Earthquake & Volcano Monitor — 2026-04-21
Aftershocks and international attention continue to follow the powerful Mw 7.5 Sanriku earthquake that struck off the coast of Japan on April 20, while Hawaii's Kīlauea volcano is primed for its next lava fountaining episode. Multiple volcanoes across the globe remain active, with Bulusan in the Philippines maintaining low-level unrest and Láscar in Chile prompting early warning alerts.
Earthquake & Volcano Monitor — 2026-04-21
Seismic Activity
Japan Sanriku Earthquake — Mw 7.5
A major seismic event struck off the Sanriku coast of Japan on Monday, April 20, 2026 at 4:53 p.m. local time. The quake registered a moment magnitude of Mw 7.5 according to the Global Centroid Moment Tensor (GCMT), with a USGS finite fault model estimating a rupture area of 70 km × 65 km and a maximum slip of 4.735 m near the hypocenter. The observed source time function gives a 12-second duration for the rupture process. A tsunami warning was issued following the event.
Initial reports from various agencies gave the magnitude as 7.7, though the GCMT and subsequent analyses settled on Mw 7.5. The earthquake shook northern regions of Japan and prompted an urgent travel safety advisory amid ongoing concerns over elevated mega-quake risk in the Sanriku region.
The Wikipedia list of 2026 earthquakes was updated within the past 8 hours, reflecting new data from the Sanriku event and other recent seismic activity globally.
Volcanic Watch
Kīlauea, Hawaiʻi — Episode 45 Imminent
The Hawaiian Volcano Observatory (HVO) has placed Kīlauea at Alert Level ADVISORY / Aviation Color Code YELLOW, reporting that the summit eruption in Halemaʻumaʻu is currently paused. However, USGS forecast models based on summit inflation indicate that lava fountaining episode 45 is likely to occur sometime between Tuesday, April 21, and Sunday, April 26. Kīlauea has been erupting episodically since December 23, 2024, from two vents (north and south) in Halemaʻumaʻu.
Bulusan Volcano, Philippines — Alert Level 1
Bulusan Volcano continues at Alert Level 1 (low-level unrest) as of April 21, 2026. The Philippine Institute of Volcanology and Seismology's 24-hour observation summary confirmed ongoing monitoring with no significant escalation in activity.
Láscar Volcano, Chile — Early Warning Issued
Chilean authorities have issued a Preventive Early Warning Monitoring for the commune of San Pedro de Atacama due to elevated activity at Láscar Volcano in the Antofagasta Region, effective April 20, 2026 at 15:30 local time. Residents and visitors in proximity have been advised to remain alert.
Global Eruption Overview
According to the Smithsonian Institution's Global Volcanism Program, approximately 40 volcanoes have continuing eruptions as reported through the end of March 2026, though typically around 20 are actively erupting at any given moment.
Earth Science
No significant new peer-reviewed research findings published after 2026-04-19 were available in today's research results for this section. Monitoring agencies continue to emphasize that Japan's Sanriku region remains under elevated seismic scrutiny following yesterday's Mw 7.5 event, given the historical context of catastrophic megaquakes along this subduction zone. Residents and travelers are encouraged to follow guidance from the Japan Meteorological Agency and local authorities regarding aftershock risks and tsunami preparedness.
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.
Powered by
