A swarm of strong earthquakes is currently shaking Kamchatka Peninsula, Russian Far East. The strongest in series was M 5.9 (USGS), M 6.0 (EMSC), recorded at 20:44 UTC on May 19, 2013. Data for depth of this earthquake is still uncertain. USGS measured 16.5 km whereas EMSC is reporting 10 km.
First earthquake in the region today was reported at 0:39 UTC when a 74 km deep, magnitude 4.9, earthquake struck. At 1:29 UTC a 4.8 magnitude earthquake struck at depth of 84 km. By 18:00 UTC four more M4+ earthquakes were reported. At 19:44 M 5.1 struck at depth of 40 km. In following minutes, M 4.7 and M 4.9 struck at depth of approximately 55 km.
Magnitude 5.9 earthquake, the strongest so far, struck at 20:44 UTC and was followed by M 4.6, M 5.1, M 4.9, M 5.0 and M 5.1 in next 60 minutes. The area is still shaking.
Kamchatka Peninsula lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west. Immediately offshore along the Pacific coast of the peninsula runs the 10.5 km (34,400 ft) deep Kuril-Kamchatka trench. Deep-focus seismic events and tsunamis are fairly common in the region. A pair of megathrust earthquakes occurred off the coast on October 16, 1737, and on November 4, 1952, in the magnitude of ~9.3 and 8.2 respectively.
Today's swarm region is part of The Kuril-Kamchatka arc which extends approximately 2,100 km from Hokkaido, Japan, along the Kuril Islands and the Pacific coast of the Kamchatka Peninsula to its intersection with the Aleutian arc near the Commander Islands, Russia. It marks the region where the Pacific plate subducts into the mantle beneath the Okhotsk microplate, part of the larger North America plate. This subduction is responsible for the generation of the Kuril Islands chain, active volcanoes located along the entire arc, and the deep offshore Kuril-Kamchatka trench. (Seismotectonics of the Kuril-Kamchatka Arc)
There are 320 000 people living on Kamchatkan Peninsula which is famous for a high density of volcanoes and associated volcanic phenomena. The Kamchatka River and the surrounding central side valley are flanked by large volcanic belts containing around 160 volcanoes, 29 of them still active. Kamchatka is also a home to the largest active volcano in the Northern Hemisphere, a 4,750 m high, Klyuchevskaya Sopka.
Puerto Rico swarm
Meanwhile, a smaller scale swarm struck off the coast of Puerto Rico. At 7:42 UTC, a magnitude 3.1 earthquake at depth of 60 km was reported by USGS. 8 minutes later M 2.9 struck at depth of only 8 km. By 17:41 UTC eleven more earthquakes were reported. All earthquakes were M 2.6+ with strongest being M 4.1 at 14:58 UTC.
Damaging earthquake in Algeria
Another significant seismic event today was 10 km deep M 5.1 (EMSC), M 4.9 (USGS) earthquake that hit northern Algeria at 9:07 UTC. The Algerian officials said it was M 5.5 earthquake. By 19:00 UTC 5 people were reported as indirectly injured, none seriously. A lot of buildings suffered minor damage like cracks. EMSC's I felt it report mentions 15 seconds or longer shake.
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