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22-31. Constraining earthquake cycle processes, ground motion characteristics, and rupture extent from geologic shaking proxies and coastal sedimentary records in subduction zones

This opportunity seeks to constrain past and future earthquake rupture characteristics along the Cascadia Subduction Zone. Proposals are encouraged that enhance and/or leverage the existing geologic record to constrain the magnitude, extent, and spatiotemporal clustering of earthquakes, as well as quantitative estimates of coseismic and interseismic deformation across multiple earthquake cycles. 

Description of the Research Opportunity

Onshore and offshore paleoseismic observations of great M8 – 9 earthquakes along portions of the Cascadia Subduction Zone (CSZ) provide evidence for megathrust earthquakes over the past ~10,000 years. Holocene coastal geologic evidence of elastic strain accumulation and release over the earthquake cycle includes stratigraphic contacts formed by coseismic subsidence during past great earthquakes; often the sharp, laterally continuous subsidence contacts are overlain by deposits of sand transported by high energy tsunamis. Furthermore, while modern geodetic datasets indicate variable along-strike interseismic coupling along the CSZ interface, little is known about the spatiotemporal variability of coupling across multiple earthquake cycles and its relationship with coseismic slip, afterslip, coastal subsidence, and long-term evolution of forearc topography. How and where CSZ earthquakes release energy – as full-margin ruptures, clusters of smaller events, or some combination thereof – will significantly impact hazard estimates, particularly for the long-period seismic energy that can significantly impact large-scale critical infrastructure. Better constraints on the variability of Cascadia earthquake rupture behavior and ground motions, including the potential clustering of earthquakes, multiple slip distributions, and spatial biasing of events to the south, are critical to reducing uncertainty in seismic and coseismic hazards throughout the region. This opportunity seeks proposals to examine evidence for coseismic and interseismic deformation processes to explore strain accumulation and release and earthquake rupture variability along the Cascadia subduction zone.  

This opportunity seeks proposals within two broad themes aiming to address these uncertainties in subduction zones. 

  1. Proposals that aim to enhance and or use the geologic record to constrain the magnitude, extent, and possible occurrence of earthquake sequences versus full-margin earthquake ruptures in Cascadia. Proposals that utilize one or more of a wide range of possible geologic proxies (e.g., subaerial and subaqueous landslides, liquefaction, fragile geologic features, tsunami deposits, and turbidites) to characterize rupture characteristics, and multi-cycle behavior, of Cascadia Subduction Zone earthquakes are welcome. Of particular interest are methods and geotechnical models that can produce new constraints on paleo-ground motion characteristics beyond just proxies for peak ground acceleration or high-frequency response (i.e., proxies sensitive to low frequency <1 Hz ground motions are desirable). This may also include furthering the understanding of the frequency-dependent triggering of subaerial and subaqueous landslides to infer shaking characteristics of past CSZ earthquakes.  

  1. Proposals that aim to quantitatively estimate coseismic and interseismic deformation along the CSZ during multiple earthquake cycles to better constrain past and future earthquake hazards along the active margin. The project may include, for example, analysis of coastal stratigraphic records, state-of-the-art paleogeodetic methods, geomorphic analysis of coastal and estuarine environments, geochronologic analyses, and/or instrumental geodesy. Given the large geographic extent of the subduction zone, postdoctoral applicants should leverage the spatially broad and diverse existing paleoseismic datasets along the CSZ to address outstanding questions in subduction zone hazards and to maximize the efficiency and impact of new datasets created over a typical postdoctoral timeline. 

Proposals beyond these suggested topics are welcome, and we encourage applicants to consider the broader USGS Subduction Zone Science priorities described in the USGS Subduction Zone Science Plan when formulating their proposal.  

Interested applicants are strongly encouraged to contact the Research Advisors early in the application process to discuss project ideas. 


Proposed Duty Station(s)

Seattle, Washington

Santa Cruz, California 


Areas of PhD

Geology, geomorphology, geophysics, civil and geotechnical engineering, 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). 



Applicants must meet one of the following qualifications:  Research Geologist, Research Geophysicist, Research Civil Engineer 

(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.)