Asperity break after 12 years: The Mw6.4 2015 Lefkada (Greece) earthquake

• Published in: Geophysical research letters 2016-06, Vol.43 (12), p.6137-6145
• Main Authors: Sokos, E., Zahradník, J., Gallovič, F., Serpetsidaki, A., Plicka, V., Kiratzi, A.
• Format: Article
• Language: English
• Subjects: Cephalonia Transform Fault; earthquake complexity; segmentation; slip inversion; strike‐slip fault; strong asperity
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL069427

The Mw6.4 earthquake sequence of 2015 in western Greece is analyzed using seismic data. Multiple point source modeling, nonlinear slip patch, and linear slip inversions reveal a coherent rupture image with directivity toward the southwest and several moment release episodes, reflected in the complex aftershock distribution. The key feature is that the 2015 earthquake ruptured a strong asperity, which was left unbroken in between two large subevents of the Mw6.2 Lefkada doublet in 2003. This finding and the well‐analyzed Cephalonia earthquake sequence of 2014 provide strong evidence of segmentation of the major dextral Cephalonia‐Lefkada Transform Fault (CTF), being related to extensional duplex transform zones. We propose that the duplexes extend farther to the north and that the CTF runs parallel to the western coast of Lefkada and Cephalonia Islands, considerably closer to the inhabited islands than previously thought. Generally, this study demonstrates faulting complexity across short time scales (earthquake doublets) and long time scales (seismic gaps). Key Points Mw6.4 earthquake in 2015 ruptured strong ~20 km long asperity, which was skipped over during previous Mw6.2 doublet in 2003 The asperity that ruptured in 2015 had been silent since the 2003 event and was short of aftershocks after its breakage Cephalonia Transform Fault is geometrically complex, segmented and located closer to inhabited islands than previously thought