GNSS TIME SERIES ANALYSIS RELATED TO EARTHQUAKE OF THE Mw 6.2 PETRINJA

Abstract

<p>A devastating earthquake (Mw 6.2) occurred on December 29, 2020,  near the town of Petrinja, in Croatia, a few kilometers north of the Bosnian border with Croatia. The earthquake affected Bosnia and Herzegovina as well, and many buildings in northwestern Bosnia and Herzegovina were severely damaged. The main earthquake impact was preceded by two strong for-shocks, which shows a great resemblance to the Banja Luka earthquake of 1969. Seismic activity at the end of December 2020 and January 2021 was manifested through the occurrence of a large number of seismic events, namely: one earthquake of magnitude 6.2, two earthquakes of magnitude between 5.0 and 6.0, twenty-two earthquakes of magnitude between 4.0 and 5.0, sixty-six earthquakes of magnitude 3.0 and 4.0 and two hundred and seventy-seven earthquakes of magnitude between 2.0 and 3.0. This earthquake is a consequence of the movement of the Adriatic microplate and its interaction with the Eurasian tectonic plate. Its movement results in the creation of current seismicity in Croatia, Bosnia and Herzegovina, Italy, Montenegro, Serbia, Slovenia.</p><p>Today, analysis of the deformations of the Earth's crust plays an important role in research related to the entire seismic cycle. The phases of seismic cycles can be reliably estimated using time series of daily coordinates from continuously operating stations of the Global Navigation Satellite System (GNSS).</p><p>In this study, we used five time-series GNSS positions (Sarajevo, Poreč, Ljubljana, Požega, and Zadar), daily resolutions (24 hours) in the IGS14 reference frame, taken from Nevada Geodetic Laboratory through the website. We determined the coseismic displacement field of the Mw 6.2 Petrinja mainshock using downloaded the GNSS time-series as well as coseismic displacement field for all earthquakes of magnitude over 4. We processed data for the GNSS time series for the period from January 2016 to December 2020. GNSS stations are located at distances ~100 km to the ~250 km distances the epicenter of the Petrinja earthquake, of which the Poreč station is the closest. JavaScript Object Notation (JSON) text format was used for processing all earthquakes in our study. JSON offset file is created based on the data downloaded from USGS (U.S. Geological Survey).</p><p>This paper, apply interactive processing in tectonics and seismology, presented offset in time series as a consequence of earthquakes. We have concluded that the cumulative movement of the Earth's crust is not only a consequence of large earthquakes but also the cause of many smaller accumulated movements caused by smaller earthquakes. The paper presents the contribution in the field of application of satellite positioning methods in geodynamic research and defines an approach that enables objective quantification of deformations of the Earth's crust in cases of seismic events. The earthquake occurred in a fault that extends approximately in the northwest-southeast direction and passes through Pokuplje near Petrinja and Glina. This fault is the boundary between two very different tectonic blocks, the Dinarides and the Pannonian Basin. Therefore, it can be said that the different stresses and displacements in these blocks are compensated through these blocks.</p>