This is Scientific American 62nd Science.

I'm Julia Rosen.

Got a minute?

99 years ago, a magnitude 7.3 earthquake hit Puerto Rico.

It also caused a tsunami that swept through coastal towns.

All told, the shaking and flooding killed more than a hundred people and damaged many buildings and roads.

Now, scientists are getting a clearer picture of that tragic event thanks to an unexpected

source, century-old documents unearthed in an archive in the capital city of San Juan.

The documents were discovered by Bill McCann, a seismologist and

former professor at the University of Puerto Rico. McCann stumbled upon boxes of

repair petitions filed by residents of what was then a newly acquired U.S. territory, asking for aid after the disaster.

He later mentioned them to Roland LaForge, another semi-retired seismologist who told me why

he wanted to rescue the records.

You know, they're just sitting there getting moldy and nobody's ever looked at them.

And there might be some really useful information in there.

So the two researchers analyzed more than 6,000 documents, which turned out to be a

gold mine of information about the disaster and the damage it caused on a house by house basis.

They're very sad and poignant at times because lost family members.

They, you know, some people drown and they never found their bodies.

You know, you got a real feel for the suffering that these people went through.

In a newly published study based on the records, the researchers focused on the earlier estimates that the tsunami rose between three and four meters high,

inundating low-lying neighborhoods.

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