Scientists will be studying yesterday's Pacific-wide tsunami, such as it was, for months if not years.

But the reason why no big waves materialized may be as simple as the Slinky, the famous spring toy.

The phenomenon at work is called harmonic resonance.

As many remember, it takes a coordinated effort for two people at either end of a Slinky to get the spring vibrating in perfect rhythm.

If one or the other side gets out of sync, the Slinky devolves into an unruly ripple, without focus or coordinated energy.

That is apparently part of the reason for the small sea-level shifts here yesterday, said Gerard Fryer, a geophysicist with the Pacific Tsunami Warning Center.

“;We've always been a little nervous about Hilo (Bay), because Hilo gets into resonance so easily,”; said Fryer. “;In this particular case, the waves were 20 minutes apart and the natural resonant period for Hilo is 30 minutes, and that is why the waves didn't grow bigger there.”;

The 1960 tsunami from an earthquake near Chile, by contrast, sent in waves at perfect 30-minute intervals, so they built up in the bay rather than canceling each other out, he said.

Harmonics also played a part due to the subsea terrain, or bathymetry, around Oahu, said Fryer.

“;We saw waves with a set period and they decayed quite slowly,”; he said. “;Normally you would expect the first few waves to be big and the next few waves to be progressively smaller.”;

But the waves were consistent, steady—and not conducive to Slinky rhythm.

“;There are still some oscillations going on at Honokohau (Big Island) and other locations,”; said Fryer in the late afternoon. “;The tail end of this tsunami is still rattling around the islands.”;

The right energy in the right direction can be awesomely powerful. That was why wind was able to topple the Tacoma Narrows Bridge in Washington state.

When the bridge opened in 1940, it was the third longest suspension bridge in the United States, nearly 6,000 feet long and supported by two towers 425 feet high.

But on Nov. 7, 1940, winds of 35 mph over the course of three hours set the bridge to swaying. The wind then increased to 42 mph, setting up Slinky action in another direction. The problem got worse when a cable snapped.

The result: collapse.

Winds of a different speed or duration might not have set the critical harmonics in motion, scientists acknowledge.

Similarly, the 8.8-magnitude quake off Chile sent 500 mph seismic waves radiating across the Pacific. The main quake was followed by several aftershocks.

The waves were not unlike the wind on the bridge.

But the waves did not build up around Hawaii the same way the wind amplified the Tacoma bridge oscillations.

There were other factors in play, said Fryer.

“;This earthquake, although it was huge, didn't involve water as deep as we expected,”; he said.

The quake was also some distance from the plate boundary, known as the Peru-Chile trench.

“;The earthquake was back away from the trench, so it didn't actually move as much water as would normally be moved in an earthquake at this location,”; Fryer said. “;That made the tsunami a little smaller.”;