Large Transverse Range Earthquakes Cause Coastal Upheaval near Ventura, Southern California

Slip on the Pitas Point thrust produces uplift and folding of the Ventura Avenue anticlinal (VAA) trend in the western Transverse Ranges of southern California. Rapid convergence has resulted in 2.7 km of uplift on the VAA over the past 200-300 ka, with as much as 320 m in the past 45-50 ka, indicating a long-term uplift rate of 6-7 mm/yr. Four Holocene emergent marine terraces are present between Carpinteria and Ventura, with the fourth terrace uplifted a minimum of 38 m. The most recent emergence event uplifted a Chumash Indian village at Pitas Point by 5-6 m about 950 yrs ago. The first terrace, which formed when the sea level was 0.5-1 m lower than at present, is nearly continuously preserved from east of Pitas Point toward the fold crest of the VAA, where its elevation increases, reaching an altitude of 7-8 m; this implies a large amount of slip on the causative fault at depth. Radiocarbon dates on marine shells and culturally derived charcoal indicate terrace emergence events occurred at about 0.95, 2.09, 4.4, and 6.7 ka.