Periodic and Static Strain Investigations with Borehole Strainmeters and GPS

I describe four investigations of crustal deformation at spatial scales of cm to hundreds of km, and temporal scales of minutes to decades. With suitable geometry, strainmeters and creepmeters can be used in combination to quantify the propagation direction, velocity, amplitude and location of aseismic slip on a fault. I quantify creep events from a generalized form of the wave equation in terms of three variables, a decay function (&omega;), a propagation velocity, vp and a slip amplitude. In the Yellowstone caldera strainmeters monitor loading arising from a seiche on Lake Yellowstone. To explain the high Q factor (i.e. the remarkable persistence) of the seiche I invoke a positive feed-back process whereby hydrothermal vents in the floor of the lake interact with bottom pressure fluctuations associated with lake level oscillations. This is believed to be the first observation of a thermally driven seiche. GPS data revealed that limited afterslip occurred following the 2015 Mw=7.8 Gorkha earthquake, despite the associated observation that subsurface strain exceeded 10E-5 near the southern margins of rupture. In a published article we hypothesize that blind thrust faults similar to the Gorkha earthquake transfer latent strain to up-dip regions of shallow thrust faults, and that this strain is exploited as additional slip in future earthquakes. Finally, I use GPS data from 151 sites in Colombia, Venezuela and Panama to identify the rate of loading and probable location of a potential future 8 8&lt;Mw&lt;8.3 tsunamigenic earthquake in NW Colombia.</p

Increased Caribbean seismicity and volcanism during minima in Earth\u27s rotation rate: Search for a physical mechanism and a 2030 forecast

Three quarters of all Mw ≥ 6.6 earthquakes and volcanic eruptions surrounding the Caribbean plate occur preferentially during periods of decadal minima in Earth’s angular spin velocity. This correlation is revealed most clearly as a 4–6 years phase lag following the first derivative of the length of the day (LOD), Earth’s angular deceleration. We show that local strains and displacements resulting from oblateness changes, or plate boundary stresses associated with changes in tropical rotation rates are orders of magnitude lower than those typically associated with earthquake or volcano triggering. Notwithstanding the absence of a satisfactory causal physical mechanism, the relationship permits decadal trends in Caribbean tectonic hazards to be anticipated many years before their occurrence. The next period of increased tectonic activity in the Caribbean, corresponding to a probable slowing in Earth’s spin rate, will occur in the decade starting on or about 2030

Characterizing High Rate GNSS Velocity Noise for Synthesizing a GNSS Strong Motion Learning Catalog

Data-driven approaches to identify geophysical signals have proven beneficial in high dimensional environments where model-driven methods fall short. GNSS offers a source of unsaturated ground motion observations that are the data currency of ground motion forecasting and rapid seismic hazard assessment and alerting. However, these GNSS-sourced signals are superposed onto hardware-, location- and time-dependent noise signatures influenced by the Earth’s atmosphere, low-cost or spaceborne oscillators, and complex radio frequency environments. Eschewing heuristic or physics based models for a data-driven approach in this context is a step forward in autonomous signal discrimination. However, the performance of a data-driven approach depends upon substantial representative samples with accurate classifications, and more complex algorithm architectures for deeper scientific insights compound this need. The existing catalogs of high-rate (≥1Hz) GNSS ground motions are relatively limited. In this work, we model and evaluate the probabilistic noise of GNSS velocity measurements over a hemispheric network. We generate stochastic noise time series to augment transferred low-noise strong motion signals from within 70 kilometers of strong events (≥ MW 5.0) from an existing inertial catalog. We leverage known signal and noise information to assess feature extraction strategies and quantify augmentation benefits. We find a classifier model trained on this expanded pseudo-synthetic catalog improves generalization compared to a model trained solely on a real-GNSS velocity catalog, and offers a framework for future enhanced data driven approaches

An Open Label, Randomized, Multicenter Study of Elafibranor in Children With Nonalcoholic Steatohepatitis

ObjectivesNonalcoholic fatty liver disease is the most common chronic liver disease in children. Elafibranor, a dual peroxisome proliferator-activated receptor α/δ agonist, has been proposed as a treatment for nonalcoholic steatohepatitis (NASH). The aims were to (1) describe pharmacokinetics (PK), safety, and tolerability of oral elafibranor at 2 doses (80 and 120 mg) in children 8-17 years and (2) assess changes in aminotransferases.MethodsChildren with NASH were randomized to open-label elafibranor 80 mg or 120 mg daily for 12 weeks. The intent-to-treat analysis included all participants who received at least 1 dose. Standard descriptive statistics and PK analyses were performed.ResultsTen males [mean 15.1 years, standard deviation (SD) 2.2] with NASH were randomized to 80 mg (n = 5) or 120 mg (n = 5). Baseline mean alanine aminotransferase (ALT) was 82 U/L (SD 13) and 87 U/L (SD 20) for 80 mg and 120 mg groups, respectively. Elafibranor was rapidly absorbed and well tolerated. Elafibranor plasma exposure increased between the 80 mg and 120 mg dose with a 1.9- and 1.3-fold increase in median Cmax and AUC 0-24 , respectively. End of treatment mean ALT was 52 U/L (SD 20) for the 120 mg group, with a relative mean ALT change from baseline of -37.4% (SD 23.8%) at 12 weeks.ConclusionsOnce daily dosing of elafibranor was well tolerated in children with NASH. There was a 37.4% relative reduction from mean baseline ALT in the 120 mg group. Decreasing ALT may be associated with improvement in liver histology, thus could be considered a surrogate for histology in early phase trials. These results may support further exploration of elafibranor in children with NASH

Clinically Actionable Hypercholesterolemia and Hypertriglyceridemia in Children with Nonalcoholic Fatty Liver Disease

OBJECTIVE: To determine the percentage of children with nonalcoholic fatty liver disease (NAFLD) in whom intervention for low-density lipoprotein cholesterol or triglycerides was indicated based on National Heart, Lung, and Blood Institute guidelines. STUDY DESIGN: This multicenter, longitudinal cohort study included children with NAFLD enrolled in the National Institute of Diabetes and Digestive and Kidney Diseases Nonalcoholic Steatohepatitis Clinical Research Network. Fasting lipid profiles were obtained at diagnosis. Standardized dietary recommendations were provided. After 1 year, lipid profiles were repeated and interpreted according to National Heart, Lung, and Blood Institute Expert Panel on Integrated Guidelines for Cardiovascular Health and Risk Reduction. Main outcomes were meeting criteria for clinically actionable dyslipidemia at baseline, and either achieving lipid goal at follow-up or meeting criteria for ongoing intervention. RESULTS: There were 585 participants, with a mean age of 12.8 years. The prevalence of children warranting intervention for low-density lipoprotein cholesterol at baseline was 14%. After 1 year of recommended dietary changes, 51% achieved goal low-density lipoprotein cholesterol, 27% qualified for enhanced dietary and lifestyle modifications, and 22% met criteria for pharmacologic intervention. Elevated triglycerides were more prevalent, with 51% meeting criteria for intervention. At 1 year, 25% achieved goal triglycerides with diet and lifestyle changes, 38% met criteria for advanced dietary modifications, and 37% qualified for antihyperlipidemic medications. CONCLUSIONS: More than one-half of children with NAFLD met intervention thresholds for dyslipidemia. Based on the burden of clinically relevant dyslipidemia, lipid screening in children with NAFLD is warranted. Clinicians caring for children with NAFLD should be familiar with lipid management

Constraints on the upper crustal magma reservoir beneath Yellowstone Caldera inferred from lake-seiche induced strain observations

Seiche waves in Yellowstone Lake with a ~78-minute period and heights ~30 km from the lake shore. By contrast, the observed far field strain amplitudes are consistent with the seiche load on a two-layered viscoelastic model representing an elastic upper crust overlying a partially molten body deeper than 3-6 km with Maxwell viscosity less than 1011 Pa s. These strain observations and models provide independent evidence for the presence of partially molten material in the upper crust, consistent with seismic tomography studies that inferred 10%-30% melt fraction in the upper crust. Key Points Strain induced by seiche waves in Yellowstone Lake is observed 30 km away Observed strainfield requires some support from an upper crustal magma reservoir Top of shallowest upper crustal partial melt is at 3 - 6 km depth ©2013. American Geophysical Union. All Rights Reserved

Regional Global Navigation Satellite System Networks for Crustal Deformation Monitoring

Regional networks of Global Navigation Satellite System (GNSS) stations cover seismically and volcanically active areas throughout the United States. Data from these networks have been used to produce high‐precision, three‐component velocity fields covering broad geographic regions as well as position time series that track time‐varying crustal deformation. This information has contributed to assessing interseismic strain accumulation and related seismic hazard, revealed previously unknown occurrences of aseismic fault slip, constrained coseismic slip estimates, and enabled monitoring of volcanic unrest and postseismic deformation. In addition, real‐time GNSS data are now widely available. Such observations proved invaluable for tracking the rapidly evolving eruption of Kīlauea in 2018. Real‐time earthquake source modeling using GNSS data is being incorporated into tsunami warning systems, and a vigorous research effort is focused on quantifying the contribution that real‐time GNSS can make to improve earthquake early warnings as part of the Advanced National Seismic System ShakeAlert system. Real‐time GNSS data can also aid in the tracking of ionospheric disturbances and precipitable water vapor for weather forecasting. Although regional GNSS and seismic networks generally have been established independently, their spatial footprints often overlap, and in some cases the same institution operates both types of networks. Further integration of GNSS and seismic networks would promote joint use of the two data types to better characterize earthquake sources and ground motion as well as offer opportunities for more efficient network operations. Looking ahead, upgrading network stations to leverage new GNSS technology could enable more precise positioning and robust real‐time operations. New computational approaches such as machine learning have the potential to enable full utilization of the large amounts of data generated by continuous GNSS networks. Development of seafloor Global Positioning System‐acoustic networks would provide unique information for fundamental and applied research on subduction zone seismic hazard and, potentially, monitoring