Disturbance of trees by the 1857 Fort Tejon earthquake, California.

Abstract

Trees may suffer damage during major earthquakes due to shaking or faulting of their substrate. Damage may result in temporarily asymmetric growth and/or reduction in width of annual growth rings. To determine whether trees contain useful records of prehistoric earthquakes in southern California, we cored eight conifers along the 1857 trace of the San Andreas fault near Wrightwod and Frazier Park, California. Annual ring widths were measured and plotted against the growth yeat determined by ring counting. We examined significant departures from normal growth trends and interpreted them in light of the 1857 earthquake and other possible environmental factors. Of eight trees sampled, five showed damage or growth anomalies attributable to the 1857 event. One 120-yr old tree straddling the fault is undamaged, suggesting no substantial slip since about 1870.-Authors