The study of past earthquakes, paleoseismology, is important because the historical record is too short to indicate how often disastrous earthquakes occur. Thus, paleoseismology can identify previously unkown events and pinpoint locations of known and unknown earthquakes.
The paleoseismic record can add important information about prehistoric earthquakes events and thus aid in estimating future earthquake hazards.
Old trees that have been damaged by earthquakes can record evidence of prehistoric earthquake disturbance in their annual growth rings.
To understand the tree-ring record we must study the effects of known earthquakes on tree rings.
These are termed analog studies. Analog studies help us to understand the tree-ring record of earthquakes.
By identifying patterns in analog studies, we can look at the record from annual rings of older trees for the same type of evidence for earthquake disturbance.
A table of the types of evidence found in trees that can be related to seismic activity can be found here.
One good example is the effects of the 1964 Alaskan earthquake, the largest historical earthquake in North America.
The power of paleoseismology was shown in a study on the San Andreas fault in California. It revealed a previously unrecorded earthquake in 1812.
Finally, here is some work in progress from a Redwood Forest outside of San Francisco.
Jacoby, G.C. 1997. Application of tree-ring analysis to paleoseismology, Reviews of Geophysics 35 (2) 109-124.
Jacoby, G. C., D. E. Bunker, and B. E. Benson. 1997. Tree-ring evidence for an A.D. 1700 Cascadia earthquake in Washington and northern Oregon, Geology 25 (11) 999-1002.
Jacoby, G. C., G. Carver and W. S. Wagner. 1995. Trees and herbs killed by an earthquake ~300 yr ago at Humboldt Bay, California, Geology, 23, 77-80.
Jacoby, G. C., P. L. Williams and B. M. Buckley. 1992. Tree-ring correlation between prehistoric landslides and abrupt tectonic events in Seattle, Washington, Science 258,1621-1623.
Jacoby, G. C. 1989. Overview of tree-ring analysis in tropical regions, Int'l. Assoc. of Wood Anatomists Bull. 10,2, 99-108.
Sheppard, P. R. and G. C. Jacoby. 1989. Application of tree-ring analysis to paleoseismology: two case studies, Geology 17, 226-229.
Jacoby, G. C., P. R. Sheppard and K. E. Sieh. 1988. Irregular recurrence of large earthquakes along the San Andreas fault: evidence from trees, Science, 241, 196-199.
Jacoby, G. C. 1987. Potentials and limits for dating prehistoric earthquakes using tree-ring analysis, 18-22 in Crone, A. J. and E. M. Omdahl, eds. Directions in Paleoseismology, U.S.G.S. Open-File Report 87-673, 456 p.
Jacoby, G. C. and L. D. Ulan. 1983. Tree-ring evidence for uplift at Icy Cape, Alaska, related to 1899 earthquakes, Jour. Geophys. Res. 88, 9305-9313.
If you are interested in tree-rings and seismic activity, please contact Dr. Gordon Jacoby at druid@ldeo.columbia.edu or click on the picture!
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