May 10, 2017

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Brian Penserini Published in Geomorphology Journal

Brian Penserini (Massachusetts) co-authored and article entitled "A morphologic proxy for debris flow erosion with application to the earthquake deformation cycle, Cascadia Subduction Zone, USA" that was published in the journal Geomorphology volume 282, pages 150-161 on April 1, 2017.

The paper concerns work that Brian and his team performed using airborne LiDAR data of the western Oregon Coast Range. They developed an empirical model to relate the morphology of valleys scoured by periodic debris flows to erosion rate. Using this model, they estimated erosion rates for 83 small catchments solely from LiDAR-derived digital elevation data. Furthermore, they demonstrated that their model could be used to estimate coseismic subsidence, or the amount by which the ground surface drops during a large magnitude megathrust earthquake, along the Cascadia Subduction Zone. Their research shows that analyses of landscapes with extensive debris flow valley networks can help quantify crustal deformation in tectonically active regions.

Brian's co-authors were Joshua Roering, also with the University of Oregon, and Ashley Streig with Portland State University.


In unglaciated steeplands, valley reaches dominated by debris flow scour and incision set landscape form as they often account for > 80% of valley network length and relief. While hillslope and fluvial process models have frequently been combined with digital topography to develop morphologic proxies for erosion rate and drainage divide migration, debris-flow-dominated networks, despite their ubiquity, have not been exploited for this purpose. Here, we applied an empirical function that describes how slope-area data systematically deviate from so-called fluvial power-law behavior at small drainage areas. Using airborne LiDAR data for 83 small (~ 1 km2) catchments in the western Oregon Coast Range, we quantified variation in model parameters and observed that the curvature of the power-law scaling deviation varies with catchment-averaged erosion rate estimated from cosmogenic nuclides in stream sediments. Given consistent climate and lithology across our study area and assuming steady erosion, we used this calibrated denudation-morphology relationship to map spatial patterns of long-term uplift for our study catchments. By combining our predicted pattern of long-term uplift rate with paleoseismic and geodetic (tide gauge, GPS, and leveling) data, we estimated the spatial distribution of coseismic subsidence experienced during megathrust earthquakes along the Cascadia Subduction Zone. Our estimates of coseismic subsidence near the coast (0.4 to 0.7 m for earthquake recurrence intervals of 300 to 500 years) agree with field measurements from numerous stratigraphic studies. Our results also demonstrate that coseismic subsidence decreases inland to negligible values > 25 km from the coast, reflecting the diminishing influence of the earthquake deformation cycle on vertical changes of the interior coastal ranges. More generally, our results demonstrate that debris flow valley networks serve as highly localized, yet broadly distributed indicators of erosion (and rock uplift), making them invaluable for mapping crustal deformation and landscape adjustment.

More Information

For more information regarding the article, visit: Geomorphology
For more information on morphologic proxy for debris flow erosion with application to the earthquake deformation cycle, contact Brian Penserini at This email address is being protected from spambots. You need JavaScript enabled to view it..

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