2021 UPDATE Potential Induced Seismicity Guide A Resource of Technical & Regulatory Considerations Associated with Fluid Injection Potential Induced Seismicity Guide: A Resource of Technical and Regulatory Considerations Associated with Fluid Injection Disclaimer This is an informational document and is not intended to offer recommended rules or regulations. The Induced Seismicity Workgroup (ISWG), an effort of the State Oil and Gas Regulatory Exchange (Exchange) recognizes that management and mitigation of the risks associated with induced seismicity are best considered at the state level with specific considerations at local, regional, or cross-state levels, due to significant variability in local geology and surface conditions (e.g., population, building conditions, infrastructure, critical facilities, seismic monitoring capabilities, etc.). Neither the State Oil and Gas Regulatory Exchange (Exchange), nor the ISWG, nor any person acting on their behalf makes any warranty, express or implied; or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or reliance on any information, apparatus, product, or process disclosed; or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favor by the Exchange, the ISWG nor any person acting on their behalf. The views and opinions of authors expressed herein do not necessarily state or reflect those of the Exchange, or the ISWG. Recommended Citation Ground Water Protection Council and Interstate Oil and Gas Compact Commission. Potential Induced Seismicity Guide: A Resource of Technical and Regulatory Considerations Associated with Fluid Injection, March 2021, 250 pages. i Preface While seismicity induced by a variety of human activity has been observed and documented for decades, induced seismicity related to underground injection activities was only first recognized in the 1960s at the Rocky Mountain Arsenal near Denver. With the dramatic increase in seismicity in the southern mid-continent of the U.S. starting in 2009, followed by a significant decreasing trend since 2015, attention has been renewed on the potential hazards posed by earthquakes induced by fluid injection. The science required to understand the process and predict its impacts is ongoing. This Guide is the third edition of what was previously entitled “Potential Injection-Induced Seismicity Associated with Oil & Gas Development: A Primer on Technical and Regulatory Considerations Informing Risk Management and Mitigation.” The previous editions focused on induced seismicity associated with the underground disposal of oil and gas produced fluids in Class II wells. The purpose of this edition of the Guide is to update the science surrounding induced seismicity since 2017 and to expand on the topic of induced seismicity related to hydraulic fracturing. The Guide consists of four chapters and 12 appendices. A new topic, induced seismicity due to carbon capture and storage (CCUS), is also briefly described in Appendix H. This Guide is designed to provide state and provincial regulatory agencies with an overview of current technical and scientific information, along with considerations associated with evaluating fluid injection-induced seismicity, managing the associated hazard and risk, and developing response strategies to mitigate the occurrence and severity of the events. It is not intended to offer specific regulatory recommendations to agencies but is intended to serve as an information resource. Also, unlike prior studies by the National Research Council (NRC), U.S. Environmental Protection Agency (USEPA), Stanford University, and others, this document is not intended to provide a broad literature review. This Guide was developed the State Oil and Gas Regulatory Exchange (Exchange), an initiative of the Interstate Oil and Gas Compact Commission (IOGCC) and the Ground Water Protection Council (GWPC). The effort was led by the Induced Seismicity by Injection Work Group (ISWG), composed of representatives of state and provincial oil and gas regulatory agencies and state and provincial geological surveys, and subject matter experts from academia, industry, federal agencies, and environmental organizations. Management and mitigation of the risks associated with induced seismicity are best considered at the state level, with specific considerations at local or regional levels. A one-size-fits-all approach is infeasible, due to significant variability in local geology and surface conditions, including such factors as population, building conditions, infrastructure, critical facilities, and seismic monitoring capabilities. Appendix G includes summaries of approaches that various states have taken to address risk management and mitigation. Although important, the issues of insurance and liability are not addressed in this Guide because each state or province has unique laws that render general consideration of these topics impractical. ii Although earthquakes can be either natural (tectonic) or human-induced, this Guide uses the term “earthquake” to refer to an induced seismic event due to fluid injection. All induced seismic events of engineering and environmental relevance are earthquakes that are the result of displacement or slip on pre-existing geologic faults. Although such events are more accurately considered to be triggered, the terms “induced” and “triggered” are often used interchangeably to refer to seismicity related to human activity. “Microseismic” events due to hydraulic fracturing are generally the result of fracturing of intact rock but can be also fault-related slip events. Microseismic events are observed to be generally smaller than moment magnitude (M) 1.0. Throughout this Guide moment magnitude is used to denote the size of an earthquake unless otherwise noted. For a more complete description of moment magnitude and its relevance to the size of earthquakes, see Earthquake Magnitude in Appendix A. iii Table of Contents Preface .............................................................................................................................................. ii Executive Summary ............................................................................................................................ 1 Introduction .............................................................................................................................................. 1 Understanding Induced Seismicity ........................................................................................................... 2 Assessing Potential Injection-Induced Seismicity ..................................................................................... 3 Risk Management and Mitigation Strategies ............................................................................................ 4 Considerations for External Communication and Engagement ................................................................ 5 Key Message ............................................................................................................................................. 7 Chapter 1: Understanding Induced Seismicity .................................................................................... 8 Chapter Highlights..................................................................................................................................... 8 Introduction—Key Concepts and Earthquake Basics ................................................................................ 8 Magnitude and Depth of Induced Earthquakes ...................................................................................... 12 Hazards and Risks of Induced Seismicity ................................................................................................ 13 Ground Motion Models (GMMs) for Induced Seismicity ........................................................................ 14 Examples of Current Models ................................................................................................................... 14 USGS Hazard Maps .................................................................................................................................. 15 Estimated Number of Induced Seismicity Locations .............................................................................. 17 How Fluid Injection May Induce Earthquakes ........................................................................................ 18 Potential for Seismicity Related to Hydraulic Fracturing ........................................................................ 20 Future Research ...................................................................................................................................... 21 Chapter 2: Assessing Potentially Injection-Induced Seismicity ........................................................... 22 Chapter Highlights................................................................................................................................... 22 Introduction ............................................................................................................................................ 22 Contemporary Seismicity .......................................................................................................................