Coseismic Displacements from Moderate-Size Earthquakes Mapped by Sentinel-1 Differential Interferometry: The Case of February 2017 Gulpinar Earthquake Sequence (Biga Peninsula, Turkey)

Athanassios Ganas,Alexandra Moshou,Panagiotis Elias,Pierre Briole,Isaak Parcharidis,Penelope Kourkouli

doi:10.3390/rs10071089

Abstract

We study the tectonic deformation from the February 2017 shallow earthquake sequence onshore Biga Peninsula (NW Turkey, NE Aegean region). We use InSAR interferograms (Sentinel-1 satellites) to identify the seismic fault (striking N110°E) and seismological data (parametric data and Moment Tensor solutions from NOA and KOERI catalogues) so as to refine its geometry and kinematics using inversion techniques. Despite the moderate magnitudes of the main events of the sequence (5.0 ≤ Mw ≤ 5.2), the total surface deformation is 2.2 fringes (or maximum 6.2 cm along LOS) and it is well visible with InSAR because of the shallow depth of the four main events (6–8 km) and the good coherence of the signal phase. Our geodetic inversion showed that the fault has normal-slip kinematics, dimensions of 6 by 6 km (length, width) and dips at 45°. The InSAR data are fitted by a uniform slip of 28 cm. In addition, 429 earthquakes were relocated with the HypoDD software and the use of a 1-D velocity model. The dip-direction of the fault is not retrievable from InSAR, but a south-dipping plane is clear from seismology and the aftershocks distribution. The spatial distribution of relocated events indicates the activation of one fault with a rupture zone length of about 10 km, a result of the occurrence of off-fault aftershocks along strike the main rupture. A stress inversion using 20 focal mechanisms (M ≥ 3.6; NOA solutions) indicates that faulting accommodates a N196°E extension. It is confirmed that moderate (5.0 ≤ M ≤ 5.2) shallow events can be traced in InSAR studies and can produce surface displacements that provide useful data in fault inversion.

Highlights

In February 2017, a shallow seismic sequence of moderate events hit the region of Gulpinar-Babakale, onshore northwestern Anatolia, Turkey (Table 1, Figure 1)
We study the tectonic deformation from the February 2017 shallow earthquake sequence onshore Biga Peninsula (NW Turkey, NE Aegean region)
Despite the moderate magnitudes of the main events of the sequence (5.0 ≤ Mw ≤ 5.2), the total surface deformation is 2.2 fringes and it is well visible with InSAR because of the shallow depth of the four main events (6–8 km) and the good coherence of the signal phase

Summary

Introduction

In February 2017, a shallow seismic sequence of moderate events hit the region of Gulpinar-Babakale, onshore northwestern Anatolia, Turkey (Table 1, Figure 1). The four main events with magnitudes between 5.0 ≤ Mw ≤ 5.2 (moment magnitude determination by National Observatory of Athens—NOA), occurred on 6 February 2017 (Mw = 5.2; 03:51 UTC and Mw = 5.0; 10:58 UTC), Remote Sens. 2018, 10, x FOR PEER REVIEW 2 of 20 2 of 20. Ased quickFloy.urTteweno weveaeknetrs eovfeMntswoc=cu4r.4readnbdetw4.e0e,nthFaetbroucacruyr6readndon28JwanituhaMryw 1b4etwaneden135.6, 2a0n1d74,.6m, tihgehnt tbhee seen retrosspeiescmtiicvietylydaecsrfeoarseedshqoucikcksl.yT. January to March 2017 NOA location and moment tensor parameters of earthquakes of Mw ≥

Methods

Results

Conclusion