One seismologist’s noise is another seismologist’s signal. What was once disregarded is now routinely processed as dense arrays of broadband seismometers continuously record small amplitude Earth motions, presenting an immense wealth of data. This dissertation presents three projects where ambient seismic noise, generated by ocean wave interactions with the solid Earth, recorded at hundreds of stations across East Asia, is processed to extract information about Rayleigh wave group velocity dispersion in order to infer details of the structure of the crust and upper mantle. In the first study, we collect data from broadband seismometer networks in Korea, Japan, and northeast China in order to develop a model of Rayleigh wave group velocity dispersion across the region. The results show the existence of a thin crust in the East Sea, and we observe low velocities across the entire period band in the Ulleung Basin associated with thick sediments at the surface and hotter than normal mantle temperatures. The second study expands upon the first by adding over 900 stations in China. The ambient noise is processed to develop a dispersion model for East Asia, and a cluster analysis is performed which reveals large scale tectonic provinces with common crust and upper mantle structures. Results from the cluster analysis are used to create a 3D model of shear wave velocities. We observe seismically fast and thick lithosphere in the Ordos block and Yangtze craton in the west, while a broad zone of low seismic velocities in the east indicates a vast region of lithospheric deformation. In the last study, we return to the Korean peninsula and incorporate new short period Rayleigh wave group velocity measurements into the 3D model of the second study to reveal the fine structure of the top 5 km of the crust. We implement a tomographic technique which directly solves for 3D model parameters, and the results show a strong correlation with known surface geology, with low velocities in Cretaceous basins and high velocities imaged in Precambrian massifs.

Last modified

• 01/25/2019

Creator

• Michael Witek

DOI

• https://doi.org/10.21985/N26R1B

Subject

• Earth and Planetary Sciences

Keyword

• Interferometry
• Seismology
• Tomography

Date created

• 2017-01-01

Resource type

• Dissertation

Rights statement

• In Copyright