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Instrumental catalogues of earthquakes in the subduction zone of the Lesser Antilles are produced by local observatories and the International Seismological Centre. But none of these catalogues merge all arrival times of the first regional phases available; in addition, they have a magnitude of completeness relatively high for the entire Lesser Antilles area. As part of the Antilles Seismological Data Centre project, we produced a unified catalogue of known earthquakes from 1972 to 2012, with optimal constraints on the hypocentre locations. We re-evaluated the hypocentres with the method used in local observatories and a probabilistic method improving the distributions of arrival time residuals. We developed a simple method to select the preferred hypocentre independently of the localization algorithm, and we offer a complete catalogue including 46,703 earthquakes. Compared to other existing catalogues, we provide additional arrival times for 24,528 earthquakes. Our results highlight the variabilities of the magnitude of completeness and of the seismicity suggesting how the future analysis could infer the mechanisms of heterogeneous seismic coupling and intermediate-depth triggering.

This article is the continuation of a study by authors to create the most complete and representative earthquake catalogs with a unified magnitude scale. The catalog created of the Ossetian sector of the Greater Caucasus (the territory of the Republic of North Ossetia–Alania and adjacent areas) was formed by the aggregation of all available data from Soviet, modern Russian, and Georgian catalogs, as well as the data from the International Seismological Centre. The integration was carried out using the author's approach based on the modified nearest neighbor method. The integrated catalog of the Ossetian sector of the Greater Caucasus contains 16,285 events for the period 1962–2022. For all events, magnitude estimates are reduced to a unified "proxy-MW" scale. The integration of data from various sources made it possible to significantly replenish the beginning of the aftershock sequence of the Racha earthquake with MW = 7.0, which occurred on 29 April 1991. There has been a change in the level of registration over time. Thus, there is a significant lack of events for the periods 1967–1970 and 1988–1991; starting from 1995, the catalog is complete for magnitude 3.2, and since 2005 for magnitude 2.2. The integration of Soviet and modern Russian and Georgian catalogs made it possible to significantly increase the completeness and representativeness of seismic events in the studied Ossetian sector of the Greater Caucasus. This once again demonstrates both the fundamental importance of merging seismic data from global, national, and regional catalogs and the effectiveness of the author's developed method. [ABSTRACT FROM AUTHOR]

This paper represents the final part of a series of studies aimed at creating the most reliable and representative earthquake catalog covering the Russian and European Arctic. The earthquake catalog of the Gakkel and Knipovich ridges, as well as the Svalbard Archipelago with a unified magnitude scale, was formed based on the combination of four regional Russian catalogs and the ISC catalog. The merging of catalogs was carried out using the modification of the author's methodology, which allowed for the identification of records in different datasets related to the same seismic event. The modification was introduced due to significant changes over time in the source catalogs. The unified proxy moment magnitude scale was formed based on regression analysis of the different magnitude estimates provided by various agencies. The integrated catalog included 17,922 earthquakes that occurred during the period 1962–2022. Analysis of the integrated catalog showed that the level of registration in the studied area significantly varies over space and time. Before 1995, the catalog contained only strong and moderate earthquakes, and the magnitude of complete registration Mc was 5.0 in the Gakkel Ridge, 4.7 in the Knipovich Ridge, and 4.5 in the Svalbard Archipelago. The number of recorded events increased in the period 1995–2011, and Mc decreased to 4.0 in the Gakkel and Knipovich ridges and to 2.8 in the Svalbard Archipelago. The best level of registration in the Svalbard Archipelago and the Knipovich Ridge was achieved after 2012, when Mc reached 1.7 and 2.8, respectively. In the Gakkel Ridge, despite a noticeable increase in the number of reported events from 2012, the magnitude of complete registration did not improve and was 4.0. The presented integrated earthquake catalog is intended for a wide range of studies of the seismic regime of the Arctic. [ABSTRACT FROM AUTHOR]

The article is a continuation of the research on creating the most complete and representative earthquake catalogs by combining all available data from regional, national, and international seismological agencies and reducing magnitudes to a uniform scale. The task of identifying and removing duplicates that arise during the merging process is solved using the authors' modification of the nearest neighbor method. It is evident that the intelligent merging of different earthquake catalogs for the same territory will improve the completeness and representativeness of events in the final integrated catalog. In this article, the earthquake catalog of the western sector of the Arctic zone of the Russian Federation (AZRF) covering the period 1962–2022 was created by merging three regional Russian catalogs and the ISC catalog. The ratio of magnitude types in the catalog for different seismic networks was analyzed, and magnitude estimates were unified based on the obtained ratios. For analyzing seismic activity in the western AZRF, it is recommended to use earthquakes from the period 1998–2020 when the catalog was significantly cleaned from explosions and other events of the "non-earthquake" type. [ABSTRACT FROM AUTHOR]

The Caucasus region is a part of ongoing collision of the Arabian and Eurasian plates, where moderate to strong earthquakes caused significant losses of lives and likelihood in the past. Employing the results of the morphostructural analysis and active faults in the region to delineate crustal blocks, and the geodetic observations on crustal movements, we develop a model of block-and-fault dynamics introducing nonlinear rheology of fault zones, and simulate earthquakes in the region. A set of numerical experiments has been performed to answer the following questions: (i) how crustal blocks react to the Arabian plate motion and to movements of the lower crust in the Caucasus; (ii) how earthquakes cluster in the system of major regional faults and generate strong seismicity; (iii) how the focal mechanisms of model events are related to the mechanisms of observed earthquakes; and (iv) how rheological properties of the fault zones influence the earthquake clustering and fault slip rates. The modeling results confirm that the contemporary crustal dynamics and seismicity pattern in the Caucasus are determined by the north-northeastern motion of the Arabian plate relative to Eurasia and the movement of the lower crust overlain by the upper crustal rigid blocks. Variations in the rheological properties of the fault zones and/or of the lower crust influence the displacement rates of the crustal blocks and hence fault slip rates. Clustering of earthquakes can be considered as a consequence of the dynamics of the block-and-fault structure in the region. The number and maximum magnitude of synthetic earthquakes change with the variations in the movements of the crustal blocks and in the rheological properties of the lower crust and the fault zones. The earthquake simulations in the Caucasus region will help to assess seismic hazard using recorded, historical, and simulated events. [ABSTRACT FROM AUTHOR]