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Challenges in seismic interferometry with ambient noise

Presented by Dr. Jay Pulliam (Baylor) Thursday, November 4 4 p.m (CST) via Zoom Click here to join the meeting Abstract: Ambient noise seismic interferometry (SI) can provide important constraints on subsurface structure and can also serve as an inexpensive complement to active-source seismic exploration. In a typical SI approach, one seismic node serves as a “virtual source” and the others as receivers. The “virtual source gather” (an empirical Green’s function) that is obtained by cross-correlating and stacking signals recorded at each node represents the seismic response of the subsurface structure between the virtual source and each receiver. SI techniques can be used for a variety of applications, including reconstructing the Earth’s layering, seismic tomography, monitoring subsurface changes in, for example, volcanoes or reservoirs, and estimating surface wave group or phase velocities in the form of dispersion curves. However, a variety of real-world challenges must be overcome to ensure that SI results are accurate and that the process is efficient. These include, but are not limited to, dealing with uneven distributions of sources, extracting body waves (where desired) from signals that are overwhelmed by surface waves, assessing convergence to accurate Green’s functions, and identifying useful features in huge volumes of data. I will present an overview of strategies we have developed and tested for surmounting these obstacles, including applications that range from geothermal fields in Nevada to the Texas-Gulf of Mexico Coastal Plain to the entire southeastern United States Bonus: The Shillong Plateau, an anomalous, high-standing structure of uncertain origin located in northeast India is the site of great historical earthquakes, in 1897 and 1950, that were accompanied by unusually large vertical uplift. Its provenance and role in regional tectonics have been debated for more than a hundred years, but evidence has emerged recently that the crust beneath Bangladesh, to the south of the Shillong Plateau, may be oceanic in nature. If so, the Dhauki thrust fault, which bounds the southern edge of the Shillong Plateau may be the site of recently initiated subduction, in which case the underthrusting of oceanic lithosphere (Bangladesh/Bay of Bengal) beneath continental crust of the Northeast India Region would explain the vertical uplift and great earthquakes suffered by the Shillong Plateau. The region’s tectonics are obscured, of course, by the deepest pile of sediments on the planet, which may also play a role in subduction, if any. I will review the evidence and propose an investigation. We hope you will plan to attend