Recent Projects

South Eastern Suture of the Appalachian Margin Experiment

The broad goal of the SESAME proposal was to improve our understanding of lithospheric accretion processes and models of passive margin development. The Paleozoic Appalachian orogen in the southeastern United States - specifically the suture between Laurentia (proto-North America) and Gondwana (proto-Africa/South America) in southern Georgia provides an ideal location for imaging crust and mantle structures related to accretion.

SESAME comprised 85 broadband seismic stations deployed in three transects across Georgia and adjacent states. Click here for a link to the SESAME FDSN site to see more details about the station locations, published papers, and accessing the data we collected.

In addition to studying the suture, the SESAME array was deployed as the EarthScope Transportable Array swept across the southeastern United States. The combined resolution of these two data sets has provided unparalleled images of crust and upper mantle structures across our study area. Many of the structures observed were entirely unexpected.

PerU Lithosphere and Slab Experiment

The goal of the PULSE project was to investigate the causes and consequences of Peruvian flat slab subduction using broadband seismic data analyses. Flat slab subduction refers to the near-horizontal subduction of an oceanic plate at some depth below the overriding lithosphere. Various causes have been suggested for flat slab subduction including increased overriding plate velocity, increased mantle viscosity, young age of the subducting lithosphere (e.g. Van Hunen and N.J. Vlaar, 2001) and subduction of oceanic plateaux/ridges (e.g. Gutscher et al., 2001). A number of tectonic features have been attributed to flat slab subduction, including the migration of arc-volcanism away from the trench, thickening of overriding lithosphere, basement cored uplift and ignimbrite flare-ups. Today, approximately 10% of modern convergent margins can be characterized as having flat (or very shallowly dipping) subduction (e.g. Gutscher and Engdahl, 2000).

This project involved the deployment of 40 broadband seismometers along three transects that covered the area from Lima to Cusco. Click here for a link to the PULSE FDSN site to see more details about the station locations, published papers, and accessing the data we collected.

PULSE was temporally and spatially colocated with the CAUGHT deployment that comprised an additional 50 broadband stations just to the south of the PULSE stations (see below).

Central Andean Uplift and the Geodynamics of High Topography

CAUGHT was a multidisciplinary effort to test end-member geodynamic models for the surface uplift, deformation history, and lithospheric evolution of the central Andes of southern Bolivia and Peru. The central Andean plateau is one of the most imposing topographic features on Earth's surface and influences climate on regional and global scales. Despite its significance, the geodynamic processes responsible for plateau formation and evolution remain poorly understood. Approaches we used included: (1) imaging lithospheric structure from deployment of a broadband seismometer array and passive source seismology, (2) quantifying temporal variations in mantle input and crustal thickness into the Altiplano using igneous petrology and geochemistry (3) quantifying kinematic and shortening history from balanced cross-sections, sedimentary basin analysis, and detrital and bedrock thermochronology, (4) improving reconstructions of the plateau elevation and climate history from stable isotope geochemistry, and (5) climate modeling for evaluation of alternative explanations of paleoclimate and paleoaltimetry observations.

My part of this research project was of course the broadband seismic deployment and analyses. Together with Susan Beck and George Zandt of the University of Arizona, I installed 50 broadband seismic stations across the northern Altiplano adjacent to the PULSE project described above. Click here for a link to the CAUGHT FDSN site to see details about the station locations, published papers, and accessing the data we collected.