May 4, 1820 Tsunami: S. Mexico
A tsunami caused by a magnitude 7.6 earthquake began at S. Mexico on May 4, 1820. The water rose as high as 4 meters. 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
- May 4, 1820
- Source
- S. Mexico
- Cause
- Earthquake
- Earthquake
- Magnitude 7.6
- Maximum water height
- 4 m (13.1 ft)
- Runups recorded
- 1
- Tsunami intensity (Soloviev-Imamura)
- 1.5
- Tsunami magnitude (Iida)
- 1
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 17.200° N, 99.600° W
The toll
- Damage
- Severe (about $5 to $25 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.
On May 4 (mistakenly l0), 1820, at 14:30 [local time] there was a large earthquake on the western coast of Mexico. The source of the earthquake apparently lay off Acapulco and San Marcos.
A tsunami arose. At Acapulco, the sea retreated to the middle of the bay, exposing the reefs. Alternate quiet flood and ebb tides were observed with some pauses in the movement of water on reaching the highest and lowest levels. Two hours later, the flood tide was so large, that the water reached the doors of the church situated in the highest part of the city square. The square was flooded. The ocean advanced inland like a wall and with great speed, sweeping away everything in its path. Then, in a strong ebb tide, stronger than in 1787 [?], the greater part of the bottom of the bay was laid bare. After this, the sea level began gradually to return to its normal state. After the tsunami, the breakwater was totally covered with sand for 1 1/2-2 m (5-6 feet), while the beach had expanded by 17 m (20 vara).
There is also an account by the master of Acapulco port. "Yesterday at 14:00, a strong earthquake occurred in the port. It lasted 5 minutes; it recurred in the next quarter of an hour, and was followed by other shocks, not so prolonged. All this terrified and depressed the
inhabitants .... After the horrors of the earthquake, there began movements of the sea in the form of an unusual flood and ebb tide, the first (along the horizontal) from 40 to 50 m (from 60 to 60 vara), and the second approximately
from 15 to 20 m (from 20 t o 25 vara). One of the two ships, which was taking on provisions in the harbor, was forced to retreat out to the bay for safety".
(above from reference #415)
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 |
|---|---|---|---|---|---|---|---|
| Acapulco | Mexico | 53 | 4 | Eyewitness observation of water height | day 5, 05:00 |
More
Every tsunami in 1820The 1800sTsunamis of MexicoThe 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 633.