A magnitude 4.9 earthquake struck the Tibetan Plateau on Oct. 24 at 00:07 UTC, the latest in a run of shocks that began with a magnitude 7.0 on Oct. 22. The U.S. Geological Survey located it 209 kilometers east-northeast of Nagqu, China, at a depth of 10 kilometers, and listed it as a reviewed event with no alert level. In China the clock read 08:07 that morning.
Help yourself and the planet: The Cool Down makes it easy to help yourself while helping the planet, with smart, simple changes to save more and waste less in your everyday life.
We may earn a commission if you sign up.
Nagqu is the landmark in USGS’s place name, not the epicenter. Every shock in this sequence lies roughly 190 to 235 kilometers from it, to the east-northeast or northeast, in a thinly populated stretch of the plateau. Four of the 22 earthquakes of magnitude 4.5 or larger that USGS listed worldwide from the start of Oct. 23 through early Oct. 24 carried that same Nagqu label.
The 4.9 on Oct. 24
The USGS record for the 4.9 gives a body-wave magnitude (mb), coordinates of 32.53 degrees north and 93.90 degrees east, and a depth of 10 kilometers that the analyst assigned rather than computed. No one had filed a felt report when the record was read, and USGS had attached no alert. Its last update came at 00:29 UTC, about 22 minutes after the shaking, and the record is marked reviewed.
A depth assigned by the analyst means the real figure could differ by several kilometers, and the same caution applies to the other shocks here that carry a depth of exactly 10 kilometers. The 4.9 is also scored on a different scale from the 7.0: the smaller event uses the body-wave scale and the larger one the moment scale, so the two numbers are close cousins rather than identical measures, and the gap of 2.1 units between them corresponds to roughly a thousandfold difference in energy released.
A magnitude 7.0 that started the sequence
The largest shock came on Oct. 22 at 14:33:40 UTC. The USGS event page for the 7.0 lists a moment magnitude of 7.0, a depth of 18 kilometers, a position 191 kilometers east-northeast of Nagqu at 32.38 degrees north and 93.78 degrees east, and an orange PAGER alert. USGS’s automated impact estimate says shaking impacts are likely, some fatalities are possible and the disaster could be widespread. About 111,000 people were estimated to have felt moderate to severe shaking, from intensity V to intensity VIII, and eight people filed felt reports.
USGS’s tectonic summary says the earthquake resulted from normal faulting within the Tibetan Plateau, on a crustal fault dipping moderately to the northwest or southeast. That fits the east-west extension of the plateau, which the agency ties to the convergence of India and Eurasia. It was the only earthquake of magnitude 6 or larger in USGS’s list of events of magnitude 4.8 and above for Oct. 22 and Oct. 23 anywhere in the world.
The records read do not describe damage or casualties, and none are claimed here. Reports of that kind, if they exist, would come from Chinese authorities and local observers rather than from the USGS magnitude and shaking estimates summarized above.
Shocks of 4.5 to 5.2 in the following hours and days
Within about 40 minutes of the main shock USGS logged a magnitude 5.2 at 15:12 UTC on Oct. 22, 201 kilometers east-northeast of Nagqu, and a magnitude 5.0 followed at 18:06 UTC, 207 kilometers east-northeast. A magnitude 4.9 at 16:21 UTC the same day sits 210 kilometers east-northeast. All of them carry the same depth of 10 kilometers as the latest event, and none drew an alert.
On Oct. 23 the activity continued at a lower level. A magnitude 4.7 struck at 14:14 UTC, 215 kilometers northeast of Nagqu, and a magnitude 4.5 followed at 14:41 UTC, 233 kilometers east-northeast. A magnitude 4.8 at 20:37 UTC, 209 kilometers east-northeast, was the largest of that day, and the 4.9 on Oct. 24 arrived 3 hours and 30 minutes after it.
Counting the 7.0, the 5.2, the 5.0 and the 4.9 on Oct. 22, the three shocks of Oct. 23 and the 4.9 on Oct. 24, USGS’s lists show at least eight events of magnitude 4.5 or larger near Nagqu in about 34 hours. Smaller shocks fall below the cutoff of those lists, so the true total is higher, and USGS also lists a magnitude 4.9 at 15:45 UTC on Oct. 22 labeled only “western Xizang,” which the label alone does not tie to this sequence.
The sizes do not fall in a straight line. The largest aftershock-range event of Oct. 22 was the 5.2, the largest of Oct. 23 was the 4.8, and the 4.9 that arrived after midnight UTC on Oct. 24 was a step back up from that day, even though it stayed below the Oct. 22 shocks. The lists USGS published show activity still continuing about 34 hours after the 7.0.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
Help yourself and the planet: Get The Cool Down →
We may earn a commission if you sign up.
More from Morning Overview
- The NSA says three phone features should be off whenever you aren’t using them
- Hurricane Hunter radar shows four warning signs that a tropical cyclone is about to strengthen, a University of Miami study found
- Tropical Storm Rachel is dumping up to 12 inches on four Mexican states on its way to major hurricane strength
- The FTC says Lens.com doubled the price shoppers saw in Google ads
