Matt Pritchard

Cornell Earth & Atmospheric Sciences

Earthquakes/Tectonics Research

We are seeking to understand the processes that occur before, during and after earthquakes, particularly along subduction zones. 


Below are some of the results of our work:


1) In northern Chile, we document post-seismic deformation from 1995-2000 which include the first observations with sufficient resolution in both time and space to infer triggering of a large (Mw > 7) earthquake by a so-called ``silent earthquake'' (Pritchard & Simons, 2006) -- see image on right. 


2)  We have done detailed studies of 8 large subduction zone earthquakes (8.5 > Mw > 6.5) in northern Chile and southern Peru using both seismic and geodetic data (see second image).  These include:
        • 1993 Mw 6.8 northern Chile (Pritchard et al., 2006)
        • 1995 Mw 8.1 Antofagasta, Chile (Pritchard et al., 2002; 2006)
        • 1996 Mw 6.7 northern Chile (Pritchard et al., 2006)
        • 1996 Mw 7.7 Nazca, Peru (Pritchard et al., 2007)
        • 1998 Mw 7.1 Antofagasta, Chile (Pritchard et al., 2007)
        • 2001 Mw 8.5 Arequipa, Peru (Pritchard et al., 2007)
        • 2007 Mw 8.1 Pisco, Peru (Pritchard & Fielding, 2008)
        • 2007 Mw 7.7 Tocopilla, Chile (Loveless et al., 2010)


We have done seismic only studies of an additional 7 earthquakes in the same area spanning Mw 6.0 to Mw 7.6.  Loveless et al., 2010 summarizes all our observations to determine if the characteristics of these eaerthquakes could have been predicted.


3) In collaboration with structural geologists, we have shown that the rupture areas of large subduction zone earthquakes may be related to a system of surface cracks in northern Chile and southern Peru (Loveless et al., 2009) and exhibit a complex relation with upper-plate faults (Loveless et al., 2010).


4) We have studied the deformation in the upper plate of subduction zones in the Seattle, Washington region (Finnegan et al., 2008) and northern Chile (Loveless & Pritchard, 2008). 

 
Our current work is focused on separating inter-seismic deformation from atmospheric and orbital errors, quantifying the amount of plate convergence that is accomodated in large subduction zone earthquakes to the amount that contributes to mountain building, comparing seismic and InSAR estimates of crustal  earthquake parameters, and finite element modeling of post-seismic deformation.

Publications:

Holtkamp, S. G., M. E. Pritchard, and R. B. Lohman (2010) Earthquake swarms in South America, Geophys. J. Int., in revision.

Loveless, J. P., R. W. Allmendinger, M. E. Pritchard, and G. Gonzalez (2010) Normal and reverse faulting driven by the subduction zone earthquake cycle in the northern Chilean forearc, Tectonics, [in press]
Loveless, J. P., M. E. Pritchard, and N. Kukowski (2010) Testing mechanisms of subduction zone segmentation and seismogenesis with slip distributions from recent Andean earthquakes, Tectonophysics, [in press] 

Allmendinger, R. W., J. P. Loveless, M. E. Pritchard, and B. Meade (2009) From decades to epochs: Spanning the gap between geodesy and structural geology of active mountain belts, Journal of Structural Geology, 11, p. 1409-1422 [Link to Science Direct]

Loveless, J. P., R. W. Allmendinger, M. E. Pritchard, J. L. Garroway and G. Gonzalez (2009) Surface cracks record long-term seismic segmentation of the Andean margin, Geology, 37, 23-26. [Link to GSA Page]

Loveless, J. P., and M. E. Pritchard (2008) Motion on upper-plate faults during subduction zone earthquakes: Case of the Atacama Fault System, northern Chile, Geochem. Geophys. Geosyst., 9, Q12017, doi:10.1029/2008GC002155, [Link to AGU Page]
Finnegan, N. J., M. E. Pritchard, R. B. Lohman, and P. R. Lundgren (2008) Constraints on surface deformation in the Seattle, WA urban corridor from satellite radar interferometry time series analysis, Geophys. J. Int., 174, 29-41. [PDF Reprint] The definitive version is available at www.blackwell-synergy.com
Pritchard, M. E. and E. J. Fielding (2008) A study of the 2006 and 2007 earthquake sequence of Pisco, Peru, with InSAR and teleseismic data. Geophys. Res. Lett. 35, doi:10.1029/2008GL033374, [Link to AGU Page]. Supplemental information available as a PDF.

Pritchard, M. E., E. O. Norabuena, C. Ji, R. Boroschek, D. Comte, M. Simons, T. H. Dixon, and P. A. Rosen (2007) Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes,  J. Geophys. Res., 111, doi:10.1029/2006JB004294. [Link to AGU Page]

Pritchard, M. E. and M. Simons (2006) An aseismic fault slip pulse in northern Chile and along-strike variations in seismogenic behavior, J. Geophys. Res., 111, doi:10.1029/2006JB004258. [Link to AGU Page]

Pritchard, M. E., C. Ji, and M. Simons (2006) Distribution of slip from 11 Mw > 6 earthquakes in the northern Chile subduction zone, J. Geophys. Res., 111, doi:10.1029/2005JB004013. [Link to AGU Page]

Pritchard, M. E., M. Simons, P. A. Rosen, S. Hensley and F. H. Webb (2002) Coseismic slip from the July 30, 1995, Mw = 8.1 Antofagasta, Chile, earthquake as constrained by InSAR and GPS observations. Geophysical Journal International 150, 362-376. [Link to Blackwell Page]