2010+Chile+Earthquake

//MinGao Li, BAE/MAE, Pennsylvania State University, 2012 //
 * 2010 Chile Earthquake (February 27, 2010) **

//Key words: Earthquake, Seismology, Liquefaction, Tsunami, Building Performance //

Introduction
toc Two years ago on February 27, 2010, a devastating 8.8 magnitude earthquake struck Chile. Since the earthquake occurred in the middle of the night (3:34 a.m. local time on Saturday), most people were asleep in their homes. Injury due to falling debris or damaged roadways, bridges, and highways was minimized to the time and day of the earthquake. Overall, 521 people were killed, 56 missing, 12,000 injured, and approximately 9% of the population in the region lost their homes (USGS, 2011, pg 5)

According to the United States Geological Survey (USGS), the location of the earthquake was estimated to be 95 kilometer (60 miles) to the northwest of Chillan, 105 kilometer (65 miles) to the northeast of Concepcion, 115 kilometer (70 miles) to the southwest of Talca, and 335 kilometer (210 miles) to the southwest of Santiago. The quake also triggered tsunami waves which crashed many coastal islands. The quake was recorded to be the fifth-largest earthquake in the world since 1900. Extensive damages were dealt across the coastline of Chile. The total economic loss in Chile due to the earthquake was approximately 15-30 billion US dollars (USGS, 2011, pg 5).



Seismology and Geotechnical Aspects
The earthquake was generated in the Chilean subduction zone, along the coast of the Nazca plate and the South American tectonic plate. According to USGS reports, the two plates were converging at 7 meters every century, until they ruptured. The rupture occurred deep beneath the coast and spread in all directions. During this process, the fault slipped to cause earthquake shaking as well as sending a tsunami along the fault-rupture area. In the past, the Chilean coast has suffered many overwhelming earthquakes along this plate boundary, including the 1985 Chile earthquake (see more information at: http://failures.wikispaces.com/1985+Chile+Earthquake+Summary+%26+Lessons+Learned) and the famous 1960 Chile earthquake (also known as the 1960 Valdivia earthquake, see more information at: []). In this 1960 catastrophe, the quake was estimated to have a magnitude of 9.5 and measured to be the largest earthquake in the world. In the event, millions of people died including people living as far away as in Japan.

The size of an earthquake is proportional to the area of the fault plane that moves in an earthquake, multiplied by the amount one side of the fault moves with respect to the other. In this particular earthquake, the fault that moved was about 480 kilometer (300 miles) long and around 100 kilometer (60 miles) wide with an average slip of about 10 meters (Ishii, 2011, pg 1). The rupture began at the epicenter and propagated toward north in the direction of the capital city of Santiago and the second largest city of Concepcion.

In terms of intensity, the 8.8 magnitude earthquake had a lower intensity of shaking than in some other similar sized earthquakes because the fault plane was mostly offshore. Intensity was defined as the effects of the earthquake that was actually experienced at that location, rather than the earthquake magnitude, which does not describe the damage or effect that was experienced. The Modified Mercalli Intensity scale (MMI) was used to describe the intensity of shaking in an earthquake range from barely felt shaking to catastrophic destruction. It is split into 12 increasing levels of damage, which is described in Roman numerals. It does not have any mathematical equations to define these rankings, they are merely rankings of observed ground shaking. Figure 3 describes the intensity of earthquake shaking for each level. For the 2010 Chilean earthquake, the highest intensity, MMI IX, was measured at the tower of Constitucion, just north of the epicenter. An intensity level VIII was recorded in Concepcion, while the capital of Santiago had an intensity level of VI during the earthquake (see figure 2 for details).
 * Intensity **





Tsunamis in general are gravity waves created by earthquakes and landslides. During a strong earthquake, the sudden rise and drop of the sea floor causes the ocean water to set into motion as surface waves. The velocity of seismic wave depends on ocean depth. In the deep ocean, waves travel at about 800 kilometer (500 miles) per hour ( Yamazaki, 2011, pg 1). This wave may be an hour apart at one foot high. As the sea wave approaches the land, velocity decreases due to the increased friction with the increasing shallow sea floor. As the wave velocity decreases, the wave builds up and its height increases since the shore gets shallower and amount of water has to stay the same. The tsunami followed by the 2010 Chilean earthquake caused major damage to over 500 kilometer (310 miles) of coastline, from Tirua to Pichilemu, and at the Juan Fernandez Islands about 600 kilometer (370 miles) off the coast. Around the Pacific, the tsunami was witnessed at over 150 locations and tsunami alerts and warnings were triggered in 54 countries. Tsunami water heights and arrival times were influenced by bathymetry, coastal topography aspect, fault slip, and localized subsidence and uplift due to the earthquake. The first tsunami surges arrived in less than 30 minutes after the main shock. The third or fourth surges are typically largest, arriving in between 90 minutes to four hours alter after the earthquake. The highest water levels recorded by the International Tsunami Survey Team (ITST) were around 10-12 meters high, excepting splash values. Multiple tidal waves of about 1.6 meters from rise to fall in 20-30 minutes intervals were witnessed in the Valparaiso area seven to eight hours after the quake (EERI, 2011, pg 5).
 * Tsunami **

Building Performance
The earthquake shaking caused a wide range of damage to buildings within the affected area. The region has a lots of old houses, churches, and other buildings built with adobe or unreinforced masonry. Absence of reinforcement and connection between adjoining walls resulted in the collapse of about 80,000 houses. Falling debris was a cause to many human deaths. About 300,000 houses and 400 churches were partially collapsed and unsafe to occupy (USGS, 2011, pg 10). They needed to be demolished. The most severe areas of collapse were the Alto Rio condominium and the O’Higgins 241 office tower in Concepcion. In addition, old historical buildings, hospitals, and other building performances during the earthquake and tsunami will be discussed. Cause of failure of these buildings will be examined in an effort to prevent a similar tragedy from happening in the future.

Alto Rio, a fifteen-story condominium, collapsed during the 2010 Chilean earthquake. Out of all the affected buildings, Alto Rio was the only building with more than three-stories that suffered a total collapse in Concepcion during the event. The lateral resisting system of the building consisted of structural reinforced concrete walls. The failure of the building was initiated by the collapse of the first story wall where the bond failed in the lap splices. As a result, the entire building overturned due to the unbalanced load distribution across the whole structure. During the collapse, the parts of the first-story walls that remained attached to the upper level rotated approximately 90 degrees and the ceiling of the first story became nearly vertical (see figures 4 and 5). The building also penetrated the slabs of underground parking spaces. Evidence had shown that the first story wall did not have adequate continuous reinforcements and confinement as well as a faulty designed lap splices (Song, 2011, pg 14). Thus, the collapse of the condominium was inevitable.
 * Alto Rio **





<span style="font-family: Arial,sans-serif;">The 23-story O’Higgins 241 office tower in Concepcion was completed in 2008. During the 2010 earthquake, it experienced a partial collapse at story 10, 14, 18. The shear walls on the east face and south face had significant damage and the exterior north and west faces appeared undamaged. It was believed that the collapse was due to the architectural asymmetry and lack of continuous reinforcement (EERI, 2011, pg 9). The building also had a number of setbacks along one of its faces which may have triggered a vertical geometry irregularity. This kind of irregularity may reduce the lateral stiffness of the entire building and make it more vulnerable to strong lateral forces.
 * <span style="font-family: Arial,sans-serif;">O’Higgins 241 office building **



<span style="font-family: Arial,sans-serif;">One of the historical buildings, Intendencia Regional del Maule, was severely damaged during the earthquake. The building was a three-story public historical building located in Talcal, Chile. The damage consisted of cracked and heavily compromise unreinforced masonry walls as well as interior and exterior architectural details and finishes. This was expected since old buildings such as the Intendencia Regional del Maule was not designed for the current earthquake knowledge. The building had undergone extensive architectural renovation shortly before the 2010 Chile earthquake. However, after the earthquake, the local government did not have any more money to strengthen and repair the damaged building.
 * <span style="font-family: Arial,sans-serif;">Historical Buildings **

<span style="font-family: Arial,sans-serif;">Hospital performance during the earthquake event was related to the age of the building and the quality of its lateral force resisting system. The Talca Regional Hospital was one of the new hospitals that suffered greatly during the earthquake. The building had major exterior damage on the façade and decorative architectural elements. The parapet was found to be improperly connected to the structure and collapsed as a result. The hung ceiling also collapsed in several areas and it damaged many building contents and expensive medical equipment. The Talca Regional Hospital had to be shut down for repair, at a time when it was needed badly after the earthquake. In comparison, other hospitals in the affected region were not in any better condition than the Talca Regional Hospital. The suspended ceiling in most hospitals also collapsed and there was extensive damage to lots of equipment and interior architectural components. Even those hospitals that were still functional after the earthquake had to close about 70% of the usable spaces for repair (Yanev, 2011, pg 23).
 * <span style="font-family: Arial,sans-serif;">Hospitals **

<span style="font-family: Arial,sans-serif;">The 8.8 magnitude earthquake also caused significant damage to public and private infrastructure. Since the epicenter was close to the primarily transportation network of Chile, the entire transportation system suffered damage and disruption. Roadbed and embankment failures were primary due to improper compaction of the soils and poor ground fill during road construction. Bridge and viaduct collapses were mainly because of the failure of the girder at the vertical support. Liquefaction also plays a major role in the failure of highway and bridges. Liquefaction caused by lateral movements spreads the soil and embankment fill apart which cause settlement issues in some of the column foundations. Two major collapsed bridges were the concrete framed long Bio-Bio Bridge and the unreinforced masonry Puente Rio Claro Bridge. Both of these bridges were scheduled for replacement because they did not meet the current code standard. Although the unreinforced masonry bridge was built in the 1870 and had survived many earthquakes, strong vertical movement during the 2010 earthquake caused it to collapse. Fortunately, most typical bridges in Chile were undamaged or had only minor damage to the support. The Chilean bridges were usually huge, with large columns and great detailing to prevent the slippage of girders from their support. Redundancies of column supports were also crucial in preventing these bridges from a total collapse. After the event, quick responses and good repair teams of Chile managed to restore the road network within a few days.
 * <span style="font-family: Arial,sans-serif;">Infrastructure **

<span style="font-family: Arial,sans-serif;">



<span style="font-family: Arial,sans-serif;">The tsunami that followed the 2010 Chilean earthquake caused great damage to many structures resulting from hydrodynamic loading, impact loading from debris and scour around foundations. Timber-framed houses and unreinforced or poorly reinforced masonry structural were very vulnerable. Lightly framed buildings were also destroyed in many coastal towns. In Dichato, 1500 homes were destroyed (EERI, 2011, pg 6). In Talcahuano, nonstructural elements were severely damaged. Almost all exterior enclosures and contents of commercial buildings and industrial warehouses along the shoreline were damaged by hydrodynamic loading of the tsunami and debris impacts. In Talcahuano Harbor, sheet pile wharf structures were damaged by soil failures caused by severe scours due to inundation and drawdown. However, reinforced concrete buildings performed exceedingly well structurally, even when inundation reached well above the second floor level. According to the Earthquake Engineering Research Institute (EERI), 124 out of the 521 identified causalities and missing were attributed to the tsunami. However, only a few coastal residents died in the tsunami because of their high level of tsunami awareness due to their personal experience in the 1960 earthquake and tsunami event. In Chile, people were prepared and trained in school to obtain a high level of awareness for natural hazards.
 * <span style="font-family: Arial,sans-serif;">Damage done by Tsunami **



Other Earthquake Comparison
<span style="font-family: Arial,sans-serif;">The 2010 8.8 magnitude Chile earthquake was the second strongest earthquake that hit Chile recorded since 1960. According to USGS reports, the 1960 Chile earthquake was estimated to have a magnitude of 9.5, which is the largest earthquake in the world. Similar to the 2010 Chilean quake, the 1960 Valdivia earthquake was created by the release of stress caused by the sub ducting Nazca Plate and the South American Plate. This event was so strong that it killed around 1,600, 3000 injured and left 2 million people homeless. The cost of the damage was approximately 400 to 800 million US dollars (this would be about 2.9 to 5.8 billion dollars in today’s standard because of inflation) The earthquake also caused a deadly tsunami that harmed people living as far away as southern Chile, Philippines, southeast Australia, Hawaii, Japan, eastern New Zealand and the Aleutian Islands. In addition, the quake caused several landslides west of Tralcan Mountain, which blocked the outflow of Rinhue Lake. The lake’s water level quickly rose above the 24 meter high dam in less than 5 hours after the main shock. As a result, it flooded several nearby towns and the city of Valdivia affecting 100,000 people living in the area. Strict design codes were enforced in Chile after the event.
 * <span style="font-family: Arial,sans-serif;">1960 Chile Earthquake Comparison **

<span style="font-family: Arial,sans-serif;">Compared to the 2010 Haiti earthquake, the death tolls in the 2010 Chile earthquake were far less severe. This was due to the fact that Chile is wealthier and much better prepared than Haiti, with strict building codes along with a long history of handling seismic catastrophes. In terms of energy release at the epicenter, the Chilean quake was about 501 times stronger than the Haitian quake. However, in Haiti, there was no building code. Thus the 7.0 magnitude catastrophe easily crushed their poorly constructed buildings. During the event, many Haitians tried to hold onto any nearby cement pillars for support but only to see them crumble in their hands. Causalities were estimated to be 220,000 people while Chile’s death toll was only in the hundreds (Bajak, 2010). This is expected because no living Haitian had ever experienced a quake as strong as the one that happened on January 12. They were simply not taught how to react during an earthquake. Even after the shock, most Haitians didn’t know whether their president was alive or dead until the very next day. Therefore, the government of Haiti could not react quickly enough to provide shelters and food supplies to its citizens. As a result, millions of Haitians were left homeless and cholera spread throughout the region infecting around 81,000 (see more details at: http://failures.wikispaces.com/2010+Haiti+Earthquake).
 * <span style="font-family: Arial,sans-serif;">2010 Haiti Earthquake Comparison **

Lessons Learned and Suggested Improvements
<span style="font-family: Arial,sans-serif;">After the 2010 earthquake event, many concrete buildings were determined to have performed as expected and casualties were minimal. This was due to the strict design code implemented after the destructive earthquake of 1960 in Chile. The largest life losses were caused by the collapse of old buildings and the effect of the tsunami. The largest economic losses were due to the damage in roads, bridges and ports. There was also widespread damage to building interiors in office, commercial and industrial buildings. Inadequate shear walls, along with asymmetric architectural configurations caused much of the damage to modern conventional mid- and high-rise buildings. Concrete shear walls typically had insufficient steel reinforcement details and core confinements. Some of the conventional details for the bracing of façades were inadequately designed for this earthquake. But out of all high-rise buildings, only the Alto Rio collapsed completely, and the O’Higgin building collapsed partially. Given the number of structures in the affected area, this performance implies generally good engineering and construction practices. In conclusion, Chile’s infrastructure and modern buildings generally protected the population. However, there are some issues that need to be addressed. Many bridges that collapsed during the earthquake require good continuity of reinforcement and well-confined ductile members. Alto Rio condominium needed stricter management and control to prevent from a total collapse. Although the structural designer of Alto Rio satisfied the Chilean seismic code requirement, his design did not provide proper lap splices and confinements in the shear walls to resist the 8.8 magnitude quake, hence the building failed.
 * <span style="font-family: Arial,sans-serif;">Conclusion **



<span style="font-family: Arial,sans-serif;">According to Yanev and his team (Yanev 2011) from the University of California, there are several areas in the code that needed to improve after the 2010 Chilean earthquake.
 * <span style="font-family: Arial,sans-serif;">Suggested Code Improvement **
 * <span style="font-family: Arial,sans-serif;">A new design spectrum obtained in this earthquake and its aftershock can be incorporated.
 * <span style="font-family: Arial,sans-serif;">A more detailed specification for reinforcing steel to improve the integrity and ductility of concrete structures subjected to seismic load should be implemented in the code.
 * <span style="font-family: Arial,sans-serif;">Micro zonation maps for vulnerable areas such as Vina del Mar, Concepcion, and other cities with soft and variable soils should be developed and coordinate with municipal zoning maps.
 * <span style="font-family: Arial,sans-serif;">A protocol for structural design, review, inspection and materials verification shall be developed.
 * <span style="font-family: Arial,sans-serif;">limitations should be set in the code to allow simplified analysis for structural design only in certain cases. For instance, a simplified analysis procedure should only be allowed for structures with limited height, very few to none irregularity, founded on firm soils, and with characteristics similar to those that performed well in this earthquake or other strong earthquakes in the past. Sixth, procedures and criteria should be established to evaluate and rehabilitate existing seismically deficient structures.

<span style="font-family: Arial,sans-serif;">Moreover, educational or training programs can be improved further in Chile to prepare for future natural catastrophe <span style="font-family: Arial,sans-serif;">(Yanev, 2011, pg 35-36).
 * <span style="font-family: Arial,sans-serif;">Suggested Training Program **
 * <span style="font-family: Arial,sans-serif;">The existing programs can be improved to include knowledge and operative training to face earthquake and tsunami to minimize human and material loss.
 * <span style="font-family: Arial,sans-serif;">Research should be done to improve Chilean seismology and earthquake engineering knowledge to design measures that eliminate or minimize human, cultural and material loss.
 * <span style="font-family: Arial,sans-serif;">Financial aid and work opportunities should be provided for scientists and engineers that specialized in earthquakes and seismology.
 * <span style="font-family: Arial,sans-serif;">Various detailed post-earthquake studies should be conducted to collect and analyze important engineering data in order to completely learn from the lessons of this earthquake.
 * <span style="font-family: Arial,sans-serif;">A quality seismic data bank should be developed in order to let the rest of the world learn from the 2010 Chilean earthquake.

<span style="font-family: Arial,sans-serif;">After all, it would be a good idea to build a monument from the remains of the collapsed structures in the earthquake to remind Chileans that they live in a country where earthquakes strike often and the country will always come back from these catastrophic events (Yanev, 2011, pg 36).

Additional Resources

 * Akhtary, M. (2010). //Evaluation of building behavior during aftershock events following the february 27th, 2010 m 8.8 earthquake in chile//. (Master's thesis, California State University, Fullerton).**
 * The report has important information for the responses of four different building during the 2010 Chile earthquake. The buildings' performance is evaluated base on the natural frequency, period, acceleration, velocity, and displacement.


 * Chinn, P. (2011). //<span style="font-family: Calibri,sans-serif;">Deadliest earthquakes // [DVD].**
 * This is a documentary video from NOVA that explores the phenomenon of earthquakes. It brings together geologists and other experts to deal with and discuss the damage wrought by some of the most destructive episodes in seismic activity such as the 2010 Chile earthquake.