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101.
Specially designed arrays of strong-motion seismographs near to the earthquake source are required for seismological and engineering studies of the generation and near-field properties of seismic waves. The first such large digital array, called SMART 1 (with radius 2 km and 37 accelerometers), to record substantial ground motion (up to 0·24g horizontal acceleration) became operational in late 1980 in a highly seismic region of Taiwan. During the first 6 months of operation, SMART 1 recorded nine earthquakes with magnitudes ranging from ML 3·8 to 6·9. Three were located directly below the array at focal depths of 59 to 76 km. The remaining six had shallow depths and epicentral distances from 7 to 193 km. Digital records from 27 three-component accelerographs were obtained from a magnitude 6·9 (ML) local earthquake on 29 January 1981. Representative measurements are described of seismic wave coherency and power spectrum as a function of wave number, frequency, azimuth of propagation and wave type. Acceleration waveforms varied significantly across the array for each event. On average, peak acceleration of horizontal components was about three times that of the vertical component. Relative spectral changes from earthquake to earthquake were large. 相似文献
102.
Selected by-products which are produced upon chlorination or ozonization of seawater were examined for their effect on eastern oyster (Crassostrea virginica) larvae. The compounds, bromate, bromoform, and chloroform, were studied at 0.05, 0.1, 1.0, and 10.0 mg/l. Repeated bioassays indicated that even at these low levels, all three substances produced some larval mortality. This preliminary study suggests that oxidation by-products formed during chlorination or ozonization of power plant cooling waters may have adverse effects upon the growth of marine invertebrates, such as C. virginica, during their delicate larval stages. 相似文献
103.
Abstract— We have made aluminum‐magnesium isotopic measurements on 4 melilite‐bearing calcium‐aluminum‐rich inclusions (CAIs), 1 plagioclase‐olivine inclusion (POI), and 2 ferromagnesian chondrules from the Ningqiang carbonaceous chondrite. All of the CAIs measured contain clear evidence for radiogenic 26Mg* from the decay of 26Al ( = 1.05 Ma). Although the low Al/Mg ratios of the melilites introduce large uncertainties, the inferred initial 26Al/27Al ratios for the CAIs are generally consistent with the value of 5 times 10?5. There is clear evidence of 26Al* in one POI and two chondrules, but with considerable uncertainties in the value of (26Al/27Al)0. The (26Al/27Al)0 ratios for the POI and the chondrules are 0.3–0.6 times 10?5, roughly an order of magnitude lower than the canonical value. Ningqiang shows very little evidence of metamorphism as a bulk object and the (26Al/27Al)0 ratios in its refractory inclusions and chondrules are consistent with those found in other unmetamorphosed chondrites of several different classes. Our observations and those of other workers support the view that 26Al was widely and approximately homogeneously distributed throughout the condensed matter of the solar system. The difference in (26Al/27Al)0 between CAIs and less refractory materials seems reasonably interpreted in terms of a ~2 million year delay between the formation of CAIs and the onset of formation of less refractory objects. The POI shows clear differences in 25Mg/24Mg between its constituent spinels and olivine, which confirms that they are partially reprocessed material from different sources that were rapidly quenched. 相似文献
104.
Great interest has recently been focused on dating and interpreting alluvial-fan surfaces. As a complement to the radiometric methods often used for surface-exposure dating, this paper illustrates a rapid method for correlating and dating fan surfaces using the cross-sectional shape of gullies incised into fan surfaces. The method applies a linear hillslope-diffusion model to invert for the diffusivity age, κt (m2), using an elevation profile or gradient (slope) profile. Gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment. Scarps adjacent to these gullies provide a measure of age. The method is illustrated on fan surfaces with ages of approximately 10 ka to 1.2 Ma in the arid southwestern United States. Two areas of focus are Death Valley, California, and the Ajo Mountains piedmont, Arizona. Gully-profile morphology is measured in two ways: by photometrically derived gradient (slope) profiles and by ground-surveyed elevation profiles. The κt values determined using ground-surveyed profiles are more consistent than those determined using photo-derived κt values. However, the mean κt values of both methods are comparable. The photometric method provides an efficient way to quantitatively and objectively correlate and relatively-date alluvial-fan surfaces. The κt values for each surface are determined to approximately 30–50% accuracy. 相似文献
105.
In this contribution we introduce the concept of multiresolution analysis (MRA) and give an explanation of the relationship
between MRA and orthonormal wavelet basis. The construction of the orthonormal B-spline wavelet bases is described in detail.
We extend the B-splines to `non-integral order' cases and thus obtain a new family of orthonormal wavelet bases for the space
L
2(R). Some good properties of the new wavelets are demonstrated. The new wavelet family gives satisfactory performances in our
research projects including seismic signal compression and gravity tide data processing.
Received: 19 July 1996 / Accepted: 17 November 1997 相似文献
106.
Shiang-Kueen Hsu 《Hydrogeology Journal》1998,6(3):405-415
In Taiwan, rapid economic growth, rising standards of living, and an altered societal structure have in recent years put
severe demands on water supplies. Because of its stable quantity and quality, groundwater has long been a reliable source
of water for domestic, agricultural, and industrial users, but the establishment of a management program that integrates groundwater
and surface-water use has been hampered by the lack of groundwater data. In 1992, the Department of Water Resources (DWR)
initiated a program entitled "Groundwater Monitoring Network Plan in Taiwan." Under this program, basic groundwater data,
including water-level and water-quality data, are being collected, and a reliable database is being established for the purpose
of managing total water resources. This paper introduces the goals, implementation stages, and scope of that plan. The plan
calls for constructing 517 hydrogeologic survey stations and 990 groundwater monitoring wells within 17 years. Under this
program, water-level fluctuations are continuously monitored, whereas water-quality samples are taken for analysis only at
the initial drilling stage and, subsequently, at the time when a monitoring well is being serviced. In 1996, the DWR and the
Water Resources Planning Commission were merged to form today's Water Resources Bureau.
Received, July 1997 · Revised, February 1998 · Accepted, January 1998 相似文献
107.
108.
We studied the mineralogy, mineral chemistry, and compositions of 48 interior silicate inclusions and a large K-rich surface inclusion from the Colomera IIE iron meteorite. Common minerals in the interior silicate inclusions are Cr diopside and Na plagioclase (albite). They are often enclosed by or coexist with albitic glasses with excess silica and minor Fe-Mg components. This mineral assemblage is similar to the “andesitic” material found in the Caddo County IAB iron meteorite for which a partial melt origin has been proposed. The fairly uniform compositions of Cr diopside (Ca44Mg46Fe10) and Na plagioclase (Or2.5Ab90.0An7.5 to Or3.5Ab96.1An0.4) in Colomera interior inclusions and the angular boundaries between minerals and metal suggest that diopside and plagioclase partially crystallized under near-equilibrium conditions from a common melt before emplacement into molten metal. The melt-crystal assemblage has been called “crystal mush.” The bulk compositions of the individual composite inclusions form an array between the most diopside-rich inclusion and plagioclase. This is consistent only with a simple mechanical mixing relationship, not a magmatic evolution series. We propose a model in which partly molten metal and crystal mush were mixed together by impact on the IIE parent body. Other models involving impact melting of the chondritic source material followed by growth of diopside and plagioclase do not easily explain near equilibrium growth of diopside and Na plagioclase, followed by rapid cooling. In the K-rich surface inclusion, K feldspar, orthopyroxene, and olivine were found together with diopside for the first time. K feldspar (sanidine, Or92.7Ab7.2An0.1 to Or87.3Ab11.0An1.7) occurs in an irregular veinlike region in contact with large orthopyroxene crystals of nearly uniform composition (Ca1.3Mg80.5Fe17.8 to Ca3.1Mg78.1Fe18.9) and intruding into a relict olivine with deformed-oval shape. Silica and subrounded Cr diopside are present within such K-feldspar regions. Some enrichments of the albite component have been detected at the end of curved elongated nodules of K feldspar intruded into the mafic silicates. The textural relationships suggest that a K-rich melt was present. A K-rich melt is neither the first melt of a chondritic system nor a differentiation product of a Na-rich partial melt of chondritic material. The K-rich material may have originated as a fluid phase that leached K from surrounding materials and segregated by a mechanism similar to that proposed for the Na-rich inclusions. 相似文献
109.
The ionospheric radiance and electron density observed by the tiny ionospheric photometer (TIP) and GPS occultation experiment
(GOX) payloads on FORMOSAT-3/COSMIC satellites are applied to determine the boundaries of the auroral oval and its width in
the winter nighttime ionosphere for both hemispheres. The TIP collects ionospheric emission at 135.6 nm due to electron impact
excitation, while the GOX offers ionospheric electron density profiles with radio occultation (RO) technique. Comparison between
them shows similar patterns of the plasma structure in the polar caps. The mean width of the auroral bands ranges between
about 2 and 11° latitude in the winter nighttime and it varies with longitudes. The comparison by month suggests that the
mean radius of the auroral ovals varies with the intensity of the auroral radiance. 相似文献
110.
Lin Liang-Fu Hsu Ho-Han Liu Char-Shine Chao Kuo-Han Ko Chia-Chun Chiu Shye-Dong Hsieh Hsin-Sung Ma Yu-Fang Chen Song-Chuen 《Marine Geophysical Researches》2019,40(4):619-633
Marine Geophysical Research - Strong ocean current influences a marine seismic survey and forces the streamer off-course from the survey line. The sideway drift of the streamer results in that the... 相似文献