日本自然灾害现状与新态势   总被引：3，自引：0，他引：3  

毛德华  何梓霖  秋山道雄 《世界地理研究》2006,15(2):41-47

日本是一个多灾且严重的国家,依据最新资料,分析了日本自然灾害的现状特征;自然灾害影响社会经济发展,而社会经济变化可能成为新的致灾因素并形成新的灾害形式。本文特别对城市化、过疏化、高龄化和网络化与灾害进行了论述;最后论述了“自助”“共助”和“公助”三位一体的防灾基本对策的内容。这些对正处于高速经济发展和城市化的我国来说,具有重要的借鉴作用。  相似文献   

Ecologic and taxonomic diversification in the Mesozoic brackish-water bivalve faunas in Japan, with emphasis on infaunalization of heterodonts     

Yasuo Kondo  Takeshi Kozai  Naoki Kikuchi  Kazuhiro Sugawara 《Gondwana Research》2006,10(3-4):316-327

Mesozoic brackish-water bivalve faunas in Japan diversified in three steps: at the beginning of the Early Jurassic, Early and Late Cretaceous. The Hettangian Niranohama Fauna in northeastern Honshu represents the establishment of a heterodont-dominated brackish-water fauna that persisted until the early Late Cretaceous. No similar composition is known from the Triassic. The infauna consists mostly of non-siphonate and some short-siphonate heterodonts, while the epifauna is represented by diverse pteriomorphian families. In the Early Cretaceous Tetori Group in central Honshu, the long-siphonate heterodonts Tetoria (Corbiculidae) and the semi-infaunal soft-bottom oyster Crassostrea appeared. The evolutionary diversification of the latter, known as the most important element of modern brackish-water faunas, may thus originate at that time. In the early Late Cretaceous (Cenomanian) of the Goshoura and Mifune Groups in west Kyushu, several euryhaline deep-burrowing heterodont families, such as Veneridae and Tellinidae, further diversified in the brackish and marine environments. The Late Cretaceous is characterized by massive shell biolithic beds in which large Crassostrea species are common, a feature common for Cenozoic brackish-water faunas. The long-term changes in the composition of the brackish-water faunas in Japan represents thus an evolutionary record, irrespective of the severe physiological and environmental conditions imposed on the highly conservative nature of the fauna.  相似文献   

Preparation of a New Geological Survey of Japan Geochemical Reference Material: Coral JCp-1   总被引：2，自引：0，他引：2  

Takashi Okai  Atsushi Suzuki  Hodaka Kawahata  Shigeru Terashima  Noboru Imai 《Geostandards and Geoanalytical Research》2002,26(1):95-99

A new geochemical reference material, coral Porites sp. JCp-1 has been prepared by the Geological Survey of Japan (GSJ). Provisional values for twenty one major, minor and trace elements are presented. The homogeneity tests showed that all elements studied are considered to be homogeneously distributed.  相似文献   

Most likely locations of large earthquakes in the Kanto and Tokai areas, Japan, based on the local recurrence times     

Max Wyss  Shozo Matsumura 《Physics of the Earth and Planetary Interiors》2002,131(2):173-184

We examined the hypothesis that minima in local recurrence time, T_L, or equivalently maxima in local probability, P_L, may map asperities in the Kanto and Tokai areas of Japan, where the earthquake catalog of the National Research Institute for Earth Science and Disaster Prevention (NIED) is complete at the M=1.5 (M1.5) level. We mapped T_L (P_L) based on the a- and b-values of the nearest earthquakes within 20 km of every node of a grid spaced 0.01° for M7 target events. Only earthquakes within the top 33 km were used. The b-values increase strongly with depth, in several areas. Therefore, some of the T_L (P_L) anomalies are not revealed if data from the entire crustal seismogenic zone are mixed. Thus, we mapped T_L (P_L) separately for the top 15 km and the rest of the depth range, as well as for the entire seismogenic crust. The resulting T_L- and P_L-maps show that approximately 12% of the total area shows anomalously short recurrence times. Out of six shallow target events with M≥6.5 and which occurred since 1890, five are located within the anomalous areas with T_L <450 years. We interpret this to mean that areas with anomalously short T_L map asperities, which are more likely than other areas to generate future target events. The probability that this result is due to chance is vanishingly small. The great Kanto rupture of 1923 appears to have initiated in the most significant asperity we mapped in the study area. One anomaly is located in the northeastern part of the area of the proposed future rupture of the Tokai earthquake, and another one at its southwestern corner. The absolute values of T_L calculated are uncertain because they depend on the size of the volume used for the calculation.  相似文献   

Petrological feature of spinel lherzolite xenolith from Oki-Dogo Island: An implication for variety of the upper mantle peridotite beneath southwestern Japan     

Natsue Abe  Masao Takami  Shoji Arai 《Island Arc》2003,12(2):219-232

Abstract   Spinel lherzolite is a minor component of the deep-seated xenolith suite in the Oki-Dogo alkaline basalts, whereas other types of ultramafic (e.g. pyroxenite and dunite) and mafic (e.g. granulite and gabbro) xenoliths are abundant. All spinel lherzolite xenoliths have spinel with a low Cr number (Cr#; < 0.26). They are anhydrous and are free of modal metasomatism. Their mineral assemblages and microtextures, combined with the high NiO content in olivine, suggest that they are of residual origin. But the Mg numbers of silicate minerals are lower (e.g. down to Fo₈₆) in some spinel lherzolites than in typical upper mantle residual peridotites. The clinopyroxene in the spinel lherzolite shows U-shaped chondrite-normalized rare-earth element (REE) patterns. The abundance of Fe-rich ultramafic and mafic cumulate xenoliths in Oki-Dogo alkali basalts suggests that the later formation of those Fe-rich cumulates from alkaline magma was the cause of Fe- and light REE (LREE)-enrichment in residual peridotite. The similar REE patterns are observed in spinel peridotite xenoliths from Kurose and also in those from the South-west Japan arc, which are non-metasomatized in terms of major-element chemistry (e.g. Fo > 89), and are rarely associated with Fe-rich cumulus mafic and ultramafic xenoliths. This indicates that the LREE-enrichment in mantle rocks has been more prominent and prevalent than Fe and other major-element enrichment during the metasomatism.  相似文献   

Early Miocene rotational process in the eastern part of south-west Japan inferred from paleomagnetic studies     

Yasuto Itoh  Kazuya Kitada 《Island Arc》2003,12(4):348-356

Abstract This paper provides untilted paleomagnetic data obtained from the early Miocene strata around the Kanazawa‐Iozen area, in the eastern part of south‐west Japan. A thick pile of volcaniclastics and marine transgressive sediments underlie the area; they were deposited in the early stage of the Japan Sea opening event. Progressive thermal demagnetization tests isolated stable primary magnetic vectors from eight sites in the upper part of the Iozen Formation. Overall, the tilt‐corrected mean direction of this unit is D = 36.4°, I = 51.6° and α₉₅ = 12.1. Together with a published paleomagnetic and chronological database, the present results suggest that clockwise rotation of south‐west Japan, linked to the back‐arc opening, commenced in the early Miocene and accelerated at the same time as rapid subsidence along the Japan Sea coast. Post‐opening, differential rotation within the eastern part of south‐west Japan is assumed, based on selected paleomagnetic data from the latest Early Miocene.  相似文献   

Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt     

Kazuhiro Tsukada 《Gondwana Research》2003,6(4):687-698

The Hida marginal belt (HMB), which consists of various kinds of fault-bound blocks, is located between the continental massif of the Hida belt and the Mesozoic accretionary complex of the Mino belt in Central Japan. Detailed field investigation reveals that the HMB had grown through the two different movements, i.e., Jurassic dextral and Cretaceous sinistral movements. The Jurassic dextral ductile shear zones run in the southern marginal part of the Hida belt and the northern part of the HMB, whereas the Cretaceous sinistral cataclastic shear zones occur in the southern part of the HMB and the northern marginal part of the Mino belt. Geologic map and field evidence seem to suggest that the Jurassic dextral movement form the fault-bound blocks of the HMB to form the basic structure of the Hida marginal belt, i.e., formation of the ‘proto-HMB.’ Following the dextral movement, the sinistral one restructured the ‘proto-HMB’ to complete the present feature of the Hida marginal belt. The Cretaceous sinistral movement might result in the sinistral collision between the proto-HMB and the Mino belt.  相似文献   

GPS-measured land subsidence in Ojiya City, Niigata Prefecture, Japan   总被引：1，自引：0，他引：1  

Hiroshi P. Sato  Kaoru Abe  Osamu Ootaki 《Engineering Geology》2003,67(3-4):379-390

Land subsidence caused by compression of clay layers in Ojiya City, Japan was measured by global positioning system (GPS) between 1 April 1996 and 31 December 1998.

Three baselines were selected in and around the city, and height difference on a WGS-84 ellipsoid was measured by GPS on each baseline. The ground at the GPS station in the city subsides and rebounds 7 cm every winter and spring, respectively. Measurement accuracy was 9.5 mm standard deviation. Ground water level was observed at a well near the GPS station. Regression analysis between total strain, calculated as ratio of the height difference displacement to the total thickness of the clay layers, and the layers' effective stress change with ground water level change gave good correlation. The slope of regression line 7.0×10⁻¹¹ m²/N was obtained as an average apparent coefficient of volume compressibility of the layers.  相似文献   

A new gravity map, a new marine geoid around Japan and the detection of the Kuroshio current   总被引：3，自引：0，他引：3  

A. Adjaout  M. Sarrailh 《Journal of Geodesy》1997,71(12):725-735

About half a million marine gravity measurements over a 30^∘×30^∘ area centered on Japan have been processed and adjusted to produce a new free-air gravity map from a 5′×5′ grid. This map seems to have a better resolution than those previously published as measured by its correlation with bathymetry. The grid was used together with a high-degree and -order spherical harmonics geopotential model to compute a detailed geoid with two methods: Stokes integral and collocation. Comparisons with other available geoidal surfaces derived either from gravity or from satellite altimetry were made especially to test the ability of this new geoid at showing the sea surface topography as mapped by the Topex/Poseidon satellite. Over 2 months (6 cycles) the dynamic topography at ascending passes in the region (23^∘47^∘N and 123^∘147^∘E) was mapped to study the variability of the Kuroshio current. Received: 15 July 1994 / Accepted: 17 February 1997  相似文献   

四川呷村银多金属矿床地质特征及其与日本黑矿的类比   总被引：5，自引：0，他引：5  

傅德明  徐明基 《四川地质学报》1996,(1)

呷村地处特提斯－喜马拉雅构造域东缘。呷村银多金属矿床产于晚三叠世义敦古岛弧带的昌台火山－沉积盆地中，矿床规模经勘查证实为超大型。呷村矿床与日本黑矿类比，在构造背景、地质特征、剖面结构及蚀变和矿化分带、矿石类型、成矿机理等方面具有极大的相似性，说明海底喷气－沉积型块状硫化物矿床，在类似的地质构造环境中均具有极大的远景。  相似文献