NMSU - Department of Physics - Colloquium Abstract



	Tom Hearn Department of Physics NMSU
Earthquake magnitudes, amplitudes, and the attenuation structure of the Earth.
Seismic amplitudes have been routinely measured for decades to estimate earthquake size, but have only recently been used to view the attenuation structure of the Earth. I will review how these data are collected and used for magnitude calculations and how they can be inverted to give attenuation structure. I focus on three data sets. Local amplitudes and surface-wave amplitudes used by the China National Network are two data sets that are sensitive to structure in the crust of China; world-wide surface-wave amplitudes collected by the International Seismological Centre are sensitive to both crust and mantle structure world wide. Tectonically active regions generally have the highest attenuation - presumably because they have more sediments, higher temperatures, and more fluids. However, volcanic activity that has intruded the crust with crystalline rocks creates low-attenuation regions. On a global scale, subduction zones cause the most attenuation while old cratonic cores cause the least.