Fact Sheet 176-95
California Division of Mines and Geology
California Institute of Technology
Pacific Gas and Electric Company
University of Puerto Rico, Mayaguez
U.S. Army Corps of Engineers
U.S. Bureau of Reclamation
U.S. Department of Energy
U.S. Department of Veterans Affairs
Many smaller agencies
Private building owners
Over the past 30 years, scientists have put together a more complete picture of how the ground shakes during earthquakes. They have learned that shaking near the source of earthquakes is far more severe than once thought and that soft ground shakes more strongly than hard rock.This knowledge has enabled engineers to improve design standards so that structures arebetter able to survive strong earthquakes.
When the 1989 Loma Prieta earthquake struck, 42 people tragically lost their lives in the collapse of a half-mile-long section of the Cypress structure, an elevated double-decker freeway in Oakland, California.Yet adjacent parts of this structure withstood the magnitude 6.9 temblor—why? The part that collapsed was built on man-made fill over soft mud, whereas adjacent sections stood on older, firmer sand and gravel deposits. Following the collapse, scientists set out instruments in the area to record the earthquake's many strong aftershocks. These instruments showed that the softer ground shook more forcefully than the firmer material—even twice as violently.
First posted March 23, 2001
For questions about the content of this report, contact Mehmet Çelebi
For additional information, contact:
Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.
Çelebi, Mehmet, Spudich, Paul A., Page, Robert A., and Stauffer, Peter H., 1995, Saving Lives Through Better Design Standards: U.S. Geological Survey Fact Sheet 176-95, 2 pp., http://pubs.usgs.gov/fs/1995/0176/.