December 4, 1918 Earthquake: Copiapo, Chile

December 4, 1918, 11:47.8 UTC, 26 S 71 W, magnitude 7.75 MS. Weak oscillations rapidly gaining strength began at Copiapo. The tremors lasted 3-6 minutes. There was no rumbling. Damage to the city was heavy; 21% of the homes were completely destroyed, and 31% were seriously damaged. The remaining 944 homes suffered comparatively little, but not one home in the city remained undamaged. The destruction was increased by the fact that the residential district of the city, situated on the alluvial loams of the Copiapo River, was built up mainly with old, dilapidated homes of the pise or wood cottages type with heavy flat roofs (25%), adobe homes with very flimsy mortar (25%), covered frame houses (25%), and reed panel homes (25%). It was mainly homes of the first and to some extent, of the second type, especially those situated on the weakest soils, which suffered. Numerous cracks up to 100 m long formed in the ground [8 degrees].

Near Copiapo, at Potrero-Seco, moderate damage was done to flimsy houses [6-7]. A collapse occurred near Punta Colorado, blocking the railway [7]. At Pugios, not a single home escaped some damage (it was mainly pise houses which were damaged); small cracks formed in the ground [7]. At San Antonio and Loroz, some homes were destroyed and many were damaged; several irrigation canals were completely destroyed [7-8]. At Tres-Puentes, numerous avalanches blocked the highway [8]. At Vallenar, walls cracked in some buildings [6-7]. A strong earthquake felt at Pueblo Undido and Tierra Amarilla.

The earthquake was preceded by two foreshocks and was followed by aftershocks.

At Caldera, the earthquake also lasted about 6 minutes. It was difficult to walk. The railway pier suffered damage. The cross was knocked off the church and shop windows were broken. Small cracks opened up in the ground near the beach. There was no other damage to the city, which was built up mainly with wooden homes [6-7].

[NOTE: numbers in brackets are intensities].

After the earthquake, the sea slowly retreated from shore and the passenger quay dried up completely. Then, just as slowly, the sea flooded the beach.

(above from reference #415)

December 4, 1918, 11:47:48 UTC, 26 S, 71 W, shallow depth, magnitude 7.75 MS. (reference #88)

December 4, 1918, 11:47.8 UTC, 26 S, 71 W, magnitude 7.75 MS. (reference #130)

December 4, 1918, 11:47:48 UTC, 26 S, 71 W, magnitude 7.8 MS, tsunami, casualties. (reference #1206)

December 4, 1918, 11:47.8 UTC, 26 S, 71 W, magnitude 7.75 MS. (reference #1092)

Damage was estimated to exceed 5 million pesos of the time, an amount quite similar to that of 1922 [earthquake]. (reference #14085)