H-Bombs for Earthquakes

Nature's brute strength is never more frightening than during a major earthquake. The earth shifts with a sickening sway. Gaping fissures open in the ground. If the temblor strikes a populated area, roads may be torn up, buildings toppled and untold lives lost -- as happened in Northeast Iran last year, when as many as 22,000 people were killed in two successive quakes. Such destructive force seems as devastating as a man-made nuclear blast. Fascinated by the awesome similarity, three Uni versity of Miami seismologists have now proposed using the power of the atom to tame the mighty rumbles of the earth.

Nuclear detonations at strategic locations far below the surface, they suggest, could be used to keep earthquakes under control. The theory is based on the inherent characteristics of quakes.

Although their science is still in its in fancy, seismologists know that earth quakes are caused by gradual shifts of the earth's crust. As long as such movements are small and unimpeded, there is little danger of a quake. But strains inevitably build up along the fault line --the zone where the crust has moved from the rock adjacent to it. If these pressures become great enough, the crust suddenly breaks loose again, lurches violently and sends out shock waves in all directions.

Writing in Science, the Miami seismologists argue that nuclear devices might relieve the stresses before they go on the rampage. Exploded two to three miles underground at intervals of twelve to 30 miles along a fault zone, the bombs would set off a series of relatively small shocks. Properly timed, these jolts would jog along the crust ever so slightly to release the forces working against it. The blasts would, in effect, be seismic safety valves, letting off small but significant amounts of pressure whenever an earthquake threatened.

The idea presents enormous difficulties. Seismologists would have to know exactly where and when to explode the bombs--an art that still eludes them, although they may eventually be able to predict quakes by carefully calculating earth stresses. Still more delicate would be the decision on the size of the bomb. The Miami seismologists--Cesare Emiliani, Christopher G. A. Harrison and Mary Swanson--say that the job probably could be done by high-yield nuclear devices of one to ten megatons, presumably H-bombs. But other seismologists point out that an explosion meant only to keep the earth's crust moving slightly may, in fact, make it lurch violently--and actually precipitate a major quake.

Small Aftershocks. "The chances are small, but not zero," says Seismologist Lynn Sykes of Columbia's Lamont-Doherty Geological Observatory. He and other scientists think that a less dangerous method of earthquake control might be to pump liquid into a fault region. Such fluids would relieve stresses by acting, in part, as underground lubricants. Yet this method also poses dangers. In the Denver area, for example, recent shocks were apparently triggered by the disposal of chemical wastes in deep underground wells.

In defense of their scheme, the Miami scientists point to a recent study of the seismic effects of 21 underground nuclear tests staged by the Atomic Energy Commission in Nevada, a highly quake-prone region. Though each blast was followed by countless small aftershocks, none reached quake proportions and all were substantially weaker than the original explosion. The AEC is convinced that there is little risk in conducting such tests. It plans to follow up its recent controversial detonation of a 1.2 megaton H-bomb on Amchitka Island in the Aleutians, another major quake zone, with more powerful underground blasts. To the dismay of scientists, however, these explosions are designed by the AEC not for such peaceful purposes as quake control but only to test new military weapons.

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