Gravity and magnetotelluric investigations to elicit the origin of Hammam Faraun hot spring,Sinai Peninsula,Egypt   总被引：1，自引：0，他引：1  

Mohamed Abdelzaher  Jun Nishijima  Gad El-Qady  Essam Aboud  Osama Masoud  Mamdoh Soliman  Sachio Ehara 《Acta Geophysica》2011,59(3):633-656

There is a clear correlation between the principal areas of current geothermal development and the seismically active boundaries of the moving segments of lithosphere defined by the plate tectonic models of the Earth. The tectonic position of Egypt in the northeastern corner of African continent suggests that the most important areas for geothermal exploration are in the region where a cluster of hot springs with varied temperatures was located around the Gulf of Suez. Gravity and magnetotelluric surveys were made in the area of Hammam Faraun hot spring, which represents the most promising area for geothermal development in Egypt. These surveys were carried out for the purpose of eliciting the origin of Hammam Faraun hot spring. The results of the analyses and interpretations of these data show that the heat source of the hot spring is due to uplift of hot basement rock. This uplift may cause deep circulation and heating of the undergroundwater.  相似文献   

Research on the stabilization treatment of clay slope topsoil by organic polymer soil stabilizer     

Jin Liu  Bin Shi  Hongtao Jiang  He Huang  Gonghui Wang  Toshitaka Kamai 《Engineering Geology》2011,117(1-2):114-120

The topsoil of clayey slope is easy to erosion because it is weak in its strength, water stability and erosion resistance. A new organic polymer soil stabilizer, which was developed for the stabilization treatment of clay slope topsoil and was named as STW, was introduced in this study. In order to understand the effect of STW on the stabilization of clayey soil, laboratory tests on the unconfined compressive strength, shear strength, water stability and erosion resistance of untreated and treated soil specimens are performed, The results indicated that STW soil stabilizer can significantly increased the unconfined compression strength, shear strength, water stability and erosion resistance of clayey soil. The unconfined compression strength increased with the increasing of curing time and the variation mainly occurs in the first 24-hour. With the addition amounts of STW increasing, the strength, water stability and erosion resistance increased at the curing time being 48 h, but in the case of friction angle, no major change was observed. Based on the scanning electron microscopy (SEM) analysis of the stabilized soil, the stabilization mechanisms of STW soil stabilizer in the clayey soil were discussed. Finally, a field test of the stabilization treatment of clay slope topsoil with STW was carried out, and the results indicated that the STW soil stabilizer on the stabilization treatment of clay slope topsoil is effective for improving the erosion resistance of slope topsoil, reducing the soil loss and protecting the vegetation growth. Therefore, this technique is worth popularizing for the topsoil protection of clay slope.  相似文献   

Secular variations of carbon and helium isotopes at Izu-Oshima Volcano, Japan   总被引：1，自引：0，他引：1  

Yuji Sano  Toshitaka Gamo  Kenji Notsu  Hiroshi Wakita 《Journal of Volcanology and Geothermal Research》1995,64(1-2)

Secular variations in ¹³C/¹²C ratios and chemical compositions of gas samples from October 1986 to July 1992 are reported from a 92–95 °C steam well located about 3 km north of Mt. Mihara, an active volcano on Izu-Oshima Island, Japan. The δ¹³C value steeply increased from −2.97‰ (relative to PDB carbonate) in December 1986 to −1.15‰ in March 1988 and then gradually decreased to −1.75‰ in July 1992. Over the same period, the CO₂ content changed similarly with time, even though the experimental error is relatively large. These variations are consistent with helium isotope changes. Initially rapid and then slow enhancements of ³He/⁴He ratio, δ¹³C value and CO₂ content are invoked by violent eruptions of Izu-Oshima volcano from 15 November to 18 December 1986. After the eruptive activity, depletion of magmatic gas emission and subsequent mixing with crustal fluids in the hydrothermal system may produce the gradual decreases of ³He/⁴He ratio, δ¹³C value and CO₂ content. Taking into account the rates of these decreases, we suggest that helium and carbon isotope ratios will return to the situation of before the magmatic eruption within 15 years.  相似文献   

High precision slip distribution of the 1944 Tonankai earthquake inferred from tsunami waveforms: Possible slip on a splay fault     

Toshitaka Baba  Phil R. Cummins  Takane Hori  Yoshiyuki Kaneda 《Tectonophysics》2006,426(1-2):119

Inversion of tsunami waveforms is a well-established technique for estimating the slip distributions of subduction zone earthquakes, with some of the most detailed results having been obtained for earthquakes in the Nankai Trough, SW Japan. The present study, although it uses a method and tsunami waveform data set almost identical to previous study, aims to improve on previous work by using a more precise specification of initial conditions for the calculation of tsunami Green's functions. Specifically, we incorporated four improvements in the present study: (1) we used a realistic plate model based only on seismic survey results, and assumed it to be the fault plane of the 1944 Tonankai earthquake; (2) the smallest subfaults consistent with the long wavelength approximation were used in the tsunami inversion analysis; (3) we included the effect of horizontal displacement of the ocean bottom on tsunami generation; and (4) we performed a checkerboard resolution test. As obtained in previous studies, a zone of high slip (> 2.0 m) was resolved off the Shima Peninsula. However, the more precise calculation of tsunami Green's functions has revealed additional detail that was not evident in previous studies, which we demonstrate is resolvable and correlates with the position of known faults in the accretionary prism. While there was little or no slip near the trench axis in the eastern part of the rupture zone, there was up to 1.5 m of slip resolved within 30 km of the trough axis in the western part, along the coast of the Kii Peninsula. This troughward slip zone coincides with the position of a large splay fault mapped in multichannel reflection surveys. Furthermore, it is also clear that the upper edge of the Enshu fault off Shima and Atsumi peninsulas is consistent with the up-dip limit of slip in the eastern part of our model. We tested the possibility that slip occurred on the former splay fault instead of on the plate interface during the 1944 Tonankai earthquake, and find that slip on this splay fault is also consistent with the data, although we cannot distinguish whether slip was dominant on the splay fault or on the plate interface. We further suggest that the position of the Enshu fault may be determined by the subduction of topographic highs, and that such faults may have an important influence on the up-dip rupture limit of the 1944 Tonankai and, potentially, other subduction zone earthquakes.  相似文献   

Origins of hydrocarbons in the Sagara oil field, central Japan     

Tomohiro  Toki  Toshitaka  Gamo  Urumu  Tsunogai 《Island Arc》2006,15(3):285-291

Abstract   We collected free-gas and in situ fluid samples up to a depth of 200.6 m from the Sagara oil field, central Japan (34°44'N, 138°15'E), during the Sagara Drilling Program (SDP) and measured the concentrations and stable carbon isotopic compositions of CH₄ and C₂H₆ in the samples. A combination of the CH₄/C₂H₆ ratios with the carbon isotope ratios of methane indicates that the hydrocarbon gases are predominantly of thermogenic origin at all depths. The isotope signature of hydrocarbon gases of δ¹³      < δ¹³     suggests that these gases in the Sagara oil field are not generated by polymerization, but by the decomposition of organic materials.  相似文献   

Wind fluctuations near a cold vortex-tropopause funnel system observed by the MU radar     

Shoichiro Fukao  Manabu D. Yamanaka  Hiromasa Matsumoto  Toru Sato  Toshitaka Tsuda  Susumu Kato 《Pure and Applied Geophysics》1989,130(2-3):463-479

Vertical and temporal variations of three-dimensional wind velocity associated with an upper-tropospheric cold vortex-tropopause funnel system were observed by an MST radar in Japan (the MU radar). Marked changes of vertical velocity and horizontal wind direction were found between the inside and outside of the cold vortex. The vertical velocity activity outside the vortex was asymmetric; it was most active in a sector before the vortex. Unsaturated internal gravity waves in their generation stage contribute predominantly to the vertical velocity activity, suggesting that tropospheric occluded cyclones may be a possible source of middle-atmospheric gravity waves through the geostrophic adjustment process.  相似文献   

Internal gravity wave selection in the upper troposphere and lower stratosphere observed by the MU radar: Preliminary results     

Manabu D. Yamanaka  Shoichiro Fukao  Hiromasa Matsumoto  Toru Sato  Toshitaka Tsuda  Susumu Kato 《Pure and Applied Geophysics》1989,130(2-3):481-495

Marked wavelike variations of the lower stratospheric wind observed on 7–10 May, 1985 by an MST radar in Japan (by the MU radar) are analyzed assuming that they are induced by monochromatic internal inertio-gravity waves. These variations are mainly composed of two modes (periods: 22 and 24 hours), both of which have zonal phase velocities (C _X ) slower than the mean westerly wind (). A statistical analysis of the zonal phase velocity shows thatC _X above andC _X below the tropopause jet stream, which is considered to be a vivid proof of wave selection due to the tropospheric mean flow and upward wave emission from the tropopause jet. A comparison between the MU radar results and routine meteorological observations leads to the conclusion that the marked waves appear when the jet stream takes a maximum wind speed.  相似文献   

Excess bottom²²²Rn profiles and their implications in the northwestern Pacific Ocean     

Toshitaka Gamo  Yoshio Horibe 《Earth and Planetary Science Letters》1984,71(2):215-228

Vertical profiles of excess bottom²²²Rn and potential temperature were measured at 23 stations in the northwestern Pacific Ocean. The Rn profiles were classified into the following three types: quasi-exponential (type E), benthic boundary layer (type B), and horizontally disturbed (type H). The ratio among types E, B and H was approximately 2 : 3 : 1.An apparent vertical eddy diffusivity (K) was calculated by applying a one-dimensional diffusion model to the Rn profiles of types E and B. Type E had K values ranging from 15 to 180 cm² s^?1 (average: 70 cm² s^?1). As to type B, K values for the benthic boundary layer (4.5–260 cm² s^?1, average: 120 cm² s^?1) were always more than an order of magnitude larger than those for the upper layer (0.2–35 cm² s^?1, average: 7 cm² s^?1), indicating more active vertical mixing in the benthic boundary layer than in the upper layer.Rn profiles were measured in regions where the bottom topography is known. It was verified that the occurrence of type H related closely with local bottom topographic features accompanied by lateral transient supply of Rn-rich or Rn-poor water.A couple of Rn profiles at the same location, measured at time intervals of several years, were compared with each other for three locations. The general characteristics of Rn profiles were shown to remain unaltered with time, while the fine structure of Rn profiles may have short-term variations caused by local bottom topography and fluctuations of bottom current as indicated in type H.  相似文献   

Near-field tsunami amplification factors in the Kii Peninsula,Japan for Dense Oceanfloor Network for Earthquakes and Tsunamis (DONET)     

Toshitaka Baba  Narumi Takahashi  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):319-325

We investigated the correlation between coastal and offshore tsunami heights by using data from the Dense Oceanfloor Network for Earthquakes and Tsunamis (DONET) observational array of ocean-bottom pressure gauges in the Nankai trough off the Kii Peninsula, Japan. For near-field earthquakes, hydrostatic pressure changes may not accurately indicate sea surface fluctuations, because ocean-bottom pressure gauges are simultaneously displaced by crustal deformation due to faulting. To avoid this problem, we focused on the average waveform of the absolute value of the hydrostatic pressure changes recorded at all the DONET stations during a tsunami. We conducted a Monte Carlo tsunami simulation that revealed a clear relationship between the average waveforms of DONET and tsunami heights at the coast. This result indicates the possibility of accurate real-time prediction of tsunamis by use of arrays of ocean-bottom pressure gauges.  相似文献   

The optical reflector system for the CANGAROO-II imaging atmospheric Cherenkov telescope     

A. Kawachi  Y. Hayami  J. Jimbo  S. Kamei  T. Kifune  H. Kubo  J. Kushida  S. LeBohec  K. Miyawaki  M. Mori  K. Nishijima  J. R. Patterson  R. Suzuki  T. Tanimori  S. Yanagita  T. Yoshikoshi  A. Yuki 《Astroparticle Physics》2001,14(4):1492-269

A new imaging atmospheric Cherenkov telescope with a light-weight reflector has been constructed. Light, robust, and durable mirror facets of containing carbon fiber reinforced plastic laminates were developed for the telescope. The reflector has a parabolic shape (f/1.1) with a 30 m² surface area, which consists of 60 spherical mirror facets. The image size of each mirror facet is 0°.08 (FWHM) on average. The attitude of each facet can be adjusted by stepping motors. After the first in situ adjustment, a point image of about 0°.14 (FWHM) over 3° field of view was obtained. The effect of gravitational load on the optical system was confirmed to be negligible at the focal plane. The telescope has been in operation with an energy threshold for γ-rays of 300 GeV since May 1999.  相似文献