Integrated Earthquake Catalog III: Gakkel Ridge, Knipovich Ridge, and Svalbard Archipelago

Abstract

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.

Integrated Earthquake Catalog of the Ossetian Sector of the Greater Caucasus

“…Magnitudes mb ISC and mb NEIC are known for 259 events. Magnitude mb ISC ≈ MW GCMT (Figure 10a), which corresponds to the ISC practice of using magnitude mb as a proxy-MW for earthquakes with M < 5.0 [6,30]. Also, mb ISC ≈ mb NEIC (Figure 10b).…”

“…As noted above, the author's method, used in the present study to identify duplicates that arise when earthquake catalogs are sequentially merged, is described in detail in [1] (see Supplementary Materials). The application of this method to create the most complete earthquake catalog with a unified magnitude scale for the Arctic zone of the Russian Federation is given in [4][5][6]. For this reason, a description of the method is not provided in this article.…”

“…Therefore, in the present paper the actual distribution of the metric for the nearest events from the two catalogs being merged is used instead of the multivariate normal distribution model. The effectiveness of this approach is shown in [6]. We believe that the maximum metric value for possible duplicate events is Ro = 30; this corresponds to the difference in time and space of the order of 1.5 min and 600 km.…”

“…When merging catalogs, the preference is given to earthquake records from the ISC catalog that have magnitude definitions MW GCMT and/or mb ISC and/or mb NEIC [4][5][6]. As shown in Table 1, in the region considered, a large majority of seismic events are registered by GS RAS seismic networks.…”

“…It allows the identification and removal of duplicate events that occur when the catalogs are merged. Previously, the integrated catalog was elaborated for the Arctic zone of the Russian Federation [4][5][6]. It is demonstrated that merging catalogs of various global, national, and regional seismic networks makes it possible to improve the completeness and representativeness of seismic events in the studied region [7][8][9][10].…”