P. Schmoldt, PhD - MTNet - DIAS

7. Geology of the Iberian Peninsula
Station Moho depth (km)
NE17 32.0 ±2.5
PAB 31.0 ±1.0
NE13 30.0 ±1.0
Tab. 7.3.: Depth of the Moho derived from Receiver Function analysis by Julià and Mejía [2004] for three stations on top of the
Iberian Massif to the west of the Tajo Basin (see Figure 7.25 for station locations).
and
velocity reduction(films) < velocity reduction(tubes) < velocity reduction(spheres)
[Mavko, 1980]. Goes et al. [2000] further argue that changes of composition and magnesium
number (Mg#) have no significant direct effect on seismic velocity, but rather
through related density changes; see also Jones et al. [2009] for details on this aspect.
The actual effect of Mg# change is dependent on the local mineral composition, e.g. compressional
velocity increases with increasing Mg# for olivine [Chen et al., 1996; James
et al., 2004] and decreases for spinel and garnet peridotites [Kopylova et al., 2004]. However,
the observed low velocity region may be due to a combination of the above-described
parameters, wherein temperature is commonly assumed to account for the bulk of the velocity
variation. More light on this aspect will be shed by results of the PICASSO Phase I
investigation, providing additional information about the present material distribution and
their condition in terms of electric conductivity.
Receiver Function
Receiver Function studies, the seismic method generally most capable of detecting the
LAB, have been carried out in Spain by Julià et al. [1998] and Julià and Mejía [2004].
The authors use data from stations installed in the area of Ebro Basin, Betic Cordillera,
and in the SW of the Iberian Peninsula of which four stations are located in proximity
of the PICASSO Phase I profile (Fig. 7.25). Three of those stations are installed in
the region of the southeastern Iberian Massif, whereas the forth station is located in the
Betic Cordillera, all within approximately 1 degree to the west of the PICASSO Phase I
profile. For the Tajo Basin the authors derive a Moho depth of around 31 km, slightly
deepening towards the north (see Tab. 7.3 for details), using direct P teleseismic wave
reverberation [Julià et al., 1998] and P-to-S converted waves (also referred to as P-wave
receiver function (PRF)) [Julià and Mejía, 2004]. No details about deeper-seated features
like the LAB are presented by Julià et al. [1998] or Julià and Mejía [2004], owing to
the lack of sufficient data. The lack of good quality data is due to the masking effect of
P-wave reverberations on PRF data and the general difficulty to obtain S-to-P converted
waves (also referred to as S-wave receiver function (SRF)).
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