Moderate magnitude 4.7 earthquake at unknown depth17 Aug 02:12 UTC: First to report: USGS after 18 minutes.I didn't feel itI felt this quakeEarthquake detailsDate & timeAug 17, 2025 01:54:09 UTC - Local time at epicenterSunday, Aug 17, 2025, at 12:54 am (GMT -1)Statusconfirmed (manually revised)Magnitude4.7Depth10 kmEpicenter latitude / longitude48.9545°S / 8.8305°WSt. HelenaSeismic antipode48.9545°N / 171.1695°EQuality18 seismic stationsShaking intensityV Moderate shaking near epicenterFelt0 reportsPrimary data sourceUSGS (United States Geological Survey)Weather at epicenter at time of quakeOvercast Clouds -1°C (30 F), humidity: 82%, wind: 15 m/s (30 kts) from SWEstimated seismic energy released7.1 x 1011 joules (197 megawatt hours, equivalent to 169 tons of TNT) | equivalent to ONE quake of magnitude 4.7 | about seismic energy35 minutes agoAug 17, 2025 01:54 GMT / Aug 17, 2025 12:54 am (GMT -1)Lat / Lng: -48.9545 / -8.8305: Southern Mid-Atlantic RidgeSource: USGSOther sources: IRIS: 4.7 / 10 kmDetail info | You felt it? - Report it!';storedMarkers.push(['quake-22064702',-48.95450,-8.83050,'35 minutes ago: Mag. 4.7, Southern Mid-Atlantic Ridge',html,'quakes-6-24.png',25,25,12,12,125]); function mkRep(id,notFelt){var nFelt=notFelt||false;var src="https://www.volcanoesandearthquakes.com/app/earthquake-report.php?quakeId="+id;if(nFelt==true){src+="¬Felt=true";}window.open(src,"","status=0,toolbar=0,location=0,directories=0,menubar=0,resizable=1,scrollbars=1,height=400,width=350");} function locationHashChanged(e){-1!=e.oldURL.indexOf("#popupMap")&&closePopup()} window.onhashchange = locationHashChanged; function comment(e){var t=e.parentNode,a=(t.dataset.id,document.getElementById("commentForm"));"none"==a.style.display?(t.appendChild(a),a.style.display="block"):a.style.display="none"}function sendComment(e){var t=e.parentNode,a=t.parentNode.dataset.id,n=document.getElementById("commentContent"),p=n.value.trim();if(p){var o="id="+a+"&quakeId="+thisQuakeId;o+="&comment="+decodeURIComponent(p),mkRequest("//reports.volcanodiscovery.com/app/eqReportComment.php","post",o,function(e){e.responseText;alert("Thank you for submitting your comment!"),t.style.display="none",n.value=""})}}function flagReport(e){var t=e.parentNode.dataset.id;if(confirm("Report this as inappropriate?")){var a="id="+t+"&quakeId="+thisQuakeId+"&flagAsInappropriate=1";mkRequest("//reports.volcanodiscovery.com/app/eqReportComment.php","post",a,function(t){var a=t.responseText;alert(a),e.style.display="none"})}}function likeReport(e){var t="id="+e.parentNode.dataset.id+"&quakeId="+thisQuakeId+"&like=1";mkRequest("//reports.volcanodiscovery.com/app/eqReportComment.php","post",t,function(t){t.responseText;e.style.opacity=.5})}]]>[smaller] [bigger]Most recent quakes Top 20 past 24 hrsNearby placesUser-reports for this quakeThere are no user reports for this quake yet.If you felt it, be the first to report it!Compare Quake DataData for the same earthquake as reported by different agenciesThe more agencies report about the same quake and post similar data, the more confidence you can have in the data. It takes normally up to a few hours until earthquake parameters are calculated with near-optimum precision.MagDepthTime GMT2025-08-17EpicenterAgency4.7± 0.1310 km6.2 mi(*)±1.9 km01:54:09.168southern Mid-Atlantic RidgeEpicenter uncertainty: ± 15 kmUSGS (United States Geological Survey)4.710 km6.2 mi(*)01:54:09southern mid-atlantic ridge0 km (0 mi) epicenter difference with USGSIRIS (Incorporated Research Institutions for Seismology)Notes:(*) A depth given as 10 km often means that the the depth of the quake could be not determined with sufficient accuracy.Aftershocks for this quakeNo aftershocks have been recorded so far. When aftershocks are detected, we will update this section.What are aftershocks?Larger earthquakes (above magnitude 5 or so) such as this one are usually followed by smaller ones known as aftershocks that occur in the same area during the days, weeks, months or even years after the main shock.[More info]What about this quake?Based on its magnitude, the fault that was active during the quake likely ruptured beneath a surface area of approximately 5 km2 (2 square miles) as a first-order estimate. The length of the rupture zone thus was probably around 4 km (2 mi).[More info]Recorded aftershocks, latest first (0 quake)Aug 17, 2025 12:54 am (GMT -1)35 minutes ago4.710 km0 km - This quakeSouthern Mid-Atlantic RidgeMain Shock (this quake)MoreMap of aftershocksEarthquake statisticsAverage number of earthquakesBased on data from the past 55 years and our earthquake archive back to 1900, there are about 2.2 quakes on average per year in the area near the epicenter of this quake (within 100 km/61 mi):Mag. 5 or higher: 0.36 quakes per year (or 1 quake every 2.8 years)Mag. 4 or higher: 1.96 quakes per yearMag. 3 or higher: 2 quakes per yearMag. 2 or higher: 2 quakes per yearThe area where this quake occurred has a high level of seismic activity. It has had at least 20 quakes above magnitude 5 since 1970, which suggests that larger earthquakes of this size occur infrequently, probably on average approximately every 1 to 5 years.Number of quakes per yearPrevious quakes in the same area of this earthquakeStrongest in 1 year 31 weeksThe earthquake was the strongest to hit this part of Saint Helena in over 1 year 31 weeks. Earlier, the last quake of equal or greater strength near the present epicenter had been a magnitude 5.0 earthquake on Wednesday, Jan 10, 2024, at 01:29 am (GMT -1 local time) in 57 km (35 mi) distance to the southeast:Mag. 5.0 earthquake Southern Mid-Atlantic Ridge - Jan 10, 2024 - The strongest-ever (since 1900) recorded quake in this area measured magnitude 5.8. It had occurred 67 years ago earlier, on Saturday, Aug 9, 1958, at 11:47 am (GMT -1 local time) in South Atlantic Ocean, Bouvet Island:Mag. 5.8 earthquake Southern Mid-Atlantic Ridge - Aug 9, 1958 - Below is a list and map of larger or recent quakes that had occurred near the epicenter before this earthquake (within up to 100 km/61 mi distance, up to 300 km/183 mi for very large quakes above mag. 7). Filter and sort the list by magnitude or time.Max results102050100AllMagnitudeAll2+3+4+5+6+7+8+Time before48 hours1 week30 days1 year5 years30 yearsAny ageDate and TimeMagDepthDistanceLocationDetailsMapApr 8, 2024 07:43 am (GMT -1)4.510 km47 km (29 mi) to the E Southern Mid-Atlantic RidgeInfoJan 10, 2024 01:29 am (GMT -1)5.010 km57 km (35 mi) to the SE Southern Mid-Atlantic RidgeInfoNov 21, 2023 09:53 am (GMT -1)4.610 km41 km (26 mi) to the SESouthern Mid-Atlantic RidgeInfoJan 21, 2023 08:56 pm (GMT -1)4.810 km25 km (16 mi) to the E Southern Mid-Atlantic RidgeInfoDec 23, 2022 08:53 am (GMT -1)4.910 km55 km (34 mi) to the SE Southern Mid-Atlantic RidgeInfoOct 29, 2022 10:23 pm (GMT -1)4.710 km87 km (54 mi) to the SE Southern Mid-Atlantic RidgeInfoOct 22, 2021 01:09 am (GMT -1)4.710 km8 km (4.9 mi) to the S Southern Mid Atlantic RidgeInfoOct 18, 2021 08:28 pm (GMT -1)4.910 km24 km (15 mi) to the E Southern Mid-Atlantic RidgeInfoMay 21, 2021 02:17 pm (GMT -1)5.110 km83 km (52 mi) to the SW Southern Mid-Atlantic RidgeInfoMar 5, 2020 01:58 pm (GMT -1)5.110 km15 km (9.3 mi) to the N Southern Mid Atlantic RidgeInfoAug 26, 2019 10:11 pm (GMT -1)4.910 km47 km (29 mi) to the SE Southern Mid-Atlantic RidgeInfoMay 30, 2016 06:35 am (GMT -1)5.210 km79 km (49 mi) to the SE Southern Mid Atlantic RidgeInfoAug 2, 2015 04:29 am (GMT -1)5.110 km100 km (62 mi) to the NW Southern Mid-Atlantic RidgeInfoFeb 1, 2015 07:02 pm (GMT -1)5.610 km74 km (46 mi) to the SE Southern Mid Atlantic RidgeInfoNov 4, 2014 03:58 pm (GMT -1)4.915 km22 km (14 mi) to the SW Southern Mid-Atlantic RidgeInfoJul 4, 2014 04:34 am (GMT -1)5.110 km43 km (27 mi) to the SE Southern Mid-Atlantic RidgeInfoOct 28, 2013 10:52 pm (GMT -1)5.032 km46 km (28 mi) to the SE Southern Mid-Atlantic RidgeInfoAug 4, 2013 12:28 am (GMT -1)5.410 km13 km (8.3 mi) to the E Southern Mid-Atlantic Ridge 1 reportInfoNov 8, 2009 12:52 pm (GMT -1)4.810 km80 km (50 mi) to the W Southern Mid-Atlantic RidgeInfoJul 10, 2009 07:00 pm (GMT -1)4.810 km36 km (22 mi) to the E Southern Mid-Atlantic RidgeInfoJul 3, 2009 06:01 pm (GMT -1)4.910 km93 km (58 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 11, 2009 09:23 am (GMT -1)4.810 km59 km (37 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 20, 2006 03:50 pm (GMT -1)5.210 km79 km (49 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 20, 2006 02:58 pm (GMT -1)5.210 km89 km (55 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 20, 2006 02:12 pm (GMT -1)5.310 km76 km (47 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 20, 2006 01:59 pm (GMT -1)5.110 km74 km (46 mi) to the SE Southern Mid-Atlantic RidgeInfoApr 20, 2006 01:31 pm (GMT -1)5.010 km84 km (52 mi) to the SE Southern Mid-Atlantic RidgeInfoFeb 25, 2005 04:11 am (GMT -1)5.010 km22 km (14 mi) to the NE Southern Mid-Atlantic RidgeInfoFeb 27, 1999 11:55 am (GMT -1)5.610 km74 km (46 mi) to the SE Southern Mid-Atlantic RidgeInfoMay 10, 1993 02:54 pm (GMT -1)5.210 km95 km (59 mi) to the SE Southern Mid-Atlantic RidgeInfoNov 1, 1992 06:51 am (GMT -1)5.310 km25 km (15 mi) to the NE Southern Mid-Atlantic RidgeInfoSep 18, 1985 11:21 pm (GMT -1)5.510 km77 km (48 mi) to the SE Southern Mid-Atlantic RidgeInfoSep 18, 1985 11:04 pm (GMT -1)5.110 km66 km (41 mi) to the SE Southern Mid-Atlantic RidgeInfoAug 9, 1958 11:47 am (GMT -1)5.815 km82 km (51 mi) to the S Southern Mid-Atlantic RidgeInfoApr 23, 1956 07:27 am (GMT -1)5.815 km76 km (47 mi) to the W Southern Mid-Atlantic RidgeInfoMap of earlier quakes in the area of this quakeMax results102050100AllMagnitudeAll2+3+4+5+6+7+8+Time before48 hours1 week30 days1 year5 years30 yearsAny ageOldest quakes are shown in yellow, most recent in red.[quakes -][quakes +][smaller][bigger]