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Background Limited studies have systematically reviewed the literature to identify and compare the various database methods and optimal thresholds for measuring medication adherence specific to adolescents and adults with asthma. In the present study, we aim to identify the methods and optimal thresholds for measuring medication adherence in population-based pharmacy databases. Methods We searched PubMed, Embase, International Pharmaceutical Abstracts (IPA), Web of Science, Google Scholar, and grey literature from January 1, 1998, to March 16, 2021. Two independent reviewers screened the studies, extracted the data, and assessed the quality of the studies. A quantitative knowledge synthesis was employed. Results Thirty-eight (38) retrospective cohort studies were eligible. This review identified 20 methods for measuring medication adherence in adolescent and adult asthma administrative health records. Two measures namely the medication possession ratio (MPR) and proportion of days covered (PDC) were commonly reported in 87% of the literature included in this study. From the meta-analysis, asthma patients who achieved adherence threshold of "0.75-1.00" [OR: 0.56, 95% CI: 0.41 to 0.77] and ">0.5" [OR: 0.71, 95% CI: 0.54 to 0.94] were less likely to experience asthma exacerbation. Conclusion Despite their limitations, the PDC and the MPR still remain the most common measures for assessing adherence in asthma pharmacy claim databases. The evidence synthesis showed that an adherence threshold of at least 0.75 is optimal for classifying adherent and non-adherent asthma patients.

β2-agonists provide necessary bronchodilatory action, are recommended by existing clinical practice guidelines and are widely prescribed for patients with these conditions. We examined the risk of all-cause mortality and hospitalization for pneumonia associated with long-or short-acting β2-agonists (LABA or SABA) or ICS (inhaled corticosteroids)/LABA use. In a nested case–control of 185,407 patients, we found no association between β2-agonist use and the risk of pneumonia in patients with asthma, COPD, or asthma-COPD overlap. In contrast, new SABA [HR 1.82 (95% CI 1.04–3.20)] or LABA [HR 2.77 (95% CI 1.22–6.31)] use was associated with an increased risk of all-cause mortality compared to ICS use in COPD patients.

Asthma-COPD overlap (ACO) is a newly identified phenotype of chronic obstructive airway diseases with shared asthma and COPD features. Patients with ACO are poorly defined, and some evidence suggests that they have worse health outcomes and greater disease burden than patients with COPD or asthma. Generally, there is no evidence-based and universal definition for ACO; several consensus documents have provided various descriptions of the phenotype. In addition, the mechanisms underlying the development of ACO are not fully understood. Whether ACO is a distinct clinical entity with its particular discrete genetic determinant different from asthma and COPD alone or an intermediate phenotype with overlapping genetic markers within asthma and COPD spectrum of obstructive airway disease remains unproven. This review summarizes the current knowledge of the genetic risk factors, characteristics, and prognosis of ACO.

This work has been supported by the Marsden Fund grant VUW0813 (Royal Society of New Zealand to C.J.N.W.), a James Cook Fellowship (Royal Society of New Zealand) to C.J.N.W., and the ECLIPSE Programme, funded by the N.Z. Ministry of Business, Innovation and Employment. G.F.C. is supported by a NERC Standard Grant (NE/T000317/1), M.L.M. is supported by an NSF CAREER grant (EAR 2042662) and S.J.B. acknowledges Marsden Fund grant VUW1627.

Immediately following the 18 March 2020 Mww 5.7 Magna, Utah, earthquake, work began on installing a network of three-component, 5 Hz geophones throughout the Salt Lake Valley. After six days, 180 geophones had been sited within 35 km of the epicenter. Each geophone recorded 250 samples per second data onsite for ∼40 days. Here, we integrate the geophone data with data from the permanent regional seismic network operated by the University of Utah Seismograph Stations (UUSS). We use machine learning (ML) methods to create a new catalog of arrival time picks, earthquake locations, and P-wave polarities for 18 March 2020–30 April 2020. We train two deep-learning U-Net models to detect P waves and S waves, assigning arrival times to maximal posterior probabilities, followed by a two-step association process that combines deep learning with a grid-based interferometric approach. Our automated workflow results in 142,000 P picks, 188,000 S picks, and over 5000 earthquake locations. We recovered 95% of the events in the UUSS authoritative catalog and more than doubled the total number of events (5000 vs. 2300). The P and S arrival times generated by our ML models have near-zero biases and standard deviations of 0.05 s and 0.09 s, respectively, relative to corresponding analyst times picked at backbone stations. We also use a deep-learning architecture to automatically determine 70,000 P-wave first motions, which agree with 93% of 5876 hand-picked up or down first motions from both the backbone and nodal stations. Overall, the use of ML led to large increases in the number of arrival times, especially S times, that will be useful for future tomographic studies, as well as the discovery of thousands more earthquakes than exist in the UUSS catalog.

Purpose: Gender differences in the incidence, susceptibility and severity of many obstructive airway diseases (OADs) have been well recognized. However, gender differences in the inhaled pharmacotherapy profile are not well characterized. Methods: We conducted a retrospective cohort study to investigate gender differences in new-users of inhaled corticosteroids (ICS), short-or long-acting beta2-agonist (SABA or LABA), ICS/LABA, short-or long-acting muscarinic antagonist (SAMA or LAMA) among patients with asthma, COPD or asthma-COPD overlap (ACO). We used Clinical Practice Research Datalink to identify OAD patients, 18 years and older, who were new-users (1-year washout period) from 01-January-1998 to 31-July-2018. Multivariable logistic regression was used to examine gender differences in each of the inhaled pharmacotherapies after controlling for potential confounders. Results: A total of 242,079 new-users (asthma: 84.93%; COPD: 10.19%; ACO: 4.88%) of inhaled pharmacotherapies were identified. The multivariable analyses showed that males with COPD were more likely to be a new user of a LABA (odds ratio [OR] 1.29; 95% confidence interval [CI], 1.12– 1.49), LAMA (OR 1.21; 95% CI 1.10– 1.33), SAMA (OR 1.11; 95% CI 1.01– 1.21) and less likely to be a new user of a SABA (OR 0.84; 95% CI, 0.80– 0.89) compared to females. Similar patterns were also observed for patients with ACO; males were more likely to be prescribed with LABA (OR 1.26; 95% CI 1.03– 1.55), LAMA (OR 1.28; 95% CI 1.11– 1.48), SAMA (OR 1.28; 95% CI 1.11– 1.48), and less likely to be a new user of a SABA (OR 0.89; 95% CI, 0.82– 0.96). Also, males with asthma were more likely to be a new-user of ICS/LABA (OR 1.15; 95% CI, 1.08– 1.23) and less likely to start an ICS (OR 0.97; 95% CI, 0.95– 0.99) in comparison with females. Conclusion: Our study showed significant gender differences in new-users of inhaled pharmacotherapies among OAD patients. Adjusting for proxies of disease severity, calendar year, smoking and socioeconomic status did not change the association by gender.

Michael Asamoah-Boaheng,1 Jamie Farrell,1 Kwadwo Osei Bonsu,2 Alwell Oyet,3 William K Midodzi1 1Faculty of Medicine, Memorial University of Newfoundland, St John’s, NL, Canada; 2School of Pharmacy, Memorial University of Newfoundland, St John’s, NL, Canada; 3Department of Mathematics and Statistics, Memorial University of Newfoundland, St John’s, NL, CanadaCorrespondence: William K Midodzi, Faculty of Medicine, Memorial University of Newfoundland, St John’s, NL, Canada, Email william.midodzi@med.mun.caBackground: Poor adherence to prescribed asthma medications and risk of severe asthma exacerbations have been well established. However, the effects of changes in asthma medication compliance levels and subsequent risk of COPD is unknown and yet to be investigated. This study investigated the independent effect of medication adherence (MA) and asthma severity levels on the risk of COPD.Methods: We used four linked administrative health databases from the Population data BC to identify asthma patients aged 18 years and older between January 1, 1998 and December 31, 1999 without diagnosis of COPD. The primary event was time-to-COPD diagnosis during the follow-up period (January 1, 2000 to December 31, 2018). The proportion of days covered (PDC) – was used as a surrogate measure for medication adherence (MA) assessed at optimal-level (≥ 0.80), Intermediate-level (0.50– 0.79), and low-level (< 0.5) of adherence. A propensity adjusted analysis with Marginal Structural Cox (MSC) model was employed to estimate the adjusted hazard ratios (aHR) and 95% confidence intervals (95% CI) for the effect of medication adherence and asthma severity over time.Results: At cohort entry, the sample included 68,211 asthma patients with an overall mean age of 48.2 years. The 18-year incidence of COPD in asthma patients was 9.8 per 1000-persons year. In an inverse weighted propensity adjusted analysis of the MSC model, higher MA levels were significantly associated with decreased risk of COPD as follows: optimal-level (aHR: 0.19, 95% CI: 0.17– 0.24); Intermediate-level (aHR: 0.20, 95% CI: 0.18, 0.23) compared to the low-level adherence group. A significant increase in COPD risk was observed in severe asthma patients with low medication adherence (aHR: 1.72, 95% CI: 1.52– 1.93), independent of other patient factors.Conclusion: Optimal (≥ 0.80) and intermediate adherence (0.5 to 0.79) levels were associated with reduced risk of COPD incidence over time. Interventions aimed at improving adherence to prescribed medications in adult asthma patients should be intensified to reduce their risk of COPD.Keywords: asthma, COPD, medication adherence, severe asthma, propensity analysis

Despite ample evidence underpinning the efficacy of βA nested case-control analysis was conducted using the UK Clinical Practice Research Datalink of patients with asthma, COPD or asthma-COPD overlap with initial treatment of LABA, SABA, ICS/LABA, ICS, long-or short-acting muscarinic antagonist (LAMA or SAMA) between 01 January 1998 and 31 July 2018. The primary outcome was MACE, defined as the first occurrence of stroke, heart failure, myocardial infarction, arrhythmia, or cardiovascular death. Each case was matched with up to 10 controls on age, sex, date of cohort-entry, and duration of follow-up. The risk of MACE associated with βThe cohort included 180,567 new users of βIn conclusion, initiation of LABA, SABA, or ICS/LABA in COPD or SABA in asthma-COPD overlap is associated with increased risk of MACE. No associations were observed among patients with asthma.

Asthma patients may have an increased risk for diagnosis of chronic obstructive pulmonary disease (COPD). However, risk factors accelerating time-to-COPD diagnosis are unclear. This study aims to estimate risk factors associated with the incidence of COPD diagnosis in asthma patients. Canada's Population Data BC (PopData BC) was used to identify asthma patients without prior COPD diagnosis between January 1, 1998, to December 31, 1999. Patients were assessed for time-to-incidence of COPD diagnosis from January 1, 2000, to December 31, 2018. The study estimated the effects of several risk factors in predicting the incidence of COPD in asthma patients during the 18-year follow-up period. Patient factors such as Medication Adherence (MA) were assessed by the proportion of days covered (PDC) and the medication possession ratio (MPR). The log-logistic mixed-effects accelerated failure time model was used to estimate the adjusted

Since 1.25 Ma, three volcanic systems in the western U.S. Cordillera hosted rhyolitic eruptions of ≳300 km3 dense rock equivalent creating the Yellowstone (0.63 Ma), Long Valley (0.76 Ma), and Valles (1.25 Ma) calderas. Their similar time scales since caldera-forming eruptions and rich histories of seismic research motivate a review of seismic constraints on the modern magma reservoirs beneath these calderas from the uppermost mantle to the upper crust. Across the Cordillera upper mantle seismic velocities are generally below the continental average and each of the calderas is underlain by exceptionally low velocities consistent with the presence of mantle melt, ≲3%. Concentrated upper mantle low-velocity anomalies are found beneath the eastern Snake River plain southwest of Yellowstone caldera and beneath Long Valley caldera. Valles caldera is located above a broadly distributed low-velocity anomaly associated with the Rio Grande Rift and Jemez volcanic lineament. At lower crustal depths potential magma reservoirs exhibit weaker seismic velocity anomalies and greater variability among the results of different tomographic inversion methods compared to shallower depths. At middle-to-upper crustal depths, ~5–15 km, seismic tomography provides evidence of magmatic reservoirs beneath all three calderas, and scattered wave imaging supports sharp upper, lateral, and/or lower boundaries of each inferred magma reservoir. Estimates of average melt fractions in these reservoirs vary from ~9–23% based on recent tomography, with localized melt fraction estimates as high as ~30–60% based on sharp interfaces detected by scattering and ray bending analyses. The wide range of inferred melt fractions likely results from contrasting sensitivities of different seismic imaging methods combined with spatially heterogeneous melt fractions and uncertainties in mapping seismic velocities to silicate melt fractions. Seismic radial anisotropy beneath Yellowstone and Long Valley calderas indicates that middle-to-upper crustal reservoirs are organized as sill complexes with relatively crystal-poor and crystal-rich layers, suggesting magma storage in many weakly connected volumes. Future estimates of (an)isotropic seismic velocities and melt fractions across 3D reservoirs may be improved through expanded applications of full waveform tomography to body and surface waves and increasingly dense array studies facilitated by combinations of broadband and rapidly-deployable shorter-period seismographs. Advanced seismic imaging offers potential for improved delineation of magma reservoir boundaries and constraints on intra-reservoir structures such as sill complexes that provide insight into magma reservoir mechanics and compositional heterogeneity.

Asthma is a prevalent disease that affects many Canadians. Persistent asthma can affect quality of life, and has multiple health implications. Maternal age at birth has been associated with many adverse health outcomes in children. Conflicting study results exist regarding maternal age at birth and childhood asthma. The association between maternal age at birth and persistent asthma in children is still unknown.To investigate the relationship between maternal age at birth and persistent asthma in children at ten years of age.This is a prospective cohort study including all children aged 0-2 years who took part in the first cycle of the National Longitudinal Survey of Children and Youths (NLSCY) and were followed every two years until eight to ten years of age in Cycle 5. An interaction term between maternal age at birth and maternal asthma history was introduced in a multivariate model to examine modification effects of maternal asthma history on the association.Multivariate logistic regression demonstrated that older maternal age at birth was significantly associated with an increased risk of childhood persistent asthma in mothers with a history of asthma (OR = 1.20, 95% CI: 1.04-1.40,Maternal history of asthma has an impact on the association between maternal age at birth and childhood persistent asthma in children by age ten. The finding may help explain the inconsistent results in the literature regarding the risk of asthma associated with maternal age at birth.

Objective: Sex differences in incidence, susceptibility and severity of many chronic respiratory diseases have been long recognized. Asthma-COPD Overlap (ACO) is newly recognized disease with its m...

Steamboat Geyser in Yellowstone National Park is the tallest active geyser on Earth and is believed to have hydrologic connection to Cistern Spring, a hydrothermal pool ~100 m southwest from the ge...

The plumbing architecture of a hydrothermal feature (e.g., geyser and spring) exerts direct control over its eruption and recharge dynamics. During an active geyser’s recharge, in response to the evolution of temperature and hydrostatic pressure within the plumbing, this two-phase-flow system experiences intensive steam bubble nucleation and collapse throughout the eruption cycle. Such steam-liquid phase transitions generate seismic signals observed as hydrothermal tremor, thus the spatiotemporal pattern of its origin can depict the plumbing architecture and illuminate how the geyser operates internally. Steamboat, the tallest active geyser on Earth, is thought to have a complex architecture and dynamics owing to the hydrologic interaction with the nearby Cistern Spring, ~100 m SW of Steamboat. To study the system, in 2019 we deployed a dense array across the Steamboat-Cistern area with an aperture of ~250 m. The array was composed of 50 three-component geophones and had a spacing of 15–35 m. During the deployment, 6 eruption cycles with intervals ranging from 3 to 8 days were recorded. We observe distinct 1–5 Hz tremor emitted from Steamboat and Cistern, which are persistent and show no isolated events and discernable arrivals. To simultaneously locate the tremor from both features, we perform multicomponent cross-correlation to isolate and enhance the coherent signals of interest with each station as the virtual source. We apply the same normalization to the 3-component data so that the particle motion excited by each virtual source is retained. We observe prevalent seismic P waves at receivers near the source, with complex wavefield transition and interference at distant receivers. Using the P wave linearity, we back project the polarized directions to constrain the 3D source location. The results provide the first 4D view of the tremor throughout the eruption cycles with hourly resolution. The 4D view reveals the conduit beneath Steamboat is vertical and extends down to ~120 m depth and the plumbing of Cistern includes a shallow vertical conduit connecting with a deep, large, and laterally offset reservoir ~60 m southeast of the surface pool. No direct connection between Steamboat and Cistern plumbing structures is found above ~120 m. The temporal variation of the tremor combined with in situ temperature and water depth measurements of Cistern, do reveal the interaction between Steamboat and Cistern throughout the eruption/recharge cycles. The observed delayed responses of Cistern in reaction to Steamboat eruptions and recharge suggest the two plumbing structures might be connected through a fractured/porous medium instead of a direct open channel, consistent with our inferred plumbing structure.

Background: The use of mobile health (mHealth) interventions has the potential to enhance chronic obstructive pulmonary disease (COPD) treatment outcomes. Further research is needed to determine which mHealth features are required to potentially enhance COPD self-management. Aim: The aim of this study was to explore the potential features of an mHealth intervention for COPD management with healthcare providers (HCPs) and patients with COPD. It could inform the development and successful implementation of mHealth interventions for COPD management. Methods: This was a qualitative study. We conducted semi-structured individual interviews with HCPs, including nurses, pharmacists and physicians who work directly with patients with COPD. Interviews were also conducted with a diverse sample of patients with COPD. Interview topics included demographics, mHealth usage, the potential use of medical devices and recommendations for features that would enhance an mHealth intervention for COPD management. Results: A total of 40 people, including nurses, physicians and pharmacists, participated. The main recommendations for the proposed mHealth intervention were categorised into two categories: patient interface and HCP interface. The prevalent features suggested for the patient interface include educating patients, collecting baseline data, collecting subjective data, collecting objective data via compatible medical devices, providing a digital action plan, allowing patients to track their progress, enabling family members to access the mHealth intervention, tailoring the features based on the patient’s unique needs, reminding patients about critical management tasks and rewarding patients for their positive behaviours. The most common features of the HCP interface include allowing HCPs to track their patients’ progress, allowing HCPs to communicate with their patients, educating HCPs and rewarding HCPs. Conclusion: This study identifies important potential features so that the most effective, efficient and feasible mHealth intervention can be developed to improve the management of COPD. The reviews of this paper are available via the supplemental material section.

The 18 March 2020 M 5.7 Magna earthquake near Salt Lake City, Utah, offers a rare glimpse into the subsurface geometry of the Wasatch fault system—one of the world’s longest active norm...

Background Whereas most studies have reported prior history/diagnosis of asthma as an independent risk factor for chronic obstructive pulmonary disease (COPD) development in later life, no systematic review and meta-analysis has been conducted to synthesize these observational studies. The aim of this review is to investigate associations between prior history of asthma and later development of COPD. Methods We conducted a comprehensive search in PubMed, CINAHL and EMBASE for studies related to prior history of asthma and COPD diagnosis. Articles were screened for relevance by two independent reviewers. Methodological quality was independently assessed and data extracted for qualitative and quantitative review. We explored heterogeneity and performed a publication bias check. Results From the 1260 articles retrieved, 9 were included in the qualitative review and 7 in the meta-analysis. History of asthma was associated with developing COPD in later life (Inverse Variance Random-effects model, odds ratio: 7.87, 95% confidence interval: 5.40-11.45, p

We investigated upper crustal structure with data from a dense seismic array deployed around Mount St. Helens for two weeks in the summer of 2014. Inter-station cross-correlations of ambient seismic noise data from the array were obtained and clear fundamental mode Rayleigh waves were observed between 2.5 and 5 s periods. In addition, higher-mode signals were observed around 2 s period. Frequency-time analysis was applied to measure fundamental mode Rayleigh wave phase velocities, which were used to invert for 2-D phase velocity maps. An azimuth-dependent travel time correction was implemented to mitigate potential biases introduced due to an inhomogeneous noise source distribution. Reliable phase velocity maps were only obtained between 3 and 4 s periods due to limitations imposed by the array aperture and higher-mode contamination. The phase velocity tomography results, which are sensitive to structure shallower than 6 km depth, reveal a ~10-15% low-velocity anomaly centered beneath the volcanic edifice and peripheral high-velocity anomalies that likely correspond to cooled igneous intrusions. We suggest that the low-velocity anomaly reflects the high porosity mixture of lava and ash deposits near the surface of the edifice, a highly fractured magmatic conduit and hydrothermal system beneath the volcano, and possibly a small contribution from silicate melt.

BACKGROUND Using a mobile health (mHealth) intervention consisting of a smartphone and compatible medical device has the potential to enhance chronic obstructive pulmonary disease (COPD) treatment outcomes while mitigating health care costs. OBJECTIVE This study aims to describe the demographics, use, and access to smartphones of patients with COPD. It also aims to explore and develop an understanding of potential facilitators and barriers that might influence patients using mHealth interventions for COPD management. METHODS This was an explanatory, sequential mixed methods study. Patients who attended respirology clinics completed a questionnaire on technology access and use. We conducted semistructured individual interviews with the patients. Interview topics included the following: demographics, mHealth use, perceptions toward challenges of mHealth adoption, factors facilitating mHealth adoption, and preferences regarding features of mHealth interventions for COPD management. RESULTS A total of 100 adults completed the survey but 22 participants were excluded because they were not diagnosed with COPD. Of these, 10 patients with COPD participated in the interview. The quantitative component revealed that many patients with COPD owned a mobile phone, but only about one-fourth of the participants (18/77, 23%) owned a smartphone. The likelihood of owning a smartphone was not associated with age, sex, marital status, or geographical location, but patients with high educational status were more likely to own a smartphone. The qualitative component found that patients with COPD, in general, had a positive attitude toward mHealth adoption for COPD management, but several facilitators and barriers were identified. The main facilitators of mHealth adoption are possible health benefits for patients, ease of use, educating patients, and credibility. Alternatively, the barriers to adoption are technical issues, lack of awareness, potential limited uptake from older adults, privacy and confidentiality issues, finances, and lack of interest in mHealth CONCLUSIONS It is important to understand the perceptions of patients with COPD regarding the adoption of innovative mHealth interventions for COPD management. This study identifies some potential facilitators and barriers that may inform the successful development and implementation of mHealth interventions for COPD management.

To determine the safety and effectiveness of current pharmacotherapies consisting of long-acting betaA systematic search was conducted using the PubMed, EMBASE, and Web of Science databases up to June 2018.Only studies comparing the safety and effectiveness of LABA and/or ICS in patients with asthma-COPD overlap were included. A meta-analysis was performed to calculate risk ratio (RR) and 95% confidence interval (CI) using Inverse Variance Random-effects model.From a total of 3382 articles retrieved, three randomized controlled trials (RCTs), six cohort studies (CS), one nested case control study fulfilled the inclusion criteria for three independent meta-analyses representing 181,603 participants. Three CS results show LABA was associated with decreased risk of myocardial infarction (combined RR: 0.80, 95% CI 0.74-0.87) versus non-LABA use; ICS/LABA was associated with a lower risk of death or hospitalization (combined RR: 0.82, 95% CI 0.75-0.90) compared to no use. Results from RCTs, no clear difference in lung function decline in FEVAmong patients with asthma-COPD overlap, LABA is associated with decreased risk of myocardial infarction; and the combination therapy of ICS/LABA appears to reduce the risk of death or hospitalization. More studies of quality data and larger number of patients are needed.PROSPERO (CRD42018090863).

The Upper Geyser Basin in Yellowstone National Park contains one of the highest concentrations of hydrothermal features on Earth including the iconic Old Faithful geyser. Although this system has been the focus of many geological, geochemical, and geophysical studies for decades, the shallow (

The intense unrest of the Yellowstone volcanic plateau is manifested through diffuse seismic activity, earthquake swarms, and episodes of complex surficial deformation that have been related to magmatic fluid transfer in the upper crust over the past several decades. While past studies have focused on modeling contemporary geophysical data, there has not been a fully-integrated evaluation of seismicity, fault kinematics, and stress field. Here we analyze a catalog of 10,201 relocated earthquakes recorded between 2010 and 2016 and determine 224 well-constrained double-couple focal mechanisms. The majority of the focal mechanisms (65%) are associated with the 2010 Madison Plateau seismic swarm. The focal mechanisms are predominantly strike-slip with subordinate normal faulting mechanisms. Possible causes of this predominance and of the concurrence of both kinematics are here discussed, in order to unravel the influence of magmatic processes such as past sill intrusions. The earthquake catalog has been analyzed in terms of location, time, and kinematics according to the phases of surficial deformation documented by GPS data in order to identify systematic patterns of deformation and has been compared to the 1988–2009 seismicity. The continuous downwarping of the overburden from 2010 to 2016 was accomodated by structural adjustment of the shallow crust through strike-slip motions on a multitude of scattered small fault planes. Furthermore, the predominance of strike-slip faulting during seismic swarms occurs when the fluid overpressure induces horizontal propagation of vertical fractures with strike-slip motions, followed by horizontal fluid flow.

The Yellowstone volcanic field has experienced three of Earth's most explosive volcanic eruptions in the last 2.1 Ma. The most recent eruption occurred 0.64 Ma forming the 60 km long Yellowstone caldera. We have compiled earthquake data from the Yellowstone Seismic Network from 1984 to 2011 and tomographically imaged the three-dimensional P wave velocity (Vp) structure of the Yellowstone volcanic system. The resulting model reveals a large, low Vp body, interpreted to be the crustal magma reservoir that has fueled Yellowstone's youthful volcanism. Our imaged magma body is 90 km long, 5–17 km deep, and 2.5 times larger than previously imaged. The magma body extends ~15 km NE of the caldera and correlates with the location of the largest negative gravity anomaly, a −80 mGal gravity low. This new seismic image provides important constraints on the dynamics of the Yellowstone magma system and its potential for future volcanic eruptions and earthquakes.

[1] Over the past several decades, the Yellowstone caldera has experienced frequent earthquake swarms and repeated cycles of uplift and subsidence, reflecting dynamic volcanic and tectonic processes. Here we examine the detailed spatial-temporal evolution of the 2010 Madison Plateau swarm, which occurred near the northwest boundary of the Yellowstone caldera. To fully explore the evolution of the swarm, we integrated procedures for seismic waveform-based earthquake detection with precise double-difference relative relocation. Using cross correlation of continuous seismic data and waveform templates constructed from cataloged events, we detected and precisely located 8710 earthquakes during the 3 week swarm, nearly 4 times the number of events included in the standard catalog. This high-resolution analysis reveals distinct migration of earthquake activity over the course of the swarm. The swarm initiated abruptly on 17 January 2010 at about 10 km depth and expanded dramatically outward (both shallower and deeper) over time, primarily along a NNW striking, ~55° ENE dipping structure. To explain these characteristics, we hypothesize that the swarm was triggered by the rupture of a zone of confined high-pressure aqueous fluids into a preexisting crustal fault system, prompting release of accumulated stress. The high-pressure fluid injection may have been accommodated by hybrid shear and dilatational failure, as is commonly observed in exhumed hydrothermally affected fault zones. This process has likely occurred repeatedly in Yellowstone as aqueous fluids exsolved from magma migrate into the brittle crust, and it may be a key element in the observed cycles of caldera uplift and subsidence.

We evaluated properties of Yellowstone earthquake swarms employing waveform multiplet analysis. Thirty-seven percent of the earthquakes in the Yellowstone caldera occur in multiplets and generally intensify in areas undergoing crustal subsidence. Outside the caldera, in the Hedgen Lake tectonic area, the clustering rate is higher, up to 75%. The Yellowstone seismicity follows a succession of two phases of earthquake sequence. The first phase is defined between swarms. It is characterized by a decay of clustering rate and by foreshock–aftershock sequences. The second phase is confined to swarms and is characterized by an increase in clustering rate, and dominant aftershock sequences. This phase reflects tectonic swarms that occur on short segments of optimally oriented faults. For example, the largest recorded swarm in Yellowstone occurred in autumn 1985 on the northwest side of the Yellowstone Plateau which was initiated as a tectonic source sequence. Fitting experimental dependence of fluid injection with intrusion migration suggests that the 1985 swarm involved, after 10 days, hydrothermal fluids flowing outward from the caldera. The 2008–2009 Yellowstone Lake swarm exhibited a high migration rate of 1 km/day, a decrease in clustering rate without a main-shock, and appears to be associated with magma injection of 1 to 5 m 3 /s in a succession of migrating magma fronts that incrementally solidify and fracture at its brittle edges. The 2010 Madison Plateau earthquake swarm on the west side of the caldera initiated as a tectonic sequence but the expansion of the swarm front was associated with hydrothermal fluid migration.

The Yellowstone volcanic field, Yellowstone National Park, is one of the most seismically active areas of the western U.S., experiencing the deadly 1959 M 7.5 Hebgen Lake, MT, earthquake adjacent to the 0.64-Ma caldera, as well as more than 30,000 earthquakes from 1973 to 2007. This well-recorded seismic activity offers the opportunity to study the temporal and spatial occurrence of earthquakes and extensive earthquake swarms and how they relate to active volcanic and tectonic processes. We characterize the distribution of earthquakes by analyzing the rate of occurrence characterized by the b -value. To accurately determine b -values, the earthquake catalog was filtered to identify statistically time- and spatially-dependent related events, defined as swarms, from independent single main and aftershocks. An algorithm was employed that identified 69 swarms for 1984–2006 based on inter-event times and spatial clustering. The swarms varied in duration from 1 to 46 days with the number of events varying from 30 to 722 with magnitudes of − 1.2 to 4.8. All of the swarm events as well as the 597 events triggered by the 2002 Denali fault, AK, earthquake were removed from the catalog for analysis. The catalog data were then filtered for a magnitude of completeness ( M COMP ) of 1.5 and the b -value distribution for the Yellowstone region was determined with the de-swarmed data. b -values ranged from 0.6 ± 0.1 to 1.5 ± 0.05 with the highest values associated with the youthful 150,000-year old Mallard Lake resurgent dome. These variations are interpreted to be related to variations in stresses accompanying the migration of magmatic and hydrothermal fluids. An area of high b -values (up to 1.3 ± 0.1) associated with the Hebgen Lake fault zone west of the Yellowstone caldera could be related to the transport of magmatic fluids out of the Yellowstone volcanic system or could be indicative of a relative low stress regime resulting from the stress release by the Hebgen Lake earthquake. An area of low b -values (0.6 ± 0.1) south of the Yellowstone caldera is interpreted as evidence of a relatively higher stress regime associated with an area of dominantly extensional stress. This seismicity was associated with a nearly 90° change in the principal stress axes direction to northeast-southwest, compared to east-west within the Yellowstone caldera, and may be influenced by buoyancy loading by the Yellowstone hotspot.

Earthquakes of the Teton–Yellowstone region represent a high level of seismicity in the Intermountain west (U.S.A.) that is associated with intraplate extension associated with the Yellowstone hotspot including the nearby Teton and Hebgen Lake faults. The seismicity and the occurrence of high slip-rate late Quaternary faults in this region leads to a high level of seismic hazard that was evaluated using new earthquake catalogues determined from three-dimensional (3-D) seismic velocity models, followed by the estimation of the probabilistic seismic hazard incorporating fault slip and background earthquake occurrence rates. The 3-D P -wave velocity structure of the Teton region was determined using local earthquake data from the Jackson Lake seismic network that operated from 1986–2002. An earthquake catalog was then developed for 1986–2002 for the Teton region using relocated hypocenters. The resulting data revealed a seismically quiescent Teton fault, at M L , local magnitude > 3, with diffuse seismicity in the southern Jackson Hole Valley area but notable seismicity eastward into the Gros Ventre Range. Relocated Yellowstone earthquakes determined by the same methods highlight a dominant E–W zone of seismicity that extends from the aftershock area of the 1959 (M S surface wave magnitude) 7.5 Hebgen Lake, Montana, earthquake along the north side of the 0.64 Ma Yellowstone caldera. Earthquakes are less frequent and shallow beneath the Yellowstone caldera and notably occur along northward trending zones of activity sub-parallel to the post-caldera volcanic vents. Stress-field orientations derived from inversion of focal mechanism data reveal dominant E–W extension across the Teton fault with a NE–SW extension along the northern Teton fault area and southern Yellowstone. The minimum stress axes directions then rotate to E–W extension across the Yellowstone caldera to N–S extension northwest of the caldera and along the Hebgen Lake fault zone. The combination of accurate hypocenters, unified magnitudes, and seismotectonic analysis helped refine the characterization of the background seismicity that was used as input into a probabilistic seismic hazards analysis. Our results reveals the highest seismic hazard is associated with the Teton fault because of its high slip-rate of approximately 1.3 mm/yr compared to the highest rate of 1.4 mm/yr in southern Yellowstone on the Mt. Sheridan fault. This study demonstrates that the Teton–Yellowstone area is among the regions highest seismic hazard in the western U.S.

The Yellowstone caldera began a rapid episode of ground uplift in mid-2004, revealed by Global Positioning System and interferometric synthetic aperture radar measurements, at rates up to 7 centimeters per year, which is over three times faster than previously observed inflation rates. Source modeling of the deformation data suggests an expanding volcanic sill of ∼1200 square kilometers at a 10-kilometer depth beneath the caldera, coincident with the top of a seismically imaged crustal magma chamber. The modeled rate of source volume increase is 0.1 cubic kilometer per year, similar to the amount of magma intrusion required to supply the observed high heat flow of the caldera. This evidence suggests magma recharge as the main mechanism for the accelerated uplift, although pressurization of magmatic fluids cannot be ruled out.

The M w 7.9 earthquake that struck central Alaska on 3 November 2002 was preceded 11 days earlier by an Mw 6.7 strike-slip foreshock on 23 October 2002. Both events were predominantly strike-slip and ruptured structures associated with the Denali fault system. Previous studies have shown that the mainshock began with failure on a relatively small northeast-striking reverse fault, before breaking out for 300 km of right-lateral strike-slip rupture. Aftershock patterns suggest that the fore- shock ruptured a region west of the mainshock, which began near the eastern extent of the foreshock sequence and proceeded east-southeast. To constrain and to quantify source duration and directivity effects, we examine surface-wave displacement seis- mograms and use an empirical Green's function (EGF) to isolate and explore main- shock rupture kinematics. Our particular interest lies in large-amplitude focussing caused by directivity. We observe Love and Rayleigh wave amplification of two orders of magnitude in the period range from 10 to 33 sec. These remarkable directivity-enhanced surface waves triggered small earthquakes more than 3000 km from the mainshock rupture.

The Yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world. An understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk. Using a joint local and teleseismic earthquake P-wave seismic inversion, we revealed a basaltic lower-crustal magma body that provides a magmatic link between the Yellowstone mantle plume and the previously imaged upper-crustal magma reservoir. This lower-crustal magma body has a volume of 46,000 cubic kilometers, ~4.5 times that of the upper-crustal magma reservoir, and contains a melt fraction of ~2%. These estimates are critical to understanding the evolution of bimodal basaltic-rhyolitic volcanism, explaining the magnitude of CO2 discharge, and constraining dynamic models of the magmatic system for volcanic hazard assessment.

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[1] Geodetic measurements of Yellowstone ground deformation from 2006 to June 2010 reveal deceleration of the recent uplift of the Yellowstone caldera following an unprecedented period of uplift that began in 2004. In 2006–2008 uplift rates decreased from 7 to 5 cm/yr and 4 to 2 cm/yr in the northern and southwest caldera, respectively, and in 2009 rates further reduced to 2 cm/yr and 0.5 cm/yr in the same areas. Elastic-dislocation modeling of the deformation data robustly indicates an expanding sill at ∼7–10 km depth near the top of a seismically imaged, crystallizing magma reservoir, with a 60% decrease in the volumetric expansion rate between 2006 and 2009. Reduction of hydrothermal-volcanic recharge from beneath the northeast caldera and seismic moment release of the 2008 and 2010 large earthquake swarms are plausible mechanisms for decelerating the caldera uplift and may have influenced the change in recent caldera motion from uplift to subsidence.

[1] Yellowstone National Park experienced an unusual earthquake swarm in December–January, 2008–2009 that included rapid northward migration of the activity at 1 km per day and shallowing of the maximum focal depths from 12 to 2 km beneath northern Yellowstone Lake. The swarm consisted of 811 earthquakes, 0.5 < MW < 4.1, aligned on a N–S 12-km-long vertical plane of hypocenters. The largest earthquake of the swarm had a 50% tensile crack-opening source determined by a full waveform inversion that we interpret as a magmatic expansion component. In addition, GPS data revealed E–W crustal extension coincident with the swarm. Modeling of GPS and seismic data is consistent with E–W opening of ∼10 cm on a N–S striking vertical dike. Our interpretation is that the swarm was induced by magmatic fluid migration or propagation of a poroelastic stress pulse along a pre-existing fracture zone.

Integration of geophysical and geological data show that the Yellowstone hotspot resulted from a mantle plume interacting with the overriding North America plate, a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16-17 Ma, 700-km-long Yellowstone-Snake River Plain (YSRP) silicic volcanic system. Accessibility of the YSRP allowed large-scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements. Seismic tomography reveals a crustal magma reservoir of 8% to 15% melt, 6 km to 16 km deep, beneath the Yellowstone caldera. An upper-mantle low-P-wave-velocity body extends vertically from 80 km to 250 km beneath Yellowstone, but the anomalous body tilts 60 °WNW and extends to 660 km depth into the mantle transition zone. We interpret this conduit-shaped low-velocity body as a plume of up to - 3.5% Vp and - 5.5% Vs perturbation that corresponds to a 1-2% partial melt. Models of whole mantle convection reveal eastward upper-mantle flow beneath Yellowstone at relatively high rates of 5 cm/yr that deflects the ascending plume into its west-tilted geometry. A geodynamic model of the Yellowstone plume constrained by Vp and Vs velocities and attenuation parameters suggests low excess temperatures of up to 120 K, corresponding to a maximum 2.5% melt, and a small buoyancy flux of 0.25 Mg/s, i.e., properties of a cool, weak plume. The buoyancy flux is many times smaller than for oceanic plumes, nonetheless, plume buoyancy has produced a ~ 400-km-wide, ~ 500-m-high topographic swell centered on the Yellowstone Plateau. Contemporary deformation derived from GPS measurements reveals SW extension of 2-3 mm/yr across the Yellowstone Plateau, one-fourth of the total Basin-Range opening rate, which we consider to be part of Basin-Range intraplate extension. Locally, decadal episodes of subsidence and uplift, averaging ~ 2 cm/yr, characterize the 80-year Yellowstone caldera monitored history and are modeled as hydrothermal-magmatic sources. Moreover a recent episode, 2004-2009, of accelerated uplift of the Yellowstone caldera at rates up to 7 cm/yr has been modeled as resulting from magmatic recharge of a 10-km-deep sill at the top of the crustal magma reservoir. Regionally, gravitational potential energy of the Yellowstone swell drives the lithosphere southwest and “downhill” from the Yellowstone Plateau 400 km where it coalesces with Basin-Range province-wide westward extension. Based on the geometry and its assumed 660 km depth, we extrapolate the plume source southwest to its original location at 17 Ma and 600 km southwest and 200 km north of the YSRP. Importantly, this location is beneath the southern part of the Columbia Plateau flood basalt field of the same age and implies that the Yellowstone mantle plume may be the common source for both of these large volcanic fields. Our time-progression model suggests that the original plume head rose vertically behind the Juan de Fuca plate, but at ~ 12 Ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler, thicker continental lithosphere, becoming entrained in eastward upper-mantle flow. These results reveal that Yellowstone plume-plate processes have had a profound effect on Late Cenozoic geologic evolution and topography of a large part of the western U.S.