The national media and local newspapers and television in several cities well outside the California earthquake area have made much in the past week of the fact that a quake could happen elsewhere, asking should state, local and federal authorities do something about that risk. For most of the nation those cries are largely "the sky is falling" journalism. This week earthquakes, a year ago global warning, who knows what tomorrow.
Responsible structural geologists have pointed out, and many academic and federal reports make clear, that the possibility of severe earthquakes outside of known seismic zones is so remote as to be not worth human worry.Even where low-intensity quakes have sometimes been felt, as in the northeast, they are not believed by any mainstream geological authority to be precursors of 6- or 7-point Richter temblors. Most earthquakes in New England and elsewhere in the northern U.S. result from the Earth's crust's continued rebounding from the weight of the ice-age glaciers that pressed down with millions of tons of pressure. Ice sheets 10,000 feet thick covered the land as far south as Illinois and New Jersey as recently as 5,000 years ago, according to the geological record. The creaks and groans as the Earth continues to recover do not pose any real threat of severe damage.
It would be far better to concentrate public and government earthquake protection efforts where it is really needed, in states like California, Alaska and - Utah. The Wasatch Fault, which most Utahns realize runs down the western side of the Wasatch Front, is a clear and present danger. Thousands of feet of movement on the Wasatch and associated faulting have occurred within relatively recent geologic history. Salt Lake City is almost as likely to have a severe earthquake in the foreseeable future as is California.
Elsewhere, notably in the New Madrid, Mo., area, 100 miles north of Memphis, Tenn., and near Charleston, S.C., severe quakes have occurred within the past 150 years. Though the mechanisms that caused those quakes are not well-understood and both areas seem seismically quiet now, there are no ongoing low-level earth tremors that suggest they are likely to recur.
In most of the rest of the U.S., earthquakes are possible, but the return of the ice age is just about as likely. The same ice that dammed outflow channels and raised the Great Salt Lake some hundreds of feet to the Lake Bonneville level melted only recently, geologically speaking. The ice advanced and retreated more than a dozen times in the Pleistocene Era, with warm interglacial periods far longer than the time since the ice most recently disappeared. The causes of such severe climatic changes are not at all well-understood, though clearly they antedated man's interference.
Some anti-nuclear activists have publicized fault zones near sites where atomic power plants have been proposed, suggesting that a real possibility exists for earthquakes in many states. While prudence might suggest not building nuclear reactors atop faults, many of the faults have not been active for millions of years. Some are found at depth, covered by other rock layers that have lain unbroken for eons. Many are in areas such as the Appalachians which were thrust up early in the Earth's history and are not under continuous pressure like the continental plates that grind together along the San Andreas Fault.
It is always prudent to take possible earth movement into account when building any structure. Landslides like that at Thistle, Utah, and floods such as undermined a New York State Thruway bridge three years ago, are possible almost anywhere. Movement where mining or petroleum production has undermined the surface is relatively common.
But to spend money and effort on safeguards against possible but unlikely disasters is to take that effort away from areas where they are likely. It would be a waste of the nation's limited resources.