Only two months after the devastating earthquakes that struck central Italy in September, part of the famous Basilica of St. Francis in the town of Assisi is once again open to the public. The region was devastated on September 26 by two earthquakes measuring 5.5 and 5.9 on the Richter scale. Scientists and engineers working to strengthen the Basilica are learning lessons useful for anyone living in an earthquake zone. Each time a strong earthquake hits a particular area, scientists take seismic measurements that are analyzed to predict how severe future earthquakes might be and how often they might occur.
Engineers also use the information to learn more about the kinds of damage an earthquake can cause.
With measuring instruments inside buildings and on the ground nearby, researchers compile a record of how a building moves during a quake. This data is then used to refine methods of strengthening older buildings and constructing new buildings to withstand strong earthquakes. In 1989, for example, the 7.1 Loma Prieta quake rattled the Santa Cruz mountains in central California. Sixty miles away, in downtown San Francisco, people inside the 49-story Transamerica tower were shaken for more than a minute. Instruments showed that the top floor swayed more than a foot in either direction, according to measurements taken by the USGS after the quake.