As part of a larger, cross-disciplinary USGS-wide focus on subduction zone science and associated hazards, the Coastal and Marine Hazards and Resources Program (CMHRP) has begun a multi-year project to examine the processes associated with earthquake, tsunami and landslide hazards along U.S. subduction zones. CMHRP’s Subduction Zone Marine Geohazards Project is centered around three science themes: (1) large earthquake recurrence (e.g., frequency of large earthquakes; likelihood of future events; similarities/differences between different types of events); (2) tsunamigenic potential and forearc response to large earthquakes; and (3) mechanics of megathrust rupture (e.g., factors that control the extent and slip amplitude of earthquakes along the subduction interface).
We encourage innovative research proposals designed to address one or more of the following research areas focused on the Cascadia Subduction Zone. Integration and synthesis of datasets, along with novel approaches to addressing the complex interrelationships among these research areas are also highly encouraged.
Relationship of Quaternary sediment distribution and stratigraphy to seafloor processes and earthquake history
Identification of the sources, volumes, and pathways of sediment delivered to the continental shelf and slope during the Quaternary is necessary to understand both the role of sediment in evolution of the margin and in recording past tsunami, earthquake and landslide events. Investigation of source-to-sink sediment dynamics is critical, particularly for identifying basins prone to strong shaking, slopes susceptible to landslides and optimal environment(s) for marine paleoseismology investigations. Examination of the linkages between fluvial systems, tectonic basins, fault interactions, seafloor morphology, offshore storage locations and dispersal pathways is fundamental in understanding earthquake and landslide recurrence and its variability along the margin.
Links between tectonic geomorphology, upper plate structure, and deeper subduction processes
Along-strike variations in morphology and structure along the Cascadia margin appear to reflect spatial variations in megathrust behavior, yet key questions remain regarding the relationship between the structure and behavior of the megathrust and forearc including controls on segmentation, locking, slip to the trench and the rupture patterns of upper and lower plate faults. Upper plate structures, including possible splay faults, that rupture with the megathrust are most likely to contribute to seafloor displacement and potential tsuamigenesis. Identification and regional mapping of active fault structures can provide insight to the segmentation pattern, earthquake recurrence intervals, stress/strain accommodation and variations in coastal uplift/subsidence. Links with onshore investigations can be used to assess the role that cross-shoreline faults play in margin segmentation, as well as in dictating the pattern and magnitude of coastal uplift or subsidence.
Influence of fluids and 3D structural interactions on the mechanics of subduction zone forearcs
The presence of fluids along the subducting plate boundary interface plays a fundamental role in influencing fault slip behavior, fault zone stability, frictional slip, and seismicity patterns at depth. Thus, it is important to understand the complex 3D structural relationships of forearc faults (e.g., megathrust fault, splay faults) and the hydrogeologic system that influences fault slip behavior and the generation of large, potentially tsunamigenic earthquakes. The shallow subduction of relatively young crust at the Cascadia margin also provides an ideal opportunity to study the effects of temperature on the behavior of the subducting system (e.g., impacts on lithospheric deformation, slab dehydration, fluid migration and fault friction). Elevated pore fluid pressure along faults reduces effective stress and fault strength along faults, and has also been proposed to result in alternative modes of slip behavior, such as episodic tremor and slip, low frequency earthquakes, and slow-slip events. With numerous seeps mapped along the margin, much of the shallow hydration system and its effect on subduction zone hazards can be understood by studying seabed fluid expulsion and fluid plumbing along forearc faults via imaging and sampling the uppermost forearc sediments.Ongoing and planned work to address these topics includes acquisition of regional-scale, high-resolution geophysical surveys (multibeam, multichannel sparker (MCS), CHIRP, magnetics) and targeted seafloor sampling, which will offer a wealth of new data for applicants to develop innovative, cross- disciplinary approaches to understanding geohazards along the Cascadia Subduction Zone. Due to the collaborative nature and broad scope of this project, interested applicants are strongly encouraged to contact the advisors listed below early in the application process to discuss project ideas and how their research might fit into the larger framework. The postdoctoral scholar will likely interact and collaborate with university partners and USGS scientists at other centers.
Proposed Duty Station: Santa Cruz, CA
Areas of Ph.D.: Marine geology, marine geophysics, 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 (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 Human Resources specialist.)
Research Advisor(s): Jenna Hill, (831) 460-7463, email@example.com; Janet Watt, (831) 460-7565, firstname.lastname@example.org; Danny Brothers, (831) 460-7460, email@example.com; Jared Kluesner, (831) 460-7547, firstname.lastname@example.org; Nathan Miller, (508) 457-2293, email@example.com; Jason Chaytor, (508) 457-2351, firstname.lastname@example.org
Human Resources Office Contact: Leah Lor, email@example.com, 916-278-9394
|Summary of Opportunities|