1922 Vallenar earthquake

Tectonic setting

The earthquake took place along the boundary between the Nazca and South American tectonic plates, at a location where they converge at a rate of seventy millimeters a year.

Chile has been at a convergent plate boundary that generates megathrust earthquakes since the Paleozoic (500 million years ago). In historical times the Chilean coast has suffered many megathrust earthquakes along this plate boundary, including the strongest earthquake ever measured. Most recently, the boundary ruptured in 2010 in central Chile.

Damage and deaths

The earthquake caused extensive damage in a zone extending approximately from Copiapó to Coquimbo. Newspapers estimated more than 1,000 dead as a result of the quake, at least 500 of them in Vallenar. The tsunami killed several hundred people in coastal cities, especially in Coquimbo.

Total damage was estimated to be in the range of $5–25 million U.S. (1922 dollars).

Characteristics

Earthquake

The earthquake was preceded by strong foreshocks on 3 and 7 November. The main shock lasted between thirty seconds and eight minutes according to various reports. A maximum Mercalli-Sieberg intensity was XI assigned in Vallenar and the surrounding region was assigned X. Shaking intensity decreased further west towards the coast, ranging from VII to IX. The location closest to the tsunami source, Caldera, was assigned VII. This suggest an inland earthquake source.

A 2019 study in Geophysical Journal International suggested the earthquake ruptured the subduction zone interface. The tsunami triggered by the mainshock was large and corresponded with a tsunami magnitude () of 8.7. Estimates of the moment magnitude range from 8.3 to 8.6. The length of the plate boundary that ruptured during the earthquake is estimated to be 300 to.

Tsunami

The epicenter of the earthquake was well inland and the tsunami may have been caused by a submarine slide triggered by the shaking.

At Caldera the tsunami began about 15 minutes after the earthquake, with a maximum run-up height of 7 m (23 ft). At Chañaral the tsunami had three surges, the first about an hour after the earthquake, the maximum run-up height was 9 m (30 ft). Three surges were also seen at Coquimbo, the last being the most destructive with a maximum run-up of 7 m (23 ft).

The tsunami was also observed in Callao, Peru (2.4 m, 7.9 ft), California (0.2 m, 8 in 13.0 hours delay), Hawaii (2.1 m, 6.9 ft 14.5 hours), Samoa (0.9 m, 3 ft 14.1 hours), Japan (0.3 m, 1 ft), Taiwan (0.03 m, 1 in), New Zealand (0.1 m, 3.9 in), Australia (0.2 m, 7.9 in) and the Philippines (0.1 m, 3.9 in).

References

References

1. Seismological Notes, Bulletin of the Seismological Society of America. "Seismological Notes" is a list of recent important earthquakes with short summaries included in each issue of the BSSA.
2. (14 December 2016). "Reexamination of the magnitudes for the 1906 and 1922 Chilean earthquakes using Japanese tsunami amplitudes: Implications for source depth constraints". Journal of Geophysical Research.
3. (1979). "Size of great earthquakes of 1837–1974 inferred from tsunami data". Journal of Geophysical Research.
4. (6 March 2010). "Magnitude 8.8 – OFFSHORE MAULE, CHILE". United States Geological Survey.
5. "Thousands Die in Earthquake." Tulsa (OK) World, 13 November 1922, p. 1.
6. [https://web.archive.org/web/20131020022854/https://earthquake.usgs.gov/earthquakes/world/events/1922_11_11.php USGS, ''Historic Earthquakes.Chile-Argentina Border. 1922 November 11 04:32 UTC. Magnitude 8.5'']
7. Dunbar, Paula K., Lockridge, Patricia A., and Whiteside, Lowell S., 1992, Catalog of significant earthquakes 2150 B.C. – 1991 A.D.: U. S. Dept. of Commerce, National Oceanic and Atmospheric Administration.
8. (1939). "Tsunamis and earthquakes". Bulletin of the Seismological Society of America.
9. (2019). "New constraints on the 1922 Atacama, Chile, earthquake from Historical seismograms". Geophysical Journal International.
10. SHOA (Servicio de Hidrográfico y Oceanográfico). "Tsunamis registrados en la costa de Chile".
11. Gutenberg, B.. (1939). "Tsunamis and earthquakes". Bulletin of the Seismological Society of America.
12. (1922). "Effect on Australian Tides". The Sydney Morning Herald.
13. NGDC. "Comments for 1922 tsunami".