Golshadi, Zeinab

In this work, we propose a geodetic model for the seismic sequence, with doublet earthquakes, that occurred in Bandar Abbas, Iran, in November 2021. A dataset of Sentinel-1 images, processed using the InSAR (Interferometric Synthetic Aperture Radar) technique, was employed to identify the surface deformation caused by the major events of the sequence and to constrain their geometry and kinematics using seismological constraints. A Coulomb stress transfer analysis was also applied to investigate the sequence’s structural evolution in space and time. A linear inversion of the InSAR data provided a non-uniform distribution of slip over the fault planes. We also performed an accurate relocation of foreshocks and aftershocks recorded by locally established seismographs, thereby allowing us to determine the compressional tectonic stress regime affecting the crustal volume. Despite the very short time span of the sequence, our results clearly suggest that distinct blind structures that were previously unknown or only suspected were the causative faults. The first Mw 6.0 earthquake occurred on an NNE-dipping, intermediate-angle, reverse-oblique plane, while the Mw 6.4 earthquake occurred on almost horizontal or very low-angle (SSE-dipping) reverse segments with top-to-the-south kinematics. The former, which cut through and displaced the Pan-African pre-Palaeozoic basement, indicates a thick-skinned tectonic style, while the latter rupture(s), which occurred within the Palaeozoic–Cenozoic sedimentary succession and likely exploited the stratigraphic mechanical discontinuities, clearly depicts a thin-skinned style.

The ML 5.8 earthquake that hit the island of Crete on 27 September 2021 is analysed with InSAR (Interferometry from Synthetic Aperture Radar) and GNSS (Global Navigation Satellite System) data. The purpose of this work is to create a model with sufficient detail for the geophysical processes that take place in several kilometres below the earth’s surface and improve our ability to observe active tectonic processes using geodetic and seismic data. InSAR coseismic displacements maps show negative values along the LOS of ~18 cm for the ascending orbit and ~20 cm for the descending one. Similarly, the GNSS data of three permanent stations were used in PPK (Post Processing Kinematic) mode to (i) estimate the coseismic shifts, highlighting the same range of values as the InSAR, (ii) model the deformation of the ground associated with the main shock, and (iii) validate InSAR results by combining GNSS and InSAR data. This allowed us to constrain the geometric characteristics of the seismogenic fault and the slip distribution on it. Our model, which stands on a joint inversion of the InSAR and GNSS data, highlights a major rupture surface striking 214◦, dipping 50◦ NW and extending at depth from 2.5 km down to 12 km. The kinematics is almost dip-slip normal (rake −106◦), while a maximum slip of ~1.0 m occurred at a depth of ca. 6 km. The crucial though indirect role of inherited tectonic structures affecting the seismogenic crustal volume is also discussed suggesting their influence on the surrounding stress field and their capacity to dynamically merge distinct fault segments.

On 18 April 2021, a MW 5.8 earthquake occurred near the city of Bandar-e Genaveh, southwestern Iran. Four synthetic aperture radar (SAR) images, acquired from Sentinel-1 (ESA Copernicus project) satellites in ascending and descending orbits, were used to get two displacement maps, catching the surface co-seismic effects through the two-pass InSAR technique. Modeling the deformation patterns using equations for a shear dislocation in elastic half-space allowed the source parameters and the slip distribution of the seismogenic source to be determined. We calculated that the rupture occurred on a reverse fault extending NW-SE, gently dipping NE and with a maximum slip reaching about 1 m. The northeast and low-dip angle of this fault are also consistent with the tectonics of the region, which is subject to deformation and shortening along the northern margin of the Arabian plate. Our estimations of the fault parameters agree with the Zagros Foredeep reverse fault. We additionally processed four other SAR images to investigate the possibility that the Mw 5.0 aftershock, which occurred about one month later, induced surface effects visible with InSAR. This analysis, however, did not provide any clear conclusions.

We have reinterpreted the causative fault parameters of the 2005 Zarand earthquake in the light of a new imagery study using Interferometric Synthetic Aperture Radar (InSAR). By conducting a joint inversion of two InSAR datasets, we can characterize the rupture as it relates to complex local structures. At first, the mainshock ruptured a nearly pure reverse fault, dipping ~65° NNW in the basement below the southeastern area of Zarand. Two more fault segments were subsequently activated: an oblique‐normal fault segment parallel to the first segment, dipping 61° to the south, and a normal‐oblique fault segment at the eastern termination of the rupture zone. The first fault segment ruptured the surface, while slip along the other two segments was confined to the lower sedimentary strata.