module 6

Question 1

Simple Convolution Model

Answer 1

S(t) = Rc * w(t)

Question 2

Types of Noise

Answer 2

Random
Coherent (ground roll, direct, refractions, multiples, diffractions

Question 3

CDP stacking benefits

Answer 3

reduce S/N
multiple suppression
average velocities increase
normal move out decreases w depth
primaries are stacked "in-phase"
multiples are stacked "out of phase"

Question 4

Land sources

Answer 4

Dynamite
mechanical wave generator
vibroseis (upsweep, downsweep)
dinoseis
thumper
air guns
mini-sosie

Question 5

conventional field record

Answer 5

eg dynamite where you can see data

Question 6

why do multiple vibe trucks sweep simultaneously in source arrays

Answer 6

attenuate surface noise

improve S/N ratio

Question 7

marine sources

Answer 7

bubble pulse
maxipulse
flexotir
vaporchoc
starjet
airgun
water gun
sparkler

Question 8

what are the 3 source groups (Marine)

Answer 8

tuned —- set to cancel out bubble oscillations
single source units - recorded signature eliminates bubble pulse
single or multiple source arrays - deigned to NOT generate or to ATTENUATE bubble pulse oscillations

Question 9

Forerunner

Answer 9

a wavelet before a spike is FORERUNNER

Question 10

Oscillations

Answer 10

wavelet that trickles off at the end is OSCILLATIONS

Question 11

Preferred signature

Answer 11

spike

Question 12

How do geophones work ?

Answer 12

GEOPHONE

arrival of a p-wave
geophone case has a coil and it’s coupled to the ground
magnet is stationary and is suspended on springs
The coil moves within the magnetic field. It induces an electrical voltage
Voltage is recovered on tape in binary format
particle motion gephones record vertically vibrating P or P/Sv waves
Special geophones are used to record Sh

Question 13

What are the geophone components ?

Answer 13

output
coil
magnet
spoke

Question 14

How do hydrophones work ?

Answer 14

There is a piezoelectric transducer within the hydrophone. It measures pressure changes in the water. These are changes from seismic pressure waves from bubbles

Question 15

What is strumming?

Answer 15

vibration of the cable and sudden acceleration

Question 16

how do you reduce cable “strumming” ?

Answer 16

ship motion is decoupled using an elastic non=active lead-in
ensure streamers are at a constant depth

Question 17

What is telemetry?

Answer 17

automatic transmission and measurement of data by wire or radio.

Question 18

Shear wave generation

Answer 18

dynamiHorizontal S waves are generated by a source which is polarized in the X-axis and detected by a receiver in the same axis

Question 19

what are the 3 main types of shear-wave source?

Answer 19

dynamite laid out in rows
anchored horizontal vibrator
directionally alternating horizontal hammer blows against the base plate

Question 20

problems to overcome in data and acquisition of shear wave data?

Answer 20

time scale adjustment

frenquency spectra of s waves are lower and more narrow band than p-waves

Question 21

what are the recording equipment?

Answer 21

analog -> digital -> analog reconstruction

recording amplifier
logic unit
tape transport
camera unit

Question 22

what are the components of recording amplifier

Answer 22

pre-amplifier - amplify input signal
analog filters - 3
multiplexer - sample in sequence

Question 23

what are the components of logic unit

Answer 23

formatter
digital to analog converter
demultiplexer

Question 24

tell me about the camera unit ?

Answer 24

wiggle trace records

Question 25

tell me about tape transport ?

Answer 25

write data to magnetic tapes

Question 26

know the binary system

Answer 26

7 6 5 4 3 2 1 0

2 2 2 2 2 2 2 2