A 7.1 magnitude earthquake struck Mexico City on September 19th, causing at least 320 deaths and injuring around 5,000 people. This quake followed an even larger 8.1 magnitude earthquake off the coast of southern Mexico just 12 days prior. Earthquakes are common in Mexico due to the country's location along tectonic plate boundaries, and Mexico City is especially vulnerable because it was built on an island in a lake that has since been drained and built upon. The city's early warning system detected the initial tremors but the violent shaking still caused significant damage, occurring on the anniversary of a deadly 1985 quake.

1. EARTHQUAKES IN MEXICO
A powerful earthquake hit Mexico City on September 19. The ground
shook violently for about 20 seconds. The quake’s magnitude was 7.1.
The most powerful earthquake ever recordedwas 9.6. It struck parts of
Chile in 1960.
The earthquake near Mexico City followed an even bigger one 12 days
previously. The epicenter of this 8.1 quake was beneath the seabed
close to southern Mexico’s Pacific coastline. The epicenters of the two
earthquakes were about 400 miles (650 kilometers) apart. Both were
followed by further smaller tremors, or aftershocks.
Earthquakes are not unusual in Mexico and other countries in Central
America. Some areas of Mexico City are more vulnerable to earthquake
damage than others. This is because of the different groundthat they
are built on.
MexicoCity was the Aztec Empire’s capital. The Aztecs calledit
Tenochtitlán. They built the city on an islandin the middle of a large
depression, or basin, ringedby mountains. One, called Popocatépetl, is
an active volcano. It’s 43 miles (70 kilometers) from Mexico City, and
the country’s second highest mountain.
Spanish conquistadors, or soldiers, arrivedin Central America about
500 years ago. The Aztecs had never seen Europeans or large wooden
sailingships before. At first, they thought that the Spanish soldiers
were gods. The Spanish were amazedto see the gold in Aztec cities. In
their search for riches, they destroyed the Aztec civilization.
After destroyingthe Aztec city, the Spanish built on top of the ruins.
Over time, much of the lake was filledin and built upon. Today, Mexico
City is one of the biggest urban areas in the world. It and the
surroundingsuburbs are home to over 20 million
people.
Since 1900, there have been 34 earthquakes stronger than magnitude
7.0 near MexicoCity. Most earthquake deaths are caused by collapsed
buildings and fallingmasonry.

2. MexicoCity has an earthquake warningsystem. It detects weaker, initial
tremors. Loud warnings are broadcast through loudspeakers.
Normally, the violent shakingbegins about one minute after the
warning. When a warningsounds, people move onto the streets as
quickly as possible.
The September 19, earthquake struck on the 32nd
anniversaryof one of
MexicoCity’s worst quakes. About 10,000 people died on this day in
1985.
Nowadays, every year, a drill, or practice, is held at 11a.m. on this date.
Everyone leaves the buildings that they are in. The earthquake warning
sounded about two hours after the drill. This time it was for real. The
quake caused at least 320 deaths.
Around 5,000 were injured. The 8.1 earthquake, 12 days before, killed
over 90 people.