HR: 0800h
AN: G51B-0812    [Abstracts]
TI: Deformation Along the Western Hellenic Subduction Zone From Continuous GPS
AU: * Floyd, M A
EM: Michael.Floyd@earth.ox.ac.uk
AF: Centre for the Observation and Modelling of Earthquakes and Tectonics, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AU: Nocquet, J
EM: nocquet@geoazur.unice.fr
AF: CNRS, UMR 6526 Geosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AU: Billiris, H
EM: billiris@central.ntua.gr
AF: NTUA, Faculty of Rural and Surveying Engineering, Department of Topography, 9 Heroon Polytechniou St., Zographos, Athens, 15773 Greece
AU: Paradissis, D
EM: dempar@central.ntua.gr
AF: NTUA, Faculty of Rural and Surveying Engineering, Department of Topography, 9 Heroon Polytechniou St., Zographos, Athens, 15773 Greece
AU: England, P
EM: Philip.England@earth.ox.ac.uk
AF: Centre for the Observation and Modelling of Earthquakes and Tectonics, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AU: Parsons, B
EM: Barry.Parsons@earth.ox.ac.uk
AF: Centre for the Observation and Modelling of Earthquakes and Tectonics, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AB: In respect of the great Sumatra-Andaman earthquake and subsequent tsunami of 26 December 2004, the study of coupling at subduction zones is imperative to understanding the seismic---or otherwise---hazard posed to a region. The Mediterranean Sea includes the Hellenic subduction zone, which accommodates the ~35 mm/yr of convergence between the oceanic lithosphere of the African plate and the extending continental lithosphere of the Aegean region. How the convergence is accommodated through earthquakes here remains controversial. For example, Jackson & McKenzie [1988] concluded that earthquakes can account for ~10% of the relative motion, implying that the subduction zone is in a stable-sliding state. On the contrary, Pirazzoli et al. [1982], using the Holocene geological record, inferred that large earthquakes (M>8) have occurred along the arc. In the last years, the development of permanent GPS networks near subduction zones has provided new information on the mechanisms of strain accumulation and release along the plate interface, highlighting the existence of transient slow slip events that may account for a significant part of convergence. We present results from a permanent network, in operation since early 2003, covering the western Hellenic Arc. Initial results indicate that no deformation perpendicular to the trench can be detected, supporting the hypothesis that the trench is currently in a stable-sliding state. Comparisons to 1992--2000 campaign data (McClusky et al. [2000]) indicate similar results. However, significant (~1m) extension is found in a comparison between historic triangulation and recent campaign GPS studies (Davies, et al. [1997]), averaged over 100 years, yet no significant earthquake can be invoked to explain such a large trench-perpendicular extension of the overriding plate. The existence of transient slip events elsewhere, however, presents a potential explanation for this discrepency in that the subduction zone does undergo strain accumulation and release cycles, but with a signal that, thus far, has been undetectable by intermittent studies in the region.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1209 Tectonic deformation (6924)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Geodesy [G]
MN: Fall Meeting 2005