January 17, 2013
Today is a day of significant quake anniversaries for the U.S. and Japan.
The last U.S. quake to kill more than a few people struck the L.A. suburb of Northridge 19 years ago today, in the wee hours of the morning. The San Fernando Valley was hit hard, but the whole L.A. area rattled violently, and seismic waves from The Valley were focused through the Santa Monica Mountains into the populous west side, an effect that’s apparent in the “Did-You-Feel-It” map if you’re familiar with the geography of L.A (click there for info if you aren’t. Or for fun if you are).
Damage was widespread and many of the area’s freeways shut down for months after major collapses when their concrete supports failed during the strong shaking. Despite the huge monetary cost (right between hurricanes Andrew and Katrina… and potentially behind Sandy) and moderate death toll, this was not Los Angeles’ “big one.” In the scheme of possible So Cal earthquakes, this was a relatively small one, and rather than hitting the core of the city, it struck a glancing blow by starting in the suburbs and sending most of its energy northward into the mountains. Nonetheless it is Angelenos’ clearest reminder (although its age must have erased it largely from modern relevance) of what to expect when a significant quake strikes the city.
Exactly a year later a quake of nearly the same magnitude struck a much more densely populated corner of the planet: Kobe, Japan. This quake, almost identical in magnitude to CA’s Northridge earthquake of the year before, is the source of that quintessential earthquake footage most everyone will be familiar with:
The Kobe quake’s death toll was two orders of magnitude higher than Northridge’s, and the damage to the port city was devastating, largely because of widespread liquefaction, an effect that was much less prevalent in the coarse sedimentary basins of Mediterranean L.A.
As we mark this anniversary of those significant earthquakes, as usual you should take advantage of this heightened awareness to double-check that you’d be ready were a similar quake to happen today. Let the commemoration serve to remind you that these were real events that really happened, and could happen again at any moment.