Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

Faculty Candidate Seminar - Sunyoung Park


 
03/02/2020 - 3:15pm
Location: 
Eckart 227
Event Description: 

SCRIPPS INSTITUTION OF OCEANOGRAPHY FACULTY CANDIDATE SEMINAR - 
Seismology 

DATE:          March 2nd, Monday, 3:15 p.m.  

LOCATION:       Eckart 227

SPEAKER:        Sunyoung Park

                         California Institute of Technology
            
 
TITLE:  Unraveling Detailed Structure of Mantle Discontinuities by Untangling Triplication Data
 
 
ABSTRACT:
 
Imaging of the seismic discontinuities that bound the mantle transition zone (at 410- and 660-km depths) is critical for understanding mantle dynamics and composition.  A type of seismic data that is highly sensitive to the detailed structure of these discontinuities is “triplication” data, i.e., three seismic phases that sample above, at, and below the discontinuity.  However, utilizing the triplication data remains challenging, as it is difficult to separate the three individual phases that arrive close in time.  In this talk, I introduce a novel technique that untangles the three arrivals and brings out the high-frequency information that is not easily accessible in the original form of the data, based on the theory that the three phases arrive at distinct horizontal speeds.  Taking advantage of a dense array of seismic stations in Japan, I apply this method to the 410- and 660-km discontinuities around the Kuril subduction zone, a region northeast of Japan.  My analyses reveal a diffuse and, at some locations, a "missing" 410-km discontinuity that cannot be explained solely by the presence of water, which suggests the significance of other effects such as high iron content in olivine.  Moreover, a “double” 660-km discontinuity separated by only 10 to 20 km is observed.  The additional discontinuity is compatible with a garnet phase transformation that can obstruct mantle flow in cold environments, with the implication that variable garnet concentrations can explain different subducting behaviors of slabs.  Going beyond the seismic structure, I also present a promising approach for understanding the rheological structure of the mantle based on geodetic observations of deep earthquakes.
 
 
 
Faculty Host:  Cathy Constable (cconstable@ucsd.edu)
For more information on this event, contact: 
lcosti@ucsd.edu
Event Calendar: 
Seminars
sharknado