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This paper presents a new model of seismic rupture surface for the Chignik Mw 8.2 earthquake which occurred off the Alaska Peninsula on July 29, 2021. The model is based on data on surface displacements obtained by satellite radar interferometry from Sentinel-1A and 1B images and on horizontal GPS displacements in the area of this earthquake. We used satellite radar images for the period between July 17 and August 10, 2021, as well as GPS data for the period between July 18 and August 8, 2021. All of these displacements include both coseismic movements and some postseismic displacements. The rupture surface model was developed using F. Pollitz' solution to the problem concerning the displacement field at the surface of a spherical radially stratified planet due to a rectangular rupture inside the planet. The inversion was regularized by requiring that the direction of displacement at each element of the rupture plane be close to a specified direction as given by seismological data. The seismic rupture surface in this model is fitted by a plane extending for 225 km along strike and 126 km along dip, and which is subdivided into 48 identical elements. According to the model derived here, the type of displacement is a nearly pure thrust, with the displacement in general involving all of the rupture zone. The maximum slip was 5.7 m, with the mean slip as averaged over the entire rupture plane being 2.2 m. Assuming the shear modulus to be 32 GPa, we found the seismic moment based on the parameters of the plane we have derived and on the displacements on it as 1.95 × 1021 N m (Мw = 8.13), which is near the USGS and GCMT estimates based on seismological data. [ABSTRACT FROM AUTHOR]

Two strike–slip faults, displacements along which caused the catastrophic earthquakes in Turkey on February 6, 2023, were mapped from satellite radar interferometry data. According to the satellite data, the relative displacements of the sides of the East Anatolian Fault Zone (EAFZ), with which the first event of Mw 7.8 was associated, exceeded 5 m in the central segment. The rupture surface extends from the area of the Doğanyol-Sivris earthquake Mw 6.7 of January 24, 2020, in the north to the Mediterranean coast in the south, where the earthquake Mw 6.3 occurred on February 20, 2023. The second event Mw 7.5 is associated with the Surgü-Çardak fault; the relative displacements of its sides, according to satellite data, exceeded 7 m. The obtained displacement fields of the Earth's surface were used to construct a model of the seismic rupture. This model was worked out on the basis of the Pollitz, 1996 solution, which defines displacements on the surface of the spherically stratified planet as a result of along dip and strike displacements on a rectangular rupture located inside the sphere. Ignoring the spherical stratification of the planet leads to errors of up to 20%, especially in the presence of a large strike–slip component [5]. Ignoring sphericity also causes an error, when using the solution obtained for an elastic homogeneous half-space, as the US Geological Survey (USGS) has done, in modeling the seismic rupture for earthquakes in Turkey in 2023. Our model differs in the detailed consideration of the fault geometry. For this purpose, the faults were approximated by 19 planes along the strike, divided into two levels along the dip. In our rupture model strike–slip displacements in the central segment of the EAFZ reached 12.7 m. In the southern segment of this rupture, the displacements are much smaller. It should be emphasized that we registered the displacements for the period from January 29, 2023, to February 10, 2023; therefore, together with co-seismic ones, they also include post-seismic displacements for four days after the main seismic events. The displacements on the rupture surface along the Surgü-Çardak Fault, where the Mw 7.5 earthquake occurred, were up to 10 m. The results demonstrate, in particular, the efficiency of application of the satellite radar interferometry in the operative study of catastrophic geodynamic phenomena and processes. [ABSTRACT FROM AUTHOR]

Abstract—For the first time, based on the synthetic-aperture radar interferometry data (InSAR), a surface rupture model of the earthquake that occurred on January 12, 2021 beneath Lake Khuvsgul (Khubsugul, Khövsgöl), Mongolia, is built. In the constructed model, the rupture of this region-largest instrumental event strikes northwest, has a dip angle of 45°, a slip rake angle in the interval from –130° to –150°, and a mean displacement of 1 m. The rupture extends to a depth of 18 km and has a strike length of 26 km. In contrast to the surface rupture model built by the US Geological Survey from seismological data, the model based on the InSAR data shows that in the northern part of the lake, the main Khuvsgul fault strikes northwest. The obtained result requires increasing the existing estimates of the length of the seismogenic part of the Khuvsgul fault severalfold. [ABSTRACT FROM AUTHOR]

Abstract—The last activation of the Koryakskii volcano in 2008–2009 was accompanied by intense fumarolic and seismic activity. Volcanic activity peaked in March–April 2009 when ash plume rose to a height of 5.5 km and extended laterally over more than 600 km. To understand the dynamics of the volcanic processes and to forecast the further course of the events, it is relevant to establish whether the eruption was associated with a rise of magma to beneath the volcanic edifice or caused by fracturing of the volcano's basement and penetration of groundwater into a high temperature zone. Based on the analysis of the images from the Japanese satellite ALOS-1 using satellite radar interferometry methods, the slope displacements of the Koryakskii volcano during its last activation have been estimated for the first time. The displacements reach 25 cm and cannot be explained by the formation of a layer of volcanic ash deposits or by the slope processes. The most likely cause of the displacements should be recognized to be the intrusion of magmatic material into the volcano edifice with the formation of a fracture with its lower edge at a depth of 0.5 km above sea level, with a size of 1.0 and 2.4 km along the strike and dip, respectively, and with a dip angle from 45° to 60°. Therefore, the processes taking place beneath the volcano can be threatening to the nearby localities and infrastructure and require continuous monitoring. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X2307019X [ABSTRACT FROM AUTHOR]