Expulsion of geopressured hydrothermal system along active faults and its relation to the occurrence of earthquakes in the Shinanogawa seismic belt,Japan   总被引：2，自引：0，他引：2  

Yasue Oki  Osamu Sato 《中国科学D辑(英文版)》2005,48(2):273-281

The 1995 Northern Niigata Earthquake (M 6.0) occurred at a shallow depth in the Niigata seismic gap. The anomaly areas in temperature, electrical conductivity and Cl- concentration of groundwater trend northeast as linear distribution in the epicentral area and are approximately coincident with the area of the seismic intensity 6 (JMA scale). The distributions of seismic intensity 6 and groundwater anomalies convincingly imaged the presence of a buried active fault beneath the epicentral area. The occurrence of this earthquake and the anomalies of groundwater were related to the expulsion of geopressured hydrothermal system (GHS). All epicenters of the destructive earthquakes along the Shinanogawa seismic belt are actually located in the buried active fault zones characterized by the areas of temperature and geochemical anomalies of groundwater. These earthquakes might have been triggered by the activity of GHS. The expulsion of GHS along an active fault in combination with the thermal softening of fault  相似文献   

A deep near-infrared survey around the giant radio galaxy PKS 1343–601     

T. Nagayama  P. A. Woudt  C. Nagashima  Y. Nakajima  D. Kato  M. Kurita  T. Nagata  H. Nakaya  M. Tamura  K. Sugitani  K. Wakamatsu  S. Sato 《Monthly notices of the Royal Astronomical Society》2004,354(4):980-990

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SH Waves in a Transversely Isotropic Medium–I     

R. Sato  E. R. Lapwood 《Geophysical Journal International》1967,14(1-4):463-470

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Observational studies of 12 DD Lacertae     

Sato  Naonobu 《Astrophysics and Space Science》1977,48(2):453-470

Astrophysics and Space Science - Analysis of the radial velocity curves of 12 DD Lacertae showns that the primary period is decreasing and the secondary is almost constant, confirming the...  相似文献   

Influence of water saturation on horizontal and vertical motion at a porous soil interface induced by incident SV wave   总被引：1，自引：0，他引：1  

Jun Yang  Tadanobu Sato 《Soil Dynamics and Earthquake Engineering》2000,19(5)

Recent field observations have indicated that water saturation of soils may strongly affect the vertical ground motion. A study is therefore carried out to investigate the effect of saturation on horizontal and vertical motion at an interface of porous soils with potential contributions directed to site evaluation based on field observations of both the horizontal and vertical motion. The problem described in this paper corresponds to an SV wave incident at the interface between the overlying soil and the underlying rock formation. The soils are modeled as partially water-saturated porous material with a small amount of air inclusions, while the rock are approximately regarded as ordinary one-phase solid. Theoretical formulation is developed for the computation of amplitudes of horizontal and vertical interface motion, which are expressed as functions of the degree of saturation, the angle of incidence as well as the frequency. Numerical results are given for a typical sand to illustrate the influence of saturation on the interface motion in two directions and their ratios. The present study demonstrates that the effect of water saturation may be substantial on both the horizontal and vertical motion as well as on their ratios, implying the importance of such effects in the interpretation of field observations.  相似文献   

Assessment of the vertical distribution on seismic ground motion   总被引：1，自引：0，他引：1  

K. Sato  K. Toki  Y. Sawada   《Soil Dynamics and Earthquake Engineering》2000,19(6)

It is very important for the facilities such as nuclear power plants to infer seismic force loading on the earthquake stability assessment of the building foundation and the surrounding slope. The purpose of this paper was to propose a method to evaluate underground seismic coefficients, taking into account dynamic response along the depth in horizontally multi-layered ground. The dynamic property of the seismic coefficient was analyzed on the basis of earthquake records observed at hard and soft rock sites mostly found in Tertiary deposits and sedimentary ground sites of the Pleistocene and Holocene epoch. The evaluation methods of a vertical distribution on underground seismic coefficients were proposed for a few calculation methods on the classified layered ground. Extended evaluation for underground seismic coefficients was confirmed with respect to some multi-layered ground during strong motion.  相似文献   

Rb–Sr and Sm–Nd isotopic studies of mafic igneous rocks from the Ryoke plutono-metamorphic belt in the Setouchi area, Southwest Japan: implications for the genesis and thermal history     

Osamu Okano  Takeharu Sato †  Hiroo Kagami ‡ 《Island Arc》2000,9(1):21-36

Abstract Rb–Sr and Sm–Nd isochron ages were determined for whole rocks and mineral separates of hornblende‐gabbros and related metadiabases and quartz‐diorite from Shodoshima, Awashima and Kajishima islands in the Ryoke plutono‐metamorphic belt of the Setouchi area, Southwest Japan. The Rb–Sr and Sm–Nd whole‐rock‐mineral isochron ages for six samples range from 75 to 110 Ma and 200–220 Ma, respectively. The former ages are comparable with the Rb–Sr whole‐rock isochron ages reported from neighboring Ryoke granitic rocks and are thus due to thermal metamorphism caused by the granitic intrusions. On the contrary, the older ages suggest the time of formation of the gabbroic and related rocks. The initial ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios of the gabbroic rocks (0.7070–0.7078 and 0.51217–0.51231 at 210 Ma, respectively) are comparable with those of neighboring late Cretaceous granites and lower crustal granulite xenoliths from Cenozoic andesites in this region. Because the gabbroic rocks are considered to be fragments of the lower crustal materials interlayered in the granulitic lower crust, their isotopic signature has been inherited from an enriched mantle source or, less likely, acquired through interaction with the lower crustal materials. The Sr and Nd isotopic and petrologic evidence leads to a plausible conclusion that the gabbroic rocks have formed as cumulates from hydrous mafic magmas of light rare earth element‐rich (Sm/Nd < 0.233) and enriched isotopic (?_Sr > 0 and ?_Nd < 0) signature, which possibly generated around 220–200 Ma by partial melting of an upper mantle. We further conclude that they are fragments of refractory material from the lower crust caught up as xenoblocks by granitic magmas, the latter having been generated by partial melting of granulitic lower crustal material around 100 Ma.  相似文献   

Two-dimensional inversion of refraction traveltimes by progressive model development     

Toshinori Sato  & Brian L. N. Kennett 《Geophysical Journal International》2000,140(3):543-558

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Age constraints on the Palaeoproterozoic Lomagundi–Jatuli Event in Zimbabwe: Zircon geochronology of the Magondi Supergroup     

Hikaru Sawada  Ernest Tafumanei Mugandani  Tomohiko Sato  Yusuke Sawaki  Shuhei Sakata  Yukio Isozaki  Shigenori Maruyama 《地学学报》2019,31(5):438-444

The ca. 2.2–2.1 Ga Magondi Supergroup on the Zimbabwe Craton in Southern Africa is mainly composed of sedimentary rocks deposited in a rift basin/passive continental margin, which record a unique episode in carbon isotope perturbation called the Lomagundi–Jatuli Event (LJE). This study reports new U–Pb ages of detrital zircons from the Deweras and Lomagundi groups of the Magondi Supergroup, and of igneous zircons from underlying granitoids, to constrain the timing of the LJE and to identify the provenance of the Magondi Supergroup. Most analysed detrital zircon grains range in ages between ca. 2.9 and 2.6 Ga. Three ca. 2.3–2.2 Ga detrital zircons from sandstone of the Deweras Group, with the youngest ²⁰⁷Pb‐²⁰⁶Pb age of 2,216 ± 22 Ma, indicate the onset of LJE in the Zimbabwe Craton was almost simultaneous to that in Fennoscandia and the Superior Craton, supporting the global synchronicity of the LJE.  相似文献   

Trends in the near-zero range of the minimum air-temperature distribution     

Noriyuki Sato  Scott M. Robeson 《自然地理学》2014,35(5):429-442

This study estimated the trends in the number of days that fall within the near-zero (0?°C) range of the temperature continuum. This narrow range has importance for potential transportation hazards and freeze-thaw cycles. While the tails of the air-temperature distribution and their trends often are closely examined under the climate change context, the frequency and trend of other portions of the air-temperature distribution can be equally important, as many societal impacts are caused by events in the non-tail region, such as near-zero °C temperatures (NZT). Examining the trend of the number of NZT days over the conterminous USA for the period of 1948–1949 through 2010–2011, we found three distinct spatial clusters. The most distinctive spatial clusters are found along the West Coast (positive temperature trends leading to a decrease in NZT days), the High Plains and Northern Rockies (positive temperature trends leading to an increase in NZT days), and the southeastern USA (negative temperature trends leading to an increase in NZT days). While trends in the number of NZT days are linked to changes in mean minimum air temperature, increasing minimum temperature leads to a positive trend at NZT days only at some locations.  相似文献