SEISMIC ATTENUATION
Ray paths from Vrancea zone
earthquakes to four stations on two
portions of the stable East European
Platform, color coded according to
the Qs estimates for the event-station
pairs. Paths to EEP stations are
consistently low attenuation (high
Qs), consistent with the cratonic
nature of the EEP, both the
Moldavian portion north of the
Trotus Fault, and the Schythian
Platform portion to the south.
Red
Q<200
300<Q<350 Cyan
Orange 200<Q< 250
350<Q<500 Blue
Yellow 250<Q< 300 White = complete S wave blocking Green
500<Q
SEISMIC ATTENUATION
Ray paths from Vrancea zone
earthquakes to five stations in the
Vrancea zone region, the Carpathian
chains or the Transylvanian basin, color
coded according to the Qs estimates for
the event-station pairs. Note that paths
to these stations are consistently high
attenuation (low Qs), and note
particularly the high frequency of S
wave blockage to the stations in the
Southern Carpathians and Transylvanian
basin. These stations are closest to the
most recent volcanic activity in the
Carpathian region. High attenuation at
these stations confirms the long-term
belief, on the basis of surface geology,
that the inner Carpathian region is a
back-arc.
Red
Q<200
300<Q<350 Cyan
Orange 200<Q< 250
350<Q<500 Blue
Yellow 250<Q< 300 White = complete S wave blocking Green
500<Q
SEISMIC ATTENUATION
ULTIMATE GOAL:
to map the distribution of lithosphere and
asthenosphere in Vrancea
PRELIMINARY RESULTS: provide a strong
indication that it will be possible to meet this goal
SEISMIC ATTENUATION
SEISMIC ATTENUATION
SEISMIC ATTENUATION
Color-coded ray paths to three stations shown in the previous slide projected onto
NW-SE cross section. Tectonic units (adapted) assuming a delamination horizon (heavy
black-white dashed line) at 70 km, consistent with mantle xenolith composition in
Persani basalts.
High-Q paths to LUC and GRE cross presumably low-attenuation continental mantle
lithosphere and crust. Not all the low Qs rays to station OZU can be explained by this
model, since many do not travel through highly attenuating asthenosphere. Either
attenuation occurs at shallow depths beneath OZU, or the model should be modified.
SEISMIC ATTENUATION
One possible modification to delamination model that would make it consistent with our
results: raise the delamination horizon (heavy black-white dashed line) to a shallower
depth so low-Q paths to OZU cross a significant thickness of asthenosphere.
DISTRIBUTION OF
LITHOSPHERE AND ASTENOSPHERE
Attenuation is low (high Qs) at stations east and north of the Vrancea zone on the East
European platform, the Scythian Platform, and in the easternmost portion of the
Moesian Platform. Inconsistent results at stations west of the Intramoesian fault,
including those in and around Bucharest, probably reflects strong site effects in
several locales. Attenuation at stations above and near the Vrancea zone, and at
stations in the Transylvanian Basin is high (low Qs), most likely due to the presence of
hot asthenosphere in these areas.
GPS
GPS
Horizontal Velocity Estimates
GPS
Vertical Velocity Estimates
NATO campaigns included
excluded
mm/yr
To early to draw any conclusions, more data necessary!
GPS
Conclusions
• Horizontal crustal motions as measured by GPS clearly
give indications for active faults and tectonic structures in
the area
• Vertical motions as measured by GPS currently are
influenced by yet unexplained artefacts, and as such are
not accurate enough for interpretation; further
measurements will be necessary
GPS
OVERALL CONCLUSIONS
Major variations of the lithosphere’s structure led to
• strength decrease
• localization of strain in adjacent basins
Pannonian Basin = hottest -> weakest basin in continental Europe
Significant Q movements =>
• seismic hazards
• landscape and slope instability
• rapid evolution of drainage systems
Cloetingh et al., 2005
ONTONG-JAVA
AEGEAN
KAMCHATKA
INDOCHINA
PERU-CHILE