ML23257A188
| ML23257A188 | |
| Person / Time | |
|---|---|
| Issue date: | 09/30/2023 |
| From: | Rasool Anooshehpoor, Mueller C, Shumway A NRC/RES/DE/SGSEB, US Dept of Interior, Geological Survey (USGS) |
| To: | |
| Rasool Anooshehpoor 301-415-2396 | |
| References | |
| Download: ML23257A188 (31) | |
Text
Induced Seismicity and its Impact on Existing Seismic Hazard Analysis Date Published: September 2023 Prepared by:
C. Mueller A. Shumway U.S. Geological Survey Geologic Hazards Science Center 1711 Illinois St.
Golden, CO 80401 Rasool Anooshehpoor, NRC Program Manager Technical Letter Report U.S. Geological Survey, Geologic Hazards
DISCLAIMER The development of this Technical Letter Report was sponsored by the U.S. Nuclear Regulatory Commission (NRC). The views and conclusions contained in the document are those of the authors and should not be interpreted as necessarily representing the official policies of the U.S.
Government.
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ABSTRACT We develop a scheme for mapping changes in earthquake rates within a region in near-real-time. A specific goal of the work is to track recent changes in the rates of induced earthquakes in the central and eastern United States. We map rates in a time window of interest, map rates in a preceding time window, and then ratio the two maps to show changes. A proof-of-concept map is first prepared, comparing rates during the first six months of 2010 with rates from the preceding five years; this demonstration map shows, among other things, the growth of induced seismicity in Oklahoma during 2010. We then present a series of ten ratio maps: the first six months of 2018 compared with the preceding five years, and so on in six-month increments through the end of 2022. These maps show changes in the rates and locations of induced earthquakes, as well as other seismicity trends. Map regions, time windows, and other model parameters are easily adaptable for other applications.
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FOREWORD For the past five years, the United States Geological Survey (USGS) has been conducting research to support the United States Nuclear Regulatory Commissions seismic hazard analysis, specifically when related to induced seismicity in the central and eastern United States and its impact on existing seismic hazard analysis. This document serves to report the USGS findings.
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TABLE OF CONTENTS DISCLAIMER ............................................................................................................................... iii ABSTRACT .................................................................................................................................. v FOREWORD ............................................................................................................................... vii LIST OF FIGURES ...................................................................................................................... xi EXECUTIVE
SUMMARY
........................................................................................................... xiii ABBREVIATIONS AND ACRONYMS ....................................................................................... xv 1 Induced Seismicity and its impact on Existing Seismic Hazard Analysis ..................... 1-1 1.1 Introduction .................................................................................................................... 1-1 1.2 Methodology ................................................................................................................... 1-1
1.3 Demonstration
January - June 2010 ............................................................................ 1-2 1.4 Results ........................................................................................................................... 1-6 1.5 Conclusions .................................................................................................................. 1-17 1.6 References ................................................................................................................... 1-17 ix
LIST OF FIGURES Figure 1-1: Seismicity rate grid for the first six months of 2010 (January 1, 2010 -
June 30, 2010); this is the numerator grid for the demonstration case. ............. 1-3 Figure 1-2: Seismicity rate grid for the five years preceding the first six months of 2010 (January 1, 2005 - December 31, 2009); this is the denominator grid for the demonstration case. ......................................................................... 1-4 Figure 1-3: Ratio grid for the demonstration case. Note, in particular, the strong increase in induced seismicity in Oklahoma. ...................................................... 1-5 Figure 1-4: Ratio grid for January 1, 2018 - June 30, 2018; denominator is the grid for preceding five years (January 1, 2013 - December 31, 2017). .................... 1-7 Figure 1-5: Ratio grid for July 1, 2018 - December 31, 2018; denominator is grid for preceding five years (July 1, 2013 - June 30, 2018). ......................................... 1-8 Figure 1-6: Ratio grid for January 1, 2019 - June 30, 2019; denominator is grid for preceding five years (January 1, 2014 - December 31, 2018)........................... 1-9 Figure 1-7: Ratio grid for July 1, 2019 - December 31, 2019; denominator is grid for preceding five years (July 1, 2014 - June 30, 2019). ....................................... 1-10 Figure 1-8: Rate grid for January 1, 2020 - June 30, 2020; denominator is grid for preceding five years (January 1, 2015 - December 31, 2019)......................... 1-11 Figure 1-9: Ratio grid for July 1, 2020 - December 31, 2020; denominator is grid for preceding five years (July 1, 2015 - June 30, 2020). ....................................... 1-12 Figure 1-10: Ratio grid for January 1, 2021 - June 30, 2021; denominator is grid for the preceding five years (January 1, 2016 - December 31, 2020)................... 1-13 Figure 1-11: Ratio grid for July 1, 2021 - December 31, 2021; denominator is for grid for preceding five years (July 1, 2016 - June 30, 2021)................................... 1-14 Figure 1-12: Ratio grid for January 1, 2022 - June 30, 2022; denominator is grid for preceding five years (January 1, 2017 - December 31, 2021)......................... 1-15 Figure 1-13: Ratio grid for July 1, 2022 - December 31, 2022; denominator is grid for preceding five years (July 1, 2021 - June 30, 2022). ....................................... 1-16 xi
EXECUTIVE
SUMMARY
To support the United States Nuclear Regulatory Commissions seismic hazard analysis, specifically when related to induced seismicity in the central and eastern United States and its impact on existing seismic hazard analysis, we develop a scheme for mapping changes in earthquake rates within a region in near-real-time. A specific goal of the work is to track recent changes in the seismicity rates of induced earthquakes in the central and eastern United States.
We did this by developing a methodology that maps rates in a time window of interest, map rates in a preceding time window and then ratio the two maps to show changes. As part of this methodology, we develop a water level technique for stabilizing the grids ratios. A proof-of-concept map is first prepared, comparing rates during the first six months of 2010 with rates from the preceding five years; this demonstration map shows, among other things, the growth of induced seismicity in Oklahoma during 2010. We then present a series of ten ratio maps: the first six months of 2018 compared with the preceding five years, and so on in six-month increments through the end of 2022. These maps show changes in the rates and locations of induced earthquakes, as well as other seismicity trends. The maps highlight some interesting recent seismicity trends, notably in Oklahoma, Kansas, Arkansas, Texas, New Madrid, and eastern Tennessee. It seems logical to assume that changes that occur in regions of known induced seismicity arise from changes in the rates or locations of induced earthquakes, but independent information would be needed to confirm this. Similarity, independent information would be needed to understand whether any new trends were induced or natural. Map regions, time windows, and other model parameters are easily adaptable for other applications.
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ABBREVIATIONS AND ACRONYMS CEUS Central and eastern United States Jan January Jul July km Kilometer mos Months NRC United States Nuclear Regualtory Comission NSHM National Seimsic Hazard Model s Smoothing parameter (e.g., 15 or 50 km)
SHA Seismic hazard analysis USGS United States Geological Survey y, yrs Years (e.g., 0.5 [6 months] or 5) xv
1 INDUCED SEISMICITY AND ITS IMPACT ON EXISTING SEISMIC HAZARD ANALYSIS This Chapter describes Task 4 - Induced Seismicity and its Impact on Existing Seismic Hazard Analysis (SHA) - of research to support the United States Nuclear Regulatory Commissions (NRC) seismic hazard analysis.
1.1 Introduction We develop a scheme for mapping changes in earthquake rates within a region in near-real-time. A specific goal of the work is to track recent changes in the rates of induced earthquakes in the central and eastern United States (CEUS). We map rates in a time window of interest, map rates in a preceding time window, and then ratio the two maps to show changes. A proof-of-concept map is first prepared, comparing rates during the first six months of 2010 with rates from the preceding five years; this demonstration map shows, among other things, the growth of induced seismicity in Oklahoma during 2010. We then present a series of ten ratio maps: the first six months of 2018 compared with the preceding five years, and so on in six-month increments through the end of 2022. These maps show changes in the rates and locations of induced earthquakes, as well as other seismicity trends. Map regions, time windows, and other model parameters are easily adaptable for other applications.
1.2 Methodology To track seismicity changes and trends over time, we map earthquake rates in a time window of interest, map rates in a preceding time window, and then ratio the two maps. A methodology first described by Frankel (1995) and Frankel and others (1996) is adapted for this study, producing gridded and smoothed maps of earthquake rates that are an intermediate step in going from an earthquake catalog to a seismic hazard map. The earthquake catalog used here was recently developed for the 2023 update of the U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) (e.g., Petersen et al., 2023).
An earthquake rate grid is developed for the CEUS by:
- 1. defining a 0.1° x 0.1° (latitude x longitude) grid that covers the region,
- 2. choosing a time window,
- 3. counting the number of earthquakes with magnitude 2.7 in the time window in each grid cell,
- 4. assuming = 1.0,
- 5. computing a scaled 10 value for each grid cell using a standard Gutenberg-Richter relationship ( ( ) = 10 ( )
, where ( ) is the number of earthquakes with magnitudes larger than ),
- 6. spatially smoothing the gridded rate values using a fixed two-dimensional Gaussian kernel, and
- 7. mapping the resulting agrid.
The agrid units in step 5 are scaled to correspond to the annual rate of magnitude 3+
earthquakes per grid cell. For each ratio map in this study, a numerator agrid is computed for a 1-1
six-month time window of interest, and a corresponding denominator agrid is computed for the preceding five years.
Smoothed agrids naturally contain grid cells with zero or very small values. To stabilize the ratios, we define a threshold rate value such that rates smaller than the threshold can be ignored, and then apply the threshold as a sort of spatial water level across the grid, replacing zero or very small values in cells with the threshold value for both the numerator and denominator grids. As an example, consider a small rate of three magnitude 2+ earthquakes per degree cell per year. With our parameter choices this corresponds to a threshold rate of 0.003 magnitude 3+ earthquake per grid cell per year.
In our application, if both the numerator and denominator values are equal (including the case where both original values have been replaced by the threshold value), they are plotted as white on the ratio map, Otherwise, ratio values are plotted using a color palette with warm colors for increasing seismicity and cool colors for decreasing seismicity.
1.3 Demonstration
January - June 2010 The first six months of 2010 were chosen as a proof-of-concept case for the methodology because of the well-known increase in induced seismicity in Oklahoma during that time. The numerator map (six-month grid with 15 km smoothing parameter) and the denominator map (preceding five-year grid with 50 km smoothing parameter) are shown in Figure 1-1 and Figure 1-2, respectively. The ratio map in Figure 1-3 shows cells with increasing rates as red or purple symbols, and cells with decreasing rates in green. Trade-offs between the threshold parameter and the smoothing parameters account for the somewhat different appearances of these two kinds of trends. The ratio map particularly highlights seismicity changes in Oklahoma, Arkansas, and Missouri.
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1-3 Figure 1-1: Seismicity rate grid for the first six months of 2010 (January 1, 2010 - June 30, 2010); this is the numerator grid for the demonstration case.
1-4 Figure 1-2: Seismicity rate grid for the five years preceding the first six months of 2010 (January 1, 2005 - December 31, 2009);
this is the denominator grid for the demonstration case.
1-5 Figure 1-3: Ratio grid for the demonstration case. Note, in particular, the strong increase in induced seismicity in Oklahoma.
1.4 Results The five-year period from 2018 through 2022 is analyzed in ten six-month increments, with the denominator grid in each case computed from the preceding five years of seismicity. The results are presented in Figure 1-4 (first six months of 2018), Figure 1-5 (last six months of 2018), and so on up to Figure 1-13 (last six months of 2022). Seismicity rates generally appear to decrease in Oklahoma, with perhaps some spatial migration (all figures). Some other areas also show interesting rate changes: the Permian Basin region in west Texas and southeast New Mexico (Figure 1-8 through Figure 1-13), south Texas (Figure 1-10 to Figure 1-13), Kansas (Figure 1-7 through Figure 1-13), the greater New Madrid region (all figures), and the greater eastern Tennessee region (all figures). Other changes are generally more localized, presumably related to individual earthquakes in most cases (all figures).
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1-7 Figure 1-4: Ratio grid for January 1, 2018 - June 30, 2018; denominator is the grid for preceding five years (January 1, 2013 -
December 31, 2017).
1-8 Figure 1-5: Ratio grid for July 1, 2018 - December 31, 2018; denominator is grid for preceding five years (July 1, 2013 - June 30, 2018).
1-9 Figure 1-6: Ratio grid for January 1, 2019 - June 30, 2019; denominator is grid for preceding five years (January 1, 2014 -
December 31, 2018).
1-10 Figure 1-7: Ratio grid for July 1, 2019 - December 31, 2019; denominator is grid for preceding five years (July 1, 2014 - June 30, 2019).
1-11 Figure 1-8: Rate grid for January 1, 2020 - June 30, 2020; denominator is grid for preceding five years (January 1, 2015 -
December 31, 2019).
1-12 Figure 1-9: Ratio grid for July 1, 2020 - December 31, 2020; denominator is grid for preceding five years (July 1, 2015 - June 30, 2020).
1-13 Figure 1-10: Ratio grid for January 1, 2021 - June 30, 2021; denominator is grid for the preceding five years (January 1, 2016 -
December 31, 2020).
1-14 Figure 1-11: Ratio grid for July 1, 2021 - December 31, 2021; denominator is for grid for preceding five years (July 1, 2016 - June 30, 2021).
1-15 Figure 1-12: Ratio grid for January 1, 2022 - June 30, 2022; denominator is grid for preceding five years (January 1, 2017 -
December 31, 2021).
1-16 Figure 1-13: Ratio grid for July 1, 2022 - December 31, 2022; denominator is grid for preceding five years (July 1, 2017- June 30, 2022).
1.5 Conclusions The maps highlight some interesting recent seismicity trends, notably in Oklahoma, Kansas, Arkansas, Texas, New Madrid, and eastern Tennessee. It seems logical to assume that changes that occur in regions of known induced seismicity arise from changes in the rates or locations of induced earthquakes, but independent information would be needed to confirm this.
Similarly, independent information would be needed to understand whether any new trends were induced or natural.
Applied in a timely manner, maps like these could certainly be used to identify areas of increasing seismicity that might be of concern for policy-making or for other practical applications. As maps, however, the results are inherently somewhat qualitative. As noted above, independent information or analysis would be required to support policy-making; in that regard its possible that other approaches might serve as well or better.
The methodology could easily be adapted to focus on a particular sub-region. In Oklahoma, for example, it might be possible to analyze migration patterns of induced seismicity in addition to rate changes in detail. Some modeling choices might benefit from deeper analysis (e.g., the threshold or smoothing parameters), but we have done some tests, and in our opinion adjusting model details within reasonable limits probably wouldnt have much effect on general outcomes.
Development of the water level technique for stabilizing the agrid ratios is a useful innovation.
1.6 References Frankel A (1995). Mapping seismic hazard in the central and eastern United States.
Seismological Research Letters (66): 8-21.
Frankel A, Mueller C, Barnhard T, Perkins D, Leyendecker E, Dickman N, Hanson S, and Hooper M (1996). National seismic-hazard maps: Documentation June 1996. U.S.
Geological Survey Open-File Report 96-532, 110 pp.
Petersen MD et al. (2023). The 2023 U.S. 50-State National Seismic Hazard Model - Overview.
Earthquake Spectra, in preparation.
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