Seismic investigation of the southern Rio Grande Rift

Competing models exist to explain what caused the Earth’s crust to spread apart 29 million years ago to create a region known today as the Rio Grande Rift (RGR). The RGR extends from central Colorado through New Mexico to northern Mexico, near El Paso. The RGR has different geologic features that distinguish it from most other valleys (e.g., the RGR was not cut by a river nor does a river branch upstream). A growing body of evidence shows that geologic activity still occurs in the RGR, with a continuation of faulting, seismicity and widening at a small rate of about 0.3 mm/yr (Woodward , 1977). We map of the seismic velocity structure and crustal thickness using data from the Rio Grande Rift Seismic TRAnsect (RISTRA) experiment and the EarthScope Transportable Array (USArray) dataset. In addition to the data we collected from the RISTRA experiment and USArray dataset, we also acquired receiver functions from the EarthScope Automatic Receiver Survey (EARS) website (http://www.earthscope.org/data) and waveform data from the Incorporated Research Institutes for Seismology (IRIS) Data Management Center (DMC). We requested seismograms from the IRIS DMC database where we acquired teleseismic events from Jan 2000 to Dec 2009. This includes 7,259 seismic events with a minimum magnitude of 5.5 and 106,389 continuous waveforms. This data was preprocessed (merged, rotated) using a program called Standing Order of Data (SOD). The RISTRA experiment and the USArray were designed to image crust and mantle structures by computing receiver functions for all data in the Southern Rio Grande Rift (SRGR). We map the crustal thickness, seismic velocity, and mantle structure for the sole purpose to better determine the nature of tectonic activity that is presently taking place and further investigate the regional extension of the Southern Rio Grande Rift (SRGR). Here we present preliminary results of the crustal and velocity structure using the kriging interpolation scheme seem stable and we are now able to clearly observe certain patterns we can use to interpret the southern RGR deformation and extension