1D Crustal Velocity Model for West-Central Montana

Western Montana is home to a significant amount of continuous, complex seismic activity due to the fact that the region lies within the Intermountain Seismic Belt (ISB). The ISB is a 100 km wide seismic belt that stretches along western Montana, reaching from Yellowstone National Park to northwest Montana, and is responsible for much of the state’s seismic activity. Like many seismically active areas, Western Montana’s earthquakes are best studied through the use of seismographs. Data from these instruments can be used to create crustal velocity models for an area within the seismic network. Velocity models are powerful tools that effectively describe seismic velocity as a function of depth and are used to enhance our understanding of an area’s crustal structure, crustal stress conditions, and earthquake hypocenter locations. In areas that are seismically active, it’s important that these models are updated regularly. However, the velocity model currently in use for Western Montana was last updated in 2003. This is because, even though Montana experiences numerous earthquakes every year, many of these earthquakes are low in magnitude, averaging from M 1.0 - M 3.5. These low magnitude earthquakes do not typically produce enough data to create or update velocity models. Oftentimes, we require much larger events (≥ M 5.0), ideally with a strong aftershock sequence. Historically, for western Montana, such events are intermittent and sometimes decades apart. We will derive a new 1-D crustal velocity model for west-central Montana by analyzing seismic-phase arrivals from the M 5.8, 6 July 2017 earthquake that occurred 11 km southeast of Lincoln, Montana, and hundreds of aftershocks that followed over a three-year period (2017-2020). The 2017 Lincoln earthquake was the largest event above M 5.5 to occur in western Montana in over half a century, the last being the 1959 M 7.3 Hebgen Lake earthquake in southwestern Montana. To determine the velocity model, we manually retrieve continuous seismic data recorded by broadband stations in the University of Montana Seismic Network, which have been strategically deployed to study the Lincoln aftershock sequence, supplemented by telemetered data from the Montana Regional Seismic Network. To constrain the model, we invert phase arrivals from several hundred well-recorded earthquakes (\u3e20 phase arrivals) using the software program VELEST. The final model will characterize the crustal velocity structure appropriate to an area in western Montana of about 5000 km2. Due to western Montana’s proclivity towards infrequent, high-magnitude earthquakes, the 2017 Lincoln event has provided a prime opportunity to collect quality seismic data that will allow us to create a much-needed crustal velocity model for this seismically active region of Montana. Not only will developing a new, regional crustal velocity model advance earthquake science in Montana, but this will also be the first model derived specifically for the west-central region of the state, as the current velocity model is most appropriate for southwestern Montana. With our model, we will be able to provide the first accurate crustal velocity structure and method to locate hypocenters for the west-central region

Deriving a 1D Seismic Velocity Model for West-Central Montana

In seismically active areas with infrequent large-magnitude earthquakes, high-quality seismic data is critical for determining regional seismic velocity models. Here, we present the first 1-D crustal seismic velocity model for west-central Montana, constrained by seismic phase arrivals from the 2017 M 5.8 earthquake that occurred near Lincoln, Montana, and hundreds of aftershocks that followed over a three-year period (2017-2020). The 2017 M 5.8 Lincoln earthquake is the only event \u3eM 5.5 to occur in western Montana in over half a century, with the previous being the 1959 M 7.3 Hebgen Lake earthquake in southwestern Montana. To derive the seismic velocity model, we analyze continuous seismic data recorded by 11 three-component, broadband stations in the University of Montana Seismic Network (UMSN), which we strategically deployed to record the Lincoln aftershock sequence. We also include seismic data from short-period, vertical-component stations in the Montana Regional Seismic Network (MRSN); three temporary three-component, broadband stations deployed by the U.S Geological Survey (USGS); and three three-component, broadband Advanced National Seismic System (ANSS) stations. We manually pick P-wave arrival times from several hundred well-recorded earthquakes using the AQMS Jiggle software and then invert these data for velocity structure using the program VELEST. To effectively constrain the structure of the deeper crust and upper mantle of western Montana as a whole, we also derive an updated velocity model for western Montana based on a regional scale dataset that also includes TA data from 2006 to 2010. This final model characterizes the velocity structure of the crust and uppermost mantle as a function of depth, appropriate to an area in western Montana of about 40,000 km2 (200 km x 200 km). Both the local and regional models improve the accuracy of hypocenter locations and advance understanding of the region’s crustal structure

Causes of prehospital misinterpretations of ST elevation myocardial infarction

Objectives: To determine the causes of software misinterpretation of ST elevation myocardial infarction (STEMI) compared to clinically identified STEMI to identify opportunities to improve prehospital STEMI identification. Methods: We compared ECGs acquired from July 2011 through June 2012 using the LIFEPAK 15 on adult patients transported by the Los Angeles Fire Department. Cases included patients ≥18 years who received a prehospital ECG. Software interpretation of the ECG (STEMI or not) was compared with data in the regional EMS registry to classify the interpretation as true positive (TP), true negative (TN), false positive (FP), or false negative (FN). For cases where classification was not possible using registry data, 3 blinded cardiologists interpreted the ECG. Each discordance was subsequently reviewed to determine the likely cause of misclassification. The cardiologists independently reviewed a sample of these discordant ECGs and the causes of misclassification were updated in an iterative fashion. Results: Of 44,611 cases, 50% were male (median age 65; inter-quartile range 52–80). Cases were classified as 482 (1.1%) TP, 711 (1.6%) FP, 43371 (97.2%) TN, and 47 (0.11%) FN. Of the 711 classified as FP, 126 (18%) were considered appropriate for, though did not undergo, emergent coronary angiography, because the ECG showed definite (52 cases) or borderline (65 cases) ischemic ST elevation, a STEMI equivalent (5 cases) or ST-elevation due to vasospasm (4 cases). The sensitivity was 92.8% [95% CI 90.6, 94.7%] and the specificity 98.7% [95% CI 98.6, 98.8%]. The leading causes of FP were ECG artifact (20%), early repolarization (16%), probable pericarditis/myocarditis (13%), indeterminate (12%), left ventricular hypertrophy (8%), and right bundle branch block (5%). There were 18 additional reasons for FP interpretation (<4% each). The leading causes of FN were borderline ST-segment elevations less than the algorithm threshold (40%) and tall T waves reducing the ST/T ratio below threshold (15%). There were 11 additional reasons for FN interpretation occurring ≤3 times each. Conclusion: The leading causes of FP automated interpretation of STEMI were ECG artifact and non-ischemic causes of ST-segment elevation. FN were rare and were related to ST-segment elevation or ST/T ratio that did not meet the software algorithm threshold

Prevention and Mitigation of Acute Radiation Syndrome in Mice by Synthetic Lipopeptide Agonists of Toll-Like Receptor 2 (TLR2)

Bacterial lipoproteins (BLP) induce innate immune responses in mammals by activating heterodimeric receptor complexes containing Toll-like receptor 2 (TLR2). TLR2 signaling results in nuclear factor-kappaB (NF-κB)-dependent upregulation of anti-apoptotic factors, anti-oxidants and cytokines, all of which have been implicated in radiation protection. Here we demonstrate that synthetic lipopeptides (sLP) that mimic the structure of naturally occurring mycoplasmal BLP significantly increase mouse survival following lethal total body irradiation (TBI) when administered between 48 hours before and 24 hours after irradiation. The TBI dose ranges against which sLP are effective indicate that sLP primarily impact the hematopoietic (HP) component of acute radiation syndrome. Indeed, sLP treatment accelerated recovery of bone marrow (BM) and spleen cellularity and ameliorated thrombocytopenia of irradiated mice. sLP did not improve survival of irradiated TLR2-knockout mice, confirming that sLP-mediated radioprotection requires TLR2. However, sLP was radioprotective in chimeric mice containing TLR2-null BM on a wild type background, indicating that radioprotection of the HP system by sLP is, at least in part, indirect and initiated in non-BM cells. sLP injection resulted in strong transient induction of multiple cytokines with known roles in hematopoiesis, including granulocyte colony-stimulating factor (G-CSF), keratinocyte chemoattractant (KC) and interleukin-6 (IL-6). sLP-induced cytokines, particularly G-CSF, are likely mediators of the radioprotective/mitigative activity of sLP. This study illustrates the strong potential of LP-based TLR2 agonists for anti-radiation prophylaxis and therapy in defense and medical scenarios

Late Quaternary History of the Beaverhead River Canyon, Southwestern Montana

The Beaverhead River, part of the headwaters of the Missouri River, flows through a 190 m-deep canyon incised across the Blacktail Range of southwestern Montana. Discontinuous, unpaired terraces occur at three ranges in elevation above the modern floodplain: ~11±3 m, ~34±8 m, and ~65±7 m with some terrace remnants above ~75 m. The three terrace levels have gradients similar to that of the modern floodplain. A minimum age of 90 ka (Sangamon Interglaciation) was obtained for a bench of calcareous tufa at 39 m using the U-Th disequilibrium series. Assuming an average incision rate of ~43 cm/1000 years based on the tufa age, then the approximate ages of the ~11 m and ~65 m terrace levels are ~26 ka and ~150 ka, respectively. The \u3e75 m terraces are more than ~180 ka and the age of the canyon is greater than ~460 ka. These estimates ages for terrace levels are consistent with major terrace development during times of Pinedale and Bull Lake glaciation. The Blacktail fault offsets Bull Lake outwash `6.5 m about 29 km southeast of the Beaverhead River Canyon, and the fault scarp can be traced to within ~11 km of the canyon. The displacement rate across the fault is ~5.4 cm/1000 years (if the outwash is equivalent to the youngest Bull Lake glaciation at ~120 ka), which is only 13% of the average canyon-incision rate. Based on the large difference between the incision rate and the fault-displacement rate as well as on the parallelism of terrace levels to the floodplain, uplift and rotation of the Blacktail Range, relative to adjacent basins has not been as significant as normal fluvial processes in terrace development. Landslides may also have been an important factor in segregating terraces within different stretches of the canyon at different times

Low Bone Mass in Ambulatory Spinal Muscular Atrophy: A Proactive Approach for an Often-Overlooked Impairment

Background: Individuals with spinal muscular atrophy (SMA) are at risk for low bone mass (LBM). The objectives of this study were to compare bone mineral density (BMD) in ambulatory SMA and control participants, identify LBM, and evaluate the associations of function and physical activity (PA) with LBM. Methods: Thirty-five children and adults, nineteen SMA and sixteen healthy controls, participated. Dual-energy absorptiometry determined BMD, T-scores, and Z-scores. The six-minute walk test (6MWT) and Timed Up and Go (TUG) assessed function. The International Physical Activity Questionnaire Short Form (IPAQ-SF) evaluated PA. Results: Group comparisons and factors associated with BMD were analyzed. Area under the receiver operating characteristic (ROC) curve (AUC) assessed the ability to identify individuals with LBM. SMA participants had lower BMD (p p = 0.004). Conclusions: Ten SMA and one control had LBM. Z-score was associated with 6MWT (rs = 0.65; p s = −0.61; p s = 0.36, p p = 0.006) and TUG (AUC: 0.85; 95% CI: 0.71–0.98; p = 0.002) identified individuals with LBM. Function, assessed by the 6MWT and TUG, is associated with BMD and shows promise for use in identifying individuals with LBM