Strain and rotation rate patterns of mainland Greece from continuous GPS data and comparison between seismic and geodetic moment release

Abstract

We processed data from~100 continuous GPS stations to provide new insights into the crustal motion and deformation of central and western Greece. We used the derived velocity field to evaluate two-dimensional strain and rotation rate tensors, and we mapped the dilatation and maximum shear strain rates. In central Peloponnese and Epirus, we documented a 90°switch in the extension direction, which can be explained on the basis of the plate boundary configuration. Evidence for an extended deformation pattern in central Greece was found. Additionally, we detected two pairs of shear belts, one in Akarnania-NW Peloponnese and one in North Aegean. We delineated two rotational domains that dominate the present-day pattern. Moreover, we saw no geodetic evidence for North Anatolian Fault growth toward central Greece. We translated the geodetic strain rates into rates of seismic moment release and compared them with earthquake catalog-based moment rates. In the central Ionian Sea, the geodetic strain is completely released seismically, which is indicative of a fully coupled seismogenic zone. However, for most of the study area, the geodesy-based moment rates are at least 2 times higher than the earthquake-based rates. We attribute this mainly to earthquake catalog representativity over the long-term situation. However, for the Gulf of Corinth, it is unrealistic to associate the high ratio of geodetic to seismic moment rates only to incompleteness of the earthquake catalog; instead, long-term aseismic deformation must be an important mechanism accommodating a considerable portion of the strain budget, especially at its western part.

Slip model of the 17 November 2015 Mw = 6.5 Lefkada earthquake from the joint inversion of geodetic and seismic data

“…Ganas et al [2013] showed that the northern part of Lefkada was moving faster than the southern part toward the N-S direction. Furthermore, at southern Lefkada, Chousianitis et al [2015] calculated increased negative dilatation rates in conjunction with decreased maximum shear strain rates compared to the strain rate pattern of the rest central Ionian Sea (Figure 4 of their paper; Figure S8). Furthermore, at southern Lefkada, Chousianitis et al [2015] calculated increased negative dilatation rates in conjunction with decreased maximum shear strain rates compared to the strain rate pattern of the rest central Ionian Sea (Figure 4 of their paper; Figure S8).…”

“…The high level of seismicity at central Ionian Sea is imprinted at the geodetic strain which is completely released seismically, pointing to a fully coupled seismogenic zone [Chousianitis et al, 2015]. This area constitutes one of the most active zones of shallow seismicity in the Aegean and surrounding regions, where strong ground shaking has repeatedly occurred as a result of moderatemagnitude events.…”

Relocation of recent seismicity and seismotectonic properties in the Gulf of Corinth (Greece)

“…1; Armijo et al 1996). Geodetic measurements have shown that the extension rate is different in the two parts of the gulf (Billiris et al 1991;Clarke et al 1998;Briole et al 2000;Avallone et al 2004;Chousianitis et al 2015). The western part extends at a rate of 13-14 mm yr −1 , with the largest opening rate measured near Aigio fault (Fig.…”

Coseismic Slip Distribution of the 12 June 2017 Mw = 6.3 Lesvos Earthquake and Imparted Static Stress Changes to the Neighboring Crust

“…Precise orbits from the International Global Navigation Satellite Systems (GNSS) Service for Geodynamics (IGS) and IGS absolute antenna phase center corrections for satellite and receiver antennas were used, and the data of several IGS stations with tightly constrained a priori values in the International Terrestrial Reference Frame 2008 (Altamimi et al, ) were also included. More details about the phase data processing step can be found in Chousianitis et al () and the references therein. Next, the daily loosely constrained bias‐fixed solutions of the parameters and their associated covariance matrices were passed as quasi‐observations in GLOBK and we produced position time series in the International Terrestrial Reference Frame 2008 (Figure S2).…”