Gulf coast regional Q and boundaries from USArray data


Earth Scope USArray provides an excellent opportunity to improve the scientific understanding of crustal attenuation in the continental United States. Using USArray data, the location and character of Q transitions between major tectonic regions are defined, particularly in the Gulf Coast region, using transects of USArray transportable array (TA) observations across these transitions to look for major changes in regional Q. The regional Q within the defined Gulf Coast region and, as a separate region, Florida is estimated using the approach of McNamara et al. (1996), Benz et al. (1997), and Erickson et al. (2004). The central and eastern United States (CEUS)/Gulf Coast transition in Texas, Oklahoma, Arkansas, Mississippi, Alabama, Georgia, and the Florida panhandle is detected, demonstrating the ability to find this transition from the limited earthquake observations available. The Q boundaries all appear to be fairly sharp features with transitions less than the 70 km spacing of the USArray. The location of the CEUS/Gulf Coast boundary is different from the proposed boundary location in the Electric Power Research Institute (EPRI, 1993) and Next Generation Attenuation-East Project (NGA-East; Dreiling et al., 2014) regionalization studies, which are based on few direct Q observations. The observed boundary location is roughly coincident with the Thomas (2010) Alabama–Oklahoma transform and the Ouachita thrust, except it extends more into central Oklahoma because of other rift structures. The regional Q f Q0 × fη estimate, in which Q0 is the Q at 1 Hz, within the Gulf Coast boundary is Q0 259 24=− 22 and η 0:715 0:013 over a broad frequency band of 0.1–16 Hz. Q for Florida, except the panhandle, seems to be constant with frequency near Q 1000, which is more closely related to midcontinental Q than Gulf Coast Q.

Publication Title

Bulletin of the Seismological Society of America