De-Confounding of Relations Between Land-level and Sea-level Change in Northern California Cal-Trans...
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![Page 1: De-Confounding of Relations Between Land-level and Sea-level Change in Northern California Cal-Trans Briefing 2014 Tom Leroy, Jason Patton, & Todd Williams.](https://reader035.fdocuments.net/reader035/viewer/2022062719/56649ef35503460f94c05d98/html5/thumbnails/1.jpg)
De-Confounding of Relations Between Land-level and Sea-level Change in Northern
California
Cal-Trans Briefing 2014
Tom Leroy, Jason Patton, & Todd Williams
Cascadia GeoSciences, Northern Hydrology, HSU Geology, U of O Geology, & HBI members
Jeff Anderson, Ray Weldon, Reed Burgette
Mark Hemphill-Haley Whelan Gilkerson
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• Humboldt Bay Vertical Reference Group– US. Fish and Wildlife Service– Northern Hydrology– Pacific Watershed Associates– Humboldt State University– University of Oregon
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Variables that determine locally observed sea level
• Eustatic (global water volume changes)
• Tectonic (land-level changes)• Sediment Accretion (local sediment
deposition)
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Variables that determine locally observed sea level
• Eustatic (global water volume changes)
• Tectonic (land-level changes)• Sediment Accretion (local sediment
deposition)
![Page 5: De-Confounding of Relations Between Land-level and Sea-level Change in Northern California Cal-Trans Briefing 2014 Tom Leroy, Jason Patton, & Todd Williams.](https://reader035.fdocuments.net/reader035/viewer/2022062719/56649ef35503460f94c05d98/html5/thumbnails/5.jpg)
Tectonic forces in Northern California are primarily driven by the Cascadia subduction zone
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Bathymetry,topography, and primary faults of the Cascadia subduction zone
52Ê52Ê50Ê50Ê48Ê48Ê46Ê46Ê44Ê44Ê42Ê42Ê40Ê40Ê240Ê238Ê236Ê236Ê234Ê234Ê232Ê232Ê
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Cross-section of a subduction zone
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Atwater & Satake, 2009
Interseismic (between earthquakes)
Coseismic (during earthquake)
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Why is this important?(1)This demonstrates the elastic nature of the crust.
(2) The sense of motion for interseismic and coseismic
land level changes are inverted.
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Coastal subsidence, Japan 2011
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Flück, et al., 1997
Wang, et al., 2003
other deformation estimates for Cascadia
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How can we determine the spatial distribution of vertical land level
change?
• Tide gage analysis• Historic level survey analysis
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Historic Tide Gage Locations Humboldt Bay
1977 - 2014
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HBV Tide Gage Deployment Locations
2013-2014Mad River SloughEureka (Chevron Dock)Hookton Slough
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Additional Records
1978-2014 NOAA
North Spit
2010US ACOE
Fields LandingSamoa
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Mad River Slough Relative to CCMad River Slough subsides relative to Crescent City at 4.2 mm/yr.
Hookton Slough Relative to CCHookton Slough subsides relative to Crescent City at 6.8 mm/yr.
North Spit Relative to CCNorth Spit subsides relative to Crescent City at 5.4 mm/yr.
Monthly Mean Sea Level (Station Datum, mm) plotted vs. Time
* assumes 2.28 mm/yr SLR
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1931: San Jose – Eureka1931: Eureka – Grants Pass1944: Arcata – North Spit1967: Longvale – Crescent City1988: Eureka – Redding1988: Westport – Arcata – North Spit1992: Garberville – Loleta2004: State Hwy – Countywide GPS
Source: NGS Integrated Database; compiled by Don Campbell, CalTrans Dist. 1, 2010.
~ 70 control points surveyed from 1931-1992~ 40 observed either 1944-1967 or 1967-1988~ 20 observed 1944-1988
Historic Leveling,Humboldt Bay
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Land level – Tide Gage Misfit
Site (mm/yr)CC 0.69 ± 0.38MRS 0.40 ± 0.20 NS 0.31 ± 0.36HS 0.10 ± 0.51
Land level Change (mm/yr)
-1.18
-2.38
-3.58
* assumes 2.28 mm/yr SLR
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Future Projects and Objectives:Campaign Tide Gage – densify network of tide gages in Humboldt Bay to better understand the spatial variation in vertical deformation.Continuous GPS collocated with tide gages – to continuously tie the tide gage water surface elevation data to the tide gage station datum; to provide independent measure of vertical land level changePermanent Tide Gage at Hookton Slough – to better model higher order controls on sea level (meteorological, storms, ENSO, etc.) Repeated Level Surveys Around Humboldt Bay – to better understand the spatial variation in vertical deformationGeodetic Modeling – build a predictive model for estimates of vertical motion between benchmarks and tide gagesSediment Coring – to characterize the prehistoric record of Paleodeformation
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