Ventura Highway

Steve's picture

I recently attended a scientific meeting and listened to a well-known geologist discuss new findings about earthquakes near Ventura, California. He suggested that several faults buried under the mountains north of town might "link up" to make an earthquake far larger than would separate quakes on the individual faults. Turns out, the uppermost arm of the link lies under the Santa Barbara Channel parallel to the coast west of Ventura. As visualized, an earthquake on this multi-fault monster could uplift the sea floor and coast north of the fault by eight meters and down drop the sea floor and coast south of it by about one quarter of that.

My ears perked! Whenever I hear of misbehaving seafloors, I picture -- tsunami.

As I imagine it, within a minute, the quake pushes up a 90 km long ridge of water maybe six meters high. Within five minutes, the water ridge collapses under its own weight and divides into two opposite traveling waves that strike off to do their worst.

What did we learn from the simulation? Well, because the coast to the right uplifted along with the water, it should be fairly safe from the wave heading that way. On the down thrown side of the fault, the Oxnard coast faces more serious issues with inundation.

Scientists have been digging in the area's sloughs and tidal flats for evidence of past tsunami that left signature in layers of sand and soil. So far, no one is sure how often these multi-fault menaces visit, but once in 5,000 years might be close to fact.

The possibility of a southern California tsunami shouldn't stop you from renting that red convertible, dialing AMERICA tunes on the radio, and cruising down the Ventura Highway. Just in case of a really wet trip however, I'd go ahead and accept the damage/collision wavier on that rag top.

Steven N. Ward, Santa Cruz

Risk Alert