The 2010 Maule, Chile Earthquake: Lessons and Future Challenges
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The 2010 Maule, Chile Earthquake: Lessons and Future Challenges TABLE OF CONTENTS Introduction 1 1. The 2010 Maule, Chile Earthquake 2 1.1 Seismological Features 2 1.2 Ground Shaking 2 1.3 Tsunami 4 1.4 Casualties 5 1.5 Historical Perspective 6 The May 21-22, 1960 Chile Earthquakes 7 2. Design and Construction in Chile 8 2.1 History of the Chilean Building Code 8 2.2 Construction Patterns 9 2.2.1 Reinforced Concrete Construction 9 2.2.2 Confined Masonry Construction 10 2.2.3 Regional Variations in Construction 10 3. Ground Reconnaissance 11 3.1 Damage Trends 11 3.2 Ground Shaking Intensities 11 3.3 Key Observations 12 4. Commercial Property Damage 13 4.1 Building Damage: Capital Region 13 4.2 Building Damage: Epicentral Region 15 4.3 Nonstructural and Contents Damage 16 Torre O’Higgins 17 Edificio Alto Río 18 5. Industrial Property Damage 19 5.1 Epicentral Region: Talcahuano 19 5.1.1 Steel 19 5.1.2 Petroleum 19 5.1.3 Cement 22 5.1.4 Galvanized Wire 23 5.2 Epicentral Region: Other cities in Biobío and Maule regions 24 5.2.1 Power Generation 24 5.2.2 Glass 24 Chilean Pulp Industry 25 5.2.3 Pulp 25 5.2.4 Food and Beverage 26 Chilean Wine Industry 27 6. Residential Property Damage 28 6.1 Tsunami Damage 28 6.2 Reconstruction Efforts 29 I TABLE OF CONTENTS (CONTINUED) 7. Public Building Damage 30 7.1 Universities 30 7.2 Hospitals 31 7.3 Historic Masonry Structures 31 8. Infrastructure Damage 32 8.1 Ports and Harbors 32 8.2 Airports 33 8.3 Roadways and Bridges 34 8.4 Lifeline Networks 35 8.4.1 Electricity 35 8.4.2 Natural Gas 36 8.4.3 Water 36 8.4.4 Telecommunications 36 9. Losses and Modeling Insights 37 9.1 Economic Losses 37 9.2 Insured Losses 37 9.3 Modeling Insights 38 9.3.1 Fire Following Earthquake 39 9.3.2 Loss Amplification 39 9.4 Event in Perspective 40 References 41 INTRODUCTION On Saturday, February 27, 2010, at 3:34 a.m. local time, a powerful earthquake struck offshore of the Maule region in central Chile. Occurring along the interface between the Nazca and South American plates, the subduction zone event caused severe ground shaking across a 660 km (400 mi) swath of the country— from Valparaíso to south of Concepción—and generated a tsunami that ravaged the coastline. In all, over 520 people lost their lives in the event. Based on the historical record and significant strain accumulation on the subduction zone, the location and magnitude of the earthquake was not unexpected. The earthquake filled in a “seismic gap” along the subduction zone that had not experienced an event since 1835. In 2011, according to the U.S. Geological Survey (USGS), if one considers worldwide events since 1900, this earthquake’s moment magnitude Mohsen Rahnama of 8.8 is tied for the sixth largest event in the historical record. Senior Vice President In March 2010, Risk Management Solutions (RMS) deployed two reconnaissance Risk Management Solutions teams to the region to investigate the impacts from the earthquake and tsunami. These teams spent two weeks in the field, collaborating with engineers and seismologists from other organizations, including the University of Chile, the USGS, and Stanford University. Post-event field reconnaissance, in its ability to rapidly and precisely make observations about the impacts from a disaster, is critical in the management of emergency response activities in the short term and the understanding of natural hazards in the long term. The primary goals of the reconnaissance teams were to confirm ground shaking and tsunami height estimates, as well as to collect empirical data on physical damage to the property and infrastructure within the impacted region. With the extent of damage and rising insurance industry losses, RMS re-deployed a team in May 2010 and then again in December 2010. From this extensive reconnaissance work, in conjunction with modeling efforts, RMS confirmed its initial insured loss estimate of $7 to $12 billion. Chile is a major insurance market, and the devastating event ranks as one of the largest insured catastrophe losses outside of the United States. The findings presented in this report highlight the unique lessons learned from the 2010 earthquake. The relatively low casualty count and degree of destruction from this event, considering its massive magnitude, demonstrates the success of the Chilean seismic building code in providing superior performance against earthquake ground motions. The geographical concentration of industrial risks, which are highly interdependent upon one another, illustrates how business interruption loss is compounded over time. The status of reconstruction efforts over a year later—particularly along tsunami-impacted coastlines—highlights the complexities inherent to societal recovery after a catastrophe. The 2010 Maule, Chile Earthquake serves as a stark reminder of the earthquake and tsunami risk to those living along subduction zones—in South America, Japan, North America, and other at-risk regions worldwide. The lessons learned, as well as the additional data continuing to emerge from this event, will ultimately improve the management of earthquake risk for years to come. 1 12 THE 2010 MAULE, CHILE EARTHQUAKE 1.1 Seismological Features ruptured along the interface between the Nazca and South American plates for almost 450 km (280 mi), The 2010 Maule, Chile Earthquake that struck offshore from the town of Pichilemu in the north to the Arauco of Chile during the early morning hours of February 27, Peninsula in the south. Interpretations of the ground 2010, was a subduction zone interface event occurring motions indicate that the highest slip was concentrated along the boundary between the Nazca and South along a 300 km (190 mi) section of interface and that American tectonic plates. Along the western coast of the zone ruptured to a depth of almost 50 km (30 South America, the oceanic Nazca Plate plunges, or mi). With an average slip of 7 m (33 ft) across a fault subducts, beneath the South American Plate at a rate rupture area of approximately 80,000 km2, the event of about 70 mm/yr (2.8 in/year). This type of tectonic released an enormous amount of energy—equivalent environment is referred to as a subduction zone and to approximately 238 megatons of TNT. the interface region between the two plates at depth As expected, the mainshock was followed by a produces the world’s largest earthquakes, including sequence of aftershocks, though fewer aftershocks the 1960 M9.5 Chile Earthquake, the 1964 M9.2 occurred compared to other historical earthquakes Alaska Earthquake, and the 2004 M9.1 Indian Ocean of similar size. According to the USGS National Earthquake. Earthquake Information Center (NEIC), over 300 The size of this event was determined to be aftershocks of M5.0 or greater occurred through April moment magnitude (M) 8.8 by numerous seismological 26, 2010, of which over 20 were M6.0 or greater. The agencies, including the Servicio Sismológico of mainshock also caused sudden displacement of the the Department of Geophysics at the University of seafloor, generating a series of tsunami waves that Chile, and the U.S. Geological Survey (USGS). The significantly impacted the Chilean coast from San earthquake initiated at a depth of 35 km (21.7 mi) and Antonio in the north to Tirúa in the south. While the localized impacts of the tsunami waves were severe for some Chilean coastal communities, the far field impacts were minimal. 80° 78° 76° 74° 72° !70° 68° !!!! 0100 200 400 600 800 ! !!!! !! !!!!! ! 1.2 Ground Shaking Kilometers !!!! !!!!!!!!!!!!!!!!!!!!! ! ! !! ! 28° !! ! 28° ! !! February 27, 2010 ! ! ! ! ! ! Shortly after the M8.8 earthquake, the USGS issued a !! ! ! ! ! ! ! ! ! Main Shock ! ! ! !! ! ! ShakeMap for the event (http://earthquake.usgs.gov/ ! ! !!!! Aftershocks (72 hours) !!!!! ! 30° !! ! 30° ! ! ! earthquakes/shakemap/), with estimates of ground Earthquakes 1902-2009 !!!!! ! ! ! ! !!! !! ! M 5.5 - 6.0 ! ! ! ! ! ! ! ! ! !!! ! motion. One measure of ground motion portrayed in ! !! ! ! ! ! !! ! ! M 6.0 - 7.0 ! !!! ! !!! !! ! ! ! !!! ! !! ! ! ! 32° ! !! ! ! 32° M 7.0 - 8.0 !! !! ! a ShakeMap is the “instrumental” Modified Mercalli !! !! ! !!!! ! !! ! ! !!!!! ! ! ! M > 8.0 Valparaíso!!! Santiago! ! !! ! !!!!!!! ! ! Intensity (MMI). The basic MMI scale is a subjective !!!!!!!! ! ! !!!!!! ! ! ! !!!!!!! ^ ! ! !!!!!!!! ! ! !! !!!!!!! ! !!!!!!!!!!!!!! ! !!!!!! !!!!!!!! San Antonio 34° ! !!!! !!!!!!!!! ! ! 34° way to differentiate and compare ground motions ! !!!!! !!!!!!!! ! ! ! ! !!!!!!! !!! !!! ! ! !!!!!! !!!!!!!!!! ! ! ! !!!!! ! !!!!!!!! !! !!Pichilemu! ! !!!!!! !!!!!!!!!!!!!!!! !!! !! !!!!!!!!! !!!! ! ! ! ! ! !!!!!!!!!! !!! based on damage levels for areas impacted by an !! ! !!!!!!!!!!!!!! ! ! !!!!!!!! ! ! ! ! ! !!!!!!!!!! ! !!!!!!!!!! !!!!! ! !!!!!!!!!! !!!! ! ! !!!!!!! !! !! ! ! ! !!!!!!! !!!! ! ! earthquake. The instrumental MMI converts ground 36° ! !!!!!!! !!! ! 36° ! !!!!!^_!!!!! !!! !!!!!!! !! !!!!!!!!!!!! !!!!! ! !!! !! !!!!!!!!!!!!! ! ! !!!! ! !Concepción! motion values, such as peak ground acceleration !!! !! !!!!! ! ! ! !! !!!!!!! !!! ! !!!! !!! !!!!!!!!!!!! ! !!!!!!!!!!!!Arauco! !! !!! !!!!!!!!!! ! ! !!!!!!!! ! !! ! and velocity, to equivalent MMI values based on !!!!!!!! 38° ! !!! 38° ! ! !!!!!!!!!! ! ! !! !!!!! !! ! !! ! !!!!! !! ! ! ! ! Tirúa! past comparisons of direct damage and measured ! ! ! ! ! !! ! ! ! ! ground motion. Because the ShakeMap is based on !! ! 40° !! 40° ! actual ground motion observations and theoretical ! ! !! ! ! calculations of ground motion, they are not directly ! 42° ! ! 42° ! ! linked to damage observations.