Reviewed by USGSChina50y ago
M6.4 earthquake 99 km NNW of Jiangyou, China
Saturday, August 21, 1976, 21:49:54 UTC · 32.571°N, 104.249°E
A magnitude 6.4 earthquake struck 99 km NNW of Jiangyou, China on Saturday, August 21, 1976, 21:49:54 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M6.9 on August 16, 1976.
- Magnitude
- 6.4
- Strong · ms
- Depth
- 33 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
60 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 126 times the energy of a magnitude 5.0.
Tectonic setting
411 km
from the nearest mapped plate boundary, between the Eurasian and Yangtze plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
33 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 100 km
USGS lists 4 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M6.7 on August 23, 1976. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 31 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.4101 km WNW of Jiangyou, ChinaAugust 25, 1933 · 87 km SW of this epicenter
- 6.9121 km NNW of Jiangyou, ChinaAugust 16, 1976 · 22 km NW of this epicenter
- 6.5128 km NNW of Kangding, ChinaMay 29, 1919 · 298 km SW of this epicenter
- 6.3146 km NW of Jiangyou, ChinaNovember 9, 1960 · 60 km W of this epicenter
- 6.2Qinghai-Sichuan border region, ChinaOctober 31, 1952 · 297 km W of this epicenter
- 6.261 km S of Tianshui, ChinaAugust 1, 1936 · 213 km NE of this epicenter
- 6.1127 km WNW of Jiangyou, ChinaMarch 14, 1938 · 87 km SW of this epicenter
- 6.1151 km NNW of Jiangyou, ChinaAugust 11, 1973 · 52 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 22 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 107,115 recorded deaths. The most severe:
- 1718M7.5
Gansu Province
19 Jun 1718 · 284 km away · intensity X
73,000 deathsExtreme damage ($25M+)
- 1879M8.0
Gansu Province
1 Jul 1879 · 82 km away · intensity XI
22,000 deathsExtreme damage ($25M+)
- 1933M7.4
Sichuan Province
25 Aug 1933 · 87 km away · intensity X
9,300 deathsExtreme damage ($25M+)
- 1765M6.5
Gansu Province: Wushan, Gangu
2 Sep 1765 · 257 km away · intensity IX
2,068 deathsExtreme damage ($25M+)
- 1881M6.5
Gansu Province
20 Jul 1881 · 119 km away · intensity VIII
480 deathsSevere damage ($5–24M)
- 1936M6.0
Gansu Province
1 Aug 1936 · 226 km away · intensity VIII
115 deathsSevere damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.