M5.6 Earthquake: Southern Mid-Atlantic Ridge

Updated 09:06 UTC · 29 Oct 2026

A magnitude 5.6 earthquake struck southern Mid-Atlantic Ridge at 13:06 UTC on 29 Sep 2026, at a depth of 10 km, reported by USGS. USGS PAGER issued a green alert: little or no damage and a low chance of deaths. USGS did not set a tsunami flag for this quake. No M2.5+ aftershock had been listed within 50 km when this page was updated.

M5.6

Magnitude (USGS)

mww

10 km

Depth

shallow

GREEN

USGS PAGER impact alert

estimated impact

Aftershocks M2.5+ so far

within 50 km

[ fig. 1 ] M5.6 EPICENTRE, AFTERSHOCKS AND PAST QUAKESThis quakeAftershock M5+AftershockPast M6+

USGS · updated 09:06 UTC 2026-10-29Tap a point for details · pinch or ctrl + scroll to zoomTrack this live in the app ›

Nearest places

Edinburgh of the Seven Seas, Tristan da Cunha, Saint Helena399 km from the epicentre · quake was WNW of here · population 271399 KM
Arraial do Cabo, Rio de Janeiro, Brazil2,850 km from the epicentre · quake was ESE of here · population 26,1632,850 KM
Armação de Búzios, Rio de Janeiro, Brazil2,852 km from the epicentre · quake was ESE of here · population 23,4632,852 KM
São João da Barra, Rio de Janeiro, Brazil2,855 km from the epicentre · quake was ESE of here · population 20,6062,855 KM
Cabo Frio, Rio de Janeiro, Brazil2,855 km from the epicentre · quake was ESE of here · population 108,2392,855 KM

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Strongest aftershocks so far

No M2.5+ aftershock listed yet.

Key context

Tectonic setting

Mid-Atlantic Ridge. This is a mid-ocean ridge, where two plates pull apart and new sea floor forms. Quakes here are shallow and frequent, but they rarely pass M7 and happen far from people, so they seldom cause damage or a large tsunami.

The USGS moment tensor shows strike-slip faulting: the two sides of the fault slid sideways past each other.

At 10 km it was a very shallow quake: shallow quakes shake the ground above them hardest, so local damage depends on how close towns are.

Shaking and impact

USGS PAGER estimates the impact from the shaking and the number of people exposed. For this quake it issued a green alert: little or no damage and a low chance of deaths (fatality alert: green, economic loss alert: green). PAGER is an early estimate and can change as reports come in.

USGS had no "Did You Feel It?" reports for this quake when this page was updated; remote and offshore quakes often get none.

Aftershocks

This page counts quakes of M2.5 or more within 50 km after the main shock, from the USGS catalog (last checked 09:06 UTC, 29 Oct 2026): 0 aftershocks so far.

Aftershocks are normal after a quake of this size. They usually become less frequent over days and weeks, but a strong aftershock can still happen, and in a few sequences a later quake is larger. No one can predict their exact time or size; follow the official agency for your area.

Earthquake history within 250 km

Since 1976, USGS lists 90 quakes of M5 or more within 250 km of this epicentre, about 1.8 a year. Since 1900 the same circle had 42 quakes of M5.6 or larger.

Largest earlier quakes within 250 km, USGS catalog since 1900 (M6+).
Magnitude	Place (USGS)	Date	Depth
M7.0	southern Mid-Atlantic Ridge	2015-06-17	10 km
M6.6	southern Mid-Atlantic Ridge	2005-02-16	10 km
M6.4	southern Mid-Atlantic Ridge	1981-06-03	10 km
M6.4	southern Mid-Atlantic Ridge	1989-09-13	12 km
M6.3	southern Mid-Atlantic Ridge	1998-01-03	10 km
M6.3	southern Mid-Atlantic Ridge	1998-04-25	10 km
M6.3	Tristan da Cunha region	1960-08-20	15 km
M6.2	southern Mid-Atlantic Ridge	1939-08-02	10 km

Official information

EMSC (European-Mediterranean Seismological Centre)
USGS event page for this quake (ShakeMap, PAGER, felt reports)
tsunami.gov for US tsunami bulletins

Data status

USGS review status: reviewed. Magnitude type: mww. USGS last updated this event on 22 Oct 2026 at 20:41 UTC. Magnitude, depth and location can still be revised; this page keeps the same address if they change.

Questions and answers

How strong was the earthquake southern Mid-Atlantic Ridge?

USGS measured it at magnitude 5.6 (mww), 10 km deep. Quakes of M5 to 5.9 are classed as moderate.

Was there a tsunami?

USGS did not set a tsunami flag for this quake. If you are on a coast and feel strong or long shaking, move to high ground anyway, and follow local officials.

Was the earthquake felt?

USGS had no felt reports when this page was updated. That is common for offshore and remote quakes. If you felt it, you can report it on the USGS event page.

Will there be more aftershocks?

Aftershocks are likely to continue for days to weeks, becoming less frequent over time. So far 0 aftershocks of M2.5+ have been listed. Most sequences do not produce a larger quake, but some do. No one can predict the time or size of the next one; follow EMSC (European-Mediterranean Seismological Centre).

What should I do after a strong earthquake?

Expect aftershocks: Drop, Cover and Hold On when shaking starts again. Check for injuries and damage, stay out of damaged buildings, and use text messages instead of calls so emergency lines stay free. On a coast, move to high ground after strong shaking. Follow your local officials.

Related live pages

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Sources

USGS event page: magnitude, location, ShakeMap, PAGER and Did You Feel It? data for this event. Public domain. Credit: U.S. Geological Survey.
USGS ComCat (FDSN event web service): the USGS earthquake catalog, used for the 30-year counts, history and aftershocks. Public domain. Credit: U.S. Geological Survey.
USGS Geoserve: nearest places to the epicentre.
GeoNames: large-city coordinates, CC BY 4.0.

Page built 09:06 UTC, 2026-10-29. Full list: data sources and method.