water can rush through it sort of like a pier on the beach, and have the more solid information higher up. this, of course, works only as long as the tsunami is not bigger that you expected. if it's bigger, of course, your building is eventually going to collapse. >> what about the power of the water as it rushes in? that has to have a huge impact and determines whether or not your structure can withstand the force. >> that's dedefein dependent on water depths as it rushes in. as you've seen in the videos, the white waters on the horizon approaching, and debris-laden water rushing in, typically the water is moving at the speed of the wave is moving, which is digit to what you witness when you go swimming on the beach because there the water is moving slower than the wave is moving. >> this is important. i've had tweets about this. professor lou, help us understand this.