Sunyoung Park Sunyoung Park
Postdoctoral Fellow

Harvard Seismology Group
Department of Earth and Planetary Sciences
Harvard University

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Research Interests

 I am interested in a variety of seismology topics including earth's shallow structure, deep structure, and earthquake characterization. I enjoy thinking about new or improved methodologies to study these topics.
 For my Ph.D. projects, I have looked into earthquake rupture and seismic structure of near surface, and mantle transition zone. I worked on an inversion scheme for rupture properties based on the 3-dimensional examination of earthquake directivity effect. The inversion is applied to estimate the rupture direction, length, propagation speed, and source duration of two deep earthquakes in the Kuril subduction zone, one of which shows complex rupture behavior. Recently, I developed a new technique utilizing the polarization information of incoming body waves to obtain the velocity map near the surface. Near-surface seismic structure is crucial to our understanding of seismic hazards, since it controls the level of ground shaking. Using the polarization observations, I have also detected instrument gain issues in Hi-net stations. It is an effective way to detect instrument gain problems without requiring an artificial signal that can interfere with seismic wave arrivals or physically examining the instrument, which is particularly advantageous for instruments such as borehole or ocean-bottom sensors that cannot be accessed easily. In addition, for the mantle transition zone, I am working on a new approach to study the upper mantle discontinuities from "triplication" data that are highly sensitive to discontinuity structures. This provides important constraints on the mantle composition and temperature in high spatial resolution compared to other types of seismic data containing relatively low frequency information.
 During my M.Sc., I studied mathematical analyses of seismic inverse problems, particularly the convergence of full waveform inversion technique. One must understand whether the set-up of an inverse problem will let the result converge to the true solution or not before jumping into massive computation and generating tomographic images. By examining the inverse problem from the theory, one can learn how to ensure the convergence to the true solution and increase the convergence rate.
 I have been very much enjoying looking at seismology from different angles. The theoretical perspective tells me how I can learn as much as possible from given data, while the real data perspective allows me to discover the real nature of earthquakes and earth structure. I appreciate the fact that what I enjoy working on can contribute to our knowledge of earthquakes and earthquake hazards, and potentially help people. At the same time, I take pleasure in improving our understanding of this planet, especially with integrated knowledge from other earth science disciplines.


2018 Ph.D. (Earth and Planetary Sciences - Geophysics), Harvard University
2012 M.S. (Energy System Engineering - Geophysics), Seoul National University, South Korea
2010 B.S. & B.A. (Energy Reources Engineering & Economics), Seoul National University, South Korea

Professional Experience

2018- Texaco Postdoctoral Scholar, California Institute of Technology (starting in October)
2018 Postdoctoral Fellow, Harvard University
2011-2012 Visiting Member, Geo-Mathematical Imaging Group (GMIG), Purdue University
2010 Visiting Researcher, Methodes et Techniques Sismique, TOTAL, Pau, France

Sunyoung Park


Park, S., Ishii, M., 2018, Frequency-Dependent Body-Wave Polarization for Constraining Local 1-D Near-Surface Structure: Application to USArray Data, In prep.

Park, S., Ishii, M., 2018, A Novel Approach Utilizing High-Frequency Triplication Data to Study Local Variations in the Upper-Mantle Transition Zone, In prep.

Park, S., Ishii, M., 2018, Double Discontinuities at the Base of the Mantle Transition Zone as Potential Barriers for Down-Wellings, In prep.

Park, S., Ishii, M., 2018, Patchy Melt Distribution Inferred from Missing 410-km Discontinuity, In prep.

Park, S., Ishii, M., 2018, Detection of Instrument Gain Problems Based on Body-Wave Polarization: Application to the Hi-net Array, Seismological Research Letters, In review.

Park, S., Ishii, M., 2018, Near-Surface Compressional and Shear Wave Speeds Constrained by Body-Wave Polarization Analysis, Geophysical Journal International, 213, 1559-1571, doi: 10.1093/gji/ggy072.

Park, S., Ishii, M., 2015, Inversion for Rupture Properties Based Upon Three-Dimensional Directivity Effect and Application to Deep Earthquakes in the Sea of Okhotsk Region, Geophysical Journal International, 203, 1011-1025, doi: 10.1093/gji/ggv352.

Park, S., Qiu, L., De Hoop, M. V., Shin, C., 2012, On Time-Harmonic Seismic Data and Blending in Full Waveform Inversion, Proceedings of the Project Review, Geo-Mathematical Imaging Group, 1, 305-318.

Park, S., 2012, Convergence of Full Waveform Inversion in the Complex-Frequency Domain, M.S. Thesis, Seoul National University.

Park, S., De Hoop, M. V., Calandra, H., Shin, C., 2011, Full Waveform Inversion: A Diffuse Optical Tomography Point of View, SEG Expanded Abstracts, 30, 2471-2475.

Park, S., Ha, W., Shin, C., Pyun, S., Calandra, H., 2010, A Strategy for Selecting the Laplace Damping Constants in the Laplace-Domain Inversion, Based on the Relationship Between the Laplace Damping Constant and the Detectable Depth of a High-Velocity Structure, SEG Expanded Abstracts, 29, 993-997.

Department of Earth and Planetary Sciences / Harvard University / 20 Oxford Street / Cambridge / MA 02138 / U.S.A. / Telephone: +1 617 495 2350 / Fax: +1 617 496 1907 / Email: