scholarly journals On the direction of approach of microseismic waves

1935 ◽  
Vol 149 (866) ◽  
pp. 183-199 ◽  
Keyword(s):  
Rayleigh Waves ◽  
Turning Points ◽  
New Method ◽  
Ground Movements ◽  
The North ◽  
Vertical Displacements

It has been thought for some time that an examination of the relation between the phases of the horizontal and vertical displacements in microseisms would be of interest in showing how closely the oscillations compare with Rayleigh waves, but a practicable scheme for making the observations has only recently been developed. In the earlier attempts the turning points of consecutive oscillations were times during several minutes, but the accuracy attained by interpolation between the minute breaks was not high enough for reliable comparisons between the components. A solution of this difficulty has now been found in a modification of the method adopted by Leet, who has examined the relation between the horizontal and vertical phases of the microseisms recorded at Harvard Observatory, using comparisons of the movements exactly at the minute breaks . The application of this new method to the seisograms of Kew Observatory is described in the present paper. 2—Tabulation of the phases of the microseisms Fig. 1 shows portions of the records, obtained from the Galitzin seismographs at Kew on January 11, 1930, when the microseisms were very large. Upward movements on the seismograms correspond with ground movements to the north, to the east, and upwards. The direction of recording is from right to left.

scholarly journals A new method for correcting temperature log profiles in low-enthalpy plays

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Sandra Schumacher ◽  
Inga Moeck
Keyword(s):  
Input Parameter ◽  
New Method ◽  
Geothermal Resources ◽  
The North ◽  
Deep Wells ◽  
Thermal Disturbance ◽  
Drilling Operations ◽  
Crucial Information ◽  
Well Data ◽  
Drilling Time

Abstract Temperature logs recorded shortly after drilling operations can be the only temperature information from deep wells. However, these measurements are still influenced by the thermal disturbance caused by drilling and therefore do not represent true rock temperatures. The magnitude of the thermal disturbance is dependent on many factors such as drilling time, logging procedure or mud temperature. However, often old well reports lack this crucial information so that conventional corrections on temperature logs cannot be performed. This impedes the re-evaluation of well data for new exploration purposes, e.g. for geothermal resources. This study presents a new method to correct log temperatures in low-enthalpy play types which only requires a knowledge of the final depth of the well as an input parameter. The method was developed and verified using existing well data from an intracratonic sedimentary basin, the eastern part of the North German Basin. It can be transferred to other basins with little or no adjustment.

Disposal of the Dead at Point of Pines, Arizona

1965 ◽  
Vol 30 (4) ◽  
pp. 442-453 ◽  
Author(s):  
William J. Robinson ◽  
Roderick Sprague
Keyword(s):  
Material Culture ◽  
New Method ◽  
The South ◽  
Burial Practices ◽  
The North ◽  
Changing Patterns ◽  
The Dead

AbstractThe analysis of 975 burials indicates that the inhumations of the Point of Pines region conformed to the flexed Mogollon pattern prior to A.D. 1000. Subsequently, extended burials appeared concurrently with a complex of traits diffused from areas to the north. At the same time, cremation became established as a part of the mortuary complex as a result of contact with Hohokam peoples to the south. Additional evidence of this contact consists of Hohokam material culture items and a ball court. Ceremonial killing of the crematory vessels was extensively practiced and included a new method, notch-killing. The variability of forms and methods of disposal suggests rapidly changing patterns and alternatives in burial practices.

Rotated Power Spectra of Microseisms

1972 ◽  
Vol 9 (4) ◽  
pp. 325-338 ◽  
Author(s):  
N. N. Chandra ◽  
G. L. Cumming
Keyword(s):  
Ground Motion ◽  
North Pacific ◽  
Rayleigh Waves ◽  
Large Fraction ◽  
Power Spectra ◽  
Vertical Motion ◽  
Wave Interactions ◽  
The North ◽  
The Waves ◽  
The North Pacific

Cross-power and coherency as a function of period and azimuth have been calculated for several seismic stations during the course of a microseismic storm in the north Pacific. These data indicate that in addition to the predicted Rayleigh waves, a large fraction of the observed ground motion must be due to other wave types, most of which have predominantly vertical motion. The data indicate that the angle subtended by the source of the waves increases with distance, suggesting that wave interactions at the coastline may be a major factor in the observed disturbances on the continent.

Estimated Global Hydrographic Variability

2007 ◽  
Vol 37 (8) ◽  
pp. 1997-2008 ◽  
Author(s):  
Gaël Forget ◽  
Carl Wunsch
Keyword(s):  
Ocean Circulation ◽  
Large Fraction ◽  
World Ocean ◽  
Three Dimensional ◽  
Sea Surface Height ◽  
Sea Surface ◽  
The North ◽  
Salinity Variability ◽  
Vertical Displacements ◽  
Diffusive Processes

Abstract An estimate is made of the three-dimensional global oceanic temperature and salinity variability, omitting the seasonal cycle, both as a major descriptive element of the ocean circulation and for use in the error estimates of state estimation. Historical hydrography, recent data from the World Ocean Circulation Experiment, and Argo profile data are all used. Root-mean-square vertical displacements in the upper 300 m of the ocean are generally smaller than 50 m, except in energetic boundary currents and in the North Atlantic subpolar gyre. Variability in temperature and salinity is strongly correlated below the top 100 m. Salinity contributions to sea surface height variability appear more significant at low latitudes than expected, possibly resulting from advective and diffusive processes. Results are generally consistent with altimetric variability under two simple kinematic hypotheses, and much of the observed structure coincides with known dynamical features. A large fraction of the sea surface height variability is consistent with the hypothesis of dominance of the first baroclinic mode.

scholarly journals Adjusting the Influence Function Method for Subsidence Prediction

2013 ◽  
Vol 553 ◽  
pp. 59-66 ◽  
Author(s):  
Ali Saeidi ◽  
Olivier Deck ◽  
Marwan Al Heib ◽  
Thierry Verdel ◽  
Alain Rouleau
Keyword(s):  
Efficient Method ◽  
Influence Function ◽  
Function Method ◽  
Underground Mining ◽  
Building Damage ◽  
Ground Movement ◽  
Ground Movements ◽  
Influence Function Method ◽  
Vertical Displacements

Theextraction of ore and minerals by underground mining may induce groundsubsidence phenomena. These phenomena produce several types of ground movement likehorizontal and vertical displacements, ground curvature and horizontal groundstrain at the surface, and associated building damage in urban regions. Theinfluence function is a well-known and efficient method for the prediction ofthese movements, but its application is restricted to mining configurationswith the same influence angle around the mine. However, this angle may displaydifferent values when the mine is not horizontal or when other subsidenceevents already occurred near the considered mine.In this paper a methodology and analgorithm are developed, based on the traditional influence function method inorder to take into account different influence angles. This methodology isimplemented in the Mathematicasoftware and a case study is presented with data from the Lorraine iron minefield in France. Ground movements calculated with the developed methodologyshow a fair concordance with observed data.

scholarly journals A New Method to Define the VI-Ts Diagram Using Subpixel Vegetation and Soil Information: A Case Study over a Semiarid Agricultural Region in the North China Plain

Sensors ◽  
2008 ◽  
Vol 8 (10) ◽  
pp. 6260-6279 ◽  
Author(s):  
Zhigang Sun ◽  
Qinxue Wang ◽  
Bunkei Matsushita ◽  
Takehiko Fukushima ◽  
Zhu Ouyang ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
New Method ◽  
Agricultural Region ◽  
The North ◽  
The North China Plain ◽  
Soil Information

A new method to determine phase velocities of Rayleigh waves from microseisms

Geophysics ◽  
2004 ◽  
Vol 69 (6) ◽  
pp. 1535-1551 ◽  
Author(s):  
Ikuo Cho ◽  
Taku Tada ◽  
Yuzo Shinozaki
Keyword(s):  
Rayleigh Waves ◽  
Vertical Component ◽  
Field Tests ◽  
Spectral Ratio ◽  
New Method ◽  
Phase Velocities ◽  
Seismic Sensors ◽  
Time Histories ◽  
Theoretical Considerations ◽  
Incoherent Noise

We have developed a new method to determine phase velocities from the vertical component of microseisms recorded with an array of seismic sensors spaced around the circumference of a circle. We calculate two different time histories by taking the average of the seismograms with differing sets of weights for the sensor stations. The spectral ratio of these two time histories contains no information on the arrival directions or on the amplitudes of the incoming waves but depends solely on the phase velocities of the arriving modes. Theoretical considerations indicate that the effects of directional aliasing caused by the use of a finite number of sensors in the field implementation of our method are small in most situations except for short wavelengths. The presence of incoherent noise limits the efficacy of our method for long wavelengths. In field tests using arrays of three seismic sensors, we obtained appropriate estimates of phase velocities in the wavelength range from 5r to 30r where r, the array radius, was on the order of a few meters.

Structure of microseismic waves: estimation of direction of approach by comparison of vertical and horizontal components

1954 ◽  
Vol 223 (1152) ◽  
pp. 96-111 ◽  
Keyword(s):  
Rayleigh Waves ◽  
Vertical Component ◽  
Correlation Coefficients ◽  
Love Waves ◽  
The North ◽  
Wave Interference ◽  
Rayleigh And Love Waves ◽  
The Mean ◽  
East West ◽  
Phase Differences

Analysis of microseisms recorded at Kew Observatory on 8 to 10 October 1951 affords further confirmation of the wave-interference theory of microseism generation, and allows those of 8 to 10 October to be attributed to a fast-moving depression between the Azores and Iceland. Although the bearing of the microseism-generating area changes by more than 90° during the period investigated, there is no appreciable difference in the ratio of the mean ampli­tudes of the north-south and east-west horizontal components as would be expected if the microseisms consisted entirely of Rayleigh waves. An investigation of the phase differences between the three components, using Lee’s method, suggests that the microseisms consist of Rayleigh and Love waves in comparable proportions. Making use of this assumption, the vertical component, which is not affected by the Love waves, is correlated with the two horizontal components with an electronic correlating device, and the bearing of the microseism area can be deduced from the correlation coefficients. The calculated bearings agree reasonably well with those obtained from the meteorological charts. The bearing of a storm on 12 to 15 November 1945, studied in a previous paper, was also calculated satisfactorily.

scholarly journals Approximate formula for the H/V ratio of Rayleigh waves in incompressible orthotropic half-spaces coated by a thin elastic layer

2017 ◽  
Vol 39 (4) ◽  
pp. 365-374
Author(s):  
Pham Chi Vinh ◽  
Tran Thanh Tuan ◽  
Le Thi Hue
Keyword(s):  
Free Surface ◽  
Rayleigh Wave ◽  
Half Space ◽  
Rayleigh Waves ◽  
Elastic Layer ◽  
Approximate Formula ◽  
Elastic Half Space ◽  
Displacement Amplitude ◽  
Vertical Displacements ◽  
Thin Elastic Layer

This paper is concerned with the propagation of Rayleigh waves in an incompressible orthotropic elastic half-space coated with a thin incompressible orthotropic elastic layer. The main purpose of the paper is to establish an approximate formula for the Rayleigh wave H/V ratio (the ratio between the amplitudes of the horizontal and vertical displacements of Rayleigh waves at the traction-free surface of the layer). First, the relations between the traction amplitude vector and the displacement amplitude vector of Rayleigh waves at two sides of the interface between the layer and the half-space are created using the Stroh formalism and the effective boundary condition method. Then, an approximate formula for the Rayleigh wave H/V ratio of third-order in terms of dimensionless thickness of the layer has been derived by using these relations along with the Taylor expansion of the displacement amplitude vector of the thin layer at its traction-free surface. It is shown numerically that the obtained formula is a good approximate one. It can be used for extracting mechanical properties of thin films from measured values of the  Rayleigh wave H/V ratio.

scholarly journals A Comparison of Northern Hemisphere Atmospheric Rivers Detected by a New Image-Processing Based Method and Magnitude-Thresholding Based Methods

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 628 ◽  
Author(s):  
Guangzhi Xu ◽  
Xiaohui Ma ◽  
Ping Chang ◽  
Lin Wang
Keyword(s):  
Image Processing ◽  
North Atlantic ◽  
North Pacific ◽  
Detection Method ◽  
New Method ◽  
Detection Methods ◽  
Image Processing Algorithm ◽  
Atmospheric Rivers ◽  
The North ◽  
The North Pacific

A majority of the existing atmospheric rivers (ARs) detection methods is based on magnitude thresholding on either the integrated water vapor (IWV) or integrated vapor transport (IVT). One disadvantage of such an approach is that the predetermined threshold does not have the flexibility to adjust to the fast changing conditions where ARs are embedded. To address this issue, a new AR detection method is derived from an image-processing algorithm that makes the detection independent of AR magnitude. In this study, we compare the North Pacific and Atlantic ARs tracked by the new detection method and two widely used magnitude thresholding methods in the present day climate. The results show considerable sensitivities of the detected AR number, shape, intensities and their accounted IVT accumulations to different methods. In many aspects, ARs detected by the new method lie between those from the two magnitude thresholding methods, but stand out with a greater number of AR tracks, longer track durations, and stronger AR-related moisture transport in the AR tracks. North Pacific and North Atlantic ARs identified by the new method account for around 100–120 ×   10 3 kg/m/s IVT within the AR track regions, about 50 % more than the other two methods. This is primarily due to the fact that the new method captures the strong IVT signals more effectively.

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