The 2014 Kefalonia Doublet (MW6.1 and MW6.0), Central Ionian Islands, Greece: Seismotectonic Implications along the Kefalonia Transform Fault Zone

Abstract

The 2014 Kefalonia earthquake sequence started on 26 January with the first main shock (M w 6.1) and aftershock activity extending over 35 km, much longer than expected from the causative fault segment. The second main shock (M w 6.0) occurred on 3 February on an adjacent fault segment, where the aftershock distribution was remarkably sparse, evidently encouraged by stress transfer of the first main shock. The aftershocks from the regional catalog were relocated using a 7-layer velocity model and station residuals, and their distribution evidenced two adjacent fault segments striking almost N-S and dipping to the east, in full agreement with the centroid moment tensor solutions, constituting segments of the Kefalonia Transform Fault (KTF). The KTF is bounded to the north by oblique parallel smaller fault segments, linking KTF with its northward continuation, the Lefkada Fault.

High-precision relocation of seismic sequences above a dipping Moho: the case of the January–February 2014 seismic sequence on Cephalonia island (Greece)

“…The western dip in combination with the oblique-slip rake may result in uplift of the hanging wall (western) of the N-S fault during co-seismic motion. Our relocation procedure suggests a different fault model than that of Karakostas et al (2014;their Fig. 8), who suggested a right step of CTFZ, on the Paliki peninsula.…”

Seismicity rate modeling for prospective stochastic forecasting: the case of 2014 Kefalonia, Greece, seismic excitation

“…The offshore seismicity is the result of either static or dynamic triggering of smaller faults, which strike obliquely to the KTF. Later on Sakkas and Lagios (2015), using geodetic data, proposed a rupture model of two segments in agreement with Karakostas et al (2014a). Figure 3 shows the relocated aftershocks up to the end of June 2014.…”

“…Further to the north, however, an offshore cluster with rather low magnitude earthquakes was developed. An interpretation based upon the epicentral distribution attributes this pattern to the first rupture with a length of 12 km, being stopped due to a strong asperity coinciding with the low seismicity area (Karakostas et al 2014a).…”

“…Both shocks were followed by numerous aftershocks increasing even more the feeling of anxiety and the willingness of people to know more about the ongoing seismic activity. The properties of the seismic sequence were studied by the use of precise aftershock locations resulted from the recordings of a dense digital seismic network (Karakostas et al 2014a). These authors also presented evidence of seismicity triggering in the along-strike adjacent fault segment, due to the static stress changes from the first main shock.…”

“…Figure 3 shows the relocated aftershocks up to the end of June 2014. Relocation was performed by hypoinverse and the double difference technique using appropriate velocity model and station corrections (Karakostas et al 2014a). The phase data are included in the monthly bulletins of the Geophysics Department of the Aristotle University of Thessaloniki.…”