Linking Earthquakes and Geologic Time by Paleoseismology for General Education Earth Science

Friday 3:00pm-4:00pm
Poster Session Part of Friday Poster Session


Martin Farley, University of North Carolina at Pembroke
In teaching general education Earth Science lecture, I want to make connections between separate topics. One way I have done so is to create a paleoseismology activity that requires students to apply principles of relative geologic time to the record of prehistoric earthquakes. This activity is derived from Kerry Sieh's investigation of the San Andreas earthquake record at Pallet Creek, northeast of Los Angeles, using the simplified cross-section published by Susan Hough in her book Earthshaking Science (2002). Hough's figure shows a set of vertical ruptures caused by earthquakes in the Pallet Creek valley and horizontal peat beds. Students are first asked to decide what tools or principles would help work out the sequence of events. Some students want to immediately interpret the answer, but I tell them if you don't have a method first, then you can't get a reasonable answer. As a group, they gradually coalesce around the idea that superposition shows the fill of sedimentary layers in the valley and cross-cutting relationships shows how much fill had occurred when each rupture happened. They then can work out the sequence of the ruptures. The peat beds have radiocarbon dates; these can be placed into the rupture sequence by superposition and the students can evaluate earthquake numerical age and whether the earthquakes are evenly spaced or bunched.
I had not decided whether this activity could be used in the lecture or lab (most UNCP students do not take the lab). I discovered it could be done in a 50-minute lecture period, so I decided to do it in lecture. Finally, because Pembroke is in the earthquake hazard zone related to the Charleston 1886 earthquake, I describe the analogous but different approach (buried sand boils) for estimating recurrence interval for Charleston earthquakes.