(Bloomberg) -- A series of quakes rattled Mexico City on Thursday, causing alarm among citizens used to tremors, sometimes with devastating effects. No damages were reported.
The quakes varied from those of medium magnitude, enough to trigger seismic alerts used to prompt evacuations, to very short ones. Mexicans tend to be especially alert in September, given that two earthquakes in that month in 1985 and 2017 were strong enough to topple buildings and kill thousands.
A magnitude 5.2 quake, coming from the state of Guerrero on the Pacific coast, lightly swayed buildings Thursday afternoon. The seismic alarm sounded in several parts of the city, leading to evacuations of office buildings and schools. Another magnitude 4.4 quake hit the state of Veracruz, in the Gulf of Mexico, but was imperceptible in the capital.
A separate set of seven, seconds-long earthquakes have shaken Mexico City since the early hours on Thursday. The first and strongest quake was a magnitude 2.5. Unlike other tremors that sway buildings in Mexico City and whose epicenter is located thousands of miles away, these quakes start in the capital itself.
‘Micro Quakes’
“Micro quakes,” as they are colloquially known, have become more noticeable in recent months for inhabitants of densely populated areas in one of the world’s biggest cities.
Alejandro Salazar Méndez, a geologist with the Instituto Politécnico Nacional, said the succession of micro quakes recorded on Thursday could suggest a swarm, defined as a sequence of seismic events occurring in a local area within a relatively short period.
Mexico City has several faults that criss-cross the valley area where it sits. There is a theory that after the 7.1 earthquake that shook Mexico City in 2017, some of these faults were “awoken,” Salazar said.
“Rock is very complex,” he added.
Because the areas where the micro quakes occur have thousands of residential constructions and offices, they are much more noticeable to people, as opposed to events happening in areas with small populations. In Mexico City in particular, people’s sensitivity to tremors has increased since the last major earthquake.
“There is a social component to this,” Salazar said. “After 2017 there is a lot more perception, a fear of them makes people become more aware.”
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