Fracking has helped to usher in an era of energy abundance in the United States. This advanced drilling procedure has helped the nation to attain the status of the largest producer of crude oil and natural gas in the world, but some of its negative externalities, such as human-induced seismicity, can no longer be ignored. The occurrence of earthquakes in communities located at proximity to disposal wells with no prior history of seismicity has shocked residents and have caused damages to properties. It has evoked individuals’ resentment against the practice of injection of fracking’s wastewater under pressure into underground disposal wells. Though the oil and gas companies have denied the existence of a link between such a practice and earthquakes and the local and state governments have delayed their responses to the unforeseen seismic events, the issue has gained in prominence among researchers, affected community residents, and the media. This case study has offered a glimpse into the varied responses of stakeholders to human-induced seismicity in a small city in the state of Texas. It is evident from this case study that although individuals’ complaints and protests from a small community may not be successful in bringing about statewide changes in regulatory policies on disposal of fracking’s wastewater, they can add to the public pressure on the state government to do something to address the problem in a state that supports fracking.

## KEY MESSAGE

1. Scientific investigations have revealed that the injection of wastewater from fracking under high pressure into underground disposal wells can induce seismicity in certain geologic areas with fault lines.

2. Human-induced seismicity has negatively impacted communities by disrupting people’s lives and causing damage to physical structures.

3. Individuals living in communities affected by human-induced seismicity have blamed oil and gas companies for the earthquakes and the state government for providing inadequate protection from the adverse consequences of fracking.

## INTRODUCTION

In the quest for energy independence and the need to reduce imports of crude oil and natural gas, hydraulic fracturing (fracking) continues to receive support from both the federal and state governments of the United States. Fracking is an unconventional drilling procedure that involves both vertical and horizontal drillings. It has enabled oil and gas companies to extract crude oil and natural gas from the pores of deep-seated sedimentary or shale rocks that lie thousands of feet below the ground—once considered inaccessible in the past.

The proliferation of fracking in the United States has ushered in an era of self-sufficiency in crude oil and natural gas production. Currently, the United States is the largest producer of fossil fuels. It has surpassed the production levels of Russia, Saudi Arabia, and other oil and gas producing countries and has attained the status of an exporter of oil and natural gas. The United States exports approximately two billion barrels of crude oil along with natural gas a day [1] from the Gulf ports to Mexico and other countries [2]. In the domestic market, the abundance of crude oil and natural gas helps keep energy prices low, allows for a gradual transition from coal to natural gas in power plants, and fuels the development of the petrochemical industry along the Gulf coast [1].

Despite the many economic benefits of fracking, it has some negative externalities that have become evident over time. One such externality is induced seismicity. It can be triggered either by injection of saltwater during fracking or during disposal of its wastewater. In western Canada, seismicity from the former type is evident while in the Midwestern states of the United States seismicity from the latter type is more common [3]. This type of externality was unforeseen when fracking was in its nascent stage. With the expansion of fracking in the United States, the number of isolated and sporadic seismic events in communities located near disposal wells has increased. These earthquakes of low- and moderate-intensity disrupt individuals’ lives in communities, render damages to properties, and lower home prices by 3.5–4.7% [4].

Consequently, individuals in affected communities have blamed it on wastewater disposal. There exist no state or federal regulations to control this activity. Although in the oil and gas producing states there exist regulatory frameworks to safeguard potable water from wastewater disposal activity (as per the requirements of the federal Safe Drinking Water Act), but they do not offer protection from seismic hazards emanating from the disposal well sites [5]. This has raised concerns in communities located at proximity to disposal well sites and affected by induced seismicity.

Wastewater is a by-product produced at oil and natural gas extraction sites using both conventional and unconventional methods. It is comprised of flowback fluids containing heavy metals, radionuclides, and brine water. There exist differences in the disposal of wastewater produced by the two types of methods. Wastewater from the conventional method of production is disposed into “injection wells” located in the extraction zones. This helps to maintain pore pressure at the sites of oil and natural gas recovery or enhance oil recovery and thereby reduces the risk of seismic hazards. However, in the case of fracking, there exist two disposal options for wastewater—recycling or storage in “disposal wells.”

In recycling fracking’s toxic wastewater, municipal sewage plants in most states are not adequately equipped to remove all its toxicity completely [6]. This calls for recycling in a separate or a mobile facility located close to the production sites [7]. Since recycling of fracking’s wastewater is expensive, it is not compulsory, and most states only encourage recycling. This has prompted oil and gas companies to choose the less expensive option of transferring the wastewater from production sites to store in disposal wells. These underground wells in the impermeable layers of rock are found in non-oil producing regions. Although their walls are lined with concrete to prevent the seepage of highly toxic wastewater into the underground aquifer, this does not help to prevent earthquakes. Studies have revealed that injection of wastewater under pressure into disposal wells leads to an increase in net fluid volume and pore pressure over time which weakens pre-existing faults and causes shifting of stress. This translates into seismic hazards for communities located close by [8].

Researchers from academic institutions and the United States Geological Survey (USGS) have expressed significant interest in stray cases of human-induced seismicity in various parts of the country around disposal well sites. An investigation into such occurrences of seismicity has led to several explanations that have linked wastewater disposal activities to induced earthquakes. For instance, geologists attributed the injection of brine water under pressure into a separate saltwater disposal well as the cause of sequential sudden seismic activity in the Dallas-Fort Worth area of Texas. The injection reactivated a normal fault and led to the release of the existing tectonic stress-causing seismic tremors [9]. In the United States mid-continent, several large earthquakes between 2011 and 2012, including one in central Oklahoma that recorded 5.6 on the Richter scale, also occurred around disposal well sites. These earthquakes have all been attributed to the disposal of large volumes of wastewater into underground wells, elevating pore pressure in the underlying rocks, and weakening the existing faults [5]. During the same period, a series of small tremors occurred in Youngstown, Ohio. Since this city had no prior history of earthquakes, the investigation into their cause once again revealed that disposal activity into a deep well led to an increase in pore pressure along the pre-existing subsurface faults located just below the wellbore. With the decrease in the volume of wastewater and the injection rate, the number of seismic tremors also declined in this area [10].

Analysis of data on injection volumes and pressure along with seismic locations and dates have helped scientists to reveal a spatial and temporal correlation between seismicity and wastewater injection volumes. Its evidence could be found in the Ellenberger formation of North Texas [11] and in Venus, Texas where a 4.0 magnitude earthquake was recorded in 2015. Examination of the Venus earthquake revealed that use of high injection volume and pressure in the disposal activity led to the buildup of pore pressure. This was followed by the release of a large amount of energy through a high-intensity earthquake [12].

The high- and low-intensity earthquakes near disposal well sites in the states of Texas, Oklahoma, Colorado, Ohio, Arkansas, New Mexico, and Virginia have made communities located near well sites to demand protection from the government through regulations. This has made the oil and gas companies to deny the existence of a link between disposal activity and seismic hazards. Even the state governments have sided with the oil and gas industry in the absence of scientific evidence [13]. But with the availability of data collected from earlier well sites by scientists and the USGS [14], the problem of human-induced seismicity from industrial activity can no longer be ignored. This is evident from the case of Azle, Texas.

## THE CASE STUDY

The city of Azle is in the Barnett Shale of Texas. From 2013 to 2014, it experienced intermittent seismic tremors due to wastewater disposal activity outside the city’s boundary. The unexpected tremors evoked varied responses from frustrated residents, public officials, and scientists. This has helped to pose the questions in this study—how do affected individuals, public officials, and scientists respond to unexpected earthquakes in a city and what are the outcomes of those responses? To answer this question, a qualitative approach was undertaken in this study, and information was obtained from interviews and content analysis of both peer and non-peer reviewed articles from credible sources.

### Methods

In the collection of primary information, telephone interviews were conducted with open-ended questions that lasted for 30 min. A city official, two environmental activists, a geologist, and a journalist from a nearby city’s local newspaper who reported the episodic earthquakes were interviewed for this study. Since the study was undertaken a few years after the earthquakes had stopped, it was difficult to identify affected individuals in the absence of group formation. To substantiate the information from individuals, local and state newspapers were searched using keywords like “Azle” and “earthquakes,” and they yielded valuable information. This was followed by content analysis of websites of state and local governments, non-profit organizations, and peer-reviewed journal articles using keywords. This helped to collect information on possible causes of earthquakes and public officials’ responses and actions amidst public complaints.

## CASE EXAMINATION

### Earthquakes in Azle

With a population of 10,960 people [15], the city of Azle lies close to the Dallas-Fort Worth metroplex area. Located 14 miles north of the larger city of Fort Worth, this city straddles the Tarrant and Parker Counties. With a land area of 8.2 square miles, Azle is considered a small city in the large state of Texas. Despite its small size, it still managed to garner a lot of media attention when 30 or more earthquakes occurred in this city from 2013 to 2014. These earthquakes ranged in intensity from 2.0 to 4.0 on the Richter scale, with the highest one recording 3.6 [16].

The intermittent earthquakes in Azle managed to send shockwaves among city residents. Since the city had no history of earthquakes for the past 150 years, the episodic tremors surprised the residents and rattled their nerves. Even the city’s building code did not consider the possibility of earthquakes. Hence, the seismic tremors left behind a trail of damages. These included cracked walls and foundations, opened sinkholes, broken water pipes, disrupted sewer systems, and shattered glass from windows. Further, in the absence of earthquake insurance, which is unheard of in this area, homeowners raised the question of who is going to pay for the repair costs? Buying earthquake insurance did not seem like a panacea to the problem since insurance companies refused to pay for damages that had occurred before purchase. Also, the purchase of such insurance would add US$400 or more to existing homeowner’s insurance costs [17]. In trying to account for the recurring earthquakes, frustrated Azle residents could not blame fracking as there was no such activity within the city. They then shifted focus to the five disposal wells located outside the city’s limits. See Figure 1. Three of these wells could handle 25,000 barrels of fracking’s wastewater[18] per day while the remaining two could handle 5,000 and 10,000 barrels, respectively. The oil and gas companies immediately rejected the idea of a link between the injection of fracking’s wastewater and local earthquakes. Even the Texas Railroad Commission (TRRC), the regulatory agency overseeing crude oil and natural gas production in the state, refused to take any action and sided with the oil and gas companies in the absence of scientific evidence. FIGURE 1. Location of Azle and injection wells. Source: https://www.smu.edu/News/2015/earthquakes-azle-report-21april2015. FIGURE 1. Location of Azle and injection wells. Source: https://www.smu.edu/News/2015/earthquakes-azle-report-21april2015. ## DISCUSSION ### Responses of City Residents to Induced Seismicity The city residents knew from the beginning that the oil and gas companies who denied the existence of a link between disposal activity and earthquakes would not make efforts to mitigate environmental hazards [19]. Affected individuals with deep feelings of loss complained to the local and state governments to do something to stop the earthquakes. They not only demanded to know the cause for the earthquakes but also sought protection from the externalities of fracking. The slow response and lackadaisical attitude of the various levels of government at dealing with people’s complaints made residents seek additional help from local and national environmental organizations’ activists operating in the state. These organizations, which had assumed a protective role to safeguard the environment in the Barnett Shale, extended help to those adversely affected by the earthquakes. Environmental activists from Earthworks and North Central Texas Community Association provided support and education to victims of the earthquakes. They met with city residents and encouraged them to attend a meeting called by the TRRC. This would provide them with the opportunity to meet state regulatory officials, directly communicate their concerns and fears about earthquakes, and demand more actions for protection and safety from the local earthquakes. Convinced by the environmental activists, Azle residents responded to the call for the meeting organized by the state government agency. Approximately 800 people showed up at the town hall meeting in the city’s high school gymnasium on January 2, 2014 [17]. The large crowd surprised the TRRC’s Commissioner and two other attending state regulatory officers. At this meeting, Azle residents demanded to know who would pay for the earthquake-related damages and why actions were not being taken to stop the tremors in the city. Some of them even suggested stopping the injection of wastewater into the disposal wells to bring an end to the earthquakes. The attendees at this meeting did not hesitate to accuse the state agency of not taking their side and instead supporting the oil and gas industry [20]. Further, an environmental activist reminded both Azle residents and state officials not to overlook the possibility of earthquake-related damages to the concrete casing of disposal wells, which could lead to the contamination of groundwater in the region and add to the existing problems. ### Responses from the Government and Scientific Community #### Local Government Faced with many public complaints, the city of Azle could only take a limited approach to address the problem. Since the disposal wells were located outside the city’s limits, it lacked the authority either to halt or control the volume and injection rate of fracking’s wastewater into the disposal wells through a local ordinance. In 2015, the state of Texas pre-empted all local governments’ authority to regulate oil and gas drilling activities through the passage of House Bill 40 [21]. This bill declared that the state government had the sole authority to regulate the oil and gas industry’s activities. Thus, in a state with a long tradition of crude oil and natural gas production and a political climate that is conducive to fracking, it seemed highly unlikely that any new or stringent regulations would be adopted to address human-induced seismicity. To help city residents, the local government undertook modest initiatives to reduce the impacts of earthquakes. It educated city residents on the hazards of earthquakes, how to report them, and on the precautionary measures, they need to undertake in the event of an earthquake. To make information readily available among residents, it added a new menu item entitled “Earthquake Info” to its official website [15]. For monitoring and to learn more about the local earthquakes, the city established contacts with the USGS and the TRRC and communicated residents’ concerns to the local Congresswoman. Concurrently, it relied heavily on its fire department to plan and handle any earthquake-related emergencies in the city. #### State Government Initially, the TRRC showed reluctance to take any action on the disposal of fracking’s wastewater in the absence of scientific proof and sided with the oil and gas companies [20]. However, with the recurrence of the earthquakes in Azle and other neighboring cities and pressure from those individuals negatively impacted by them, the state’s regulatory officials organized a few meetings to collect information. At these meetings, officials mainly listened to complaints and grievances. They remained unwilling to answer individuals’ specific questions, did not make any commitments to act [17], and reminded people that decisions are not made based on emotions but rather on scientific evidence. On January 21, 2014, when the TRRC organized a meeting in the state capital of Austin, busloads of people from Azle and the neighboring cities of Reno and Springtown, which also experienced similar earthquakes, showed up at the meeting. Though individuals vociferously complained about the earthquakes, this second meeting proved to be no different from the previous town hall meeting in Azle on January 2, 2014. Once again, the TRRC officials offered no solution to citizens’ problems and individuals left Austin feeling both disappointed and frustrated. Although both the state and the agency initially displayed an apathetic attitude toward the quakes, with the realization of the seriousness of the issue, officials at TRRC voted to hire an in-house seismologist on March 28, 2014 [22]. This seemed a step in the right direction to better understand and interpret scientific evidence into the causes of such earthquakes. In May 2014, a subcommittee on Seismic Activity was created by the Texas House Committee on Energy Resources to study the increase in seismic activity in the Barnett Shale region. In 2015, the state legislature approved US$4.47 million funding for the TexNet [23] program for the installation of seismic monitors near the disposal well sites to further aid research into the increase in seismicity in North Texas [24]. As more scientific evidence became available from throughout the country, the possibility of earthquakes emanating from the disposal activity could no longer be overlooked. It prompted the TRRC to make amendments in its permit requirements for new disposal wells. See Figure 2. From October 28, 2014 onward, the agency started requiring the submission of data on seismic activities within a 100-mile radius of a proposed well along with the calculation of boundary pressure to ensure that fracking’s wastewater remains underground even under risky conditions. It also implemented other measures that include the possibility of suspending well operation activities upon suspicion of causing seismic activities in the region and required submission of well operators’ logs upon request for information on the volume and injection pressures used in the disposal of fracking’s wastewater [25].

FIGURE 2.

Varied stakeholders’ responses to human-induced seismicity in the aftermath of fracking.

FIGURE 2.

Varied stakeholders’ responses to human-induced seismicity in the aftermath of fracking.

The piece-meal approach undertaken by the state has the potential to reduce the occurrence of earthquakes from the new disposal wells, but the risk from the existing wells remained. In a state with more than 8,100 disposal wells [18], the amendment seemed inadequate in offering the needed protection to people in communities located close to disposal wells. Though the occurrences of earthquakes in Azle and its neighboring cities have gradually waned over the last few years, this cannot be fully attributed to the amendment. It has been partly due to the reduction in fracking activities in the Barnett Shale and a shift in fracking activities to the newly discovered sites in the western parts of the state. Even with the migration of fracking to the Permian Basin of the state, the risk of earthquakes in the Barnett Shale persists. In the event of a global increase in the price of crude oil and natural gas, fracking and disposal activity can gain in momentum and along with it the possibility of earthquakes [26].

#### Scientific Community

The unprecedented earthquakes in North Texas surprised the scientific community in the state. Researchers at Southern Methodist University (SMU) in Dallas, the University of Texas (UT) in Austin, and the USGS displayed an interest in investigating their cause. Though these researchers could not offer an immediate answer, they expressed the hope that with the examination and analysis of seismic data collected from nearby well sites they would be able to offer explanations. To aid their investigation, monitors were installed near the cities of Azle and Reno to collect seismic data.

Upon analysis of seismic data collected by researchers from SMU and UT Austin, the researchers presented their findings on Texas Seismicity to the Texas House of Representatives’ Energy Resources Committee on May 4, 2015 [27]. They attributed the increased seismicity in North Texas to industrial activity in the area and drew attention to similarities with other human-induced earthquakes in those areas that were not considered as seismically active regions, such as the Denver and Paradox areas of Colorado, where earthquakes had occurred in the past due to injection or removal of fluids from the rocks.

With more scientific investigation, it has become obvious now that earthquakes in Azle display more resemblance to human-induced seismicity rather than with natural tectonic activities. As there exists no evidence of active faulting in the area, fracking and related industrial activities are considered responsible for generating stress on the ancient fault system. Further, the researchers have pointed out that the changes in underground and lake water levels before and after the quakes are not linked to stress changes in the area. Instead, it is probably due to a combination of brine production and wastewater injection close to the fault zone that created enough pressure to induce the earthquakes. Such findings help to validate the need to monitor subsurface wastewater pressure formations and earthquakes of 2.0 or higher magnitude, which is not a norm in the state or the nation [28].

## CONCLUSION

It is evident from this case study that in the absence of scientific evidence, it is difficult for individuals’ complaints to gain recognition from private industry or the government. In such circumstances, public complaints are likely to be ignored and the state government is unlikely to adopt and implement a regulation that might hurt the profitability of a lucrative industry in the state that is well known for creating jobs and generating revenue. However, such behavior did not discourage city residents, and they pursued their complaints while demanding greater protections. This helped not to lose sight of the problem and maintain pressure on the state government to address it.

In the face of unexpected events, as observed in the case study, both media and scientist attentions were attracted for various reasons. The media helped to focus attention on the issue while scientists tried to seek an explanation through the collection of data. The joint efforts of media and scientists culminated into pressure on the state officials to do something to address the problem. Despite such pressure and evidence linking industrial activity to human-induced seismicity, the state officials could only adopt a soft stance due to heavy lobbying by the oil and gas industry. This resulted in amendments in existing rules that were inadequate in addressing the problem. Under such circumstances where the political climate discourages the adoption of stringent regulations, there exists the need to explore alternative and non-regulatory options.

These options have the potential to partly address the problem and can coexist with existing amendments, and they can also be either punitive or rewarding. A punitive option requires the imposition of a tax per barrel of wastewater generated at the fracking site. This can help reduce the amount of wastewater for disposal and internalize the cost imposed on homeowners from the damages caused by earthquakes [4]. On the other hand, the adoption of a reward system with an offer of monetary incentives for wastewater recycling can help to enhance the rate of recycling by the oil and gas companies. Another option is government-funded research on wastewater recycling to make the process more cost-efficient and effective. Whatever options a state may select, it is likely to depend on its political will to alleviate the problem and expend available resources. The extent of the utility of these options remains to be explored in future studies.

## CASE STUDY QUESTIONS

1. Why is the disposal of fracking’s wastewater a problem in many states?

2. In the face of public accusations and scientific evidence linking seismicity to disposal of wastewater, should oil and gas companies compensate for damages to private and public properties?

3. Discuss the potential of public opposition in bringing about relevant changes in the disposal of fracking’s wastewater.

4. Do you think that public accusations of the government taking the side of the oil and gas industry is true?

5. Discuss the role of the scientific community in drawing attention to a problem and seeking a solution to address it.

## AUTHOR CONTRIBUTIONS

SM is the single author of the case.

## COMPETING INTERESTS

The author has declared that no competing interests exist.

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