The 1985 Mexico City earthquake struck in the early morning of 19 September at 07:17:50 (CST) with a moment magnitude of 8.0 and a maximal Mercalli intensity of IX (Violent).

Then-president Miguel de la Madrid and the ruling Institutional Revolutionary Party (PRI) were widely criticized for what was perceived as an inefficient response to the emergency, including an initial refusal of foreign aid.

Damage to structures is worsened by soil liquefaction which causes the loss of foundation support and contributes to dramatic settlement of large buildings.

[3][7][8] Mexico City's downtown area mostly lies on the silt and volcanic clay sediments of the bed of the historic Lake Texcoco, which are between seven and thirty-seven meters deep and have a high water content.

Nearly all the buildings that collapsed were located in this lake zone that extended from Tlatelolco in the north to Viaducto Miguel Alemán in the south, Chapultepec Park in the west and to a short distance east of the Zócalo or main plaza.

It was also surrounded by a number of other buildings belonging to the hospital complex such as a blood bank, teaching facilities, offices as well as the original convent.

[23] Manuel José Othón Street in the Colonia Obrera neighborhood, near Metro station San Antonio Abad, was the location of one of the many garment factories in the city center area.

[24] The Conalep SPP was a building located between the streets of Iturbide and Humboldt, in the Historic Center of Mexico City, which was destroyed by the 8.1 magnitude earthquake of 19 September 1985.

[33] In the Conjunto Urbano, two of the three modules of the building called "Nuevo León", at thirteen stories tall, completely collapsed, while the other one was severely damaged.

[32] During these rescue efforts, a nearby building, called Oaxaca, began to creak noisily, causing everyone to run and abandon the site temporarily, but it did not collapse.

[23][35] One of the most famous images of the event is the recording of the live broadcast of Hoy Mismo, then the morning news cast in the Televisa television network, when the earthquake struck.

The three newscasters were María Victoria Llamas (in place of Guillermo Ochoa, the principal anchor who was on leave), Lourdes Guerrero and Juan Dosal.

[36] The last image broadcast from the studio was that of Lourdes Guerrero stating "... it's still shaking a little (sigue temblando un poquitito), but we must take it calmly.

The transmission ended because a nearby 10-ton antenna had bent over and crushed parts of Televisa's buildings that were located on Niños Héroes and Dr. Río de la Loza Streets in Colonia Doctores.

[36] Some members of the Hoy Mismo staff died, including producer Ernesto Villanueva and engineer David Mendoza Córcega, who had just parked at the Televisa building, but had no time to escape from his car.

On Line 1, there was no service in stations Merced, Pino Suárez, Isabel la Católica, Salto del Agua, Balderas or Cuauhtémoc.

In total, the city lost more than 4,000 public hospital beds in the earthquake, severely disrupting these institutions' ability to handle the crisis.

Students at the Universidad de las Américas in nearby Puebla reported feeling as if the cafeteria had been lifted and rocked back and forth, shattering windows and injuring some people but mostly causing panic.

Coastal and most inland damage was moderated by the fact that most of the west of Mexico sits on bedrock, which serves to transmit the shockwaves without amplifying them.

Ordinary citizens organized brigades to help with rescue efforts and to provide food, clothing and emotional support to the homeless.

[23] The military was deployed to patrol streets to prevent looting after a curfew was imposed,[39] as well as rescue, sanitary efforts and other, with 1,836 soldiers initially sent in and another 1,500 conscripts sent later.

[18] The federal government's first public response was President de la Madrid's declaration of a period of mourning for three days starting from 20 September 1985.

The crisis was severe enough to have tested the capabilities of wealthier countries, but the government from local PRI bosses to President de la Madrid himself exacerbated the problem aside from the lack of money.

President de la Madrid refused to cut foreign debt payments to use the money to help with the recovery effort.

[20] CUD and other popular movement representatives met the head of the Secretariat of Urban Development and Ecology (SEDUE) Guillermo Carrillo Arena on 27 September 1985.

The deal generally worked; movements like CUD moderated their stances and agencies like SEDUE and PRHP made progress in rebuilding housing, regardless of political affiliation.

One of the prominent groups was the delegation of the Israel Defence Force (IDF), which was enthusiastically welcomed and hosted by the Jewish community of Mexico City.

[citation needed] At the time of the earthquake, Mexico was in its fourth year of a foreign debt crisis, and a contracting economy causing serious political problems for the Institutional Revolutionary Party (PRI).

[42] One preparation that was made for any future events was the alert system, Sistema de Alerta Sísmica (SAS), which sends early-warning messages electronically from sensors along the coastal subduction zone in Guerrero.

They have gained international fame as they have helped in disasters in San Salvador, Taiwan, in the countries of the rim of the Indian Ocean after the tsunami there in 2004,[45] and in the January 2010 Haiti earthquake.