Abstract
Two passive seismic experiments have been carried out across the Trans
European Suture Zone (TESZ) from northern Germany to southern Sweden
(TOR) and across the Proterozoic-Archaean suture in Finland (SVEKALAPKO)
to improve our understanding of the processes involved in the creation
of the European continent. Teleseismic earthquakes recorded by the
two networks and stations of the GRSN and GEOFON permanent networks
have been used for studies of the crust-mantle, and upper mantle
seismic discontinuities with the receiver function method. Along
the TOR network the depth to the Moho increases from 30 km at the
southern edge of the profile to 40 km at the Elbe Line. Between the
Elbe Line and TESZ the Moho branches off and whereas the deeper branch
continues at 40 km depth to the TESZ a second branch appears at 30-35
km depth. The upper branch descends north of the TESZ to below 55
km under the northern end of the TOR profile. The crustal thickening
north of the TESZ is accompanied by an increase in average Vp/Vs
values, appearance of intracrustal conversion zones and north dipping
features which we interpret as remnants of the subduction and subsequent
collision between Avalonia and Baltica. In southern Finland beneath
the SVEKALAPKO network the Moho starts in the south at the depth
of 40-45 km, plunges to about 65 km depth south of the Archaean-Proterozoic
suture. This deepening of the Moho is coincident with a north dipping
intracrustal structure apparently related to the subduction and collision
and of the Proterozoic and Archaean provinces in Proterozoic. North
of the line of the suture the Moho rises smoothly to 45-50 km depth
in the Archaean province. Along the TOR profile, 410 and 660 discontinuities
were hard to detect. However, manyfold stacking of receiver functions
revealed that the conversions from the two discontinuities arrive
more or less according to IASP91 predicted time. Across the SVEKALAPKO
network 410 and 660 discontinuities arrive markedly earlier than
IASP91 theoretical arrival times. In particular north of the Archaean-Proterozoic
suture in Finland the 410 and 660 km conversions arrive about 2 s
earlier, indicating about 5 per cent higher average upper mantle
velocities and lower temperatures than what IASP91 global model predicts.
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