Seismic study of crustal structure in Pennsylvania and New York*

1955 ◽  
Vol 45 (4) ◽  
pp. 303-325 ◽  
Author(s):  
Samuel Katz
Keyword(s):  
New York ◽  
Elastic Wave ◽  
Upper Mantle ◽  
Compressional Wave ◽  
Compressional Wave Velocity ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Central Pennsylvania ◽  
Significant Difference ◽  
Mohorovičić Discontinuity

Abstract Blasts at two quarries in northern New York and central Pennsylvania have been recorded to a distance of 309 km. The data indicate an essentially homogeneous, unlayered crust, with elastic wave velocities possibly increasing with depth. An average crustal thickness for the region is 34.4 km., with no indication of significant difference in thickness between the two areas. Observed compressional wave velocities for the crust are 6.39 and 6.31 km/sec. for New York, and 6.04 km/sec. for Pennsylvania. The corresponding shear wave velocities are 3.62 and 3.60 km/sec., and 3.61 km/sec. Average upper mantle velocities are 8.14 km/sec. for Pn and 4.69 km/sec. for Sn. The compressional wave velocity of anorthosite near Tahawus, N.Y., is 6.63 km/sec. No near-vertical reflections from the Mohorovičić discontinuity were observed.

SEISMIC STUDIES ON THE EASTERN SEABOARD OF CANADA: THE ATLANTIC COAST OF NOVA SCOTIA

1964 ◽  
Vol 1 (1) ◽  
pp. 10-22 ◽  
Author(s):  
D. L. Barrett ◽  
M. Berry ◽  
J. E. Blanchard ◽  
M. J. Keen ◽  
R. E. McAllister
Keyword(s):  
Nova Scotia ◽  
Upper Mantle ◽  
Atlantic Coast ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Crust And Upper Mantle ◽  
Compressional Waves ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Eastern Seaboard

The results of seismic refraction profiles on the Atlantic coast of Nova Scotia and on the continental shelf off Nova Scotia are presented. Compressional and shear waves have been observed in the crust and mantle and suggest that the thickness of the crust is about 34 km. The compressional wave velocities recorded in the main crust and upper mantle are 6.10 and 8.11 km s−1 respectively. No compressional waves with values of velocity between these values can be identified, and this suggests that any "intermediate" layer is thin or absent. The corresponding shear wave velocities are 3.68 and 4.53 km s−1. Values of Poisson's ratio in the crust and mantle are 0.22 and 0.28. Alternative models of the crust which, on the evidence of travel times, might fit the observed results are discussed.

scholarly journals Modified Fixed Wall Oedometer When Considering Stress Dependence of Elastic Wave Velocities

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6291
Author(s):  
Jong-Sub Lee ◽  
Geunwoo Park ◽  
Yong-Hoon Byun ◽  
Changho Lee
Keyword(s):  
Elastic Wave ◽  
Shear Wave ◽  
Compressional Wave ◽  
Stress Dependence ◽  
Bender Elements ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Vertical Effective Stress ◽  
Side Friction ◽  
Applied Stresses

A modified oedometer cell for measuring the applied stresses and elastic waves at the top and bottom of the specimen is developed to evaluate the effect of the side friction on the stress dependence of the elastic wave velocities. In the modified cell, two load cells are installed at the top and bottom plates, respectively. To generate and detect the compressional and shear waves, a pair of piezo disk elements and a pair of bender elements are mounted at both the top and bottom plates. Experimental results show that the stresses measured at the bottom are smaller than those measured at the top during the loading and vice versa during unloading, regardless of the densities and heights of the specimens. Under nearly saturated conditions, the compressional wave velocities remain almost constant for the entire stress state. With plotting stresses measured at top, the shear wave velocities during unloading are greater than those during loading, whereas with plotting stresses measured at bottom, the shear wave velocities during unloading are smaller than those during loading owing to the side friction. The vertical effective stress may be simply determined from the average values of the stresses measured at the top and bottom of the specimens.

SEISMIC STUDIES ON THE EASTERN SEABOARD OF CANADA: THE APPALACHIAN SYSTEM. I

1966 ◽  
Vol 3 (1) ◽  
pp. 89-109 ◽  
Author(s):  
G. N. Ewing ◽  
A. M. Dainty ◽  
J. E. Blanchard ◽  
M. J. Keen
Keyword(s):  
Upper Mantle ◽  
Intermediate Layer ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Compressional Wave Velocity ◽  
The West ◽  
Crust And Upper Mantle ◽  
Wave Velocities ◽  
Anticosti Island ◽  
Eastern Seaboard

The results of seismic refraction profiles in the Gulf of St. Lawrence and on the northwest and northeast coasts of Newfoundland are presented. The thickness of the crust is about 45 km in the region of the Gulf of St. Lawrence southwest of the Cabot Strait Trough, and off the northeast coast of Newfoundland east of the Long Range Mountains. One interpretation of the data suggests that the compressional wave velocities through the underlying mantle are 8.50 and 8.69 km s−1 respectively. An "intermediate" layer about 20 km thick is identified with compressional wave velocities of 7.35 and 7.52 km s−1 beneath these areas. A thinner crust, 33 km thick approximately, underlies the west coast of Newfoundland, and a crustal thickness of 35 km is postulated near Anticosti Island. The compressional wave velocity in the upper part of the mantle beneath this thinner crust is close to 8 km s−1. The intermediate layer thins and, possibly, pinches out in the vicinity of Anticosti Island and northwest Newfoundland. The results lead to the suggestion that we see within the crust and upper mantle the subsurface expression of the two-sided nature of the Appalachian system. The system shows no sign of quietly dying away beneath the northeastern coast of Newfoundland.

scholarly journals The structure of the lithosphere and upper mantle beneath the Eastern Mediterranean and Middle East

2020 ◽  
Vol 2 (3) ◽  
pp. 311-326 ◽  
Author(s):  
Dan McKenzie
Keyword(s):  
Middle East ◽  
Shear Wave ◽  
Upper Mantle ◽  
Eastern Mediterranean ◽  
Three Dimensional ◽  
Surface Velocity ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Surface Measurements ◽  
Lithosphere Thickness

AbstractSurface velocity measurements show that the Middle East is one of the most actively deforming regions of the continents. The structure of the underlying lithosphere and convecting upper mantle can be explored by combining three types of measurement. The gravity field from satellite and surface measurements is supported by the elastic properties of the lithosphere and by the underlying mantle convection. Three dimensional shear wave velocities can be determined by tomographic inversion of surface wave velocities. The shear wave velocities of the mantle are principally controlled by temperature, rather than by composition. The mantle composition can be obtained from that of young magmas. Application of these three types of observation to the Eastern Mediterranean and Middle East shows that the lithosphere thickness in most parts is no more than 50-70 km, and that the elastic thickness is less than 5 km. Because the lithosphere is so thin and weak the pattern of the underlying convection is clearly visible in the topography and gravity, as well as controlling the volcanism. The convection pattern takes the form of spokes: lines of hot upwelling mantle, joining hubs where the upwelling is three dimensional. It is the same as that seen in high Rayleigh number laboratory and numerical experiments. The lithospheric thicknesses beneath the seafloor to the SW of the Hellenic Arc and beneath the NE part of the Arabian Shield are more than 150 km and the elastic thicknesses are 30–40 km.

Sonic logging of compressional‐wave velocities in a very slow formation

Geophysics ◽  
1995 ◽  
Vol 60 (6) ◽  
pp. 1627-1633 ◽  
Author(s):  
Bart W. Tichelaar ◽  
Klaas W. van Luik
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Compressional Wave ◽  
P Wave ◽  
Dipole Source ◽  
Frequency Spectra ◽  
Unconsolidated Sands ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Sonic Logging

Borehole sonic waveforms are commonly acquired to produce logs of subsurface compressional and shear wave velocities. To this purpose, modern borehole sonic tools are usually equipped with various types of acoustic sources, i.e., monopole and dipole sources. While the dipole source has been specifically developed for measuring shear wave velocities, we found that the dipole source has an advantage over the monopole source when determining compressional wave velocities in a very slow formation consisting of unconsolidated sands with a porosity of about 35% and a shear wave velocity of about 465 m/s. In this formation, the recorded compressional refracted waves suffer from interference with another wavefield component identified as a leaky P‐wave, which hampers the determination of compressional wave velocities in the sands. For the dipole source, separation of the compressional refracted wave from the recorded waveforms is accomplished through bandpass filtering since the wavefield components appear as two distinctly separate contributions to the frequency spectrum: a compressional refracted wave centered at a frequency of 6.5 kHz and a leaky P‐wave centered at 1.3 kHz. For the monopole source, the frequency spectra of the various waveform components have considerable overlap. It is therefore not obvious what passband to choose to separate the compressional refracted wave from the monopole waveforms. The compressional wave velocity obtained for the sands from the dipole compressional refracted wave is about 2150 m/s. Phase velocities obtained for the dispersive leaky P‐wave excited by the dipole source range from 1800 m/s at 1.0 kHz to 1630 m/s at 1.6 kHz. It appears that the dipole source has an advantage over the monopole source for the data recorded in this very slow formation when separating the compressional refracted wave from the recorded waveforms to determine formation compressional wave velocities.

VELOCITY OF COMPRESSIONAL WAVES IN POROUS MEDIA AT PERMAFROST TEMPERATURES

Geophysics ◽  
1968 ◽  
Vol 33 (4) ◽  
pp. 584-595 ◽  
Author(s):  
A. Timur
Keyword(s):  
Porous Media ◽  
Wave Velocity ◽  
Compressional Wave ◽  
Freezing Process ◽  
Rock Matrix ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
Average Equation ◽  
Wave Velocities ◽  
Time Average

Measurements of velocity of compressional waves in consolidated porous media, conducted within a temperature range of 26 °C to −36 °C, indicate that: (1) compressional wave velocity in water‐saturated rocks increases with decreasing temperature whereas it is nearly independent of temperature in dry rocks; (2) the shapes of the velocity versus temperature curves are functions of lithology, pore structure, and the nature of the interstitial fluids. As a saturated rock sample is cooled below 0 °C, the liquid in pore spaces with smaller surface‐to‐volume ratios (larger pores) begins to freeze and the liquid salinity controls the freezing process. As the temperature is decreased further, a point is reached where the surface‐to‐volume ratio in the remaining pore spaces is large enough to affect the freezing process, which is completed at the cryohydric temperature of the salts‐water system. In the ice‐liquid‐rock matrix system, present during freezing, a three‐phase, time‐average equation may be used to estimate the compressional wave velocities. Below the cryohydric temperature, elastic wave propagation takes place in a solid‐solid system consisting of ice and rock matrix. In this frozen state, the compressional wave velocity remains constant, has its maximum value, and may be estimated through use of the two‐phase time average equation. Limited field data for compressional wave velocities in permafrost indicate that pore spaces in permafrost contain not only liquid and ice, but also gas. Therefore, before attempting to make velocity estimates through the time‐average equations, the natures and percentages of pore saturants should be investigated.

FLUID SATURATION EFFECTS ON DYNAMIC ELASTIC PROPERTIES OF SEDIMENTARY ROCKS

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 895-921 ◽  
Author(s):  
A. R. Gregory
Keyword(s):  
Shear Wave ◽  
Elastic Moduli ◽  
Sedimentary Rocks ◽  
Compressional Wave ◽  
Reflection Coefficients ◽  
High Porosity ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Fluid Saturation ◽  
Saturation Effects

The influence of saturation by water, oil, gas, and mixtures of these fluids on the densities, velocities, reflection coefficients, and elastic moduli of consolidated sedimentary rocks was determined in the laboratory by ultrasonic wave propagation methods. Twenty rock samples varying in age from Pliocene to early Devonian and in porosity from 4 to 41 percent were tested under uniform pressures equivalent to subsurface depths of 0 to 18,690 ft. Fluid saturation effects on compressional‐wave velocity are much larger in low‐porosity than in high‐porosity rocks; this correlation is strengthened by elevated pressures but is absent at atmospheric pressure. At a frequency of 1 MHz, the shear‐wave velocities do not always decrease when liquid pore saturants are added to rocks as theorized by Biot; agreement with theory is dependent upon pressure, porosity, fluid‐mineral chemical interactions, and the presence of microcracks in the cementing material. Experimental results support the belief that lower compressional‐wave velocities and higher reflection coefficients are obtained in sedimentary rocks that contain gas. Replacing pore liquids with gas markedly reduces the elastic moduli of rocks, and the effect is enhanced by decreasing pressure. As a rule, the moduli decrease as the porosity increases; Poisson’s ratio is an exception to the rule. Liquid and gas saturation in consolidated rocks can also be distinguished by the ratio of compressional and shear wave velocities [Formula: see text]. The potential diagnostic value of elastic moduli in seismic exploration may stimulate interest in the use of shear‐wave reflection methods in the field.

Measured and calculated elastic wave velocities for xenoliths from the lower crust and upper mantle

1990 ◽  
Vol 173 (1-4) ◽  
pp. 207-210 ◽  
Author(s):  
Ian Jackson ◽  
Roberta L. Rudnick ◽  
S.Y. O'Reilly ◽  
C. Bezant
Keyword(s):  
Elastic Wave ◽  
Upper Mantle ◽  
Lower Crust ◽  
Crust And Upper Mantle ◽  
Wave Velocities

scholarly journals Shear wave velocities in the upper mantle of the Western Alps: new constraints using array analysis of seismic surface waves

2017 ◽  
Vol 210 (1) ◽  
pp. 321-331 ◽  
Author(s):  
Chao Lyu ◽  
Helle A. Pedersen ◽  
Anne Paul ◽  
Liang Zhao ◽  
Stefano Solarino ◽  
...  
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Upper Mantle ◽  
Western Alps ◽  
Array Analysis ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Seismic Surface Waves

Estimation of Dry-Rock Elastic Moduli Based on the Simulation of Mud-Filtrate Invasion Effects on Borehole Acoustic Logs

2009 ◽  
Vol 12 (06) ◽  
pp. 898-911 ◽  
Author(s):  
Tobiloluwa B. Odumosu ◽  
Carlos Torres-Verdín ◽  
Jesús M. Salazar ◽  
Jun Ma ◽  
Benjamin Voss ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Shear Wave ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Compressional Wave ◽  
Shear Rigidity ◽  
Spatial Distributions ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Mud Filtrate

Summary Reliable estimates of dry-rock elastic properties are critical to the accurate interpretation of the seismic response of hydrocarbon reservoirs. We describe a new method for estimating elastic moduli of rocks in-situ based on the simulation of mud-filtrate invasion effects on resistivity and acoustic logs. Simulations of mud-filtrate invasion account for the dynamic process of fluid displacement and mixing between mud-filtrate and hydrocarbons. The calculated spatial distributions of electrical resistivity are matched against resistivity logs by adjusting the underlying petrophysical properties. We then perform Biot-Gassmann fluid substitution on the 2D spatial distributions of fluid saturation with initial estimates of dry-bulk (kdry) modulus and shear rigidity (µdry) and a constraint of Poisson's ratio (?d) typical of the formation. This process generates 2D spatial distributions of compressional and shear-wave velocities and density. Subsequently, sonic waveforms are simulated to calculate shear-wave slowness. Initial estimates of the dry-bulk modulus are progressively adjusted using a modified Gregory-Pickett (1963) solution of Biot's (1956) equation to estimate a shear rigidity that converges to the well-log value of shear-wave slowness. The constraint on dynamic Poisson's ratio is then removed and a refined estimate of the dry-bulk modulus is obtained by both simulating the acoustic log (monopole) and matching the log-derived compressional-wave slowness. This technique leads to reliable estimates of dry-bulk moduli and shear rigidity that compare well to laboratory core measurements. Resulting dry-rock elastic properties can be used to calculate seismic compressional-wave and shear-wave velocities devoid of mud-filtrate invasion effects for further seismic-driven reservoir-characterization studies.

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