Notes: We present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active Aegean region. We focus first on the 130 km long Corinth Rift, an asymmetric graben where a flight of terraces of marine origin are uplifted. We show that the edges of the terraces lie in the footwall of the normal fault bounding the Corinth Rift and correspond to sea-level highstands of laic Pleistocene age. Using a detailed analysis of aerial and SPOT imagery supported by field observations, we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault. The elevation of the terraces' inner edges was estimated at 172 sites with an error of ±5m. This data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level. To date the deformation, we correlate the Corinth terraces with late Pleistocene oxygen-isotope stages of high sea-level stands and with global sea-level fluctuations. Using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary-element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault. We show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000. All the terraces are fitted for fault slip increasing in proportion to terrace age, and the component of regional uplift is found to be less than 0.3 mm yr−1. The best fits give a slip rate of 11±3 mm yr−1 on the main rift-bounding fault over the last 350 kyr. Other geological and morphologic information allows us to estimate the total age of the main fault (∼1 Ma) and to examine the mechanical evolution of the Corinth Rift. The minimum observed sediment thickness in the Gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6–7 mm yr−1 (40 per cent less than estimated with modelling). Even this slip rate is nearly 10 times higher than for comparable features in most of the Aegean and elsewhere in the world.At a larger scale, the spacing and asymmetry of the rift systems in the Aegean suggest strain localization in the upper mantle, with slow extension starting 15 Myr ago or earlier. The more recent (1 Myr), rapid phase of rifting in Corinth partly reactivated this earlier phase of extension. The younger faulting in Corinth appears to result from its present location in the inhomogeneous stress field (process zone) of the south-westward propagating tip of the southern branch of the North Anatolian Fault. We extend these relations to propose a mechanical model for the Late Cenozoic evolution of the Aegean. As the Arabia/Europe collision progressed in eastern Turkey it caused Anatolia to move to the west and the North Anatolian Fault to propagate into the Aegean, where the early slow extension started to be modified about 5 Ma ago. The process of propagation dramatically increased the activity of some but not all of the earlier rifts. The model we present is compatible with tectonic observations, as well as with the seismicity, the palaeomagnetic rotations and the displacement field now observed with GPS and SLR.

Notes: The El Asnam (Algeria) earthquake of 1980 October is the largest earthquake to have occurred in North Africa since instrumental records began (Ms = 7.3). It was caused by movement on a segmented reverse fault which is part of the fault zone that separates the Chelif alluvial plains from the coastal range of the Atlas Mountains. The coastal range is the actively deforming plate boundary between Africa and Eurasia.In this paper, the results of an aftershock study carried out using a 28-station portable network in the epicentral area in the 5 weeks after the main shock are presented. A total of 4517 aftershocks have been located, using both P- and S-phases. Of these 4517 events, 1279 pass a set of quality criteria, and are used to discuss the detailed tectonics of the aftershock zone.The southwestern half of the aftershock zone has a relatively restricted band of seismicity running parallel to the main fault. In cross-section, this seismicity is observed to lie almost exclusively in the footwall of the main fault, and indicates both antithetic reverse faulting and extension parallel to the fault zone. The only exception to this pattern occurs at a junction of the main fault segments, where a distinct cluster of events with very variable focal mechanisms is located in the hangingwall. This cluster may be equated with a barrier that impeded the rupture of the main shock. Beyond the southwest end of the main fault, a mixture of strike-slip and reverse faulting occurred, and suggests a mechanism whereby this end of the fault can act as an asperity for earthquake generation.Aftershocks in the northeastern half of the study area indicate movement on a stack of listric reverse faults. The focal mechanisms of these events show that the N-dipping nodal planes (assumed to be the fault planes) flatten with depth. We suggest that the faults sole into a low-angle (20°) decollement at about 8-10 km depth, at the base of the aftershock zone.We argue that the northeastern part of the 1980 aftershock zone is typical of the actively deforming coastal belt of northwest Algeria. Subduction of the western Mediterranean basin beneath the north African margin does not seem to occur. Instead, the margin is absorbing the motion, with old normal faults being reactivated as thrusts.

Notes: [Auszug] Although displacements across faults have been monitored carefully for some time4'5, there has been almost no study of the transient strains that must be associated with the passage of each creep event. Frank7 has discussed the strain-time histories that can be expected theoretically during typical ...

Notes: [Auszug] SYDENHAM1 has failed to appreciate that problems exist in studies of Earth strain which will not be solved by producing the 'ultimate' Strainmeter. Strain signals cover a wide frequency range, and signal sources and noise vary across the spectrum. The correct way to assess instrument performance is ...

Notes: [Auszug] The first type of geophysical tiltmeter, and by far the most widely used, is that of short baselength (between a few centimetres and a metre) angle sensing systems which include horizontal pendulums and more recently, electrolytic bubble levels. These instruments all suffer from the disadvantage ...

Notes: [Auszug] They are installed NE/SW in a disused railway tunnel in Yorkshire (coordinates 53 46' N, 1 51-5' W, 200 m above sea level). The environmental requirements for strain measurements are very stringent and it appears that Queensbury Tunnel is suitable for many reasons: it is more than ninety years old, ...

Notes: [Auszug] A fold controlling the form of the local topography near El Asnam, Algeria, increased in amplitude at the time of the earthquake of 10 October 1980. The deformation occurred rapidly in an elastic–brittle manner and not in the gradual ductile fashion in which folds are normally thought to ...

Notes: [Auszug] In some cases where several instruments are installed in different parts of the same observatory1 discrepancies between identical instruments have been observed. The discrepancies consist of both variations in amplitude and phase of the observed tidal harmonics and although it is possible to ...