Journal Article

Modelling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities

Vassilis Karakostas, Eleftheria Papadimitriou and Dragomir Gospodinov

in Geophysical Journal International

Volume 197, issue 1, pages 525-541
Published in print April 2014 | ISSN: 0956-540X
Published online January 2014 | e-ISSN: 1365-246X | DOI: http://dx.doi.org/10.1093/gji/ggt523
Modelling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities

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The 2013 January 8 Mw 5.8 North Aegean earthquake sequence took place on one of the ENE–WSW trending parallel dextral strike slip fault branches in this area, in the continuation of 1968 large (M = 7.5) rupture. The source mechanism of the main event indicates predominantly strike slip faulting in agreement with what is expected from regional seismotectonics. It was the largest event to have occurred in the area since the establishment of the Hellenic Unified Seismological Network (HUSN), with an adequate number of stations in close distances and full azimuthal coverage, thus providing the chance of an exhaustive analysis of its aftershock sequence. The main shock was followed by a handful of aftershocks with M ≥ 4.0 and tens with M ≥ 3.0. Relocation was performed by using the recordings from HUSN and a proper crustal model for the area, along with time corrections in each station relative to the model used. Investigation of the spatial and temporal behaviour of seismicity revealed possible triggering of adjacent fault segments. Theoretical static stress changes from the main shock give a preliminary explanation for the aftershock distribution aside from the main rupture. The off-fault seismicity is perfectly explained if μ > 0.5 and B = 0.0, evidencing high fault friction. In an attempt to forecast occurrence probabilities of the strong events (Mw ≥ 5.0), estimations were performed following the Restricted Epidemic Type Aftershock Sequence (RETAS) model. The identified best-fitting MOF model was used to execute 1-d forecasts for such aftershocks and follow the probability evolution in time during the sequence. Forecasting was also implemented on the base of a temporal model of aftershock occurrence, different from the modified Omori formula (the ETAS model), which resulted in probability gain (though small) in strong aftershock forecasting for the beginning of the sequence.

Keywords: Friction; Earthquake interaction, forecasting, and prediction; Seismicity and tectonics; Statistical seismology; Rheology and friction of fault zones; Continental tectonics: strike-slip and transform; Dynamics and mechanics of faulting

Journal Article.  9694 words.  Illustrated.

Subjects: Geophysics

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