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Lg Attenuation in the Central and Eastern United States

Andrea Gallegos1, Nishath R. Ranasinghe1, James Ni1, and Eric Sandvol2
1New Mexico State University
2University Of Missouri, Columbia

Lg waveforms recorded by EarthScope's Transportable Array and US Flexible Array were used to determine interstation crustal attenuation in the central and eastern United States using two station and reverse two station/event methods. 1 Hz Q0 values were calculated based on Lg spectral amplitudes filtered at a narrow band from 0.5 to 1.5 Hz. The results show northeast trending high Q0 regions (low attenuation) ranging from eastern New Mexico to Wisconsin. Regions of low Q0 (high attenuation) are seen along the Minnesota-Wisconsin border, along the South Dakota-Nebraska border, in the Mississippi Embayment, Reelfoot rift, and in the Oklahoma Aulacogen. A positive correlation between heat flow, sediment thickness, recent tectonic activity, hydrocarbons, and low Q0 was observed. Areas with low heat flow, thin sediment cover, slight or no recent tectonic activity, and a lack of hydrocarbons were observed to have consistently high Q0. These new models use a larger amount of data and attain more ray path coverage than previous studies and better constrain Lg attenuation parameters in the study area. The attenuation maps generated are highly detailed and show positive correspondences with observed geology. This increase in detail can improve ground motion predictions of future large earthquakes for more accurate hazard assessment and improve overall understanding of the structure and assemblage of the Central and Eastern United States.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013