23-28. Advancing quantitative lacustrine paleoseismology using historical records of earthquake shaking in Alaska

Research Opportunity Description

Background. Lacustrine environments (lakes) in southcentral Alaska record sedimentary evidence of strong shaking caused by historic earthquakes, including the 2018, M7.1 Anchorage and the 1964, M9.2 Great Alaska earthquakes (Boes et al., 2018; Praet et al., 2017; 2022; Singleton et al., 2024, in press; Van Daele et al., 2019; Vanderkerkhove et al., 2019). A variety of shaking-related sedimentary features in lakes include turbidites formed from shaking induced subaqueous gravity flows, large submarine landslides, and soft sediment deformation (Molenaar et al., 2022; Praet et al., 2017; 2022; Singleton et al., 2024, in press; Van Daele et al., 2019a). The various features that record shaking in lakes reflect a spectrum of shaking parameters and different physical environments. Recent work shows that historic earthquakes in southcentral Alaska generate sedimentary evidence if a minimum shaking intensity is reached (Moernaut et al., 2014; Singleton et al., in press). However, beyond this minimum intensity it is unclear what combination of factors is necessary to produce the myriad types of observed sedimentary evidence (i.e., surficial sediment remobilization vs large submarine landslides) (Praet et al., 2022). 

Despite recent advances in lacustrine paleoseismology, key questions about how to derive quantitative estimates of past earthquake shaking drive current research, such as: What are the key factors in a lake’s physiography, sediment characteristics, and seismic shaking parameters (e.g., PGA, PGV, duration, frequency content) that influence the response to earthquake shaking in lakes? Do certain characteristics of shaking-related deposits reflect variations in earthquake sources (e.g., megathrust vs intraslab vs crustal) and seismic shaking? What minimum thresholds in shaking intensity and duration are required to remobilize subaqueous sediment and how do variations in these parameters affect the deposits that record earthquakes? This research opportunity seeks candidates interested in developing novel approaches that blend seismology and sedimentology to determine quantitative shaking estimates for past earthquakes using the characteristics of lake sediments that record earthquakes.

Lacustrine imprints of seismic shaking have been likened to natural seismographs (Singleton et al., 2024; Van Daele et al., 2019a). Yet reconstructing the fault source, shaking intensity, and earthquake magnitude corresponding to earthquake-triggered sedimentary evidence in lakes remains a cutting-edge research topic (Howarth et al., 2021; Moernaut et al., 2014; 2020; Van Daele et al., 2019b). The Pacific-North American plate boundary in southcentral Alaska features crustal, slab, and megathrust seismic sources that have generated large earthquakes in the 20^th and 21^st centuries. Because of the rich earthquake history in the region, lacustrine environments present a natural laboratory to study the imprints of seismic shaking and offer the rare opportunity to advance methods that use paleoseismic data to quantify earthquake shaking intensity and duration. One aspirational objective in USGS-led lacustrine paleoseismology research is to test and develop methods that quantify shaking intensity and duration, among other seismic parameters, from the observable earthquake-triggered evidence in lake sediments. Advancing such methods is a critical step to connect the secondary evidence found in lake environments with the primary seismic source. 

Research Opportunity. This research opportunity aims to develop methods to quantify the shaking intensity and duration of past earthquakes based on lacustrine imprints of strong shaking in south-central Alaskan lakes. A wealth of baseline data from eleven Alaskan lakes is available, including high-resolution sub-bottom seismic profiles, percussion-driven gravity cores, and detailed bathymetric maps, and additional lacustrine studies are planned. The Alaskan lacustrine paleoseismology database describes shaking related sedimentary evidence from different seismic sources (slab vs plate interface), and a range of magnitudes and shaking intensities. Additionally, the Alaskan database come from studies of lakes with different physiographies and sedimentologies (i.e., deep proglacial lakes to shallow kettle lakes), providing sufficient data to identify the combination of factors that produce the observed spectrum of shaking related deposits. Ongoing seismic monitoring of Skilak Lake will provide measurements of amplification and tuning of earthquake-generated ground motion that can be used to study the effects of basin site response on turbidite triggering. As a compliment to the ongoing seismic monitoring, a recent push has developed a suite of field and laboratory tools capable of characterizing the geomechanical properties of the lacustrine sediments.

The Mendenhall fellow will also benefit from collaboration with EHP and CMHRP focused studies of the Alaska Aleutian subduction zone planned for 2025–2030, including ongoing seismic monitoring of Skilak Lake and earthquake recurrence studies at Chelatna, Esther, and Allison Lakes.

An ideal applicant would have experience in marine and/or lacustrine sedimentology, paleoclimatology, and specifically, experience with sediment core collection and analyses using advanced laboratory techniques. In addition, they might also have experience with interpretation of sediment proxy data, dating techniques (e.g., radiocarbon, lead isotope, etc.), and (ideally) high-resolution seismic stratigraphy and paleoseismology.

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

References

Boes, E., Van Daele, M., Moernaut, J., Schmidt, S., Jensen, B.J., Praet, N., Kaufman, D., Haeussler, P., Loso, M.G. and De Batist, M., 2018. Varve formation during the past three centuries in three large proglacial lakes in south-central Alaska. GSA Bulletin, v.130, no. 5-6, p.757-774. https://doi.org/10.1130/B31792.1

Howarth, J. D., Barth, N. C., Fitzsimons, S. J., Richards-Dinger, K., Clark, K. J., Biasi, G. P., ... & Sutherland, R. (2021). Spatiotemporal clustering of great earthquakes on a transform fault controlled by geometry. Nature Geoscience, 14(5), 314-320.

Moernaut, J., Daele, M. V., Heirman, K., Fontijn, K., Strasser, M., Pino, M., ... & De Batist, M. (2014). Lacustrine turbidites as a tool for quantitative earthquake reconstruction: New evidence for a variable rupture mode in south central Chile. Journal of Geophysical Research: Solid Earth, 119(3), 1607-1633.

Moernaut, J., Van Daele, M., Strasser, M., Clare, M.A., Heirman, K., Viel, M., Cardenas, J., Kilian, R., de Guevara, B.L., Pino, M. and Urrutia, R., 2017. Lacustrine turbidites produced by surficial slope sediment remobilization: a mechanism for continuous and sensitive turbidite paleoseismic records. Marine Geology, 384, pp.159-176.

Moernaut, J. (2020). Time-dependent recurrence of strong earthquake shaking near plate boundaries—A lake sediment perspective, Earth Science Reviews 210, 103344, doi: 10.1016/j.earscirev.2020.103344.

Molenaar, A., Van Daele, M., Huang, J. J. S., Strasser, M., De Batist, M., Pino, M., ... & Moernaut, J. (2022). Disentangling factors controlling earthquake-triggered soft-sediment deformation in lakes. Sedimentary Geology, 438, 106200.

Praet, N., J. Moernaut, M. Van Daele, E. Boes, P. J. Haeussler, M. Strupler, S. Schmidt, M. G. Loso, and M. De Batist (2017). Paleoseismic potential of sublacustrine landslide records in a high-seismicity setting (south-central Alaska), Marine Geology 384, 103–119, doi: 10.1016/j.margeo.2016.05.004. 

Praet, N., M. Van Daele, T. Collart, J. Moernaut, E. Vandekerkhove, P. Kempf, P. J. Haeussler, and M. De Batist (2020). Turbidite stratigraphy in proglacial lakes: Deciphering trigger mechanisms using a statistical approach, Sedimentology 67, no. 5, 2332–2359, doi: 10.1111/sed.12703.

Praet, N., Van Daele, M., Moernaut, J., Mestdagh, T., Vandorpe, T., Jensen, B. J., ... & De Batist, M. (2022). Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south‐central Alaska. Sedimentology.

Singleton, D. (2024). Calibrating the subaqueous seismograph: Using recent events to inform our knowledge of the past, PAGES Mag 32, no. 1, 4–5, doi: 10.22498/pages.32.1.4.

Singleton, D. M., Brothers, D., Haeussler, P. J., Witter, R. C., & Hill, J. C. (in press). Constraining the earthquake recording threshold of intraslab earthquakes with turbidites in southcentral Alaska's lakes and fjords. In: Ruppert N et al. (Eds) Tectonics of Alaska and Western Canada. AGU Geophysical Monograph Series.

Van Daele, M., P. J. Haeussler, R. C. Witter, N. Praet, and M. D. Batist (2019a). The Sedimentary Record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the Lacustrine Seismograph, Seismological Research Letters 91, no. 1, 126–141, doi: 10.1785/0220190204. 

Van Daele, M., Araya-Cornejo, C., Pille, T., Vanneste, K., Moernaut, J., Schmidt, S., ... & Cisternas, M. (2019b). Distinguishing intraplate from megathrust earthquakes using lacustrine turbidites. Geology, 47(2), 127-130.

Vandekerkhove, E., M. V. Daele, N. Praet, V. Cnudde, P. J. Haeussler, and M. D. Batist (2019). Flood‐triggered versus earthquake‐triggered turbidites: A sedimentological study in clastic lake sediments (Eklutna Lake, Alaska), Sedimentology 186, 195–26, doi: 10.1111/sed.12646.

Proposed Duty Station(s)

Anchorage, Alaska

Santa Cruz, California

Woods Hole, Massachusetts

Areas of Ph.D.

Geology, geophysics, oceanography, seismology, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications

Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, or Research Oceanographer. 

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the USGS Human Resources specialist.)