IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Oral Presentation 2269
Present-day horizontal and vertical tectonic motion of the Dinarides
region, Croatia, from GPS data and tide gauge data
Mr. Goran Buble
IAG
Richard A. Bennett, Sigrun Hreinsdttir, Gabriele Casale, Tomislav Baić, Eljko BačIć,
Marijan Marjanović
Despite considerable attention directed towards Circum-Adriatic tectonics in the recent years, the rate
and direction of Adria microplate motion and internal microplate fragmentation remain unresolved. We
analyze tide gauge data from the eastern Adriatic Sea in order to assess spatial variation in vertical
tectonics. Tide gauge data are available from eight sites in Italy, Slovenia, Croatia and Montenegro with
long time series (30-95 years). Correlation among tide gauge records indicates that the interannual
sealevel variations are common mode. We are thus able to mitigate bias in trend estimates associated
with interannual variations by common-mode filtering (Wdowinski et al., 1997; Davis et al., 1999). We
find relative vertical crustal rates (with respect to the geoid) along the coast that fluctuate between 0.7
mm/yr which may be indication of active tectonic processes. Preliminary vertical rates determined from
a sparse network of continuous GPS sites (with respect to reference ellipsoid) in the region are in
general agreement with the tide gauge results within uncertainties. We also analyzed campaign and
continuous GPS data collected along the eastern Adriatic coast in 1994-2005 to investigate the pattern
of horizontal deformation. We find that NE directed horizontal shortening across the Dinarides that
varies along the coast of Croatia, revealing apparent rotations that are not well resolved by the present
GPS data set, but which nevertheless provide new clues regarding the modern configuration and motion
of the Adria micoplate(s). Velocity estimates for Istria are compatible with previous models for Adria
microplate motion (Battaglia et al., 2004; Calais et al. 2003). Sites in Istria have a Northward motion as
expected but sites further south along the coast (latitude 44 to 45 degrees N) have a more westward
motion, up to 40 degrees off from expected North Adria poles. Motions of sites on the Island of
Palagruza, Croatia, outermost Dalmatian Island, and Matera, Italy, Puglia platform, respectively, differ
by less than 0.20.3 mm/yr in magnitude and 03 degrees azimuth, which implies that Palagruza and
Puglia lie on a common southern Adria microplate. We will also discuss a new project that will involve
addition of a number of new continuous GPS stations, additional GPS campaigns, and other
measurements.
Keywords: gps, tide gauge, dinarides