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Earthquakes induced by human activities can impede the development of underground resources. Significant induced events (M5) have caused both economic and human losses. The recent ML 5.6 (MW 5.1) event near Peace River, Alberta occurs in a region of in situ bitumen recovery. We find that 3.4 cm of ground deformation was caused by reverse fault slip (∼29 cm), possibly related to Peace River Arch faulting. Events are located within the shallow basement, nearby to significant wastewater injection into Paleozoic strata. We find a statistical relationship between earthquakes and injection operations. These events were likely related to the in situ bitumen development: dominantly from wastewater disposal induced pore pressure increases, with smaller poroelastic contributions from bitumen recovery. The assessment of this earthquake as induced will likely have implications for future energy development, management, and regulation—including carbon capture and blue hydrogen. Plain Language Summary: Earthquakes can be caused by underground fluid injection; cases of M5 induced events have caused damage and harm. One of the largest recorded earthquakes in Alberta (ML 5.6) occurred in a region of underground oil sand development. Here, ground shaking and deformation information are combined into an interpreted result: that ancient faults were reactivated with reverse slip. The fault slip is largely within the crystalline basement, with a small portion extending into basal sediments. Nearby injection operations dispose of petroleum‐related wastewater in these basal sediments. This earthquake was likely triggered by the injection process: injection increases pore pressure, which diffuses laterally along permeable sediments, until encountering fractured rock, which channelizes flow into the crystalline basement—the increase of pore pressure within the fault continues until reaching a critical point for slip initiation. This event likely being induced will have important implications for future operations. Key Points: On 30 November 2022 one of Alberta's largest recorded events (ML 5.6, MW 5.1) occurred in a region of in situ bitumen recoveryA well oriented fault was reactivated with reverse slip (29 cm), causing up to 3.4 cm of ground deformationThe event was likely induced by pore pressure from disposal, with smaller poroelastic stress changes from bitumen production [ABSTRACT FROM AUTHOR]

Earthquakes resulting from hydraulic fracturing (HF) can have delayed triggering relative to injection commencement over a varied range of time scales, with the majority of M ≥ 4 mainshocks occurring near/after well completion. This poses serious challenges for risk mitigation and hazard assessment. Here, we document a high‐resolution, three‐dimensional source migration process with delayed mainshock triggering that is controlled by local hydrogeological conditions near Fox Creek, Alberta, Canada. Our results reveal that poroelastic effects might contribute to induced seismicity, but are probably insufficient to activate a large fault segment not critically stressed. The rapid pore‐pressure build‐up from HF can be very localized and capable of producing large, felt earthquakes if adequate hydrological paths exist. We interpret the delayed triggering as a manifestation of pore‐pressure build‐up along pre‐existing faults needed to facilitate seismic failure. Our findings can explain why so few injection operations are seismogenic. Plain Language Summary: Fluid injection‐induced earthquakes (IIE), especially those M ≥ 4 mainshocks, are often observed to occur near or after well completion. Such delayed triggering relative to injection commencement poses serious challenges for both regulators and the energy industry to establish an effective mitigation strategy for the potential seismic risk. In this study, we reveal a high‐resolution, complex three‐dimensional pattern of IIE migration near Fox Creek, Alberta, Canada. The observed first‐outward‐then‐inward IIE sequence highlights the significance of hydrogeological networks in facilitating fluid pressure migration and the associated seismic failure. The detailed spatiotemporal distribution of IIE suggests that the effect of pore‐pressure build‐up from hydraulic fracturing (HF) can be very localized. The delayed triggering is a combined result of the fluid pressure migration and the current stress state of the hosting fault system away from the HF wells. The findings from this study also provide plausible explanations on why only a very limited number of fluid injections are seismogenic. Key Points: We document a complex 3D source migration process with delayed mainshock triggering that is controlled by a local hydrogeological settingPoroelastic effects contribute to induced events but are probably insufficient to activate a large fault segment not critically stressedRapid pore‐pressure build‐up can be very localized and lead to large earthquakes if adequate hydrological paths exist [ABSTRACT FROM AUTHOR]

Induced earthquakes caused by hydraulic fracturing are a growing concern, with risks that are often managed by traffic light protocols (TLPs). Here, we apply a risk‐informed strategy for choosing TLP red‐light thresholds. We utilize a combination of probabilistic maximum magnitudes, formation depth, site amplification, ground motion relationships, felt/damaging shaking tolerances, and population information to simulate the spatial distribution of nuisance and damage impacts. We apply this approach to many of the prominent North American shale plays that have caused earthquakes: the Horn River Basin, the Duvernay Formation, the Montney Formation, the Utica Shale, the Marcellus Shale, the SCOOP & STACK play in Oklahoma, the Eagle Ford Formation, and the Delaware Basin. We find that induced earthquake impacts are spatially heterogeneous, depending most strongly on population density. These spatial heterogeneities vary on different length scales, depending on if they are related to nuisance (longer range, 100s kms) or damage (shorter range, 10s kms). Because of this variability, we suggest an approach that sets red‐light magnitudes based on tolerances to nuisance and damage risks (varying between Mw 2.0–5.0). Comparison of the results between North American shale plays where TLPs have been enacted suggests that nuisance risks have been an influencing factor in determining red‐light thresholds. Our method provides quantitative guidelines for traffic light protocols designed in a risk‐informed manner that retains the implementational simplicity of magnitude‐based thresholds. In addition, our results provide a benchmark for jurisdictional nuisance tolerances that future TLPs could be guided by. Plain Language Summary: Subsurface injection operations, like hydraulic fracturing, have the potential to cause earthquakes. Typically, the risks of these earthquakes are managed through a traffic light protocol (TLP): a system that prescribes an operational stopping point (red‐light) for injection operations. We have devised a method to inform the choice of the red‐light threshold quantitatively in a risk‐informed manner, by considering nuisance and damage potential from earthquake ground shaking that could occur after well shut‐in. We apply this approach to the major shale plays of North America that have caused earthquakes. These risks are spatially heterogenous, so choosing a single earthquake magnitude for a red‐light would not be fair. A fairer approach would be to choose tolerances for nuisance and damage and then set the (spatially varying) magnitude such that these tolerances are not exceeded. We compare our results within shale plays, but also at a continental play‐by‐play scale. Generally, the red‐light thresholds adopted by jurisdictions reflects these differences (justifying a risk‐based approach). Examination of these differences in risk tolerances suggests consistencies within plays that could be used as guidelines for future TLPs. Overall, our method provides a means to determine red‐light thresholds, depending on a jurisdiction's tolerance to earthquake risks. Key Points: We apply a risk‐informed method for choosing induced earthquake red‐light thresholds to shale plays in North AmericaNuisance and damage risks are spatially heterogeneous both between and within the considered shale playsRed‐light magnitude thresholds based on these risks vary spatially (Mw 2.0–5.0), which argues against the use of a single threshold [ABSTRACT FROM AUTHOR]

Using data from nodal geophones and broadband seismometers, this study investigates the seismicity near Red Deer, Alberta, a region with increasing cases of hydraulic fracturing (HF)‐induced earthquakes. A cluster of 417 events was detected, and their spatial distribution and focal mechanisms reveal a NE trending rupture area with two strike‐slip fault planes. Reactivation of preexisting faults by pore pressure diffusion is likely responsible for the occurrence of the earthquake sequence following the ML 4.18 mainshock. The temporal sequence of reactivated fault orientations suggests apparent changes in the local stress field following the mainshock, which is also responsible for a remotely triggered cluster observed 1 month after the mainshock. This secondary triggering process enhances our understanding of the trailing effect of HF‐induced seismicity. Plain Language Summary: Since 2018, the Red Deer region in Alberta, Canada, has experienced an increasing number of earthquakes, most of which are associated with nearby hydraulic fracturing operations. In this study, we analyze data from a dense array of seismic sensors and regional seismometers to detect and locate events surrounding a hydraulic fracturing site near Red Deer from 4 March to 10 April 2019. The spatial distribution of the earthquakes defines a complex fault system that was activated at two different times. The results in this study signify stress changes in the shallow crust in connection with the 4.18 magnitude earthquake on 4 March 2019. Modifications to the regional stress regime are relatively long‐lived, as suggested by the continued occurrences of smaller earthquakes 1 month after the mainshock. Key Points: The spatial distribution of an induced earthquake swarm near Red Deer defines a double‐fault system that ruptured over timeFocal mechanisms exhibit a temporal sequence of strike orientations, potentially reflective of stress perturbations after the mainshockA remote aftershock cluster observed 1 month after the mainshock suggests a secondary triggered fault slip [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Copper associated hepatitis (CAH) has been increasingly recognized in dogs, and speculation exists that hereditary defects in copper metabolism have been exacerbated by increased environmental copper exposure. However, no broad epidemiological investigations have been performed to investigate quantitative hepatic copper concentrations ([Cu]H) over time in both dogs that are (predisposed breed [PB]), and are not (non‐predisposed breed [NPB]), considered at‐risk for CAH. Objectives: To investigate [Cu]H in dogs and explore temporal, demographic, and histologic associations spanning 34 years. Animals 546 archived liver specimens. Methods: Retrospective study. Searches of the Michigan State University Veterinary Diagnostic Laboratory database identified dogs that had undergone hepatic histopathologic assessment. Cases with archived tissue were reviewed and classified by breed, time period, and presence or absence of hepatitis. Inductively coupled plasma mass spectrometry was used to determine [Cu]H. Results: In time period 2009–2015, median [Cu]H were 101 μg/g and 313 μg/g greater than median [Cu]H in time period 1982–1988 for NPB and PB dogs, respectively (P <.001 for both comparisons). The proportion of dogs with [CU]H > 300 μg/g increased in NPB (28% to 49%) and PB dogs (48% to 71%) during these periods (P =.002 for both comparisons). Median [Cu]H in dogs with hepatitis increased 3‐fold over time in both NPB (P =.004) and PB populations (P <.001). Conclusions and Clinical Importance: The frequent recognition of CAH in recent years is likely due to the observed increases in [Cu]H over time. Importantly, effects are not limited to PB dogs. [ABSTRACT FROM AUTHOR]

Abstract: Focal mechanisms of induced earthquakes reflect anthropogenic contributions to preexisting geological features and fault slippages. In this paper, we examine fault‐related (double‐couple (DC)) and possibly fluid‐related (non‐double‐couple (non‐DC)) mechanisms of induced earthquakes (M2–6) at regional scales. We systematically compare well‐resolved focal mechanisms of 33 events in the Western Canada Sedimentary Basin, among which 12 were induced by hydraulic fracturing and one by secondary recovery. Most of the seismicity is dominated by strike‐slip/thrust faulting regimes, whereas limited (but consistent) non‐DC components are obtained from injection‐induced seismicity in central Alberta. We interpret the persistent compensated‐linear‐vector‐dipole components (M2.1–3.8) as reflecting fracture growth and/or noncoplanar faults slippages during hydraulic‐fracturing stimulations. We further expand the moment tensor decomposition analysis to four representative classes of induced seismicity globally and find that the overall contribution of non‐DC components is comparable between induced and tectonic earthquakes. [ABSTRACT FROM AUTHOR]

Abstract: Presently, consensus on the incorporation of induced earthquakes into seismic hazard has yet to be established. For example, the nonstationary, spatiotemporal nature of induced earthquakes is not well understood. Specific to the Western Canada Sedimentary Basin, geological bias in seismogenic activation potential has been suggested to control the spatial distribution of induced earthquakes regionally. In this paper, we train a machine learning algorithm to systemically evaluate tectonic, geomechanical, and hydrological proxies suspected to control induced seismicity. Feature importance suggests that proximity to basement, in situ stress, proximity to fossil reef margins, lithium concentration, and rate of natural seismicity are among the strongest model predictors. Our derived seismogenic potential map faithfully reproduces the current distribution of induced seismicity and is suggestive of other regions which may be prone to induced earthquakes. The refinement of induced seismicity geological susceptibility may become an important technique to identify significant underlying geological features and address induced seismic hazard forecasting issues. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine if contrast-enhanced computed tomography (CT) accurately reflected vascular luminal invasion by adrenal masses in dogs. Medical records of 15 dogs with 17 adrenal masses that underwent preoperative CT imaging were reviewed. Presence or absence of vascular invasion was confirmed by surgery or necropsy/histology. Vascular invasion was identified correctly using contrast-enhanced CT in 11/12 dogs. The sensitivity and specificity of contrast-enhanced CT for vascular invasion compared with surgery or necropsy was 92% and 100%, respectively. The positive predictive value and negative predictive value of contrast-enhanced CT was 100% and 90%, respectively. The accuracy was 95%. In one dog, invasion of the phrenicoabdominal vein was not identified on CT images. Six of eight masses with vascular invasion where a histologic diagnosis was obtained were malignant. Four of four pheochromocytomas invaded adjacent vasculature. Contrast-enhanced CT provided accurate preoperative assessment of adrenal masses. Vascular invasion by adrenal masses in this study occurred by way of the lumen of the phrenicoabdominal vein with subsequent intraluminal extension into other veins, rather than by erosion through vessel walls. [ABSTRACT FROM AUTHOR]

The purpose of this study was to describe the clinical, radiographic, and computed tomographic findings in dogs and cats with migrating intrathoracic grass awns. Thirty-five dogs and five cats with visual confirmation of a grass awn following surgery, endoscopy or necropsy, and histology were assessed. The medical records and all diagnostic imaging studies were reviewed retrospectively. Labrador Retrievers or English Pointers <5 years of age, with a history of coughing and hyperthermia, were the most common presentations. Seventeen animals had an inflammatory leukogram of which 14 had a left shift or toxic neutrophils. Radiographs were performed in 38 animals and computed tomography (CT) in 14. Thoracic radiographs were characterized by focal pulmonary interstitial to alveolar opacities ( n=26) that occurred most commonly in the caudal ( n=19) or accessory lobes ( n=8). Additional findings included pneumothorax ( n=9), pleural effusion ( n=8), and pleural thickening ( n=7). Pulmonary opacities identified on radiographs correlated to areas of pneumonia and foreign body location. CT findings included focal interstitial to alveolar pulmonary opacities ( n=12) most commonly in the right caudal lung lobe ( n=9), pleural thickening ( n=11), mildly enlarged intrathoracic lymph nodes ( n=10), soft tissue tracking ( n=7) with enhancing margins ( n=4), pneumothorax ( n=6), pleural effusion ( n=4), and foreign body visualization ( n=4). Histologic diagnoses included pulmonary and mediastinal granulomas or abscesses, bronchopneumonia, and pleuritis. Migrating intrathoracic grass awns should be considered as a differential diagnosis in coughing, febrile animals with focal interstitial to alveolar pulmonary opacities, pleural effusion, pleural thickening, and/or pneumothorax on radiographs or CT. [ABSTRACT FROM AUTHOR]

The purpose of this study was to describe the clinical and radiographic findings in dogs with bone lesions secondary to histiocytic sarcoma. Nineteen dogs with radiographically identified bone lesions that were histologically diagnosed as histiocytic sarcoma were assessed. The medical records, all available radiographs and histologic sections were reviewed retrospectively. Dogs were subcategorized into localized or disseminated histiocytic sarcoma groups. Golden Retrievers or Rottweilers greater than 5 years of age, with a history of lameness or neurologic deficits localized to the spinal cord was the most common presentation. Fifteen of 19 dogs had a radiographically detectable soft tissue mass associated with bone destruction. The bone lesions had aggressive characteristics and the sites of involvement included periarticular bones ( n=11), vertebrae ( n=6), proximal humerus ( n=5), and rib ( n=2). Fifteen of 19 dogs had disseminated histiocytic sarcoma, and four had localized histiocytic sarcoma. All Rottweilers had disseminated histiocytic sarcoma. Histiocytic sarcoma should be considered as a differential diagnosis for aggressive periarticular, vertebral, or proximal humeral bone lesions identified on radiographs. The index of suspicion should be increased in greater than 5-year-old Golden Retrievers and Rottweilers when a soft tissue mass is associated with the bone lesion on radiographs or myelography. Bone involvement with histiocytic sarcoma, and the Rottweiler breed, was associated with the disseminated form of the disease. [ABSTRACT FROM AUTHOR]

The medical records and magnetic resonance (MR) images of dogs with an acquired trigeminal nerve disorder were reviewed retrospectively. Trigeminal nerve dysfunction was present in six dogs with histologic confirmation of etiology. A histopathologic diagnosis of neuritis ( n=2) or nerve sheath tumor ( n=4) was made. Dogs with trigeminal neuritis had diffuse enlargement of the nerve without a mass lesion. These nerves were isointense to brain parenchyma on T1-weighted (T1W) precontrast images and proton-density-weighted (PDW) images and either isointense or hyperintense on T2-weighted (T2W) images. Dogs with a nerve sheath tumor had a solitary or lobulated mass with displacement of adjacent neuropil. Nerve sheath tumors were isointense to the brain parenchyma on T1W, T2W, and PDW images. All trigeminal nerve lesions enhanced following contrast medium administration. Atrophy of the temporalis and masseter muscles, with a characteristic increase in signal intensity on T1W images, were present in all dogs. [ABSTRACT FROM AUTHOR]