HR: 08:20h
AN: T51A-02    [PDF]
TI: Seismic Versus Aseismic Deformation in Iran Inferred from GPS and Seismicity Data
AU: * Masson, F
EM: fmasson@dstu.univ-montp2.fr
AF: LDL -UMR CNRS 5573, Universite Montpellier, Pl. E. Bataillon, Montpellier, 34095 France
AU: Chery, J
AF: LDL -UMR CNRS 5573, Universite Montpellier, Pl. E. Bataillon, Montpellier, 34095 France
AU: Martinod, J
AF: LMTG - UMR CNRS 5563, Universite Paul Sabatier, 38, rue des 36-Ponts, Toulouse, 31400 France
AU: Hatzfeld, D
AF: LGIT - UMR CNRS 5559, Universite Joseph Fourrier, BP 53, Grenoble, 38041 France
AU: Vernant, P
AF: LDL -UMR CNRS 5573, Universite Montpellier, Pl. E. Bataillon, Montpellier, 34095 France
AU: Tavakoli, F
AF: Geodynamic Department, National Cartographic Center, Po. BOX 13185-1684, Meraj Ave, Tehran, 19531 Iran (Islamic Republic of)
AU: Ashtiany, M
AF: International Institute of Earthquake Engineering and Seismology, Farmanieh, Dibaji, Arghavan St., Nø 27, Tehran, 19531 Iran (Islamic Republic of)
AB: The present tectonic of Iran results from the north-south convergence between the undeformed shield areas of Arabia to the south-west and Eurasia to the north-east. A GPS network of 28 benchmarks has been surveyed in September 1999 and October 2001. Our GPS velocity field defines a quantitative strain pattern of the Arabia-Eurasia collision. It allows to answer three major questions which can be addressed quantifying the present-day Iranian tectonics. a) How is quantitatively distributed the deformation within this juvenile continental collision between different active structures (Zagros, Alborz, Caucasus) ? b) How is accommodated the transition from a continental collision in Zagros to an oceanic subduction in Makran ? c) Is the deformation accommodated seismically or aseismically ? This presentation will focus on this third question. The combined analysis of the geodetic strain rate field and the strain rate field deduced from the seismicity allows to characterise the style of deformation and specially to precise the part of the seismic deformation relatively to the aseismic one. Geodetic measurements record complete deformation (seismic and aseismic) while earthquakes provide information about the seismic deformation. Iran is one of the best place to study the seismic/aseismic deformation ratio because it is a very large deformed area (~ 1500 x 1500 km2), covered by a geodetic network and characterised by a dense and well known historical seismicity. Comparison of seismic and geodetic strain rates indicates that highly strained zones experience mainly aseismic deformation in southern Iran and seismic deformation in northern Iran. This correlate with large earthquakes distribution. Indeed, a dense, low intensity seismicity is observed in the Zagros whereas the largest earthquakes occur in northern Iran. Jointly used, earthquake data and geodetic strain may be of valuable help in order to define the earthquake potential in highly populated areas of northern Iran.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1242 Seismic deformations (7205)
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting