Ground motions from induced earthquakes in Oklahoma and Kansas: influence of local crustal structure
Abstract
Ground motions from induced earthquakes in Oklahoma and Kansas exhibit near-source (0-50 km) distance-attenuation that is distinct from what is modeled by current ground motion prediction equations (GMPEs). Waveforms from well recorded earthquakes in Oklahoma contain strong multiples, with successive phases controlling the strong ground motions at increasing distances. Waveform modeling, with a 1-D seismic velocity model containing a strong impedance contrast between basement and overburden, reproduces these features. Modeling indicates strong sensitivity of the ground motion distance-attenuation to earthquake depth, to the overburden thickness and seismic impedance with basement rocks, and to the location of the rupture with respect to strong impedance contrasts within the upper crust. Because of the strong influence of this sedimentary layer, which thins to the northeast, and which occurs throughout much of the parts of Oklahoma that are experiencing induced earthquakes, we also investigate the effects on ground motions using 3-D earthquake simulations. We develop a 3-D seismic velocity model from borehole data and carry out low-frequency (f<1 Hz) finite-element ground motion simulations. These simulations show strong azimuthal and frequency-dependent variations in the peak motions and suggest that 1- and 3-D wave propagation features should be considered in the development of mean GMPEs and in interpreting ground motion variability. The waveform observations and modeling results are important for understanding induced earthquake ground motions in Oklahoma and Kansas, and their applications to seismic hazard. The apparent attenuation of these ground motions suggests that the lateral extent of current, 1-year seismic hazard forecasts for induced earthquakes may be too large. Future GMPEs (and other seismological studies) for this region will benefit by incorporating effects from these important regional wave-propagation features.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.S22B..04M
- Keywords:
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- 4475 Scaling: spatial and temporal;
- NONLINEAR GEOPHYSICS;
- 7209 Earthquake dynamics;
- SEISMOLOGY;
- 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGY;
- 8164 Stresses: crust and lithosphere;
- TECTONOPHYSICS