τeκτoniκa https://tektonika.online/index.php/home <p>Diamond open Acess Journal publishing peer-reviewed research in Structural Geology and Tectonics</p> en-US jtektonika@gmail.com (Tektonika Team) jtektonika@gmail.com (Tektonika Team - Admin) Tue, 24 Jan 2023 09:25:20 +0000 OJS 3.3.0.8 http://blogs.law.harvard.edu/tech/rss 60 20th to 21st Century Relative Sea and Land Level Changes in Northern California https://tektonika.online/index.php/home/article/view/6 <p>Sea-level changes are modulated in coastal northern California by land-level changes due to the earthquake cycle along the Cascadia subduction zone, the San Andreas plate boundary fault system, and crustal faults. Sea-level rise (SLR) subjects ecological and anthropogenic infrastructure to increased vulnerability to changes in habitat and increased risk for physical damage. The degree to which each of these forcing factors drives this modulation is poorly resolved. We use NOAA tide gage data and ‘campaign’ tide gage deployments, Global Navigation Satellite System (GNSS) data, and National Geodetic Survey (NGS) first-order levelling data to calculate vertical land motion (VLM) rates in coastal northern California. Sea-level observations, highway level surveys, and GNSS data all confirm that land is subsiding in Humboldt Bay, in contrast to Crescent City where the land is rising. Subtracting absolute sea-level rate (~1.99 mm/year) from Crescent City (CC) and North Spit (NS) gage relative sea-level rates reveals that CC is uplifting at ~2.83 mm/year and NS is subsiding at ~3.21mm/year. GNSS vertical deformation reveals similar rates of ~2.60 mm/year of uplift at Crescent City. In coastal northern California, there is an E-W trending variation in vertical land motion that is primarily due to Cascadia megathrust fault seismogenic coupling. This interseismic subsidence also dominates the N-S variation in vertical land motion in most of the study region. There exists a second-order heterogeneous N-S trend in vertical land motion that we associate to crustal fault-related strain. There may be non-tectonic contributions to the observed VLM rates.</p> Jason R. Patton, Todd B. Williams, Jeffrey K. Anderson, Mark Hemphill-Haley, Reed J. Burgette, Ray Weldon II, Robert C. McPherson, Thomas H. Leroy Copyright (c) 2023 Jason R. Patton, Todd B. Williams, Jeffrey K. Anderson, Mark Hemphill-Haley, Reed J. Burgette, Ray Weldon II, Robert C. McPherson, Thomas H. Leroy https://tektonika.online/index.php/home/article/view/6 Tue, 24 Jan 2023 00:00:00 +0000