I have several main interests. Which ones I pursue at a given time depends of factors such as funding and the availability of students, among other things. One
of my interests is related to exploration seismology. In the past some of my students processed reflection and vertical seismic profiling (VSP) data using the
commercial package SIERRA, but now we are fortunate to have been awarded a $2.6
million donation from Landmark Graphics. Under this donation we received the
Promax seismic processing package, the Earth Cube 3-D visualization package,
as well as several others, all of which are routinely used in oil exploration.
We are currently in the process of installing these packages, which we plan to
use with data from the New Madrid seismic zone. This work will be done in
collaboration with Dr. R. Van Arsdale.

I also have a long-standing interest in earthquake location and 3-D velocity inversion. My work on earthquake location focused on a theoretical reanalysis of
the problem of joint hypocentral determination (JHD) an resulted in a reassessment of location concepts and techniques. I applied the software developed in this research to a number of data sets from interesting tectonic places, such as the Loma Prieta area and the New Madrid seismic zone, and my results showed a number of features not found by more standard software. A summary of results is in the two book chapters listed under my recent publications. A particularly important result was that in some cases the JHD station corrections, which under certain circumstances carry information about lateral velocity variations, indicated the presence of velocity variations larger than expected, which in turn had a significant effect on earthquake locations. This question was further investigated using 3-D velocity inversion software, which is the tool required for accurate locations when the lateral velocity variations are significant. However, not every inversion package performs well in those cases, as can be seen from the discussion in my Comment on the Campi Flegrei velocities (see Pujol, J., Comment on "Laboratory measurements of ultrasonic wave velocities ...). The inversion software I am currently using was written by Harley Benz (Benz et al, JGR, v. 101, p. 8111-8128, 1996) and incorporates the finite-difference software of Podvin and Lecomte (Gephys. J. Int., v. 105, p. 271-284, 1991) for the computation of travel times, which performs very well in the presence of large lateral velocity variations. One of my students applied Benz's software to data from the Northridge mainshock-aftershock sequence and I recently added data from the San Fernando sequence. Our results show very clear pictures of the San Fernando basin and the relation between velocity anomalies and earthquake locations. This research will be continued with support from the U.S.G.S.

My work on vertical seismic profiling began as a Ph.D. student in Wyoming and continues to date. VSP data are excellent to study the propagation of waves within the earth. We can see, for example, how waves reflect and how P waves are converted to S waves, and how complicated wave propagation can actually be. The VSP data are also great to investigate anelastic attenuation because it is possible to observe the downgoing wave field, something that cannot be done with surface data.

My most recent VSP work uses data recorded at two different depth scales: kilometers and meters. In the first case I am working on the analysis of data from the 9 km deep borehole recorded in crystally rock in Germany. This ambitious undertaking, known by the German acronym KTB (http://icdp.gfz-potsdam.de/html/ktb/ktb.htm) produced a wealth of information that could have not been inferred form surface data. For example, open cracks and fluids were found much deeper than expected. Another unexpected result was high attenuation at depths close to 4 km (see Pujol, J., E. Lueschen, and Y. Hu, Seismic wave attenuation in Germany's ... paper), which may be caused by the presence of fluids. The most recent VSP data was recorded in 1999 to a depth of 8.5 km and preliminary analysis already show interesting wave propagation results. On the other end of the scale, I have analyzed VSP data recorded to 60 m depth or less in the Memphis area (see Pujol, J., S. Pezeshk, Y. Zhang, and C. Zhao. Unexpected values of Qs in ...). The goal of this study was to determine the attenuation of the shallow unconsolidated
sediments of the Mississippi embayment as part of a larger seismic hazards research project. This research was conducted in collaboration with Dr. Shahram Pezeshk, a colleague in the Dep. of Civil Engineering, and will be expanded in the next two years thanks to a grant from the U.S.G.S.

 

 
  • Associate Professor since 1998

  • Ph.D., Geophysics, University of Wyoming, 1985

  • Earthquake and exploration seismology, inverse problems, earthquake location, 3-D velocity inversion, attenuation, vertical seismic profiling

Books and Book Chapters:

Pujol, J. Elastic wave propagation and generation in seismology, Cambridge
University Press, June 2003.
http://books.cambridge.org/0521520460.htm

Pujol, J. Software for joint hypocentral determination. In International
Handbook of Earthquake and Engineering Seismology, Part B, Lee, W., H.
Kanamori, P. Jennings, and C. Kisslinger, Eds., 1621-1623. Academic Press, July 2003.

Pujol, J. Joint event location - The JHD technique and applications to data from local seismic networks. In "Advances in seismic event location", Thurber C., and N. Rabinowitz, Eds. Kluwer Academic Publishers, 163-204, 2000.

Refereed papers:

Pujol, J. Earthquake location tutorial: graphical approach and approximate
epicentral location techniques. Seism. Res. Lett., v. 75, 63-74, 2004.

Rydelek, P. and J. Pujol. Real-time seismic warning with a two-station
subarray. Bull. Seism. Soc. Am., v. 94, 1546-1550, 2004.

Pujol, J. The body force equivalent to an earthquake: a tutorial.
Seism. Res. Lett., v. 74, 163-168, 2003

Pujol, J. Determination of a local magnitude scale: a generalized inverse
solution, Bull. Seism. Soc. Am., v. 93, 2758-2761, 2003.

Pujol, J., S. Pezeshk, Y. Zhang, and C. Zhao. Unexpected values of Qs in the
unconsolidated sediments of the Mississippi embayment. Bull. Seism. Soc. Am., v. 92, 1117-1128, 2002.

Mueller, K., and J. Pujol. Three dimensional geometry of the Reelfoot blind thrust: implications for moment release and earthquake magnitude in the New Madrid seismic zone. Bull. Seism. Soc. Am., v. 91, 1563-1573, 2001.

Pujol, J., Comment on "Laboratory measurements of ultrasonic wave velocities in rocks from the Campi Flegrei volcanic system and their relation to other field data'', by M. Zamora, G. Sartoris, and W. Chelini. J. Geophys. Res., v. 105, 21,537-21,542, 2000.

Qi, G., J. Pujol, and Z. Fan. 3D AE visualization of bone cement fatigue crack locations. J. Biomedical Materials Res., v. 52, 256-260, 2000.

Qi, G., and J. Pujol. Numerical assessment of the quality of AE source locations in the presence of noise. J. Acoust. Emiss., v. 17, Nos. 3-4, 111-120, 1999.

Ratchkovsky, N., J. Pujol, and N. Biswas, Relocation of shallow earthquakes in southern Alaska using the joint hypocenter determination method. Seismological Journal v. 2, 87-102. 1998.

Pujol, J., E. Lueschen, and Y. Hu, Seismic wave attenuation in Germany's deep borehole area from VSP data. Geophysics v. 63, 354-365, 1998.

Pujol, J., R. Herrmann, S. C. Chiu, and J. M. Chiu, Constrained relocation of
New Madrid seismic zone earthquakes. Seism. Res. Lett., v. 69, 56-68, 1998.

University of Memphis