Claudia Jean Falenski, age 15, of Natrona,, Pennsylvania, for her question:

What is the Richter Scale?

The energy of a major earthquake may be 10,000 times greater than the early A bomb. When it strikes in some faraway place, we hear about it within hours and soon see fleeting TV pictures of the damage. Meantime our rescue planes have left to aid the stricken victims. Sometimes we get a chance to help with personal donations of food, clothing and such. With our concern for the victims we wonder how bad it was and also how big it was. After a few days, we get a Richter Scale rating which tells us how big it was in comparison with other major earthquakes.

The surface damage to rocks and buildings is earthquake intensity. It may be rated on the Mercalli Scale of Earthquake Intensity, 1n Roman numerals. The size and scope of the entire crustal upheaval is earthquake magnitude. It is rated on the Richter Scale of Earthquake Magnitude, in ordinary figures and decimals. Intensity tells us how bad it was in a certain area. Magnitude tells us how big it was in relation to the earth.

Earthquakes are triggered by crustal upheavals, sometimes 100 miles below the surface. Their trembling vibrations sweep around the world and also down through the globe. Worldwide seismology centers have super sensitive seismographs that monitor these vibrations, moment by moment. They are recorded in zig zag lines. Data from far flung centers is compared to pinpoint the center of a medium or major quake.

In 1935, Charles Richter worked out a system to measure the relative magnitudes of earthquakes occurring anywhere in the world. When a quake occurs, seismograph and other records are gathered from several centers in and near the region of upheaval. All this material is assembled and compared. When different centers show slight variations, average figures are taken.

All these estimates are matched against figures on standard charts and tables. The final answer is based on the degree of earthquake activity at a distance of 100 kilometers from its epicenter. The figures on the Richter Scale are not so simple as they look, for they are based on logarithmic tens.

For example, a monstrous earthquakes of magnitude seven is ten times greater than a major quake of magnitude six. Magnitude six is ten times greater than magnitude five. There is an enormous difference between one whole number and the next. For this reason, most earthquake magnitudes fall between the whole numbers. They are rated is decimals as, for example, 6.2 or 5.8.

There is no limit to the possible categories on the Richter Scale. But thank goodness the top records are no higher than eight or nine, and upheavals of these dimensions are very rare. On the Richter Scale, the magnitude of a major monster is 100 million times greater than the constant little shivers that constantly go on in the earth's restless crust.