Dense array observations of induced seismicity: The LArge-n Seismic Survey in Oklahoma (LASSO) experiment

Sara Dougherty

Earthquake Science Center

Date & Time
Building 3, Rambo Auditorium
Rob Skoumal

The substantial increase in earthquake rate observed in Oklahoma during the last decade has largely been attributed to the disposal of wastewater from energy production activities. While existing sparse regional networks are able to capture the occurrence of most M≥3 earthquakes and some smaller magnitude events, micro to minor earthquakes typically cannot be detected. To enable the detection of microseismicity, we deployed a temporary array of >1,800 nodal seismometers in northern Oklahoma. The LArge-n Seismic Survey in Oklahoma (LASSO) array operated for approximately one month, covering a 25-km-by-32-km region with a nominal station spacing of ~400 m. We develop a local earthquake catalog from data recorded by the LASSO array, which allows us to investigate sequences of induced seismicity in this region of active wastewater injection with unprecedented clarity. A two-stage earthquake detection method identifies more than 13,000 earthquakes recorded by the array, a factor of ~140 increase over the regional earthquake catalog. We explore frequency-magnitude relationships and the spatiotemporal evolution of seismicity in our catalog. The locations and orientations of select active faults, as inferred from seismicity, will also be presented.

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