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Mendenhall Research Fellowship - Research Opportunity #17-17 Hazard and energy studies at U.S. continental margins using ocean bottom seismographs
Detailed seismic observations of almost all subduction-zone related processes, including major hazards such as great subduction earthquakes, tsunamis, and island volcanic eruptions, require the use of ocean bottom seismographs (OBS) for accurate imaging and detailed earthquake localization. Passive margins like the U.S. Atlantic, Alaskan North Slope, and the Gulf of Mexico, host major oil, gas, and hydrate reservoirs and are also prone to submarine slope failures and potentially landslide-generated tsunamis. Shear-wave measurements, which can only be recorded directly by on-bottom instruments, provide valuable constraints on mechanical properties of marine sediments in situ, enabling us to, for example, model forearc deformation and tsunami generation during large subduction earthquakes, assess the potential for submarine slope failures, and measure natural gas hydrate concentrations. The advent of passive seismological techniques such as beam forming, seafloor compliance, and ambient noise imaging provide new tools to analyze data and learn new information about the seafloor and the hazards it contains. Passive seismology in the marine environment is unique both in terms of deployment considerations and data analysis and requires the development of special skills. The USGS Woods Hole Science Center (WHSC), located within the campus of the Woods Hole Oceanographic Institution (WHOI), owns many of the short-period OBS in the academic fleet, and two intermediate-period seismographs, and has access to additional intermediate-period seismographs. It maintains a close working relationship with the WHOI OBS facility and has been occasionally using additional WHOI-owned seismographs.
This Mendenhall project provides an opportunity to conduct independent innovative research on three passive seismology data sets collected by the OBS and to participate in the collection of new data sets. A high-quality data set was recorded for a year by six broad-band OBS arrayed close to the Puerto Rico Trench north in 2015-16 to augment data collected by the Puerto Rico seismic network. The OBS recorded over 4000 earthquakes, many of them occurring in seismic swarms. The data appears to be among the quietest data ever recorded by OBS due to the large water depth (~5,500 m) and lack of currents. First-order scientific questions that can be answered with this data set are, for example: Is the slab torn? What is the origin of the frequent seismic swarms that unnerve the citizens of Puerto Rico? Can the Puerto Rico trench produce a M9 earthquake and tsunami? The second data set consists of a cluster of intermediate-period OBS presently being deployed on the continental slope off Georges Bank to record ambient noise and teleseismic events. The goals there are to characterize the sediment properties of the failing slope and the deeper structure of the margin and understand the coupling between major storms and seismic energy traveling through the Earth. The teleseismic events may help define the crustal structure and tectonic evolution of this never-before studied portion of the U.S. margin, which has implications to potential energy resources in the area. A third OBS deployment is planned for 2020 along Queen Charlotte Fault, Alaska, to study fault-zone properties via the propagation of fault-guided waves. The Queen Charlotte Fault, connecting Vancouver Island and southern Alaska is perhaps the fastest moving strike-slip earthquake on Earth, with six M >7 during the past 100 years and a super-shear rupture, and is therefore a useful laboratory to study rupture along these types of faults.
Proposed Duty Station: Woods Hole, MA
Areas of Ph.D.: Seismology, marine geophysics or related disciplines (candidates holding a Ph.D. in other disciplines but with knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications: Applicants must meet one of the following qualifications: 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.)
Physical/Environmental Demands: Work is usually performed in an office environment. However, the candidate is encouraged to participate in the occasional deployment or retrieval of ocean bottom seismometers aboard ships of opportunity and to participate in overnight planning and scientific meetings. Work at sea will be as part of a small team of technicians and scientists under the safety supervision of the ship’s master.
Occasional travel - Overnight travel of 1 to 5 nights per month may be required.
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This job originated on www.usajobs.gov. For the full announcement and to apply, visit www.usajobs.gov/GetJob/ViewDetails/515821500. Only resumes submitted according to the instructions on the job announcement listed at www.usajobs.gov will be considered.