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Chilean Earthquake
by Vanessa Braggs
Physical Geology
Fall 2015
  
 

                           
 

The Great Chilean Earthquake of 1960
 

            On May 22, 1960 at 7:11 pm the largest earthquake recorded in earth’s history occurred near the town of Valdivia, in southern Chile. “The Great Chilean Earthquake” as it is sometimes referred to, had a magnitude of 9.5, causing substantial damage and loss of life not only in Chile but also in many areas of the Pacific Ocean. For a better understanding of the extensive damages caused by “The Great Chilean Earthquake,” it is important to explain and discuss what is an earthquake, what causes earthquakes, and earthquakes in Chile, as well as the effects and devastation caused by The Great Chilean Earthquake of 1960.
 

What is an earthquake? An earthquake is what happens when two blocks of the earth (tectonic plates) suddenly slip past one another. The surface where they slip is called the fault. Sometimes an earthquake has foreshocks which are smaller earthquakes that happen in the same place as the larger earthquake that follows. Unfortunately, scientists cannot tell that an earthquake is a foreshock until the larger earthquake happens. The largest, main earthquake is called the main shock. Main shocks always have aftershocks that follow, which are smaller earthquakes that occur afterwards in the same place as the main shock. Depending on the size of the main shock, aftershocks can continue for weeks, months, and even years after the main shock.
 

What causes earthquakes? The earth has four major layers: the inner core, outer core, mantle, and crust. The crust and the top of the mantle make up a thin skin on the surface of our planet. But this skin is not all in one piece; it is made up of many pieces like a puzzle covering the surface of the earth.
 

https://msnucleus.org/membership/html/k-6/pt/plate/6/images/plate2.gif

                                         Figure 1. This picture represents the world’s tectonic plates and fault lines    
                                                                             (http://earthquake.usgs.gov/learn/kids/eqscience.php)
 

 

These puzzle pieces keep slowly moving around, sliding past one another and bumping into each other. These puzzle pieces are called tectonic plates, and the edges of the plates are called the plate boundaries. The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults. Since the edges of the plates are rough, they get stuck while the rest of the plates keeps moving (The Science of Earthquakes). Finally, when the plate has moved far enough, the edges unstick on one of the faults, causing an earthquake. What causes earthquakes in Chile? Cinna Lomnitz states that Chile emerges as perhaps one of the most highly seismic region in the world (Lomnitz, 2004). As a part of a 5,000 km subduction system and with a subduction rate of more than 7cm/year, Chile is located atop one of the most highly active subduction zones in the world (Lomnitz 2004). As a result of this, Chile has an extended history of earthquakes.
 

peru-chile-trench Nazca Plates

                                      Figure 2. This picture represents a cross-section of the Nazca tectonic plates and fault lines.
                   (http://sciencythoughts.blogspot.com/2012_09_01_archive.html)
 

 

The 1960 Chile earthquake, considered the largest earthquake recorded in the 20th century with a 9.5 magnitude, originated beneath the Pacific Ocean off the coast of southern Chile on May 22, 1960. The earthquake occurred at 7:11 PM local time, approximately 100 miles off the coast of Chile, parallel to the city of Valdivia. The fault displacement source that caused the earthquake occurred at a depth of twenty miles where the Nazca Plate subducted beneath the South American Plate, producing a long rupture zone that extended over an estimated 560-620 miles stretch of the Nazca Plate and extending from Talca, Chile to the Chiloe Archipelago.
 

The earthquake was preceded by a series of foreshocks of magnitude 7.0 and higher that occurred the previous day, including a magnitude 7.9 that caused severe damage in the Concepcion area. After the main shock event, many aftershocks occurred with five of magnitude 7.0 or greater through November 1st of the same year. Considering the magnitude of the earthquake, the death toll for this huge earthquake was less than it might have been because, fortunately, the quake occurred in the middle of the afternoon, many of the structures in the area had been built to be earthquake-resistant, and the fact that the quake was preceded by a series of foreshocks that placed the population on alert. These foreshocks warned residents of the area of the imminent disaster that was coming, frightening most people from their buildings and placing them outside when the main earthquake occurred.
 

Chile earthquake of 1960

                                          Figure 3. Map depicting the region of the Chile earthquake.

                                       (http://www.britannica.com/event/Chile-earthquake-of-1960)
 

 

The Great Chilean Earthquake caused a high death toll and extensive damages. The Encyclopedia Britannica points out that many Chilean cities sustained significant damage, including Puerto Montt, where noticeable subsidence occurred, and Valdivia, where nearly half of the buildings were uninhabitable (Chile Earthquake of 1960).
 

http://seismo.berkeley.edu/gifs/blog_TIEH_Chile_1960_valdivia_lg.png 

Figure 4. Extent of the destruction in Valdivia, Ecuador after the 1960 earthquake.

(http://seismo.berkeley.edu/blog/seismoblog.php/2015/05/22/today-in

Earthquake-history-Chile)

 

Although the havoc caused by the temblor was severe, most of the damages and casualties resulted from the descent, fifteen minutes later, of a tsunami that rose up to 80 feet high along the Chilean coastline from Lebu to Puerto Aisen, cities that paralleled the subducting plate (Chile Earthquake of 1960).  
                               

The quake generated a series of tsunamis that caused most of the damages and deaths because they pushed buildings from their foundations and many others drowned as a result of the tsunami. The United States Geological Service (USGS) reported that Puerto Saavedra was completely destroyed by waves that reached heights of 38 ft. and carried remains of houses inland as much as two miles (Historic Earthquakes).

 

largest earthquake - tsunami damage                largest earthquake - tsunami damage at Queule

Figure 5. Tsunami destruction along the                    Figure 6. Before and after pictures of the    

Chilean Coast.                                                             Queule Valley, Chile.
The bottom picture shows the damage of the 80 ft. tsunami.

      (http://geology.com/records/largest-earthquake)         

       (http://geology.com/records/largest-earthquake)

The combined effects of the disaster left an estimated of two million people homeless. The death toll and damages were estimated at approximately 1,655 killed, 3,000 injured, and $550 million in damages in southern Chile, which would be about $5 billion today.
 

The earthquake also affected surrounding areas. The USGS reports that there was about five feet of subsidence along the Chilean coast from the south end of the Arauco Peninsula to Quellon on Chiloe Island (Historic Earthquakes). This subsidence left a number of buildings below water level at high tide and as much as ten feet of uplift occurred at Isla Guafo.
 

largest earthquake - tsunami map

                                                    Figure 7. A picture of a waterfront street in Quellon, Chile. The

                                                    Immediate area subsided approximately six feet during the earthquake.

                                                   (http://geology.com/records/largest-earthquake/)

 

Additionally, many landslides occurred in the Chilean Lake District from Lago Villarica to Lago Todos los Santos. In addition, two days after the earthquake, on May 24, Puyehue-Cordόn Caulle volcano, in Chile erupted for several weeks after nearly forty years of inactivity, sending steam and ash as high as 6,000 m (Historic Earthquakes).
 

Cordón-Caulle volcano, 1960

                                       Figure 8. The Cordon-Caulle volcano eruption, Los Lagos, Chile on 24 May 1960.                        
                                                       (http://www.britannica.com/event/Chile-earthquake-of-1960)

                               

          Scientists cannot be 100% sure but some seismologists believe the volcanic eruption was linked to the Valdivia earthquake. The 1960 earthquake also caused severe damages along the Pacific Ocean.

Chile earthquake of 1960: tsunami

                                            Figure 9. Effects of the tsunami caused by the 1960 Chile

                                            Earthquake. (http://www.britannica.com/event/Chile-earthquake-of- 1960).

 

Geology.Com reported tsunamis generated by the earthquake traveled across the Pacific Ocean at a speed of over 200 miles per hour (World’s Largest Recorded Earthquake). The enormity of the seafloor shifts that caused the tsunamis was such that the waves that arrived nearly fifteen hours later in the Hawaiian Island, 6,200 miles away, reached a height of 35 feet at landfall in some places. The waves caused millions of dollars of damage at Hilo Bay on the main island of Hawaii, subsequently killing 61people.
 

Hilo, Hawaii; tsunami; Chile earthquake of 1960

                                                 Figure 10. Debris and damage at Hilo Island, Hawaii caused by
                                                                              the 35 foot tsunami after the Chile earthquake, May 1960.                                                                  
                                                                              (http://www.britannica.com/event/Chile-earthquake-of-1960)

 

When the waves reached the main Japanese island of Honshu 22 hours later, the waves had subsided to about eighteen feet and destroyed over 1,600 homes, killing nearly 200 people (Chile Earthquake of 1960). Another 32 people were reported dead or missing in the Philippines after the tsunami hit those islands. Damage also occurred on Easter Island, and in the Samoan Islands. Although the force of the waves that reached the Pacific coast of the United States was mitigated, Crescent City, California saw waves of up to 5.6 feet, and boats and docks in Los Angeles, San Diego, and Long Beach were damaged (Historic Earthquakes).
 

As of today, scientists have not been able to predict earthquakes. What scientists do know is that on any particular fault, there will be another earthquake sometime in the future, but they have no way of telling exactly when and where an earthquake will happen next. Chile sits on a major fault, and its history accounts for many earthquakes, yet predicting the next one is almost impossible. The 1960 earthquake has served as the model for scientists, engineers, architects and emergency agencies to develop better ways to protect and mitigate the effects of earthquakes.
 

The Great earthquake is still studied today in the hopes that scientists can develop new ways of detecting when the next earthquake will happen. Regardless, the Chile earthquake of 1960 is the greatest recorded in near modern history and many fear the next one can be even worse. The Chile earthquake not only destroyed large areas of the country, but it impacted much of the world. Earthquakes are as much a part of daily life across the planet, and they must be studied. Continued studies of the Chile fault lines continue to provide data and present challenges to this day. Perhaps scientists will be able to better estimate when the next major quake will occur, hopefully allowing people enough time to move to safety mitigating large amounts of loss of life.


 

 

Works Cited

“Chile Earthquake of 1960.” Encyclopedia Britannica. Encyclopedia Britannica, 2015. Web. 30

Oct. 2015.

“Historic Earthquakes Chile.” USGS. USGS, 1 Nov. 2012. Web. 30 Oct. 2015.

Lomnitz, Cinna. “Major Earthquakes of Chile: A historical Survey, 1535-1960.” Seismological

Research Letters 75.3 (2004): 368-378. Web. 30 Oct. 2015.

“The Science of Earthquakes.” USGS. USGS, 24 Jul. 2012. Web. 30 Oct. 2015.

“World’s Largest Recorded Earthquake.” Geology.com. Geology.com, 2005-2016. Web. 30 Oct.

2015.