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

Abstract

We inferred the rupture process of the 2015 Lefkada earthquake by combining teleseismic and near‐field strong motion data, together with static and dynamic GPS displacements. The joint inversion of all data sets revealed a relatively complex slip pattern with a heterogeneous distribution. Slip is confined in the upper 10 km. Two principal asperities with peak slip amplitude of 2.35 m, which released 65% of the total seismic moment, were recovered southwest of the epicenter. Remarkably, the 2015 earthquake ruptured the part of the Cephalonia Transform Fault Zone that remained unbroken during the 2003 event, revealing a pattern of rupture segmentation along the fault zone. In this context the Lefkada segment can be divided into a northern and southern part. Preseismic deformation onshore southern Lefkada revealed that since the 2003 rupture, the northern part of the Lefkada segment continuously loaded the southern part, which eventually broke during the 2015 event.

On the Segmentation of the Cephalonia–Lefkada Transform Fault Zone (Greece) from an InSAR Multi-Mode Dataset of the Lefkada 2015 Sequence

“…Our F1 segment is the only one that could be compared to other slip models, at a first approximation, as published slip distributions are only provided for a single fault segment. Our estimated peak slip of 2.9 m is comparable to the 2.3 m calculated by Chousianitis et al [9]. Additionally, our model predicts a small slip pattern to the northeast of the Lefkada island.…”

“…Additionally, our model predicts a small slip pattern to the northeast of the Lefkada island. This patch, with slightly different characteristics, also appears in the models of Avallone et al [7] and Chousianitis et al [9].…”

“…Initially, we attempted to jointly model our InSAR results with GPS data [9,10,12]. However, the joint geodetic inversion led to large residuals in both datasets.…”

“…On 17 November 2015, an earthquake (Mw 6.4) ( Figure 1b) struck the western coast of Lefkada island, which stimulated a wealth of publications [7][8][9][10][11][12][13][14][15][16][17][18]. Sokos et al [19] were the first to identify that the mainshock broke a strong asperity, left unbroken, in-between two large subevents of the previous 2003 doublet earthquake of Mw 6.2.…”

“…Moreover, this slip patch was defined to be at depths >10 km, and [8] claim that it was not well resolved by their dataset. It must be noted, though, that monitoring tectonic phenomena in the Ionian Sea is a challenging task, and to elucidate the fault segmentation is difficult due to the sparse distribution of the seismographic and geodetic data, as previously mentioned also by [8,9,12,19].…”