Tsunami? In La Conner? Don't rule it out

Tsunami is a Japanese word for what used to be more appropriately called a “tidal wave.” In movies and television dramas, tsunamis are portrayed as monster ocean waves cresting over the likes of New York City or Los Angeles. A bit misleading to say the least.

Tsunamis are huge bursts of energy being transported in water. In reality, when a tsunami reaches land it’s much more like the tidal flood that invaded La Conner a few years ago, only bigger, much bigger.

As most folks have seen in YouTube videos of Japan’s 2011 flooding, a tsunami tide can be so massive it pushes boats, cars and all manner of other debris up town streets and topples any structure that dares to resist its thrust.

Bigger tsunamis are relentless. They flood, then recede to leave folks catching their breath and feeling a little relieved, only for the water to return with even more mass and force. Tsunamis can be awesome; a truly hard-to-imagine force of nature.

Think about the last time you tossed a rock in a pond or any body of calm water. The rock pushed water out of the way as it broke the surface. That disturbance sent a circle of ripples along the water’s surface as an energy wave. The ripples radiate in a circle. The 150-foot by 700-mile rock of a Juan de Fuca Fault rupture does the same. Some of its energy radiates west, traveling at the speed of a cruising passenger jet, and in hours surges ashore in Japan, Korea, Siberia and Taiwan.

Some of the energy radiates east and floods the coasts of Washington, Oregon and Northern California, literally drowning coastal communities in minutes.

I admit I don’t understand the physics involved with the ripples. I just haven’t spent enough time observing ripples from rocks tossed in pools. I have noticed though, the first ripple is not the biggest.

But are they a realistic threat to La Conner? Looking behind all the hand wringing attending the warnings about a “big one” on the Juan de Fuca subduction fault, I’d say no and yes – both based on science and geography.

I don’t find any evidence that a Juan de Fuca generated tsunami has or will pose a threat to La Conner. As such a giant force travels the Straits between Canada and the U.S., all the way to Puget Sound, its energy will be sapped, and when it finally reaches the more open waters of the Sound, its remaining energy will be dissipated by spreading through the Sound.

However, there is another possible source of a local tsunami – the Seattle Fault that crosses Puget Sound. Mud core evidence collected at the edges of the Sound points to a 6-foot tsunami type event happening about 900 BC. The fault is well studied. A rupture occurred on the fault then with a displacement of 27 feet. The body of water over the fault is puny compared to the Pacific Ocean, but it apparently was massive enough to absorb the quake’s energy and radiate same. Any flooding that may have attended that event remains to be documented.