top of page

How would the proposed Humboldt offshore wind infrastructure interact with geological hazards, such as earthquakes and tsunamis?

Future studies are planned to determine more precisely how the North Coast’s proposed offshore wind infrastructure would interact with geological hazards, such as earthquakes and tsunamis, and to contribute to our current knowledge that is based on past case studies and research from around the world.

​

The North Coast of California, which includes the locations of the Humboldt Wind Energy Area (1) and other proposed offshore wind infrastructure, is an extremely seismically active area characterized by frequent earthquakes and other related geological hazards (2) because of its proximity to the intersection of three tectonic plates (the Pacific, Gorda, and North American plates) that is known as the Mendocino Triple Junction.

map-hi-res.jpg

Overview map of features in the Mendocino Ridge area.

Source: NOAA (20)

While floating offshore wind turbines are generally better suited to seismically active locations (3) compared to fixed-bottom offshore wind turbines because of generally greater resilience against the effects of ground shaking, floating offshore infrastructure, let alone its onshore companions, are not at all immune to potential adverse impacts from earthquakes and other geological hazards.

 

For instance, the shock waves produced by the compression of sea water during submarine earthquakes, or seaquakes, can disseminate into the towers and nacelles of both fixed-bottom and floating wind turbines, causing large vertical accelerations that can exceed operational limits (4). There are also risks to mooring and anchorage systems (5), as well as to the buried cables that transmit power to shore (6), which “are at risk of damage when exposed, and [whose] performance drops when over buried” (7).

​

Major earthquakes and seaquakes throughout the Pacific Ocean can also be tsunamigenic, meaning that they may cause significant tsunamis; however, the relationship between earthquake rupture and subsequent tsunamis is complex (8).

 

Our current knowledge about the various potential geological hazards to the proposed North Coast offshore wind infrastructure is relatively limited at this early stage of offshore wind development off the eastern Pacific Coast, although local studies are ongoing. The analysis and mitigation of geological hazards to offshore wind infrastructure in the Pacific Ocean differs from that in the Atlantic Ocean or the North Sea, since earthquakes and tsunamis in the western Atlantic are relatively infrequent because the only major subduction zones are along the Caribbean Sea (9), and the rare tsunamis in the North Sea are generated by deep water slope failure (7), but usually diminished by the shallow water approaching the coast (10). And while local analyses of earthquake and tsunami risk to the proposed North Coast offshore wind infrastructure are still preliminary, we can nevertheless learn from past events in the eastern Pacific.

 

On March 11, 2011, a 9.0–9.1 magnitude undersea megathrust earthquake (the largest quake ever recorded in Japan) occurred about 45 miles east of the Oshika Peninsula of Japan’s Tōhoku region, and subsequently triggered a 16-foot tsunami (11). The earthquake’s epicenter was located only about 186 miles from the Kamisu 1 semi-offshore wind farm (12). Click here to view a photo of Kamisu 1 after the Tōhoku earthquake (13).

 

Kamisu 1 was shut down temporarily after the post-quake tsunami due to grid failure and engulfment of a nearby substation (14) immediately after the quake, but the wind farm resumed operation (15) only three days later after checks showed no damage to the system, and were soon back to supplying electricity to the Tokyo Electric Power Company. The fully operational wind facilities were asked to help compensate for the gap in power (14) caused by the Fukushima-Daiichi nuclear reactor failure and meltdown, which prompted Japanese authorities to idle all of the country’s 48 nuclear reactors, which formerly supplied 30% of Japan’s electricity (16).

Numerous factors were considered in engineering the turbines to successfully resist seismic disruption (17). The wind turbine’s nacelle, or electrical enclosure, “contains the main shaft, gearbox, generator, and associated components. The nacelle bedplate has a girder structure. The gearbox is attached to the bedplate and transmits the torque from the main shaft to the generator. A roller bearing is used for the yaw system together with electrical actuators and a hydraulic brake system. The step-up transformer and power conditioning system are not located in the nacelle…to reduce the weight of the nacelle, lower the center of gravity, reduce seismic overturning moment and make these components more easily accessible. The converter and transformer are located at ground level to increase seismic resistance and facilitate maintenance.” (17)

Screenshot 2024-09-25 at 4.19.53 PM.png

Layout of major wind turbine components.

Source: Matsunobu et al. 2014 (17, pg. 2)

Based on the analysis and lessons of Kamisu 1, in 2015 Japanese companies installed a 344-foot offshore wind turbine (16), billed as being able to withstand 65-foot waves (and even tsunamis) (18) due to the use of deliberately slackened chains to connect the turbine to the seabed, in the Onahama Port test area of Fukushima, Japan (19).

 

In 2020, two reports were published related to geological hazards for the proposed North Coast offshore wind infrastructure: “Potential Earthquake, Landslide, Tsunami and Geo-Hazards for the U.S. Offshore Pacific Wind Farms” by RPS for the U.S. Bureau of Ocean Energy Management (6), and “California North Coast Offshore Wind Studies: Overview of Geological Hazards” by the Schatz Energy Research Center at Humboldt State University (now Cal Poly Humboldt) (2). 

 

The RPS (6) and Schatz (2) studies agree that all components of the proposed North Coast offshore wind infrastructure, including a floating offshore wind farm, cable landfall on the coastline, interconnection with onshore electric transmission infrastructure, and port infrastructure located within Humboldt Bay, could be negatively impacted by the direct effects earthquakes or seaquakes, as well as indirect hazardous effects including tsunamis, destabilization of biogenic methane gas hydrates beneath the seafloor, onshore and offshore sediment liquefaction, slope instability, and submarine landslides. 

 

More information about potential geological hazards to proposed North Coast wind infrastructure will be added to this website as it is collected in the future.

References​​

  1. U.S. Bureau of Ocean Energy Management. (n.d.). Humboldt Wind Energy Area. U.S. Department of the Interior. www.boem.gov/renewable-energy/state-activities/humboldt-wind-energy-area 

  2. Hemphill-Haley, M.A., Hemphill-Haley, E. and Wunderlich, W. (2020). Overview of Geological Hazards. In M. Severy, Z. Alva, G. Chapman, M. Cheli, T. Garcia, C. Ortega, N. Salas, A. Younes, J. Zoellick, & A. Jacobson (Eds.) California North Coast Offshore Wind Studies. Humboldt, CA: Schatz Energy Research Center. https://schatzcenter.org/pubs/2020-OSW-R16.pdf 

  3. Bhattacharya, S., Biswai, S., Aleem, M., et al. (2021, June 12). Seismic Design of Offshore Wind Turbines: Good, Bad and Unknowns. Energies, 14(12): 3496. https://doi.org/10.3390/en14123496

  4. Kaynia, A.M., Blekastad, H., Schell, P., and Walter, E.L. (2022, November 8). Seismic response of floating wind turbines due to seaquakes. Wind Energy. https://doi.org/10.1002/we.2791 

  5. Kim, S., Jin, C., and Kim, M. (2024, January). Time-dependent responses and mooring tensions of a moored floating structure in tsunami waves. Marine Structures, 93. https://doi.org/10.1016/j.marstruc.2023.103538 

  6. RPS. (2020, May). Potential Earthquake, Landslide, Tsunami and Geo-Hazards for the U.S. Offshore Pacific Wind Farms. www.rpsgroup.com/imported-media/5565/potential-earthquake-landslide-tsunami-and-geohazards-for-the-us-offshore-pacific-wind-farms.pdf 

  7. University of Hull. (2024). Tsunami risk to UK offshore wind: Palaeo evidence and numerical model simulations. https://auracdt.hull.ac.uk/research-projects/tsunami-risk-to-uk-offshore-wind-palaeo-evidence-and-numerical-model-simulations/ 

  8. Pacific Coastal and Marine Science Center. (n.d.). Local Tsunamis in the Pacific Northwest. U.S. Geological Survey. www.usgs.gov/centers/pcmsc/local-tsunamis-pacific-northwest 

  9. U.S. Geological Survey. (n.d.). Could a large tsunami happen in the United States? www.usgs.gov/faqs/could-a-large-tsunami-happen-united-states 

  10. Netherlands Coastguard. (n.d.). Is it possible that a tsunami unfolds in the North Sea? https://kustwacht.be/en/faq/it-possible-tsunami-unfolds-north-sea 

  11. Wikipedia Contributors. (2024, July 10). 2011 Tōhoku earthquake and tsunami. Wikipedia. https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami 

  12. Sievert, T. (2011, March 20). Japan - Wind turbines survive both tsunami and earthquake. Windfair. https://w3.windfair.net/wind-energy/news/8957-japan-wind-turbines-survive-both-tsunami-and-earthquake 

  13. Goda, K. (2016, January). Photograph of the Kamisu (Hasaki) wind farm following the 2011 Tohoku earthquake [Image]. Research Gate. www.researchgate.net/figure/Photograph-of-the-Kamisu-Hasaki-wind-farm-following-the-2011-Tohoku-earthquake_fig2_282442990 

  14. Prideaux, E. (2011, March 11). The wind farm that withstood the Japanese tsunami. Wind Power Monthly. www.windpowermonthly.com/article/1061942/wind-farm-withstood-japanese-tsunami 

  15. Japan for Sustainability. (2011, July 10). Offshore Wind Farm Withstands Great East Japan Earthquake and Tsunami. www.japanfs.org/en/news/archives/news_id031055.html 

  16. Yamamoto, A. (2015, August 3). Japan Builds World's Largest Floating Wind Turbine off Fukushima. NBC News. www.nbcnews.com/news/world/japan-builds-worlds-largest-floating-wind-turbine-fukushima-n402871 

  17. Matsunobu, T., Inoue, S., Tsuji, Y., et al. (2014, December 31). Seismic Design of Offshore Wind Turbine Withstands Great East Japan Earthquake and Tsunami. Journal of Energy and Power Engineering, 8: 2039-2044. www.davidpublisher.com/Public/uploads/Contribute/550915d7442f1.pdf 

  18. Knapschaefer, J. (2015, August 11). Offshore from Fukushima, A Wind Turbine Rises. Engineering News-Record. www.enr.com/articles/5654-offshore-from-fukushima-a-wind-turbine-rises 

  19. Fukushima Offshore Wind Consortium. (2015, July 30). Fukushima Floating Offshore Wind Farm Demonstration Project. www.fukushima-forward.jp/project01/english/news_release/news150730.html 

  20. Henderson, J. and Bohan, M. (2014, September 23–October 12). Return to Mendocino Ridge: U.S. Extended Continental Shelf Project, Exploratory Mapping Expedition: Mission Overview. NOAA Ocean Exploration. https://oceanexplorer.noaa.gov/explorations/14mendocino/welcome.html

bottom of page