Earthquake Damage in Mexico City, Mexico, September 19, 1985
Dataset Identification:
Resource Abstract:
On September 19, 1985, a magnitude 8.1 earthquake occurred off the Pacific coast of Mexico. The damage was concentrated in
a 25 km2 area of Mexico City, 350 km from the epicenter. The underlying geology and geologic history of Mexico City contributed
to this unusual concentration of damage at a distance from the epicenter. Of a population of 18 million, an estimated 10,000
people were killed, and 50,000 were injured. In addition, 250,000 people lost their homes and property damage amounted to
$5 billion. This set of slides shows different types of damaged buildings and the major kinds of structural failure that occurred
in this earthquake including collapse of top, middle and bottom floors and total building failure. The effect of the subsoils
on the earthshaking and building damage are emphasized. Over 800 buildings crumbled, including hotels, hospitals, schools,
and businesses. Communications between Mexico City and the outside world were interrupted for many days. Surrounding areas
affected by the earthquake included the Mexican States of Jalisco, Guerrero, and Michoacan. Damage in the epicentral area
wasrestricted to a few tourist resorts and industrial estates along the Mexico Pacific coast. A two-meter tsunami also caused
some damage in this area. There are geologic reasons why Mexico and especially Mexico City are vulnerable to earthquake damage.
Along the west coast of southern Mexico and Central America, the Cocos Plate dips beneath the North American Plate producing
a very active seismic zone. Since the beginning of the Twentieth Century, 84 earthquakes of magnitude greater than 7.0 have
occurred in this zone. The location of the 1985 earthquake's epicenter near the coast at the border between the states of
Michoacan and Guerrero was not a surprise. Prior to the 1985 earthquake this area, located between two areas that had experienced
recent earthquakes, was known as the "Michoacan Gap." The "gap" was filled in 1985 by the main shock and a severe aftershock
(magnitude 7.5) that occurred two days later, on September 21. Mexico City lies in a broad basin formed approximately 30 million
years ago by faulting of an uplifted plateau. Volcanic activity closed the basin and resulted in the formation of Lake Texcoco.
The Aztecs chose an island in this lake as an easily defended location for their capitol. The expansion of Mexico City and
the gradual draining of the lake left the world's largest population center located on unconsolidated lake-bed sediments.
These soft sedimentary clay deposits amplified the seismic waves, or they liquefied, destroying the foundation of some buildings.
Double resonance coupling between the earthquake waves, the subsoils, and the buildings caused intensity IX shaking in some
areas, lasting up to three minutes. Earthquakes in 1957 and in 1979 also damaged Mexico City. However, neither of these earthquakes
was quite as devastating as the 1985 earthquake. In the area of greatest damage in downtown Mexico City, some types of structures
failed more frequently than others. In the highest damage category were buildings with six or more floors. Resonance frequencies
of these buildings were similar to the resonance frequencies of the subsoil. Because of the unusual flexibility of Mexico
City structures, upper floors swayed as much as one meter and frequently collapsed. Differential movements of adjacent buildings
also resulted in damage. A flexible building often failed if it was held by adjacent, more rigid lower buildings. Damage or
failure often occurred where two swaying buildings came in contact with each other. Corner buildings were also vulnerable
to damage. Lessons learned from the patterns of earthquake damage need to be applied to prevent another disaster when an earthquake
releases stress that is building in another area-along the Mexico coast between Acapulco and Zihuatanejo.
Citation
Title Earthquake Damage in Mexico City, Mexico, September 19, 1985
publication Date
1994
Edition First
presentationForm
cited responsible party
-
publisher
organisation Name
DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
cited responsible party
-
originator
organisation Name
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (comp)
cited responsible party
-
publisher
organisation Name
National Geophysical Data Center
other Citation Details
Cinergi keyword enhanced.File generated at Thu Aug 24 07:00:40 UTC 2017
purpose:
Make available Damage Photos for research and education
Resource language:
eng; USA
Resource progress code:
completed
Resource Maintenance Information
maintenance or update frequency:
notPlanned
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Legal Constraints
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Access Constraints: None Use Constraints: None Distribution Liability: While every effort has been made to ensure that these
data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages
caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system.
NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
Resource extent
Geographic Extent
Geographic Bounding Box
westBoundLongitude
-99.09
eastBoundLongitude
-99.09
northBoundLatitude
19.24
southBoundLatitude
19.24
Temporal Extent
Publication Date
1985-09-19
1985-09-21
Credits:
Patricia Lockridge
point of contact
-
pointOfContact
organisation Name
DOC/NOAA/NESDIS/NCEI> National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
notes: This metadata was automatically generated from the Content Standard for Digital Geospatial Metadata: Extensions for Remote
Sensing Metadata standard version FGDC-STD-012-2002 using the June 2011 version of the FGDC RSE to ISO 19115-2 transform.
The Spatial Reference Information is not currently mapped over to ISO but will be mapped in future versions.
notes: This record was automatically modified on 2015-10-14 to include references to NCEI where applicable.
Metadata contact
-
pointOfContact
organisation Name
DOC/NOAA/NESDIS/NCEI> National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce