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Poster Abstracts
PLATE TECTONICS: A NEWLY COMPLETED EXHIBIT IN THE SAN BERNARDINO COUNTY MUSEUM’S
HALL OF GEOLOGICAL WONDERS (A-028)
K. Springer, E. Scott, and J.C. Sagebiel
The San Bernardino County Museum (SBCM) in Redlands, California is completing a suite of exhibits in our new Hall of
Geological Wonders. One of the first to be realized is “Plate Tectonics”. Throughout the Hall, the theme imbued in every
exhibit is the process of science, inviting visitors to ask us “How do we know?” In that vein, we have positioned the theory of
Plate Tectonics as the bedrock for all modern geologic studies and its development of the theory as one of the best examples of
the scientific method. We initially introduce plate tectonics to the public in a series of quotations, ideas and observations of the
earth from the likes of Aristotle, Native Americans, Darwin and Ben Franklin. The scientific method is introduced, explaining
that scientific inquiry strives to understand how things work, objectively and without bias. The exhibit then seques to quotes
from Wegener, Longwell, and Hess, finally culminating in “The Lines of Evidence”, displayed as a touchable scaled giant
bronze globe of the Earth’s topography along with mini globes that discuss continental drift (its rock and fossil evidence), seafloor
spreading and paleomagnetism, culminating in the unified theory of plate tectonics.
“Plate Tectonics” is the scaffolding for a suite of future exhibits on earthquake science that reveal the origin of southern
California’s striking topography and our most notorious geologic feature, the San Andreas fault system, as the culprit. Visitors
will observe the San Andreas Fault zone from our “Earth's Cylinder” – below ground in a re-created paleoseismic trench
across the fault, exhibited next to a Pallet Creek and a Wrightwood fault peel, and above ground from a viewing tower.
Visitors will experience a simulated earthquake in our immersive “ShakeOut Cabin”, while receiving earthquake
preparedness information. These exhibits explore the importance of science in everyday life, emphasizing science as a process
and encouraging visitors to become a part of this process. “Did You Feel It?” and the “Quake Catcher Network” are
interactives that simulate a real-time earthquake experience in a museum exhibit setting, and the “Active Earth” touch-screen
kiosk provides nested online information on earthquake science. Additionally, a video of SCEC researchers will inspire
visitors to explore science. This collection of exhibits will provide a unique introduction to scientific inquiry, earthquake
science and earthquake preparedness for our visitors.
A NEW AGE CONSTRAINT FOR A NEAR-FAULT PRECARIOUS LANDFORM IN CENTRAL OTAGO, NEW
ZEALAND (B-099)
M. Stirling, D. Rood, G. Balco, and A. Zondervan
In recent years, studies of precariously balanced rocks (PBRs) in New Zealand were focused on age determinations of features
at near-fault sites. Until recently, efforts to interpret exposure ages from Be-10 data on PBRs in central Otago, an area with an
equivalent climate to that of coastal central-to-northern California, were unable to resolve whether the rocks are of the order
10 3 -10 4 or 10 4 -10 5 years of age. Resolution of these age differences is critical to determining the utility of PBRs for constraining
seismic hazard models at long return periods. Reinterpretation of cosmogenic Be-10 data for “Clyde 6”, a near-fault PBR that
has had eight Be-10 analyses undertaken in recent years (and three additional analyses on nearby outcrops), is possible using
the methodology of Balco et al (2011). Samples collected from a vertical profile are used to interpret the rate of exhumation
and thus an age for the PBR. The dating method combines measured Be-10 concentrations with a numerical model that
accounts for nuclide production before, during, and after exhumation of the PBR from the subsurface. A three-dimensional
model constructed from photogrammetry is used to correct for the shielding of cosmic rays due to the shape of the feature.
Using all 8 Be-10 samples from Clyde 6 (and assuming zero rock erosion since exhumation), the results suggest that the
“tipping age” (time at which the rock was exhumed and free to topple) is ~40 ka. The best fit model is fairly well fit to
observed Be-10 concentrations, except for one sample; however, the misfit for this sample can be reduced if modest postexhumation
rock erosion (e.g. spalling) occurred at this sample location. The results also suggest that the feature sat in the
subsurface for a long time period, consistent with the site being part of an exhumed Tertiary peneplain (i.e., a landform
characterised by low rates of erosion). The interpreted age of Clyde 6 allows 4-6 Dunstan Fault earthquakes to have occurred
since the rock was exhumed. Combined with the fragility of the feature (alpha=6 degrees), these data suggest that ground
motions in these earthquakes did not exceed 0.11-0.14g (Stirling and Anooshehpoor, 2006) at this site.
2011 SCEC Annual Meeting | 237