Risk from Oklahoma’s Induced Earthquakes: The Cost of Declustering
The U.S. Geological Survey (USGS) has for each year 2016–2018 released a one‐year seismic hazard map for the central and eastern United States (CEUS) to address the problem of induced and triggered seismicity (ITS) in the region. ITS in areas with historically low rates of earthquakes provides both challenges and opportunities to learn about crustal conditions, but few scientific studies have considered the financial risk implications of damage caused by ITS. We directly address this issue by modeling earthquake risk in the CEUS using the 1 yr hazard model from the USGS and the RiskLink software package developed by Risk Management Solutions, Inc. We explore the sensitivity of risk to declustering and b‐value, and consider whether declustering methods developed for tectonic earthquakes are suitable for ITS. In particular, the Gardner and Knopoff (1974) declustering algorithm has been used in every USGS hazard forecast, including the recent 1 yr forecasts, but leads to the counterintuitive result that earthquake risk in Oklahoma is at its highest level in 2018, even though there were one‐fifth as many earthquakes as occurred in 2016. Our analysis shows that this is a result of (1) the peculiar characteristics of the declustering algorithm with space‐varying and time‐varying seismicity rates, (2) the fact that the frequency-magnitude distribution of earthquakes in Oklahoma is not well described by a single b‐value, and (3) at later times, seismicity is more spatially diffuse and seismicity rate increases are closer to more populated areas. ITS in Oklahoma may include a combination of swarm‐like events with tectonic‐style events, which have different frequency–magnitude and aftershock distributions. New algorithms for hazard estimation need to be developed to account for these unique characteristics of ITS.
J. Maurer et al., "Risk from Oklahoma’s Induced Earthquakes: The Cost of Declustering," Bulletin of the Seismological Society of America, vol. 20, Seismological Society of America, Apr 2020.
The definitive version is available at https://doi.org/10.1785/0120190268
Geosciences and Geological and Petroleum Engineering
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07 Apr 2020