Stephanie Shields, age 8, of Omaha, Net., for‑‑her question:

Why do earthquakes happen?

At a quarter to noon, on March 22, our old Andy got shaken up in an earthquake. He was sitting in his chair writing you‑know‑what when suddenly a load of big books tumbled out of the bookcase into his lap. A statue of the Roman goddess Diana fell down and broke off her head. Mrs. Rama‑Pooka, Andy's white cat, scooted off and climbed up the chimney. For the ground was shaking sideways and up and down and everything ‑ everything was jolted along with it.

This, of course, was the recent earthquake of the beautiful city of San Francisco. It was a fairly bad one. Windows were broken, a few chimney pots fell and all the cans and bottles in Andy's favorite supermarket were shaken onto the floor. The upset lasted about a minute ‑ no one was hurt seriously. Mrs. Rte,‑na‑Pooka lot Andy wash her white again, the statue was mended and things were soon back to normal.

The earthquake was caused by masses of heavy rock rumbling and tumbling about miles below ground. In some places, the deep layers of the earth's crust are cracked, buckled and piled all higeldy nigeldy, Like a pile of badly balanced building blocks, they arc likely to topple. When this happens, the upset is felt by the surface layers over the up heavel. The ground shakes, shifts and sometimes cracks open in fissures.

Such an area of topsy turvey underground layers of rock is called a fault in the; earth's crust, As you would expect, it occurs where the surface is uneven. Faults follow the line of high mountains beside ocean deeps and earthquakes haunt the faulty regions.

One earthquake belt, at the foot of the Himalaya ridge, runs along the Mediterranean region. Another runs along the high mountains that border the western shores of North and South America. The San Andreas, the most active fault in the world, is in this region. It begins up north, under th(; Pacific Ocean, moves into California just north of San Francisco, runs south to the Salton Sea and maybe into the Gulf of Mexico.

Around  San Francisco, the San Andreas fault wrinkles like an old apple into several faults. Any one of them can shrug its shoulders and shake the city. The recent one registered 5.3 on the earthquake scale and shocked the needle of the recording instrument out of use:. There were sizeable quakes before and after the big one. For it takes many shakeups before the tumbled rocks below ground are settled again.

The year 1906 is remembered for a far more severe quake that shook San Francisco. Gas mains were broken and the city burned. It was rebuilt with special mains and a plentiful supply of fire fighting water. And this time the city was ready to defend itself from the worst danger of an earthquake ‑ which is fire.