The short-term seismicity of the Central Ionian Islands (Greece) studied by means of a clustering model

Abstract

SUMMARY Earthquake clustering in the area of Central Ionian Islands (Greece) is statistically modelled by means of the Epidemic Type Aftershock Sequence (ETAS) branching model, which is the most popular among the short-term earthquake clustering models. It is based upon the assumption that an earthquake is not fully related to any other one in particular, but rather to both all previous events, and the background seismicity. The close temporal proximity of the strong ($M \ge 6.0$) events in the study area offers the opportunity to retrospectively test the validity of the ETAS model through the 2014 Kefalonia doublet (Mw 6.1 and Mw 6.0) and the 2015 Lefkada aftershock sequences. The application of a physics-based earthquake simulator to the local fault system produced a simulated catalogue with time, space and magnitude behaviour in line with the observed seismicity. This catalogue is then used for the detection of short-term interactions between both strong and smaller events and the comparison between the two cases. The results show that the suggested clustering model provides reliable forecasts of the aftershock activity. Combining the ETAS model and the simulator code, though, needs to be more deeply examined since the preliminary results show some discrepancy between the estimated model parameters.

Variations in hazard during earthquake sequences between 1995 and 2018 in western Greece as evaluated by a Bayesian ETAS model

“…This study revealed that the joint implementation of physics-based approaches and the statistical ETAS model is beneficial for future OEF systems. Kourouklas et al (2020) Mangira et al (2020), revealing that the employed ETAS clustering model provides reliable forecasts of the aftershock activity for this region.…”

An Earthquake-Clustering Model in North Aegean Area (Greece)

“…The model considers earthquakes as the realization of a Hawkes process, namely as a point with coordinates (x, y, t, m) corresponding to its geographical position (x, y), occurrence time (t) and earthquake magnitude (m). As in previous publications [7,8,23], we neglected depth as a spatial coordinate. We based this decision on the fact that the depths of the crustal earthquakes in our catalog range between 3 and 15 km.…”

Strong Earthquakes Recurrence Times of the Southern Thessaly, Greece, Fault System: Insights from a Physics-Based Simulator Application

“…The maximum magnitude that the simulator generates will also be influenced by the effect of the value of A-R. A wide range of Aσ values are reported, ranging from 0.0012 to 0.6 MPa, obtained from different earthquake sequences (Harris, 1998;Harris and Simpson, 1998). Mangira et al 2020 tested values ranging between 0.04 and 0.09 MPa in the Central Ionian Islands (Greece), with a value equal to Aσ 0.06 MPa found to be the most appropriate. Console et al 2020 used values between 0.01 and 1.0 Mpa concluding Aσ 0.05 MPa for Central Italy.…”

“…These improved versions were successfully applied to simulate the seismicity of Calabria (Console et al, 2017;Console et al, 2018b) and Central Apennines (Console et al, 2018a) in Italy. The latest version of the algorithm incorporates the effect of the Rate and State Constitutive law proposed by Dieterich 1994 in the physical processes, leading to a stochastic manner of nucleation with applications in Central Italy (Console et al, 2020) and Greece (Mangira et al, 2020).…”