About

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I am a postdoc at the University of Arizona working with Susan Beck on continent-wide scale imaging in South America.

Contact info: rwporritt at gmail.com, rporritt at usc.edu, rob at seismo.berkeley.edu, porritt at email.arizona.edu

Newer Paper! Robert W. Porritt, Meghan S. Miller, Leland J. O’Driscoll, Cooper W. Harris, Nova Roosmawati, Luis Teofilo da Costa, Continent–arc collision in the Banda Arc imaged by ambient noise tomography, Earth and Planetary Science Letters, Volume 449, 1 September 2016, Pages 246-258, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2016.06.011.

New Paper! Porritt, R. W., and S. Yoshioka (2016), Slab pileup in the mantle transition zone and the 30 May 2015 Chichi-jima earthquake, Geophys. Res. Lett., 43, doi:10.1002/2016GL068168.

Until recently I was a postdoc at the University of Southern California working primarily with Meghan Miller. We used multiple seismic imaging methods, such as S to P receiver functions and ambient noise tomography (ANT) to image cratonic structure in the Hudson Bay and we used ANT to image the Banda Arc collision in southeastern Indonesia (see the experiment blog here)

During my postdoc at USC, I spent four months in Kobe, Japan, working with Shoichi Yoshioka to test the bounds of receiver function based imaging in Japan. Our primary focus was to investigate the relationships between discontinuity structure and large seismic sources.

Also while at USC I worked with Thorsten Becker to analyze seismic anisotropy of the upper mantle from SKS splitting in Colombia. We found a significant change in the fast orientation of splitting over ~100 km relating to the transition from the arc to the back arc where a seismic gap indicates either slab tearing of a single plate, or side-by-side subduction of two plates.

I did my PhD in seismology at UC Berkeley. I worked with Richard Allen to constrain the seismic wave-speed structure with regional imaging methods. I am most interested in innovative methods of visualizing large datasets to find otherwise hidden information which may be key to solving the tectonic puzzle.

Scenes from UC Berkeley - Memorial Glade

Scenes from UC Berkeley – Memorial Glade (Photo credit: John-Morgan)

I developed the DNA13 tomographic model family. This model utilizes body wave delay times, teleseismic surface waves, and ambient seismic noise to provide constraints from the surface through the mantle transition zone. Additionally, we rotate waveform the data into the P-SV-SH ray oriented coordinate frame to measure two independent S wave arrivals. This allows an improved joint inversion of Rayleigh waves with SV component delay times.

I am also working with researchers at Los Alamos National Lab on an innovative method of model validation. We start with the proposition that a valid seismic model will be able to replicate waveforms to a degree of precision consistent with the model data fit. By simplifying the waveform metrics, we can can determine the improvement of fit through the use of finite frequency kernels over simple ray theoretical inversion kernels.

My first published work used Ambient Seismic Noise to image the lithosphere in Cascadia. [PDF] This study stemmed from two Flexible Array deployments I helped install, maintain, and eventually decommission in Cascadia. The FACES (FlexArray along Cascadia Experiment for Segmentation) and FAME (Flexible Array Mendocino Experiment) combined for approximately 100 broadband seismic stations. Utilizing these arrays we also looked at shear-wave splitting, ambient noise source location, body-wave tomography, and joint inversion of ambient noise, teleseismic surface waves, and reciever functions.

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