Moment Tensor Estimation using a Grid-Search approach for the Pawnee, Oklahoma Mw 5.8 Earthquake
Abstract
Following the 5.8 Mw earthquake in Pawnee, Oklahoma, a series of moment tensor solutions were published by the National Earthquake Information Center (NEIC). While all solutions were in relative agreement that the focal mechanism was vertical strike slip in nature there is a great deal of variance in the optimal depth and double couple percentage. Such a variance in depth solutions is particularly important in interpretation as Oklahoma is actively engaging in hydrocarbon production and waste-water disposal. The GCMT solution using teleseismic long period surface waves favors a deep ( 18 km) strong double couple solution ( 97%). In contrast, long period body wave and regional moment tensor solutions favor intermediate depth ( 10 km) and double couple solutions ( 75%) and the high frequency body wave solutions prefers a shallow depth ( 2 km) marginal double couple solution ( 56%). The depth using traditional travel time location techniques at the NEIC was 5.6 +/- 1.3km. The intent of this study is to assess the uncertainty in the moment tensor estimation using an exhaustive parameter grid-search strategy recently developed by Tape and Tape (2015). Using this approach we systematically scan through depths and moment tensors and for each depth moment tensor pair compute a misfit function. To better understand how our different datasets add information to estimating the unknown parameters we apply the proposed methodology to regional surface waves, teleseismic body waves, and, finally, both surface and teleseismic body waves. We present not only the best solution but a set of plausible moment tensors at each depth. A desirable consequence of this abstract would be to demonstrate that the differing solutions submitted to the NEIC are plausible in the sense that they best explain the data used in their respective inversions but may not necessarily adequately resolve a particular model parameter. http://earthquake.usgs.gov/earthquakes/eventpage/us10006jxs#moment-tensorTape, W. & Tape, C., 2015. A uniform parameterization of moment tensors, Geophys. J. Int., 202, 2074-2081.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.S51E3176F
- Keywords:
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- 7215 Earthquake source observations;
- SEISMOLOGYDE: 7230 Seismicity and tectonics;
- SEISMOLOGY