Seismic wavelets and resolution - Seismic Amplitude - page 26

Time-shifted
zero-phase
wavelet

Decomposed into single
frequency components

Plot of phase
against frequency

Phase

0

Time zero

Time shift

-180

-360

Frequency

Time Time

Figure 3.4 Linear phase wavelet; illustrating that this phase behaviour is effectively associated with a time shift (J. Chamberlain, personal

communication)

a) b)

Source Signature

18db/oct low-cut 18+24 db/oct low-cut

0 0

50 50

100 100

Frequency

150 150

Reflection
Refraction
Transmission
Attenuation

Earth Filter

10 0

a: blue
b: red 10 -1

10 -2

Amplitude spectra

0 50 100

Frequency Hz

Figure 3.6 Two minimum phase wavelets with similar bandwidth
but slightly different low-cut responses (after Simm and White 2002 ) .
Note the marked differences in wavelet shape.

Frequency

tie is lower in frequency and roughly symmetrical with a
phase of around 180°.
These effects are controlled by attenuation, which
varies with the lithology and state of consolidation.

Seismic Trace
Figure 3.5 Seismic bandwidth and the Earth filter.

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