US volcano alert level RAISED after California earthquake and ‘increased seismicity’
On Thursday, July 4 a magnitude 6.4 earthquake struck in southern California at 10.34 local time (4.34pm BST), with strong to very strong shaking felt in Ridgecrest. Shaking was felt by millions of people according to the United States Geological Survey (USGS), with areas including Los Angeles and Las Vegas reporting to feel the quake. Following the earthquake, multiple aftershocks have been felt - with 50 to 700 recorded as magnitude three or higher according to the USGS. On July 4, a magnitude 4.5 earthquake also struck 280 miles (450km) from Unalaska and has been followed by further smaller quakes. Today alone, (July 5) 13 quakes ranging from magnitude 1.1 to magnitude 3.6 have shaken Alaska. Now the threat level for volcanoes has been upgraded following the increased seismicity. According to the Alaska Volcano Observatory (AVO) and USGS: “Due to an increase in seismicity above background levels over at least the last eight hours AVO is raising the Aviation Colour Code to YELLOW and Alert Level to ADVISORY at Semisopochnoi. Read More: Earthquake today: Katla, Etna, Kilauea and Mount St Helens rumble “No explosive activity has been detected on the Adak infrasound array and clouds currently obscure satellite views of the volcano. “AVO will continue to monitor the volcano using satellite, infrasound and seismic data.” On July 4, a magnitude 4.5 earthquake struck 450km from Unalaska, and has been followed by further smaller quakes. Semisopochnoi is an island which is part of the Rat Islands group, in the western Aleutian Islands of Alaska. The island is uninhabited, and is an important area for maritime birds, with many breeds choosing to nest there. Alaska is no stranger to earthquakes, as several tectonic features in the area can produce high magnitude quakes. According to the Alaska Earthquake Centre, the Aleutian megathrust is the source of the strongest earthquakes in the region, such as the 1938 M8.3 earthquake southwest of Kodiak Island. These earthquakes are capable of producing damaging tsunamis, as was documented in historical records of Russian settlers and in recently discovered paleo-tsunami deposits. Both Alaska and California are located on the explosive Ring of Fire, a horseshoe-shaped area spanning 40,000 km around the basin of the Pacific Ocean. Within the Ring of Fire, there are oceanic trenches, volcanic arcs, volcanic belts and plate movements almost continuously. About 90 percent of the world’s earthquakes and 81 percent of the world’s largest earthquakes occur along the Ring of Fire. In terms of volcanoes, all but three of the world’s 25 largest volcanic eruptions of the last 11,700 years occurred at volcanoes in the Ring of Fire.
On Thursday, July 4 a magnitude 6.4 earthquake struck in southern California at 10.34 local time (4.34pm BST), with strong to very strong shaking felt in Ridgecrest. Shaking was felt by millions of people according to the United States Geological Survey (USGS), with areas including Los Angeles and Las Vegas reporting to feel the quake. Following the earthquake, multiple aftershocks have been felt – with 50 to 700 recorded as magnitude three or higher according to the USGS. On July 4, a magnitude 4.5 earthquake also struck 280 miles (450km) from Unalaska and has been followed by further smaller quakes. Today alone, (July 5) 13 quakes ranging from magnitude 1.1 to magnitude 3.6 have shaken Alaska. Now the threat level for volcanoes has been upgraded following the increased seismicity. According to the Alaska Volcano Observatory (AVO) and USGS: “Due to an increase in seismicity above background levels over at least the last eight hours AVO is raising the Aviation Colour Code to YELLOW and Alert Level to ADVISORY at Semisopochnoi. Read More: Earthquake today: Katla, Etna, Kilauea and Mount St Helens rumble “No explosive activity has been detected on the Adak infrasound array and clouds currently obscure satellite views of the volcano. “AVO will continue to monitor the volcano using satellite, infrasound and seismic data.” On July 4, a magnitude 4.5 earthquake struck 450km from Unalaska, and has been followed by further smaller quakes. Semisopochnoi is an island which is part of the Rat Islands group, in the western Aleutian Islands of Alaska. The island is uninhabited, and is an important area for maritime birds, with many breeds choosing to nest there. Alaska is no stranger to earthquakes, as several tectonic features in the area can produce high magnitude quakes. According to the Alaska Earthquake Centre, the Aleutian megathrust is the source of the strongest earthquakes in the region, such as the 1938 M8.3 earthquake southwest of Kodiak Island. These earthquakes are capable of producing damaging tsunamis, as was documented in historical records of Russian settlers and in recently discovered paleo-tsunami deposits. Both Alaska and California are located on the explosive Ring of Fire, a horseshoe-shaped area spanning 40,000 km around the basin of the Pacific Ocean. Within the Ring of Fire, there are oceanic trenches, volcanic arcs, volcanic belts and plate movements almost continuously. About 90 percent of the world’s earthquakes and 81 percent of the world’s largest earthquakes occur along the Ring of Fire. In terms of volcanoes, all but three of the world’s 25 largest volcanic eruptions of the last 11,700 years occurred at volcanoes in the Ring of Fire.
