Geophysical and paleoseismological investigations of the marianna earthquake source in east-central arkansasperiod of performance: 8/1/2022 through 6/30/2023THIS purpose of the proposed project is…

Geophysical and paleoseismological investigations of the marianna earthquake source in east-central arkansasperiod of performance: 8/1/2022 through 6/30/2023THIS purpose of the proposed project is to further elucidate the earthquake history of the source of large earthquakes near marianna, arkansas, and thereby improve our understanding of the recurrence times of large-magnitude earthquakes and the long-term behavior of the marianna source. The northwest-oriented daytona beach lineament, marked by large sand blows, appears to be the surface expression of a fault zone imaged below in seismic reflection profiles. The sand blows formed as the result of large earthquakes circa 4.8, 5.5, and 9.9 KA, and at least two earlier events between 11 KA and 41 KA, and likely record slip events on the underlying fault zone. Results of our recent investigations at two liquefaction sites along the lineament add confidence in these interpretations and also point to the need for more dating of late pleistocene sand blows in order to better understand the paleoearthquake history and behavior of the fault zone. A better understanding of the earthquake history of the marianna area also will provide insights regarding spatial and temporal migration of seismicity across the region, including the new madrid seismic zone, which will have significant implications for earthquake hazard assessment in the central united states. Activities to be performed include geophysical and paleoseismological investigations of three liquefaction sites, as well as collection and dating of samples at two previously studied sites, to further assess the earthquake potential of the fault zone beneath the daytona beach lineament southwest of marianna, arkansas. Project deliverables include the following: - three-dimensional GPR profiles of large sand blows and related dikes used to position paleoseimic trenches at 3-5 sites; - trench logs and descriptions of liquefaction features, faults, and host deposits; - photographs of significant features including liquefaction features and faults exposed in trenches; - tables of the results of radiocarbon and OSL dating of samples collected in the trenches; - updated paleoliquefaction database and updated regional and local maps showing locations, sizes, and age estimates of sand blows and related sand dikes for the marianna area; - a map illustrating the paleoearthquake history of the marianna source and other seismic sources in the region, including the new madrid seismic zone; - a final technical report submitted to the earthquake hazards program and a scientific article submitted to the bulletin of the seismological society of america or the eastern section of seismological research letters for publication. This project is likely to produce new information about the timing, magnitude, and recurrence of paleoearthquakes in the marianna area that will contribute to the national probabilistic seismic hazard map, the national seismic hazard model, and regional assessments of earthquake hazards including the metropolitan areas of memphis, tennessee, and little rock, arkansas.