Large-N array observations of injection-induced seismicity in northern Oklahoma: the LASSO experiment

Sara L. Dougherty, Elizabeth S. Cochran, & Rebecca M. Harrington

Published August 14, 2017, SCEC Contribution #7654, 2017 SCEC Annual Meeting Poster #046

In response to the recent increase in seismicity rate in Oklahoma, we deployed a temporary array of more than 1,800 vertical-component nodal seismometers. The LArge-n Seismic Survey in Oklahoma (LASSO) array covered a 25-km-by-32-km region with a nominal station spacing of ~400 m in northern Oklahoma for one month in spring 2016. We identify local earthquakes recorded by the LASSO array using standard short-term average/long-term average (STA/LTA) and waveform-correlation-based detection techniques. The classic STA/LTA technique identifies more than 3,000 events during the deployment, a factor of ~50 increase over the regional earthquake catalog. The catalog produced from our dense array allows us to investigate sequences of likely-induced seismicity in a region of active wastewater injection, imaging seismicity with unprecedented clarity. We use data from LASSO to assess the locations, frequency, magnitudes, source properties, and spatiotemporal evolution of micro- to minor earthquakes. Preliminary hypocentral locations for the identified events indicate several dense clusters of seismicity that are active throughout the deployment. We construct a database of template waveforms from these events and use this in a correlation-based detection technique to identify additional smaller magnitude (M<2) earthquakes. We use these results to explore the spatiotemporal evolution of seismicity as recorded by the LASSO array. Of particular interest is migration of the seismicity along individual fault segments, especially in relation to energy production activities. The locations and orientations of active subsurface faults may provide insights into interactions between small-scale fault structures as well as the potential locations of future injection-induced seismicity.

Dougherty, S. L., Cochran, E. S., & Harrington, R. M. (2017, 08). Large-N array observations of injection-induced seismicity in northern Oklahoma: the LASSO experiment. Poster Presentation at 2017 SCEC Annual Meeting.

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