# Integrated Earthquake Catalog III: Gakkel Ridge, Knipovich Ridge, and Svalbard Archipelago
It should be noted that the Gakkel Ridge is undisturbed by transform faults [7, 8, 9]. Similar characteristics of spreading rates and structure are also present in the eastern segment of the Southwest Indian Ridge. This is reflected in similar seismic activity features that distinguish these ridges from ridges with slow and medium spreading rates [10]. Based on the morphological features and deep structure, the Gakkel Ridge is divided into three provinces: the Western Volcanic Zone (WVZ) (7\({}^{\circ}\) W-3\({}^{\circ}\) E), the central Sparsely Magmatic Zone (SMZ) (3\({}^{\circ}\) E-30\({}^{\circ}\) E), and the Eastern Volcanic Zone (EVZ) (30\({}^{\circ}\) E-85\({}^{\circ}\) E) [1,2]. Despite its lower spreading rate, the WVZ is characterized by extensive magmatic processes, which are reflected in the similarity of its relief to that of the Mid-Atlantic Ridge rift zone. The maximum depth of the WVZ reaches 4.3 km. The length of volcanic ridges identified in its central part ranges from 15 to 50 km, with heights ranging from 0.4 to 1.4 km. The rift valley is composed of basalts, and several hydrothermal plumes have been identified within it [7,11,12]. In contrast, the SMZ is characterized by rare manifestations of magmatism, with a single large volcanic center located in the 19\({}^{\circ}\) E area. The maximum depth of the rift valley is 4.8-5.4 km [6,7,12]. Within the EVZ, extended magmatic sections with gentle slopes and lengths of 40-120 km separated by volcanic centers can be distinguished. The maximum depth of the magmatic sections is 4.8-5.1 km. The largest volcanic center of the Gakkel Ridge is located in the eastern part of the segment, in the 85\({}^{\circ}\) E area [6,7,12]. In 1999, an unprecedented surge in seismic activity was recorded there. It was caused by an effusive-explosive underwater volcanic eruption. The seismic network deployed on ice floes allowed for the registration of a swarm of 209 events with hypocenter depths up to 25 km [3,4]. Based on the data  
Figure 1: Scheme of the Arctic region and seismic networks. The red line is the boundary between North American and Eurasian plates. The red dotted line is the part of the boundary after the Gakkel ridge. WVZ and EVZ are the Eastern and the Western Volcanic Zones in the Gakkel ridge, and SMZ is the Sparsely Magmatic Zone [1,2]; a star marks the location of volcanic eruption and earthquake swarm in 1999 [3,4]. Arrows show the spreading direction. Triangles are seismic stations of European and Russian networks (see legend). obtained in [13], a seismic tomography model was constructed. The combination of ultra-slow spreading rates with low potential mantle temperatures leads to the production of low-temperature, volatile-rich magmatic melts. Explosive underwater eruptions occur as a result of the degassing of these melts [13; 14]. Maximum magnitudes are recorded in the eastern segment of the Gakkel Ridge (in the Laptev Sea). The strongest earthquake within the Gakkel Ridge, with \(MS\) = 6.5 (International Seismological Centre), occurred there on 25 August 1964 [15]. The epicenters of two earthquakes with \(MW\) = 6.4 and \(MW\) = 6.2 (Global Centroid-Moment-Tensor), which occurred on 21 March 1988 and 6 March 2005, respectively, were also located in this area [16]. The Svalbard Archipelago includes more than a thousand small and large islands, among which West Spitsbergen, Prince Charles Land, Barents Island, Edge, and Northeast Land can be distinguished. More than half of the archipelago's area is covered by glaciers. The first temporary seismic station was installed in 1911 in Longyearbyen. Subsequently, several analog stations were installed in Kapp Linne (1958-1963), Ny-Alesund (1967), Hornsund (1978), Barentsburg (1979), and Pyramid (1982-1989). In addition, several large-scale seismic surveys were conducted on Phipps Island, Southern Spitsbergen, and Northeast Land in 1976-1986 to study the tectonic structure of the region [17; 18].