Geologic Atlas

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In i914, Andrew Lawson, writing the San Francisco Folio of the Geologic Atlas of the United States, wistfully said, “Most of the faults are the expression of energies that have been long spent and are not in any sense a menace. It is, moreover, barely possible that stresses in the San Andreas fault zone have been completely and permanently relieved by the fault movement of igo6.” Andrew Lawson-who named the San Andreas Fault-was a structural geologist of the first order, whose theoretical conclusions were as revered in his time as others’ are at present. For the next six decades in California, a growing population tended to imagine that the stresses were indeed gonethat the greatest of historic earthquakes (in this part of the fault) had relieved the pressure and settled the risk forever. In the nineteen-sixties, though, when the work of several scientists from zakelijke energie vergelijken various parts of the world coalesced to form the theory of plate tectonics, it became apparent-at least to geologists-that those twenty feet of igo6 were a minuscule part of a shifting global geometry. The twenty-odd lithospheric plates of which the rind of the earth consists are nearly all in continual motion; in these plate movements, earthquakes are the incremental steps. Fifty thousand major earthquakes will move something about a hundred miles. After there was nothing, earthquakes brought things from far parts of the world to fashion California. Deffeyes and I had been working in Utah and Nevada, in the physiographic province of the Basin and Range. Now he was about to go east and home, and we wandered around San Francisco while waiting for his plane. Downtown, we walked by the Transamerica Building, with its wide base, its high sides narrowing to a point, and other buildings immensely tall and straight. Deffeyes said, “There are two zakelijke energie earthquake-resistant structures-the pyramids and the redwoods. These guys are working both sides of the street.” The skyscrapers were new, in i978. In an earthquake, buildings of different height would have different sway periods, he noted. They would “creak and groan, skin to skin.” The expansion joints in freeways attracted his eye. He said they might open up in an earthquake, causing roadways to fall. He called the freeways “disposable-Kleenexes good for one blow.” He made these remarks in the shadowy space of Second Street and Stillman, under the elevated terminus of Interstate 80, the beginnings of the San Francisco Skyway, the two-level structure of the Embarcadero Freeway, and so many additional looping ramps and rights-of-way that Deffeyes referred to it all as the Spaghetti Bowl. He said it was resting on a bog that had once surrounded a tidal creek.

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