Hazards of Earthquakes and Secondary Effects in Mexico
The historical occurrences of earthquakes, landslides, and liquefaction in Mexico
On the morning of September 19, 1985, an 8.0 magnitude earthquake centered roughly 240 miles away rocked Mexico City. In minutes, over 900 buildings were destroyed and over 4000 damaged just in the city itself. A third of the city was hit by power outages and nearly 70% of the transportation network was blocked by debris. After two months of clearing roads and structures, there were estimates that anywhere between 9,000-35,000 people were killed by the disaster and up to 100,000 were left homeless (USGS).
This was not Mexico's first major earthquake, nor its last. In 1932, the city of Guadalajara was shaken by an 8.1 magnitude earthquake; and in 2010, a 7.2 magnitude earthquake shook the area just south of the American border in the Baja California region (USGS). As one of the world's most seismically active countries, earthquakes have a major impact on everyone, including American citizens, in Mexico.
Earthquakes are not the only seismic hazards in Mexico, and the country also sees occurrences of landslides as well as liquefaction - where shaking causes soil to behave as a liquid temporarily.
Seismicity of Mexico (Esri, USGS, NOAA)
To review these seismic events, we ran scenario earthquakes at three different sites of historical earthquakes: El Mayor, Jalisco, and Michoacán using two different magnitudes similar to those of the infamous earthquakes at each site.
These sites also lie in areas with larger numbers of American citizens. The states of Jalisco, Colima, and Baja California and major urban centers such as Mexico City and Guadalajara have higher numbers of Americans.
While tourist destinations like Cancun on the east coast do host high numbers of American tourists, these areas experience earthquakes much less frequently than the urban centers in central and west Mexico. Additionally, the states where tourist destination are located tend to have fewer Americans overall than the states in northern and western areas of Mexico.
El Mayor
These scenario earthquakes replicated events similar to the 2010 El Mayor earthquake.
In 2010, the El Mayor earthquake caused violent shaking in cities near the epicenter and was felt in cities as far as Tijuana. Several landslides were mapped near the earthquake, and liquefaction occurred in the Colorado River Delta, near Mexicali, and Imperial Valley (USGS). With Baja California continuously being a common area for American citizens, future earthquakes in the region will likely have large impacts on them. It is rather fortunate that the 2010 event saw only 2 fatalities, and the next large event may see far more casualties unless citizens prepare ahead of time.
Jalisco
These scenario earthquakes replicated events similar to the 1932 Jalisco earthquake.
The 1932 Jalisco earthquake killed over 400 people and left thousands of buildings collapsed and damaged throughout the states of Jalisco and Colima. It could be felt from Culiacan all the way to Acapulco (USGS). There were likely many landslides and possible liquefaction events, though there is little recorded data from the time period. Seeing as how Guadalajara has grown and the region continues to have many Americans, it seems that an event resembling the 1932 incident would be disastrous for the area.
Michoacán
These scenario earthquakes replicated events similar to the 1985 Michoacán earthquake (also known as the 1985 Mexico City earthquake).
The infamous 1985 earthquake spelled disaster for Mexico City with casualty estimates ranging anywhere from 9,000-30,000 fatalities and another 30,000 injured. Nearly 20 million people felt the earthquake as it collapsed thousands of structures through several Mexican states (USGS). One reason Mexico City was struck so hard was due to the soft lake bed soil that it lies on which amplifies the waves through Mexico City and which led to both landslides and liquefaction during the 1985 disaster. The amplified shaking can be seen in the ShakeMap for the historical event.
Visualization of amplified waves through Mexico City area where darker reds correspond to more intense waves and ground shaking (New York Times, "Mexico City Was Built on an Ancient Lake Bed")
Fortunately, it seems from the scenario earthquakes that lesser magnitude earthquakes may not be as damaging to Mexico City due to the waves not being strong enough to reach it and be amplified. The same can not be said for the area surrounding the epicenter of the earthquake which would still see severe shaking and landslides.
Conclusion
Mexico sees dozens of earthquakes annually, and it is only a matter of time before the next major incident strikes. Landslide and liquefaction events have been recorded at the sites of several earthquakes and constitute dangers that citizens may not be aware of during or in the immediate aftermath of an earthquake. Though our scenarios certainly do not capture every seismic threat to Mexico, they do show what the extent of a single major event can be. Steps should be taken to mitigate the damage of these hazards to ensure that the next major earthquake does not devastate American citizens in Mexico.
