Reviewed by USGSGuam18y ago
M4.2 earthquake 141 km W of Umatac Village, Guam
Tuesday, May 20, 2008, 19:41:52 UTC · 13.092°N, 143.372°E
A magnitude 4.2 earthquake struck 141 km W of Umatac Village, Guam on Tuesday, May 20, 2008, 19:41:52 UTC, at a depth of 205.5 km (intermediate).
- Magnitude
- 4.2
- Light · mb
- Depth
- 206 km
- Intermediate
- 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
28 km
from the nearest mapped plate boundary, between the Philippine Sea and Mariana plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: intermediate
206 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.1 on May 24, 2008. 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 561 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.832 km S of Inarajan Village, GuamAugust 8, 1993 · 155 km E of this epicenter
- 7.2265 km S of Merizo Village, GuamJanuary 28, 1931 · 274 km SE of this epicenter
- 7.1261 km S of Merizo Village, GuamMay 9, 1917 · 267 km SE of this epicenter
- 7.120 km SSW of Merizo Village, GuamApril 26, 2002 · 135 km E of this epicenter
- 7.098 km SSE of Inarajan Village, GuamDecember 9, 1909 · 187 km SE of this epicenter
- 7.032 km NNE of Yigo Village, GuamOctober 26, 1912 · 189 km NE of this epicenter
- 7.069 km SSE of Inarajan Village, GuamOctober 12, 2001 · 180 km E of this epicenter
- 6.8181 km WSW of Merizo Village, GuamMay 9, 2008 · 67 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1993M7.8
Tuman Bay, Apra Harbor
8 Aug 1993 · 155 km away · intensity IX
$250 million damagetsunami
- 1849M7.5
Guam
25 Jan 1849 · 101 km away · intensity IX
Severe damage ($5–24M)tsunami
- 1909M8.0
Guam
9 Dec 1909 · 188 km away · intensity VIII
Moderate damage ($1–5M)tsunami
- 1892M7.5
Guam
16 May 1892 · 101 km away · intensity VIII
Moderate damage ($1–5M)tsunami
- 2001M7.0
Guam
12 Oct 2001 · 180 km away · intensity VIII
Moderate damage ($1–5M)
- 1825
Ladrones Island
Apr 1825 · 101 km away · intensity VIII
Moderate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.