecology theory in virtue of combining technology of Remote Sensing with GIS. Firstly, land use types were divided into 6 classes (farmland, mountain, forestland, water body, urban land and unused land) according to national classification standard of land use, comprehensible ability of TM image and purpose of this study. Secondly, following the theory of landscape ecology analysis, 11 typical landscape indices were abstracted to evaluate the environmental effects and spatial feature changes of land use. Research results indicated that land use has grown more and more diversified and unbalanced, human activities have disturbed the landscape more seriously. Finally, transfer matrix of Markov was applied to forecast change process of land use in the future different periods, and then potential land use changes were also simulated from 2010 to 2050. Results showed that conversion tendency for all types of land use in Kitakyushu into urban construction land were enhanced. The study was anticipated to help local authorities better understand and address a complex land use system, and develop improved land use management strategies that could better balance urban expansion and ecological conservation.     

西北太平洋: 21世纪的地理--政治枢纽

20世纪初,英国著名地理学家麦金德在其名著《历史的地理枢纽》一书中,通过对地理大发现以后世界政治地图,尤其是欧洲政治地图变化的分析,提出了“大陆腹地”的概念,并把中、东欧地区称为国际政治的“枢纽”地区。二战以后,美、英等西方国家正是基于麦金德的这一思路,把围堵“枢纽”地区作为其全球战略的重中之重,拉开了长达半个世纪的“冷战”帷幕。冷战结束以后,世界政治地理格局发生了重大变化,西北太平洋地区以其重要的地理位置、蓬勃发展的经济和急剧增长的军备,成为国际地缘政治中新的“枢纽”地区。本文从政治军事地理角度对这一问题进行了初步研究,供关心西北太平洋地区局势的同仁参考。     

Topography of the Seismic Velocity Discontinuities beneath the Chugoku and Shikoku Districts,Southwest Japan

The first P-arrival-time data from 513 local earthquakes were analyzed to study lateral variation of the depth to the Conrad and Moho discontinuities beneath the Chugoku and Shikoku districts, southwest Japan, as well as to determine earthquake hypocenters and P-wave station corrections. The depth to the discontinuity was estimated by minimizing the travel-time residuals of more than 8700 first P arrivals observed at 55 seismic stations. The Conrad and Moho discontinuities are located within depth ranges of 15–25 km and 30–40 km, respectively. The Moho is deeper under the mountain area than under the Seto Inland Sea area, and especially deep under the Pacific Coast of the Shikoku district and the mountain area in the Chugoku district. The depth variation of the Moho is quite similar to the Bouguer gravity anomaly distribution and the lateral variations of the P-wave velocity. The deep Moho under the southern Shikoku is located at the portion in which the continental Moho under the island arc meets the oceanic Moho that is the boundary interface between the oceanic crust and the Philippine Sea (PHS) plate dipping toward the back arc. Although there are high mountains in the northern and middle Shikoku, the Moho is not so deep because subduction of the PHS plate prevents the Moho from getting deep, while the Moho is deep due to isostatic balance under the mountain area in the Chugoku district. In addition, we indicated the possibility that the upper boundary of the oceanic crust just above the high-velocity PHS plate is in contact with the deep Moho under the western Chugoku. The contact of the Moho with the oceanic crust can explain the markedly negative gravity anomaly observed in the western Chugoku and the later phase that appears just after the first P arrival from local earthquakes.     

Seismic Hazard Evaluation Using Markov Chains: Application to the Japan Area

Seismogenic regions within some geographic area are interrelated through tectonics and seismic history, although this relation is usually complex, so that seismicity in a given region cannot be predicted in a straightforward manner from the activity in other region(s). We present a new statistical method for seismic hazard evaluation based on modeling the transition probabilities of seismicity patterns in the regions of a geographic area during a time interval, as a Markov chain. Application of the method to the Japan area renders good results, considering the occurrence of a high probability transition as a successful forecast. For magnitudes M5.5 and time intervals t=0.10 year, the method yields a 78% aftcast (forecast of data already used to evaluate the hazard) success rate for the entire catalog, and an indicative 80% forecast success rate for the last 10 transitions in the catalog. A byproduct of the method, regional occurrence probabilities determined from the transition probabilities, also provides good results; aftcasts of regional activity have a 98% success rate, and those of activity in the highest probability region about 80.5% success rate. All results are superior to those from the null hypotheses (a memory-less Poissonian, fixed-rate, or uniform system) and have vanishingly small probabilities of resulting from purely random guessing.     

Interrelationships Between Topography,Quaternary Vertical Displacement,Active Faults and Short-term Horizontal Crustal Strain in Honshu,Japan

Regional and local characteristics of active fault patterns and elevation variation throughout Honshu, Japan are characterized in terms of their fractal dimensions; this allows variation in these complex variables to be compared directly to the scalar properties of net Quaternary vertical displacement, elevation and 10- and 110-year horizontal strains. The comparisons reveal that, throughout Honshu as a whole, there is significant correlation (r=0.75) between Quaternary vertical displacement, elevation, and its fractal properties. There is poor correlation, however, of elevation and its fractal properties to horizontal crustal strain, and also between Quaternary vertical displacement and horizontal crustal strain. A slight negative correlation is observed between the fractal properties of the active fault system and horizontal crustal strain measured over 10- and 110-year time periods (–0.43 and –0.26, respectively). The correlation between the 10-year (1985–1994) and 110-year (1883–1994) area strains, 0.48, reveals the occurrence of considerable change in the distribution of regional strain over these short time frames. Local computations of the correlation between data sets made for overlapping 160 km length windows of data spaced every 20 km along analysis lines reveal internal fluctuations in the correlation between variables. The local correlation between Quaternary vertical displacement and elevation is highest through central Japan and the Kinki Triangle. There is weak negative correlation between area strain and fractal dimensions of the active fault network. The local correlation between the fractal dimensions of active faults and horizontal area strain over the recent 10-year time period averages about –0.6 through central Japan in an area that extends across the Kinki Triangle through the northern part of central Honshu and northeast across the Itoigawa Shizuoka Tectonic Line. In general, regions of greatest complexity in the active fault network are associated with persistent negative area or compressional strain. Sparsely faulted areas in general coincide with areas of positive or roughly zero area strain. The presence of negative correlation through central Japan and the Kinki Triangle area in the recent 10-year period results from a decrease of area strain within an increasingly complex active fault system that reaches maximum negative values concentrated in the Kinki Triangle during the 1985–1994 time period.     

Physical criterion to evaluate seismic activity associated with the seismic cycle of great interplate earthquakes

A new criterion is introduced to judge if the vicinity of the source region of a great interplate earthquake is in an active period. It is based on the stress change caused by the great earthquake. A region is regarded as being in an active period of seismicity if the occurrence rate of earthquakes on faults in the stress shadow of the great earthquake is significantly higher than in the early stage of the seismic cycle, and if the stressing rate of these faults is sufficiently low. This criterion was applied to the seismicity in the central part of southwest Japan before and after the 1944 Tonankai and 1946 Nankai earthquakes. The results show that before the 1944 Tonankai earthquake, the region was in an active period from at least 1927.The region was in a quiet period for almost50 years after the 1946 Nankai earthquake.Data after 1995 show that the region is once more in an active period of seismicity preceding the next great interplate earthquakes along the Nankai trough,although the total number of earthquakes has not yet significantly increased. Our results indicate that earthquake probability in the central part of southwest Japan will become high in the coming decades until the next great interplate earthquakes along the Nankai trough.     

Anisotropy of gas permeability associated with cleat pattern in a coal seam of the Kushiro coalfield in Japan

An underground investigation has been performed in a subbituminous coal seam exhibiting a particular cleat pattern in the Kushiro coalfield, Japan. The coal cleat pattern shows some analogy to isolated straight joints, and is believed to have been formed during the late Tertiary period by a compressive tectonic stress, roughly in the east–west direction. Three cylindrical coal specimens representing the three orthogonal axes of the coal seam with respect to the bedding plane and its associated cleat were cored from a large block of coal. Gas permeabilities of the three coal specimens were measured under the same hydrostatic pressure conditions. Results clearly revealed anisotropy in permeability of the coal seam under relatively low confining pressures of less than about 12 MPa. The specimen cored parallel to both the bedding plane and cleat strike showed the highest permeability, even though the cleats were partly filled with calcite and clay minerals. The permeability in this direction was 2.5 times higher than perpendicular to the bedding plane, and 3 times higher than in the direction parallel to the bedding plane but perpendicular to the cleat strike. This suggests that the cleats play a greater role than bedding planes in controlling fluid flow in the coal seam. The permeability in the three orientations, however, converged to the same value at confining pressures above about 16 MPa. This may suggest that both cleats and bedding planes in a coal seam can close due to earth pressure if the coal seam is located below a certain depth. It further indicates that the traditional view that gas permeability is always greater parallel to the coal bedding than perpendicular to it should be reconsidered.     

Estimation of the sequence and size of the Tozawagawa landslide,Niigata, Japan,using aerial photographs

On 5 January 2000, a landslide occurred along the right flank of the upper tributary of the Tozawagawa River in Niigata Prefecture, Japan. The landslide blocked the river and formed a temporary lake approximately 670 m long and 11 m deep. In this report, we estimated a time series of aerial photographs from 1947, 1976, 2000, and 2001 to describe the sequences of the landslide. There are some indications that the landslide is a reactivation of an old failure that occurred before 1947. In addition, we have attempted to calculate the scale and volume by aerial photogrammetry.     

Using an airborne laser scanner for the identification of shallow landslides and susceptibility assessment in an area of ignimbrite overlain by permeable pyroclastics

An airborne laser scanner can identify shallow landslides even when they are only several meters in diameter and are hidden by vegetation, if the vegetation is coniferous or deciduous trees in a season with fewer leaves. We used an airborne laser scanner to survey an area of the 1998 Fukushima disaster, during which more than 1,000 shallow landslides occurred on slopes of vapor-phase crystallized ignimbrite overlain by permeable pyroclastics. We identified landslides that have occurred at the 1998 event and also previous landslides that were hidden by vegetation. The landslide density of slopes steeper than 20° was 117 landslides/km² before the 1998 disaster. This event increased the density by 233 landslides/km² indicating that this area is highly susceptible to shallow landsliding.