Logs and Data From Trenches Across the Berryessa Fault at the Jerd Creek Site, Northeastern Napa County, California, 2011-2012

摘要

The primary purpose of this report is to provide drafted field logs of exploratory trenches excavated across the Berryessa Fault section of the northern Green Valley Fault (Lienkaemper, 2012; Lienkaemper and others, 2013) in 2011 and 2012 that show evidence for at least one surface-rupturing earthquake in the past few centuries. The site location and site detail are shown on sheet 1 (figs. 1 and 2). The trench logs are shown on sheets 1, 2, 3 and 4. We also provide radiocarbon ages (table 1) used for chronological modeling of the earthquake history and a field description of a soil profile in one trench (appendix). A formal report based on these logs and data is in preparation. The approximate location of the west trace of the Berryessa Fault, a northern section of the Green Valley Fault, is identified in the vicinity of the trench site primarily by aerial photo interpretation of its geomorphic expression (Lienkaemper, 2012) and more precisely at the site from its exposure in trenches. The trench site (sheet 1, figs. 1 and 2) lies in an alluviated valley formed by the dextral fault offset of Jerd Creek, and primarily comprises residual soils and colluvium at the valley margins, and within the valley, alluvial fan, stream and debris flow deposits of late Pleistocene and Holocene age.