December 9, 1909 Tsunami: Guam, Mariana Islands, US Territories
A tsunami caused by a magnitude 8 earthquake began at Guam, Mariana Islands, US Territories on December 9, 1909 at 23:28 UTC. Its effects were recorded at 1 place.
Where the waves reached
The source (white) and every runup with a place, colored by the water height recorded there. A ring is a runup NCEI marks doubtful.
- Under 1 m
- 1 to 3 m
- 3 to 10 m
- 10 to 30 m
- 30 m and more
- Height not recorded
The tsunami
- Date
- December 9, 1909, 23:28 UTC
- Source
- Guam, Mariana Islands, US Territories
- Cause
- Earthquake
- Earthquake
- Magnitude 8, 100 km deep
- Runups recorded
- 1
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 12.500° N, 145.000° E
The toll
- Damage
- Moderate (about $1 to $5 million) with the earthquake or eruption that caused it
Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.
What the record says
NCEI’s account, from the sources it cites.
At 9 a.m. on December 10th there were two shocks lasting twenty seconds of which the second was the more severe. Direction of the shocks SE-NW. The river bed sank in several places. The passing wave could been distinctly as it crossed the plaza, and the station ship in the harbor reported having felt the shock. (reference #2519)
Every runup
Nearest the source first. Heights are above sea level at the time; a tide gauge reads half the wave’s full height.
| Where | Country | Km from source | Water height, m | Inland, m | Measured by | First wave, UTC | Deaths |
|---|---|---|---|---|---|---|---|
| Agana Harbor, Guam, GU | US Territories | 112 | Eyewitness observation of water height |
More
Every tsunami in 1909The 1900sTsunamis of US TerritoriesThe earthquakeThis day in weather historyAlerts in force
Sources
Tsunami events and runups from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-09-24. NCEI tsunami event 1386.