The Investigation of Tropospheric Changes with GNSS: A study on 6 February 2023 Kahramanmaraş Earthquake Sequence

Abstract

The earthquakes that occurred in Kahramanmaraş on February 6, 2023, are among the significant seismic events in Turkey. Recorded at moment magnitudes of 7.8 and 7.6 in ten hours on East Anatolian Fault Zone (EAFZ), these earthquakes resulted in extensive destruction and loss of lives in the region. The effects of these earthquakes have been actively studied following the events, utilizing geodetic measurement techniques, particularly GNSS measurements, which are commonly employed in earthquake studies for determining tectonic movements and crustal deformations. As known, GNSS signals pass through significant atmospheric layers, namely the ionosphere and troposphere, before reaching the Earth's surface, and the influence of these atmospheric layers is evident in the results due to various error sources within these layers. One of the main limiting factors in studies such as determining crustal movements is the influence of the troposphere, as surface velocities are on the order of a few mm/yr and require high accuracy (at the mm level). In this study, changes in the troposphere during the earthquakes on February 6, 2023, were investigated using tropospheric zenith delays (Zenith Total Delay - ZTD) computed from GNSS observations. The results indicate the presence of zenith tropospheric delay anomalies at stations close to the fault rupture during and after the main shock, while no such anomalies were observed at distant stations from the fault rupture zone. This finding indicates a relationship between earthquakes and changes occurring in the troposphere.