Crustal strain in central Greece from repeated GPS measurements in the interval 1989-1997

Abstract

International audienceA 66-station GPS network spanning central Greece, first observed in 1989, has been occupied fully on three occasions: June 1989, October 1991 and May 1993. Subsets of this network bounding the Gulf of Korinthos have also been occupied in June 1995, October 1995, May 1996 and September/October 1997. The first three occupations were processed using a fiducial GPS methodology, whereas later surveys were processed using CODE precise orbits. Combination of data from different surveys to yield smooth site velocities requires global network translations at each epoch to compensate for errors in the realization of the reference frame. This method provides a posteriori estimates of the relative coordinate errors and reference frame noise. Only one earthquake, the 1995 June 15 Egion event, has caused significant local coseismic displacement, and its effects on the interseismic velocity field are removed using an elastic dislocation model.We constrain the orientation of the 100 yr triangulation–GPS velocity estimates of Davies et al. (1997) using 14 sites common to the two networks. The goodness of fit of this transformation indicates that the short-term and 100 yr geodetic estimates of deformation are highly compatible. We infer that short-term geodetic studies are capable of determining longer-term deformation rates provided that transient, local effects can be modelled. From the combined velocity field, we estimate principal strains and rigid-body rotation rates at points on a regular grid using data from neighbouring sites. Strain rates are high within the Gulf of Korinthos and much lower elsewhere. The extension rate across the Gulf of Korinthos increases from east to west. Comparison of the extension rate with historical and recent rates of seismic release of strain reveals significant medium-term seismic hazard in the western Gulf of Korinthos, and may also indicate long-term aseismic strain.

Patterns of Quaternary uplift of the Corinth rift southern border (N Peloponnese, Greece) revealed by fluvial landscape morphometry

“…This accelerated Holocene uplift is also consistent with the observed discrepancy between hiceeding 10 mm year -1 in the central rift according to geodetic measurements (Clarke et al, 1998;Avallone et al, 2004), and much lower long-term rates, smaller than 5 mm year -1 during the last 0.7 Ma in the same area . Furthermore, the intriguing westward increase in GPS-derived extension rates (e.g., Bell et al, 2011) parallels the S R -inferred westward decrease in age of the recent uplift acceleration.…”

“…Furthermore, the intriguing westward increase in GPS-derived extension rates (e.g., Bell et al, 2011) parallels the S R -inferred westward decrease in age of the recent uplift acceleration. Therefore, we suggest that, rather than betraying a long-term feature (Clarke et al, 1998), the E-W gradient in GPS rate might be a short-term feature resulting from high impulse rates located at the tip of an E-W propagating extension/uplift signal and rapidly decaying to lower rates once the signal is passed. This reconciles the GPS data with the main body of evidence by decoupling it from the longterm data.…”

Crust-mantle mechanical coupling in Eastern Mediterranean and Eastern Turkey

“…A c. 20 mm∕y rightlateral strike-slip motion along the North Anatolian Fault Zone (NAFZ) and 9 mm∕y left-lateral motion along the East Anatolian Fault (EAF) accommodate the westward escape of Anatolia. The GPS velocity field from a dataset I compiled from several sources (3,(11)(12)(13)(14)(15)(16)(17) and four IGS stations (GPSVELv1.0) (18) with respect to GSRM-APM-1, an Absolute Plate Motion (APM) reference frame (19), is given in Fig. 1.…”

Seismotectonic content by the source parameters of the 10 June 2012 Ölüdeniz-Fethiye (Dodecanese Islands) Mw 6.1 earthquake and aftershocks (southwestern Turkey)

“…The western Anatolian, southern Aegean and western Mediterranean lithospheres move on average 25 mm year -1 anticlockwise in relation to the Eurasian plate (Clarke et al 1998;McClusky et al 2000;Ayhan et al 2002;Meade et al 2002). While the subduction rate is 18 mm year -1 along the Hellenic Arc in the south of the Mediterranean, the Pliny-Strabo fault located in the north of the Hellenic Arc and Fethiye-Burdur fault yield a 10 mm year -1 movement defined by the Global Positioning System (GPS) (Reilinger et al 2006).…”