People walk through the rubble following an earthquake in San Francisco in this April 18, 1906 file photo. On April 17, 1906, San Francisco was cosmopolitan enough to host Enrico Caruso in "Carmen" and so financially flushed it ranked fourth among American cities in raising money to help victims of a volcano in Italy. A day later, San Francisco was pleading for help itself after a giant earthquake struck along the San Andreas fault. (AP Photo/File)