Analysis of seismicity in Kamchatka and Japan demonstrates that, within the framework of nonlinear dynamical systems, it is possible to estimate the key parameters of a system of equations acting as a “generator” of the seismic regime. Based on the introduced seismic parameter, estimates are obtained for the embedding dimension and the fractal dimension of the phase portrait for the dynamic seismicity system. The former indicates the dimension (the required number of equations) of the dynamical system needed to describe the seismic regime, whereas the latter reflects the degree of chaos (randomness) in the system’s solution. This analysis spans a wide range of energy, spatial, and temporal scales. A distinct shift in the properties of such a system generating the dynamics of seismicity is observed in association with the Tohoku megaearthquake.
The evolution of tectonic faults and localization of strong earthquake sources are controlled by the configuration and rheological properties of tectonic asperities. Seismogenic spots are a seismic manifestation of tectonic asperities and can be identified on the basis of spatiotemporal analysis of seismicity, namely, they represent topologically dense spatial groups of background seismicity. This study investigates the seismicity patterns of the Kamchatka Subduction Zone (KSZ), where the oceanic Pacific Plate subducts beneath the continental Okhotsk Plate along the Kamchatka Peninsula. We used the regional seismic catalog from the Kamchatka Branch, Geophysical Survey, Russian Academy of Sciences, which includes 38 886 events recorded from January 1, 1990, to September 14, 2025. The magnitude of completeness (Mc) for the catalog is 3.0. Seven seismogenic spots, with characteristic sizes ranging from 150 to 250 km, are identified within the KSZ. The structuring of these spots is shown to persist throughout the entire 35-year observation period. The boundaries of the seismogenic spots are consistent with the structural features of the subducting Pacific plate. Within these seismogenic spots, 18 out of 23 epicenters of earthquakes with magnitudes greater than 7 that have occurred in the region since 1900 are localized. The source structure of the strongest Kamchatka megaearthquake Mw 8.8 on July 29, 2025, which reflects the configuration of tectonic asperities, is in full agreement with the configuration of the KSZ seismogenic spots.
The article analyzes volcanic swarms during periods of magma intrusion at Redoubt and Augustine volcanoes from the perspective of seismic regime. It is shown that the two volcanic swarms observed prior to the 2009 eruption of Redoubt Volcano differ in both their temporal energy release patterns and their frequency-magnitude distribution (b-value). Furthermore, the second swarm, occurring immediately before the eruption, features a more prominent strongest event, with the majority of other strong events clustering within a few hours prior to it (considering the swarm’s total duration of approximately three days). Abruptly following the strongest event, the seismic energy release drops sharply, which deviates from the classical pattern of swarm activity. The number of events and their maximum magnitudes showed a gradual increase from the swarm’s onset toward the strongest event. Furthermore, a decrease in the b-value was observed prior to the strongest event, compared to the elevated values recorded at the beginning of the swarm. These patterns are also identified during the intrusion period preceding the 2006 eruption of Augustine Volcano, though over a longer temporal scale. Such behavior is successfully explained within the framework of rock failure and magma intrusion models.
Using ground-based magnetometer stations and vertical ionospheric sounding stations, we investigate the intensification of variations in the geomagnetic field and ionospheric electron density associated with the July 29, 2025 strong megathrust Kamchatka earthquake and its aftershocks over a thousand km from the observation stations. The recorded anomalous geomagnetic and electron density variations are interpreted as resulting from the propagation of three types of earthquake-induced waves: seismic Rayleigh waves, atmospheric internal waves originated at the earthquake epicenter, and slow magnetohydrodynamic waves generated via the transformation of atmospheric waves in the lower ionosphere.
Paleomagnetic studies were performed on red-colored siltstones from the lower part of the Early Ediacaran Kumakh-Ulakh Formation (western slope of the Aldan Shield, southern Siberian Platform), representing a postglacial sequence associated with the Marinoan glaciation (645–635 Ma). Under the Geocentric Axial Dipole (GAD) model, the obtained results indicate a near-equatorial position of the Siberian Platform during the deposition of the Kumakh-Ulakh Formation, which supports the Snowball Earth hypothesis. On the other hand, the distribution pattern of the Kumakh-Ulakh Formation virtual geomagnetic poles may indicate the contribution of an equatorial-dipole component to the Early Ediacaran geomagnetic field, thus deviating from the actualistic GAD model. In this case, the result cannot be used to support the Snowball Earth hypothesis. Regardless of the geomagnetic field configuration during the time period under consideration, the obtained paleomagnetic data suggest that the post-Marinoan deglaciation processes were not associated with a significant change in the latitudinal position of the Siberian Platform. This conclusion, however, is based on the assumption of a constant contribution of the axial and equatorial dipole components to the main geomagnetic field during the Late Cryogenian and Early Ediacaran.
