共查询到20条相似文献，搜索用时 62 毫秒
1.
In comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions for mathematical equivalence then follow in a natural sequence. Laboratory measurements are made on a variety of rock samples to indicate the type of comparison and correlation expected from field measurements. Results indicate that frequency domain and phase measurements are equivalent, but two frequency domain measurements are needed to produce the same amount of polarization information as a single phase measurement. Frequency and time domain measurements will be similar but never equivalent due to the basic differences in their respective parameter definitions. 相似文献
2.
Field measurements of seismic P-wave velocities have been carried out by surface to surface refraction measurements for five different rock types. Subweathering velocities are surprisingly high and range from 5.0 km/sec in quartz monzonite to 6.2 km/sec in amphibolite in agreement with the proposal of Nur and Simmons for water-saturated low-porosity rocks. Maximum velocities found are 6.1 km/sec for quartz monzonite, 5.8 km/sec for granite gneiss, 6.4 km/sec for syenite, 6.4 km/sec for anorthosite, and 7.0 km/sec for amphibolite, and maximum depth for these velocities is 1.3 km. We conclude as follows: (1) field measurements correspond well with laboratory measurements but true velocity may be slightly higher than laboratory measurements, (2) shallow velocities are much higher than older laboratory measurements but agree well with recent laboratory measurements on water-saturated samples, (3) velocities much less than 6 km/sec seem unlikely in the crust unless in an area of extreme tectonic activity, (4) velocities of 6.5–6.7 km/sec commonly reported for the lower continental crust probably correspond to rocks less mafic than basalt or gabbro. 相似文献
3.
Chulsang Yoo Eunho Ha 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(3):287-297
In this study, the effect of zero measurements on the spatial correlation function of rainfall is analyzed for the quantification
of a rainfall field. The use of a bivariate mixed distribution function made it possible to analyze and compare the spatial
correlation functions for these three different data sets: only the positive measurements at both gauge locations, positive
measurements at either one or both gauge locations, and all measurements including zero at both locations. As an example,
the spatial correlation functions are derived for the Geum River Basin, Korea and evaluated for the wet and dry seasons, respectively.
Results show that the effect of zero measurements on spatial correlation structures is significant during the wet season,
when the inter-station correlations were estimated significantly lower than those during the dry season. It was also found
that only the case considering positive measurements are valid for the quantification of rainfall field. Even during the wet
season, the inter-station correlation coefficients derived by considering the zero measurements show their high variability
along with many abnormally looking high estimates, which made the quantification of the spatial correlation function become
very ambiguous. 相似文献
4.
Jeffrey L. Bada E. Hoopes D. Darling Graham Dungworth Henk J. Kessels Keith A. Kvenvolden David J. Blunt 《Earth and Planetary Science Letters》1979,43(2):265-268
Enantiomeric measurements for aspartic acid, glutamic acid, and alanine in twenty-one different fossil bone samples have been carried out by three different laboratories using different analytical methods. These inter-laboratory comparisons demonstrate that D/L aspartic acid measurements are highly reproducible, whereas the enantiomeric measurements for the other amino acids show a wide variation between the three laboratories. At present, aspartic acid measurements are the most suitable for racemization dating of bone because of their superior analytical precision. 相似文献
5.
W.J. MO
CICKI 《Geophysical Prospecting》1987,35(4):393-423
Theoretical and practical aspects of a new method for underground cavity localization are presented. The method is based on shallow temperature measurements. It is shown that such measurements can complement the geophysical methods most commonly used for cavity location. The results from finite-difference numerical calculations indicate possible origins of temperature anomalies–the existence of which is confirmed experimentally, primarily by field measurements. Temperature anomalies up to 1°C have been recorded over underground cavities. A satisfactory agreement between measurements and theory is found. 相似文献
6.
A local geodetic network of 20 points was established in 1988 around the Seiyal fault for monitoring lateral movements. Two levellinglines, crossing the fault, were prepared for monitoring vertical movements. The initial horizontal geodetic measurements were carried out in March 1989. The measurements were repeated twice a year. The initial vertical geodetic measurements (levelling) were carried out in November 1989 and repeated in November 1990.Four horizontal geodetic measurements and two levelling measurements were analysed. The results revealed remarkable horizontal and vertical changes during the period of measurement. 相似文献
7.
The attack on the World Trade Center (WTC) resulted in the destruction of buildings, and the release of tons of dust and debris into the environment. As part of the effort to characterize the environmental impact of the WTC collapse, Mussel Watch Program trace element measurements from the Hudson–Raritan Estuary (HRE) were assessed for the years before (1986–2001) and after (2001–2005) the attack. Trace element measurements in the HRE were significantly higher than Mussel Watch measurements taken elsewhere in the Nation. Post-attack trace element measurements were not significantly different from pre-attack measurements. The impacts of WTC collapse may have been obscured by high ambient levels of trace elements in the HRE. 相似文献
8.
V. V. Kopeikin 《Geomagnetism and Aeronomy》2014,54(1):117-126
Spectral measurements of radiowaves emitted by artificial ball lightning are presented. The measurements were carried out using two different facilities: a pulsed power generator (PPG) and a three-contour Tesla transformer. The results of these measurements confirm the hypothesis that ball lightning is a self-oscillator of high-voltage pulses in the radio range. 相似文献
9.
A combination of DC-resistivity sounding and profiling measurements can be used to obtain the maximum information about distribution of resistivities in the earth. Combined sounding-profiling measurements with the AMN, MNB arrays are considered. The resistivity data from such measurements can be presented as: (a) normal sounding curves, (b) combined sounding-profiling curves, (c) profiling curves, (d) pseudo-sections, or as transformations obtained by the so-called gradient processing, to emphasize the influence of the target objects. The examples chosen from numerical modeling and field tests show the efficiency of measurements with three-electrode arrays to accurately locate thin conductors and contacts of lithological units of different resistivities. An interpreted cross-section is compared with the results of other geophysical measurements (VLF-R, dipole EM, Δ, IP) showing good correlation. 相似文献
10.
Water exchange between surface water and groundwater can modulate or generate ecologically important fluxes of solutes across the sediment‐water interface. Seepage meters can directly measure fluid flux, but mechanical resistance and surface water dynamics may lead to inaccurate measurements. Tank experiments were conducted to determine effects of mechanical resistance on measurement efficiency and occurrence of directional asymmetry that could lead to erroneous net flux measurements. Seepage meter efficiency was high (average of 93%) and consistent for inflow and outflow under steady flow conditions. Wave effects on seepage meter measurements were investigated in a wave flume. Seepage meter net flux measurements averaged 0.08 cm/h—greater than the expected net‐zero flux, but significantly less than theoretical wave‐driven unidirectional discharge or recharge. Calculations of unidirectional flux from pressure measurements (Darcy flux) and theory matched well for a ratio of wave length to water depth less than 5, but not when this ratio was greater. Both were higher than seepage meter measurements of unidirectional flux made with one‐way valves. Discharge averaged 23% greater than recharge in both seepage meter measurements and Darcy calculations of unidirectional flux. Removal of the collection bag reduced this net discharge. The presence of a seepage meter reduced the amplitude of pressure signals at the bed and resulted in a nearly uniform pressure distribution beneath the seepage meter. These results show that seepage meters may provide accurate measurements of both discharge and recharge under steady flow conditions and illustrate the potential measurement errors associated with dynamic wave environments. 相似文献
11.
12.
A. V. Mordvinov 《Geomagnetism and Aeronomy》2010,50(8):933-936
A comparative analysis of measurements of total solar flux in the active cavity radiometer irradiance monitor (ACRIM) and
Physikalisch-Meteorologisches Observatorium Davos (PMOD) scales was performed. An analysis of integrated differences of simultaneous
measurements of solar flux made it possible to estimate the systematic differences that can lead to the accumulation large
errors with time. The measurements of solar flux in ACRIM and PMOD scales were reduced to an intermediate radiometric scale
through data correction for systematic errors. The corrected measurements in the unified scale were consistent and there is
a compromise between initial data sets. The measurements in the intermediate scale indicate changes in solar flux between
the minima of solar activity in 1986, 1996, and 2008. The amplitude of these variations is comparable with uncertainty in
their long-term trends, which questions earlier obtained estimates for secular variations of solar luminosity. 相似文献
13.
Spatially and temporally distributed measurements of processes, such as baseflow at the watershed scale, come at substantial equipment and personnel cost. Research presented here focuses on building a crowdsourced database of inexpensive distributed stream stage measurements. Signs on staff gauges encourage citizen scientists to voluntarily send hydrologic measurements (e.g., stream stage) via text message to a server that stores and displays the data on the web. Based on the crowdsourced stream stage, we evaluate the accuracy of citizen scientist measurements and measurement approach. The results show that crowdsourced data collection is a supplemental method for collecting hydrologic data and a promising method of public engagement. 相似文献
14.
I. Stuart McDermid 《Surveys in Geophysics》1987,9(2):107-122
This review considers the requirements and possibilities for the development of a ground-based network for long-term observations of the atmosphere. This network would be specifically designed to provide early detection of changes in the composition and structure of the stratosphere. The species and parameters identified as being important and amenable to ground-based measurements are summarized, as are the currently available techniques capable of making the required measurements. Ultraviolet laser remote sensing is identified as the most promising technique for the measurement of ozone and temperature profiles which are considered to have the highest priority for network measurements. The laser techniques, and the research at JPL Table Mountain Observatory, to implement ozone and temperature measurements are discussed in greater detail. 相似文献
15.
V. L. Khalipov A. E. Stepanov G. A. Kotova S. E. Kobyakova V. V. Bogdanov A. B. Kaisin V. A. Panchenko 《Geomagnetism and Aeronomy》2016,56(5):535-544
Vertical and horizontal plasma drifts are investigated during the polarization jet (PJ) detection in the F2 ionospheric layer based on the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations. It is shown that the velocities of vertical and horizontal drifts are significantly higher than the background motion during PJ observation periods. The ionospheric plasma motion direction changes from upward to downward on the polar edge of the main ionospheric trough. Doppler measurements on the DPS-4 ionosondes are compared with the simultaneous measurements of the plasma drift on the DMSP satellites during their passage near the Yakutsk meridian. The two kinds of measurements are in good agreement with each other. During the magnetic storm of June 23, 2005, by measurements of the DMSP satellites, the velocities of upward plasma flows were 1.0–1.4 km/s at a satellite altitude of 850 km. In the ionospheric F region, this speed corresponds to 150 m/s. According to satellite measurements, the westward drift velocity reached 2.5 km/s. The development of the polarization jet in the ionosphere was accompanied by a tenfold decrease in the electron density in 15–30 min. 相似文献
16.
A high sensitivity thermometer using a thermistor sensing element was designed for practical measurements in the field. The most suitable procedures for the elimination of diurnal and seasonal variation of temperature, the influence of vegetation cover and of other effects were investigated. Positive results of geothermic measurements have been acquired on sulfide deposits. By far the most important results of geothermic measurements have been obtained in hydrogeological problems, e.g. the investigation of circulation of underground water. In the case of prospection for cold mineral waters the combination of geothermic measurements with gasometric analyses is very useful. As the classical domain for geothermic investigation, prospection for hot water is to be mentioned. 相似文献
17.
《Journal of Applied Geophysics》2006,58(3):188-201
Characterisation and sampling of coarse heterogeneous soils is often impossible using common geotechnical in situ tests once the soil contains particles with a diameter larger than a few decimetres. In this situation geophysical techniques—and particularly electrical measurements—can act as an alternative method for obtaining information about the ground characteristics. This paper deals with the use of electrical tomography on heterogeneous diphasic media consisting of resistive inclusions embedded in a conductive matrix. The adopted approach articulates in three steps: numerical modelling, measurements on a small-scale physical model, and field measurements. Electrical measurements were simulated using finite element analyses, on a numerical model containing a random concentration of inclusions varying from 0% to 40%. It is shown that for electrode spacing 8 times greater than the radius of inclusions, the equivalent homogeneous resistivity is obtained. In this condition, average measured resistivity is a function of the concentration of inclusions, in agreement with the theoretical laws. To apply these results on real data, a small-scale physical model has been built, where electrical measurements were conducted both on the model and on each phase. From these laboratory measurements, a very satisfying estimation of the percentage of inclusions has been obtained. Finally, the methodology applied to a real experimental site composed of alluvial fan deposits made of limestone rocks embedded in a clayey matrix. The estimated percentage of rock particles obtained via electrical measurements was in accordance with the real grain size distribution. 相似文献
18.
Oceanographic climatology is widely used in different applications, such as climate studies, ocean model validation and planning of naval operations. Conventional climatological estimates are based on historic measurements, typically by averaging the measurements and thereby smoothing local phenomena. Such phenomena are often local in time and space, but crucial to some applications. Here, we propose a new method to estimate time-calibrated oceanographic profiles based on combined historic and real-time measurements. The real-time measurements may, for instance, be SAR pictures or autonomous underwater vehicles providing temperature values at a limited set of depths. The method employs empirical orthogonal functions and clustering on a training data set in order to divide the ocean into climatological regions. The real-time measurements are first used to determine what climatological region is most representative. Secondly, an improved estimate is determined using an optimisation approach that minimises the difference between the real-time measurements and the final estimate. 相似文献
19.
Three triangulation and trilateration micro networks in the seismic region of Ljubljana city, for the determination of horizontal and vertical movements, have been measured for the fourth time. GPS measurements have been included into the networks for the first time. The problem of the distance measurements was solved with the precise distancemeter Kern Mekometer ME 5000, angle measurements have been done with the electronic theodolite Kern E2. The problem of the orientation of the separated local networks was solved with GPS measurements. The results show that displacement in all three nets are not in the direction of the local fault but in the direction of the Sava fault and at the same time in the direction of the edge of the Peradriatic plate. 相似文献
20.
Summary In brief a newly developed freezing nuclei meter is described. Results of measurements made with this instrument in New Jersey, California and in the Thule area, Greenland, are shown. These data are compared with measurements of condensation nuclei, simultaneously made with the General Electric and the Aitkennuclei counters. Also the results obtained from some measurements of the lightscattering function of the aerosol in industrial areas near New York City are presented. 相似文献