Asperity break after 12 years: The M_w6.4 2015 Lefkada (Greece) earthquake

Abstract

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).

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“…(Figure 7c). This is reminiscent of the behavior of earthquakes rupturing fault gaps left unbroken by previous earthquakes and initiating in highly stressed areas at the edges of past ruptures [e.g., Wei et al, 2013;Ye et al, 2014;Sokos et al, 2016]. It is, however, difficult to draw a strong conclusion based on these results as they are dependent on our modeling assumptions and regularization.…”

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