25 years since Loma Prieta25 years ago tonight, like many people around the United States, I sat dow

25 years since Loma Prieta25 years ago tonight, like many people around the United States, I sat down after dinner and tried to turn on a game of the World Series between the Giants and the Athletics – teams based in San Francisco and Oakland. I quickly discovered that game wasn’t happening any time soon; a major earthquake had struck the areas where those 2 teams are based just moments before the game was to start.The Loma Prieta earthquake would up as a surprise in many ways. The Bay Area hadn’t been struck by a large earthquake in the memory of most of its inhabitants; suddenly it had to deal with the results. Building codes and designs for things like highways and bridges that were thought to be adequate turned out to be woefully weak, leading to collapsing of structures like the double-decker Nimitz freeway, which pancaked downwards, trapping and killing those on the lower deck.One of the stories of this quake that always struck me was the lack of preparation for fire despite the legacy of huge fires after the 1906 Earthquake. Fed by broken gas and electricity lines, fires broke out all over San Francisco, particularly in the hard-hit Marina district that sits atop loose sediment that magnified the shaking. Had the city of San Francisco not purchased a fire boat that was able to pump water from the bay itself into the city just before this disaster, its possible the entire Marina District could have burned to the ground.Loma Prieta actually struck far from San Francisco and away from the most famous faults in the area. The fault is close to the San Andreas, but is actually one of many smaller faults in the hills and mountains surrounding these cities. The fault generated compressional forces in that area, squeezing the ground and deforming this formerly in tact drain covering (just thought that was a cool image). As a consequence, scientists have put extra effort since 1989 into understanding the power of these faults and their ability to impact cities.Engineers have also realized that building codes need improved. As I said yesterday during the shakeout drill: the old saying is that earthquakes don’t kill people, buildings do. That held true in Loma Prieta, and since that quake building codes in these cities have continued to improve.San Francisco is not off the hook. It’s been over 100 years since the San Andreas last moved, which means another event on that fault is entirely possible. The Hayward fault runs directly through San Francisco Bay and Oakland and is a second major strike-slip fault in this area as part of the same system. On top of that, there are potentially thousands of smaller faults in the mountains surrounding these cities capable of producing earthquakes on the scale of Loma Prieta.The USGS estimates that San Francisco has a 2 in 3 chance of experiencing a Loma Prieta sized earthquake or larger in the next 30 years. It will happen again, it’s just a matter of time and preparation.-JBBImage credits:http://upload.wikimedia.org/wikipedia/commons/4/4a/NimitzFreewayRibbonLomaPrietaQuake.jpghttp://pubs.usgs.gov/dds/dds-29/screens/053sr.jpeghttp://earthquake.usgs.gov/regional/nca/1989/Read morehttp://pubs.usgs.gov/fs/2014/3092/pdf/fs2014-3092.pdfhttp://www.sciencedaily.com/releases/2007/09/070926191844.htm -- source link

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