Stormflow generation involving pipe flow in a zero‐order basin of Peninsular Malaysia

Hydrological responses in a zero‐order basin (ZOB), a portion of whose discharge emerged via preferential flow through soil pipes, were examined over a 2‐year period in Peninsular Malaysia to elucidate primary stormflow generation processes. Silicon (Si) and specific conductance (EC) in various runoff components were also measured to identify their sources. ZOB flow response was dependent on antecedent precipitation amount; runoff increased linearly with precipitation during events >20 mm in relatively wet antecedent moisture conditions. Runoff derived from direct precipitation falling onto saturated areas accounted for <0·2% of total ZOB flow volume during the study period, indicating the predominance of subsurface pathways in ZOB flow. ZOB flow (high EC and low Si) was distinct from perennial baseflow via bedrock seepage (low EC and high Si) 5 m downstream of the ZOB outlet. Pipe flow responded quickly to ZOB flow rate and was characterized by a threshold flow capacity unique to each pipe. Piezometric data and pipe flow records demonstrated that pipes located deeper in the soil initiated first, followed by those at shallower depths; initiation of pipe flow corresponded to shallow groundwater rise above the saprolite‐soil interface. Chemical signatures of pipe flow were similar to each other and to the ZOB flow, suggesting that the sources were well‐mixed soil‐derived shallow groundwater. Based upon the volume of pipe flow during storms, the combined contribution of the pipes monitored accounted for 48% of total ZOB flow during the study period. Our results suggest that shallow groundwater, possibly facilitated by preferential flow accreted above the saprolite–soil interface, provides dominant stormflow, and that soil pipes play an important role in the rapid delivery of solute‐rich water to the stream system. Copyright © 2006 John Wiley & Sons, Ltd.     

Large-Scale Mapping Observations of the C i (3P1-3P0) and CO (J = 3-2) Lines toward the Orion A Molecular Cloud

Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.     

Resistivity exploration for altered zone at otake geothermal area — Japan

Geothermal electric power plant with a capacity of 10 mw has been now constructed by the Kyushu Electric Power Co. Ltd. at Otake, northern part of the Kyushu Island. Resistivity exploration, one of geophysical prospecting applied to this field in order to investigate the subsurface structure accompanied with natural steams, indicated low resistivity layer corresponding to altered zone of andesite due to hydrothermal agents. For the rapid interpretation of resistivity sounding curves, a method of calculating the standard curve for the multiple layered earth is developed in the utilization of an electronic digital computer. Some examples to show the application of this method are given, and tinally the result is described of resistivity measurement at Otake geothermal area.     

Origin of a magnetic lineation on Kyushu Island, Japan

Abstract Several linear magnetic anomalies over continental crust have been identified in and around the Japanese Islands. The anomalies are probably related to island arc tectonic structures, but identifying specific sources has been difficult. Several deep holes were drilled in and around Aso caldera, where a linear anomaly occurs along an active fault. One drillhole located on the linear anomaly encountered a zone of highly magnetized and altered basement rocks at least 100 m thick at a depth of ∼1000 m. The other hole was located away from the anomaly and did not encounter any high-magnetic zones. Rocks from the zone have exceptionally strong remanent magnetization (several tens of A/m) sub-parallel to the present field. AF demagnetization experiments indicated that the magnetization is hard and stable. Magnetic modeling indicates that the linear anomaly is caused mainly by this layer. Microscopic examination of core samples shows that the highly magnetized zone includes secondary magnetic minerals and abundant hydrothermal alterations. Temperatures determined by fluid inclusions and down-hole temperatures show that the temperature of the highly magnetized zone was elevated in the past relative to surrounding rocks. The high temperature could destroy primary magnetic minerals and replace them with secondary magnetic minerals. Thus, the past hydrothermal system may have enhanced thermo-chemical remanent magnetization. The results can produce a model indicating that there was a past hydrothermal system related to the tectonic structure.     

Partial mass isolation in tall buildings

To find an economical approach in the seismic design of tall buildings, it is proposed to isolate a part of the structure by an isolator layer located in the height of building. Application of this technique causes a fundamental change in basic dynamic characteristics of the system. As a result, all major modal shapes of structure exhibit large displacement at the level of the isolator. A viscous damping device integrated into the isolation layer utilizes this relative movement to effectively reduce the earthquake input energy transmitted to the system. This technique is quite versatile and easily adjustable to different applications including seismic retrofit of buildings. Numerical analysis of some basic examples in this study shows desirable performances for a variety of applications. © 1998 John Wiley & Sons, Ltd.     

CCD Photometry of KZ Hya using the 45-CM Telescope in Paraguay

A SX Phe-type pulsating variable KZ Hya (HD94033) was observed with CCD set attached to the 45-cm reflector at Asuncion Astronomical Observatory in Paraguay. In the present work, 12 maximum phases were covered. A new ephemeris has been obtained, and the result suggests a probable change of the pulsation period of KZ Hya.     

Quasi-decadal modulations of North Pacific Intermediate Water area in the cross section along the 137°E meridian: impact of the Aleutian Low activity

Temporal variations of area of the North Pacific Intermediate Water (NPIW), in the repeat hydrographic section along 137°E meridian conducted by the Japan Meteorological Agency, are investigated using the de-trended variables from 1972 to 2008. Variations of NPIW area show a clear quasi-decadal (about 10 years) modulation and it is caused by the vertical displacement of isopycnal surfaces in the lower portion of NPIW around the northern boundary of its distribution (30–32°N): The downward (upward) movement of isopycnal surfaces in the lower portion of NPIW as a result of the first-mode baroclinic ocean response stretches (shrinks) the density layer equivalent of NPIW and causes strengthening (weakening) of westward flows associated with the Kuroshio Counter Current, and then it can induce an increase (decrease) of volume transport of NPIW from the east. Consequently, the NPIW northern boundary shifts northward (southward) and an increase (decrease) of the NPIW area is induced. Large-scale atmospheric forcing controlling the vertical displacements of isopycnal surfaces is explored using a wind-driven hindcast ocean model. The vertical displacements stem from the first-mode baroclinic ocean response to the two types of Aleutian Low (AL) activities: in particular, the meridional movement of the AL imparts more potential influence on them than the AL intensity variation does.     

Investigation of cutting methods for small samples of Hayabusa and future sample return missions

We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions.     

Three‐dimensional microstructure of samples recovered from asteroid 25143 Itokawa: Comparison with LL5 and LL6 chondrite particles

In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B.     

Crystallization temperature determination of Itokawa particles by plagioclase thermometry with X‐ray diffraction data obtained by a high‐resolution synchrotron Gandolfi camera

The crystallization temperatures of Itokawa surface particles recovered by the space probe Hayabusa were estimated by a plagioclase geothermometer using sodic plagioclase triclinicity. The Δ131‐index required for the thermometer, which is the difference in X‐ray diffraction peak positions between the 131 and 11 reflections of plagioclase, was obtained by a high‐resolution synchrotron Gandolfi camera developed for the third generation synchrotron radiation beamline, BL15XU at SPring‐8. Crystallization temperatures were successfully determined from the Δ131‐indices for four particles. The observed plagioclase crystallization temperatures were in a range from 655 to 660 °C. The temperatures indicate crystallization temperatures of plagioclases in the process of prograde metamorphism before the peak metamorphic stage.