scholarly journals A Simple Method for P-waves Velocity Estimation Using Pore Attributes Shape Factor and Tortuosity

2020 ◽  
Vol 9 (2) ◽  
pp. 83-89
Author(s):  
Muhammad Burhannudinnur ◽  
Suryo Prakoso
Keyword(s):  
Wave Velocity ◽  
Shape Factor ◽  
Empirical Relationship ◽  
Velocity Estimation ◽  
P Wave ◽  
Simple Relationship ◽  
P Waves ◽  
Simple Method ◽  
P Wave Velocity ◽  
Relationship Of

Several researchers have arranged an approach to estimating the P-wave velocity, but none of them specifically relates to the pore attribute. Pore attributes are one of the main factors that affect pore complexity and rock quality. If P-wave velocity is influenced by the pore complexity, then it should be possible to arrange a simple relationship of P-wave velocity with the pore attribute. This study is intended to construct an empirical relationship of P-wave velocity with a combination of pore attributes, shape factor, and tortuosity (Fsτ) so that the P-wave velocity can be easily estimated. This study used two sandstone datasets from 2 different basins, which are the northern part of the West Java basin and the Kutai basin. This research shows that a simple empirical equation can be arranged to relate the P-wave velocity with Fsτ. This relationship provides a good correlation coefficient. It offers an easy and straightforward approach to estimating P-wave

scholarly journals Estimation of Geodynamic Properties using Seismic Techniques at a Steel Rolling Factory, Northwestern Gulf of Suez, Egypt

2020 ◽  
Vol 8 (6) ◽  
pp. 1785-1794
Keyword(s):  
Wave Velocity ◽  
Seismic Waves ◽  
Seismic Refraction ◽  
Industrial Area ◽  
P Wave ◽  
Gulf Of Suez ◽  
S Wave ◽  
P Waves ◽  
Steel Rolling ◽  
P Wave Velocity

The objective of the current investigations is to estimate the dynamic geotechnical properties necessary for evaluating the conditions of the subsurface in order to make better decisions for economic and safe designs of the proposed structures at a Steel Rolling Factory, Ataqa Industrial Area, Northwestern Gulf of Suez, Egypt. To achieve this purpose, four seismic refraction profiles were conducted to measure the velocity of primary seismic waves (P-waves) and four profiles were conducted using Multichannel Analysis of Surface Waves (MASW) technique in the same locations of refraction profiles to measure the velocity of shear waves (S-waves). SeisImager/2D Software Package was used in the analysis of the measured data. Data processing and interpretation reflect that the subsurface section in the study area consists of two layers, the first layer is a thin surface layer ranges in thickness from 1 to 4 meters with P-wave velocity ranges from 924 m/s to 1247 m/s and S-wave velocity ranges from 530 m/s to 745 m/s. The second layer has a P-wave velocity ranges from 1277 m/s to 1573 m/s and the S-wave velocity ranges from 684 m/s to 853 m/s. Geotechnical parameters were calculated for both layers. Since elastic moduli such as Poisson’s ratio, shear modulus, Young’s modulus, and bulk’s modulus were calculated. Competence scales such as material index, stress ratio, concentration index, and density gradient were calculated also. In addition, the ultimate and allowable bearing capacities

ATTENUATION MEASUREMENTS IN THE FIELD

Geophysics ◽  
1966 ◽  
Vol 31 (3) ◽  
pp. 562-569 ◽  
Author(s):  
J. Cl. De Bremaecker ◽  
Richard H. Godson ◽  
Joel S. Watkins
Keyword(s):  
Wave Velocity ◽  
Reasonable Agreement ◽  
P Wave ◽  
Head Wave ◽  
Published Data ◽  
Complex Shear Modulus ◽  
P Waves ◽  
P Wave Velocity ◽  
Complex Shear ◽  
Aa Lava

The amplitudes of the P head wave were measured on an aa lava flow, on unconsolidated cinders, and on compact limestone. The data are satisfied by the equation [Formula: see text], where A is the amplitude, d the distance, [Formula: see text] the attenuation coefficient for P waves, ν the frequency, and α the P wave velocity. By assuming a complex shear modulus μ* but a real λ one finds [Formula: see text], where β is the shear wave velocity. This formula is in reasonable agreement with published data.

A fall in P-wave velocity before the Gisborne, New Zealand, earthquake of 1966

1974 ◽  
Vol 64 (5) ◽  
pp. 1501-1507 ◽  
Author(s):  
D. J. Sutton
Keyword(s):  
New Zealand ◽  
Wave Velocity ◽  
Significant Variation ◽  
Arrival Time ◽  
P Wave ◽  
Time Interval ◽  
P Waves ◽  
Arrival Times ◽  
P Wave Velocity ◽  
Seismograph Station

Abstract A fall in P-wave velocity before the Gisborne earthquake of March 4, 1966 is indicated by arrival-time residuals of P waves from distant earthquakes recorded at the Gisborne seismograph station. Residuals were averaged over 6-month intervals from 1964 to 1968 and showed an increase of about 0.5 sec, implying later arrival times. The change began about 480 days before the earthquake. This precursory time interval is about that expected for an earthquake of this magnitude (ML = 6.2), but unlike most other reported instances, there was no obvious delay between the return of the velocity to normal and the occurrence of the earthquake. Similar analyses were carried out over the same period for two other New Zealand seismograph stations; at Karapiro there was no significant variation in mean residuals, and at Wellington the scatter was too large for the results to be meaningful. The Gisborne earthquake had a focus in the lower crust, about 25 km deep and was deeper than other events for which such precursory drops in P-wave velocity have been reported.

The use of critical porosity concept for P-wave velocity estimation: A field case

2020 ◽  
Author(s):  
Suryo Prakoso ◽  
Muhammad Burhannudinnur ◽  
Sigit Rahmawan ◽  
Ghanima Yasmaniar ◽  
Syamsul Irham
Keyword(s):  
Wave Velocity ◽  
Velocity Estimation ◽  
P Wave ◽  
Critical Porosity ◽  
Field Case ◽  
P Wave Velocity

Seismological studies in a rock body at Chalk River, Ontario and their relation to fractures

1982 ◽  
Vol 19 (8) ◽  
pp. 1535-1547 ◽  
Author(s):  
C. Wright
Keyword(s):  
Wave Velocity ◽  
Test Site ◽  
P Wave ◽  
Seismic Velocities ◽  
S Wave ◽  
P Waves ◽  
Rock Body ◽  
Near Surface ◽  
Wave Velocities ◽  
P Wave Velocity

Seismological experiments have been undertaken at a test site near Chalk River, Ontario that consists of crystalline rocks covered by glacial sediments. Near-surface P and S wave velocity and amplitude variations have been measured along profiles less than 2 km in length. The P and S wave velocities were generally in the range 4.5–5.6 and 2.9–3.2 km/s, respectively. These results are consistent with propagation through fractured gneiss and monzonite, which form the bulk of the rock body. The P wave velocity falls below 5.0 km/s in a region where there is a major fault and in an area of high electrical conductivity; such velocity minima are therefore associated with fracture systems. For some paths, the P and 5 wave velocities were in the ranges 6.2–6.6 and 3.7–4.1 km/s, respectively, showing the presence of thin sheets of gabbro. Temporal changes in P travel times of up to 1.4% over a 12 h period were observed where the sediment cover was thickest. The cause may be changes in the water table. The absence of polarized SH arrivals from specially designed shear wave sources indicates the inhomogeneity of the test site. A Q value of 243 ± 53 for P waves was derived over one relatively homogeneous profile of about 600 m length. P wave velocity minima measured between depths of 25 and 250 m in a borehole correlate well with the distribution of fractures inferred from optical examination of borehole cores, laboratory measurements of seismic velocities, and tube wave studies.

scholarly journals Comparing ray-theoretical and finite-frequency teleseismic traveltimes: implications for constraining the ratio of S-wave to P-wave velocity variations in the lower mantle

2020 ◽  
Vol 224 (3) ◽  
pp. 1540-1552
Author(s):  
Carlos A M Chaves ◽  
Jeroen Ritsema ◽  
Paula Koelemeijer
Keyword(s):  
North America ◽  
Wave Velocity ◽  
Lower Mantle ◽  
P Wave ◽  
Finite Frequency ◽  
S Wave ◽  
P Waves ◽  
Long Period ◽  
P Wave Velocity ◽  
The Pacific

SUMMARY A number of seismological studies have indicated that the ratio R of S-wave and P-wave velocity perturbations increases to 3–4 in the lower mantle with the highest values in the large low-velocity provinces (LLVPs) beneath Africa and the central Pacific. Traveltime constraints on R are based primarily on ray-theoretical modelling of delay times of P waves (ΔTP) and S waves (ΔTS), even for measurements derived from long-period waveforms and core-diffracted waves for which ray theory (RT) is deemed inaccurate. Along with a published set of traveltime delays, we compare predicted values of ΔTP, ΔTS, and the ΔTS/ΔTP ratio for RT and finite-frequency (FF) theory to determine the resolvability of R in the lower mantle. We determine the FF predictions of ΔTP and ΔTS using cross-correlation methods applied to spectral-element method waveforms, analogous to the analysis of recorded waveforms, and by integration using FF sensitivity kernels. Our calculations indicate that RT and FF predict a similar variation of the ΔTS/ΔTP ratio when R increases linearly with depth in the mantle. However, variations of R in relatively thin layers (< 400 km) are poorly resolved using long-period data (T > 20 s). This is because FF predicts that ΔTP and ΔTS vary smoothly with epicentral distance even when vertical P-wave and S-wave gradients change abruptly. Our waveform simulations also show that the estimate of R for the Pacific LLVP is strongly affected by velocity structure shallower in the mantle. If R increases with depth in the mantle, which appears to be a robust inference, the acceleration of P waves in the lithosphere beneath eastern North America and the high-velocity Farallon anomaly negates the P-wave deceleration in the LLVP. This results in a ΔTP of about 0, whereas ΔTS is positive. Consequently, the recorded high ΔTS/ΔTP for events in the southwest Pacific and stations in North America may be misinterpreted as an anomalously high R for the Pacific LLVP.

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