IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of mechanical and civil engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in mechanical and civil engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Seismic data Interpretation On Dhodak field PakistanJamal Ahmad
I (Jamal Ahmad) presented this on 21 Feb, 2009 to defend my M.Phil dissertation in Geophysics at QAU, Islamabad, Pakistan. For more information about this, you may contact me directly at jamal.qau@gmail.com.
The oxford dictionary defines an attribute as, “a quality ascribed to any person or thing”. We have extended this definition to: “seismic attributes are all the information obtained from seismic data, either by direct measurements or by logical or experience based reasoning
In reflection seismology : aseismic attributes is a quality extracted or derived from seismic data that can be analyzed in order to enhance information that might be more subtle in a traditional seismic image , leading to a better geological or geophysical interpretation of the data
Over the past decades, we have witnessed attribute developments track breakthroughs in reflector acquisition and mapping, fault identification, bright spot identification, frequency loss, thin bed tuning, seismic stratigraphy.
Seismic data Interpretation On Dhodak field PakistanJamal Ahmad
I (Jamal Ahmad) presented this on 21 Feb, 2009 to defend my M.Phil dissertation in Geophysics at QAU, Islamabad, Pakistan. For more information about this, you may contact me directly at jamal.qau@gmail.com.
The oxford dictionary defines an attribute as, “a quality ascribed to any person or thing”. We have extended this definition to: “seismic attributes are all the information obtained from seismic data, either by direct measurements or by logical or experience based reasoning
In reflection seismology : aseismic attributes is a quality extracted or derived from seismic data that can be analyzed in order to enhance information that might be more subtle in a traditional seismic image , leading to a better geological or geophysical interpretation of the data
Over the past decades, we have witnessed attribute developments track breakthroughs in reflector acquisition and mapping, fault identification, bright spot identification, frequency loss, thin bed tuning, seismic stratigraphy.
Crustal Structure from Gravity and Magnetic Anomalies in the Southern Part of...Editor IJCATR
The gravity and magnetic data along the profile across the southern part of the Cauvery basin have been collected and the data is interpreted for crustal structure depths.The first profile is taken from Karikudito Embalecovering a distance of 50 km. The gravity lows and highs have clearly indicated various sub-basins and ridges. The density logs from ONGC, Chennai, show that the density contrast decreases with depth in the sedimentary basin, and hence, the gravity profiles are interpreted using variable density contrast with depth. From the Bouguer gravity anomaly, the residual anomaly is constructed by graphical method correlating with well data and subsurface geology. The residual anomaly profiles are interpreted using polygon and prismatic models. The maximum depths to the granitic gneiss basement are obtained as 3.00 km. The regional anomaly is interpreted as Moho rise towards coast. The aeromagnetic anomaly profiles are also interpreted for charnockite basement below the granitic gneiss group of rocks using prismatic model.
Estimation of Dipping Angles of Refracting Interfacesiosrjce
IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) multidisciplinary peer-reviewed Journal with reputable academics and experts as board member. IOSR-JESTFT is designed for the prompt publication of peer-reviewed articles in all areas of subject. The journal articles will be accessed freely online.
Crustal Structure from Gravity and Magnetic Anomalies in the Southern Part of...Editor IJCATR
The gravity and magnetic data along the profile across the southern part of the Cauvery basin have been collected and the data is interpreted for crustal structure depths.The first profile is taken from Karikudito Embalecovering a distance of 50 km. The gravity lows and highs have clearly indicated various sub-basins and ridges. The density logs from ONGC, Chennai, show that the density contrast decreases with depth in the sedimentary basin, and hence, the gravity profiles are interpreted using variable density contrast with depth. From the Bouguer gravity anomaly, the residual anomaly is constructed by graphical method correlating with well data and subsurface geology. The residual anomaly profiles are interpreted using polygon and prismatic models. The maximum depths to the granitic gneiss basement are obtained as 3.00 km. The regional anomaly is interpreted as Moho rise towards coast. The aeromagnetic anomaly profiles are also interpreted for charnockite basement below the granitic gneiss group of rocks using prismatic model.
Estimation of Dipping Angles of Refracting Interfacesiosrjce
IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) multidisciplinary peer-reviewed Journal with reputable academics and experts as board member. IOSR-JESTFT is designed for the prompt publication of peer-reviewed articles in all areas of subject. The journal articles will be accessed freely online.
Estimation of Poisson’s Ratio of Ozizza Subsurface Layersiosrjce
A geophysical survey aimed at determining the Poisson’s ratio of subsurface earth materials have
been carried out. Knowledge of the Poisson’s ratio of materials is important since it gives information about the
quality of such materials with respect to construction works. The study area is Ozizza (lat. 5.80
-5.90N; long.
7.80
-7.90E) situated within the Afikpo sedimentary basin in south - eastern Nigeria. The geophysical method
employed was the seismic refraction method and both P - and S - waves were utilized. The major equipment
used was a MOD.S79 seismograph and its accessories including P- and S- wave sources and detectors. The
result shows that the P- waves delineated three layers with average velocities of 420m/s, 1745m/s and 2620m/s
for the first, second and third layers from the earth’s surface respectively whereas the S-waves revealed only
two layers with average velocities of 310 m/s and 1100 m/s for the first and second layers accordingly. The
result indicates that the first and second layers of Ozizza (probably made up of sandy clay and sand with gravel
have Poisson’s ratio of 0.22 and 0.28 respectively.
Quantum Current in Graphene Nano Scrolls Based Transistortheijes
Graphene based material application as a new centuery material are growing rappidly its carrier transport phenomenon with fast mobility have been focused resently. In the graphene family nanoscrolls because of their especial structure need to be explored. In the presented work a theoretical model for carrier transport in the arcemedus graphene nanoscrolls is reported. Graphene nanoscroll chairal dependent electrical property is considered and then schottky transistor based platform is modeled. The transport coeficient as a fundamental transport factor is discussed. The geometrical paprameter effect on the working phenomenon is considered as well.
Detection of Low-Speed Layer (Lvl) In Seismic Refraction Survey Using Combine...iosrjce
A combination of two geophysical methods not only helps to enhance the accuracy of results but also
helps to detect the presence of a low velocity layer which cannot be detected by refraction shooting alone. The
Direct Current resistivity method was combined with the seismic refraction method to infer the lithology of
Nnodo (Latitude 6.300
- 6.320N and Longitude 8.100
- 8.120E), Nigeria, during which a low-velocity layer was
encountered. The major instruments used were the signal enhancement seismograph and the ABEM terrameter.
The seismic refraction method revealed three layers of the earth from its surface with velocities 300m/s,
1200m/s and 2100m/s which were interpreted as dry/loose sand, saturated sand and limestone respectively. The
resistivity method however, revealed five geoelectric layers with resistivity values 957 Ωm,363 Ωm,1033
Ωm,489 Ωm and 135 Ωm which were interpreted as dry soil, saturated sand, sandy clay, limestone and shale
respectively. A comparison of the two results showed that the third layer from the surface at Nnodo interpreted
as probably sandy clay( from the resistivity survey) was not detected in the seismic refraction survey. This was
suspected to be a low-velocity layer with a velocity of about 600m/s. Hence the layer of limestone according to
the seismic result is the fourth layer of the study area and not the third.The actual lithology of the third layer
which the seismic refraction method could not detect is sandy clay. This was evident from the resistivity result.
The lithologic sequence of the study area from the earth’s surface is therefore dry soil, saturated sand, sandy
clay, limestone and fractured shale(wet).
Delineating faults using multi-trace seismic attributes: Example from offshor...iosrjce
Techniques for delineating faults have been applied to a 3D seismic data acquired over parts of
offshore Niger Delta. The volumetric dip and azimuth of the seismic traces was first computed directly from the
seismic reflection data. Noise cancellation techniques were then applied to the data to highlight overall
structural dip trend. An attribute that highlight seismic discontinuities based on trace-trace similarity was then
computed over a user-defined window using the seismic reflectivity and smoothened dip data as input. The dip
and similarity volumes reveal a structural framework consisting of a major NE-SW trending lineament
separating two zones of contrasting structural styles. In the northern part of the lineament, deformation is
compressional, with NNE-SSW to N-S trending thrusts and folds. In the south, deformation is characterized by a
network of predominantly NW-SE trending extensional faults. Although the structural trend is clearly evident in
the computed dip volumes, estimating multi-trace similarity along structural dips has significantly improved the
ability to recognize faults in the data
International Journal of Mathematics and Statistics Invention (IJMSI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJMSI publishes research articles and reviews within the whole field Mathematics and Statistics, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
In this study the kinematic wave equation has been solved numerically using the modified Lax
explicit finite difference scheme (MLEFDS) and used for flood routing in a wide prismatic channel and a nonprismatic
channel. Two flood waves, one sinusoidal wave and one exponential wave, have been imposed at the
upstream boundary of the channel in which the flow is initially uniform. Six different schemes have been
introduced and used to compute the routing parameter, the wave celerity c. Two of these schemes are based on
constant depth and use constant celerity throughout the computation process. The rest of the schemes are based
on local depths and give celerity dependent on time and space. The effects of the routing parameter c on the
travel time of flood wave, the subsidence of the flood peak and the conservation flood flow volume have been
studied. The results seem to indicate that there is a minimal loss/gain of flow volume whatever the scheme is.
While it is confirmed that neither of the schemes is 100% volume conservative, it is found that the scheme
Kinematic Wave Model-2 (KWM-II) gives the most accurate result giving only 0.1% error in perspective of
volume conservation. The results obtained in this study are in good qualitative agreement with those obtained in
other similar studies.
An Examination of Effectuation Dimension as Financing Practice of Small and M...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Does Goods and Services Tax (GST) Leads to Indian Economic Development?iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Childhood Factors that influence success in later lifeiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Emotional Intelligence and Work Performance Relationship: A Study on Sales Pe...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Customer’s Acceptance of Internet Banking in Dubaiiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
A Study of Employee Satisfaction relating to Job Security & Working Hours amo...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Consumer Perspectives on Brand Preference: A Choice Based Model Approachiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Student`S Approach towards Social Network Sitesiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Broadcast Management in Nigeria: The systems approach as an imperativeiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
A Study on Retailer’s Perception on Soya Products with Special Reference to T...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
A Study Factors Influence on Organisation Citizenship Behaviour in Corporate ...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Consumers’ Behaviour on Sony Xperia: A Case Study on Bangladeshiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Design of a Balanced Scorecard on Nonprofit Organizations (Study on Yayasan P...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Public Sector Reforms and Outsourcing Services in Nigeria: An Empirical Evalu...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Media Innovations and its Impact on Brand awareness & Considerationiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Customer experience in supermarkets and hypermarkets – A comparative studyiosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Social Media and Small Businesses: A Combinational Strategic Approach under t...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Secretarial Performance and the Gender Question (A Study of Selected Tertiary...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Implementation of Quality Management principles at Zimbabwe Open University (...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Organizational Conflicts Management In Selected Organizaions In Lagos State, ...iosrjce
IOSR Journal of Business and Management (IOSR-JBM) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of business and managemant and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications inbusiness and management. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Measurement of Velocity Gradients of Beds At Unwana, Nigeria
1. IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE)
e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 6 Ver. IV (Nov. - Dec. 2015), PP 57-60
www.iosrjournals.org
DOI: 10.9790/1684-12645760 www.iosrjournals.org 57 | Page
Measurement of Velocity Gradients of Beds At Unwana, Nigeria
S. O.
AGHA1
, R.C. UWA1
and J.E.EKPE1
1. Department of Industrial Physics, Ebonyi State University, Abakaliki.
Abstract: Seismic compressional waves have been used in Unwana to measure velocity gradients of beds. The
seismic refraction method was employed. Unwana is situated within latitude 50
50'
to 50
55'
N and longitude 70
50'
to 70
57'
E. It has an area of about 48km2
. A digital type signal enhancement seismograph was the equipment
used along with its accessories. Forward and reverse shootings were carried out along the same profile line and
the seismic velocities and thicknesses of underlying layers were estimated. The velocity gradients of the
refracting beds were hence evaluated. The primary wave velocities for both forward and reverse shots were
found to be 315m/s and 300m/s respectively for the first layer and 608 and 600m/s respectively for the second
layer. The thickness measured from both forward and reverse ends of the profile line were 2.1m and 2.0m
respectively for the first layer and 7.3m and 4.7m respectively for the second layer. These gave values of
velocity gradients as 149s-1
and 150s-1
respectively for layer 1 and 83s-1
and 127s-1
respectively for the second
layer. The result indicates that the materials of the first layer in Unwana are laterally homogenous and are flat-
laying while those of the second layer are dipping although with no lateral inhomogeneity.
Keywords: Refraction, compressional, seismic, seismograph.
I. Introduction
The seismic refraction method can be used for very many purposes. These include determination of
groundwater potential of an area, deduction of rock lithology and estimation of thickness and velocity values of
rock layers.
This work shows how the method can be used to deduce velocity gradient.
Velocity gradient is hereby defined as the ratio of seismic wave velocity of a substratum to its
thickness. Because the refracting interface is in most cases not horizontal, the assumption of flat layers then
leads to errors in velocity and depth computations. When an interface is presumed to be dipping, the velocities
of the layers and the dip of the interface can be obtained by shooting a second complementary profile in the
opposite direction. (Lowrie, 1997).
As an illustration, consider two impact points A and B along a profile line, AB. The two shot points are
located at the end of a geophone array that covers AB with A as the shot point for the forward profile and B for
the reverse profile.
DC is the refractor, V1 and V2 are the velocities in the upper and lower medium respectively. HA is the layer
thickness measured from point A while HB is the layer thickness measured from point B and 𝜃 is the dip angle
of the interface (fig. I). Obviously, HA > HB. When an impact is made at A, the seismic ray ADCB from point A
impinges on the refractor at point D and travels parallel to the boundary along the up-dip direction to point C as
a head wave before entering a receiver at B. In the reverse profiling the ray BCDA from impact point B travels
along the boundary in the down-dip sense to point A through points C and D accordingly. The travel time versus
offset graphs i.e. t-x curves (Fig.. 2) would not, be the same for the forward and reverse profiling but the total
travel-time must be equal (Kearey and Brooks, 1991).
D
HB
Ө
B
NV1
M
A
HA C
V2
Fig.1: Schematic Diagram of a Dipping Bed
2. Measurement Of Velocity Gradients Of Beds At Unwana, Nigeria
DOI: 10.9790/1684-12645760 www.iosrjournals.org 58 | Page
From the T-X curves, true velocities V1 and V2 of the first and second layers of the subsurface can be obtained
as follows.
𝑉1 =
𝑉𝐼𝐹 + 𝑉𝐼𝑅
2 … … … … … … … … … … . (1)
𝑉2 =
2 cos 𝜃
1
𝑉2𝐹
+
1
𝑉2𝑅
… … … … … … … … … … … … . . …. (2)
where F and R represent forward and reverse profiles respectively and 𝜃 is the dip angle. VIF and VIR
are calculated from the reciprocal slopes, M of the curves. The dip angle 𝜃 and the critical angle, ic are
determined from V1,VIF, and V1R respectively as follows:
𝜃 =
1
2
𝑆𝑖𝑛−1
𝑉1
𝑉1𝐹
+ 𝑠𝑖𝑛−1
𝑉1
𝑉1𝑅
… … … … … … … . . (3)
𝑖 𝐶 =
1
2
𝑆𝑖𝑛−1
𝑉1
𝑉1𝐹
− 𝑠𝑖𝑛−1
𝑉1
𝑉1𝑅
… … … … … … … . . (4)
With the knowledge of the dip angle, 𝜃 the true velocity, V2 is calculated as shown in equation (2) above
(Okwueze, 1988).
Apparent velocities V2F and V2R are obtained from the relations:
1
𝑉2𝐹
=
1
𝑉1
𝑆𝑖𝑛 𝑖 𝑐 + 𝜃 … … … … … … … … … … … . . (5)
1
𝑉2𝑅
=
1
𝑉1
𝑆𝑖𝑛 𝑖 𝑐 − 𝜃 … … … … … … … … … … … . . (6)
The velocity gradient (V/h) at each of the short points for a given layer thickness, h are evaluated using the
values of V1F, V1R, V2F and V2R, etc. This work involves the use of the seismic refraction method to estimate the
velocity gradient at Unwana, Nigeria. Unwana is situated within latitude 50
50'
to 50
55'
N and longitude 70
50'
to
70
55'
E
II. Materials And Method
As in all seismic refraction surveys involving shallow investigations, the materials needed included a
seismograph, sets of geophones, and source of signal. In this particular work, the seismograph was a signal
enhancement type. The geophones were electromagnetic type with frequency 10Hz. The signal was
compressional waves generated mechanically, as a result, only P-wave geophones were arrayed. Single line
𝑀1𝑅 =
1
𝑉1𝑅
TRTF
𝑀2𝑅 =
1
𝑉2𝑅
𝑀𝐼𝐹 =
1
𝑉𝐼𝐹
𝑀2𝐹 =
1
𝑉2𝐹
Distance (x)
Figure 2: T-X curves for forward and reverse
profiles.
3. Measurement Of Velocity Gradients Of Beds At Unwana, Nigeria
DOI: 10.9790/1684-12645760 www.iosrjournals.org 59 | Page
profiling method of seismic refraction survey was adopted. About 12 geophones were interconnected in series
with the shot point and the inter-geophone spacing was 5m. After the initial shooting (forward shooting), the
shot point was moved to the rear of the geophone array for the reverse shot. The shot-detector spacing at both
extremes of the array was also 5m.
III. Result And Discussion
Fig. 4 shows the T-X graph of P-wave data obtained at the study area.
Table 1 shows the velocity gradient (V/h) measured from each end of the shot points for the various layers
delineated by the wave in the study area
Table 1: Velocity (V), thickness (h), and velocity gradient (V/h) obtained in the study area
LAYER FORWARD SHOT REVERSE SHOT
V(m/s) h(m) V/h(s-1
) V(m/s) h(m) V/h(s-1
)
1 314 2.1 140.05 300 2.0 150
2 608 7.3 83.02 600 4.7 127
3 1714 - 1867
IV. Discussion
The T-X graph reveal three geoseismic layers with velocities 314m/s, 608m/s and 1714m/s for layers
1,2 and 3 respectively for the forward shot and velocities 300m/s, 600m/s and 1867m/s for layers 1,2,3
respectively for the reverse shot. These velocities as well as the layer thicknesses, measured from each end of
the profile and the evaluated velocity gradient, are shown in Table I.
Looking at the result, it is seen from Table I that the velocity values for forward and reverse shots which are
314m/s and 300m/s for layer 1 are nearly the same. Their thicknesses also are approximately equal - 2.1m from
the forward shot point and 2.0m from the reverse shot point. The velocity gradients measured are therefore
equal.
However for the second layer, although the seismic velocities measured from both ends of the shot
point are nearly the same (608m/s and 600m/s for forward and reverse shots respectively), the thicknesses at
both ends differ markedly – 7.3m and 4.7m respectively. For this reason, the velocity gradients at both ends of
the shot vary widely – 83.02s-1
and 127s-1
for the forward and reverse ends respectively.
V. Conclusion
The fact that the thickness values of both forward and reverse shots for the first layer are approximately
the same indicates that the interface has negligible dip. The refractor is therefore flat-laying. Again because the
seismic velocities measured from both ends of the profile line are nearly equal implies that lateral differences in
composition of materials are negligible. Thus the materials of the first layer are homogenous and are interpreted
Distance, x (m)
Time,T
(ms)
0 5 10 15 20 25 30 35 40 45
300m/s
588m/s
600m/s
1714m/s1867m/s
313m/s
4. Measurement Of Velocity Gradients Of Beds At Unwana, Nigeria
DOI: 10.9790/1684-12645760 www.iosrjournals.org 60 | Page
to be probably sandy clay. To confirm the absence of dip in the first layer and the homogeneity of materials
there, the velocity gradient has the same value at both ends of the profile line.
However the result for the second layer indicates the presence of dip given the wide variation in thickness at
both ends of the profile line. The material composition nevertheless seems to be uniform throughout the layer as
the seismic velocities are nearly the same at both ends of the profile line. Thus, because of the variation in
thickness, the velocity gradient estimated at both ends of the profile varies widely. The second refractor
therefore is dipping.
References
[1]. Agha, S.O., and Arua, A.I. (2014). Integrated Geophysical Investigation of Sequence of Deposition of Sedimentary Strata in
Abakaliki. European Journal of Physical and Agricultural Sciences. 1(5), 1 – 5.
[2]. Agha, S.O., Okwueze, E.E., and Akpan, T. (2006). Determination of Strength of Foundation Materials in Afikpo, Nigeria, Using
Seismic Refraction Method. Nigerian Journal of Physics. 18(1), 33-37
[3]. Dobrin, M.B. (1976). Introduction to Geophysical Prospecting. McGraw-Hill Book Company Ltd. Japan.
[4]. Kearey, P., and Brooks, M. (1991). An Introduction to Geophysical Exploration(2nd
ed.). Blackwell Scientific Publications,
Cambridge, U.S.A.
[5]. Lowrie, W. (1997). Fundamentals of Geophysics (3rd
Edition). Cambridge University Press, New York.