Short‐Term Hindcasts of Seismic Hazard in the Western Canada Sedimentary Basin Caused by Induced and Natural Earthquakes

Ghofrani, Hadi; Atkinson, Gail M.; Schultz, Ryan; Assatourians, Karen

doi:10.1785/0220180285

Cited by 26 publications

(41 citation statements)

References 54 publications

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“…Using regional seismograph networks (Schultz et al, 2017; Wang et al, 2017) and local arrays (Bao & Eaton, 2016; Eaton et al, 2018), seismological studies of induced seismicity in the Duvernay play consistently show that induced events exhibit strong spatiotemporal association with nearby HF operations, with dominantly strike‐slip focal mechanisms (R. Wang et al, 2016, 2017, 2018; Zhang et al, 2016). The focal depths of induced events are systematically shallower than natural seismicity (Zhang et al, 2016) and, over a broad area, the rate of induced seismicity surpasses the rate of tectonic earthquakes (Atkinson et al, 2016)—appreciably changing the seismic hazard in the region (Ghofrani et al, 2019; Schultz & Nanometrics, 2019).…”

Section: Summary Of Documented Casesmentioning

confidence: 99%

Hydraulic Fracturing‐Induced Seismicity

Schultz

Skoumal

Brudzinski

et al. 2020

Reviews of Geophysics

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Hydraulic fracturing (HF) is a technique that is used for extracting petroleum resources from impermeable host rocks. In this process, fluid injected under high pressure causes fractures to propagate. This technique has been transformative for the hydrocarbon industry, unlocking otherwise stranded resources; however, environmental concerns make HF controversial. One concern is HF‐induced seismicity, since fluids driven under high pressure also have the potential to reactivate faults. Controversy has inevitably followed these HF‐induced earthquakes, with economic and human losses from ground shaking at one extreme and moratoriums on resource development at the other. Here, we review the state of knowledge of this category of induced seismicity. We first cover essential background information on HF along with an overview of published induced earthquake cases to date. Expanding on this, we synthesize the common themes and interpret the origin of these commonalities, which include recurrent earthquake swarms, proximity to well bore, rapid response to stimulation, and a paucity of reported cases. Next, we discuss the unanswered questions that naturally arise from these commonalities, leading to potential research themes: consistent recognition of cases, proposed triggering mechanisms, geologically susceptible conditions, identification of operational controls, effective mitigation efforts, and science‐informed regulatory management. HF‐induced seismicity provides a unique opportunity to better understand and manage earthquake rupture processes; overall, understanding HF‐induced earthquakes is important in order to avoid extreme reactions in either direction.

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Section: Summary Of Documented Casesmentioning

confidence: 99%

Hydraulic Fracturing‐Induced Seismicity

Schultz

Skoumal

Brudzinski

et al. 2020

Reviews of Geophysics

Self Cite

256

176

View full text Add to dashboard Cite

show abstract

“…However, there are some differences between the present analysis shown in this report and the study from Ghofrani et al. (2019): Instead of the standard likelihood level of 2% in 50 yr used by Ghofrani et al. (2019), we use the 1% likelihood level in 1 yr, as proposed by Petersen et al.…”

Section: Discussionmentioning

confidence: 87%

“…Previous studies (Ghofrani et al., 2019; Petersen et al., 2016, 2017, 2018) have generated one‐year seismic hazard maps to include induced earthquakes explicitly. For instance, Ghofrani et al.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Short‐Term Seismic Hazard in Alberta, Canada, From Induced and Natural Earthquakes: 2011–2020

2022

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We generate short‐term seismic hazard maps for the province of Alberta, Canada, from 2011 through 2020. First, we describe the required adaptations to probabilistic seismic hazard analysis to generate short‐term seismic hazard maps, following the Monte Carlo simulation approach. Second, we identify the natural and induced seismic source areas in Alberta and estimate their earthquake recurrence parameters revealing considerable spatio‐temporal variations in the a $a$‐ and b $b$‐values in the different seismic clusters in the province. Areas with the highest short‐term seismic hazard during the last decade in Alberta are related to cases of induced seismicity, including hydraulic fracturing activities in the Duvernay Fm., near Fox Creek, and waste‐water disposal activities near the Musreau Lake. These maps provide a valuable tool to quantify the short‐term evolution in the seismic hazard, which is particularly important considering past and emerging cases of induced seismicity related to the energy sector in Alberta. Furthermore, using parameters from the previous year, we make a seismic hazard forecast for the year 2021. Our analysis provides a baseline of expected short‐term seismic hazard, with inheren uncertainty due to the assumption of unchanged recurrence parameters from the previous year; yet our study reveals pertinent seismicity patterns in line with changing human activities.

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“…As ground motion prediction equations (GMPEs) move toward source path site‐specific models, that is, nonergodic or spatially varying models (e.g., Landwehr et al, 2016), a full understanding is needed of the observed ground motion variability at any one site and the spatial correlation pattern of ground motion within a given region. By incorporating better models for uncertainty, the accuracy of hazard maps can be improved (Baltay et al, 2017; Bommer & Abrahamson, 2006; Ghofrani et al, 2019). Characteristics of ground motions presented herein provide additional quantification of the systematic uncertainty in GMPEs used to produce hazard maps and will help inform how to reduce uncertainties when improving GMPEs used for future seismic hazard estimates in Southern California.…”

Section: Introductionmentioning

confidence: 99%

Peak Ground Velocity Spatial Variability Revealed by Dense Seismic Array in Southern California

et al. 2020

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Understanding and modeling variability of ground motion is essential for building accurate and precise ground motion prediction equations, which can net site-specific characterization and reduced hazard levels. Here, we explore the spatial variability in peak ground velocity (PGV) at Sage Brush Flats along the San Jacinto Fault in Southern California. We use data from a dense array (0.6 × 0.6 km 2 , 1,108 geophones, station spacings 10-30 m) deployed in 2014 for~1 month. These data offer an opportunity to study small-scale variability in this region. We examine 38 earthquakes (2 ≤ M L ≤ 4.2) within 200 km of the array. Fault strands and a small basin impact the ground motions, producing PGV variations up to 22% of the mean and a 40% reduction in P and S wave near-surface velocities. We find along-fault rupture directivity, source, and path effects can increase PGVs by 167%. Surface PGV measurements exceed the colocated borehole station (depth at 148 m) PGV by factors of 3-10, confirming the impact on PGV from near-surface fault structures, basins, topography, and amplifications from soft sediments. Consistently, we find high PGVs within the basin structure. A pair of colocated GaM L 2.6 events produce repeatable PGV values with similar spatial patterns. The average corner frequencies of these two events are 11-16 Hz, and viable measurements of stress drop can differ by 6.45 MPa. Within this small array, the PGV values are variable implying spatial extrapolation of PGV to regions of known faults and basins, even across a small area, should be done with caution. Plain Language Summary There are an infinite number of locations where seismic waves interact with Earth's surface, yet seismologists can only record a finite set of ground motions. This requires assumptions about how known measurements or predictions can be extrapolated to nearby locations. We test to what extent extrapolation is viable using an array of 1,108 geophones installed 10-20 m apart within a 0.36 km 2 study area for 1 month atop the San Jacinto Fault in Southern California. Measuring ground motions from 38 small local earthquakes, we observe peak ground velocity (PGV) variations up to 22% across the array. We find the basin structure consistently traps energy, amplifying the seismic velocities, and that the damaged region within the fault reduces the PGVs. Comparing surface and borehole measurements (148 m deep), we find PGVs recorded at the surface are 3-10 times greater than the measurements at depth. We attribute these differences to amplification from soft sediments within the basin. We show that by leveraging information from >1,000 measurements per earthquake the ground motion velocities can be tightly constrained. These results suggest the spatial extrapolation of PGVs in regions of known faults and basins, even across a small area, should be done with caution.

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Short‐Term Hindcasts of Seismic Hazard in the Western Canada Sedimentary Basin Caused by Induced and Natural Earthquakes

Cited by 26 publications

References 54 publications

Hydraulic Fracturing‐Induced Seismicity

Hydraulic Fracturing‐Induced Seismicity

Evolution of Short‐Term Seismic Hazard in Alberta, Canada, From Induced and Natural Earthquakes: 2011–2020

Peak Ground Velocity Spatial Variability Revealed by Dense Seismic Array in Southern California

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