The Chilean Tsunami of 1960
Figure 1.  How an earthquake in a subduction zone creates a tsunami
Figure 1. How an earthquake in a subduction zone creates a tsunami


On May 22, 1960 a 9.5 magnitude earthquake occured around 14:11 in the South American country Chile near the coast line. The earthquake occured by way of a strike-slip fault that was created by the action of the Nazca Plate being subducted under the South American Plate with the depth of the focus at 33km. The earthquake's rupture length was 1000 km long and 200 km wide. It was to be the highest recorded magnitude of any earthquake in history. The earthquake's sheer magnitude triggered a series of disasters that would go on to affect many parts of the globe as the time went on. Tsunamis were quickly formed after the initial earthquake and would shoot out across the Pacific Ocean as well as along the Chilean coast. Figure 1 shows how exactly a tsunami is created from energy released by an earthquake. Places like Hawaii, Japan, and the Philippines were just some to have reaped the devastation of the effects of tsunamis. The death toll of both the earthquake and tsunami totals neared 1700 along with 3000 injured and 2 million homeless as reported by the United States Geological Survey. The economic loss in damages world wide totaled over a half billion dollars back then.

Figure 2.  Aerial view of coastal area on Isla Chiloe, Chile
Figure 2. Aerial view of coastal area on Isla Chiloe, Chile

Damage to Chile

The Tsunami arrived only minutes after the earthquake much to the shock of some of the people in Chile. The tsunami raced down the coast line with waves as high as 82 ft destroying nearly everything in its path. Seismic waves killed 52 people alone according to the International Seismological Summary. Figure 2 displays this type of damage near the areas by the coast. The tsunamis created by the earthquake caused more damage in Chile all the way from the cities of Lebu to Puerto Aisen. Flooding at places such as Riñihue Lake and mudslides along the Andes were also triggered by the earthquake and tsunami which caused considerable amounts of damage to surrounding areas. Also a few days after the earthquake on May 24, a sub-plinian eruption style immerged out of the Cordón Calle volcano located near the Andean Valley in Chile.



Damage to Other Parts of the World

The main tsunami created by the earthquake initially shot out across the entire Pacific Ocean. Tsunamis have very long wavelenghts and can travel very far at alarming speeds of hundreds of Km per hour. They move fast in the ocean and can go unnoticed because their wave height is particularly small. Once they reach their destination they are slowed down and increase in height causing catastrophes in other countries. Effects were seen in many places such as: Hawaii, Japan, New Zealand, the Philippines, some of the California coast, and the Aleutian Islands. Figure 3 displays the time in hours that it took for the tsunami to reach parts of the world. Hilo, Hawaii seemed to take on the brunt of the tsunami's force. This is because the positioning of Hilo in accordance with the bay on the part of the main island. That created waves as high as 35ft destroying the city along with killing 61 people and injured 43 who failed to heed the warning sirens. Figure 4 shows the shear force that the tidal waves and flooding brought to Hilo. The waves bent back parking meters and scattered debris such as: automobiles, machinery, and even a ten-pound tracker trailer throughout the city. Sea rock in the amounts of as much as 20 metric tons were also thrown far inland. Every frame building was either crushed or felt the wrath of terrible flooding. Even the buildings that were reinforced with concrete or structural steel were emptied due to the violent waves. It wasn't just the island of Hawaii that was affected by tsunamis, Maui also had houses, offices, and even a church damaged and destroyed by tidal waves. Japan also felt the wrath of the tsunami in similar fashion with waves almost as high as the ones in Hilo, but with a higher death toll at 199 mostly due to flooding. Figure 5 shows this flooding in Japan first hand. The western coast of the United States in places like Crescent City California even were affected. In California, places like harbors suffered the losses of several boats that were either sunk, set to sea, or misplaced that in turn damaged piers and bridges in Los Angeles and Long Beach.
Figure 3. Tsunami travel time from focus
Figure 3. Tsunami travel time from focus
Figure 5. Flooding in Japan due to Tsunami
Figure 5. Flooding in Japan due to Tsunami
Figure 4.   Damage cause by tsunami in Hilo
Figure 4. Damage cause by tsunami in Hilo

Chile's Past History of Earthquakes

Before the 1960's great 9.5 magnitude earthquake, Chile experienced a quake with similar size in its subduction zone in the year 1575. The years to come also bought Chile earthquakes near 8.0 magnitude earthquakes in the years 1737 and 1837 on the same fault. The 1960 9.5 magnitude earthquake came as a surprise to most geologists seeing as Chile had those earthquakes thought to be near magnitude 8 in between the years after the giant earthquake in 1575. It was a surprise mostly because for an earthquake of a 9.0 or greater magnitude, the stress caused by subduction must be built up over several hundred years and not just a period over 123 years since the earthquake in 1837. This past cycle of earthquakes is was keeps scientists asking questions and trying to create a successful way of predicting when the looming big earthquake is going to hit.






Sources:
http://earthquake.usgs.gov/earthquakes/world/events/1960_05_22_articles.php
http://www.geophys.washington.edu/tsunami/general/historic/chilean60.html
http://pubs.usgs.gov/circ/c1187/
http://bcs.whfreeman.com/earthquakes/content/cat_490/bt00eh05.htm#Chile,%201960
http://news.nationalgeographic.com/news/2005/09/0915_050915_earthquake.html
http://www.geotimes.org/nov05/NN_ChileEQ.html