Impacts of climate change on landscapes of the eastern Sierra Nevada and western Great Basin

AbstractPollen and algae from Owens Lake in eastern California provide evidence for a series of climatic oscillations late in the last glaciation. Juniper woodland, which dominated the Owens Valley from 16,200 to 15,500 cal yr B.P., suggests much wetter conditions than today. Although still wetter and cooler than today, the area then became fairly warm and dry, with woodland being replaced by shrubs (mainly sagebrush) from 15,500 to 13,100 cal yr B.P. Next, Chenopodiaceae (shadscale) increased, woody species declined, and lake levels fell—all evidence for a brief (ca. 100–200 yr) drought about 13,000 cal yr B.P. The climate continued to oscillate between wet and dry from 13,000 to 11,000 cal yr B.P. After 11,000 cal yr B.P., low lake levels and the increased dominance of desert shrubs indicate the beginning of warm, dry Holocene conditions. The region's climate was unstable during the Younger Dryas but uncertainities in dating prevent identification of the Younger Dryas interval in the Owens Lake record. Comparison of the Owens Lake record with studies in the Sierra Nevada and Great Basin suggest that the climate was generally wetter between 13,000 and 11,000 cal yr B.P., with warmer summers, although no consistent pattern of climate change emerges.

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A local-magnitude scale for the western Great Basin-eastern Sierra Nevada from synthetic Wood-Anderson seismograms

Bulletin of the Seismological Society of America ◽

10.1785/bssa0850041236 ◽

1995 ◽

Vol 85 (4) ◽

pp. 1236-1243

Author(s):

Martha Kane Savage ◽

John G. Anderson

Keyword(s):

Sierra Nevada ◽

Great Basin ◽

Magnitude Scale ◽

Local Magnitude ◽

Digital Network ◽

Original Definition ◽

Correction Curve ◽

Fitting Parameters ◽

Distance Correction ◽

Eastern Sierra Nevada

Abstract We have computed synthetic Wood-Anderson seismograms for over 1100 arrivals at 10 three-component, broadband digital stations in the UNR western Great Basin-eastern Sierra Nevada network. These represent all the available records from local earthquakes over magnitude 3.5 between 1990 and June of 1993, plus selected events of smaller magnitude. There were 77 events ranging in magnitude from 2.2 to 5.9, including four events over magnitude 5. The distances considered ranged from 15 to 600 km, with the best-represented range being from 30 to 450 km. We invert these measurements to determine distance and station corrections appropriate for a local-magnitude scale, constrained by Richter's original definition that an earthquake of ML = 3 will cause a 1-mm zero to peak deflection of the Wood-Anderson seismogram at 100 km from the epicenter. The results between 30 and 450 km were essentially independent of choice of curve-fitting parameters. In the 30- to 500-km distance region, the smooth distance-correction curves were very similar to that determined by Richter (1958), which is still used for southern California earthquakes. We propose to use Richter's distance-correction curve in reporting amplitude magnitudes from our digital network.

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