A brief history of Mexican earthquakes

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Over the last two weeks Mexico has experienced two devastating earthquakes (in addition to the damage inflicted by hurricane Katia). The first, late on Sept. 7, was the strongest, at an estimated 8.2 level on the Richter scale. Its epicenter was the city of Tonalá, in the state of Chiapas. Like most localities in the area, a high proportion of Tonalá’s inhabitants are indigenous Mexicans, and many of them live in abject poverty (77 percent of Chiapas’ population lives below the poverty line according to Mexican government statistics). Some 90 people are confirmed to have died in Chiapas and the neighboring state of Oaxaca, and the damage caused by the quake, and its hundreds of aftershocks will take years to repair.

The second was no small tremor, either. At 7.1 on the Richter scale, it was still one of the strongest felt in Mexico in recent decades. At about 1 p.m. on Sept. 19, residents of Mexico City had to run out of homes, schools, and businesses, as buildings began to convulse uncontrollably and crumble to the ground. Since large sections of the City are built on an unstable lake bed, the effects of the tremors are magnified. In a cruel twist, the quake happened on the anniversary of the infamous 1985 earthquake, which killed upwards of 10,000 people (both quakes also occurred just a couple of days after Sept. 16, Mexico’s Independence Day). As of now, the death toll of the most recent quake stands at 200, but is expected to increase.

The 1985 tragedy is embedded in the Mexican consciousness as one of the worst in the country’s history. At 8.1 on the Richter, it was not quite as strong as last week’s in Chiapas. But the instability of the soil in the capital and the terrible building standards that were the norm in Mexico at the time, both contributed to a higher number of casualties. Since then, a number of major quakes have shaken the nation. In 1995, two quakes surpassed seven Richter points– one centered in the state of Guerrero and one between Colima and Jalisco, which left more than 60 people dead. A major quake in 1999 (7.4 Richter), left hundreds of thousands of people homeless in Oaxaca. Between 2012 and 2014, at least three quakes surpassing 7 on the Richter hit different parts of the country. Particularly infamous was a 7.5 quake that hit Ometepec, Guerrero in March 2012, because of the damage caused by hundreds of aftershocks, many surpassing 4 or 5 magnitude on the Richter scale.

Fortunately, the number of casualties in the more recent events has been kept low by the institution of new building standards and the initiation of SASMEX, a system to detect seismic activity and warn the populace before an earthquake actually hits. In the most recent event in Chiapas, residents had some 13 seconds to seek refuge before the worst began. People living farther away had more time, as much as two minutes’ warning. This is enough time for people to exit buildings and move away from electrical towers and large trees.

The flip side is that there’s little SASMEX or any other mechanism will be able to do if an even stronger quake hits Mexico. The Sept. 7 quake has been officially dubbed the strongest in a century, which essentially means the strongest officially recorded, since reliable seismometers only began being installed across the country around 1910. But expert estimates, based on historical and geological evidence, suggest that stronger tremors have been felt in the area. A colossal quake in March of 1787 (when Mexico was still a Spanish colony), is believed to have reached 8.6 Richter, and caused a tsunami that washed off much of the coast that now belongs to Oaxaca. An even stronger one, which estimates indicate reached an unbelievable 9 points Richter, hit Mexico City in 1858. And at least four more tremors over 8 Richter are believed to have hit different areas of Mexico between 1899 and 1903.

There’s no doubt that the Mexican government and the international community will continue to work to mitigate the damage and loss of life caused by earthquakes. Ultimately, though, the unexpected convulsions of the ground, much like the catastrophic storms that are currently crowding the Atlantic Ocean, remind us that for all our technological accomplishments, we are mostly helpless when faced with the power our planet can unleash.

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