No abstract

On February 6, 2023, two large earthquakes occurred near the Turkish town of Kahramanmaraş. The moment magnitude (Mw) 7.8 mainshock ruptured a 310 km-long segment of the left-lateral East Anatolian Fault, propagating through multiple releasing step-overs. The Mw 7.6 aftershock involved nearby left-lateral strike-slip faults of the East Anatolian Fault Zone, causing a 150 km-long rupture. We use remote-sensing observations to constrain the spatial distribution of coseismic slip for these two events and the February 20 Mw 6.4 aftershock near Antakya. Pixel tracking of optical and synthetic aperture radar data of the Sentinel-2 and Sentinel-1 satellites, respectively, provide near-field surface displacements. High-rate Global Navigation Satellite System data constrain each event separately. Coseismic slip extends from the surface to about 15 km depth with a shallow slip deficit. Most aftershocks cluster at major fault bends, surround the regions of high coseismic slip, or extend outward of the ruptured faults. For the mainshock, rupture propagation stopped southward at the diffuse termination of the East Anatolian fault and tapered off northward into the Pütürge segment, some 20 km south of the 2020 Mw 6.8 Elaziğ earthquake, highlighting a potential seismic gap. These events underscore the high seismic potential of immature fault systems.

Water vapour and its variations in the Earth's atmosphere are related to atmospheric activities and climate changes. However, it is difficult to obtain high-resolution and high-accuracy precipitable water vapour (PWV) and its variations using traditional techniques, particularly in Turkey with the complex weather variability caused by the proximity of the Black Sea and the Mediterranean Sea. Satellite observations provide unique ways to observe PWV variations at regional or global scale, e.g. global positioning system (GPS). In this study, long-time PWV variations and trends are investigated and obtained from 6-year continuous GPS observations in Turkey (January 2010-January 2016), which are compared with nearly co-located radiosonde and moderate resolution imaging spectroradiometer (MODIS) observations to check its accuracy. The root mean square error (RMSE) of PWV differences is about 1-3 mm between radiosonde and GPS, and 3-7 mm between MODIS and GPS. Furthermore, the linear trend and seasonal amplitudes, and phase of the GPS-estimated PWV signals are computed. Statistically significant trends are found at all stations. While stations near the Mediterranean Sea have increasing trends with about 0.30 mm year −1 , the stations at inland have increasing trends of about 0.10 mm year −1 . The annual phases between radiosonde, GPS and MODIS PWV at all the stations are almost close to each other with differences in 1 ∘ -2 ∘ . Finally, the relation between north Atlantic oscillation (NAO) and PWV trends is investigated. Results show that PWV trends agree with NAO behaviours especially for the stations near the Mediterranean Sea. The recent human activities may have impacts on long-term PWV variation trends.

No abstract

No abstract