Institute of Earthquake Prediction Theory and Mathematical Geophysics

Abstract We consider the Schrödinger equation with a multipoint potential of the Bethe−Peierls−Thomas−Fermi type. We show that such a potential in dimension d = 2 or d = 3 is uniquely determined by its scattering amplitude at a fixed positive energy. Moreover, we show that there is no non-zero potential of this type with zero scattering amplitude at a fixed positive energy and a fixed incident direction. Nevertheless, we also show that a multipoint potential of this type is not uniquely determined by its scattering amplitude at a positive energy E and a fixed incident direction. Our proofs also contribute to the theory of inverse source problem for the Helmholtz equation with multipoint source.

The Gutenberg–Richter law establishes a log-linear relationship between the number of earthquakes that have occurred within some spatiotemporal volume and their magnitude. This similarity property presumably reflects fractal structure of the fault system in which earthquake sources are formed. The Gutenberg–Richter law plays a key role in the problems of seismic hazard and risk assessment. Using the Gutenberg–Richter relationship, we can estimate the average recurrence period of strong earthquakes from the recurrence rate of weaker earthquakes. Since the strongest earthquakes occur infrequently, with intervals of a few hundred years or more, it is not possible to directly assess their recurrence. From indirect geologic and paleoseismic estimates it often seems that strong earthquakes on individual faults occur more frequently than expected in accordance with the Gutenberg–Richter law. Such estimates underlie the hypothesis of the so called characteristic earthquakes. This hypothesis is in many cases additionally supported by the form of the magnitude–frequency distributions for individual faults, constructed from the data of modern earthquake catalogs. At the same time, an important factor affecting the form of the magnitude–frequency distribution is the choice of the spatial domain in which the distribution is constructed. This paper investigates the influence of this factor and determines the conditions under which the Gutenberg–Richter law is applicable for estimating the recurrence of strong earthquakes.

This paper verifies the compliance of the earthquake productivity law (Shebalin et al., 2020a) in laboratory experiments on rock destruction. Westerly granite and Benheim sandstone specimens were subjected to uniaxial loading under uniform compression. An acoustic-emission (AE) recording system made it possible to create catalogues of AE sources similar to earthquake catalogues. The data from experiments conducted at the Rock Friction Laboratory (USGS, Menlo Park, United States) and the Geomechanics and Rheology Laboratory (GFZ, Potsdam) were analyzed. It was found that the AE events in the considered samples are characterized by a unimodal distribution of the nearest-neighbor proximity function. The compliance of the productivity law for acoustic-emission events in laboratory experiments on the destruction of rock samples is shown, which gives grounds to speak about the similarity of grouping processes in real seismicity and in laboratory conditions.

The spatial clustering of epicenters of seismic events in the Northwest Pacific Ocean is analyzed using the Discrete Perfect Sets (DPS) topological filtering algorithm. The results of the analysis are presented in this paper. Based on the data shallow earthquakes recorded from 1963 to 2022 by the seismic network of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences, stable areas of epicenter clustering are identified. These areas are associated with the Northern and Southern segments of the Kuril-Kamchatka seismofocal zone and do not depend on the time of recording of the earthquakes. The characteristic clustering radius for the Kuril-Kamchatka seismofocal zone is determined and is found to be 42–44 km. The analysis has confirmed the unique pattern of seismicity in the territory of the Commander segment of the Aleutian arc, which differs from that observed in the Northern and Southern segments.

We consider the December 27, 2023, earthquake (mb = 5.4) that occurred on the margin of the Siberian Platform, on the northwestern slopes of the Akitkan Ridge. The earthquake epicenter is spatially associated with a structural suture (deep thrust fault) separating the Siberian Platform and the Baikal fold belt. The seismic event was followed by hardly any aftershocks. Its maximum shaking intensity was IV (MSK-64); it was observed at distances up to 180 km. The December 27, 2023, Akitkan earthquake is localized in a previously aseismic region, far from active areas of the Baikal Rift. It suggests a new look at seismic activity of fault structures bordering the Siberian Platform. The focal mechanism, determined from P-wave first-motion polarities at regional stations, demonstrates normal fault movements on inclined fault planes with a submeridional strike, which agrees with the orientation of the structural suture. This does not contradict seismogeological data indicating that an inversion of tectonic movements can be observed in some segments of the deep thrust fault zones. The December 27, 2023, Akitkan earthquake confirms modern seismic activity of the Akitkan seismic source zone and the fundamental possibility of relatively strong seismic events being generated by marginal structures of the Siberian Platform.

The key parameters of an earthquake are magnitude, epicenter coordinates, and depth. Depth often has a decisive influence on the macroseismic effect of certain earthquakes. In this regard, for example, to assess seismic risk, one should know information on the statistics of earthquake occurrence at certain depths. In this work, catalogs of continental crustal earthquakes in the Southern Siberia are analyzed. The distributions of earthquake depths are approximated by various functions. The Weibull distribution, with a maximum at 8 km, is shown to describe the depth distribution of these crustal earthquakes most accurately. When the western (Altai–Sayan) and eastern (Baikal Rift Zone) parts of the region are considered separately, the Weibull distribution is also preferable. The maximum of the distribution is found to be at 9 km for the Baikal rift zone and at 7 km for the Altai–Sayan zone.

An algorithm for identifying seismic generation zones or “seismic domains” using fuzzy logic has been developed and tested on the island of Sakhalin. Initial data were obtained from diagrams of the distribution of “weak” zones, relief elevation distribution skewness, and magnitude of recent area deformation for one year. These data were processed using a γ-operator in fuzzy logic with γ = 0.9, which allowed us to identify areas with high seismic activity. The areas where these active areas intersect with zones with increased compressive stress values, as determined by computer modeling, were considered to be seismic zones. It was shown that, if there are not enough source materials available, it is possible to exclude information about the recent deformation field from consideration and use an assumed grid of active faults for computer modeling. This approach may be useful when analyzing areas that have not been studied well.

Abstract—On February 6, 2023, two devastating earthquakes struck southern central Turkey, nine hours apart. The ground shaking from these earthquakes even swept over a significant part of northwestern Syria. In this paper, we consider the locations of the epicenters of these earthquakes against the prediction of the М ≥ 6.5 earthquake epicenters in Anatolia and adjacent regions, which was made in 1973 by I.M. Gelfand, V.I. Keilis-Borok and their colleagues using the Kora-3 pattern recognition algorithm based on morphostructural zoning data. We also present the results of early detection of the periods with an increased probability of the strongest earthquakes as determined by the medium-term prediction algorithm for the M8 earthquakes. It is found that the epicenters of the February 6, 2023 earthquakes occurred in a node identified in 1973 as potentially earthquake-prone for М ≥ 6.5, and both events occurred within the spatial and temporal coverage of the warning area diagnosed by the M8 algorithm in July 2021.