Annual Report 2000 - WIT

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176
random media according to the generalized O'Doherty-Anstey formalism of Shapiro
and Hubral (1999). The reciprocal quality factor in Fig. (2) is normalized 6 by .
Phase velocity
1.1
1.08
1-D
2-D
”S”
•S•
3-D
exp. Gauss
ªSª««
¦S¦
§S§
v/c_0
0
v/c
1.06
1.04
1.02
L/a=5
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1
­¬¬­®®¯¯ °S°
ŸSŸ
°S°±± ²²³³ ´´µµ S
žSž
S
šSš
›S›
—S— –S–
—S— –S–
S ˜S˜
˜S˜
œSœ
S
œSœ
›S› šSš
0.98
–1 0 1 2 3 4 5
Log(ka)
Figure 1: Phase velocity normalized by the background velocity + ø
as a function of ÿ {
for Gaussian and exponentially correlated random media in 1-D, 2-D and 3-D .
APPLICATION
Attenuation measurements at the KTB-site
Within the framework of the KTB (the German continental deep drilling project) a
new insight in the structure of the continental crust was obtained. The KTB-site is
located in Southeast Germany and consists of two super-deep boreholes. The rocks
are of crystalline type (for a thorough review of this project we refer to Harjes et al.
1997). Several techniques (including analysis of VSP-Data and lab measurements)
have been applied in order to estimate the attenuation (see also Pujol et al, 1998).
Figure (3) displays the measured values in the frequency range from 5 to 85Hz and
indicates the corresponding references and depth intervals. In summary, all
P4P
studies
show h surprisingly (h [ ä
low -values ). Note h that reported -values of
P$P
the
Lithosphere are of h
õ#õ P$P$P
the order (see e.g. Figure 5.2 in Sato and Fehler,
1998).