Earthquake & Volcano Monitor — 2026-04-20
A powerful magnitude 7.5 earthquake struck off the northeastern coast of Japan early on April 20, triggering tsunami warnings and prompting the Japanese government to activate crisis management protocols. On the volcanic front, Mayon Volcano in the Philippines issued a fresh ash advisory this morning, while Kīlauea in Hawaii remains in a paused eruption state with lava fountaining episode 45 forecasted imminently.
Earthquake & Volcano Monitor — 2026-04-20
Seismic Activity
🚨 Major Earthquake Strikes Northern Japan — Tsunami Warning Issued
A magnitude 7.5 earthquake struck off the northeastern coast of Japan on April 20, 2026, with tsunami warnings immediately issued for large coastal areas in northern Japan. Prime Minister Sanae Takaichi announced that the government had set up a crisis management team in response to the powerful event.
Reuters reported the preliminary magnitude at 7.4 before upward revision, with waves expected to reach large coastal areas in northern Japan.
Japan remains one of the world's most seismically active regions, sitting at the convergence of multiple tectonic plates.
Volcanic Watch
🌋 Mayon Volcano (Philippines) — Ash Advisory Issued
Mayon Volcano on Luzon Island in the Philippines issued a Volcanic Ash Advisory through the VAAC Tokyo on April 20, 2026 at 02:00 UTC, reporting an eruption with ash reaching FL100 (approximately 10,000 feet) extending westward. A satellite image from April 18 confirmed ongoing activity at the volcano.
🌋 Kīlauea (Hawaii) — Eruption Paused, Episode 45 Imminent
The USGS Hawaiian Volcano Observatory (HVO) reports that the summit eruption of Kīlauea in Halemaʻumaʻu crater is currently paused, with the alert level at YELLOW/ADVISORY and the aviation color code at YELLOW. Summit inflation is underway and glow has been visible at the south vent.
Forecast models suggest that lava fountaining episode 45 will occur sometime between Monday, April 20 and Saturday, April 25, 2026.
🌋 Great Sitkin (Alaska) — Slow Lava Eruption Continues
Great Sitkin Volcano in the Aleutian Islands, Alaska, remains at WATCH alert level (Aviation Color Code: ORANGE). Lava continues to erupt slowly within the summit crater.
🌍 Global Volcanic Activity Overview
According to the Smithsonian Institution's Global Volcanism Program, 40 volcanoes were reported with continuing eruptions as of the most recent reporting period through March 31, 2026.
The weekly volcanic activity report from The Watchers (covering April 9–15, 2026) noted new activity or unrest at 3 volcanoes and ongoing activity at 17 volcanoes during that period. Reported activity included continuing minor rockfalls on the lava field of Great Sitkin and ongoing reporting by agencies including JMA, KVERT, and USGS-CVO.
Earth Science
🔬 Kikai Supervolcano — Magma System Rebuilding
Scientists have discovered that the magma system linked to the most powerful eruption of the Holocene is slowly rebuilding beneath the Kikai caldera off Japan. Using seismic imaging, researchers mapped a large magma reservoir and confirmed it is the same system responsible for a cataclysmic ancient eruption. While this research was published prior to our 24-hour window, it is directly relevant to ongoing monitoring of the region now experiencing major seismic activity.
Readers in tsunami warning zones in northern Japan should follow official government instructions immediately. Monitor NHK World and Japan Meteorological Agency updates for the latest tsunami wave heights and arrival times.
This content was collected, curated, and summarized entirely by AI — including how and what to gather. It may contain inaccuracies. Crew does not guarantee the accuracy of any information presented here. Always verify facts on your own before acting on them. Crew assumes no legal liability for any consequences arising from reliance on this content.
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