Surface Deformation Analysis of the Wider Zagreb Area (Croatia) with Focus on the Kašina Fault, Investigated with Small Baseline InSAR Observations.

Marin Govorčin,Boško Pribičević,Shimon Wdowinski

doi:10.3390/s19224857

Marin Govorčin, Boško Pribičević + Show 1 more

Open Access

https://doi.org/10.3390/s19224857

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Abstract

The wider Zagreb area is considered one of the few seismically active areas in the Republic of Croatia. During the period 1880–1906, moderate to strong seismic activity with three earthquakes magnitude ML ≥ 6 occurred on the NW-SE striking Kašina Fault and since then, the area has not experienced earthquakes exceeding magnitude ML = 5. In order to estimate the ongoing interseismic strain accumulation along the fault, we analyze Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) and Environmental Satellite (Envisat)-Advanced Synthetic Aperture Radar (ASAR) datasets acquired over the period 2007–2010 and 2002–2010, respectively. The data were analyzed using small baseline interferometry (SBI) technique and indicate very slow surface deformations in the area, within ±3.5 mm/year, which are in a good agreement with previous geodetic studies. Interseismic strain accumulation analysis was conducted on two 14 km long segments of the Kašina Fault, seismically active in the South and stable in the North. The analysis indicates an ongoing interseismic strain accumulation of 2.3 mm/year on the Southern segment and no detectable strain accumulation on the Northern segment. Taking into consideration the lack of moderate to strong seismic activity in the past 113 years combined with the preliminary geodetic analysis from this study, we can conclude that the Southern segment of the Kašina Fault has the potential to generate earthquake magnitude Mw < 6.

Highlights

On 9 November 1880, a strong earthquake hit the wider Zagreb area and caused destruction of 13% of buildings in the city of Zagreb
We focus on providing an initial surface deformation analysis of interseismic strain accumulation on the Kašina Fault based on InSAR data
Fault, which could be due to the sparse distribution right-lateral horizontal movements

Summary

Introduction

On 9 November 1880, a strong earthquake (estimated ML ≈ 6.3 reported in Prelogović et al [1]) hit the wider Zagreb area and caused destruction of 13% of buildings in the city of Zagreb. The area afterward experienced two more earthquakes ML ≈ 5.9 in 1905 and 1906 with epicenters that coincide with the 1880 earthquake [2]. The earthquake epicenters were estimated to be on the Southern segment of the strike-slip Kašina. Based on seismological data of the past 100 years, a 150 years recurrence interval for earthquakes magnitude ML > 6 is estimated for the wider Zagreb area (see Markušić and Herak [3]), suggesting that the strong earthquake might occur in the decades. The wider Zagreb area has significant socio-economic importance for the Republic of Croatia as it generates over 50% of the Croatian gross national product and home for about

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