Historic Earthquakes

Michoacan, Mexico
1985 September 19 13:17:47 UTC
Magnitude 8.0

Michoacan, Mexico

At least 9,500 people were killed, about 30,000 were injured, more than 100,000 people were left homeless, and severe damage was caused in parts of Mexico City and in several states of central Mexico. According to some sources, the death toll from this earthquake may be as high as 35,000. It is estimated that the quake seriously affected an area of approximately 825,000 square kilometers, caused between 3 and 4 billion U.S. dollars of damage, and was felt by almost 20 million people. Four hundred twelve buildings collapsed and another 3,124 were seriously damaged in Mexico City. About 60 percent of the buildings were destroyed at Ciudad Guzman, Jalisco. Damage also occurred in the states of Colima, Guerrero, Mexico, Michoacan, Morelos, parts of Veracruz and in other areas of Jalisco.

The maximum Modified Mercalli intensity was IX at Mexico City, Ciudad Guzman and the Pacific Coast towns of Lazaro Cardenas, Ixtapa and La Union. Felt reports were received from Mazatlan, Sinaloa to Tuxtla Gutierrez, Chiapas, and as far away as Guatemala City, Guatemala and Houston, Texas. The quake was also felt at Brownsville, McAllen, Corpus Christi, Ingram and El Paso, Texas. It was felt very strongly by people on board the ship "Nedlloyd Kyoto" located at 17 35.4' North, 102 36.9' West.

Landslides caused damage at Atenquique, Jalisco and near Jala, Colima. Rockslides were reported along the highways in the Ixtapa area and sandblows and ground cracks were observed at Lazaro Cardenas.

A tsunami was generated which caused some damage at Lazaro Cardenas, Zihuatenejo and Manzanillo. Estimated wave heights were 3 meters at Zihuatenejo and 2.8 meters at Lazaro Cardenas. Tide stations recorded maximum wave heights (peak-to-trough) of 1.4 meters at Acapulco, Mexico; 60 cm at La Libertad, Ecuador; 58 cm at Acajutla, El Salvador; 24 cm at Kahului, Hawaii and at Pago Pago, American Samoa; 22 cm at Hilo, Hawaii; 21 cm at Baltra Island, Galapagos; 14 cm at Apia, Samoa; 7 cm at Rikitea, Gambier Islands; and 5 cm at Papeete, Tahiti. There were some reports, still unconfirmed, that some ships off the Pacific coast of Mexico observed unusually heavy seas up to 30 meters high near the time of the earthquake.

Seiches were observed in East Galveston Bay, Texas and in swimming pools in Texas, New Mexico, Colorado and Idaho. Water well fluctuations were recorded at Ingleside, Texas; Santa Fe, New Mexico; Rolla, Missouri; Hillsborough County, Florida; and Smithsburg, Maryland.

A large percentage of the buildings which were damaged in Mexico City were between 8 and 18 stories high, indicating possible resonance effects with dominant two-second period horizontal ground accelerations which were recorded in the area.

The focal mechanism is poorly controlled and corresponds to reverse faulting.

Compiled from press reports, Foreign Broadcast Information Service and personal communication with Cinna Lomnitz, Universidad Nacional Autonoma de Mexico, Mexico City and Lloyd S. Cluff, Pacific Gas and Electric Co., San Francisco.

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