M4.2 earthquake 291 km SSW of Laojunmiao, China

Saturday, September 5, 2009, 08:59:20 UTC · 37.644°N, 95.883°E

A magnitude 4.2 earthquake struck 291 km SSW of Laojunmiao, China on Saturday, September 5, 2009, 08:59:20 UTC, at a depth of 10.0 km (shallow).

Magnitude: 4.2; Light · mb
Depth: 10 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

30 tons of TNT

That is about 1/500 of the Hiroshima bomb. A magnitude 5.0 releases about 16 times more energy.

Tectonic setting

1,047 km

from the nearest mapped plate boundary, between the Eurasian and Indian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

10 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 50 km

USGS lists 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.1 on September 18, 2009. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 83 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 277 recorded deaths. The most severe:

1932M7.6
Gansu Province
25 Dec 1932 · 239 km away · intensity X
275 deathsSevere damage ($5–24M)
2002M5.5
Gansu Province: Yumne
14 Dec 2002 · 269 km away
2 deathsSevere damage ($5–24M)
2004M5.4
Qinghai Province: Delingha
4 May 2004 · 79 km away
Severe damage ($5–24M)
2008M6.3
Qinghai Province
10 Nov 2008 · 10 km away
$4 million damage
1937M7.5
Qinghai Province
7 Jan 1937 · 283 km away · intensity X
Limited damage (under $1M)
1963M7.0
Qinghai Province
19 Apr 1963 · 238 km away · intensity VIII
Limited damage (under $1M)

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers