AEG OR Chapter April 16, 2019 Meeting
Hunting For Cascadia Triggered Landslides
PURCHASE OF TICKETS USING BROWN PAPER TICKETS: Ticket sales stops by Noon on Monday April 15th.
(At the door payments in Cash or Checks only.)
6:00 Social Hour
6:45 Dinner (Salad and Pizza)
Speakers: Bill Burns and Will Struble
Large magnitude earthquakes and climatic events in mountainous settings commonly trigger thousands of landslides, and these slope failures typically constitute a significant proportion of the damage associated with these events. Large, dormant deep-seated landslides are ubiquitous in the Oregon Coast Range (OCR), USA, yet a method for calculating landslide ages with accuracy required to diagnose a specific triggering event, includ-ing the 1700 AD Cascadia earthquake, has remained elusive. Establishing a compelling connection between pre-historic slope insta-bility and specific triggers requires land-slides ages with accuracy greater than that provided by 14C dating of detrital materials. Tree ring analysis is the only known method capable of determining landslide age with this accuracy. Dozens of landslide-dammed lakes in western Oregon present an oppor-tunity to use tree rings from drowned snags, or ghost forests, to establish the year of death, and thus landsliding. We crossdate tree ring indices from drowned Douglas-fir trees with existing live tree ring records from the OCR that exhibit synchronous, time-specific patterns due to regional climate variations. Our analyses determine that the land-slides responsible for creating Wasson and Klickitat Lakes occurred in 1819 and 1751 AD, respectively. 14C dates from selected tree rings and landslide deposit detritus are consistent with our tree ring anal-ysis, although the ages exhibit high variability, revealing the limitations of using 14C dating alone. Because dendrochronology provides annual accuracy of landsliding, sampling tree rings at ad-ditional landslide-dammed lakes throughout the OCR can be used to constrain the potential effects of ground motion and major climatic events on Cas-cadia landscapes.
SPEAKER No. 1 BIO: Mr. Bill Burns
Bill attended Florida State University where he earned his bachelors degree in geology and then Portland State University for his masters degree in geology. While working on his masters, he was a research assistant on a study of landslides impacting the Portland METRO from the storms of 1996-97. His masters thesis was on the Engineering Geology and Relative Stability of an area in Oregon City, Oregon.
Bill is a registered Professional Geologist (RPG) and Certified Engineering Geologist (CEG) in Oregon and Washington. He spent roughly 10 years consulting as an engineering geologist in Oregon and Washington before his current position as Landslide Geotechnical Specialist at the Oregon Department of Geology and Mineral Industries (DOGAMI). He has spent the last 15 years at DOGAMI working on research related to earthquake, landslide, and volcanic hazards in Oregon. He is the principal investigator at DOGAMI on landslide hazards and has authored many publications on landslide hazard mapping methodology, risk analysis, and maps. He has spent the last 25 years helping communities in Oregon understand and reduce risk from earthquake, volcano, and landslide hazards. Bill is also an active member of the Association of Engineering Geologist (AEG) and the Geological Society of America (GSA).
SPEAKER No. 2 BIO: Mr. Will Struble
Will Struble is a PhD Candidate in the Department of Earth Sciences at the University of Oregon. As a native of northern Nevada and Lake Tahoe, his fascination with landscape evolution stems from exploring the Sierra Nevada and Basin and Range at a young age. His research focuses on quantifying landscape response to seismicity in the Pacific Northwest, notably by dating landslide-dammed lakes in the Oregon Coast Range using dendrochronology. He additionally is studying the tectonic geomorphology of the Cascadia forearc over Neogene timescales. He received his BS in geology from the University of Nevada, Reno in 2016 where he worked on using the geomorphic expression of normal faults to predict slip rate. He is a recent recipient of the Lokey Doctoral Science Fellowship, and he spent summer 2018 at the University of Potsdam working on landscape evolution numerical methods. When not perusing Oregons ever-growing LiDAR dataset, he spends his time hiking and exploring the western U.S.
Old Market Pub (View)
6959 SW Multnomah Blvd.
Portland, OR 97223
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