The USGS has confirmed a magnitude 4.7 earthquake with its epicentre 81 km W of San Antonio de los Cobres, Argentina, occurring at 03:09 UTC on Thursday, August 20, 2026. The event's focal depth — 166.7 km — is a key factor in understanding how this earthquake was experienced at the surface.
Why Depth Matters
With a focal depth of 166.7 km, this earthquake falls into the intermediate depth category (70–300 km). At this depth, seismic waves travel further before reaching the surface, spreading energy over a wider area. While shaking intensity at the epicentre is somewhat reduced compared to a shallow event of equal magnitude, an intermediate earthquake can be felt across a much larger region.
Depth is one of the most critical but least discussed parameters of any earthquake. Two earthquakes of identical magnitude can have dramatically different surface effects depending on how deep the rupture originates. Significant damage can occur to vulnerable structures — particularly unreinforced masonry, old adobe buildings, and poorly maintained older construction. Well-engineered modern buildings are designed to withstand this level of shaking with minimal structural impact, though contents may shift and non-structural elements (ceilings, partitions) can be damaged.
Magnitude 4.7: What the Science Says
On the moment magnitude scale, 4.7 represents a moderate earthquake. Moderate earthquakes are felt by virtually everyone near the epicentre. Strong shaking lasting 10–30 seconds can topple unsecured items, crack plaster, and cause poorly anchored objects to fall. Aftershocks are common following moderate events.
A magnitude 4.7 earthquake releases approximately roughly 500 tonnes of TNT of energy. For comparison, this exceeds the energy released by most conventional explosive events and is sufficient to shift tectonic stress in measurable ways across a wide region.
Tectonic Setting
Chile runs along the subduction boundary where the Nazca Plate dives beneath the South American Plate — one of the most seismically active convergent boundaries on the planet. This setting has produced the largest instrumentally recorded earthquake in history.
This region's seismic history is an important reminder that earthquake risk is a long-term reality that requires sustained preparedness. Chile holds the record for the strongest earthquake ever measured: the 1960 Valdivia earthquake at magnitude 9.5. More recently, the 2010 Maule earthquake (M8.8) and its associated tsunami caused widespread damage. Chileans have developed strong earthquake-preparedness culture over generations.
Practical Safety Information
Regardless of the earthquake's depth or magnitude, standard safety procedures apply. Fasten heavy furniture — bookshelves, water heaters, cabinets — to walls using earthquake straps. Store breakable items on lower shelves and heavy items closest to the floor. These simple steps significantly reduce the risk of injury from falling objects.
During and after an earthquake, follow instructions from official civil protection, emergency services, and government authorities. Avoid spreading unverified information on social media. Official channels provide the most reliable information about aftershock risk, evacuation orders, and available assistance.
SHOA (Servicio Hidrográfico y Oceanográfico de la Armada) manages tsunami warnings for Chile, while SENAPRED coordinates national disaster response. Evacuation routes and tsunami inundation maps are posted in most coastal communities.
Track This Event
All seismic data for this event is being updated in real time as the USGS refines its measurements. Initial magnitude and depth estimates are sometimes revised as more seismograph stations report in — a process that typically completes within hours of the event. Follow updates on our live earthquake map and consider submitting a felt report if you experienced this earthquake directly.
How QuakeWatch Tracks This Event
QuakeWatch sources earthquake data directly from the USGS ComCat (Comprehensive Catalog), which aggregates data contributed by seismic networks worldwide including JMA (Japan), EMSC (Europe and Mediterranean), GFZ (Germany and global), Geoscience Australia, and dozens of national and regional networks. This data is refreshed every 60 seconds, ensuring that new earthquakes appear on our live map within minutes of being processed by the USGS. You can also submit a felt report for this earthquake directly on its detail page.
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