Dr. Robert Porritt Guest Lecture

DateJanuary 24, 2020
Time3:00 - 4:00 pm
LocationBaylor Sciences Building, Room C.206
DescriptionDr. Robert Porritt

Postdoctoral Fellow

Institute for Geophysics - Jackson School of Geosciences

The University of Texas at Austin

Shear velocity structure of the continuous US from complementary imaging methods with USArray and TexNet

The USArray seismic experiment has provided a revolutionary dataset for understanding the dynamic Earth system. The evenly spaced, broadband data coverage from coast to coast provides the necessary information for teleseismic imaging of the lithospheric and deeper mantle as well as detections of unexpected induced seismicity in the mid-continent. While several complementary seismic tomography models have been produced from the dataset, many are either regional in scope or too coarse for detailed interpretation. Here we overcome these limitations by travel-time tomography on a data-adaptive mesh, recovering structure of a similar length scale as published regional models in the continuous US while also recovering global structure consistent with previous global models outside the US. With our parameterization in terms of both Vsh and Vsv constrained by Love and Rayleigh waves respectively, we are able to estimate the radial anisotropy structure, indicative of the deformation history of the upper mantle. Large scale structures such as the contrast between the craton and cordillera and the subducting Farallon system are well resolved, as are smaller scale features such as the southeastern to eastern continental margin. This contrast is particularly distinctive across the Ouachita-Marathon Front in southeastern Texas. This region is one of the broadest passive continental margins on Earth today and has seen a significant increase in seismicity over the past decade. This has led to a recent TexNet temporary deployment to better understand the seismicity and seismic velocity structure of the region. Here we present results from ambient noise tomography jointly inverted with P to S receiver functions to image the crust of the region. The resulting 3D shear velocity model suggests most of the seismicity is correlated with the San Marcos Arch, a high stand that was stretched during the breakup of Pangaea, while the surrounding regions were magmatically underplated from the rifting process. This correlation between regions of induced seismicity and mid to lower crustal structure indicates the tectonic history of a region is important for the consideration of whether or not human activity will induce earthquakes.
PublisherDepartment of Geosciences
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