New Evidence of Prehistoric Lowcountry Earthquakes Pradeep Talwani, the Director of the South Carolina Seismic Network and Professor of Geophysics at the University of South Carolina, recently (June 2007) opened an exploratory trench at Colonial Dorchester State Park (http://www.southcarolinaparks.com/park-finder/state-park/725.aspx ) to look for evidence of earthquake-related ground movement near Old Fort Dorchester. Records from August 31, 1886 M = 7 earthquake indicate that the walls of the fort were cracked by ground movement during the event. In this trench Doctor Talwani and colleagues discovered a sand blow (pictured to the right), a feature formed when an underground wet sand layer liquefies during earthquake shaking and the sand and water mixture is ejected from the ground. Hundreds of these features dotted the Lowcountry landscape after the 1886 earthquake. In the trench wall the sand blow appears as a wine glass shaped layer of white and yellow sand above a layer of red and gray clay. Geological and archeological evidence from trench indicates this particular sand blow occurred before the settlement of Colonial Dorchester, since bricks and other human artifacts lie only in the upper gray soil above the sand blow. Doctor Talwani and colleagues are currently looking for geologic material that can be dated in the trench wall, to determine when the earthquake that created the sand blow occurred. Also see the Post & Courier newspaper story: http://www.charleston.net/news/2007/jun/12/old_sand_geyser_shows_quakes_part_life_here/ For more information, contact Dr. Steven Jaume, (843) 953-1802, jaumes@cofc.edu.
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Last Updated: July 2, 2008 Curator: hallcr@cofc.edu	Sponsored by: SC Emergency Management Division