Geophysics

Sliding Under Lake Tahoe

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Science  13 May 2005:
Vol. 308, Issue 5724, pp. 927
DOI: 10.1126/science.308.5724.927d

The Great Basin of the United States is called that because, over the past 40 million years, the crust has been extending broadly. The locus of extension, which is characterized by faulting and volcanism, has moved from the center of the basin to its eastern and western margins, notably forming Death Valley, California. Along the western margin, the extension is complicated by its interaction with the San Andreas fault, a major strike-slip fault, and is now impinging on the Sierra Nevada Mountains (which have some of the highest elevations in North America).

Kent et al.have determined the recent extension at the margin in the Lake Tahoe area (on the border between California and Nevada) by dating and mapping offset shorelines and ancient avalanches into the lake. This history implies that the region is extending by about 0.5 mm/year, enough to produce a magnitude 7 earthquake approximately once every 3000 years. Such a quake could generate waves in Lake Tahoe approaching 10 m, or even much higher waves if the earthquake were to induce a slide into the lake as has happened in the past. — BH

Geology 33, 365 (2005).

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