HR: 12:05h
AN: G12A-08    [Abstracts]
TI: Rigid Block Motion, Interseismic Strain, and Backarc Deformation in the Aegean
AU: * Apel, E V
EM: apel@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall University of California, Berkeley, Berkeley, CA 94720-4767, United States
AU: Bürgmann, R
EM: burgmann@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall University of California, Berkeley, Berkeley, CA 94720-4767, United States
AU: Serpelloni, E
EM: enricos@bo.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Centro Nazionale, Via Donato Creti 12, Bologna, 40128, Italy
AB: We combine available GPS data in and around the Aegean region to model plate boundary deformation and earthquake cycle effects in the observed velocity field. Typically, GPS data in the region have been used as evidence that a southern Aegean micro-plate behaves coherently and rigidly. These first-order models match the observed data quite well suggesting little intra-plate or plate-boundary deformation. However, the M >8 Crete earthquake of AD 365 and some other historic earthquakes may have occurred along the Hellenic subduction zone, which implies that a substantial portion of the subduction thrust may be locked. Depending on the locking required to generate earthquakes of this magnitude, a measureable elastic strain signal reaching far into the overriding plate should be evident in the surface velocity field. Alternatively, slow accumulation of elastic strain and dominantly aseismic creep on the subduction thrust may generate very little deformation across the southern Aegean plate. It is also possible that the surface velocities generated by convergence at a locked subduction zone are masked by simultaneous back-arc extension, creating the illusion of rigid plate motion. We consider a range of possibilities in an attempt to interpret the current geodetic signal in the region and its implications for earthquake hazard assessment. We use a block modeling approach that considers both rigid rotations and elastic strain fields along block boundaries to examine the possible trade-off between these components. As many of the stations are located away from the plate boundaries in question it is difficult to constrain boundary parameters, such as locking depth and dip, using only the GPS data. We generate multiple models to explore the solution space of all reasonable parameters. Our modeling suggests that it is possible for coeval extension (back-arc) and convergence (subduction) to occur masquerading as rigid motion. Eventually, precisely determined vertical motions of GPS stations above the Hellenic subduction zone are needed to resolve this important question.
DE: 1209 Tectonic deformation (6924)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8150 Plate boundary: general (3040)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2007 Fall Meeting