National Geographic : 1990 May
against each other and were of different heights," said Helmut Krawinkler of Stan- I i.. ford University. "This gave them different periods of vibration and caused them to butt against one another. Some pounded each other to ruins. Sometimes the shorter building, with the quicker movement, dislodged the taller building's side wall, and it fell on the short structure. Unreinforced masonry buildings are death traps and should be reinforced whenever possible." With Santa Cruz residents Bob and Jean Holston I drove up into the mountains, toward the dark peak named Loma Prieta. On a mountain shoulder, Lee and Terry Peterson's house still stood, but its spine was broken. I walked around a small moving van and stuck my head inside the house. Immediately I felt disoriented. The floors sloped off, each room at a different angle. Walls tilted. Only a chandelier, hanging like a plumb bob, indicated a true direction. Walking unsteadily to the kitchen, I found Mrs. Peterson sorting things to be saved, things to be cast out. Mr. Peterson and their friend John Everett were eyeing a huge refrig erator, one of the last items yet to be removed. I uttered my sympathies. "It's just a house," said Mrs. Peterson cheerily. "We still have our lives, our pic tures-I still have my wedding dress." She paused. "This place is still settling. If you hear a creaking, go for a door." I helped tilt the refrigerator onto a dolly. From kitchen to door, the floor slanted uphill. We put our (Continued on page 96) CHARLES O'REAR, WEST LIGHT On shaky ground, Robert Brown of the U. S. 24 GeologicalSurvey photographsa sand boil that burst up through a mud flat south of San Francisco. The phenomenon results INTERSTA from a process called liquefaction, treacher Two-tiered section ous to buildings. In an earthquake, loose of 1-880 was built and saturated sandy layers become like atop mud and fill quicksand, with virtually no strength to that amplified s - support structures as the ground heaves. deck smash UpThrough weak spots in the soil, sand boils vehicles below, erupted into basements, yards, and streets killing 42. atop man-made fill where San Francisco d dand Oakland grew both before and afterthe 1906 earthquake (left). Built on fill, the Marina district was heavily damaged. There, some sand boils acted as time capsules, ironically spewing fragments of 6 buried redwood and other debrisfrom the 1906 quake used as fill.