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Introduction to Geophysics
Department of Earth SciencesKFUPM
Refraction Interpretation-2
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oduc
tion
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Previous Lecture
Refraction Seismology ObjectiveInterpretation ModelsQuiz
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FUPM Interpretation Models
Figure 4.3 of Lillie
Single Horizontal Interface in kmIn
trod
ucti
on t
o Ge
ophy
sics
-KFU
PM
Fig. 4.4 of Lillie
t1 Delayed Time
100-150km <Spread Length< 300-600km
Oceans Continental1
1
2
Vc
Cosht
θ=
CCosh
Vtθ211=
Inversion equations
12
2112 VV
VVhxcr −
+=
Forward equations
Intr
oduc
tion
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Geop
hysi
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FUPM Single Horizontal Interface in meter
Fig. 4.5 of Lillie
11
2
Vc
Cosht
θ=
CCosh
Vtθ211=
Inversion equations
12
2112 VV
VVhxcr −
+=
Forward equations
Intr
oduc
tion
to
Geop
hysi
cs-K
FUPM Several Horizontal Interfaces
Generalized Refraction ModelIn
trod
ucti
on t
o Ge
ophy
sics
-KFU
PM
111
,2
Vni
Cosht
in
in
θ∑
=− =
Fig. 4.7 of Lillie
The above model is valid as long as velocity does not decreased with depth.
Refraction: Example from Ocean Basin
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Fig. 4.8 of Lillie, modified after Sheriff and Geldart, 1995.
Refraction: Oceanic Crust
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Where do you know about the well-known examples of Oceanic Crust?
Layer 1: Deep-sea sedimentsLayer 2: Basalt (Volcanics and shallow intrusions)Layer 3: Gabbro (Deeper Intrusions)Layer 4: Peridodite (Uppermost refraction; gives Moho refraction)
Mid
-Atla
ntic
R
idge
Eas
t P
acif
ic
Ris
e
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oduc
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Parks and Plates©2005 Robert J. Lillie
Formation of Oceanic CrustIn
trod
ucti
on t
o Ge
ophy
sics
-KFU
PM
Parks and Plates©2005 Robert J. Lillie
Formation of Oceanic CrustIn
trod
ucti
on t
o Ge
ophy
sics
-KFU
PM
Parks and Plates©2005 Robert J. Lillie
Intr
oduc
tion
to
Geop
hysi
cs-K
FUPM Formation of Oceanic Crust
Parks and Plates©2005 Robert J. Lillie
Intr
oduc
tion
to
Geop
hysi
cs-K
FUPM Formation of Oceanic Crust
Parks and Plates©2005 Robert J. Lillie
Intr
oduc
tion
to
Geop
hysi
cs-K
FUPM Formation of Oceanic Crust
Parks and Plates©2005 Robert J. Lillie
Parks and Plates©2005 Robert J. Lillie
Field Trip: KFUPM BEACH
Schedule: March 29 (or 27?) before Mid-Term Break
Leaving from: 12:30 from KFUPM
The purpose: Measurements of Refraction and Gravity
Any questions or suggestions.
