Simulated ground motions for induced seismicity at a 12-story structure in Oklahoma using the SCEC Broadband Platform

Jessie K. Saunders, Frankie Martinez, Jennifer S. Haase, & Mohamed Soliman

Published August 15, 2018, SCEC Contribution #8756, 2018 SCEC Annual Meeting Poster #014

Oklahoma has been experiencing an increase in seismicity due to wastewater injection related to oil and natural gas production. As many buildings in Oklahoma were constructed before this increase, it is imperative to determine the response of these buildings to significant ground motion. We use a multi-instrument approach to monitor a 12-story reinforced concrete building at Oklahoma State University (OSU), where several campus buildings experienced damage from the 2016 M5.8 Pawnee earthquake. A strong-motion accelerometer collocated with a GPS receiver were installed on the roof of the building, and an additional accelerometer was installed on the ground floor. Combined GPS/seismic monitoring on the roof can provide a broadband view of the shaking, particularly low-frequency motion and static offset information necessary for determining damage. Since the instrument installation in July 2017, we have recorded over 10 M4+ earthquakes. In a preliminary data assessment, we find shaking amplification ratios of the roof relative to the ground floor are 2.1 and 2.5 in the E-W and N-S directions, respectively, consistent with the structure’s rectangular shape and orientation.

The maximum magnitude of induced earthquakes is not known and remains controversial, however estimates of acceleration levels with a given probability of exceedance are now calculated annually using methodology consistent with the National Probabilistic Seismic Hazard Assessment maps. These are useful tools that are made available to the engineering community. To build on that effort, we are calculating scenario ground motions for the OSU study site to be made available for estimating the expected building response to larger earthquakes. We will generate synthetic waveforms from a suite of ruptures using the frequency-wavenumber approach to compute Green’s functions for frequencies <1 Hz, combined with stochastic high-frequency waveform components generated using the SCEC Broadband Platform. We first generate synthetic ruptures along the Sooner Lake Fault, which ruptured in the 2016 Pawnee earthquake. We compare our synthetic waveforms with observations from the 2016 Pawnee earthquake to verify the approach. We are using a M4.6 earthquake from April 2018 to assess the consistency of the simulations with new observed data at the study site. For the future scenario calculations, the ruptures are based on two known faults near OSU, the Stillwater and Lake Carl Blackwell faults.

Citation
Saunders, J. K., Martinez, F., Haase, J. S., & Soliman, M. (2018, 08). Simulated ground motions for induced seismicity at a 12-story structure in Oklahoma using the SCEC Broadband Platform. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions