M6.9 earthquake south of the Mariana Islands

Sunday, September 30, 2007, 02:08:30 UTC · 10.454°N, 145.718°E

A magnitude 6.9 earthquake struck south of the Mariana Islands on Sunday, September 30, 2007, 02:08:30 UTC, at a depth of 14.0 km (shallow). USGS received 36 “Did You Feel It?” reports, with a maximum reported intensity of IV (light). It is the strongest earthquake within 300 km since an M7.0 on October 12, 2001.

Magnitude: 6.9; Strong · mwb
Depth: 14 km; Shallow
Felt reports: 36; Max intensity IV
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 100 km aftershock search area

In context

How big was it, and why here?

Energy released

338 kilotons of TNT

That is about 22 times the Hiroshima bomb. It released about 708 times the energy of a magnitude 5.0.

Tectonic setting

208 km

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

Depth: shallow

14 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
96929<br>0.262	III · Weak	9	356 km
96913<br>0.269	IV · Light	8	349 km
96910<br>0.293	IV · Light	5	350 km
96915<br>0.302	III · Weak	4	345 km
96950<br>0.330	II · Weak	1	504 km

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 26 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.5 on September 30, 2007. 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 184 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 3 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 · 298 km away · intensity IX
$250 million damagetsunami
1909M8.0
Guam
9 Dec 1909 · 241 km away · intensity VIII
Moderate damage ($1–5M)tsunami
2001M7.0
Guam
12 Oct 2001 · 261 km away · intensity VIII
Moderate damage ($1–5M)

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

Nearby trackers