Assessing active faults along the southeastern coast of South Korea
At the invitation of Drs. Sung-Ja Choi and Ueechan Chwae, both of KIGAM, I worked on marine terraces and active faulting along the eastern coast of South Korea from1999 to 2008. The project began as a result of a visit to the U. S. by Dr. Choi while I was directing a Keck Geology Consortium project along the San Andreas fault near Pt Arena in California. Along with co-directors Dr. Tom Gardner (Trinity University, Texas) and Dr. Carol Prentice (USGS), I was training students to identify and map marine terraces that are deformed and cut by faults that post-date the terrace formation.
A bedrock marine terrace forms as a wave-cut platform at sea level and the "inner edge" of that terrace approximates mean sea level, as in the example from near the Point Arena lighthouse in the photo I took at right. Eustatic sea level changes with time, so that wave-cut platforms are abandoned when sea level falls, as during cold, glacial times. With ongoing, moderate rates of uplift along the California coast, marine platforms are uplifted and gradually covered with a veneer of alluvium, colluvium, and sometimes eolian deposits. Finding and surveying the inner edges of marine terraces in the field, combined with mapping marine terraces from air photos, LIDAR, and other imagery, enables us to document amounts and patterns of fault-related deformation that has occurred since the time of terrace formation.
The results of this work are summarized at
Choi, S.-J., D. J. Merritts, and Y. Ota (2008), Elevations and ages of marine terraces and late Quaternary rock uplift in southeastern Korea, J. Geophys. Res., 113, B10403. doi:10.1029/2007JB005260