Yamada, Japan (CNN) -- Just over a month after the worst natural disaster in modern Japanese history, scientists and researchers are still trying to piece together the mystery of exactly how and why some areas were wiped out by tsunami and others escaped.

International teams of geologists are mapping out the geological causes and complex effects of the March 11 tsunami waves triggered by a magnitude-9.0 quake off the eastern coast of Japan.

First moments of the tsunami

More than 13,000 people died in the tsunami and another 14,000 are still missing and feared washed to sea, including a dozen residents of Yoriso in Miyagi prefecture.

The small fishing village juts out on a peninsula, making it the closest populated point to the epicenter of the quake, and one of the first places to be hit by the tsunami waves.

Rumi Endo, a 17-year-old high school student now sheltered in the village elementary school recounted the terror she felt after rushing to high ground as the tsunami siren sounded.

Japan marks one month since quake, tsunami

"I had never imagined such a thing happening," she said as she showed a video taken on her cell phone, powered by a hand-cranked generator. "I was scared to death."

She said that a total of four waves crashed through the concrete breakwater sheltering the cove. In her video she is screaming as one wave picks up a family member's home and carries it careening far up the hill.

It's the job of teams like that led by Akio Okayasu to figure out just how high those waves got, so experts can help design new defenses against future tsunamis.

Up the coast in the town of Yamada, the professor of engineering at the Tokyo University of Marine Science and Technology measured wave heights of more than 15 meters in some spots.

But some other locations in the same bay look virtually untouched, with waves under half that size.

Wearing hard hats and heavy boots, the teams scramble up cliffs and comb through shattered buildings.

They're scanning for clues such as dirty water lines near the roofs of two-story warehouses and floating fishing gear tangled in power lines that give them a hint of the destructive power of the waves.

They use sophisticated laser pointers, computers with global positioning systems and towering measuring sticks to log the wave heights and strength.

Associate professor of engineering at Georgia Tech Hermann Fritz specializes in monitoring tsunamis. He's conducted field studies of a dozen, including the one off the Indonesian coast in 2004 that killed over 200,000 people.

Still, he was stunned by the amount of debris and the ultimate height of the latest tsunami.

Tsunami aid: How you can help

The survey teams have registered run-up heights of nearly 38 meters, or 124 feet, while tsunami waters rushed up to 10 kilometers, or six miles, inland in some places.

In Yamada, the town had just completed a new 7-meter-tall concrete tsunami wall with thick steel gates built to be slammed shut in case of an alert.

The new walls appeared to have held against the initial battering. But the tsunami waters rushed around the older sections on the edges, engulfing the town and then knocking down some sections as the water flowed back to the sea.

Okayasu says that just like a modern computer, in the effort to design new defenses hardware is just part of the solution: software is also needed.

He says that studies like his will help to show where walls need to be built higher or stronger.

But he also warns that rebuilding needs to be done smarter, with easier roads for evacuation, and tall, strong towers for people to gather in.

Okayasu says there also need to be improvements in how people and governments cope with evacuations and disaster planning.

"We can expect another big quake and tsunami to hit within 30 years, maybe in western Japan or somewhere else in the world," says Okayasu.

Words of hope for Japan

"Our final goal here is to help not only Japanese but also other people in the world avoid disaster."