Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Vanessa Braggs
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.
Figure 1. This picture represents the world’s tectonic plates and fault lines
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.
This picture represents a cross-section of the Nazca tectonic plates and fault
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
Figure 3. Map depicting the region of the Chile earthquake.
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).
Figure 4. Extent of the destruction in Valdivia, Ecuador after the 1960 earthquake.
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).
Figure 5. Tsunami destruction along the Figure 6. Before and after pictures of the
Queule Valley, Chile.
The bottom picture shows the damage of the 80 ft. tsunami.
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.
Figure 7. A picture of a waterfront street in Quellon, Chile. The
Immediate area subsided approximately six feet during the 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).
Figure 8. The Cordon-Caulle volcano eruption, Los Lagos, Chile on 24 May 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.
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.
Figure 10. Debris and damage at Hilo Island, Hawaii caused by
the 35 foot tsunami after the Chile earthquake, May 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.
“Chile Earthquake of 1960.” Encyclopedia Britannica. Encyclopedia Britannica, 2015. Web. 30
“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.