My main research interests are in the field of observational seismology, which means that I use records of ground motion (sometimes also wave motion in the oceans) to learn about the Earth and earthquakes. Although scientific curiosity plays an important part in this research, I am also interested in practical applications of observational seismology to hazard reduction.

Earthquake Source Processes and Tsunamigenesis

    From seismograms we can derive information on the source characteristics of earthquakes: the type of faulting, the orientation of the fault plane, the size of the event, the distribution of slip on the fault plane, the speed with which the rupture propagated, etc. One of my current research projects (funded by NSF) is focussed on the characteristics of earthquakes that occur in subduction zones, both on the interface between subducting and overriding plates, as well as within the subducting plate itself, and the relationship between these different types of events.

    In collaboration with staff at the National Earthquake Information Center (NEIC) of the US Geological Survey, I maintain a system to determine fully automatic Centroid Moment Tensors near real-time for large global earthquakes. These CMT’s provide a reliable and fast magnitude estimate, in addition to information on the type of faulting responsible for the event. You can find more on this project, and subscribe to its E-mail list, on the researchcmt page at the USGS.

   With collaborators at JPL and Caltech, I also contribute to the development of a finite source response system for global earthquakes that will use seismic, geodetic and tsunami data (ARIA-EQ).

Hazard Reduction and Near Real-Time Seismology

    In addition to the researchcmt collaborative project with the NEIC, other National Earthquake Hazard Reduction grants also support my research into the rapid estimation of source parameters of earthquakes. A surface wave locator  I developed in a collaborative project with Hong Kie Thio at URS Corporation uses back-propagation techniques to quickly and reliable determine the long period magnitude and location of global events. Named the Surface wave Locator and Associator in Quasi Real-time (SLAQR, ask me for the password), it also makes very pretty movies...            

    Another project that was recently funded explores whether we can use the distribution of aftershocks after a large earthquake to determine the extent of the rupture plane of the mainshock.

      I am now also working on a USGS project that uses seismic waves that bounce off the surface of the Earth to improve the determination of depth of global earthquakes.

Selected Publications/Abstracts etc.

  Thio, H.K. and J. Polet: Probabilistic Tsunami Hazard Analysis, Proceedings of the 15th World Conference on Earthquake Engineering, Lisbon, Portugal, 2012.

Thio, H.K. and J. Polet: Tsunami early warning based on surface wave inversion techniques, Proceedings of the 15th World Conference on Earthquake Engineering, Lisbon, Portugal, 2012.

   Polet, J. and H. K. Thio, Rapid Calculation of the Centroid Moment Tensor and Waveheight Predictions Around the Pacific for the 2011 Tohoku Earthquake, Earth Planets Space, Vol. 63 (No. 7), pp. 541-545,  2011.

  Thio, H.K., Somerville, P.G. and J. Polet: Probabilistic Tsunami Hazard in California, Pacific Earthquake Engineering Research Center Report 2010/108, 331pp, 2010.

  Polet, J. and H. Kanamori: Tsunami Earthquakes, invited contribution to the “Encyclopedia of Complexity and Systems Science”, Editor-in-chief: Meyers, Robert A., Springer Publishing, ISBN: 978-0-387-75888-6, 2009.

  Polet, J., Thio, H.K. and P. Earle: Implementation of Near Real-Time Methods Using Surface Waves to Determine Earthquake Source Characteristics at the National Earthquake Information Center, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract S13B-1801, 2008.

  Polet J., Thio, H.K. and P. Earle: Near real-time determination of location, magnitude and source properties of large worldwide earthquakes using long-period surface waves. Seismological Research Letters; 78(2): 248-248, 2007.

  Polet, J.: A map of relative P wave delay times across southern California, Geochem. Geophys. Geosyst., 8, Q10003, doi:10.1029/2007GC001626, 2007.

  Ammon, C.J., C. Ji, H.K. Thio, D. Robinson, S. Ni, V. Hjorleifsdottir, H. Kanamori, T. Lay, S. Das, D. Helmberger, G. Ichinose, J. Polet and D. Wald; Rupture Process of the 2004 Sumatra-Andaman Earthquake, Science, 308, 1133-1139, 2005.

  Liu, Q., Polet, J., Komatitsch, D. and J. Tromp; Spectral-element moment-tensor inversion of earthquakes in southern California, Bull. Seismol. Soc. Am., 94, 1748-1761, 2004.

  Polet, J. and H.K. Thio: The 1994 Java tsunami earthquake and its “normal” aftershocks, Geophys. Res. Lett., 30, 1474, doi:10.1029/2002GL016806, 2003.

  Saikia, C. K., Thio, H. K., Ichinose, G., Rao, Bodin, P., Polet, J. and P. Sommerville; Bhuj, India earthquake of January 26, 2001: Reconnaissance report, Earthquake Spectra, Suppl. A to Vol. 18, 23-42, 2002.

  Hauksson, E., Small, P., Hafner, K., Busby, R., Clayton, R., Goltz, J., Heaton, T., Hutton, K., Kanamori, H. and J. Polet, Southern California Seismic Network: Caltech/USGS element of TriNet 1997-2001, Seismol. Res. Lett., vol. 72, 690-704, 2001.

  Polet, J. and H. Kanamori; Shallow subduction zone earthquakes and their tsunamigenic potential, Geophys. Journ. Int., 684-702,  2000.