Oklahoma Earthquakes: Trends and Underlying Causes. Jeremy Boak, Oklahoma Geological Survey October 21, 2016

Transcription

1 Oklahoma Earthquakes: Trends and Underlying Causes Jeremy Boak, Oklahoma Geological Survey October 21,

2 The Oklahoma Geological Survey is a state agency for research and public service located on the Norman Campus of the University of Oklahoma and affiliated with the OU College of Earth and Energy. The Survey is chartered in the Oklahoma Constitution and is charged with investigating the state's land, water, mineral, and energy resources and disseminating the results of those investigations to promote the wise use of Oklahoma's natural resources consistent with sound environmental practices. We are not a regulatory authority 2

3 Acknowledgments OGS Staff Engaged on the Seismicity Issue Seismology: Jefferson Chang, Fernando Ferrer, Noorulann Ghouse, Junjun Hu, Andrew Thiel, Isaac Woelfel Hydrogeology, Geology, Geophysics: Kyle Murray, Richard Andrews, Kevin Crain, Steve Holloway, Jordan Williams Publications & Outreach: Ted Satterfield

4 OGS Uses about 40 Stations to Locate Oklahoma Earthquakes

5 Measuring an Earthquake Magnitude - a scaled estimate of energy released as seismic waves, proportional to rupture area Magnitude measured multiple ways (M L, m b, M w, M o, M s ) Magnitude estimates rarely the same between different methods All magnitude measures are uncertain Magnitude scales logarithmic (+1 unit of magnitude = ~10 times shaking & ~32 times the energy release) Earthquake Intensity is a qualitative estimate (using Modified Mercalli scale ranging from I-XII) 5

6 Earthquake Magnitude & Frequency Magnitude Earthquakes Energy Equivalents Richter Scale (logarithmic) Largest recorded earthquakes Vast destruction Massive loss of life Great earthquake Severe impact Large loss of life Strong earthquake Damage in $Billions Some loss of life Moderate earthquake Property damage Light earthquake Some property damage Minor earthquake Felt by humans Injection induced earthquakes Typical <3.5 (Highest recorded = 5.6) Chile (1960) Alaska (1964) Sumatra (2004) Chile (2010) New Madrid (1812) San Francisco (1906) Charleston SC (1886) Haiti (2010) Loma Prieta (1989) Northridge (1994) Long Island (1884) < ,500 10, ,000 Krakatoa eruption Frequency of Occurrence Avg. per year (est.) World s largest nuclear test (USSR) Mount St Helens eruption Hiroshima atomic bomb Average Tornado Average tornado Large Lightning Bolt Large lightning bolt Oklahoma city bombing Moderate lightning bolt Magnitude 2.0 and below = typical micro-seismic events

7 Earthquakes Alfalfa Grant Woods Noble Pawnee Garfield Payne Logan Lincoln Okfuskee Oklahoma Seminole 7

8 Earthquakes Alfalfa Grant Woods Noble Pawnee Garfield Payne Logan Lincoln Okfuskee Oklahoma Seminole 8

9 Source:

10 USGS 1-Year Projection Validated 10

11 Pawnee Earthquake (M5.8-76% of 2016 Seismic Energy) 11

12 Galena Township Fault 15% of 2016 Seismic Energy Oklahoma Geological Survey Dr. Jeremy Boak, Director 11 July 2016 M4+ aftershocks in Woods County Time: 2016 July 08 21:04:27.5 (CDT) Magnitude: 4.4 Mw Epicenter: , Depth: 7.1 km Time: 2016 July 08 17:29:38.0 (CDT) Magnitude: 4.2 Mw 6 Epicenter: , Depth: 6.4 km The recent M4.2, M4.2, and M4.4 that occurred on 2016 July 08 are considered aftershocks of the M5.1 earthquake that happened on 2016 Feb 13. This sequence brings the total of M4 or greater aftershocks on the Galena Township Fault Zone (GTFZ) up to eight. Empirical relations from global observations suggest that a few more aftershocks of M4+ are expected to occur on the GTFZ, as the crust adjusts to the displacement done by the M5.1 mainshock. Clustered aftershocks of similar magnitude are not uncommon in seismically active regions. The duration of aftershock sequences is typically longer in mid-continental settings than along plate boundaries. We derived three focal plane solutions (FPS or beachball diagrams) from each event that indicate strike-slip displacement dominated the motion along the fault. In case of further seismicity, we urge the public to protect themselves from falling objects: (1) drop to the ground; (2) cover your head and neck; and (3) hold on to any sturdy cover. Time: 2016 July 08 16:31:57.7 (CDT) Magnitude: 4.2 Mw Epicenter: , Depth: 7.3 km 12

13 Earthquakes Occur in Basement, on Optimally Aligned Faults Number of Earthquakes Earthquakes Ave. = 5.4±1. 6 Active Fault Orientations 2014 Maximum Horizontal Stress Depth (km) OGS OF

14 Oklahoma M2.8+ Earthquakes Earthquakes per Day M2.8+ Earthquakes 30 Day Mov. Avg. 180 Day Mov. Avg. 1 0 Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16 Jan-17 14

15 Human Activity Can Induce Earthquakes Fluid Pressure increase from injection Figure modified from: 15

16 Underground Injection Control (UIC) Class II Injection Salt Water Disposal (SWD) Wells Murray 2014, OGS OF

17 Earthquake Activity Occurs Where Deep Injection Increases Substantially Source: Walsh, F. R., and Zoback, M. D. (2015) Oklahoma s recent earthquakes and saltwater disposal. Sci. Adv. 2015; 1:e , 18 June

18 Areas of Lower SWD Show Lower Earthquake Activity Source: Walsh, F. R., and Zoback, M. D. (2015) Oklahoma s recent earthquakes and saltwater disposal. Sci. Adv. 2015; 1:e , 18 June

19 SWD Includes Very Little Flowback Water from Hydraulic Fracturing Source: Walsh, F. R., and Zoback, M. D. (2015) Oklahoma s recent earth-quakes and saltwater disposal. Sci. Adv. 2015; 1:e , 18 June

20 Earthquakes per Day Earthquakes, Oil and Water M2.8+ Earthquakes 684 Arbuckle Well Injection Oklahoma Oil Production 6 Month Moving Average Daily Injection/Production (Millions of barrels) Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16 Jan-17 20

21 Earthquake Year-to-Year Comparison /05/ /05/ M3.0+ Earthquakes M3.5+ Earthquakes J F M A M J J A S O N D J 0 J F M A M J J A S O N D J 21

22 Simplified Regional Grouping Northwest Grant Alfalfa Northwest North Central Woods Noble Pawnee Garfield Payne Logan Central Lincoln Okfuskee Oklahoma Seminole South 22

23 Three Large Quakes Dominate Energy Release 1,000,000 Seismic Moment by Region Seismic Moment (Trillion N-m) 800, , , ,000 M5.0+ Rest of OK North Central Northwest Central South

24 Earthquake Forecasting Probability of one or more earthquakes of magnitude (m) over the specified time Not a prediction, but a forecast Shorter the period, the more uncertain the estimate August 2016 Magnitude (M L ) Duration Year Year months days days Probabilities are expressed as values from 0 to 1. To transform probabilities to percent, multiply by 100.

25 Earthquake Forecasting Probability of one or more earthquakes of magnitude (m) over the specified time Not a prediction, but a forecast Shorter the period, the more uncertain the estimate October 10, 2016 Magnitude (M L ) Duration Year Year months days days Probabilities are expressed as values from 0 to 1. To transform probabilities to percent, multiply by 100.

26 Summary: Induced Seismicity in Oklahoma No documented case of induced seismicity comes close to the current earthquake rates or the area over which the earthquakes are occurring in Oklahoma The OGS considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in SWD wells. Hydraulic fracturing flowback water only contributes a small amount to the SWD apparently responsible for the observed rate of earthquakes The drop in earthquake frequency over the past year likely results from decreases in injection in the Area of Interest driven both by oil price and by Corporation Commission actions

27 Backup Material 27

28 Seismic Activity Shifts Regionally Through Time 900,000 Seismic Moment by Region Seismic Moment (Trillion N-m) 800, , , , , , , ,000 Rest of OK North Central Northwest Central South

29 Cumulative Seismic Moment (Energy) by Year 1,000,000 Cumulative Seismic Moment (Trillion N-m) 100,000 10,000 1, J F M A M J J A S O N D J 29

30 Oklahoma Earthquakes Cumulative Frequency Magnitude 30

31 Pattern of Larger Earthquakes 36 Lincoln County Earthquakes 37.2 Galena Township Fault Woods & Major Galena Twp Fault 36.8 Latitude Wellston Prague Lincoln Longitude Latitude Longitude 31

32 Lincoln County Earthquakes Cumulative Frequency Lincoln Prague Wellston Magnitude 32

33 Woods and Major County Earthquakes Cumulative Frequency Woods & Major Galena Twp Fault Magnitude (M L ) 33

34 Most Earthquakes Occurring in ~16% of the Area of the State Alfalfa Grant Woods Noble Pawnee Garfield Payne Logan Lincoln Oklahoma 34

35 Earthquake Capital of the U. S.? Oklahoma 2015 Cumulative Frequency Oklahoma 2014 Oklahoma 2011 California Magnitude 35

36 USGS 1% Hazard Map 36

37 Sources of Injection-Induced Seismicity 1. Produced-water disposal Water produced in conjunction with oil Typically, for every 1 bbl of oil, 5-10 bbl of water are produced (global est.) Water is salty and normally not useful Injection is optimal method for salt water disposal Re-use is becoming more attractive and popular especially in hydraulic fracturing 2. Enhanced oil recovery (EOR) wells Rarely causes earthquakes because normally as much fluid is extracted as is injected but a few cases identified. PRODUCED-OIL vs WATER Barrels Produced ENHANCED OIL RECOVERY WELLS Equal Amounts of Fluid In & Out