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Why Mexico is at the epicenter of the month’s most prominent natural disasters

A 7.1-magnitude earthquake struck central Mexico on Sept. 19, killing at least 200 people. (Video: The Washington Post)
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About two weeks ago, Hurricane Katia made landfall near Tecolutla, Mexico, about 200 miles east-northeast of Mexico City. It was only a Category 1 storm when it landed — relatively tame compared with the landfall of Hurricane Irma, which was whipping through the Gulf of Mexico at the same time. Nonetheless, two people were killed by the storm.

That was on Sept. 8. A few hours earlier, a massive earthquake shook the country farther south, killing more than 60 people. That quake, though, was nothing compared with the one that struck the nation’s capital Tuesday. That quake killed more than 200 people, crumbling buildings and crippling much of the city.

September has, in one sense, been an unlucky month for Mexico. But there are few places on the planet besides Mexico where the bad luck of a severe earthquake and a hurricane might actually converge.

The National Oceanic and Atmospheric Administration tracks tropical cyclone activity around the globe. Each and every recorded storm has been plotted out, so we can see where hurricanes take place. That pattern looks like this:

(Click the image to view a larger version.)

Tropical cyclones (of which hurricanes are a more severe example) tend to originate just north and south of the equator. In the Atlantic basin, the baseline pattern is westward movement into the Caribbean and Gulf of Mexico followed by a turn to the north and east. In the map above, the severity of the storm (indicated by wind speed) is indicated with a darker line with storms that pass over the same territory also deepening the red.

Notice what happens around Mexico: A number of sections of dark red, both to the west and east of the country.

Now we overlay the boundaries of the Earth’s tectonic plates, the shifting continental boundaries that often spawn earthquakes where they meet. Along Mexico’s western coast lies the boundary of the Cocos plate and the North American plate. The motion of the Cocos plate sliding under the North American plate creates earthquakes, like the one this week.

While Mexico is certainly a place where cyclone activity and fault lines intersect, it’s not the only place. Notice Southeast Asia, near Japan. There, too, a similar problem arises.

Those maps, though, simply suggest where big storms and big earthquakes might happen. Here’s where they do happen, looking at hurricanes (or cyclones with hurricane-force winds) and earthquakes that registered at least 6 on the Richter scale since 1980. Red-purple blocks are locations of hurricanes, with darker colors indicating stronger or more frequent storms. Blue dots are earthquakes, with darker colors indicating — you guessed it — stronger or more frequent quakes.

(These maps indicate any degree of latitude and longitude where such a storm or earthquake occurred.)

We’ve zoomed in on the two regions mentioned above. Again: These are places where there have been hurricane-force winds and major earthquakes since 1980.

There are places that have seen both a serious earthquake and a hurricane-strength storm since 1980. Where? Near where the earthquake hit Mexico earlier this month, for one. There are more such locations in Southeast Asia, but the combined strength of the storms and earthquakes near Mexico were more severe.

Here’s the kicker: All of those places on the above map had major storms and major earthquakes in the same year.

In that sense, Mexico’s bad month isn’t all that unusual — at least for Mexico.

Major storms and earthquakes, by decade. Hurricane activity is through 2016.